Fig. 1. (a) Dimensions of the casting with runners (unit: mm), (b) a melt flow simulation using Flow-3D software together with Reilly's model[44], predicted that a large amount of bifilms (denoted by the black particles) would be contained in the final casting. (c) A solidification simulation using Pro-cast software showed that no shrinkage defect was contained in the final casting.

AZ91 합금 주물 내 연행 결함에 대한 캐리어 가스의 영향

TianLiabJ.M.T.DaviesaXiangzhenZhuc
aUniversity of Birmingham, Birmingham B15 2TT, United Kingdom
bGrainger and Worrall Ltd, Bridgnorth WV15 5HP, United Kingdom
cBrunel Centre for Advanced Solidification Technology, Brunel University London, Kingston Ln, London, Uxbridge UB8 3PH, United Kingdom

Abstract

An entrainment defect (also known as a double oxide film defect or bifilm) acts a void containing an entrapped gas when submerged into a light-alloy melt, thus reducing the quality and reproducibility of the final castings. Previous publications, carried out with Al-alloy castings, reported that this trapped gas could be subsequently consumed by the reaction with the surrounding melt, thus reducing the void volume and negative effect of entrainment defects. Compared with Al-alloys, the entrapped gas within Mg-alloy might be more efficiently consumed due to the relatively high reactivity of magnesium. However, research into the entrainment defects within Mg alloys has been significantly limited. In the present work, AZ91 alloy castings were produced under different carrier gas atmospheres (i.e., SF6/CO2, SF6/air). The evolution processes of the entrainment defects contained in AZ91 alloy were suggested according to the microstructure inspections and thermodynamic calculations. The defects formed in the different atmospheres have a similar sandwich-like structure, but their oxide films contained different combinations of compounds. The use of carrier gases, which were associated with different entrained-gas consumption rates, affected the reproducibility of AZ91 castings.

연행 결함(이중 산화막 결함 또는 이중막이라고도 함)은 경합금 용융물에 잠길 때 갇힌 가스를 포함하는 공극으로 작용하여 최종 주물의 품질과 재현성을 저하시킵니다. Al-합금 주물을 사용하여 수행된 이전 간행물에서는 이 갇힌 가스가 주변 용융물과의 반응에 의해 후속적으로 소모되어 공극 부피와 연행 결함의 부정적인 영향을 줄일 수 있다고 보고했습니다. Al-합금에 비해 마그네슘의 상대적으로 높은 반응성으로 인해 Mg-합금 내에 포집된 가스가 더 효율적으로 소모될 수 있습니다. 그러나 Mg 합금 내 연행 결함에 대한 연구는 상당히 제한적이었습니다. 현재 작업에서 AZ91 합금 주물은 다양한 캐리어 가스 분위기(즉, SF6/CO2, SF6/공기)에서 생산되었습니다. AZ91 합금에 포함된 연행 결함의 진화 과정은 미세 조직 검사 및 열역학 계산에 따라 제안되었습니다. 서로 다른 분위기에서 형성된 결함은 유사한 샌드위치 구조를 갖지만 산화막에는 서로 다른 화합물 조합이 포함되어 있습니다. 다른 동반 가스 소비율과 관련된 운반 가스의 사용은 AZ91 주물의 재현성에 영향을 미쳤습니다.

Keywords

Magnesium alloy, Casting, Oxide film, Bifilm, Entrainment defect, Reproducibility

1. Introduction

As the lightest structural metal available on Earth, magnesium became one of the most attractive light metals over the last few decades. The magnesium industry has consequently experienced a rapid development in the last 20 years [1,2], indicating a large growth in demand for Mg alloys all over the world. Nowadays, the use of Mg alloys can be found in the fields of automobiles, aerospace, electronics and etc.[3,4]. It has been predicted that the global consumption of Mg metals will further increase in the future, especially in the automotive industry, as the energy efficiency requirement of both traditional and electric vehicles further push manufactures lightweight their design [3,5,6].

The sustained growth in demand for Mg alloys motivated a wide interest in the improvement of the quality and mechanical properties of Mg-alloy castings. During a Mg-alloy casting process, surface turbulence of the melt can lead to the entrapment of a doubled-over surface film containing a small quantity of the surrounding atmosphere, thus forming an entrainment defect (also known as a double oxide film defect or bifilm) [7][8][9][10]. The random size, quantity, orientation, and placement of entrainment defects are widely accepted to be significant factors linked to the variation of casting properties [7]. In addition, Peng et al. [11] found that entrained oxides films in AZ91 alloy melt acted as filters to Al8Mn5 particles, trapping them as they settle. Mackie et al. [12] further suggested that entrained oxide films can act to trawl the intermetallic particles, causing them to cluster and form extremely large defects. The clustering of intermetallic compounds made the entrainment defects more detrimental for the casting properties.

Most of the previous studies regarding entrainment defects were carried out on Al-alloys [7,[13][14][15][16][17][18], and a few potential methods have been suggested for diminishing their negative effect on the quality of Al-alloy castings. Nyahumwa et al.,[16] shows that the void volume within entrainment defects could be reduced by a hot isostatic pressing (HIP) process. Campbell [7] suggested the entrained gas within the defects could be consumed due to reaction with the surrounding melt, which was further verified by Raiszedeh and Griffiths [19].The effect of the entrained gas consumption on the mechanical properties of Al-alloy castings has been investigated by [8,9], suggesting that the consumption of the entrained gas promoted the improvement of the casting reproducibility.

Compared with the investigation concerning the defects within Al-alloys, research into the entrainment defects within Mg-alloys has been significantly limited. The existence of entrainment defects has been demonstrated in Mg-alloy castings [20,21], but their behaviour, evolution, as well as entrained gas consumption are still not clear.

In a Mg-alloy casting process, the melt is usually protected by a cover gas to avoid magnesium ignition. The cavities of sand or investment moulds are accordingly required to be flushed with the cover gas prior to the melt pouring [22]. Therefore, the entrained gas within Mg-alloy castings should contain the cover gas used in the casting process, rather than air only, which may complicate the structure and evolution of the corresponding entrainment defects.

SF6 is a typical cover gas widely used for Mg-alloy casting processes [23][24][25]. Although this cover gas has been restricted to use in European Mg-alloy foundries, a commercial report has pointed out that this cover is still popular in global Mg-alloy industry, especially in the countries which dominated the global Mg-alloy production, such as China, Brazil, India, etc. [26]. In addition, a survey in academic publications also showed that this cover gas was widely used in recent Mg-alloy studies [27]. The protective mechanism of SF6 cover gas (i.e., the reaction between liquid Mg-alloy and SF6 cover gas) has been investigated by several previous researchers, but the formation process of the surface oxide film is still not clearly understood, and even some published results are conflicting with each other. In early 1970s, Fruehling [28] found that the surface film formed under SF6 was MgO mainly with traces of fluorides, and suggested that SF6 was absorbed in the Mg-alloy surface film. Couling [29] further noticed that the absorbed SF6 reacted with the Mg-alloy melt to form MgF2. In last 20 years, different structures of the Mg-alloy surface films have been reported, as detailed below.(1)

Single-layered film. Cashion [30,31] used X-ray Photoelectron Spectroscopy (XPS) and Auger Spectroscopy (AES) to identify the surface film as MgO and MgF2. He also found that composition of the film was constant throughout the thickness and the whole experimental holding time. The film observed by Cashion had a single-layered structure created from a holding time from 10 min to 100 min.(2)

Double-layered film. Aarstad et. al [32] reported a doubled-layered surface oxide film in 2003. They observed several well-distributed MgF2 particles attached to the preliminary MgO film and grew until they covered 25–50% of the total surface area. The inward diffusion of F through the outer MgO film was the driving force for the evolution process. This double-layered structure was also supported by Xiong’s group [25,33] and Shih et al. [34].(3)

Triple-layered film. The triple-layered film and its evolution process were reported in 2002 by Pettersen [35]. Pettersen found that the initial surface film was a MgO phase and then gradually evolved to the stable MgF2 phase by the inward diffusion of F. In the final stage, the film has a triple-layered structure with a thin O-rich interlayer between the thick top and bottom MgF2 layers.(4)

Oxide film consisted of discrete particles. Wang et al [36] stirred the Mg-alloy surface film into the melt under a SF6 cover gas, and then inspect the entrained surface film after the solidification. They found that the entrained surface films were not continues as the protective surface films reported by other researchers but composed of discrete particles. The young oxide film was composed of MgO nano-sized oxide particles, while the old oxide films consist of coarse particles (about 1  µm in average size) on one side that contained fluorides and nitrides.

The oxide films of a Mg-alloy melt surface or an entrained gas are both formed due to the reaction between liquid Mg-alloy and the cover gas, thus the above-mentioned research regarding the Mg-alloy surface film gives valuable insights into the evolution of entrainment defects. The protective mechanism of SF6 cover gas (i.e., formation of a Mg-alloy surface film) therefore indicated a potential complicated evolution process of the corresponding entrainment defects.

However, it should be noted that the formation of a surface film on a Mg-alloy melt is in a different situation to the consumption of an entrained gas that is submerged into the melt. For example, a sufficient amount of cover gas was supported during the surface film formation in the studies previously mentioned, which suppressed the depletion of the cover gas. In contrast, the amount of entrained gas within a Mg-alloy melt is finite, and the entrained gas may become fully depleted. Mirak [37] introduced 3.5%SF6/air bubbles into a pure Mg-alloy melt solidifying in a specially designed permanent mould. It was found that the gas bubbles were entirely consumed, and the corresponding oxide film was a mixture of MgO and MgF2. However, the nucleation sites (such as the MgF2 spots observed by Aarstad [32] and Xiong [25,33]) were not observed. Mirak also speculated that the MgF2 formed prior to MgO in the oxide film based on the composition analysis, which was opposite to the surface film formation process reported in previous literatures (i.e., MgO formed prior to MgF2). Mirak’s work indicated that the oxide-film formation of an entrained gas may be quite different from that of surface films, but he did not reveal the structure and evolution of the oxide films.

In addition, the use of carrier gas in the cover gases also influenced the reaction between the cover gas and the liquid Mg-alloy. SF6/air required a higher content of SF6 than did a SF6/CO2 carrier gas [38], to avoid the ignition of molten magnesium, revealing different gas-consumption rates. Liang et.al [39] suggested that carbon was formed in the surface film when CO2 was used as a carrier gas, which was different from the films formed in SF6/air. An investigation into Mg combustion [40] reported a detection of Mg2C3 in the Mg-alloy sample after burning in CO2, which not only supported Liang’s results, but also indicated a potential formation of Mg carbides in double oxide film defects.

The work reported here is an investigation into the behaviour and evolution of entrainment defects formed in AZ91 Mg-alloy castings, protected by different cover gases (i.e., SF6/air and SF6/CO2). These carrier gases have different protectability for liquid Mg alloy, which may be therefore associated with different consumption rates and evolution processes of the corresponding entrained gases. The effect of the entrained-gas consumption on the reproducibility of AZ91 castings was also studied.

2. Experiment

2.1. Melting and casting

Three kilograms AZ91 alloy was melted in a mild steel crucible at 700 ± 5 °C. The composition of the AZ91 alloy has been shown in Table 1. Prior to heating, all oxide scale on the ingot surface was removed by machining. The cover gases used were 0.5%SF6/air or 0.5%SF6/CO2 (vol.%) at a flow rate of 6 L/min for different castings. The melt was degassed by argon with a flow rate of 0.3 L/min for 15 min [41,42], and then poured into sand moulds. Prior to pouring, the sand mould cavity was flushed with the cover gas for 20 min [22]. The residual melt (around 1 kg) was solidified in the crucible.

Table 1. Composition (wt.%) of the AZ91 alloy used in this study.

AlZnMnSiFeNiMg
9.40.610.150.020.0050.0017Residual

Fig. 1(a) shows the dimensions of the casting with runners. A top-filling system was deliberately used to generate entrainment defects in the final castings. Green and Campbell [7,43] suggested that a top-filling system caused more entrainment events (i.e., bifilms) during a casting process, compared with a bottom-filling system. A melt flow simulation (Flow-3D software) of this mould, using Reilly’s model [44] regarding the entrainment events, also predicted that a large amount of bifilms would be contained in the final casting (denoted by the black particles in Fig. 1b).

Fig. 1. (a) Dimensions of the casting with runners (unit: mm), (b) a melt flow simulation using Flow-3D software together with Reilly's model[44], predicted that a large amount of bifilms (denoted by the black particles) would be contained in the final casting. (c) A solidification simulation using Pro-cast software showed that no shrinkage defect was contained in the final casting.

Shrinkage defects also affect the mechanical properties and reproducibility of castings. Since this study focused on the effect of bifilms on the casting quality, the mould has been deliberately designed to avoid generating shrinkage defects. A solidification simulation using ProCAST software showed that no shrinkage defect would be contained in the final casting, as shown in Fig. 1c. The casting soundness has also been confirmed using a real time X-ray prior to the test bar machining.

The sand moulds were made from resin-bonded silica sand, containing 1wt. % PEPSET 5230 resin and 1wt. % PEPSET 5112 catalyst. The sand also contained 2 wt.% Na2SiF6 to act as an inhibitor [45]. The pouring temperature was 700 ± 5 °C. After the solidification, a section of the runner bars was sent to the Sci-Lab Analytical Ltd for a H-content analysis (LECO analysis), and all the H-content measurements were carried out on the 5th day after the casting process. Each of the castings was machined into 40 test bars for a tensile strength test, using a Zwick 1484 tensile test machine with a clip extensometer. The fracture surfaces of the broken test bars were examined using Scanning Electron Microscope (SEM, Philips JEOL7000) with an accelerating voltage of 5–15 kV. The fractured test bars, residual Mg-alloy solidified in the crucible, and the casting runners were then sectioned, polished and also inspected using the same SEM. The cross-section of the oxide film found on the test-bar fracture surface was exposed by the Focused Ion Beam milling technique (FIB), using a CFEI Quanta 3D FEG FIB-SEM. The oxide film required to be analysed was coated with a platinum layer. Then, a gallium ion beam, accelerated to 30 kV, milled the material substrate surrounding the platinum coated area to expose the cross section of the oxide film. EDS analysis of the oxide film’s cross section was carried out using the FIB equipment at accelerating voltage of 30 kV.

2.2. Oxidation cell

As previously mentioned, several past researchers investigated the protective film formed on a Mg-alloy melt surface [38,39,[46][47][48][49][50][51][52]. During these experiments, the amount of cover gas used was sufficient, thus suppressing the depletion of fluorides in the cover gas. The experiment described in this section used a sealed oxidation cell, which limited the supply of cover gas, to study the evolution of the oxide films of entrainment defects. The cover gas contained in the oxidation cell was regarded as large-size “entrained bubble”.

As shown in Fig. 2, the main body of the oxidation cell was a closed-end mild steel tube which had an inner length of 400 mm, and an inner diameter of 32 mm. A water-cooled copper tube was wrapped around the upper section of the cell. When the tube was heated, the cooling system created a temperature difference between the upper and lower sections, causing the interior gas to convect within the tube. The temperature was monitored by a type-K thermocouple located at the top of the crucible. Nie et al. [53] suggested that the SF6 cover gas would react with the steel wall of the holding furnace when they investigated the surface film of a Mg-alloy melt. To avoid this reaction, the interior surface of the steel oxidation cell (shown in Fig. 2) and the upper half section of the thermocouple were coated with boron nitride (the Mg-alloy was not in contact with boron nitride).

Fig. 2. Schematic of the oxidation cell used to study the evolution of the oxide films of the entrainment defects (unit mm).

During the experiment, a block of solid AZ91 alloy was placed in a magnesia crucible located at the bottom of the oxidation cell. The cell was heated to 100 °C in an electric resistance furnace under a gas flow rate of 1 L/min. The cell was held at this temperature for 20 min, to replace the original trapped atmosphere (i.e. air). Then, the oxidation cell was further heated to 700 °C, melting the AZ91 sample. The gas inlet and exit valves were then closed, creating a sealed environment for oxidation under a limited supply of cover gas. The oxidation cell was then held at 700 ± 10 °C for periods of time from 5 min to 30 min in 5-min intervals. At the end of each holding time, the cell was quenched in water. After cooling to room temperature, the oxidised sample was sectioned, polished, and subsequently examined by SEM.

3. Results

3.1. Structure and composition of the entrainment defects formed in SF6/air

The structure and composition of the entrainment defect formed in the AZ91 castings under a cover gas of 0.5%SF6/air was observed by SEM and EDS. The results indicate that there exist two types of entrainment defects which are sketched in Fig. 3: (1) Type A defect whose oxide film has a traditional single-layered structure and (2) Type B defect, whose oxide film has two layers. The details of these defects were introduced in the following. Here it should be noticed that, as the entrainment defects are also known as biofilms or double oxide film, the oxide films of Type B defect were referred to as “multi-layered oxide film” or “multi-layered structure” in the present work to avoid a confusing description such as “the double-layered oxide film of a double oxide film defect”.

Fig. 3. Schematic of the different types of entrainment defects found in AZ91 castings. (a) Type A defect with a single-layered oxide film and (b) Type B defect with two-layered oxide film.

Fig. 4(a-b) shows a Type A defect having a compact single-layered oxide film with about 0.4 µm thickness. Oxygen, fluorine, magnesium and aluminium were detected in this film (Fig. 4c). It is speculated that oxide film is the mixture of fluoride and oxide of magnesium and aluminium. The detection of fluorine revealed that an entrained cover gas was contained in the formation of this defect. That is to say that the pores shown in Fig. 4(a) were not shrinkage defects or hydrogen porosity, but entrainment defects. The detection of aluminium was different with Xiong and Wang’s previous study [47,48], which showed that no aluminium was contained in their surface film of an AZ91 melt protected by a SF6 cover gas. Sulphur could not be clearly recognized in the element map, but there was a S-peak in the corresponding ESD spectrum.

Fig. 4. (a) A Type A entrainment defect formed in SF6/air and having a single-layered oxide film, (b) the oxide film of this defect, (c) SEM-EDS element maps (using Philips JEOL7000) corresponding to the area highlighted in (b).

Fig. 5(a-b) shows a Type B entrainment defect having a multi-layered oxide film. The compact outer layers of the oxide films were enriched with fluorine and oxygen (Fig. 5c), while their relatively porous inner layers were only enriched with oxygen (i.e., poor in fluorine) and partly grew together, thus forming a sandwich-like structure. Therefore, it is speculated that the outer layer is the mixture of fluoride and oxide, while the inner layer is mainly oxide. Sulphur could only be recognized in the EDX spectrum and could not be clearly identified in the element map, which might be due to the small S-content in the cover gas (i.e., 0.5% volume content of SF6 in the cover gas). In this oxide film, aluminium was contained in the outer layer of this oxide film but could not be clearly detected in the inner layer. Moreover, the distribution of Al seems to be uneven. It can be found that, in the right side of the defect, aluminium exists in the film but its concentration can not be identified to be higher than the matrix. However, there is a small area with much higher aluminium concentration in the left side of the defect. Such an uneven distribution of aluminium was also observed in other defects (shown in the following), and it is the result of the formation of some oxide particles in or under the film.

Fig. 5. (a) A Type B entrainment defect formed in SF6/air and having a multi-layered oxide film, (b) the oxide films of this defect have grown together, (c) SEM-EDS element maps (using Philips JEOL7000) corresponding to the area shown in (b).

Figs. 4 and 5 show cross sectional observations of the entrainment defects formed in the AZ91 alloy sample cast under a cover gas of SF6/air. It is not sufficient to characterize the entrainment defects only by the figures observed from the two-dimensional section. To have a further understanding, the surface of the entrainment defects (i.e. the oxide film) was further studied by observing the fracture surface of the test bars.

Fig. 6(a) shows fracture surfaces of an AZ91 alloy tensile test bar produced in SF6/air. Symmetrical dark regions can be seen on both sides of the fracture surfaces. Fig. 6(b) shows boundaries between the dark and bright regions. The bright region consisted of jagged and broken features, while the surface of the dark region was relatively smooth and flat. In addition, the EDS results (Fig. 6c-d and Table 2) show that fluorine, oxygen, sulphur, and nitrogen were only detected in the dark regions, indicating that the dark regions were surface protective films entrained into the melt. Therefore, it could be suggested that the dark regions were an entrainment defect with consideration of their symmetrical nature. Similar defects on fracture surfaces of Al-alloy castings have been previously reported [7]Nitrides were only found in the oxide films on the test-bar fracture surfaces but never detected in the cross-sectional samples shown in Figs. 4 and 5. An underlying reason is that the nitrides contained in these samples may have hydrolysed during the sample polishing process [54].

Fig. 6. (a) A pair of the fracture surfaces of a AZ91 alloy tensile test bar produced under a cover gas of SF6/air. The dimension of the fracture surface is 5 mm × 6 mm, (b) a section of the boundary between the dark and bright regions shown in (a), (c-d) EDS spectrum of the (c) bright regions and (d) dark regions, (e) schematic of an entrainment defect contained in a test bar.

Table 2. EDS results (wt.%) corresponding to the regions shown in Fig. 6 (cover gas: SF6/air).

Empty CellCOMgFAlZnSN
Dark region in Fig. 6(b)3.481.3279.130.4713.630.570.080.73
Bright region in Fig. 6(b)3.5884.4811.250.68

In conjunction with the cross-sectional observation of the defects shown in Figs. 4 and 5, the structure of an entrainment defect contained in a tensile test bar was sketched as shown in Fig. 6(e). The defect contained an entrained gas enclosed by its oxide film, creating a void section inside the test bar. When the tensile force applied on the defect during the fracture process, the crack was initiated at the void section and propagated along the entrainment defect, since cracks would be propagated along the weakest path [55]. Therefore, when the test bar was finally fractured, the oxide films of entrainment defect appeared on both fracture surfaces of the test bar, as shown in Fig. 6(a).

3.2. Structure and composition of the entrainment defects formed in SF6/CO2

Similar to the entrainment defect formed in SF6/air, the defects formed under a cover gas of 0.5%SF6/CO2 also had two types of oxide films (i.e., single-layered and multi-layered types). Fig. 7(a) shows an example of the entrainment defects containing a multi-layered oxide film. A magnified observation to the defect (Fig. 7b) shows that the inner layers of the oxide films had grown together, presenting a sandwich-like structure, which was similar to the defects formed in an atmosphere of SF6/air (Fig. 5b). An EDS spectrum (Fig. 7c) revealed that the joint area (inner layer) of this sandwich-like structure mainly contained magnesium oxides. Peaks of fluorine, sulphur, and aluminium were recognized in this EDS spectrum, but their amount was relatively small. In contrast, the outer layers of the oxide films were compact and composed of a mixture of fluorides and oxides (Fig. 7d-e).

Fig. 7. (a) An example of entrainment defects formed in SF6/CO2 and having a multi-layered oxide film, (b) magnified observation of the defect, showing the inner layer of the oxide films has grown together, (c) EDS spectrum of the point denoted in (b), (d) outer layer of the oxide film, (e) SEM-EDS element maps (using Philips JEOL7000) corresponding to the area shown in (d).

Fig. 8(a) shows an entrainment defect on the fracture surfaces of an AZ91 alloy tensile test bar, which was produced in an atmosphere of 0.5%SF6/CO2. The corresponding EDS results (Table 3) showed that oxide film contained fluorides and oxides. Sulphur and nitrogen were not detected. Besides, a magnified observation (Fig. 8b) indicated spots on the oxide film surface. The diameter of the spots ranged from hundreds of nanometres to a few micron meters.

Fig. 8. (a) A pair of the fracture surfaces of a AZ91 alloy tensile test bar, produced in an atmosphere of SF6/CO2. The dimension of the fracture surface is 5 mm × 6 mm, (b) surface appearance of the oxide films on the fracture surfaces, showing spots on the film surface.

To further reveal the structure and composition of the oxide film clearly, the cross-section of the oxide film on a test-bar fracture surface was onsite exposed using the FIB technique (Fig. 9). As shown in Fig. 9a, a continuous oxide film was found between the platinum coating layer and the Mg-Al alloy substrate. Fig. 9 (b-c) shows a magnified observation to oxide films, indicating a multi-layered structure (denoted by the red box in Fig. 9c). The bottom layer was enriched with fluorine and oxygen and should be the mixture of fluoride and oxide, which was similar to the “outer layer” shown in Figs. 5 and 7, while the only-oxygen-enriched top layer was similar to the “inner layer” shown in Figs. 5 and 7.

Fig. 9. (a) A cross-sectional observation of the oxide film on the fracture surface of the AZ91 casting produced in SF6/CO2, exposed by FIB, (b) a magnified observation of area highlighted in (a), and (c) SEM-EDS elements map of the area shown in (b), obtained by CFEI Quanta 3D FEG FIB-SEM.

Except the continuous film, some individual particles were also observed in or below the continuous film, as shown in Fig. 9. An Al-enriched particle was detected in the left side of the oxide film shown in Fig. 9b and might be speculated to be spinel Mg2AlO4 because it also contains abundant magnesium and oxygen elements. The existing of such Mg2AlO4 particles is responsible for the high concentration of aluminium in small areas of the observed film and the uneven distribution of aluminium, as shown in Fig. 5(c). Here it should be emphasized that, although the other part of the bottom layer of the continuous oxide film contains less aluminium than this Al-enriched particle, the Fig. 9c indicated that the amount of aluminium in this bottom layer was still non-negligible, especially when comparing with the outer layer of the film. Below the right side of the oxide film shown in Fig. 9b, a particle was detected and speculated to be MgO because it is rich in Mg and O. According to Wang’s result [56], lots of discrete MgO particles can be formed on the surface of the Mg melt by the oxidation of Mg melt and Mg vapor. The MgO particles observed in our present work may be formed due to the same reasons. While, due to the differences in experimental conditions, less Mg melt can be vapored or react with O2, thus only a few of MgO particles formed in our work. An enrichment of carbon was also found in the film, revealing that CO2 was able to react with the melt, thus forming carbon or carbides. This carbon concentration was consistent with the relatively high carbon content of the oxide film shown in Table 3 (i.e., the dark region). In the area next to the oxide film.

Table 3. EDS results (wt.%) corresponding to the regions shown in Fig. 8 (cover gas: SF6/ CO2).

Empty CellCOMgFAlZnSN
Dark region in Fig. 8(a)7.253.6469.823.827.030.86
Bright region in Fig. 8(a)2.100.4482.8313.261.36

This cross-sectional observation of the oxide film on a test bar fracture surface (Fig. 9) further verified the schematic of the entrainment defect shown in Fig. 6(e). The entrainment defects formed in different atmospheres of SF6/CO2 and SF6/air had similar structures, but their compositions were different.

3.3. Evolution of the oxide films in the oxidation cell

The results in Section 3.1 and 3.2 have shown the structures and compositions of entrainment defects formed in AZ91 castings under cover gases of SF6/air and SF6/CO2. Different stages of the oxidation reaction may lead to the different structures and compositions of entrainment defects. Although Campbell has conjectured that an entrained gas may react with the surrounding melt, it is rarely reported that the reaction occurring between the Mg-alloy melt and entrapped cover gas. Previous researchers normally focus on the reaction between a Mg-alloy melt and the cover gas in an open environment [38,39,[46][47][48][49][50][51][52], which was different from the situation of a cover gas trapped into the melt. To further understand the formation of the entrainment defect in an AZ91 alloy, the evolution process of oxide films of the entrainment defect was further studied using an oxidation cell.

Fig. 10 (a and d) shows a surface film held for 5 min in the oxidation cell, protected by 0.5%SF6/air. There was only one single layer consisting of fluoride and oxide (MgF2 and MgO). In this surface film. Sulphur was detected in the EDS spectrum, but its amount was too small to be recognized in the element map. The structure and composition of this oxide film was similar to the single-layered films of entrainment defects shown in Fig. 4.

Fig. 10. Oxide films formed in the oxidation cell under a cover gas of 0.5%SF6/air and held at 700 °C for (a) 5 min; (b) 10 min; (c) 30 min, and (d-f) the SEM-EDS element maps (using Philips JEOL7000) corresponding to the oxide film shown in (a-c) respectively, (d) 5 min; (e) 10 min; (f) 30 min. The red points in (c and f) are the location references, denoting the boundary of the F-enriched layer in different element maps.

After a holding time of 10 min, a thin (O, S)-enriched top layer (around 700 nm) appeared upon the preliminary F-enriched film, forming a multi-layered structure, as shown in Fig. 10(b and e). The thickness of the (O, S)-enriched top layer increased with increased holding time. As shown in Fig. 10(c and f), the oxide film held for 30 min also had a multi-layered structure, but the thickness of its (O, S)-enriched top layer (around 2.5 µm) was higher than the that of the 10-min oxide film. The multi-layered oxide films shown in Fig. 10(b-c) presented a similar appearance to the films of the sandwich-like defect shown in Fig. 5.

The different structures of the oxide films shown in Fig. 10 indicated that fluorides in the cover gas would be preferentially consumed due to the reaction with the AZ91 alloy melt. After the depletion of fluorides, the residual cover gas reacted further with the liquid AZ91 alloy, forming the top (O, S)-enriched layer in the oxide film. Therefore, the different structures and compositions of entrainment defects shown in Figs. 4 and 5 may be due to an ongoing oxidation reaction between melt and entrapped cover gas.

This multi-layered structure has not been reported in previous publications concerning the protective surface film formed on a Mg-alloy melt [38,[46][47][48][49][50][51]. This may be due to the fact that previous researchers carried out their experiments with an un-limited amount of cover gas, creating a situation where the fluorides in the cover gas were not able to become depleted. Therefore, the oxide film of an entrainment defect had behaviour traits similar to the oxide films shown in Fig. 10, but different from the oxide films formed on the Mg-alloy melt surface reported in [38,[46][47][48][49][50][51].

Similar with the oxide films held in SF6/air, the oxide films formed in SF6/CO2 also had different structures with different holding times in the oxidation cell. Fig. 11(a) shows an oxide film, held on an AZ91 melt surface under a cover gas of 0.5%SF6/CO2 for 5 min. This film had a single-layered structure consisting of MgF2. The existence of MgO could not be confirmed in this film. After the holding time of 30 min, the film had a multi-layered structure; the inner layer was of a compact and uniform appearance and composed of MgF2, while the outer layer is the mixture of MgF2 and MgO. Sulphur was not detected in this film, which was different from the surface film formed in 0.5%SF6/air. Therefore, fluorides in the cover gas of 0.5%SF6/CO2 were also preferentially consumed at an early stage of the film growth process. Compared with the film formed in SF6/air, the MgO in film formed in SF6/CO2 appeared later and sulphide did not appear within 30 min. It may mean that the formation and evolution of film in SF6/air is faster than SF6/CO2. CO2 may have subsequently reacted with the melt to form MgO, while sulphur-containing compounds accumulated in the cover gas and reacted to form sulphide in very late stage (may after 30 min in oxidation cell).

Fig. 11. Oxide films formed in the oxidation cell under a cover gas of 0.5%SF6/CO2, and their SEM-EDS element maps (using Philips JEOL7000). They were held at 700 °C for (a) 5 min; (b) 30 min. The red points in (b) are the location references, denoting the boundary between the top and bottom layers in the oxide film.

4. Discussion

4.1. Evolution of entrainment defects formed in SF6/air

HSC software from Outokumpu HSC Chemistry for Windows (http://www.hsc-chemistry.net/) was used to carry out thermodynamic calculations needed to explore the reactions which might occur between the trapped gases and liquid AZ91 alloy. The solutions to the calculations suggest which products are most likely to form in the reaction process between a small amount of cover gas (i.e., the amount within a trapped bubble) and the AZ91-alloy melt.

In the trials, the pressure was set to 1 atm, and the temperature set to 700 °C. The amount of the cover gas was assumed to be 7 × 10−7 kg, with a volume of approximately 0.57 cm3 (3.14 × 10−8 kmol) for 0.5%SF6/air, and 0.35 cm3 (3.12 × 10−8 kmol) for 0.5%SF6/CO2. The amount of the AZ91 alloy melt in contact with the trapped gas was assumed to be sufficient to complete all reactions. The decomposition products of SF6 were SF5, SF4, SF3, SF2, F2, S(g), S2(g) and F(g) [57][58][59][60].

Fig. 12 shows the equilibrium diagram of the thermodynamic calculation of the reaction between the AZ91 alloy and 0.5%SF6/air. In the diagram, the reactants and products with less than 10−15 kmol have not been shown, as this was 5 orders of magnitude less than the amount of SF6 present (≈ 1.57 × 10−10 kmol) and therefore would not affect the observed process in a practical way.

Fig. 12. An equilibrium diagram for the reaction between 7e-7 kg 0.5%SF6/air and a sufficient amount of AZ91 alloy. The X axis is the amount of AZ91 alloy melt having reacted with the entrained gas, and the vertical Y-axis is the amount of the reactants and products.

This reaction process could be divided into 3 stages.

Stage 1: The formation of fluorides. the AZ91 melt preferentially reacted with SF6 and its decomposition products, producing MgF2, AlF3, and ZnF2. However, the amount of ZnF2 may have been too small to be detected practically (1.25 × 10−12 kmol of ZnF2 compared with 3 × 10−10 kmol of MgF2), which may be the reason why Zn was not detected in any the oxide films shown in Sections 3.13.3. Meanwhile, sulphur accumulated in the residual gas as SO2.

Stage 2: The formation of oxides. After the liquid AZ91 alloy had depleted all the available fluorides in the entrapped gas, the amount of AlF3 and ZnF2 quickly reduced due to a reaction with Mg. O2(g) and SO2 reacted with the AZ91 melt, forming MgO, Al2O3, MgAl2O4, ZnO, ZnSO4 and MgSO4. However, the amount of ZnO and ZnSO4 would have been too small to be found practically by EDS (e.g. 9.5 × 10−12 kmol of ZnO,1.38 × 10−14 kmol of ZnSO4, in contrast to 4.68 × 10−10 kmol of MgF2, when the amount of AZ91 on the X-axis is 2.5 × 10−9 kmol). In the experimental cases, the concentration of F in the cover gas is very low, whole the concentration f O is much higher. Therefore, the stage 1 and 2, i.e, the formation of fluoride and oxide may happen simultaneously at the beginning of the reaction, resulting in the formation of a singer-layered mixture of fluoride and oxide, as shown in Figs. 4 and 10(a). While an inner layer consisted of oxides but fluorides could form after the complete depletion of F element in the cover gas.

Stages 1- 2 theoretically verified the formation process of the multi-layered structure shown in Fig. 10.

The amount of MgAl2O4 and Al2O3 in the oxide film was of a sufficient amount to be detected, which was consistent with the oxide films shown in Fig. 4. However, the existence of aluminium could not be recognized in the oxide films grown in the oxidation cell, as shown in Fig. 10. This absence of Al may be due to the following reactions between the surface film and AZ91 alloy melt:(1)

Al2O3 + 3Mg + = 3MgO + 2Al, △G(700 °C) = -119.82 kJ/mol(2)

Mg + MgAl2O4 = MgO + Al, △G(700 °C) =-106.34 kJ/molwhich could not be simulated by the HSC software since the thermodynamic calculation was carried out under an assumption that the reactants were in full contact with each other. However, in a practical process, the AZ91 melt and the cover gas would not be able to be in contact with each other completely, due to the existence of the protective surface film.

Stage 3: The formation of Sulphide and nitride. After a holding time of 30 min, the gas-phase fluorides and oxides in the oxidation cell had become depleted, allowing the melt reaction with the residual gas, forming an additional sulphur-enriched layer upon the initial F-enriched or (F, O)-enriched surface film, thus resulting in the observed multi-layered structure shown in Fig. 10 (b and c). Besides, nitrogen reacted with the AZ91 melt until all reactions were completed. The oxide film shown in Fig. 6 may correspond to this reaction stage due to its nitride content. However, the results shows that the nitrides were not detected in the polished samples shown in Figs. 4 and 5, but only found on the test bar fracture surfaces. The nitrides may have hydrolysed during the sample preparation process, as follows [54]:(3)

Mg3N2 + 6H2O =3Mg(OH)2 + 2NH3↑(4)

AlN+ 3H2O =Al(OH)3 + NH3

In addition, Schmidt et al. [61] found that Mg3N2 and AlN could react to form ternary nitrides (Mg3AlnNn+2, n= 1, 2, 3…). HSC software did not contain the database of ternary nitrides, and it could not be added into the calculation. The oxide films in this stage may also contain ternary nitrides.

4.2. Evolution of entrainment defects formed in SF6/CO2

Fig. 13 shows the results of the thermodynamic calculation between AZ91 alloy and 0.5%SF6/CO2. This reaction processes can also be divided into three stages.

Fig. 13. An equilibrium diagram for the reaction between 7e-7 kg 0.5%SF6/CO2 and a sufficient amount of AZ91 alloy. The X axis denotes the amount of Mg alloy melt having reacted with the entrained gas, and the vertical Y-axis denotes the amounts of the reactants and products.

Stage 1: The formation of fluorides. SF6 and its decomposition products were consumed by the AZ91 melt, forming MgF2, AlF3, and ZnF2. As in the reaction of AZ91 in 0.5%SF6/air, the amount of ZnF2 was too small to be detected practically (1.51 × 10−13 kmol of ZnF2 compared with 2.67 × 10−10 kmol of MgF2). Sulphur accumulated in the residual trapped gas as S2(g) and a portion of the S2(g) reacted with CO2, to form SO2 and CO. The products in this reaction stage were consistent with the film shown in Fig. 11(a), which had a single layer structure that contained fluorides only.

Stage 2: The formation of oxides. AlF3 and ZnF2 reacted with the Mg in the AZ91 melt, forming MgF2, Al and Zn. The SO2 began to be consumed, producing oxides in the surface film and S2(g) in the cover gas. Meanwhile, the CO2 directly reacted with the AZ91 melt, forming CO, MgO, ZnO, and Al2O3. The oxide films shown in Figs. 9 and 11(b) may correspond to this reaction stage due to their oxygen-enriched layer and multi-layered structure.

The CO in the cover gas could further react with the AZ91 melt, producing C. This carbon may further react with Mg to form Mg carbides, when the temperature reduced (during solidification period) [62]. This may be the reason for the high carbon content in the oxide film shown in Figs. 89. Liang et al. [39] also reported carbon-detection in an AZ91 alloy surface film protected by SO2/CO2. The produced Al2O3 may be further combined with MgO, forming MgAl2O4 [63]. As discussed in Section 4.1, the alumina and spinel can react with Mg, causing an absence of aluminium in the surface films, as shown in Fig. 11.

Stage 3: The formation of Sulphide. the AZ91 melt began to consume S2(g) in the residual entrapped gas, forming ZnS and MgS. These reactions did not occur until the last stage of the reaction process, which could be the reason why the S-content in the defect shown Fig. 7(c) was small.

In summary, thermodynamic calculations indicate that the AZ91 melt will react with the cover gas to form fluorides firstly, then oxides and sulphides in the last. The oxide film in the different reaction stages would have different structures and compositions.

4.3. Effect of the carrier gases on consumption of the entrained gas and the reproducibility of AZ91 castings

The evolution processes of entrainment defects, formed in SF6/air and SF6/CO2, have been suggested in Sections 4.1 and 4.2. The theoretical calculations were verified with respect to the corresponding oxide films found in practical samples. The atmosphere within an entrainment defect could be efficiently consumed due to the reaction with liquid Mg-alloy, in a scenario dissimilar to the Al-alloy system (i.e., nitrogen in an entrained air bubble would not efficiently react with Al-alloy melt [64,65], however, nitrogen would be more readily consumed in liquid Mg alloys, commonly referred to as “nitrogen burning” [66]).

The reaction between the entrained gas and the surrounding liquid Mg-alloy converted the entrained gas into solid compounds (e.g. MgO) within the oxide film, thus reducing the void volume of the entrainment defect and hence probably causing a collapse of the defect (e.g., if an entrained gas of air was depleted by the surrounding liquid Mg-alloy, under an assumption that the melt temperature is 700 °C and the depth of liquid Mg-alloy is 10 cm, the total volume of the final solid products would be 0.044% of the initial volume taken by the entrapped air).

The relationship between the void volume reduction of entrainment defects and the corresponding casting properties has been widely studied in Al-alloy castings. Nyahumwa and Campbell [16] reported that the Hot Isostatic Pressing (HIP) process caused the entrainment defects in Al-alloy castings to collapse and their oxide surfaces forced into contact. The fatigue lives of their castings were improved after HIP. Nyahumwa and Campbell [16] also suggested a potential bonding of the double oxide films that were in contact with each other, but there was no direct evidence to support this. This binding phenomenon was further investigated by Aryafar et.al.[8], who re-melted two Al-alloy bars with oxide skins in a steel tube and then carried out a tensile strength test on the solidified sample. They found that the oxide skins of the Al-alloy bars strongly bonded with each other and became even stronger with an extension of the melt holding time, indicating a potential “healing” phenomenon due to the consumption of the entrained gas within the double oxide film structure. In addition, Raidszadeh and Griffiths [9,19] successfully reduced the negative effect of entrainment defects on the reproducibility of Al-alloy castings, by extending the melt holding time before solidification, which allowed the entrained gas to have a longer time to react with the surrounding melt.

With consideration of the previous work mentioned, the consumption of the entrained gas in Mg-alloy castings may diminish the negative effect of entrainment defects in the following two ways.

(1) Bonding phenomenon of the double oxide films. The sandwich-like structure shown in Fig. 5 and 7 indicated a potential bonding of the double oxide film structure. However, more evidence is required to quantify the increase in strength due to the bonding of the oxide films.

(2) Void volume reduction of entrainment defects. The positive effect of void-volume reduction on the quality of castings has been widely demonstrated by the HIP process [67]. As the evolution processes discussed in Section 4.14.2, the oxide films of entrainment defects can grow together due to an ongoing reaction between the entrained gas and surrounding AZ91 alloy melt. The volume of the final solid products was significant small compared with the entrained gas (i.e., 0.044% as previously mentioned).

Therefore, the consumption rate of the entrained gas (i.e., the growth rate of oxide films) may be a critical parameter for improving the quality of AZ91 alloy castings. The oxide film growth rate in the oxidization cell was accordingly further investigated.

Fig. 14 shows a comparison of the surface film growth rates in different cover gases (i.e., 0.5%SF6/air and 0.5%SF6/CO2). 15 random points on each sample were selected for film thickness measurements. The 95% confidence interval (95%CI) was computed under an assumption that the variation of the film thickness followed a Gaussian distribution. It can be seen that all the surface films formed in 0.5%SF6/air grew faster than those formed in 0.5%SF6/CO2. The different growth rates suggested that the entrained-gas consumption rate of 0.5%SF6/air was higher than that of 0.5%SF6/CO2, which was more beneficial for the consumption of the entrained gas.

Fig. 14. A comparison of the AZ91 alloy oxide film growth rates in 0.5%SF6/air and 0.5%SF6/CO2

It should be noted that, in the oxidation cell, the contact area of liquid AZ91 alloy and cover gas (i.e. the size of the crucible) was relatively small with consideration of the large volume of melt and gas. Consequently, the holding time for the oxide film growth within the oxidation cell was comparatively long (i.e., 5–30 min). However, the entrainment defects contained in a real casting are comparatively very small (i.e., a few microns size as shown in Figs. 36, and [7]), and the entrained gas is fully enclosed by the surrounding melt, creating a relatively large contact area. Hence the reaction time for cover gas and the AZ91 alloy melt may be comparatively short. In addition, the solidification time of real Mg-alloy sand castings can be a few minutes (e.g. Guo [68] reported that a Mg-alloy sand casting with 60 mm diameter required 4 min to be solidified). Therefore, it can be expected that an entrained gas trapped during an Mg-alloy melt pouring process will be readily consumed by the surrounding melt, especially for sand castings and large-size castings, where solidification times are long.

Therefore, the different cover gases (0.5%SF6/air and 0.5%SF6/CO2) associated with different consumption rates of the entrained gases may affect the reproducibility of the final castings. To verify this assumption, the AZ91 castings produced in 0.5%SF6/air and 0.5%SF6/CO2 were machined into test bars for mechanical evaluation. A Weibull analysis was carried out using both linear least square (LLS) method and non-linear least square (non-LLS) method [69].

Fig. 15(a-b) shows a traditional 2-p linearized Weibull plot of the UTS and elongation of the AZ91 alloy castings, obtained by the LLS method. The estimator used is P= (i-0.5)/N, which was suggested to cause the lowest bias among all the popular estimators [69,70]. The casting produced in SF6/air has an UTS Weibull moduli of 16.9, and an elongation Weibull moduli of 5.0. In contrast, the UTS and elongation Weibull modulus of the casting produced in SF6/CO2 are 7.7 and 2.7 respectively, suggesting that the reproducibility of the casting protected by SF6/CO2 were much lower than that produced in SF6/air.

Fig. 15. The Weibull modulus of AZ91 castings produced in different atmospheres, estimated by (a-b) the linear least square method, (c-d) the non-linear least square method, where SSR is the sum of residual squares.

In addition, the author’s previous publication [69] demonstrated a shortcoming of the linearized Weibull plots, which may cause a higher bias and incorrect R2 interruption of the Weibull estimation. A Non-LLS Weibull estimation was therefore carried out, as shown in Fig. 15 (c-d). The UTS Weibull modulus of the SF6/air casting was 20.8, while the casting produced under SF6/CO2 had a lower UTS Weibull modulus of 11.4, showing a clear difference in their reproducibility. In addition, the SF6/air elongation (El%) dataset also had a Weibull modulus (shape = 5.8) higher than the elongation dataset of SF6/CO2 (shape = 3.1). Therefore, both the LLS and Non-LLS estimations suggested that the SF6/air casting has a higher reproducibility than the SF6/CO2 casting. It supports the method that the use of air instead of CO2 contributes to a quicker consumption of the entrained gas, which may reduce the void volume within the defects. Therefore, the use of 0.5%SF6/air instead of 0.5%SF6/CO2 (which increased the consumption rate of the entrained gas) improved the reproducibility of the AZ91 castings.

However, it should be noted that not all the Mg-alloy foundries followed the casting process used in present work. The Mg-alloy melt in present work was degassed, thus reducing the effect of hydrogen on the consumption of the entrained gas (i.e., hydrogen could diffuse into the entrained gas, potentially suppressing the depletion of the entrained gas [7,71,72]). In contrast, in Mg-alloy foundries, the Mg-alloy melt is not normally degassed, since it was widely believed that there is not a ‘gas problem’ when casting magnesium and hence no significant change in tensile properties [73]. Although studies have shown the negative effect of hydrogen on the mechanical properties of Mg-alloy castings [41,42,73], a degassing process is still not very popular in Mg-alloy foundries.

Moreover, in present work, the sand mould cavity was flushed with the SF6 cover gas prior to pouring [22]. However, not all the Mg-alloy foundries flushed the mould cavity in this way. For example, the Stone Foundry Ltd (UK) used sulphur powder instead of the cover-gas flushing. The entrained gas within their castings may be SO2/air, rather than the protective gas.

Therefore, although the results in present work have shown that using air instead of CO2 improved the reproducibility of the final casting, it still requires further investigations to confirm the effect of carrier gases with respect to different industrial Mg-alloy casting processes.

7. Conclusion

Entrainment defects formed in an AZ91 alloy were observed. Their oxide films had two types of structure: single-layered and multi-layered. The multi-layered oxide film can grow together forming a sandwich-like structure in the final casting.2.

Both the experimental results and the theoretical thermodynamic calculations demonstrated that fluorides in the trapped gas were depleted prior to the consumption of sulphur. A three-stage evolution process of the double oxide film defects has been suggested. The oxide films contained different combinations of compounds, depending on the evolution stage. The defects formed in SF6/air had a similar structure to those formed in SF6/CO2, but the compositions of their oxide films were different. The oxide-film formation and evolution process of the entrainment defects were different from that of the Mg-alloy surface films previous reported (i.e., MgO formed prior to MgF2).3.

The growth rate of the oxide film was demonstrated to be greater under SF6/air than SF6/CO2, contributing to a quicker consumption of the damaging entrapped gas. The reproducibility of an AZ91 alloy casting improved when using SF6/air instead of SF6/CO2.

Acknowledgements

The authors acknowledge funding from the EPSRC LiME grant EP/H026177/1, and the help from Dr W.D. Griffiths and Mr. Adrian Carden (University of Birmingham). The casting work was carried out in University of Birmingham.

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Fig. 1. Schematic of lap welding for 6061/5182 aluminum alloys.

알루미늄 합금 겹침 용접 중 용접 형성, 용융 흐름 및 입자 구조에 대한 사인파 발진 레이저 빔의 영향

린 첸 가오 양 미시 옹 장 춘밍 왕
Lin Chen , Gaoyang Mi , Xiong Zhang , Chunming Wang *
중국 우한시 화중과학기술대학 재료공학부, 430074

Effects of sinusoidal oscillating laser beam on weld formation, melt flow and grain structure during aluminum alloys lap welding

Abstract

A numerical model of 1.5 mm 6061/5182 aluminum alloys thin sheets lap joints under laser sinusoidal oscillation (sine) welding and laser welding (SLW) weld was developed to simulate temperature distribution and melt flow. Unlike the common energy distribution of SLW, the sinusoidal oscillation of laser beam greatly homogenized the energy distribution and reduced the energy peak. The energy peaks were located at both sides of the sine weld, resulting in the tooth-shaped sectional formation. This paper illustrated the effect of the temperature gradient (G) and solidification rate (R) on the solidification microstructure by simulation. Results indicated that the center of the sine weld had a wider area with low G/R, promoting the formation of a wider equiaxed grain zone, and the columnar grains were slenderer because of greater GR. The porosity-free and non-penetration welds were obtained by the laser sinusoidal oscillation. The reasons were that the molten pool volume was enlarged, the volume proportion of keyhole was reduced and the turbulence in the molten pool was gentled, which was observed by the high-speed imaging and simulation results of melt flow. The tensile test of both welds showed a tensile fracture form along the fusion line, and the tensile strength of sine weld was significantly better than that of the SLW weld. This was because that the wider equiaxed grain area reduced the tendency of cracks and the finer grain size close to the fracture location. Defect-free and excellent welds are of great significance to the new energy vehicles industry.

온도 분포 및 용융 흐름을 시뮬레이션하기 위해 레이저 사인파 진동 (사인) 용접 및 레이저 용접 (SLW) 용접에서 1.5mm 6061/5182 알루미늄 합금 박판 랩 조인트 의 수치 모델이 개발되었습니다. SLW의 일반적인 에너지 분포와 달리 레이저 빔의 사인파 진동은 에너지 분포를 크게 균질화하고 에너지 피크를 줄였습니다. 에너지 피크는 사인 용접의 양쪽에 위치하여 톱니 모양의 단면이 형성되었습니다. 이 논문은 온도 구배(G)와 응고 속도 의 영향을 설명했습니다.(R) 시뮬레이션에 의한 응고 미세 구조. 결과는 사인 용접의 중심이 낮은 G/R로 더 넓은 영역을 가짐으로써 더 넓은 등축 결정립 영역의 형성을 촉진하고 더 큰 GR로 인해 주상 결정립 이 더 가늘다는 것을 나타냅니다. 다공성 및 비관통 용접은 레이저 사인파 진동에 의해 얻어졌습니다. 그 이유는 용융 풀의 부피가 확대되고 열쇠 구멍의 부피 비율이 감소하며 용융 풀의 난류가 완만해졌기 때문이며, 이는 용융 흐름의 고속 이미징 및 시뮬레이션 결과에서 관찰되었습니다. 두 용접부 의 인장시험 은 융착선을 따라 인장파괴형태를인장강도사인 용접의 경우 SLW 용접보다 훨씬 우수했습니다. 이는 등축 결정립 영역이 넓을수록 균열 경향이 감소하고 파단 위치에 근접한 입자 크기가 미세 하기 때문입니다. 결함이 없고 우수한 용접은 신에너지 자동차 산업에 매우 중요합니다.

Fig. 1. Schematic of lap welding for 6061/5182 aluminum alloys.
Fig. 1. Schematic of lap welding for 6061/5182 aluminum alloys.
Fig. 2. Finite element mesh.
Fig. 2. Finite element mesh.
Fig. 3. Weld morphologies of cross-section and upper surface for the two welds: (a) sine pattern weld; (b) SLW weld.
Fig. 3. Weld morphologies of cross-section and upper surface for the two welds: (a) sine pattern weld; (b) SLW weld.
Fig. 4. Calculation of laser energy distribution: (a)-(c) sine pattern weld; (d)-(f) SLW weld.
Fig. 4. Calculation of laser energy distribution: (a)-(c) sine pattern weld; (d)-(f) SLW weld.
Fig. 5. The partially melted region of zone A.
Fig. 5. The partially melted region of zone A.
Fig. 6. The simulated profiles of melted region for the two welds: (a) SLW weld; (b) sine pattern weld.
Fig. 6. The simulated profiles of melted region for the two welds: (a) SLW weld; (b) sine pattern weld.
Fig. 7. The temperature field simulation results of cross section for sine pattern weld.
Fig. 7. The temperature field simulation results of cross section for sine pattern weld.
Fig. 8. Dynamic behavior of the molten pool at the same time interval of 0.004 s within one oscillating period: (a) SLW weld; (b) sine pattern weld.
Fig. 8. Dynamic behavior of the molten pool at the same time interval of 0.004 s within one oscillating period: (a) SLW weld; (b) sine pattern weld.
Fig. 9. The temperature field and flow field of the molten pool for the SLW weld: (a)~(f) t = 80 ms~100 ms.
Fig. 9. The temperature field and flow field of the molten pool for the SLW weld: (a)~(f) t = 80 ms~100 ms.
Fig. 10. The temperature field and flow field of the molten pool for the sine pattern weld: (a)~(f) t = 151 ms~171 ms.
Fig. 10. The temperature field and flow field of the molten pool for the sine pattern weld: (a)~(f) t = 151 ms~171 ms.
Fig. 11. The evolution of the molten pool volume and keyhole depth within one period.
Fig. 11. The evolution of the molten pool volume and keyhole depth within one period.
Fig. 12. The X-ray inspection results for the two welds: (a) SLW weld, (b) sine pattern weld.
Fig. 12. The X-ray inspection results for the two welds: (a) SLW weld, (b) sine pattern weld.
Fig. 13. Comparison of the solidification parameters for sine and SLW patterns: (a) the temperature field simulated results of the molten pool upper surfaces; (b) temperature gradient G and solidification rate R along the molten pool boundary isotherm from weld centerline to the fusion boundary; (c) G/R; (d) GR.
Fig. 13. Comparison of the solidification parameters for sine and SLW patterns: (a) the temperature field simulated results of the molten pool upper surfaces; (b) temperature gradient G and solidification rate R along the molten pool boundary isotherm from weld centerline to the fusion boundary; (c) G/R; (d) GR.
Fig. 14. The EBSD results of equiaxed grain zone in the weld center of: (a) sine pattern weld; (b) SLW weld; (c) grain size.
Fig. 14. The EBSD results of equiaxed grain zone in the weld center of: (a) sine pattern weld; (b) SLW weld; (c) grain size.
Fig. 15. (a) EBSD results of horizontal sections of SLW weld and sine pattern weld; (b) The columnar crystal widths of SLW weld and sine pattern weld.
Fig. 15. (a) EBSD results of horizontal sections of SLW weld and sine pattern weld; (b) The columnar crystal widths of SLW weld and sine pattern weld.
Fig. 16. (a) The tensile test results of the two welds; (b) Fracture location of SLW weld; (b) Fracture location of sine pattern weld.
Fig. 16. (a) The tensile test results of the two welds; (b) Fracture location of SLW weld; (b) Fracture location of sine pattern weld.

Keywords

Laser welding, Sinusoidal oscillating, Energy distribution, Numerical simulation, Molten pool flow, Grain structure

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Fig. 1 Multi-physics phenomena in the laser-material interaction zone

COMPARISON BETWEEN GREEN AND
INFRARED LASER IN LASER POWDER BED
FUSION OF PURE COPPER THROUGH HIGH
FIDELITY NUMERICAL MODELLING AT MESOSCALE

316-L 스테인리스강의 레이저 분말 베드 융합 중 콜드 스패터 형성의 충실도 높은 수치 모델링

W.E. ALPHONSO1*, M. BAYAT1 and J.H. HATTEL1
*Corresponding author
1Technical University of Denmark (DTU), 2800, Kgs, Lyngby, Denmark

ABSTRACT

L-PBF(Laser Powder Bed Fusion)는 금속 적층 제조(MAM) 기술로, 기존 제조 공정에 비해 부품 설계 자유도, 조립품 통합, 부품 맞춤화 및 낮은 툴링 비용과 같은 여러 이점을 산업에 제공합니다.

전기 코일 및 열 관리 장치는 일반적으로 높은 전기 및 열 전도성 특성으로 인해 순수 구리로 제조됩니다. 따라서 순동의 L-PBF가 가능하다면 기하학적으로 최적화된 방열판과 자유형 전자코일을 제작할 수 있습니다.

그러나 L-PBF로 조밀한 순동 부품을 생산하는 것은 적외선에 대한 낮은 광 흡수율과 높은 열전도율로 인해 어렵습니다. 기존의 L-PBF 시스템에서 조밀한 구리 부품을 생산하려면 적외선 레이저의 출력을 500W 이상으로 높이거나 구리의 광흡수율이 높은 녹색 레이저를 사용해야 합니다.

적외선 레이저 출력을 높이면 후면 반사로 인해 레이저 시스템의 광학 구성 요소가 손상되고 렌즈의 열 광학 현상으로 인해 공정이 불안정해질 수 있습니다. 이 작업에서 FVM(Finite Volume Method)에 기반한 다중 물리학 중간 규모 수치 모델은 Flow-3D에서 개발되어 용융 풀 역학과 궁극적으로 부품 품질을 제어하는 ​​물리적 현상 상호 작용을 조사합니다.

녹색 레이저 열원과 적외선 레이저 열원은 기판 위의 순수 구리 분말 베드에 단일 트랙 증착을 생성하기 위해 개별적으로 사용됩니다.

용융 풀 역학에 대한 레이저 열원의 유사하지 않은 광학 흡수 특성의 영향이 탐구됩니다. 수치 모델을 검증하기 위해 단일 트랙이 구리 분말 베드에 증착되고 시뮬레이션된 용융 풀 모양과 크기가 비교되는 실험이 수행되었습니다.

녹색 레이저는 광흡수율이 높아 전도 및 키홀 모드 용융이 가능하고 적외선 레이저는 흡수율이 낮아 키홀 모드 용융만 가능하다. 레이저 파장에 대한 용융 모드의 변화는 궁극적으로 기계적, 전기적 및 열적 특성에 영향을 미치는 열 구배 및 냉각 속도에 대한 결과를 가져옵니다.

Laser Powder Bed Fusion (L-PBF) is a Metal Additive Manufacturing (MAM) technology which offers several advantages to industries such as part design freedom, consolidation of assemblies, part customization and low tooling cost over conventional manufacturing processes. Electric coils and thermal management devices are generally manufactured from pure copper due to its high electrical and thermal conductivity properties. Therefore, if L-PBF of pure copper is feasible, geometrically optimized heat sinks and free-form electromagnetic coils can be manufactured. However, producing dense pure copper parts by L-PBF is difficult due to low optical absorptivity to infrared radiation and high thermal conductivity. To produce dense copper parts in a conventional L-PBF system either the power of the infrared laser must be increased above 500W, or a green laser should be used for which copper has a high optical absorptivity. Increasing the infrared laser power can damage the optical components of the laser systems due to back reflections and create instabilities in the process due to thermal-optical phenomenon of the lenses. In this work, a multi-physics meso-scale numerical model based on Finite Volume Method (FVM) is developed in Flow-3D to investigate the physical phenomena interaction which governs the melt pool dynamics and ultimately the part quality. A green laser heat source and an infrared laser heat source are used individually to create single track deposition on pure copper powder bed above a substrate. The effect of the dissimilar optical absorptivity property of laser heat sources on the melt pool dynamics is explored. To validate the numerical model, experiments were conducted wherein single tracks are deposited on a copper powder bed and the simulated melt pool shape and size are compared. As the green laser has a high optical absorptivity, a conduction and keyhole mode melting is possible while for the infrared laser only keyhole mode melting is possible due to low absorptivity. The variation in melting modes with respect to the laser wavelength has an outcome on thermal gradient and cooling rates which ultimately affect the mechanical, electrical, and thermal properties.

Keywords

Pure Copper, Laser Powder Bed Fusion, Finite Volume Method, multi-physics

Fig. 1 Multi-physics phenomena in the laser-material interaction zone
Fig. 1 Multi-physics phenomena in the laser-material interaction zone
Fig. 2 Framework for single laser track simulation model including powder bed and substrate (a) computational domain with boundaries (b) discretization of the domain with uniform quad mesh.
Fig. 2 Framework for single laser track simulation model including powder bed and substrate (a) computational domain with boundaries (b) discretization of the domain with uniform quad mesh.
Fig. 3 2D melt pool contours from the numerical model compared to experiments [16] for (a) VED = 65 J/mm3 at 7 mm from the beginning of the single track (b) VED = 103 J/mm3 at 3 mm from the beginning of the single track (c) VED = 103 J/mm3 at 7 mm from the beginning of the single track. In the 2D contour, the non-melted region is indicated in blue, and the melted region is indicated by red and green when the VED is 65 J/mm3 and 103 J/mm3 respectively.
Fig. 3 2D melt pool contours from the numerical model compared to experiments [16] for (a) VED = 65 J/mm3 at 7 mm from the beginning of the single track (b) VED = 103 J/mm3 at 3 mm from the beginning of the single track (c) VED = 103 J/mm3 at 7 mm from the beginning of the single track. In the 2D contour, the non-melted region is indicated in blue, and the melted region is indicated by red and green when the VED is 65 J/mm3 and 103 J/mm3 respectively.
Fig. 4 3D temperature contour plots of during single track L-PBF process at time1.8 µs when (a) VED = 65 J/mm3 (b) VED = 103 J/mm3 along with 2D melt pool contours at 5 mm from the laser initial position. In the 2D contour, the non-melted region is indicated in blue, and the melted region is indicated by red and green when the VED is 65 J/mm3 and 103 J/mm3 respectively.
Fig. 4 3D temperature contour plots of during single track L-PBF process at time1.8 µs when (a) VED = 65 J/mm3 (b) VED = 103 J/mm3 along with 2D melt pool contours at 5 mm from the laser initial position. In the 2D contour, the non-melted region is indicated in blue, and the melted region is indicated by red and green when the VED is 65 J/mm3 and 103 J/mm3 respectively.

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Fig. 1. Schematic figure showing the PREP with additional gas flowing on the end face of electrode.

플라즈마 회전 전극 공정 중 분말 형성에 대한 공정 매개변수 및 냉각 가스의 영향

Effects of process parameters and cooling gas on powder formation during the plasma rotating electrode process

Yujie Cuia Yufan Zhaoa1 Haruko Numatab Kenta Yamanakaa Huakang Biana Kenta Aoyagia AkihikoChibaa
aInstitute for Materials Research, Tohoku University, Sendai 980-8577, JapanbDepartment of Materials Processing, Graduate School of Engineering, Tohoku University, Sendai 980-8577, Japan

Highlights

•The limitation of increasing the rotational speed in decreasing powder size was clarified.

•Cooling and disturbance effects varied with the gas flowing rate.

•Inclined angle of the residual electrode end face affected powder formation.

•Additional cooling gas flowing could be applied to control powder size.

Abstract

The plasma rotating electrode process (PREP) is rapidly becoming an important powder fabrication method in additive manufacturing. However, the low production rate of fine PREP powder limits the development of PREP. Herein, we investigated different factors affecting powder formation during PREP by combining experimental methods and numerical simulations. The limitation of increasing the rotation electrode speed in decreasing powder size is attributed to the increased probability of adjacent droplets recombining and the decreased tendency of granulation. The effects of additional Ar/He gas flowing on the rotational electrode on powder formation is determined through the cooling effect, the disturbance effect, and the inclined effect of the residual electrode end face simultaneously. A smaller-sized powder was obtained in the He atmosphere owing to the larger inclined angle of the residual electrode end face compared to the Ar atmosphere. Our research highlights the route for the fabrication of smaller-sized powders using PREP.

플라즈마 회전 전극 공정(PREP)은 적층 제조 에서 중요한 분말 제조 방법으로 빠르게 자리잡고 있습니다. 그러나 미세한 PREP 분말의 낮은 생산율은 PREP의 개발을 제한합니다. 여기에서 우리는 실험 방법과 수치 시뮬레이션을 결합하여 PREP 동안 분말 형성에 영향을 미치는 다양한 요인을 조사했습니다. 분말 크기 감소에서 회전 전극 속도 증가의 한계는 인접한 액적 재결합 확률 증가 및 과립화 경향 감소에 기인합니다.. 회전 전극에 흐르는 추가 Ar/He 가스가 분말 형성에 미치는 영향은 냉각 효과, 외란 효과 및 잔류 전극 단면의 경사 효과를 통해 동시에 결정됩니다. He 분위기에서는 Ar 분위기에 비해 잔류 전극 단면의 경사각이 크기 때문에 더 작은 크기의 분말이 얻어졌다. 우리의 연구는 PREP를 사용하여 더 작은 크기의 분말을 제조하는 경로를 강조합니다.

Keywords

Plasma rotating electrode process

Ti-6Al-4 V alloy, Rotating speed, Numerical simulation, Gas flowing, Powder size

Introduction

With the development of additive manufacturing, there has been a significant increase in high-quality powder production demand [1,2]. The initial powder characteristics are closely related to the uniform powder spreading [3,4], packing density [5], and layer thickness observed during additive manufacturing [6], thus determining the mechanical properties of the additive manufactured parts [7,8]. Gas atomization (GA) [9–11], centrifugal atomization (CA) [12–15], and the plasma rotating electrode process (PREP) are three important powder fabrication methods.

Currently, GA is the dominant powder fabrication method used in additive manufacturing [16] for the fabrication of a wide range of alloys [11]. GA produces powders by impinging a liquid metal stream to droplets through a high-speed gas flow of nitrogen, argon, or helium. With relatively low energy consumption and a high fraction of fine powders, GA has become the most popular powder manufacturing technology for AM.

The entrapped gas pores are generally formed in the powder after solidification during GA, in which the molten metal is impacted by a high-speed atomization gas jet. In addition, satellites are formed in GA powder when fine particles adhere to partially molten particles.

The gas pores of GA powder result in porosity generation in the additive manufactured parts, which in turn deteriorates its mechanical properties because pores can become crack initiation sites [17]. In CA, a molten metal stream is poured directly onto an atomizer disc spinning at a high rotational speed. A thin film is formed on the surface of the disc, which breaks into small droplets due to the centrifugal force. Metal powder is obtained when these droplets solidify.

Compared with GA powder, CA powder exhibits higher sphericity, lower impurity content, fewer satellites, and narrower particle size distribution [12]. However, very high speed is required to obtain fine powder by CA. In PREP, the molten metal, melted using the plasma arc, is ejected from the rotating rod through centrifugal force. Compared with GA powder, PREP-produced powders also have higher sphericity and fewer pores and satellites [18].

For instance, PREP-fabricated Ti6Al-4 V alloy powder with a powder size below 150 μm exhibits lower porosity than gas-atomized powder [19], which decreases the porosity of additive manufactured parts. Furthermore, the process window during electron beam melting was broadened using PREP powder compared to GA powder in Inconel 718 alloy [20] owing to the higher sphericity of the PREP powder.

In summary, PREP powder exhibits many advantages and is highly recommended for powder-based additive manufacturing and direct energy deposition-type additive manufacturing. However, the low production rate of fine PREP powder limits the widespread application of PREP powder in additive manufacturing.

Although increasing the rotating speed is an effective method to decrease the powder size [21,22], the reduction in powder size becomes smaller with the increased rotating speed [23]. The occurrence of limiting effects has not been fully clarified yet.

Moreover, the powder size can be decreased by increasing the rotating electrode diameter [24]. However, these methods are quite demanding for the PREP equipment. For instance, it is costly to revise the PREP equipment to meet the demand of further increasing the rotating speed or electrode diameter.

Accordingly, more feasible methods should be developed to further decrease the PREP powder size. Another factor that influences powder formation is the melting rate [25]. It has been reported that increasing the melting rate decreases the powder size of Inconel 718 alloy [26].

In contrast, the powder size of SUS316 alloy was decreased by decreasing the plasma current within certain ranges. This was ascribed to the formation of larger-sized droplets from fluid strips with increased thickness and spatial density at higher plasma currents [27]. The powder size of NiTi alloy also decreases at lower melting rates [28]. Consequently, altering the melting rate, varied with the plasma current, is expected to regulate the PREP powder size.

Furthermore, gas flowing has a significant influence on powder formation [27,29–31]. On one hand, the disturbance effect of gas flowing promotes fluid granulation, which in turn contributes to the formation of smaller-sized powder [27]. On the other hand, the cooling effect of gas flowing facilitates the formation of large-sized powder due to increased viscosity and surface tension. However, there is a lack of systematic research on the effect of different gas flowing on powder formation during PREP.

Herein, the authors systematically studied the effects of rotating speed, electrode diameter, plasma current, and gas flowing on the formation of Ti-6Al-4 V alloy powder during PREP as additive manufactured Ti-6Al-4 V alloy exhibits great application potential [32]. Numerical simulations were conducted to explain why increasing the rotating speed is not effective in decreasing powder size when the rotation speed reaches a certain level. In addition, the different factors incited by the Ar/He gas flowing on powder formation were clarified.

Fig. 1. Schematic figure showing the PREP with additional gas flowing on the end face of electrode.
Fig. 1. Schematic figure showing the PREP with additional gas flowing on the end face of electrode.

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Fig. 3. Experimental angled top-view setup for laser welding of zinc-coated steel with a laser illumination.

Effect of zinc vapor forces on spattering in partial penetration laser welding of zinc-coated steels

Yu Hao a, Nannan Chen a,b, Hui-Ping Wang c,*, Blair E. Carlson c, Fenggui Lu a,*
a Shanghai Key Laboratory of Materials Laser Processing and Modification, School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai,
200240, PR China b Department of Industrial and Manufacturing Eng

ABSTRACT

A three-dimensional thermal-fluid numerical model considering zinc vapor interaction with the molten pool was developed to study the occurrence of zinc vapor-induced spatter in partial penetration laser overlap welding of zinc-coated steels. The zinc vapor effect was represented by two forces: a jet pressure force acting on the keyhole rear wall as the vapor bursts into the keyhole and a drag force on the upper keyhole wall as the vapor escapes upwards. The numerical model was calibrated by comparing the predicted keyhole shape with the keyhole shape observed by high-speed X-ray imaging and applied for various weld schedules. The study showed that large jet pressure forces induced violent fluctuations of the keyhole rear wall, resulting in an unstable keyhole and turbulent melt flow. A large drag force pushed the melt adjacent to the keyhole surface upward and accelerated the movement of the melt whose velocities reached 1 m/s or even higher, potentially inducing spatter. Increased heat input facilitated the occurrence of large droplets of spatter, which agreed with experimental observations captured by high-speed camera.

아연도금강의 부분용입 레이저 겹침용접에서 아연증기유도 스패터의 발생을 연구하기 위하여 용융풀과의 아연증기 상호작용을 고려한 3차원 열유체 수치모델을 개발하였습니다.

아연 증기 효과는 증기가 열쇠 구멍으로 폭발할 때 키홀 뒤쪽 벽에 작용하는 제트 압력력과 증기가 위쪽으로 빠져나갈 때 위쪽 키홀 벽에 작용하는 항력의 두 가지 힘으로 표시됩니다.

수치 모델은 예측된 열쇠 구멍 모양과 고속 X선 영상으로 관찰된 키홀 모양을 비교하여 보정하고 다양한 용접 일정에 적용했습니다.

이 연구는 큰 제트 압력이 키홀 뒷벽의 격렬한 변동을 유발하여 불안정한 열쇠 구멍과 난류 용융 흐름을 초래한다는 것을 보여주었습니다. 큰 항력은 키홀 표면에 인접한 용융물을 위로 밀어올리고 속도가 1m/s 이상에 도달한 용융물의 이동을 가속화하여 잠재적으로 스패터를 유발할 수 있습니다.

증가된 열 입력은 고속 카메라로 포착한 실험적 관찰과 일치하는 큰 방울의 스패터 발생을 촉진했습니다.

Fig. 1. Schematic of zero-gap laser welding of zinc-coated steel.
Fig. 1. Schematic of zero-gap laser welding of zinc-coated steel.
Fig. 2. Experimental setup for capturing a side view of the laser welding of zinc-coated steel enabled by use of high-temperature glass.
Fig. 2. Experimental setup for capturing a side view of the laser welding of zinc-coated steel enabled by use of high-temperature glass.
Fig. 3. Experimental angled top-view setup for laser welding of zinc-coated steel with a laser illumination.
Fig. 3. Experimental angled top-view setup for laser welding of zinc-coated steel with a laser illumination.
Fig. 4. Schematic of the rotating Gaussian body heat source.
Fig. 4. Schematic of the rotating Gaussian body heat source.
Fig. 5. Schematic of jet pressure force caused by zinc vapor: (a) locating the outlet of zinc vapor (point A), (b) schematic of assigning the jet pressure force.
Fig. 5. Schematic of jet pressure force caused by zinc vapor: (a) locating the outlet of zinc vapor (point A), (b) schematic of assigning the jet pressure force.
Fig. 6. Schematic of drag force caused by zinc vapor.
Fig. 6. Schematic of drag force caused by zinc vapor.
Fig. 7. Procedure for calculating the outgassing velocity of zinc vapor.
Fig. 7. Procedure for calculating the outgassing velocity of zinc vapor.
Fig. 8. Schematic related to calculating the zone of vaporized zinc.
Fig. 8. Schematic related to calculating the zone of vaporized zinc.
Fig. 9. The meshed domains for the thermal-fluid simulation of laser welding.
Fig. 9. The meshed domains for the thermal-fluid simulation of laser welding.
Fig. 10. The calculated temperature field and validation: (a) 3-D temperature field; (b)-(f) Comparison of experimental and simulated weld cross section: (b) P = 2000 W, v = 50 mm/s; (c) P = 2500 W, v = 50 mm/s; (d) P = 3000 W, v = 50 mm/s; (e) P = 3000 W, v = 60 mm/s; (f) P = 3000 W, v = 70 mm/s.
Fig. 10. The calculated temperature field and validation: (a) 3-D temperature field; (b)-(f) Comparison of experimental and simulated weld cross section: (b) P = 2000 W, v = 50 mm/s; (c) P = 2500 W, v = 50 mm/s; (d) P = 3000 W, v = 50 mm/s; (e) P = 3000 W, v = 60 mm/s; (f) P = 3000 W, v = 70 mm/s.
Fig. 11. Comparison of X-Ray images of in-process keyhole profiles and the numerical predictions: (a) Single sheet penetration (P = 480 W, v = 150 mm/s); (b) Two sheet penetration (P = 532 W, v = 150 mm/s).
Fig. 11. Comparison of X-Ray images of in-process keyhole profiles and the numerical predictions: (a) Single sheet penetration (P = 480 W, v = 150 mm/s); (b) Two sheet penetration (P = 532 W, v = 150 mm/s).
Fig. 12. High-speed images of dynamic keyhole in laser welding of steels: (a) without zinc coating (b) with zinc coating.
Fig. 12. High-speed images of dynamic keyhole in laser welding of steels: (a) without zinc coating (b) with zinc coating.
Fig. 13. Mass loss and molten pool observation under different laser power and welding velocity for 1.2 mm + 1.2 mm HDG 420LA stack-up
Fig. 13. Mass loss and molten pool observation under different laser power and welding velocity for 1.2 mm + 1.2 mm HDG 420LA stack-up
Fig. 14. Numerical results of keyhole and flow field in molten pool: (a) without zinc vapor forces, (b) with zinc vapor forces.
Fig. 14. Numerical results of keyhole and flow field in molten pool: (a) without zinc vapor forces, (b) with zinc vapor forces.
Fig. 18. Calculated velocity fields for different welding parameters: (a) P = 2 kW, v = 50 mm/s, (b) P = 2.5 kW, v = 50 mm/s, (c) P = 3 kW, v = 50 mm/s, (d) P = 3 kW, v = 60 mm/s, (e) P = 3 kW, v = 70 mm/s.
Fig. 18. Calculated velocity fields for different welding parameters: (a) P = 2 kW, v = 50 mm/s, (b) P = 2.5 kW, v = 50 mm/s, (c) P = 3 kW, v = 50 mm/s, (d) P = 3 kW, v = 60 mm/s, (e) P = 3 kW, v = 70 mm/s.
Fig. 19. Schematic of the generation of spatter in different sizes: (a) small size, (b) large size.
Fig. 19. Schematic of the generation of spatter in different sizes: (a) small size, (b) large size.

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Fluid Thermodynamic Simulation of Ti-6Al-4V Alloy in Laser Wire Deposition

Fluid Thermodynamic Simulation of Ti-6Al-4V Alloy in Laser Wire Deposition

Xiang WangLin-Jie ZhangJie Ning, and Suck-Joo Na
Published Online:8 Apr 2022https://doi.org/10.1089/3dp.2021.0159

Abstract

A 3D numerical model of heat transfer and fluid flow of molten pool in the process of laser wire deposition was presented by computational fluid dynamics technique. The simulation results of the deposition morphology were also compared with the experimental results under the condition of liquid bridge transfer mode. Moreover, they showed a good agreement. Considering the effect of recoil pressure, the morphology of the deposit metal obtained by the simulation was similar to the experiment result. Molten metal at the wire tip was peeled off and flowed into the molten pool, and then spread to both sides of the deposition layer under the recoil pressure. In addition, the results of simulation and high-speed charge-coupled device presented that a wedge transition zone, with a length of ∼6 mm, was formed behind the keyhole in the liquid bridge transfer process, where the height of deposited metal decreased gradually. After solidification, metal in the transition zone retained the original melt morphology, resulting in a decrease in the height of the tail of the deposition layer.

Keywords

LWD, CFD, liquid bridge transfer, fluid dynamics, wedge transition zone

Fluid Thermodynamic Simulation of Ti-6Al-4V Alloy in Laser Wire Deposition
Fluid Thermodynamic Simulation of Ti-6Al-4V Alloy in Laser Wire Deposition
Fluid Thermodynamic Simulation of Ti-6Al-4V Alloy in Laser Wire Deposition
Fluid Thermodynamic Simulation of Ti-6Al-4V Alloy in Laser Wire Deposition

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Figure 3.10: Snapshots of Temperature Profile for Single Track in Keyhole Regime (P = 250W and V = 0.5m/s) at the Preheating Temperature of 100 °C

Multiscale Process Modeling of Residual Deformation and Defect Formation for Laser Powder Bed Fusion Additive Manufacturing

Qian Chen, PhD
University of Pittsburgh, 2021

레이저 분말 베드 퓨전(L-PBF) 적층 제조(AM)는 우수한 기계적 특성으로 그물 모양에 가까운 복잡한 부품을 생산할 수 있습니다. 그러나 빌드 실패 및 다공성과 같은 결함으로 이어지는 원치 않는 잔류 응력 및 왜곡이 L-PBF의 광범위한 적용을 방해하고 있습니다.

L-PBF의 잠재력을 최대한 실현하기 위해 잔류 변형, 용융 풀 및 다공성 형성을 예측하는 다중 규모 모델링 방법론이 개발되었습니다. L-PBF의 잔류 변형 및 응력을 부품 규모에서 예측하기 위해 고유 변형 ​​방법을 기반으로 하는 다중 규모 프로세스 모델링 프레임워크가 제안됩니다.

고유한 변형 벡터는 마이크로 스케일에서 충실도가 높은 상세한 다층 프로세스 시뮬레이션에서 추출됩니다. 균일하지만 이방성인 변형은 잔류 왜곡 및 응력을 예측하기 위해 준 정적 평형 유한 요소 분석(FEA)에서 레이어별로 L-PBF 부품에 적용됩니다.

부품 규모에서의 잔류 변형 및 응력 예측 외에도 분말 규모의 다중물리 모델링을 수행하여 공정 매개변수, 예열 온도 및 스패터링 입자에 의해 유도된 용융 풀 변동 및 결함 형성을 연구합니다. 이러한 요인과 관련된 용융 풀 역학 및 다공성 형성 메커니즘은 시뮬레이션 및 실험을 통해 밝혀졌습니다.

제안된 부품 규모 잔류 응력 및 왜곡 모델을 기반으로 경로 계획 방법은 큰 잔류 변형 및 건물 파손을 방지하기 위해 주어진 형상에 대한 레이저 스캐닝 경로를 조정하기 위해 개발되었습니다.

연속 및 아일랜드 스캐닝 전략을 위한 기울기 기반 경로 계획이 공식화되고 공식화된 컴플라이언스 및 스트레스 최소화 문제에 대한 전체 감도 분석이 수행됩니다. 이 제안된 경로 계획 방법의 타당성과 효율성은 AconityONE L-PBF 시스템을 사용하여 실험적으로 입증되었습니다.

또한 기계 학습을 활용한 데이터 기반 프레임워크를 개발하여 L-PBF에 대한 부품 규모의 열 이력을 예측합니다. 본 연구에서는 실시간 열 이력 예측을 위해 CNN(Convolutional Neural Network)과 RNN(Recurrent Neural Network)을 포함하는 순차적 기계 학습 모델을 제안합니다.

유한 요소 해석과 비교하여 100배의 예측 속도 향상이 달성되어 실제 제작 프로세스보다 빠른 예측이 가능하고 실시간 온도 프로파일을 사용할 수 있습니다.

Laser powder bed fusion (L-PBF) additive manufacturing (AM) is capable of producing complex parts near net shape with good mechanical properties. However, undesired residual stress and distortion that lead to build failure and defects such as porosity are preventing broader applications of L-PBF. To realize the full potential of L-PBF, a multiscale modeling methodology is developed to predict residual deformation, melt pool, and porosity formation. To predict the residual deformation and stress in L-PBF at part-scale, a multiscale process modeling framework based on inherent strain method is proposed.

Inherent strain vectors are extracted from detailed multi-layer process simulation with high fidelity at micro-scale. Uniform but anisotropic strains are then applied to L-PBF part in a layer-by-layer fashion in a quasi-static equilibrium finite element analysis (FEA) to predict residual distortion and stress. Besides residual distortion and stress prediction at part scale, multiphysics modeling at powder scale is performed to study the melt pool variation and defect formation induced by process parameters, preheating temperature and spattering particles. Melt pool dynamics and porosity formation mechanisms associated with these factors are revealed through simulation and experiments.

Based on the proposed part-scale residual stress and distortion model, path planning method is developed to tailor the laser scanning path for a given geometry to prevent large residual deformation and building failures. Gradient based path planning for continuous and island scanning strategy is formulated and full sensitivity analysis for the formulated compliance- and stress-minimization problem is performed.

The feasibility and effectiveness of this proposed path planning method is demonstrated experimentally using the AconityONE L-PBF system. In addition, a data-driven framework utilizing machine learning is developed to predict the thermal history at part-scale for L-PBF.

In this work, a sequential machine learning model including convolutional neural network (CNN) and recurrent neural network (RNN), long shortterm memory unit, is proposed for real-time thermal history prediction. A 100x prediction speed improvement is achieved compared to the finite element analysis which makes the prediction faster than real fabrication process and real-time temperature profile available.

Figure 1.1: Schematic Overview of Metal Laser Powder Bed Fusion Process [2]
Figure 1.1: Schematic Overview of Metal Laser Powder Bed Fusion Process [2]
Figure 1.2: Commercial Powder Bed Fusion Systems
Figure 1.2: Commercial Powder Bed Fusion Systems
Figure 1.3: Commercial Metal Components Fabricated by Powder Bed Fusion Additive Manufacturing: (a) GE Fuel Nozzle; (b) Stryker Hip Biomedical Implant.
Figure 1.3: Commercial Metal Components Fabricated by Powder Bed Fusion Additive Manufacturing: (a) GE Fuel Nozzle; (b) Stryker Hip Biomedical Implant.
Figure 2.1: Proposed Multiscale Process Simulation Framework
Figure 2.1: Proposed Multiscale Process Simulation Framework
Figure 2.2: (a) Experimental Setup for In-situ Thermocouple Measurement in the EOS M290 Build Chamber; (b) Themocouple Locations on the Bottom Side of the Substrate.
Figure 2.2: (a) Experimental Setup for In-situ Thermocouple Measurement in the EOS M290 Build Chamber; (b) Themocouple Locations on the Bottom Side of the Substrate.
Figure 2.3: (a) Finite Element Model for Single Layer Thermal Analysis; (b) Deposition Layer
Figure 2.3: (a) Finite Element Model for Single Layer Thermal Analysis; (b) Deposition Layer
Figure 2.4: Core-skin layer: (a) Surface Morphology; (b) Scanning Strategy; (c) Transient Temperature Distribution and Temperature History at (d) Point 1; (e) Point 2 and (f) Point 3
Figure 2.4: Core-skin layer: (a) Surface Morphology; (b) Scanning Strategy; (c) Transient Temperature Distribution and Temperature History at (d) Point 1; (e) Point 2 and (f) Point 3
Figure 2.5: (a) Scanning Orientation of Each Layer; (b) Finite Element Model for Micro-scale Representative Volume
Figure 2.5: (a) Scanning Orientation of Each Layer; (b) Finite Element Model for Micro-scale Representative Volume
Figure 2.6: Bottom Layer (a) Thermal History; (b) Plastic Strain and (c) Elastic Strain Evolution History
Figure 2.6: Bottom Layer (a) Thermal History; (b) Plastic Strain and (c) Elastic Strain Evolution History
Figure 2.7: Bottom Layer Inherent Strain under Default Process Parameters along Horizontal Scanning Path
Figure 2.7: Bottom Layer Inherent Strain under Default Process Parameters along Horizontal Scanning Path
Figure 2.8: Snapshots of the Element Activation Process
Figure 2.8: Snapshots of the Element Activation Process
Figure 2.9: Double Cantilever Beam Structure Built by the EOS M290 DMLM Process (a) Before and (b) After Cutting off; (c) Faro Laser ScanArm V3 for Distortion Measurement
Figure 2.9: Double Cantilever Beam Structure Built by the EOS M290 DMLM Process (a) Before and (b) After Cutting off; (c) Faro Laser ScanArm V3 for Distortion Measurement
Figure 2.10: Square Canonical Structure Built by the EOS M290 DMLM Process
Figure 2.10: Square Canonical Structure Built by the EOS M290 DMLM Process
Figure 2.11: Finite Element Mesh for the Square Canonical and Snapshots of Element Activation Process
Figure 2.11: Finite Element Mesh for the Square Canonical and Snapshots of Element Activation Process
Figure 2.12: Simulated Distortion Field for the Double Cantilever Beam before Cutting off the Supports: (a) Inherent Strain Method; (b) Simufact Additive 3.1
Figure 2.12: Simulated Distortion Field for the Double Cantilever Beam before Cutting off the Supports: (a) Inherent Strain Method; (b) Simufact Additive 3.1
Figure 3.10: Snapshots of Temperature Profile for Single Track in Keyhole Regime (P = 250W and V = 0.5m/s) at the Preheating Temperature of 100 °C
Figure 3.10: Snapshots of Temperature Profile for Single Track in Keyhole Regime (P = 250W and V = 0.5m/s) at the Preheating Temperature of 100 °C
s) at the Preheating Temperature of 500 °C
s) at the Preheating Temperature of 500 °C
Figure 3.15: Melt Pool Cross Section Comparison Between Simulation and Experiment for Single Track
Figure 3.15: Melt Pool Cross Section Comparison Between Simulation and Experiment for Single Track

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Forming characteristics and control method of weld bead for GMAW on curved surface

곡면에 GMAW용 용접 비드의 형성 특성 및 제어 방법

Forming characteristics and control method of weld bead for GMAW on curved surface

The International Journal of Advanced Manufacturing Technology (2021)Cite this article

Abstract

곡면에서 GMAW 기반 적층 가공의 용접 성형 특성은 중력의 영향을 크게 받습니다. 성형면의 경사각이 크면 혹 비드(hump bead)와 같은 심각한 결함이 발생합니다.

본 논문에서는 양생면에서 용접 비드 형성의 형성 특성과 제어 방법을 연구하기 위해 용접 용융 풀 유동 역학의 전산 모델을 수립하고 제안된 모델을 검증하기 위해 증착 실험을 수행하였습니다.

결과는 용접 비드 경사각(α)이 증가함에 따라 역류의 속도가 증가하고 상향 용접의 경우 α > 60°일 때 불규칙한 험프 결함이 나타나는 것으로 나타났습니다.

상부 과잉 액체의 하향 압착력과 하부 상향 유동의 반동력과 표면장력 사이의 상호작용은 용접 혹 형성의 주요 요인이었다. 하향 용접의 경우 양호한 형태를 얻을 수 있었으며, 용접 비드 경사각이 증가함에 따라 용접 높이는 감소하고 용접 폭은 증가하였습니다.

하향 및 상향 용접을 위한 곡면의 용융 거동 및 성형 특성을 기반으로 험프 결함을 제어하기 위해 위브 용접을 통한 증착 방법을 제안하였습니다.

성형 궤적의 변화로 인해 용접 방향의 중력 성분이 크게 감소하여 용융 풀 흐름의 안정성이 향상되었으며 복잡한 표면에서 안정적이고 일관된 용접 비드를 얻는 데 유리했습니다.

하향 용접과 상향 용접 사이의 단일 비드의 치수 편차는 7% 이내였으며 하향 및 상향 혼합 혼합 비드 중첩 증착에서 비드의 변동 편차는 0.45로 GMAW 기반 적층 제조 공정에서 허용될 수 있었습니다.

이러한 발견은 GMAW를 기반으로 하는 곡선 적층 적층 제조의 용접 비드 형성 제어에 기여했습니다.

The weld forming characteristics of GMAW-based additive manufacturing on curved surface are dramatically influenced by gravity. Large inclined angle of the forming surface would lead to severe defects such as hump bead. In this paper, a computational model of welding molten pool flow dynamics was established to research the forming characteristic and control method of weld bead forming on cured surface, and deposition experiments were conducted to verify the proposed model. Results indicated that the velocity of backward flows increased with the increase of weld bead tilt angle (α) and irregular hump defects appeared when α > 60° for upward welding. The interaction between the downward squeezing force of the excess liquid at the top and the recoil force of the upward flow at the bottom and the surface tension were primary factors for welding hump formation. For downward welding, a good morphology shape could be obtained, and the weld height decreased and the weld width increased with the increase of weld bead tilt angle. Based on the molten behaviors and forming characteristics on curved surface for downward and upward welding, the method of deposition with weave welding was proposed to control hump defects. Gravity component in the welding direction was significantly reduced due to the change of forming trajectory, which improved the stability of the molten pool flow and was beneficial to obtain stable and consistent weld bead on complex surface. The dimensional deviations of the single bead between downward and upward welding were within 7% and the fluctuation deviation of the bead in multi-bead overlapping deposition with mixing downward and upward welding was 0.45, which could be acceptable in GMAW-based additive manufacturing process. These findings contributed to the weld bead forming control of curve layered additive manufacturing based on GMAW.

Keywords

  • Molten pool behaviors
  • GMAW-based WAAM
  • Deposition with weave welding
  • Welding on curved surface
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Figure 2. (a) Scanning electron microscopy images of Ti6Al4V powder particles and (b) simulated powder bed using discrete element modelling

Laser Powder Bed에서 Laser Drilling에 의한 Keyhole 형성 Ti6Al4V 생체 의학 합금의 융합: 메조스코픽 전산유체역학 시뮬레이션 대 경험적 검증을 사용한 수학적 모델링

Keyhole Formation by Laser Drilling in Laser Powder Bed Fusion of Ti6Al4V Biomedical Alloy: Mesoscopic Computational Fluid Dynamics Simulation versus Mathematical Modelling Using Empirical Validation

Asif Ur Rehman 1,2,3,*
,† , Muhammad Arif Mahmood 4,*
,† , Fatih Pitir 1
, Metin Uymaz Salamci 2,3
,
Andrei C. Popescu 4 and Ion N. Mihailescu 4

Abstract

LPBF(Laser Powder Bed fusion) 공정에서 작동 조건은 열 분포를 기반으로 레이저 유도 키홀 영역을 결정하는 데 필수적입니다. 얕은 구멍과 깊은 구멍으로 분류되는 이러한 영역은 LPBF 프로세스에서 확률과 결함 형성 강도를 제어합니다.

LPBF 프로세스의 핵심 구멍을 연구하고 제어하기 위해 수학적 및 CFD(전산 유체 역학) 모델이 제공됩니다. CFD의 경우 이산 요소 모델링 기법을 사용한 유체 체적 방법이 사용되었으며, 분말 베드 보이드 및 표면에 의한 레이저 빔 흡수를 포함하여 수학적 모델이 개발되었습니다.

동적 용융 풀 거동을 자세히 살펴봅니다. 실험적, CFD 시뮬레이션 및 분석적 컴퓨팅 결과 간에 정량적 비교가 수행되어 좋은 일치를 얻습니다.

LPBF에서 레이저 조사 영역 주변의 온도는 높은 내열성과 분말 입자 사이의 공기로 인해 분말층 주변에 비해 급격히 상승하여 레이저 횡방향 열파의 이동이 느려집니다. LPBF에서 키홀은 에너지 밀도에 의해 제어되는 얕고 깊은 키홀 모드로 분류될 수 있습니다. 에너지 밀도를 높이면 얕은 키홀 구멍 모드가 깊은 키홀 구멍 모드로 바뀝니다.

깊은 키홀 구멍의 에너지 밀도는 다중 반사와 키홀 구멍 내의 2차 반사 빔의 집중으로 인해 더 높아져 재료가 빠르게 기화됩니다.

깊은 키홀 구멍 모드에서는 온도 분포가 높기 때문에 액체 재료가 기화 온도에 가까우므로 얕은 키홀 구멍보다 구멍이 형성될 확률이 훨씬 높습니다. 온도가 급격히 상승하면 재료 밀도가 급격히 떨어지므로 비열과 융해 잠열로 인해 유체 부피가 증가합니다.

그 대가로 표면 장력을 낮추고 용융 풀 균일성에 영향을 미칩니다.

In the laser powder bed fusion (LPBF) process, the operating conditions are essential in determining laser-induced keyhole regimes based on the thermal distribution. These regimes, classified into shallow and deep keyholes, control the probability and defects formation intensity in the LPBF process. To study and control the keyhole in the LPBF process, mathematical and computational fluid dynamics (CFD) models are presented. For CFD, the volume of fluid method with the discrete element modeling technique was used, while a mathematical model was developed by including the laser beam absorption by the powder bed voids and surface. The dynamic melt pool behavior is explored in detail. Quantitative comparisons are made among experimental, CFD simulation and analytical computing results leading to a good correspondence. In LPBF, the temperature around the laser irradiation zone rises rapidly compared to the surroundings in the powder layer due to the high thermal resistance and the air between the powder particles, resulting in a slow travel of laser transverse heat waves. In LPBF, the keyhole can be classified into shallow and deep keyhole mode, controlled by the energy density. Increasing the energy density, the shallow keyhole mode transforms into the deep keyhole mode. The energy density in a deep keyhole is higher due to the multiple reflections and concentrations of secondary reflected beams within the keyhole, causing the material to vaporize quickly. Due to an elevated temperature distribution in deep keyhole mode, the probability of pores forming is much higher than in a shallow keyhole as the liquid material is close to the vaporization temperature. When the temperature increases rapidly, the material density drops quickly, thus, raising the fluid volume due to the specific heat and fusion latent heat. In return, this lowers the surface tension and affects the melt pool uniformity.

Keywords: laser powder bed fusion; computational fluid dynamics; analytical modelling; shallow
and deep keyhole modes; experimental correlation

Figure 1. Powder bed schematic with voids.
Figure 1. Powder bed schematic with voids.
Figure 2. (a) Scanning electron microscopy images of Ti6Al4V powder particles and (b) simulated powder bed using discrete element modelling
Figure 2. (a) Scanning electron microscopy images of Ti6Al4V powder particles and (b) simulated powder bed using discrete element modelling
Figure 3. Temperature field contour formation at various time intervals (a) 0.695 ms, (b) 0.795 ms, (c) 0.995 ms and (d) 1.3 ms.
Figure 3. Temperature field contour formation at various time intervals (a) 0.695 ms, (b) 0.795 ms, (c) 0.995 ms and (d) 1.3 ms.
Figure 4. Detailed view of shallow depth melt mode with temperature field at 0.695 ms
Figure 4. Detailed view of shallow depth melt mode with temperature field at 0.695 ms
Figure 5. Melt flow stream traces formation at various time intervals (a) 0.695 ms, (b) 0.795 ms, (c) 0.995 ms and (d) 1.3 ms
Figure 5. Melt flow stream traces formation at various time intervals (a) 0.695 ms, (b) 0.795 ms, (c) 0.995 ms and (d) 1.3 ms
Figure 6. Density evolution of the melt pool at various time intervals (a) 0.695 ms, (b) 0.795 ms, (c) 0.995 ms and (d) 1.3 ms.
Figure 6. Density evolution of the melt pool at various time intervals (a) 0.695 ms, (b) 0.795 ms, (c) 0.995 ms and (d) 1.3 ms.
Figure 7. Un-melted and melted regions at different time intervals (a) 0.695 ms, (b) 0.795 ms, (c) 0.995 ms and (d) 1.3 ms
Figure 7. Un-melted and melted regions at different time intervals (a) 0.695 ms, (b) 0.795 ms, (c) 0.995 ms and (d) 1.3 ms
Figure 8. Transformation from shallow depth melt flow to deep keyhole formation when laser power increased from (a) 170 W to (b) 200 W
Figure 8. Transformation from shallow depth melt flow to deep keyhole formation when laser power increased from (a) 170 W to (b) 200 W
Figure 9. Stream traces and laser beam multiple reflections in deep keyhole melt flow mode
Figure 9. Stream traces and laser beam multiple reflections in deep keyhole melt flow mode
Figure 10. A comparison between analytical and CFD simulation results for peak thermal distribution value in the deep keyhole formation
Figure 10. A comparison between analytical and CFD simulation results for peak thermal distribution value in the deep keyhole formation
Figure 11. A comparison among experiments [49], CFD and analytical simulations for deep keyhole top width and bottom width
Figure 11. A comparison among experiments [49], CFD and analytical simulations for deep keyhole top width and bottom width

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Figures-Effects of sinusoidal oscillating laser beam on weld formation, melt flow and grain structure during aluminum alloys lap welding

알루미늄 합금 겹침 용접 중 용접 형성, 용융 흐름 및 입자 구조에 대한 사인파 발진 레이저 빔의 영향

Effects of sinusoidal oscillating laser beam on weld formation, melt flow and grain structure during aluminum alloys lap welding

Lin Chen, Gaoyang Mi, Xiong Zhang, Chunming Wang
School of Materials Science and Engineering, Huazhong University of Science and Technology, Wuhan, 430074, China

Abstract

레이저 사인파 진동(사인) 용접 및 레이저 용접(SLW)에서 1.5mm 6061/5182 알루미늄 합금 박판 랩 조인트의 수치 모델이 온도 분포와 용융 흐름을 시뮬레이션하기 위해 개발되었습니다.

SLW의 일반적인 에너지 분포와 달리 레이저 빔의 사인파 진동은 에너지 분포를 크게 균질화하고 에너지 피크를 줄였습니다. 에너지 피크는 사인 용접의 양쪽에 위치하여 톱니 모양의 단면이 형성되었습니다. 이 논문은 시뮬레이션을 통해 응고 미세구조에 대한 온도 구배(G)와 응고 속도(R)의 영향을 설명했습니다.

결과는 사인 용접의 중심이 낮은 G/R로 더 넓은 영역을 가짐으로써 더 넓은 등축 결정립 영역의 형성을 촉진하고 더 큰 GR로 인해 주상 결정립이 더 가늘다는 것을 나타냅니다. 다공성 및 비관통 용접은 레이저 사인파 진동에 의해 얻어졌습니다.

그 이유는 용융 풀의 부피가 확대되고 열쇠 구멍의 부피 비율이 감소하며 용융 풀의 난류가 완만해졌기 때문이며, 이는 용융 흐름의 고속 이미징 및 시뮬레이션 결과에서 관찰되었습니다. 두 용접부의 인장시험에서 융착선을 따라 인장파괴 형태를 보였고 사인 용접부의 인장강도가 SLW 용접부보다 유의하게 우수하였습니다.

이는 등축 결정립 영역이 넓을수록 균열 경향이 감소하고 파단 위치에 근접한 입자 크기가 미세하기 때문입니다. 결함이 없고 우수한 용접은 신에너지 자동차 산업에 매우 중요합니다.

A numerical model of 1.5 mm 6061/5182 aluminum alloys thin sheets lap joints under laser sinusoidal oscillation (sine) welding and laser welding (SLW) weld was developed to simulate temperature distribution and melt flow. Unlike the common energy distribution of SLW, the sinusoidal oscillation of laser beam greatly homogenized the energy distribution and reduced the energy peak. The energy peaks were located at both sides of the sine weld, resulting in the tooth-shaped sectional formation. This paper illustrated the effect of the temperature gradient (G) and solidification rate (R) on the solidification microstructure by simulation. Results indicated that the center of the sine weld had a wider area with low G/R, promoting the formation of a wider equiaxed grain zone, and the columnar grains were slenderer because of greater GR. The porosity-free and non-penetration welds were obtained by the laser sinusoidal oscillation. The reasons were that the molten pool volume was enlarged, the volume proportion of keyhole was reduced and the turbulence in the molten pool was gentled, which was observed by the high-speed imaging and simulation results of melt flow. The tensile test of both welds showed a tensile fracture form along the fusion line, and the tensile strength of sine weld was significantly better than that of the SLW weld. This was because that the wider equiaxed grain area reduced the tendency of cracks and the finer grain size close to the fracture location. Defect-free and excellent welds are of great significance to the new energy vehicles industry.

Keywords

Laser weldingSinusoidal oscillatingEnergy distributionNumerical simulationMolten pool flowGrain structure

Figures-Effects of sinusoidal oscillating laser beam on weld formation, melt flow and grain structure during aluminum alloys lap welding
Figures-Effects of sinusoidal oscillating laser beam on weld formation, melt flow and grain structure during aluminum alloys lap welding
Fig. 1. Schematic of (a) geometry of the simulation model, (b) A-A cross-section presenting the locations of point probes for recording temperature history (unit: µm).

Laser powder bed fusion of 17-4 PH stainless steel: a comparative study on the effect of heat treatment on the microstructure evolution and mechanical properties

17-4 PH 스테인리스강의 레이저 분말 베드 융합: 열처리가 미세조직의 진화 및 기계적 특성에 미치는 영향에 대한 비교 연구

panelS.Saboonia, A.Chaboka, S.Fenga,e, H.Blaauwb, T.C.Pijperb,c, H.J.Yangd, Y.T.Peia
aDepartment of Advanced Production Engineering, Engineering and Technology Institute Groningen, University of Groningen, Nijenborgh 4, 9747 AG, Groningen, The Netherlands
bPhilips Personal Care, Oliemolenstraat 5, 9203 ZN, Drachten, The Netherlands
cInnovation Cluster Drachten, Nipkowlaan 5, 9207 JA, Drachten, The Netherlands
dShi-changxu Innovation Center for Advanced Materials, Institute of Metal Research, Chinese Academy of Sciences, 72 Wenhua Road, Shenyang 110016, P. R. China
eSchool of Mechanical Engineering, University of Science and Technology Beijing, Beijing, 100083, P.R. China

Abstract

17-4 PH (precipitation hardening) stainless steel is commonly used for the fabrication of complicated molds with conformal cooling channels using laser powder bed fusion process (L-PBF). However, their microstructure in the as-printed condition varies notably with the chemical composition of the feedstock powder, resulting in different age-hardening behavior. In the present investigation, 17-4 PH stainless steel components were fabricated by L-PBF from two different feedstock powders, and subsequently subjected to different combinations of post-process heat treatments. It was observed that the microstructure in as-printed conditions could be almost fully martensitic or ferritic, depending on the ratio of Creq/Nieq of the feedstock powder. Aging treatment at 480 °C improved the yield and ultimate tensile strengths of the as-printed components. However, specimens with martensitic structures exhibited accelerated age-hardening response compared with the ferritic specimens due to the higher lattice distortion and dislocation accumulation, resulting in the “dislocation pipe diffusion mechanism”. It was also found that the martensitic structures were highly susceptible to the formation of reverted austenite during direct aging treatment, where 19.5% of austenite phase appeared in the microstructure after 15 h of direct aging. Higher fractions of reverted austenite activates the transformation induced plasticity and improves the ductility of heat treated specimens. The results of the present study can be used to tailor the microstructure of the L-PBF printed 17-4 PH stainless steel by post-process heat treatments to achieve a good combination of mechanical properties.

17-4 PH(석출 경화) 스테인리스강은 레이저 분말 베드 융합 공정(L-PBF)을 사용하여 등각 냉각 채널이 있는 복잡한 금형 제작에 일반적으로 사용됩니다. 그러나 인쇄된 상태의 미세 구조는 공급원료 분말의 화학적 조성에 따라 크게 달라지므로 시효 경화 거동이 다릅니다.

현재 조사에서 17-4 PH 스테인리스강 구성요소는 L-PBF에 의해 두 가지 다른 공급원료 분말로 제조되었으며, 이후에 다양한 조합의 후처리 열처리를 거쳤습니다. 인쇄된 상태의 미세구조는 공급원료 분말의 Creq/Nieq 비율에 따라 거의 완전히 마르텐사이트 또는 페라이트인 것으로 관찰되었습니다.

480 °C에서 노화 처리는 인쇄된 구성 요소의 수율과 극한 인장 강도를 개선했습니다. 그러나 마텐자이트 구조의 시편은 격자 변형 및 전위 축적이 높아 페라이트 시편에 비해 시효 경화 반응이 가속화되어 “전위 파이프 확산 메커니즘”이 발생합니다.

또한 마르텐사이트 구조는 직접 시효 처리 중에 복귀된 오스테나이트의 형성에 매우 민감한 것으로 밝혀졌으며, 여기서 15시간의 직접 시효 후 미세 조직에 19.5%의 오스테나이트 상이 나타났습니다.

복귀된 오스테나이트의 비율이 높을수록 변형 유도 가소성이 활성화되고 열처리된 시편의 연성이 향상됩니다. 본 연구의 결과는 기계적 특성의 우수한 조합을 달성하기 위해 후처리 열처리를 통해 L-PBF로 인쇄된 17-4 PH 스테인리스강의 미세 구조를 조정하는 데 사용할 수 있습니다.

Keywords

Laser powder bed fusion17-4 PH stainless steelPost-process heat treatmentAge hardeningReverted austenite

Fig. 1. Schematic of (a) geometry of the simulation model, (b) A-A cross-section presenting the locations of point probes for recording temperature history (unit: µm).
Fig. 1. Schematic of (a) geometry of the simulation model, (b) A-A cross-section presenting the locations of point probes for recording temperature history (unit: µm).
Fig. 2. Optical (a, b) and TEM (c) micrographs of the wrought 17-4 PH stainless steel.
Fig. 2. Optical (a, b) and TEM (c) micrographs of the wrought 17-4 PH stainless steel.
Fig. 3. EBSD micrographs of the as-printed 17-4 PH steel fabricated with “powder A” (a, b) and “powder B” (c, d) on two different cross sections: (a, c) perpendicular to the building direction, and (b, d) parallel to the building direction.
Fig. 3. EBSD micrographs of the as-printed 17-4 PH steel fabricated with “powder A” (a, b) and “powder B” (c, d) on two different cross sections: (a, c) perpendicular to the building direction, and (b, d) parallel to the building direction.
Fig. 4. Microstructure of the as-printed 17-4 PH stainless steel fabricated with “powder A” (a) and “powder B” (b).
Fig. 4. Microstructure of the as-printed 17-4 PH stainless steel fabricated with “powder A” (a) and “powder B” (b).
Fig. 5. Simulated temperature history of the probes located at the cross section of the L-PBF 17-4 PH steel sample.
Fig. 5. Simulated temperature history of the probes located at the cross section of the L-PBF 17-4 PH steel sample.
Fig. 6. Dependency of the volume fraction of delta ferrite in the final microstructure of L-PBF printed 17-4 PH steel as a function of Creq/Nieq.
Fig. 6. Dependency of the volume fraction of delta ferrite in the final microstructure of L-PBF printed 17-4 PH steel as a function of Creq/Nieq.
Fig. 7. IQ + IPF (left column), parent austenite grain maps (middle column) and phase maps (right column, green color = martensite, red color = austenite) of the post-process heat treated 17-4 PH stainless steel: (a-c) direct aged, (d-f) HIP + aging, (g-i) SA + Aging, and (j-l) HIP + SA + aging (all sample were printed with “powder A”).
Fig. 7. IQ + IPF (left column), parent austenite grain maps (middle column) and phase maps (right column, green color = martensite, red color = austenite) of the post-process heat treated 17-4 PH stainless steel: (a-c) direct aged, (d-f) HIP + aging, (g-i) SA + Aging, and (j-l) HIP + SA + aging (all sample were printed with “powder A”).
Fig. 8. TEM micrographs of the post process heat treated 17-4 PH stainless steel: (a) direct aging and (b) HIP + aging (printed with “powder A”).
Fig. 8. TEM micrographs of the post process heat treated 17-4 PH stainless steel: (a) direct aging and (b) HIP + aging (printed with “powder A”).
Fig. 9. XRD patterns of the post-process heat treated 17-4 PH stainless steel printed with “powder A”.
Fig. 9. XRD patterns of the post-process heat treated 17-4 PH stainless steel printed with “powder A”.
Fig. 10. (a) Volume fraction of reverted austenite as a function of aging time for “direct aging” condition, (b) phase map (green color = martensite, red color = austenite) of the 15 h direct aged specimen printed with “powder A”.
Fig. 10. (a) Volume fraction of reverted austenite as a function of aging time for “direct aging” condition, (b) phase map (green color = martensite, red color = austenite) of the 15 h direct aged specimen printed with “powder A”.
Fig. 11. Microhardness variations of the “direct aged” specimens as a function of aging time at 480 °C.
Fig. 11. Microhardness variations of the “direct aged” specimens as a function of aging time at 480 °C.
Fig. 12. Kernel average misorientation graphs of the as-printed 17-4 PH steel with (a) martensitic structure (printed with “powder A”) and (b) ferritic structure (printed with “powder b”).
Fig. 12. Kernel average misorientation graphs of the as-printed 17-4 PH steel with (a) martensitic structure (printed with “powder A”) and (b) ferritic structure (printed with “powder b”).
Fig. 13. Typical stress-strain curves (a) along with the yield and ultimate tensile strengths (b) and elongation (c) of the as-printed and post-process heat treated 17-4 PH stainless steel (all sample are fabricated with “powder A”).
Fig. 13. Typical stress-strain curves (a) along with the yield and ultimate tensile strengths (b) and elongation (c) of the as-printed and post-process heat treated 17-4 PH stainless steel (all sample are fabricated with “powder A”).
Fig. 14. (a) IQ + IPF and (b) phase map (green color = martensite, red color = austenite) of the “direct aged” specimen after tensile test at a location nearby the rupture point (tension direction from left to right).
Fig. 14. (a) IQ + IPF and (b) phase map (green color = martensite, red color = austenite) of the “direct aged” specimen after tensile test at a location nearby the rupture point (tension direction from left to right).

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electromagnetic metal casting computation designs Fig1

A survey of electromagnetic metal casting computation designs, present approaches, future possibilities, and practical issues

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Abstract

Electromagnetic metal casting (EMC) is a casting technique that uses electromagnetic energy to heat metal powders. It is a faster, cleaner, and less time-consuming operation. Solid metals create issues in electromagnetics since they reflect the electromagnetic radiation rather than consume it—electromagnetic energy processing results in sounded pieces with higher-ranking material properties and a more excellent microstructure solution. For the physical production of the electromagnetic casting process, knowledge of electromagnetic material interaction is critical. Even where the heated material is an excellent electromagnetic absorber, the total heating quality is sometimes insufficient. Numerical modelling works on finding the proper coupled effects between properties to bring out the most effective operation. The main parameters influencing the quality of output of the EMC process are: power dissipated per unit volume into the material, penetration depth of electromagnetics, complex magnetic permeability and complex dielectric permittivity. The contact mechanism and interference pattern also, in turn, determines the quality of the process. Only a few parameters, such as the environment’s temperature, the interference pattern, and the rate of metal solidification, can be controlled by AI models. Neural networks are used to achieve exact outcomes by stimulating the neurons in the human brain. Additive manufacturing (AM) is used to design mold and cores for metal casting. The models outperformed the traditional DFA optimization approach, which is susceptible to local minima. The system works only offline, so real-time analysis and corrections are not yet possible.

Korea Abstract

전자기 금속 주조 (EMC)는 전자기 에너지를 사용하여 금속 분말을 가열하는 주조 기술입니다. 더 빠르고 깨끗하며 시간이 덜 소요되는 작업입니다.

고체 금속은 전자기 복사를 소비하는 대신 반사하기 때문에 전자기학에서 문제를 일으킵니다. 전자기 에너지 처리는 더 높은 등급의 재료 특성과 더 우수한 미세 구조 솔루션을 가진 사운드 조각을 만듭니다.

전자기 주조 공정의 물리적 생산을 위해서는 전자기 물질 상호 작용에 대한 지식이 중요합니다. 가열된 물질이 우수한 전자기 흡수재인 경우에도 전체 가열 품질이 때때로 불충분합니다. 수치 모델링은 가장 효과적인 작업을 이끌어 내기 위해 속성 간의 적절한 결합 효과를 찾는데 사용됩니다.

EMC 공정의 출력 품질에 영향을 미치는 주요 매개 변수는 단위 부피당 재료로 분산되는 전력, 전자기의 침투 깊이, 복합 자기 투과성 및 복합 유전율입니다. 접촉 메커니즘과 간섭 패턴 또한 공정의 품질을 결정합니다. 환경 온도, 간섭 패턴 및 금속 응고 속도와 같은 몇 가지 매개 변수 만 AI 모델로 제어 할 수 있습니다.

신경망은 인간 뇌의 뉴런을 자극하여 정확한 결과를 얻기 위해 사용됩니다. 적층 제조 (AM)는 금속 주조용 몰드 및 코어를 설계하는 데 사용됩니다. 모델은 로컬 최소값에 영향을 받기 쉬운 기존 DFA 최적화 접근 방식을 능가했습니다. 이 시스템은 오프라인에서만 작동하므로 실시간 분석 및 수정은 아직 불가능합니다.

electromagnetic metal casting computation designs Fig1
electromagnetic metal casting computation designs Fig1
electromagnetic metal casting computation designs Fig2
electromagnetic metal casting computation designs Fig2
electromagnetic metal casting computation designs Fig3
electromagnetic metal casting computation designs Fig3
electromagnetic metal casting computation designs Fig4
electromagnetic metal casting computation designs Fig4
electromagnetic metal casting computation designs Fig5
electromagnetic metal casting computation designs Fig5
electromagnetic metal casting computation designs Fig6
electromagnetic metal casting computation designs Fig6
electromagnetic metal casting computation designs Fig7
electromagnetic metal casting computation designs Fig7
electromagnetic metal casting computation designs Fig8
electromagnetic metal casting computation designs Fig8
electromagnetic metal casting computation designs Fig9
electromagnetic metal casting computation designs Fig9

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Fig. 1. Schematic description of the laser welding process considered in this study.

Analysis of molten pool dynamics in laser welding with beam oscillation and filler wire feeding

Won-Ik Cho, Peer Woizeschke
Bremer Institut für angewandte Strahltechnik GmbH, Klagenfurter Straße 5, Bremen 28359, Germany

Received 30 July 2020, Revised 3 October 2020, Accepted 18 October 2020, Available online 1 November 2020.

Abstract

Molten pool flow and heat transfer in a laser welding process using beam oscillation and filler wire feeding were calculated using computational fluid dynamics (CFD). There are various indirect methods used to analyze the molten pool dynamics in fusion welding. In this work, based on the simulation results, the surface fluctuation was directly measured to enable a more intuitive analysis, and then the signal was analyzed using the Fourier transform and wavelet transform in terms of the beam oscillation frequency and buttonhole formation. The 1st frequency (2 x beam oscillation frequency, the so-called chopping frequency), 2nd frequency (4 x beam oscillation frequency), and beam oscillation frequency components were the main components found. The 1st and 2nd frequency components were caused by the effect of the chopping process and lumped line energy. The beam oscillation frequency component was related to rapid, unstable molten pool behavior. The wavelet transform effectively analyzed the rapid behaviors based on the change of the frequency components over time.

Korea Abstract

빔 진동 및 필러 와이어 공급을 사용하는 레이저 용접 공정에서 용융 풀 흐름 및 열 전달은 CFD (전산 유체 역학)를 사용하여 계산되었습니다. 용융 용접에서 용융 풀 역학을 분석하는 데 사용되는 다양한 간접 방법이 있습니다.

본 연구에서는 시뮬레이션 결과를 바탕으로 보다 직관적 인 분석이 가능하도록 표면 변동을 직접 측정 한 후 빔 발진 주파수 및 버튼 홀 형성 측면에서 푸리에 변환 및 웨이블릿 변환을 사용하여 신호를 분석했습니다.

1 차 주파수 (2 x 빔 발진 주파수, 이른바 초핑 주파수), 2 차 주파수 (4 x 빔 발진 주파수) 및 빔 발진 주파수 성분이 발견 된 주요 구성 요소였습니다. 1 차 및 2 차 주파수 성분은 쵸핑 공정과 집중 라인 에너지의 영향으로 인해 발생했습니다.

빔 진동 주파수 성분은 빠르고 불안정한 용융 풀 동작과 관련이 있습니다. 웨이블릿 변환은 시간 경과에 따른 주파수 구성 요소의 변화를 기반으로 빠른 동작을 효과적으로 분석했습니다.

1 . 소개

융합 용접에서 용융 풀 역학은 용접 결함과 시각적 이음새 품질에 직접적인 영향을 미칩니다. 이러한 역학을 연구하기 위해 고속 카메라를 사용하는 직접 방법과 광학 또는 음향 신호를 사용하는 간접 방법과 같은 다양한 측정 방법을 사용하여 여러 실험 방법을 고려했습니다. 시간 도메인의 원래 신호는 특별히 주파수 도메인에서 변환 된 신호로 변환되어 용융 풀 동작에 영향을 미치는 주파수 성분을 분석합니다. Kotecki et al. (1972)는 고속 카메라를 사용하여 가스 텅스텐 아크 용접에서 용융 풀을 관찰했습니다. [1]. 그들은 120Hz 리플 DC 출력을 가진 용접 전원을 사용할 때 용융 풀 진동 주파수가 120Hz임을 보여주었습니다. 전원을 끈 후 진동 주파수는 용융 풀의 고유 주파수를 나타내는 용융 풀 크기와 관련이 있습니다. 진동은 응고 중에 용접 표면 스케일링을 생성했습니다. Zacksenhouse and Hardt (1983)는 레이저 섀도 잉 동작 측정 기술을 사용하여 가스 텅스텐 아크 용접에서 완전히 관통 된 용융 풀의 동작을 측정했습니다 [2] . 그들은 2.5mm 두께의 강판에서 6mm 풀 반경 (고정 용접)에 대해 용융 풀의 고유 주파수가 18.9Hz라는 것을 발견했습니다. Semak et al. (1995) 고속 카메라를 사용하여 레이저 스폿 용접에서 용융 풀 및 키홀 역학 조사 [3]. 그들은 깊이가 약 3mm이고 반경이 약 3mm 인 용융 풀에서 200Hz의 낮은 체적 진동 주파수를 관찰했습니다. 0.45mm Aendenroomer와 den Ouden (1998)은 강철의 펄스 가스 텅스텐 아크 용접에서 용융 풀 진동을보고했습니다 [4] . 그들은 침투 깊이에 따라 진동 모드 변화를 보였고 주파수는 50Hz에서 150Hz 사이에서 변화했습니다. 주파수는 완전히 침투 된 용융 풀에서 더 낮았습니다. Hermans와 den Ouden (1999)은 단락 가스 금속 아크 용접에서 용융 풀 진동을 분석했습니다. [5]. 그들은 용융 풀의 단락 주파수와 고유 주파수가 같을 때 부분적으로 침투 된 용융 풀의 경우 공정 안정성이 향상되었음을 보여주었습니다. Yudodibroto et al. (2004)는 가스 텅스텐 아크 용접에서 용융 풀 진동에 대한 필러 와이어의 영향을 조사했습니다 [6] . 그들은 금속 전달이 특히 부분적으로 침투 된 용융 풀에서 진동 거동을 방해한다는 것을 보여주었습니다. Geiger et al. (2009) 레이저 키홀 용접에서 발광 분석 [7]. 신호의 주파수 분석을 사용하여 용융 풀 (1.5kHz 미만)과 키홀 (약 3kHz)에 해당하는 진동 주파수 범위를 찾았습니다. Kägeler와 Schmidt (2010)는 레이저 용접에서 용융 풀 크기의 변화를 관찰하기 위해 고속 카메라를 사용했습니다 [8] . 그들은 용융 풀에서 지배적 인 저주파 진동 성분 (100Hz 미만)을 발견했습니다. Shi et al. (2015) 고속 카메라를 사용하여 펄스 가스 텅스텐 아크 용접에서 용융 풀 진동 주파수 분석 [9]. 그들은 용접 침투 깊이가 작을수록 용융 풀의 진동 빈도가 더 높다는 것을 보여주었습니다. 추출 된 진동 주파수는 완전 용입 용접의 경우 85Hz 미만 이었지만 부분 용입 용접의 경우 110Hz에서 125Hz 사이였습니다. Volpp와 Vollertsen (2016)은 레이저 키홀 역학을 분석하기 위해 광학 신호를 사용했습니다 [10] . 그들은 공간 레이저 강도 분포로 인해 0.8에서 154 kHz 사이의 고주파 범위에서 피크를 발견했습니다. 위에서 언급 한 실험적 접근법은 공정 조건, 측정 방법 및 측정 된 위치에 따라 수십 Hz에서 수십 kHz까지 광범위한 용융 풀 역학에 대한 결과를 보여 주었다는 점에 유의해야합니다.

융합 용접에서 용융 풀 역학을 연구하기 위해 분석 접근 방식도 사용되었습니다. Zacksenhouse와 Hardt (1983)는 2.5mm 두께의 강판에서 대칭형 완전 관통 용융 풀의 고유 진동수를 계산했습니다 [2] . 매스 스프링 해석 모델을 사용하여 용융 풀 반경 6mm (고정 용접)에 대해 20.4Hz (실험에서 18.9Hz)의 고유 진동수와 3mm 풀 반경 (연속 용접)에 대해 40Hz의 고유 진동수를 예측했습니다. ). Postacioglu et al. (1989)는 원통형 용융 풀과 키홀을 가정하여 레이저 용접의 용융 풀에서 키홀 진동의 고유 진동수를 계산했습니다 .. 특정 열쇠 구멍 모양의 경우 약 900Hz의 기본 주파수가 계산되었습니다. Postacioglu et al. (1991)은 또한 레이저 용접에서 용접 속도를 고려하기 위해 타원형 용융 풀의 고유 진동수를 계산했습니다 [12] . 그들은 타원형 용융 풀의 모양이 고유 진동수에 영향을 미친다는 것을 보여주었습니다. 고유 진동수는 축의 길이 비율이 낮았으며, 즉 타원의 반장 축과 반 단축의 비율이 낮았습니다. Kroos et al. (1993)은 축 대칭 용융 풀과 키홀을 가정하여 레이저 키홀 용접의 동적 거동에 대한 이론적 모델을 개발했습니다 .. 키홀 폐쇄 시간은 0.1ms였으며 안정성 분석은 약 500Hz의 주파수에서 공진과 같은 진동을 예측했습니다. Maruo와 Hirata (1993)는 완전 관통 아크 용접에서 용융 풀을 모델링했습니다 [14] . 그들은 녹은 웅덩이가 정적 타원 모양을 가지고 있다고 가정했습니다. 그들은 고유 진동수와 진동 모드 사이의 관계를 조사하고 용융 풀 크기가 감소함에 따라 고유 진동수가 증가한다는 것을 보여주었습니다. Klein et al. (1994)는 원통형 키홀 모양을 사용하여 완전 침투 레이저 용접에서 키홀 진동을 연구했습니다 [15] . 그들은 점성 감쇠로 인해 키홀 진동이 낮은 kHz 범위로 제한된다는 것을 보여주었습니다. Klein et al. (1996)은 또한 레이저 출력의 작은 변동이 강한 키홀 진동으로 이어질 수 있음을 보여주었습니다[16] . 그들은 키홀 진동의 주요 공진 주파수 범위가 500 ~ 3500Hz라는 것을 발견했습니다. Andersen et al. (1997)은 고정 가스 텅스텐 아크 용접 [17] 에서 고정 된 원통형 모양을 가정하여 용융 풀의 고유 진동수를 예측 했으며 완전 용입 용접에서 용융 풀 폭이 증가함에 따라 감소하는 것으로 나타났습니다. 3.175mm 두께의 강판의 경우 주파수는 20Hz ~ 100Hz 범위였습니다. 위에 표시된 분석 방법은 일반적으로 단순한 용융 풀 모양을 가정하고 고유 진동수를 계산했습니다. 이것은 단순한 용융 풀 모양으로 고정 용접 공정을 분석하는 데 충분하지만 대부분의 용접 사례를 설명하는 과도 용접 공정에서 용융 풀 역학 분석에는 적합하지 않습니다.

반면에 수치 접근 방식은 고온 및 강한 빛과 같은 실험적 제한없이 자세한 정보를 제공하기 때문에 용융 풀 역학을 분석하는 이점이 있습니다. 전산 유체 역학 (CFD)의 수치 시뮬레이션 기술이 발전함에 따라 용융 풀 역학 분석에 대한 많은 연구가 수행되었습니다. 실제 용융 표면 변화는 VOF (체적 부피) 방법을 사용하여 계산할 수 있습니다. Cho et al. (2010) CO 2 레이저-아크 하이브리드 용접 공정을 위한 수학적 모델 개발 [18], 구형 방울이 생성 된 금속 와이어의 용융 과정이 와이어 공급 속도와 일치한다고 가정합니다. 그들은 필러 와이어가 희석되는 용융 풀 동작을 보여주었습니다. Cho et al. (2012)는 높은 빔 품질과 높은 금속 흡수율로 인해 업계에서 널리 사용되는 디스크 레이저 키홀 용접으로 수학적 모델을 확장했습니다 [19] . 그들은 열쇠 구멍에서 레이저 광선 번들의 다중 반사를 고려하고 용융 풀에서 keyholing과 같은 빠른 표면 변화를 자세히보고했습니다. 최근 CFD 시뮬레이션은 험핑 (Otto et al., 2016 [20] ) 및 기공 (Lin et al., 2017 [21] )과 같은보다 구체적인 현상을 분석하는데도 사용되었습니다 .) 레이저 용접에서. 그러나 용융 풀 역학과 관련된 연구는 거의 수행되지 않았습니다. Ko et al. (2000)은 수치 시뮬레이션을 사용하여 가스 텅스텐 아크 용접 풀의 동적 거동을 조사했습니다 [22] . 그들은 완전히 침투 된 용융 풀이 부분적으로 침투 된 풀보다 낮은 주파수에서 진동한다는 것을 보여주었습니다. 진동은 수십 분의 1 초 내에 무시할 수있는 크기로 감쇠되었습니다. Geiger et al. (2009)는 또한 수치 시뮬레이션을 사용하여 레이저 용접에서 용융 풀 거동을 보여주었습니다 [7]. 그들은 계산 된 증발 속도를 주파수 분석에 사용하여 공정에서 나오는 빛의 실험 결과와 비교했습니다. 판금 레이저 용접에서 중요한 공간 빔 진동 및 추가 필러 재료가있는 공정에 대한 용융 풀 역학에 대한 연구도 불충분합니다. Hu et al. (2018)은 금속 전달 메커니즘을 밝히기 위해 전자빔 3D 프린팅에서 와이어 공급 모델링을 수행했습니다. 그들은 주로 열 입력에 의해 결정되는 액체 브리지 전이, 액적 전이 및 중간 전이의 세 가지 유형의 금속 전달 모드를 보여주었습니다 .. Meng et al. (2020)은 레이저 빔 용접에서 용융 풀에 필러 와이어에 의해 추가 된 추가 요소의 전자기 교반 효과를 모델링했습니다. 용가재의 연속적인 액체 브릿지 이동이 가정되었고, 그 결과 전자기 교반의 영향이 키홀 깊이에 미미한 반면 필러 와이어 혼합을 향상 시켰습니다 [24] . Cho et al. (2017) 용접 방향에 수직 인 1 차원 빔 진동과 용접 라인을 따라 공급되는 필러 와이어를 사용하여 레이저 용접을위한 시뮬레이션 모델 개발 [25]. 그들은 시뮬레이션을 사용하여 특정 용접 현상, 즉 용융 풀의 단추 구멍 형성을 보여주었습니다. Cho et al. (2018)은 다중 반사 수와 전력 흡수량의 푸리에 변환을 사용하여 주파수 영역에서 소위 쵸핑 주파수 (2 x 빔 발진 주파수) 성분을 발견했습니다 [26] . 그러나 그들은 용융 풀 역학을 분석하기 위해 간접 신호를 사용했습니다. 따라서보다 직관적 인 분석을 위해서는 표면의 변동을 직접 측정해야합니다.

이 연구는 이전 연구에서 개발 된 레이저 용접 모델을 사용하여 3 차원 과도 CFD 시뮬레이션을 수행하여 빔 진동 및 필러 와이어 공급을 포함한 레이저 용접 공정에서 용융 풀 역학을 조사합니다. 용융 된 풀 표면의 시간적 변화는 시뮬레이션 결과에서 추출되었습니다. 추출 된 데이터는 주파수 영역뿐만 아니라 시간-주파수 영역에서도 분석되었습니다. 신호 처리를 통해 도출 된 결과는 특징적인 용융 풀 역학을 나타내며 빔 진동 주파수 및 단추 구멍 형성 측면에서 레이저 용접의 역학을 줄일 수있는 잠재력을 제공합니다.

2 . 방법론

그림 1도 1은 용접 방향에 수직 인 1 차원 빔 진동과 용접 라인을 따라 공급되는 필러 와이어를 사용하는 레이저 용접 프로세스의 개략적 설명을 보여줍니다. 1mm 두께의 알루미늄 합금 (AlSi1MgMn) 시트는 시트 표면에 초점을 맞춘 멀티 kW 파이버 레이저 (YLR-8000S, IPG Photonics, USA)를 사용하여 용접되었습니다. 시트는 에어 갭이있는 맞대기 이음으로 정렬되었습니다. 1 차원 스캐너 (ILV DC-Scanner, Ingenieurbüro für Lasertechnik + Verschleiss-Schutz (ILV), 독일)를 사용하여 레이저 빔의 1 차원 정현파 진동을 실현했습니다. 이 스캔 시스템에서 최대 진동 폭은 250Hz의 진동 주파수에서 1.4mm입니다. 오정렬에 대한 공차를 개선하기 위해 동일한 최대 너비 값이 사용되었습니다. 와이어 공급 시스템은 1을 공급했습니다. 2mm 직경의 알루미늄 합금 (AlSi5) 필러 와이어를 일정한 공급 속도로 에어 갭을 채 웁니다. 1mm 에어 갭의 경우 와이어 이송 속도는 용접 속도의 1.5 배 값으로 설정되었으며 참조 실험 조건은 문헌에서 얻었습니다 (Schultz, 2015 참조).[27] ).

그림 1

CFD 시뮬레이션은 레이저 용접에서 열 전달 및 용융 풀 동작을 계산하기 위해 수행되었습니다. 그림 2 는 CFD 시뮬레이션을위한 계산 영역을 보여줍니다. 실온에서 1.2mm 직경의 필러 와이어가 공급되고 레이저 빔이 진동했습니다. 1mm 두께의 공작물이 용접 속도로 왼쪽에서 오른쪽으로 이동했습니다. 0.1mm의 최소 메쉬 크기가 도메인에서 생성되었습니다. 침투 깊이가 더 깊은 이전 연구의 메쉬 테스트 결과는 0.2mm 이하의 메쉬 크기로 시뮬레이션 정확도가 확보 된 것으로 나타 났으므로 [28] 본 연구에서 사용 된 메쉬 크기가 적절할 수 있습니다. 도메인을 구성하는 세포의 수는 약 120 만 개였습니다. 1 번 테이블사용 된 레이저 용접 매개 변수를 보여줍니다. 용융 풀 역학 측면에서 다양한 진동 주파수와 에어 갭 크기가 고려되었으며 12 개의 용접 사례가 표 2 에 나와 있습니다. 표 3 은 시뮬레이션에 사용 된 알루미늄 합금과 순수 알루미늄 (Cho et al., 2018 [26] )의 표면 장력 계수를 제외하고 온도와 무관 한 열-물리적 재료 특성을 보여줍니다 . 여기서 표면 장력 계수는 액체 온도에서 온도와 표면 장력 계수 사이의 선형 관계를 가진 유일한 온도 의존적 ​​특성이었습니다.

그림 2

표 1 . . 레이저 용접 매개 변수.

레이저 용접 매개 변수
레이저 빔 파워3.0kW
빔 허리 반경50µm *
용접 속도6.0m / 분
와이어 공급 속도9.0m / 분
빔 진동 폭1.4mm
빔 진동 주파수100Hz, 150Hz, 200Hz, 250Hz
에어 갭 크기0.8mm, 0.9mm, 1.0mm, 1.1mm

반경은 1.07μm의 파장, 4.2mm • mrad의 빔 품질, 시준 초점 거리 및 초점 렌즈 200mm, 광섬유 직경 100μm의 원형 빔을 가정하여 계산되었습니다.

표 2 . 이 연구에서 고려한 용접 사례.

에어 갭 크기 [mm]진동 주파수 [Hz]
100150200250
0.9사례 1엑스엑스엑스
1.0사례 2사례 4사례 7사례 10
1.1사례 3사례 5사례 8사례 11
1.2엑스사례 6사례 912면

표 3 . 시뮬레이션에 사용 된 열 물리적 재료 특성 (Cho et al., 2018 [26] ).

특성상징
밀도ρ2700kg / m3
열 전도성케이1.7×102Wm K
점도ν1.15×10−삼kg / ms
표면 장력 계수 티엘*γ엘0.871 J / m2
표면 장력 온도 구배 *−1.55×10−4J / m 2 K
표면 장력 계수γγ엘−ㅏ(티−티엘)
비열8.5×102J / kg K
융합 잠열h에스엘3.36×105J / kg
기화 잠열 *hV1.05×107J / kg
Solidus 온도티에스847K
Liquidus 온도티엘905K
끓는점 *티비2743K

순수한 알루미늄.

시뮬레이션을 위해 단상 뉴턴 유체와 비압축성 층류가 가정되었습니다. 질량, 운동량 및 에너지 보존의 지배 방정식을 해결하여 계산 영역에서 속도, 압력 및 온도 분포를 얻었습니다. VOF 방법은 자유 표면 경계를 찾는 데 사용되었습니다. 스칼라 보존 방정식을 추가로 도입하여 용융 풀에서 충전재의 부피 분율을 계산했습니다. 시뮬레이션에 사용 된 레이저 용접의 수학적 모델은 다음과 같습니다. 레이저 빔은 가우스와 같은 전력 밀도 분포를 기반으로 697 개의 광선 에너지 번들로 나뉩니다. 광선 추적 방법을 사용하여 다중 반사를 고려했습니다. 재료에 대한 레이저 빔의 반사 (또는 흡수) 에너지는 프레 넬 반사 모델을 사용하여 계산되었습니다. 온도에 따른 흡수율의 변화를 고려 하였다. 혼합물의 흡수율은베이스 및 충전제 물질 분획의 가중 평균을 사용하여 계산되었습니다. 반동 압력과 부력도 고려되었습니다. 경계 조건으로 에너지와 압력의 균형은 VOF 방법으로 계산 된 자유 표면에서 고려되었습니다. 레이저 용접 모델과 지배 방정식은 FLOW-3D v.11.2 (2017), Flow Science, Inc.에서 유한 차분 방법과 유한 체적 방법을 사용하여 이산화되고 해결되었습니다. 경계 조건으로 에너지와 압력의 균형은 VOF 방법으로 계산 된 자유 표면에서 고려되었습니다. 레이저 용접 모델과 지배 방정식은 FLOW-3D v.11.2 (2017), Flow Science, Inc.에서 유한 차분 방법과 유한 체적 방법을 사용하여 이산화되고 해결되었습니다. 경계 조건으로 에너지와 압력의 균형은 VOF 방법으로 계산 된 자유 표면에서 고려되었습니다. 레이저 용접 모델과 지배 방정식은 FLOW-3D v.11.2 (2017), Flow Science, Inc.에서 유한 차분 방법과 유한 체적 방법을 사용하여 이산화되고 해결되었습니다.[29] . 계산에는 48GB RAM이 장착 된 Intel® Xeon® 프로세서 E5649로 구성된 워크 스테이션이 사용되었습니다. 계산 시스템을 사용하여 0.2 초 레이저 용접을 시뮬레이션하는 데 약 18 시간이 걸렸습니다. 지배 방정식 (Cho and Woizeschke, 2020 [30] ) 및 레이저 용접 모델 (Cho et al., 2018 [26] )에 대한 자세한 설명은 부록 A 에서 확인할 수 있습니다 .

그림 3 은 용융 풀 변동의 직접 측정에 대한 개략적 설명을 보여줍니다. 용융 풀의 역학을 분석하기 위해 시뮬레이션 중에 용융 풀 표면의 시간적 변동 운동을 측정했습니다. 상단 및 하단 표면 모두에서 10kHz의 샘플링 주파수로 변동을 측정 한 반면, 측정 위치는 X 축의 레이저 빔 위치에서 2mm 떨어진 용접 중심선에있었습니다. 그림 4시간 신호를 분석하는 데 사용되는 푸리에 변환 및 웨이블릿 변환의 개략적 설명을 보여줍니다. 측정 된 시간 신호는 고속 푸리에 변환 (FFT) 방법을 사용하여 주파수 영역으로 변환되었습니다. 결과는 측정 기간 동안 평균화 된 주파수 성분의 크기를 보여줍니다. 웨이블릿 변환 방법은 시간-주파수 영역에서 국부적 인 특성을 찾는 데 사용되었습니다. 결과는 주파수 구성 요소의 크기뿐만 아니라 시간 변화도 보여줍니다.

그림 3
그림 4

3 . 결과

이 연구 에서는 표 2에 표시된 12 가지 용접 사례 를 시뮬레이션했습니다. 그림 5 는 3 차원 시뮬레이션 결과를 평면도 와 바닥면으로 보여줍니다. 결과는 용융 된 풀의 거동에 따라 분류 할 수 있습니다 : 단추 구멍 형성 없음 (녹색), 안정 또는 불안정 단추 구멍 있음 (파란색), 불안정한 단추 구멍으로 인한 구멍 결함 (빨간색). 일반적인 열쇠 구멍보다 훨씬 큰 직경을 가진 단추 구멍은 레이저 용접의 특정 진동 조건에서 나타날 수 있습니다 (Vollertsen, 2016 [31]). 진동 주파수가 증가함에 따라 용접 이음 부 코스 및 스케일링 측면에서 시각적 이음새 품질이 향상되었습니다. 고주파에서 스케일링은 무시할 수있을 정도 였고 코스는 균질했습니다. 언더컷 결함의 발생도 감소했습니다. 그러나 관통 결함 부족 (case 7, case 10)이 나타났다. 에어 갭은 단추 구멍 형성에 중요했습니다. 에어 갭 크기가 증가함에 따라 단추 구멍이 더 쉽게 형성되었지만 구멍 결함으로 더 쉽게 남아 있습니다. 안정적인 단추 구멍 형성은 고려 된 공극 조건의 좁은 영역에서만 나타납니다.

그림 5

그림 6 은 시뮬레이션과 실험에서 융합 영역의 모양을 보여줍니다. 버튼 홀이없는 경우 1, 불안정한 버튼 홀 형성이있는 경우 8, 안정적인 버튼 홀 형성이있는 경우 11의 3 가지 경우에 대해 시뮬레이션 결과와 실험 결과를 비교하여 유사성을 나타냈다. 본 연구에서 고려한 용접 조건의 경우 표면 품질 결과는 Fig. 5 와 같이 큰 차이를 보였으 나 단면 융착 영역 [26] 과 형상은 큰 차이를 보이지 않았다.

그림 6

무화과. 7 과 8 은 각각 100Hz와 250Hz의 진동 주파수에서 시뮬레이션 결과를 기반으로 분석 된 용융 풀 역학과 시뮬레이션 및 실험 결과를 보여줍니다. 이전 연구에서 볼 수 있듯이 레이저 빔의 진동 주파수는 단추 구멍 형성과 밀접한 관련이 있습니다 (Cho et al., 2018 [26] 참조 ). 그림 7 (a) 및 (b)는 각각 시뮬레이션 및 실험을 기반으로 한 진동 주파수 100Hz에서 대표적인 용융 풀 동작을 보여줍니다. 완전히 관통 된 키홀 및 버튼 홀 형성은 관찰되지 않았으며 응고 후 거친 비드 표면이 남았습니다. 그림 7(c)와 (d)는 각각 윗면과 바닥면의 표면 변동에 대한 시뮬레이션 결과를 기반으로 한 용융 풀 역학 분석을 보여줍니다. 샘플링 데이터는 상단 표면이 공작물의 상단 표면 위치에서 평균적으로 변동하는 반면 하단 표면은 공작물의 하단 표면 위치에서 평균적으로 변동하는 것으로 나타났습니다. 표면 변동의 푸리에 변환 및 웨이블릿 변환 결과는 명확한 1  주파수 (2 x 빔 발진 주파수, 이른바 초핑 주파수, Cho et al., 2018 [26] 참조 ) 및 2  주파수 (4 x 빔 발진)를 보여줍니다. 주파수) 두 표면의 구성 요소, 그러나 바닥 표면과 첫 번째에 대한 결과주파수 성분이 더 강합니다. 반면 그림 8 (a)와 (b)에서 보는 바와 같이 250Hz의 진동 주파수에서 시뮬레이션과 실험 결과는 안정된 버튼 홀 형성과 응고 후 매끄러운 비드 표면을 나타냈다. 그림 8 의 샘플링 신호의 진폭은 그림 7 의 진폭 보다 작으며 푸리에 변환 및 웨이블릿 변환의 결과에서 중요한 주파수 성분이 발견되지 않았습니다.

Fi 7
그림 8

Fig. 9 는 진동 주파수 200Hz에서 시뮬레이션 결과를 바탕으로 분석 된 용융 풀 역학과 시뮬레이션 및 실험 결과를 보여준다. 이 주파수에서 Fig. 9 (a)와 (b) 에서 보는 바와 같이 , 시뮬레이션과 실험 모두에서 불안정한 buttonhole 거동이 관찰되었다. 바닥면에서 샘플링 데이터의 푸리에 변환 및 웨이블릿 변환의 결과 빔 발진 주파수 성분이 발견되었습니다.

그림 9

4 . 토론

시뮬레이션 및 실험 결과는 비드 표면 품질이 향상되고 빔 진동 주파수가 증가함에 따라 버튼 홀이 형성되는 것으로 나타났습니다. 표면의 변동 데이터에 대한 푸리에 변환 및 웨이블릿 변환의 결과에 따라 다음과 같은 주요 주파수 구성 요소가 발견되었습니다. 1  및 2 버튼 홀 형성이없는 주파수, 불안정한 용융 풀 거동이있는 빔 진동 주파수, 안정적인 버튼 홀 형성이있는 중요한 주파수 성분이 없습니다. 이들 중 불안정한 용융 풀 동작과 관련된 빔 진동 주파수 성분은 완전히 관통 된 키홀과 반복적으로 생성 및 붕괴되는 불안정한 버튼 홀의 특성으로 인해 웨이블릿 변환 결과에서 명확한 실선 형태로 나타나지 않았습니다. 분석 결과는 윗면보다 바닥면에서 더 분명했습니다. 이는 필러 와이어 공급 및 키홀 링 공정에서 강한 하향 흐름으로 인해 용융 풀 역학이 바닥 표면 영역에서 더 강했기 때문입니다. 진동 주파수가 증가함에 따라 용융 풀 역학과 상단 표면과 하단 표면 간의 차이가 감소했습니다.

첫 번째 주파수 (2 x 빔 진동 주파수)는이 연구에서 관찰 된 가장 분명한 구성 요소였습니다. Schultz et al. (2018)은 또한 실험을 통해 동일한 성분을 발견했습니다 [32] , 용융 풀 표면 운동에 대한 푸리에 분석을 수행했습니다. 첫 번째 주파수 성분은 빔 발진주기 당 두 개의 주요 이벤트가 있음을 의미합니다. 이것은 레이저 빔이 빔 진동주기 당 두 번 와이어를 절단하거나 절단하는 프로세스와 일치합니다. 용융 된 와이어 팁은 낮은 진동 주파수에서 고르지 않고 날카로운 모서리를 갖는 것으로 나타났습니다 (Cho et al., 2018 [26] ). 이것은 첫 번째 원인이 될 수 있습니다.용융 된 풀에서 지배적이되는 주파수 성분. 진동 주파수가 증가하면 용융 된 와이어 팁이 더 균일 해 지므로 효과가 감소합니다. 용접 방향으로의 정현파 횡 방향 빔 진동을 통한 에너지 집중도 빔 진동주기 당 두 번 발생합니다. 그림 10 은 발진 주파수에 따른 레이저 빔의 라인 에너지 (단위 길이 당 에너지)의 변화를 보여줍니다. 그림 10 b) 의 라인 에너지 는 레이저 출력을 공정 속도로 나누어 계산했습니다. 여기서 처리 속도는(w이자형엘디나는엔지에스피이자형이자형디)2+(디(에스나는엔유에스영형나는디ㅏ엘wㅏV이자형나는엔에프나는지.10ㅏ))디티)2. 낮은 발진 주파수에서 라인 에너지는 발진 폭의 양쪽 끝에 과도하게 집중됩니다. 이러한 집중된 에너지는 과도한 키홀 링 프로세스를 초래하므로 언더컷 결함이 나타날 수있는 높은 흐름 역학이 발생합니다. 진동 주파수가 증가함에 따라 집중 에너지는 더 작은 조각으로 나뉩니다. 따라서 높은 진동 주파수에서 과도한 키홀 링 및 수반되는 언더컷 결함의 발생이 감소되었습니다. 위에서 언급 한 두 가지 현상 (불균일 한 와이어 팁과 집중된 라인 에너지)은 빔 발진주기 당 두 번 발생하며 발진 주파수가 증가하면 그 효과가 감소합니다. 따라서 저주파 에서 2  주파수 성분 (4 x 빔 발진 주파수)이 나타나는 것은이 두 현상의 동시 작용입니다.

그림 10

두 가지 현상 중 첫 번째 주파수 에 대한 주된 효과 는 집중된 라인 에너지입니다. Cho et al. (2018)은 전력 흡수 데이터를 푸리에 변환을 사용하여 분석했을 때 1  주파수 성분이 더 우세 해졌고, 2  주파수 성분은 발진 주파수가 증가함에 따라 상대적으로 약화 되었음을 보여주었습니다 [26] . 용융 된 와이어 팁은 또한 빈도가 증가함에 따라 더욱 균일 해졌습니다. 결과는 진동 주파수의 증가가 용융 풀에 대한 와이어의 영향을 제거하는 것으로 나타났습니다. 따라서 발진 주파수가 증가함에 따라 라인 에너지 집중의 영향 만 남을 수 있습니다. 그림 10 과 같이, 집중 선 에너지가 작은 조각으로 분할되기 때문에 효과도 감소하지만 최대 값이 변경되지 않았기 때문에 여전히 효과적입니다.

빔 진동 주파수 성분은 불안정한 단추 구멍 및 열쇠 구멍 붕괴를 수반하는 불안정한 용융 풀 동작과 관련이 있습니다. 언더컷 결함이있는 케이스 8 (발진 주파수 200Hz)에서 발진 주파수 성분이 관찰되었습니다. 이것은 특히 완전히 관통 된 열쇠 구멍과 불안정한 단추 구멍에서 불안정한 용융 풀 동작을 보여주었습니다. 경우 10 (진동 주파수 250Hz)의 경우 상대적으로 건강한 비드가 형성 되었으나, 도 11 (a) 와 같이 웨이블릿 변환 결과에서 t1의 시간 간격으로 진동 주파수 성분이 관찰되었다 . 이 시간 간격 t1의 용융 풀 거동은 그림 11에 나와 있습니다.(비). 완전히 관통 된 열쇠 구멍이 즉시 무너지는 것이 분명하게 관찰되었습니다. 이것은 진동 주파수 성분이 불안정한 용융 풀 거동과 밀접한 관련이 있음을 보여줍니다. 발견 된 주파수 성분으로부터 완전히 관통 된 열쇠 구멍과 같은 불안정한 용융 풀 거동을 예측할 수 있습니다. 완전히 관통 된 키홀이 반복적으로 붕괴되기 때문에 빔 진동 주파수 성분은 그림 9 (d) 와 같이 웨이블릿 변환 결과에서 명확한 실선 형태로 보이지 않습니다 .

그림 11

Cho and Woizeschke (2020)에 따르면 단추 구멍 형성은 자체 지속 가능한 카테 노이드처럼 작용하기 때문에 용융 풀 역학을 감소시킬 수 있습니다 [30] . 그림 12 는 버튼 홀 형성 측면에서 t2의 시간 간격에서 용융 풀 거동의 변화를 보여줍니다. 단추 구멍은 t2의 간헐적 인 부분에만 형성되었습니다. 1st 이후이 시간 동안 웨이블릿 변환의 결과로 주파수 성분이 사라졌고, 버튼 홀 형성은 용융 풀 역학을 줄이는 데 효과적이었습니다. 따라서, 웨이블릿 변환의 결과로 주파수 성분이 지워지는 것을 관찰함으로써 버튼 홀 형성을 예측할 수있다. 이와 관련하여 웨이블릿 변환 기술은 시간에 따른 용융 풀 변화를 나타낼 수 있습니다. 이 기술은 향후 용융 풀 동작을 모니터링하는 데 사용될 수 있습니다.

그림 12

5 . 결론

CFD 시뮬레이션 결과를 사용하여 빔 진동 및 필러 와이어 공급을 통한 레이저 용접에서 용융 풀 역학을 분석 할 수있었습니다. 용융 풀 표면의 변동 데이터의 푸리에 변환 및 웨이블릿 변환은 여기서 용융 풀 역학을 분석하는 데 사용되었습니다. 결과는 다음과 같은 결론으로 ​​이어집니다.1.

 주파수 (2 x 빔 발진 주파수, 이른바 초핑 주파수), 2  주파수 (4 x 빔 발진 주파수) 및 빔 발진 주파수 성분은 푸리에 변환 및 웨이블릿 변환 분석에서 발견 된 주요 성분이었습니다.2.

 주파수와 2  주파수 성분 의 출현은 두 가지 사건, 즉 레이저 빔에 의한 필러 와이어의 절단 공정과 집중된 레이저 라인 에너지의 효과의 결과였습니다. 이는 빔 진동주기 당 두 번 발생했습니다. 따라서 두 번째 주파수 성분은 동시 작용으로 인해 발생했습니다. 빔 진동 주파수 성분은 불안정한 용융 풀 동작과 관련이 있습니다. 구성 요소는 열쇠 구멍과 단추 구멍의 붕괴와 함께 나타났습니다.삼.

낮은 발진 주파수에서는 1  주파수와 2  주파수 성분이 함께 나타 났지만 발진 주파수가 증가함에 따라 그 크기가 함께 감소했습니다. 집중 선 에너지는 주파수가 증가함에 따라 최대 값이 변하지 않는 반면, 잘게 잘린 선단이 평평 해져 그 효과가 사라졌기 때문에 쵸핑 프로세스보다 더 큰 영향을 미쳤습니다.4.

용융 풀 거동의 빠른 시간적 변화는 웨이블릿 변환 방법을 사용하여 분석되었습니다. 따라서이 방법은 열쇠 구멍 및 단추 구멍의 형성 및 붕괴와 같은 일시적인 용융 풀 변화를 해석하는 데 사용할 수 있습니다.

CRediT 저자 기여 성명

조원익 : 개념화, 방법론, 소프트웨어, 검증, 형식 분석, 조사, 데이터 큐 레이션, 글쓰기-원고, 글쓰기-검토 및 편집. Peer Woizeschke : 감독, 프로젝트 관리, 작문-검토 및 편집.

경쟁 관심의 선언

저자는이 논문에보고 된 작업에 영향을 미칠 수있는 경쟁적인 재정적 이해 관계 나 개인적 관계가 없다고 선언합니다.

감사의 말

이 작업은 알루미늄 합금 용접 역량 센터 (Centr-Al)에서 수행되었습니다. Deutsche Forschungsgemeinschaft (DFG, 프로젝트 번호 290705638 , “용접 풀 캐비티를 생성하여 레이저 깊은 용입 용접에서 매끄러운 이음매 표면”) 의 자금은 감사하게도 인정됩니다.

부록 A . 사용 된 지배 방정식 및 레이저 용접 모델

1 . 지배 방정식 (Cho 및 Woizeschke [ 30 ])

-대량 보존 방정식,(A1)∇·V→=미디엄˙에스ρ어디, V→속도 벡터입니다. ρ밀도이고 미디엄˙에스필러 와이어를 공급하여 질량 소스의 비율입니다. 단위미디엄에스단위 부피당 질량입니다. WFS (와이어 공급 속도) 및 필러 와이어의 직경과 같은 매스 소스 및 필러 와이어 조건,디w계산 영역에서 다음과 같은 관계가 있습니다.(A2)미디엄=∫미디엄에스디V=미디엄0+씨×ρ×W에프에스×π디w24×티어디, 미디엄총 질량, 미디엄0초기 총 질량, V볼륨입니다.씨단위 변환 계수입니다. 티시간입니다.

-운동량 보존 방정식,(A3)∂V→∂티+V→·∇V→=−1ρ∇피+ν∇2V→−케이V→+미디엄˙에스ρ(V에스→−V→)+지어디, 피압력입니다. ν동적 점도입니다. 케이뭉툭한 영역의 다공성 매체 모델에 대한 항력 계수, V에스→질량 소스에 대한 속도 벡터입니다. 지신체 힘으로 인한 신체 가속도입니다.

-에너지 절약 방정식,(A4)∂h∂티+V→·∇h=1ρ∇·(케이∇티)+h˙에스어디, h특정 엔탈피입니다. 케이열전도율, 티온도이고 h˙에스특정 엔탈피 소스로, Eq 의 질량 소스와 연관됩니다 (A1) . 계산 영역의 총 에너지,이자형다음과 같이 계산됩니다.(A5)이자형=∫미디엄에스h에스디V=∫미디엄에스씨Vw티w디V어디, 씨Vw질량 원의 비열, 티w질량 소스의 온도입니다.

또한, 엔탈피 기반 연속체 모델을 사용하여 고체-액체 상 전이를 고려했습니다.

-VOF 방정식,(A6)∂에프∂티+∇·(V→에프)=에프˙에스어디, 에프유체가 차지하는 부피 분율이며 0과 1 사이의 값을 가지며 에프˙에스질량의 소스와 연결된 유체의 체적 분율의 비율 식. (A1) . 질량 공급원에 해당하는 부피 분율은 다음에 할당됩니다.에프에스.

-스칼라 보존 방정식,(A7)∂Φ∂티+∇·(V→Φ)=Φ˙에스어디, Φ필러 와이어의 스칼라 값입니다. 셀의 유체가 전적으로 필러 와이어로 구성된 경우Φ1이고 유체에 대한 필러 와이어의 부피 분율에 따라 0과 1 사이에서 변경됩니다. Φ˙에스Eq 에서 질량 소스에 연결된 스칼라 소스의 비율입니다 (A1) . 스칼라 소스는 전적으로 필러 와이어이기 때문에 1에 할당됩니다. 확산 효과는 고려되지 않았습니다.

2 . 레이저 용접 모델 (Cho et al. [26] )

흡수율을 계산하기 위해 프레 넬 반사 모델을 사용했습니다. ㅏ=1−ρ씨재료의 표면 상에 도시 된 바와 같이 수학 식. (A8) 원 편광 빔의 경우.(A8)ㅏ=1−ρ씨=1−12(ρ에스+ρ피)어디,ρ에스=(엔1씨영형에스θ−피)2+큐2(엔1씨영형에스θ+피)2+큐2,ρ에스=(피−엔1에스나는엔θ티ㅏ엔θ)2+큐2(피+엔1에스나는엔θ티ㅏ엔θ)2+큐2,피2=12{[엔22−케이22−(엔1에스나는엔θ)2]2+2엔22케이22+[엔22−케이22−(엔1에스나는엔θ)2]},큐2=12{[엔22−케이22−(엔1에스나는엔θ)2]2+2엔22케이22−[엔22−케이22−(엔1에스나는엔θ)2]}.어디, 복잡한 인덱스 엔1과 케이1반사 지수와 공기의 흡수 지수이며 엔2과 케이2공작물을위한 것입니다. θ입사각입니다. 도시 된 바와 같이 수학 식. (A9)에서 , 혼합물의 흡수율은 식에서 얻은 모재 및 필러 와이어 분획의 가중 평균이됩니다 . (A7) .(A9)ㅏ미디엄나는엑스티유아르 자형이자형=Φㅏw나는아르 자형이자형+(1−Φ)ㅏ비ㅏ에스이자형어디, ㅏ비ㅏ에스이자형과 ㅏw나는아르 자형이자형각각 비금속과 필러 와이어의 흡수율입니다.

자유 표면 경계에서의 반동 압력 에이 싱은 Eq. (A10) .(A10)피아르 자형(티)≅0.54피에스ㅏ티(티)=0.54피0이자형엑스피(엘V티−티비아르 자형¯티티비)어디, 피에스ㅏ티포화 압력, 피0대기압입니다. 엘V기화의 잠열, 티비끓는 온도이고 아르 자형¯보편적 인 기체 상수입니다.

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Numerical simulation of slag movement from Marangoni flow for GMAW with computational fluid dynamics Figures

Numerical simulation of slag movement from Marangoni flow for GMAW with computational fluid dynamics

전산 유체 역학을 사용하여 GMAW에 대한 Marangoni 흐름에서 슬래그 이동의 수치 시뮬레이션

Dae-WonChoaYeong-DoParkbMuralimohanCheepucaBusan Machinery Research Center, Korea Institute of Machinery and Materials, 48, Mieumsandan 5-ro 41beon-gil, Gangseo-gu, Busan 46744, Republic of KoreabDepartment of Advanced Materials Engineering, Dong-Eui University, Busan, Republic of KoreacSuper-TIG Welding Co., Limited, Busan, Republic of Korea

Keywords : Marangoni flowMolten slag movementMolten pool behavorSurface tension gradient

Abstract

이 연구는 전산 유체 역학을 이용하여 스프레이 모드 가스 금속 아크 용접에서 생성되는 산화물인 용융 슬래그의 거동을 분석했습니다. 주로 규산염 (SiO2)으로 구성된 용융 슬래그는 용융 풀 표면에 있습니다. 일반적으로 용융 슬래그는 아크 플라즈마 경계 주변에서 생성된다고 가정합니다.

따라서 이 연구의 수치 시뮬레이션에서 슬래그는 특정 밀도와 크기를 가진 구형 입자로 모델링됩니다. Marangoni 유동 효과를 비교하기 위해 이 연구는 표면 장력 구배가 다른 두 가지 사례 (양수 및 음수)를 조사했습니다. 수치 시뮬레이션과 실험 결과 모두 음의 표면 장력 구배가 비드 가장자리에 갇힌 슬래그를 형성하는 반면 양의 표면 장력 구배는 상단 표면의 중앙에 갇힌 슬래그를 형성하는 것으로 나타났습니다.

This study analyzed the behavior of molten slag, which is an oxide generated during spray mode gas metal arc welding, with computational fluid dynamics. The molten slag, composed mainly of silicate (SiO2), is located on the molten pool surface. It is generally assumed that the molten slag is generated around the arc plasma boundary. Therefore, in the numerical simulation in this study the slag is modeled as a spherical particle, which has a specific density and size. To compare the Marangoni flow effect, this study investigated two different cases where the surface tension gradients were different (positive and negative). In both the numerical simulation and experimental results it was found that negative surface tension gradient formed trapped slag on the bead edge while the positive surface tension gradient formed trapped slag on the center of the top surface.

Numerical simulation of slag movement from Marangoni flow for GMAW with computational fluid dynamics Figures
Numerical simulation of slag movement from Marangoni flow for GMAW with computational fluid dynamics Figures
Weld bead surface images showing the slag formation location for (a) wire 1 and (b) wire 2.

The effect of alloying elements of gas metal arc welding (GMAW) wire on weld pool flow and slag formation location in cold metal transfer (CMT)

가스 금속 아크 용접 (GMAW) 와이어의 합금 원소가 CMT (Cold Metal Transfer)에서 용접 풀 흐름 및 슬래그 형성 위치에 미치는 영향

Md. R. U. Ahsan1,3, Muralimohan. Cheepu2, Yeong-Do Park* 2,3
1Department of Mechanical Engineering, International University of Business, Agriculture and Technology,
Dhaka 1230, Bangladesh.
r.ahsan06me@gmail.com
2Department of Advanced Materials and Industrial Management Engineering, Dong-Eui University, Busan
47340, Republic of Korea.
muralicheepu@gmail.com
3Department of Advanced Materials Engineering, Dong-Eui University, B

Abstract

용접시 표면 장력 구동 흐름 또는 마랑고니 흐름은 용접 비드 모양을 제어하는데 중요한 역할을 하므로 용접 접합 품질에 영향을 미칩니다. 용해된 금속의 표면 장력은 보통 음의 온도 계수를 가지므로 용접 풀이 중심에서 토우 방향으로 흐르게 됩니다.

표면 장력의 이 온도 계수는 황(S), 산소(O), 셀레늄(Se) 및 텔루륨(Te)과 같은 표면 활성 요소가 있는 경우 양의 계수로 변경할 수 있습니다. 소모품에 존재하는 탈산화 원소의 양이 용접 금속에 존재하는 산소량을 결정합니다. 탈산화제 양이 적으면 용접 금속에 산소 농도가 높아집니다.

적절한 양의 산소가 있으면 용융지에 표면 장력 구배의 양의 온도 계수가 발생할 수 있습니다. 이 경우 용접 풀은 토우에서 중앙 방향으로 흐릅니다. 그 결과, 아크와 용융지에 있는 화농성 반응의 경우, 합금 요소의 다양한 산화물이 슬래그(slag)라고 합니다. 슬래그는 용융지 표면에 떠서 용융지 흐름 패턴에 따라 누적됩니다.

그 결과, 슬래그는 용융지 흐름 패턴에 따라 용접 비드 중심 또는 토우 중심을 따라 형성됩니다. 슬래그는 용접 비드의 외관과 도장 접착력을 저하시키므로 제거해야 합니다. 쉽게 분리할 수 있기 때문에 용접 비드 중심 부근에서 슬래그가 형성되는 것이 좋습니다.

용접 풀의 현장 고속 비디오 촬영, 용접 금속 화학 성분 분석, 소모품 합금 요소가 용접 풀 흐름 패턴 및 슬래그 형성 위치에 미치는 영향이 공개되어 CMT-GMAW의 생산성 향상을 위해 용접 소모품 선택을 용이하게 할 수 있습니다.

The surface tension driven flow or Marangoni flow in welding plays an important role in governing weld bead shape hence affecting the weld joint quality. The surface tension of molten metal usually has a negative temperature coefficient causing the weld pool to flow from the center towards the toe.

This temperature coefficient of the surface tension can be altered to be a positive one in the presence of surface-active elements like sulfur (S), oxygen (O), selenium (Se) and tellurium (Te). The amount of deoxidizing elements present in the consumables governs the amount of oxygen present in the weld metal. The presence of a lower amount of deoxidizers results in higher concentration of oxygen in the weld metal.

The presence of adequate amount of oxygen can result in a positive temperature coefficient of surface tension gradient in the weld pool. In such situation, the weld pool flows from the toe towards the direction of the center. As a result, of pyrometallurgical reactions in the arc and the weld pool various oxides of the alloying elements are former which are referred as slag.

The slags float on the weld pool surface and accumulate following the weld pool flow pattern. As a result, slags form either along the center of the weld bead or the toe depending on the weld pool flow pattern. The slags need to be removed as they degrade the weld bead appearance and paint adhesiveness.

Due to easy detachability, slag formation near the center of the weld bead is desired. From in-situ high-speed videography of weld pool, weld metal chemical composition analysis, the effect of consumables alloying elements on weld pool flow pattern and slag formation location are disclosed, which can facilitate the selection of the welding consumables for better productivity in CMT-GMAW.

Weld bead surface images showing the slag formation location for (a) wire 1 and (b) wire 2.
Weld bead surface images showing the slag formation location for (a) wire 1 and (b) wire 2.
Fig. 2: High-speed movie frames and schematic showing the weld pool flow pattern and the slag formation location for wire 1 and wire 2.
Fig. 2: High-speed movie frames and schematic showing the weld pool flow pattern and the slag formation location for wire 1 and wire 2.
Fig. 3: Quantitative analysis data on slag formation for different wire.
Fig. 3: Quantitative analysis data on slag formation for different wire.

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Figure 2. Experimental setups for the (a) Al/Cu overlap joint and (b) laser welding process.

Investigation on Laser Welding of Al Ribbon to Cu Sheet: Weldability, Microstructure, and Mechanical and Electrical Properties

알루미늄 리본과 구리 시트의 레이저 용접에 대한 조사 : 용접성, 미세 구조, 기계적 및 전기적 특성

Won‐Sang Shin 1,†, Dae‐Won Cho 2,†, Donghyuck Jung 1, Heeshin Kang 3, Jeng O Kim 3, Yoon‐Jun Kim 1,*
and Changkyoo Park 3,*

Al 리본과 Cu 시트의 펄스 레이저 용접은 전력 전자 모듈의 전기적 상호 연결에 대해 조사되었습니다. 결함 없는 Al / Cu 조인트를 얻기 위해 레이저 출력, 스캔 속도 및 열 입력이 서로 다른 다양한 실험 조건이 사용되었습니다. Al / Cu 레이저 용접 중에 금속 간 화합물이 용접 영역에 형성되었습니다. 전자 탐침 마이크로 분석기와 투과 전자 현미경으로 Al4Cu9, Al2Cu, AlCu 등으로 밝혀진 금속 간 화합물의 상을 확인했습니다. 전산 유체 역학 시뮬레이션은 Marangoni 효과가 용융 풀의 순환을 유도하여 혼합물을 생성하는 것으로 나타났습니다. Al과 Cu의 결합과 Al / Cu 조인트에서 소용돌이 모양의 구조 형성. Al / Cu 접합부의 인장 전단강도와 전기 저항을 측정하였으며 용접 면적과 강한 상관 관계를 보였다. Al / Cu 접합부의 용접 면적이 증가함에 따라 기계적 강도의 감소와 전기 저항의 증가가 측정 되었습니다. 또한 무결점 Al / Cu 접합을 위한 공정 창을 개발하고 Al / Cu 레이저 브레이즈 용접을 위한 실험 조건을 조사하여 Al / Cu 접합에서 금속 간 화합물 형성을 최소화했습니다.

Introduction

전기 상호 연결은 전력 전자 모듈을 패키징하는 데 중요합니다. 우수한 기계적 및 전기적 특성을 가진 견고한 전기적 상호 연결은 전력 전자 모듈의 전기적 고장을 방지하는 데 필수적입니다. 저항 스폿 용접, 브레이징, 납땜 및 초음파 용접 (USW)이 전기 상호 연결에 사용되었습니다.

납땜과 납땜 모두 저온 공정으로 인해 접합부에서 한계 변형과 잔류 응력이 발생합니다 [1]. 필러 합금은 두 공정 모두 견고한 전기 접촉을 달성하는 데 필수적입니다. 따라서 조인트는 서로 접촉하는 서로 다른 금속으로 구성됩니다.

결과적으로 조인트는 부식 환경에서 갈바닉 부식에 취약 할 수 있습니다 [2,3]. 더욱이, 비금속과 충전재 사이의 친화도를 고려해야 하기 때문에 제한된 충전재 만 특정 조인트에 사용할 수 있습니다 [1]. USW는 용접 온도가 낮고 용접 시간이 짧기 때문에 접합부의 변형이 비교적 적습니다.

따라서 이는 특히 연질 재료 (예 : Al, Cu, Ag, Au 및 Ni)의 경우 기존 접합 방법을 대체하고 있습니다 [4–6]. 그러나 Cu를위한 USW 공정의 경우, 표면 산화물이 강해 용접성이 저하되는 것을 방지하기 위해 Cu 표면에 Sn 또는 Ni 코팅이 필요하며, 이는 공정 속도를 늦추고 산업적 응용을위한 경제적 측면을 악화시킨다 [7 , 8].

레이저 용접은 쉬운 제어, 고정밀 및 원격 처리의 특성으로 인해 전력 전자 모듈의 전기 연결에 대한 유망한 후보입니다. 열의 영향을 받는 작은 영역과 변형은 전기 접점의 손상을 최소화 할 것으로 예상됩니다 [9-11]. 또한 레이저 용접을 위해 추가 표면 준비가 필요하지 않습니다.

이종 재료의 용접은 산업 응용 분야에서 중요했습니다. 더욱이 그림 1 [12,13]에서 볼 수 있듯이 전기 연결을위한 와이어 또는 리본 본딩에 여러 다른 조인트가 필요하기 때문에 전력 전자 모듈에서 필수적인 기술이되고 있습니다.

전기 접점의 다양한 조합 중에서 Al과 Cu는 높은 전기 전도성으로 인해 전기 연결에 중요한 재료로 종종 간주됩니다 [14]. 그러나 Al과 Cu의 서로 다른 용접은 금속 간 화합물 (IMC)의 형성을 촉진하고 동시에 Al / Cu 조인트의 기계적 및 전기적 특성에 영향을 줍니다. 일반적으로 Al / Cu 조인트 내부에 IMC가 있으면 연성 및 전기 저항에 해를 끼치므로 균열이 쉽게 발생하고 용접을 통한 전기 전도도를 방해합니다 [15,16].

따라서 견고한 Al / Cu 조인트를 얻으려면 IMC의 형성을 피해야합니다. 여러 연구에서 Al 및 Cu 시트의 레이저 빔 용접을 조사했습니다. 연속파 (CW) 레이저가 Al / Cu 조인트에 사용되었습니다 [17-23]. 큰 열 입력과 상당한 IMC 형성으로 인해 용접 영역에서 많은 균열이 관찰되었습니다 [18,19].

CW 레이저 빔의 공간 진동은 Al / Cu 조인트의 용접 품질을 향상시키는 것으로 나타났습니다. 직선 CW 레이저 빔 [18-20]과 비교하여 용접 영역에서 IMC 크기가 더 작은 기공과 균열이 더 적습니다.

Al과 Cu 시트의 겹침 접합에는 CW 단일 모드 파이버 레이저를 사용했으며, IMC 형성을 억제하여 높은 용접 속도 (즉, 50m / min)에서 견고한 Al / Cu 접합을 얻었습니다 [22]. Mai et al. [23]은 다른 Al / Cu 용접을 달성하기 위해 펄스 레이저를 사용했습니다.

그들은 Al / Cu 용접성이 레이저 공정 매개 변수에 크게 의존한다는 것을 밝혔으며 100mm / min 미만의 스캔 속도에서 균열없는 Al / Cu 접합을 달성하는 데 성공했습니다.

본문 내용 생략 : 문서 하단부의 원문보기를 참고하시기 바랍니다.

Figure 1. Schematic diagram of the insulated gate bipolar transistors (IGBT) power module. Red‐dotted box indicated the electrical connections
Figure 1. Schematic diagram of the insulated gate bipolar transistors (IGBT) power module. Red‐dotted box indicated the electrical connections
Figure 2. Experimental setups for the (a) Al/Cu overlap joint and (b) laser welding process.
Figure 2. Experimental setups for the (a) Al/Cu overlap joint and (b) laser welding process.
Figure 3. Schematic diagram of the numerical simulation domain and boundary conditions.
Figure 3. Schematic diagram of the numerical simulation domain and boundary conditions.
Figure 4. Experimental setup for the four‐point electrical resistance measurement.
Figure 4. Experimental setup for the four‐point electrical resistance measurement.
Figure 5. Cross‐sectional OM image of the Al/Cu joints in parallel to the laser welding direction. The laser power and scan speed were set at 2300 W and 20 mm/s, respectively.
Figure 5. Cross‐sectional OM image of the Al/Cu joints in parallel to the laser welding direction. The laser power and scan speed were set at 2300 W and 20 mm/s, respectively.
Figure 6 shows the cross‐sectional SEM images of the Al/Cu joints, and corresponding EPMA element mapping of Al and Cu for the (a) 23/20, (b) 25/28.6, (c) 25/15.4, and (d) 27/20.
Figure 6 shows the cross‐sectional SEM images of the Al/Cu joints, and corresponding EPMA element mapping of Al and Cu for the (a) 23/20,
Figure 6. Cross‐sectional SEM image and elemental distribution mapping of Al and Cu elements for the (a) 23/20, (b) 25/28.6, (c) 25/15.4, and (d) 27/20.
Figure 6. Cross‐sectional SEM image and elemental distribution mapping of Al and Cu elements for the (d) 27/20.
Figure 7. EPMA line scan analysis and identification of the IMCs for the (a) 23/20 and (b) 25/15.4.
Figure 7. EPMA line scan analysis and identification of the IMCs for the (a) 23/20 and (b) 25/15.4.
Figure 8. TEM analysis for the 25/28.6. (a) Indicating the location of TEM analysis in SEM image of the welding zone. (b) TEM bright‐field image and SAED pattern insets, examined at the location (1) in figure (a), confirmed Al‐rich phase (white globular shape) and Al2Cu eutectic phase (gray region), and (c) TEM bright‐field image and SAED pattern inset of Al4Cu9, examined at the location (2) in figure (a).
Figure 8. TEM analysis for the 25/28.6. (a) Indicating the location of TEM analysis in SEM image of the welding zone. (b) TEM bright‐field image and SAED pattern insets, examined at the location (1) in figure (a), confirmed Al‐rich phase (white globular shape) and Al2Cu eutectic phase (gray region), and (c) TEM bright‐field image and SAED pattern inset of Al4Cu9, examined at the location (2) in figure (a).
Figure 9. Temperature profiles and molten pool flow on transverse cross‐section (y–z plane at x = 1.23 cm): (a) Negative surface tension gradient for the 23/20 (Case 1), (b) negative surface tension gradient for the 25/15.4 (Case 2), (c) positive surface tension gradient for the 25/15.4 (Case 3), and (d) without surface tension for the 25/15.4 (Case 4).
Figure 9. Temperature profiles and molten pool flow on transverse cross‐section (y–z plane at x = 1.23 cm): (a) Negative surface tension gradient for the 23/20 (Case 1), (b) negative surface tension gradient for the 25/15.4 (Case 2), (c) positive surface tension gradient for the 25/15.4 (Case 3), and (d) without surface tension for the 25/15.4 (Case 4).
Figure 12. Results of the tensile shear tests for the (a) 23/20: fracture at the Al ribbon and (b) 25/15.4: fracture at the weld
Figure 12. Results of the tensile shear tests for the (a) 23/20: fracture at the Al ribbon and (b) 25/15.4: fracture at the weld
Figure 13. Stress–strain curves obtained by the tensile shear tests.
Figure 13. Stress–strain curves obtained by the tensile shear tests.

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Fig. 9 (a) Velocity field, keyhole profile, and breakage of the keyhole to form bubble and (b) 2D temperature and velocity field along the longitudinal section

A Numerical Study on the Keyhole Formation During Laser Powder Bed Fusion Process

Keyhole에 대한 수치적 연구 : 레이저 분말 중 형성 베드 퓨전 공정

Subin Shrestha1
J.B. Speed School of Engineering,University of Louisville,Louisville, KY 40292
e-mail: subin.shrestha@louisville.edu

Y. Kevin Chou
J.B. Speed School of Engineering,University of Louisville,Louisville, KY 40292
e-mail: kevin.chou@louisville.edu

LPBF (Laser Powder Bed fusion) 공정 중 용융 풀의 동적 현상은 복잡하고 공정 매개 변수에 민감합니다. 에너지 밀도 입력이 특정 임계 값을 초과하면 키홀이라고 하는 거대한 증기 함몰이 형성 될 수 있습니다.

이 연구는 수치 분석을 통해 LPBF 과정에서 키홀 거동 및 관련 기공 형성을 이해하는 데 중점을 둡니다. 이를 위해 이산 분말 입자가 있는 열 유동 모델이 개발되었습니다.

이산 요소 방법 (DEM)에서 얻은 분말 분포는 계산 영역에 통합되어 FLOW-3D를 사용하는 3D 프로세스 물리학 모델을 개발합니다.

전도 모드 중 용융 풀 형성과 용융의 키홀 모드가 식별되고 설명되었습니다. 높은 에너지 밀도는 증기 기둥의 형성으로 이어지고 결과적으로 레이저 스캔 트랙 아래에 구멍이 생깁니다.

또한 다양한 레이저 출력과 스캔 속도로 인한 Keyhole 모양을 조사합니다. 수치 결과는 동일한 에너지 밀도에서도 레이저 출력이 증가함에 따라 Keyhole크기가 증가 함을 나타냅니다. Keyhole은 더 높은 출력에서 ​​안정되어 레이저 스캔 중 Keyhole 발생을 줄일 수 있습니다.

The dynamic phenomenon of a melt pool during the laser powder bed fusion (LPBF) process is complex and sensitive to process parameters. As the energy density input exceeds a certain threshold, a huge vapor depression may form, known as the keyhole. This study focuses on understanding the keyhole behavior and related pore formation during the LPBF process through numerical analysis. For this purpose, a thermo-fluid model with discrete powder particles is developed. The powder distribution, obtained from a discrete element method (DEM), is incorporated into the computational domain to develop a 3D process physics model using flow-3d. The melt pool formation during the conduction mode and the keyhole mode of melting has been discerned and explained. The high energy density leads to the formation of a vapor column and consequently pores under the laser scan track. Further, the keyhole shape resulted from different laser powers and scan speeds is investigated. The numerical results indicated that the keyhole size increases with the increase in the laser power even with the same energy density. The keyhole becomes stable at a higher power, which may reduce the occurrence of pores during laser scanning.

Keywords: additive manufacturing, keyhole, laser powder bed fusion, porosity

Fig. 1 (a) Powder added to the dispenser platform and (b) powder particles settled over build plate after the recoating process
Fig. 1 (a) Powder added to the dispenser platform and (b) powder particles settled over build plate after the recoating process
Fig. 2 3D computational domain used for single-track simulation
Fig. 2 3D computational domain used for single-track simulation
Fig. 3 Temperature-dependent material properties of Ti-6Al-4V
Fig. 3 Temperature-dependent material properties of Ti-6Al-4V
Fig. 4 Powder and substrate melting during laser application
Fig. 4 Powder and substrate melting during laser application
Fig. 5 Melt region formed after complete melting and solidification
Fig. 5 Melt region formed after complete melting and solidification
Fig. 6 Melt pool boundary comparison between the experiment [25] and the simulation
Fig. 6 Melt pool boundary comparison between the experiment [25] and the simulation
Fig. 7 Equilibrium points during the formation of vapor column [27]
Fig. 7 Equilibrium points during the formation of vapor column [27]
Fig. 8 Multiple reflection vectors from the keyhole wall
Fig. 8 Multiple reflection vectors from the keyhole wall
Fig. 9 (a) Velocity field, keyhole profile, and breakage of the keyhole to form bubble and (b) 2D temperature and velocity field along the longitudinal section
Fig. 9 (a) Velocity field, keyhole profile, and breakage of the keyhole to form bubble and (b) 2D temperature and velocity field along the longitudinal section
Fig. 10 Fluid flow in the transverse direction during keyhole melting
Fig. 10 Fluid flow in the transverse direction during keyhole melting
Fig. 11 Melt pool boundary compared with the experiment [21] for 195 W laser power and 400 mm/s scan speed
Fig. 11 Melt pool boundary compared with the experiment [21] for 195 W laser power and 400 mm/s scan speed
Fig. 12 Melt region formed after complete melting and solidification
Fig. 12 Melt region formed after complete melting and solidification
Fig. 13 2D images of the pores formed at the beginning of the single track and their 3D-rendered morphology
Fig. 13 2D images of the pores formed at the beginning of the single track and their 3D-rendered morphology
Fig. 14 Pore number and volume from a different level of power with LED = 0.4 J/mm [29]
Fig. 14 Pore number and volume from a different level of power with LED = 0.4 J/mm [29]
Fig. 15 Keyhole shape at different time steps from different parameters: (a) P = 100 W, v = 250 mm/s, (b) P = 200 W, v = 500 mm/s, (c) P = 300 W, v = 750 mm/s, and (d) P = 400 W, v = 1000 mm/s
Fig. 15 Keyhole shape at different time steps from different parameters: (a) P = 100 W, v = 250 mm/s, (b) P = 200 W, v = 500 mm/s, (c) P = 300 W, v = 750 mm/s, and (d) P = 400 W, v = 1000 mm/s
Fig. 16 Intensity dependence in the relationship between vapor column and evaporation pressure [27]
Fig. 16 Intensity dependence in the relationship between vapor column and evaporation pressure [27]
Fig. 17 Temperature distribution when laser has moved 0.8 mm with P = 300 W, v = 750 mm/s and P = 400 W, v = 1000 mm/s
Fig. 17 Temperature distribution when laser has moved 0.8 mm with P = 300 W, v = 750 mm/s and P = 400 W, v = 1000 mm/s
Fig. 18 Melt region with different level of power with LED of 0.4 J/mm
Fig. 18 Melt region with different level of power with LED of 0.4 J/mm

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Figure 5.6 Experimental set-up equipped with high-speed camera system

COMPUTATIONAL FLUID DYNAMIC MODELLING OF LASER ADDITIVE MANUFACTURING PROCESS AND EFFECT OF GRAVITY

전산 유체 역학 레이저 첨가제 모델링 제조 공정 및 중력의 영향

A thesis submitted to
The University of Manchester
For the degree of
Doctor of Philosophy (PhD)
In the Faculty of Science and Engineering
2017
Heng Gu
School of Mechanical, Aerospace and Civil
Engineering

레이저 적층 제조 (LAM)는 재료를 층별로 선택적으로 추가하여 하나 또는 여러 개의 레이저 빔을 사용하여 재료를 융합하거나 응고시키는 3D 부품을 형성하는 것을 기반으로 합니다.

LAM 공정을 조사하는 데 상당한 양의 작업을 할 수 있지만 다른 재료 성장 방향에서 중력 및 동적 유체 흐름 특성의 영향에 대해서는 알려진 바가 거의 없습니다.

레이저 제조 기술의 발전과 함께 LAM은 실린더 본체, 터빈 블레이드의 표면 클래딩, 해양 드릴링 헤드, 다양한 증착 방향이 일반적으로 필요한 슬리브 및 몰드의 측벽을 비롯한 다양한 환경에서 점점 더 많이 사용되고 있습니다. 또한 공간 적층 제조의 경우 운영 환경이 매우 낮거나 무중력을 경험하게 됩니다.

LAM 프로세스를 모델링하기 위한 수치적 방법 개발에 대한 이전 연구에서 많은 노력을 기울였습니다. 그러나 이전 모델링 작업의 대부분은 자유 표면 형성을 고려하지 않고 용융 풀 역학 개발에 초점을 맞추었습니다. 몇 가지 조사에만 동적 유동 용융 풀에 대한 재료 추가 분석이 포함됩니다.

다양한 재료 증착 방향 및 무중력 효과에서 수행 할 때 모든 복잡한 기능을 사용하여 증착 프로세스를 시뮬레이션하고 중력 효과를 고려할 수 있는 모델을 개발하는 작업은 발견되지 않았습니다.

이 연구에서는 재료 추가, 표면 장력, 용융 및 응고, 중력, 온도 의존 재료 속성, 자유 표면 형성 및 이동을 포함한 복합 공정 요인을 고려한 LAM 공정을 위해 3 차원 과도 전산 유체 역학 모델이 ​​구축되었습니다. 열원. 레이저 금속 증착 공정에 대한 더 나은 이해는 수치적으로 그리고 실험적으로 이루어졌습니다.

이 연구는 단일 레이어의 증착, 여러 인접 패스 및 돌출 된 피쳐가 있는 완전한 3 차원 형상을 다루었습니다. 증착 공정 중 다양한 증착 방향과 무중력 및 매우 낮은 중력에 대한 중력의 영향을 조사하고 그 영향을 최소화하기 위해 공정 매개 변수를 최적화 했습니다.

이 연구는 또한 층별 재료 추가를 기반으로 레이저 좁은 갭 용접 공정의 기본 현상과 용접 공정이 다른 방향으로 수행 될 때 중력이 홈 내부의 용융 풀 형성에 미치는 영향을 이해하는 데까지 확장되었습니다.

용융 풀 개발 이력 및 온도 분포를 분석하여 공정 중에 표면 장력 계수의 영향을 논의했습니다. 현재 모델의 도움으로 증착 불균일성, 증착 양단의 돌출부, 경사, 융착 부족, 계단 효과, 표면 파형, 중력 변화로 인한 붕괴 등 다양한 결함을 설명 하였습니다.

이러한 모든 결함을 제거하기 위한 해당 솔루션이 제시되었습니다. 무중력 레이저 적층 제조에 대한 연구는 이전에 보고되지 않았던 몇 가지 새로운 현상을 발견하여 우주에서 미래의 레이저 3D 프린팅을 위한 길을 닦았습니다.

Figure 1.1 Diagram for thesis structure
Figure 1.1 Diagram for thesis structure
Figure 2.1 Basic construction of a laser system [8]
Figure 2.1 Basic construction of a laser system [8]
Figure 2.3 Schematic of a diode laser system [12]
Figure 2.3 Schematic of a diode laser system [12]
Figure 2.4 Principle of a cladding pumped fibre laser [13]
Figure 2.4 Principle of a cladding pumped fibre laser [13]
Figure 2.5 Concept of a thin disk laser [14]
Figure 2.5 Concept of a thin disk laser [14]
Figure 2.7 Lateral powder injection [12]
Figure 2.7 Lateral powder injection [12]
Figure 2.9 Laser additive manufacturing using wire, (a) front feeding, (b) rear feeding,  wire placed at (c) leading edge, (d) centre and (e) trailing edge of melt pool [23, 24]
Figure 2.9 Laser additive manufacturing using wire, (a) front feeding, (b) rear feeding, wire placed at (c) leading edge, (d) centre and (e) trailing edge of melt pool [23, 24]
Figure 2.20 Bead geometry at the beginning of the deposition with different surface  tension gradient (a) Negative, (b) positive, (c) Mixed [85]
Figure 2.20 Bead geometry at the beginning of the deposition with different surface tension gradient (a) Negative, (b) positive, (c) Mixed [85]
Figure 2.22 Simulation of humping effect in high-speed gas tungsten arc welding [91]
Figure 2.22 Simulation of humping effect in high-speed gas tungsten arc welding [91]
Figure 2.25 (a) Melt pool shape formed by Marangoni stress only, (b) Melt pool shape  formed by gravity force only, (c) Melt shape formed by the combination of those two  forces together [122]
Figure 2.25 (a) Melt pool shape formed by Marangoni stress only, (b) Melt pool shape formed by gravity force only, (c) Melt shape formed by the combination of those two forces together [122]
Figure 2.27 Growth rate and temperature gradient on solidification boundary with  different melt pool shape [120]
Figure 2.27 Growth rate and temperature gradient on solidification boundary with different melt pool shape [120]
Figure 2.29 Two different methods to produce overhang structures[136]
Figure 2.29 Two different methods to produce overhang structures[136]
Figure 2.30 Contact angle of a water droplet adhering on a glass window [142]
Figure 2.30 Contact angle of a water droplet adhering on a glass window [142]
Figure 2.31 Stress components of a single track laser deposition (a) x-direction, (b) ydirection, (c) z-direction, (d) von Mises equivalent stress [151]
Figure 2.31 Stress components of a single track laser deposition (a) x-direction, (b) ydirection, (c) z-direction, (d) von Mises equivalent stress [151]
Figure 2.32 Phase fraction of martensite during laser metal deposition [160]
Figure 2.32 Phase fraction of martensite during laser metal deposition [160]
Figure 4.15 Development of melt pool and velocity field 0.588 s, 1.2 s, 1.896 s, 2.4 s
Figure 4.15 Development of melt pool and velocity field 0.588 s, 1.2 s, 1.896 s, 2.4 s
Figure 4.33 Two methods to print C, (A) raster (B) offset out
Figure 4.33 Two methods to print C, (A) raster (B) offset out
Figure 5.4(a) Cavitar laser illumination system (b) High-speed camera in horizontal  position
Figure 5.4(a) Cavitar laser illumination system (b) High-speed camera in horizontal position
Figure 5.5 Schematic diagrams of wire laser deposition process (a) flat (b) vertical
Figure 5.5 Schematic diagrams of wire laser deposition process (a) flat (b) vertical
Figure 5.6 Experimental set-up equipped with high-speed camera system
Figure 5.6 Experimental set-up equipped with high-speed camera system
Figure 5.7 2-layer deposition result and cross-section (a) top view, (b) experimental  cross section, (c) cross-section of modelling result
Figure 5.7 2-layer deposition result and cross-section (a) top view, (b) experimental cross section, (c) cross-section of modelling result
Figure 5.13 Temperature and melt pool-velocity field history for case 8, (a&f:0.36 s,  b&g:1.44 s, c&h:1.80 s, d&i:1.908 s, e&j:2.196 s)
Figure 5.13 Temperature and melt pool-velocity field history for case 8, (a&f:0.36 s, b&g:1.44 s, c&h:1.80 s, d&i:1.908 s, e&j:2.196 s)
Figure 5.16 Comparison of melt pool evolution for cases with big and small spot size
Figure 5.16 Comparison of melt pool evolution for cases with big and small spot size
Figure 6.27 (a,b,c) before re-melting, (d,e,f) after re-melting
Figure 6.27 (a,b,c) before re-melting, (d,e,f) after re-melting

6.5 Conclusion

좁은 갭 용접 공정의 다양한 측면을 다루는 3 차원 모델이 구축되었습니다. 용접 비드와 측벽 사이의 융합 현상이 없는 것은 필러 재료와 측벽을 녹일 수 있는 충분한 에너지를 제공 할 수 없는 낮은 열 입력으로 인한 것일 수 있습니다.

증가된 레이저 출력을 적용하거나 재 용융 패스를 수행 한 후 더 나은 표면 품질을 얻을 수 있고 측벽과의 융합 부족을 제거 할 수 있습니다. 용접 비드의 모양이 볼록한 모양에서 오목한 모양으로 바뀌고 측면 벽과의 좋은 젖음이 실현 될 수 있습니다.

다양한 위치에서 좁은 틈새 용접에 대한 중력의 영향을 조사했습니다. 용융 풀 전면의 경사 모양은 중력의 영향으로 다르게 나타납니다.

반면, 홈이 없는 기판의 증착 공정과 비교할 때 대부분의 열을 전달하는데 도움이 되는 측벽의 존재로 인해 중력의 영향이 감소했습니다.

마지막 패스 중에 중력은 일부 평평하지 않은 위치에서 심각한 낙하 및 붕괴 문제를 일으킬 수 있습니다. 이것은 표면에 더 큰 용융 풀이 형성되어 중력과 표면 장력 사이의 균형이 깨졌기 때문입니다. 수직 업 위치에서 좁은 간격 용접 공정 동안 다른 중력 수준이 적용되었습니다.

용접 비드와 측벽 사이의 융합 부족은 중력 수준이 증가함에 따라 관찰 될 수 있습니다. 중력이 증가하면 용융 풀의 뒤쪽 영역으로 더 많은 액체 재료가 이동하여 더 심각한 물방울과 볼록한 모양의 용접 비드가 발생합니다.

용융 풀 개발 이력의 도움으로 용접 비드가 더 이상 그루브에 있지 않거나 측벽과의 직접적인 접촉이 적을 때 전도를 통해 더 적은 열이 방출 될 수 있기 때문에 용융 풀 부피가 크게 증가한다는 것을 알 수 있습니다.

좁은 간격 용접 공정에 대한 표면 장력 계수의 영향을 조사했습니다. 양의 표면 장력 계수를 적용하면 용접 비드가 홈 내부에서 덜 오목한 것처럼 보였고 측벽의 습윤 조건이 음의 ∂γ / ∂T 조건의 경우만큼 좋지 않았습니다.

측벽이 없으면 용접 비드는 표면의 마지막 패스 동안 음의 계수와 양의 계수 케이스 사이에 더 많은 차이를 보여줍니다. 표면 장력 계수는 홈 내부의 측벽과의 융합 상태를 결정하는 데 중요한 역할을 했습니다.

두꺼운 부분의 좁은 틈새 용접 중에 여러 번 통과하는 용접 비드 개발이 조사되었습니다. 비드 모양은 열 축적으로 인해 더 많은 패스가 증착 될수록 더 오목 해집니다. 패스 간의 융합 부족은 때때로 다음 패스의 재 용융 공정을 통해 제거 될 수 있습니다. 이종 재료를 사용한 좁은 틈새 용접 프로세스가 성공적으로 시뮬레이션되었습니다.

중심선을 따라 용융 풀과 용접 비드의 비대칭 형성은 재료 열 특성의 차이에 기인 할 수 있으며, 결과적으로 측벽과의 융합 부족을 유발할 수 있습니다.

비드 비대칭 문제는 수평 위치에서 용접 공정을 수행하거나 총 열 입력을 증가시켜 열전도율이 높은 측벽을 녹이는 방식으로 피할 수 있습니다. 재 용융 공정은 표면 품질을 향상시키고 모재와의 융착 문제를 제거하기 위해 용접된 표면에 적용 할 때 유용한 것으로 밝혀졌습니다.

Figure 8 Evaluation test of thermal sprayed coatings

Development of Advanced Materials and Manufacturing Technologies for High-efficiency Gas Turbines

고효율 가스 터빈용 신소재 및 제조 기술 개발

Mitsubishi Heavy Industries Technical Review Vol. 52 No. 4 (December 2015)

가스 터빈 복합 화력 (GTCC) 발전 시장은 재생 에너지와 공존 할 수 있는 가장 깨끗하고 경제적인 화력 발전 시스템으로 장기적으로 성장할 것으로 예상됩니다. 효율성을 더욱 높이려면 터빈 부품 재료의 특성을 개선하고 첨단 블레이드 설계에 필요한 복잡한 구조를 구축하기 위한 제조 기술 개발이 필수적입니다.

이 보고서는 가스 터빈의 고온 적용을 위한 재료 및 제조 기술로서 합금 설계 및 주조, 코팅, 용접 수리 및 냉각 구멍 드릴링 공정을 포함한 기술 개발을 제시합니다.

최근 몇 년 동안 세계 에너지 수요는 특히 중국과 인도와 같은 아시아 국가에서 현저하게 증가하고 있습니다. 2035 년 글로벌 에너지 소비량은 2010 년 대비 약 1.5 배 수준에이를 것으로 예상됩니다. 일본에서는 에너지 자급률이 10 % 미만이며 에너지 사용 효율을 높이고 환경 부하를 줄이는 것이 시급한 문제입니다. . 특히 현재 일본 전기 생산량의 거의 90 %를 차지하고있는 화력 발전의 효율화가 필요하다. 발전 효율은 가스 터빈 (시스템의 주요 구성 요소)의 연소 온도에 크게 영향을받습니다. 온도가 상승함에 따라 열 순환 효율이 향상 될 수 있기 때문에 Mitsubishi Hitachi Power Systems, Ltd.

(MHPS)는 1980 년대 초부터 더 높은 온도 / 더 나은 효율성 및 더 큰 용량을 가진 고급 시스템을 개발했습니다.
그림 11에서 보듯이 터빈 입구 온도는 1984 년 (Type D) 1,100 ° C 등급에서 시작하여 1989 년 1,350 ° C 등급 (Type F), 1997 년 1,500 ° C 등급 (Type 지).

또한 2011 년에는 1,600 ° C 급 가스 터빈 (J 형)이 출범했습니다 .2 2004 회계 연도부터 국가 프로젝트 “1,700 ° C 급 가스 터빈을위한 원소 기술 개발”이 시작되었습니다. J 형 가스 터빈 개발 프로젝트는 첨단 열 차단 코팅 (TBC) 및 냉각 / 공기 역학 기술과 같은 결과도 활용되었습니다 (그림 2).

가스 터빈 온도를 더욱 높이려면 이러한 고온을 견딜 수있는 신소재를 설계하고 터빈 부품의 특성을 개선하며 고급 블레이드 설계에 필요한 복잡한 구조를 구축하기 위한 제조 기술을 발명하는 것이 중요합니다.
이 보고서는 MHPS가 Mitsubishi Heavy Industries, Ltd. (MHI) 연구 및 혁신 센터와 함께 개발하고 있는 이러한 기술을 소개합니다.

 Figure 1    Increase in the turbine inlet temperature and transition of applied materials and technologies
Figure 1 Increase in the turbine inlet temperature and transition of applied materials and technologies
Characteristics of the M501J gas turbine
Characteristics of the M501J gas turbine

MHPS와 MHI는 MGA1400, MGA1400DS, MGA2400을 고온 환경에서 사용할 수 있을 만큼 내구성이 있는 고강도 Ni 계 초합금으로 개발하여 자사 제품에 적용하고 있습니다. 일반적으로 인터 빈 블레이드에 사용되는 초합금은 주조 방법에 따라 기존 주조 합금, 방향 응고 합금, 단결정 합금 중 하나로 분류됩니다.

이 세 가지 유형 중 MGA1400 및 MGA2400은 기존 주조 합금의 범주에 해당하는 반면 MGA1400DS는 방향성 응고 합금입니다 . 단결정 합금은 입자 경계가 없기 때문에 가장 강하고 (그 존재는 재료 강도 측면에서 불리 함) 입자 경계 강화를 고려하지 않고 합금 조성을 최적화 할 수 있습니다.

그러나 주조 공정에서 발생하는 주조 결함은 강도를 크게 저하시킬 수 있으므로 제조 기술의 확립이 중요합니다. 산업용 가스 터빈 블레이드는 크기가 크기 때문에 항공기 엔진보다 제조하기가 더 어렵습니다.

MHI 연구 혁신 센터는 1700 ° C 급 가스 터빈을 건설하기 위해 NIMS (National Institute for Materials Science)와 공동 연구를 수행하여 단결정 블레이드용 고내열 소재를 개발했습니다. 고온에서 재료의 강도를 검증하는 것 뿐만 아니라 결함이 없는 좋은 단결정 구조를 얻기 위한 주조 기술 개발도 필수적입니다.

신소재는 원재료 및 주조 비용 등 경제성 측면에서도 만족스러워야 한다. 또한 고온에서 필요한 모든 재료 특성 (예 : 크리프 강도, 열 피로 강도 및 내 산화성)을 나타내야 합니다. 특히 크리프 강도와 열 피로 강도의 공존을 실현하기 위한 기술 개발이 어려웠습니다.

NIMS 합금 설계 프로그램에 의해 결정된 조성으로 테스트 합금을 조사하는 동안 MHI와 NIMS는 속성 예측을 위한 데이터베이스를 확장하기 위해 주로 열 피로 강도에 대한 데이터를 수집했습니다. 이러한 노력으로 인해 크리프 강도와 열 피로 강도 모두에서 우수한 특성을 가진 단결정 합금 인 MGA1700이 개발되었습니다 (그림 3).

일반적으로 레늄과 같은 고가의 희귀 금속을 포함하는 고강도의 다른 단결정 합금과 달리 MGA1700은 콘없이 고강도를 실현하는 획기적인 합금입니다.

 Figure 3    Micro structure and high-temperature strength property of the designed alloy
Figure 3 Micro structure and high-temperature strength property of the designed alloy
   Figure 8    Evaluation test of thermal sprayed coatings
Figure 8 Evaluation test of thermal sprayed coatings
 Figure 11    Schematic diagram of LMD Figure 13    Cross-sectional comparison of weld beads between analysis results and LMD application      Figure 12    Analytical model and a typical result of the analysis
Figure 11 Schematic diagram of LMD Figure
Figure 12 Analytical model and a typical result of the analysis
13 Cross-sectional comparison of weld beads between analysis results and LMD application

중략 ……

References

1. Komori, T. et al., the 41th GTSJ Seminar material (2013) pp. 57-64 2. Yuri, M. et al., Development of 1600°C-Class High-efficiency Gas Turbine for Power Generation Applying J-Type Technology, Mitsubishi Heavy Industries Technical Review Vol. 50 No. 3 (2013) pp.1-10. 3. Okada, I. et al., Development of Ni base Superalloy for Industrial Gas Turbine, Superalloy2004,(2004),p707-712. 4. Kishi, K. et al., Welding Repair Technology for Single Crystal Blade and Vane,Proceedings of the International Gas Turbine Congress, (2014), IGTC07-116S. 5. KREUTZ, E.W. et al., Process Development and Control of Laser Drilled and Shaped Holes in TurbineComponents, JLMN-Journal of Laser Micro/Nanoengineering, Vol.2 No.2 (2007), p123. 6. Sezer, H.K. et al., Mechanisms of Acute Angle Laser Drilling induced Thermal Barrier CoatingDelamination,Journal of Manufacturing Science and Engineering, vol.131 (2009), p.051014-1 7. Goya, S. et al., High-Speed & High-Quality Laser Drilling Technology Using a Prism Rotator, MitsubishiHeavy Industries Technical Review Vol. 52 No. 1 (2015) pp. 106-109

Simulation Gallery

Simulation Gallery

Simulation Gallery | 시뮬레이션 갤러리

시뮬레이션 비디오 갤러리에서 FLOW-3D  제품군으로 모델링 할 수 있는 다양한 가능성을 살펴보십시오 .

적층 제조 시뮬레이션 갤러리

FLOW-3D AM 은 레이저 파우더 베드 융합, 바인더 제트 및 직접 에너지 증착과 같은 적층 제조 공정을 시뮬레이션하고 분석합니다. FLOW-3D AM 의 다중 물리 기능은 공정 매개 변수의 분석 및 최적화를 위해 분말 확산 및 압축, 용융 풀 역학, L-PBF 및 DED에 대한 다공성 형성, 바인더 분사 공정을 위한 수지 침투 및 확산에 대한 매우 정확한 시뮬레이션을 제공합니다. 

Multi-material Laser Powder Bed Fusion | FLOW-3D AM

Micro and meso scale simulations using FLOW-3D AM help us understand the mixing of different materials in the melt pool and the formation of potential defects such as lack of fusion and porosity. In this simulation, the stainless steel and aluminum powders have independently-defined temperature dependent material properties that FLOW-3D AM tracks to accurately capture the melt pool dynamics. Learn more about FLOW-3D AM’s mutiphysics simulation capabilities at https://www.flow3d.com/products/flow3…

Laser Welding Simulation Gallery

FLOW-3D WELD 는 레이저 용접 공정에 대한 강력한 통찰력을 제공하여 공정 최적화를 달성합니다. 더 나은 공정 제어로 다공성, 열 영향 영역을 최소화하고 미세 구조 진화를 제어 할 수 있습니다. 레이저 용접 공정을 정확하게 시뮬레이션하기 위해 FLOW-3D WELD 는 레이저 열원, 레이저-재료 상호 작용, 유체 흐름, 열 전달, 표면 장력, 응고, 다중 레이저 반사 및 위상 변화를 특징으로 합니다.

Keyhole welding simulation | FLOW-3D WELD

물 및 환경 시뮬레이션 갤러리

FLOW-3D 는 물고기 통로, 댐 파손, 배수로, 눈사태, 수력 발전 및 기타 수자원 및 환경 공학 과제 모델링을 포함하여 유압 산업에 대한 많은 응용 분야를 가지고 있습니다. 엔지니어는 수력 발전소의 기존 인프라 용량을 늘리고, 어류 통로, 수두 손실을 최소화하는 흡입구, 포 이베이 설계 및 테일 레이스 흐름을위한 개선 된 설계를 개발하고, 수세 및 퇴적 및 공기 유입을 분석 할 수 있습니다.

금속 주조 시뮬레이션 갤러리

FLOW-3D CAST  에는 캐스팅을 위해 특별히 설계된 광범위하고 강력한 물리적 모델이 포함되어 있습니다. 이러한 특수 모델에는 lost foam casting, non-Newtonian fluids, and die cycling에 대한 알고리즘이 포함됩니다. FLOW-3D CAST 의 강력한 시뮬레이션 엔진과 결함 예측을 위한 새로운 도구는 설계주기를 단축하고 비용을 절감 할 수 있는 통찰력을 제공합니다.

HPDC |Comparison of slow shot profiles and entrained air during a filling simulation |FLOW-3D CAST

Shown is a video comparing two slow shot profiles. The graphs highlight the shot profiles through time and the difference in entrained air between the slow shots. Note the lack of air entrained in shot sleeve with calculated shot profile which yields a much better controlled flow within the shot sleeve.

Coastal & Maritime Applications | FLOW-3D

FLOW-3D는 선박 설계, 슬로싱 다이내믹스, 파동 충격 및 환기 등 연안 및 해양 애플리케이션에 이상적인 소프트웨어입니다. 연안 애플리케이션의 경우 FLOW-3D는 연안 구조물에 심각한 폭풍과 쓰나미 파장의 세부 정보를 정확하게 예측하고 플래시 홍수 및 중요 구조물 홍수 및 손상 분석에 사용됩니다.

Laser Welding and Additive Manufacturing

Melt Pool Modeling: Innovation in Laser Welding & Additive Manufacturing

Melt Pool Modeling - Innovation in Laser Welding & Additive Manufacturing Webinar

Additive Manufacturing 기술이 새로운 제조 방식을 계속 발전시키면서 CFD 모델링은 공정 개발 및 최적화와, 재료의 변화를 이해하고, 설계 및 연구를 수행하는 매우 유용한 도구가 되었습니다. 이 웨비나에서는 최첨단 CFD 소프트웨어 FLOW-3D AM이 레이저 파우더 베드 융합 및 직접 에너지 증착 공정에서 용융 풀 역학을 모델링하는데 어떻게 사용되는지 살펴볼 것입니다. 그런 다음 유용한 정보를 얻기 위해 모델 데이터의 추출 및 분석에 집중하고 FLOW-3D AM에서 최근에 구현된 기능에 대해 논의합니다. 마지막으로 레이저 용접 및 적층 제조 응용 분야 모두에 적용할 수 있는 관련 산업 사례 연구를 검토하여 산업 응용 분야에 소프트웨어 사용을 보여줍니다.

https://www.facebook.com/FLOW3D.CFD.Software/videos/359103388813376/

Laser Metal Deposition Simulation | FLOW-3D AM | Facebook
Laser Metal Deposition Simulation | FLOW-3D AM | Facebook
FLOW-3D - We'll be presenting and exhibiting at the 2021
FLOW-3D – We’ll be presenting and exhibiting at the 2021

등록 링크https://zoom.us/webinar/register/7516034917241/WN_tik88gXJRzult2_HDNIzPA
산지 표준시(미국 및 캐나다)의 2021년 5월 5일 11:00 오전 (현지 시간)
이벤트 주최: FLOW-3D

발표자

photo of Paree Allu

Paree AlluSenior CFD Engineer @Flow Science, Inc.Paree Allu is a Senior CFD Engineer with Flow Science, where he leads the technical and business strategy for Flow Science’s additive manufacturing and laser welding software solutions. Paree holds a Master’s Degree in Mechanical Engineering from The Ohio State University.

photo of Allyce Jackman

Allyce JackmanCFD Engineer @Flow Science, Inc.Allyce Jackman is a CFD Engineer with Flow Science, where she specializes in laser welding, coating, and complex multiphysics applications. Allyce holds a Bachelor’s Degree in Mechanical Engineering from the University of New Mexico.

Pulsed Laser Welding

Pulsed Laser Welding | 펄스 레이저 용접

Pulsed Laser Welding

시뮬레이션 설명

펄스 레이저 용접은 레이저의 고출력 및 고속 주파수 펄스를 생성합니다. 이는 무엇보다도 열에 민감한 장비 주변의 용도에 도움이 될 수 있습니다. 이 예제는 FLOW-3D AM에서 이 효과를 모델링하는 방법을 보여줍니다. 이 시뮬레이션을 실행하려면 FLOW-3D WELD가 필요합니다.

시뮬레이션 세부 정보

버전#: FLOW-3D v11.2와 FLOW-3D WELD가 결합됨

본 사례에 대해 궁금하신 사항이 있으시면 언제든지 기술지원팀에 연락주세요.

Ring Beam Welding

Ring Beam Welding | 링 빔 용접

Ring Beam Welding

시뮬레이션 설명

이 시뮬레이션은 FLOW-3D 및 FLOW-3D WELD를 사용하여 만들 수 있는 수많은 다양한 레이저 모양 중 하나인 일반 링, 레이저 빔을 보여줍니다. 이 시뮬레이션을 실행하려면 FLOW-3D WELD가 필요합니다.

시뮬레이션 세부 정보

버전#: FLOW-3D v11.2와 FLOW-3D WELD가 결합됨

본 사례에 대해 궁금하신 사항이 있으시면 언제든지 기술지원팀에 연락주세요.

Laser Oscillation Welding

Laser Oscillation Welding | 레이저 진동 용접

Laser Oscillation Welding

시뮬레이션 설명

이 시뮬레이션은 8Hz 주파수에서 2개의 AISI 1026 강철 조각 사이의 진동 용접을 시연합니다. FLOW-3D AM을 사용하여 브리지 간격 거리에 사용되는 다양한 진동 용접 기법을 조사할 수 있습니다. 이 시뮬레이션을 실행하려면 FLOW-3D WELD가 필요합니다.

시뮬레이션 세부 정보

버전#: FLOW-3D v11.2와 FLOW-3D WELD가 결합됨
만든 날짜: 2020년 12월

본 사례에 대해 궁금하신 사항이 있으시면 언제든지 기술지원팀에 연락주세요.

레이저 용접 수치해석 (FLOW-3D WELD)

FLOW-3D WELD Products

레이저 용접 수치해석 (FLOW-3D WELD)

FLOW-3D@ WELD는 레이저 용접 공정에 대한 정확한 시뮬레이션 기능을 제공하여 최적화된 공정을 개발하게 합니다. 더 나은 공정 제어를 통해 기공, 열 영향 영역을 최소화하고 미세 구조 변화를 제어할 수 있습니다.

레이저 용접 프로세스를 정확하게 시뮬레이션하기 위해 FLOW-3D@ WELD는 레이저 열원, 레이저-재료 상호 작용, 유체 흐름, 열 전달, 표면 장력, 응고, 다중 레이저 반사 및 위상 변화와 같은 모든 관련 물리 모델을 제공합니다.

Laser Welding

최근에는 뛰어난 생산성과 속도, 낮은 열 입력이 결합되어 기존의 용접 프로세스를 대체하는 레이저 용접 프로세스가 주목 받고 있습니다. 레이저 용접이 제공하는 장점은 용접강도가 좋고, 열 영향 부위가 작으며, 정밀도가 낮고 변형이 적으며, 강철, 알루미늄, 티타늄 및 이종 금속을 포함한 광범위한 금속 및 합금을 용접 할 수 있는 기능이 있습니다.

FLOW-3D@는 레이저 용접 공정에 대한 강력한 통찰력을 제공하고 궁극적으로 프로세스 최적화를 달성하는 데 도움이 됩니다.

보다 나은 프로세스 제어를 통해 기공을 최소화할 수 있습니다. 열 영향부위 및 미세조직을 제어가 가능합니다. FLOW-3D는 자유표면 추적 알고리즘을 통해 매우 복잡한 용접 POOL 시뮬레이션을 해석하는데 매우 적합합니다.

용접 모듈은 레이저 소스에 의해 생성된 Heat flux, 용융 금속에 대한 증발압력, shield gas 효과, 용융 풀의 반동압력 및 다중 레이저 반사와 같은 물리적 모델을 FLOW-3D에 적용하기 위해 개발되었습니다. 키홀 용접과 같은 현실적인 프로세스 시뮬레이션을 위해서는 모든 관련 물리적 현상을 적용하는 것이 중요합니다.

FLOW-3D는 레이저 용접의 conduction and keyhole 방식을 시뮬레이션 할 수 있습니다. 전 세계의 연구원들은 FLOW-3D를 사용하여 용접역학을 분석하고, 공정 매개 변수를 최적화하여 기공을 최소화하며, 레이저 용접공정에서의 dendrite 결정 성장 양상을 예측합니다.

Shallow penetration weld (top left); deep penetration weld with shield gas effects (top right); deep penetration weld with shield gas and evaporation pressure (bottom left); and deep penetration weld with shield gas, evaporation pressure and multiple laser reflections effects (bottom right).

Full Penetration Laser Welding Experiments

한국 카이스트와 독일 BAM은 16K kW레이저를 사용하여 10mm강판에 완전 침투 레이저 용접 실험을 수행하였습니다. CCD카메라의 도움을 받아 완전 용입 레이저 용접으로 형성된 상단 및 하단 용융풀 거동을 확인할 수 있었습니다. 그들은 또한 FLOW-3D 로 용접 공정 해석으로 해석과 실험결과의 경향이 일치하는 것을 알 수 있었습니다.

Experimental setup with CCD cameras observing the top and bottom molten pools
Schematic of computation domain in FLOW-3D

 

Simulation results at the top show melt pool lengths of 8mm and 15mm, whereas experiments indicated melt pool lengths of 7mm and 13mm

Laser Welding Porosity Case Study

General Motors, Michigan, 중국의 상하이 대학교는 용접 공정 변수, 즉 keyhole 용접에서 기공의 발생에 대해 용접 속도 및 용접 각도와 같은 공정 매개 변수가 미치는 영향을 알아보기 위해 협력하여 연구를 진행하였습니다.

레이저 용접된 Al 접합부 단면의 기공을 분석합니다. Keyhole이 유도 된 기공들은 유동 역학으로 인해 발생되고 균열을 일으킬 수 있습니다. 최적화 공정의 매개변수는 이러한 종류의 기공을 완화할 수 있습니다. FLOW-3D를 사용하여 연구원들은 증발 및 반동 압력, 용융풀, 온도에 따른 표면장력 및 Keyhole내의 다중 레이저 반사, 프레넬 흡수를 포함한 모든 중요한 물리적 현상을 설명했습니다.

연구진은 시뮬레이션 모델을 기반으로 Keyhole 용접에서 생성된 기공들의 주요 원인으로 불안정한 Keyhole을 규정하였습니다. 아래 이미지에서 볼 수 있듯이 뒤쪽 용융 풀의 과도한 재순환은 뒤쪽 용융 풀이 앞쪽 용융 풀 경계를 무너뜨리며 기공들을 생성시킵니다. 갇힌 공간이 증가하는 응고 전면에 의해 갇혔을때 기공들이 발생되었습니다.

Distribution of porosity in longitudinal welding sections as seen in simulations (top) and experiments (bottom)

용접 속도가 빠를수록 더 큰 keyhole이 생성되며 이로 인해, 보다 안정적인 keyhole이 생성됩니다. 연구진은 FLOW-3D를 사용하여 용접 속도와 용접 경사각으로 기공들의 생성을 완화시킬 수 있었습니다.


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Fig 3. Front view of the ejected powder particles due to the plume movement. Powder particles are colored by their respective temperature while trajectory colors show their magnitude at 0.007 seconds.

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Figure 3: 3D temperature contours and 2D melt pool cross-sections where the melt pool is stabilized at x=500 µm from the start of the laser initial location for cases where (a) absorptivity = 0.1, Recoil pressure coefficient B = 1 and laser beam radius = 12 µm, (b) absorptivity = 0.1, Recoil pressure coefficient B = 20 and laser beam radius = 12 µm, (c) absorptivity = 0.1, Recoil pressure coefficient B = 1 and laser beam radius = 18 µm, (d) absorptivity = 0.45, Recoil pressure coefficient B = 1 and laser beam radius = 18 µm, (e) absorptivity = 0.45, Recoil pressure coefficient B = 20 and laser beam radius = 12 µm, (f) absorptivity = 0.45, Recoil pressure coefficient B = 20 and laser beam radius = 18 µm.

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CFD가 레이저 용접을 만나면 : 불꽃이 어떻게 날아갑니까?

Pareekshith Allu Senior CFD Engineer | Additive Manufacturing | Laser Welding | Business Development

When CFD meets laser welding: How sparks fly!

CFD 또는 전산 유체 역학은 수치적 방법을 사용하여 유체 흐름을 연구하는 것입니다. 유체 흐름의 기본 방정식에는 솔루션 해가 없으므로 컴퓨터를 사용하여 방정식을 반복적으로 계산하는 수치해석 방법으로 해결합니다. 일반적으로 CFD 도구는 공기 역학, 엔진 연소, 물 및 환경 흐름, 미세 유체 및 제조 공정에서 광범위한 연구 및 엔지니어링 문제에 적용될 수 있습니다. CFD가 개발에 중요한 역할을 한 기술을 매일 접할 가능성이 있습니다. FLOW-3D 소프트웨어 제품 제조업체인 Flow Science Inc.에서는 자유 표면 흐름 문제 라고하는 특수한 문제 해결에 중점을 둡니다 . 

자유 표면 흐름이란 무엇입니까? 밀도 차이가 큰 두 유체간에 인터페이스가 공유되는 분야는 자유 표면 흐름입니다. 예를 들어, 기체-액체 경계면이 제한되지 않고 시간에 따라 자유롭게 움직이고 변경할 수 있다는 점에서 강의 물과 주변 공기 사이에 자유 표면이 존재합니다. FLOW-3D 솔버의 기본 DNA 인 Volume of Fluid 또는 VoF 방법 은 자유 표면의 진화를 추적하는 강력한 계산 기술입니다. 우리는 지난 40 년 동안 이 문제에 거의 전적으로 집중했습니다.

자유 표면 흐름은 제조산업 분야에서도 널리 사용됩니다. 금속 주조에서는 용융 금속과 용융 금속이 채우는 금형 또는 다이의 공기 사이에 자유 표면이 존재합니다. L-PBF ( Laser Powder Bed fusion) 라고하는 적층 제조 공정에서 레이저를 사용하여 분말 입자를 녹이고 융합하여 공정에서 자유 표면 용융 풀을 만듭니다. 그리고 레이저 용접에서는 레이저 빔에 의해 녹아서 두 개의 금속 부품 / 부품을 함께 융합 할 때 형성되는 자유 표면 용융 풀이 있습니다. 

이 게시물에서는 레이저 용접 공정에 대한 CFD 시뮬레이션이 유용한 이유를 설명합니다.

레이저 기술은 지난 몇 년 동안 상당히 발전했으며 이제 다른 레이저 제조업체는 다양한 파장에서 펄싱 기능이 있는 고출력 레이저를 제공 할 수 있습니다. 레이저와 로봇 자동화 시스템, 컨트롤러 및 프로세스 센서의 통합은 다양한 제조 산업에서 사용을 확대하여 열 입력이 적고 열 영향 영역이 더 작은 레이저 용접 조인트를 가능하게합니다. 

레이저-재료 상호 작용은 복잡하며이를 정확하게 모델링하려면 이러한 시간적 및 공간적 규모와 관련된 물리학을 구현해야합니다. 레이저 열원은 표면에 에너지를 축적하여 기판을 녹이고 용융 금속 풀을 만듭니다. 용융 풀은 전력, 속도 및 스캔 경로와 같은 레이저 가공 매개 변수와 용융 풀의 자유 표면에 동적 증기압을 적용하는 차폐 가스의 영향을 더 많이받습니다. 또한 용접되는 기판의 재료 특성이 중요한 역할을합니다. 용융된 풀의 상 변화와 증발은 용융 풀을 더욱 압박하는 반동 압력을 유발할 수있는 반면 표면 장력은 풀 내의 유체 대류에 영향을줍니다. 키홀 링이있는 경우 레이저 광선이 키홀 내에 갇혀 추가 반사 영향을 받을 수 있습니다. 기판에 더 많은 에너지를 전달합니다. 불안정한 키홀이 붕괴되면 갇힌 공극이 진행되는 응고 경계에 의해 포착되는 다공성 형성으로 이어질 수 있습니다. 

분명히 많은 일이 진행되고 있습니다. 이것이 CFD 시뮬레이션이 강력 할 수있는 곳이며 FLOW-3D WELD를 개발할 때 레이저-재료 상호 작용을 이해하는 데 많은 노력을 기울이는 이유입니다. 자유 표면 추적 및 레이저 에너지 증착, 차폐 가스 역학, 상 변화, 반동 압력, 표면 장력, 레이저 광선 추적 및 응고와 함께 유체 및 열 흐름 방정식을 통합하는 물리 기반 모델은 레이저의 복잡한 상호 작용을 캡처하는 데 매우 정확합니다. 용접과정을 해석하는 기능은 용융 풀의 안정성에 대한 다양한 공정 매개 변수의 영향을 분리하고 엔지니어와 연구원이 용접 일정을 최적화하는 데 도움이 될 수 있습니다.

CFD 시뮬레이션은 레이저 용접 프로세스를 분석하고 개선하는데 도움이되는 프레임 워크를 제공 할 수 있습니다. 불안정한 용융 풀은 키홀 유발 다공성, 파열 및 스패 터와 같은 결함을 초래할 수 있기 때문에 용융 풀의 작동 방식을 이해하는 것은 조인트의 품질에 매우 중요합니다. 그 후, FLOW-3D WELD 모델의 출력인 응고된 용융 풀 데이터 및 열 구배와 같은 결과를 미세 구조 또는 유한 요소 분석 모델에 입력하여 각각 결정 성장 및 열 응력 진화를위한 길을 닦을 수 있습니다.

이 게시물이 CFD를 사용하여 레이저 용접 프로세스를 시뮬레이션하는 이점을 이해하는데 도움이 되기를 바랍니다.

레이저 용접 공정을 더 잘 이해하기 위해 CFD 시뮬레이션 적용을 고려해 보셨습니까? 어떤 특징 / 물리 현상이 모델링되기를 원하십니까? 질문과 의견이 있으면 언제든지 flow3d@stikorea.co.kr 또는 미국 본사의 paree.allu@flow3d.com에게 연락하십시오.

2 Fluid, 1 Temperature

2 Fluid, 2 Temperature 모델

2 Fluid, 2 Temperature 모델

우주선 및 자동차 연료 탱크 및 특정 미세 유체 장치는 안전하고 효율적인 작동을 위해 정확한 액체 및 기체 상태 모델링이 필요합니다. 이러한 시스템에 유체 계면이 존재하는 것 외에도, 열 전달 및 상 변화의 물리학도 정확하게 포착해야합니다. 얼마나 복잡합니까!

이러한 복잡한 시나리오를 시뮬레이션하기 위해 FLOW-3D v12.0에는 2 Fluid, 2 Temperature 모델이 도입되었습니다.

 

단순화 된 모델 : 2 Fluid, 1 Temperature

FLOW-3D 의 인터페이스 추적 방법인 TruVOF는 열 전달 및 위상 변화를 포함하여 2 Fluid 모델과 함께 작동합니다. 그러나,이 모델의 단순화 중 하나는, 인터페이스를 갖는 메쉬 셀의 온도가 다음의 개략도에 도시 된 바와 같이 혼합물 온도 (따라서 단순화 된 모델) Tmix로 표현된다는 것입니다.

온도가 경계면을 가로 질러 연속적이고 매끄러 울 때 혼합물 근사치가 적절하지만, 열-물리적 특성의 큰 차이로 인해 액체 및 가스가 있는 경우에는 이를 추정 할 수 없습니다. 이러한 시스템에서 용액의 정확도는 액체-기체 혼합물을 함유하는 셀에서 유체 에너지 및 온도의 평균으로부터 발생하는 과도한 수치 확산에 의해 압도 될 수 있습니다. 단순화 된 온도 슬립 모델은 이러한 경우 부분적인 솔루션만 제공합니다.

단순화 된 모델-2 Fluid, 1 Temperature

종합 모델 : 2 Fluid, 2 Temperature

1 Temperature 접근 방식의 결함을 극복하기 위해 2 Fluid 솔루션에 대한 2 Temperature 모델이 버전 11.3에 도입되었습니다. 여기에는 아래 회로도에 표시된 것처럼 각 유체에 대한 에너지 전달 방정식을 해결하고 각 상의 온도를 저장하는 작업이 포함됩니다. 자유 표면이 있는 메쉬 셀은 이제 액체 (T1)와 가스 (T2) 온도를 모두 나타냅니다.

종합 모델 : 2 유체, 2 온도

탱크 슬로싱(Tank sloshing)

탱크 슬로싱에 대한 이 사례 연구에서, 액체는 초기 온도 300K이고 가스는 400K입니다. 단순화 된 모델과 포괄적인 모델 사이의 수치 확산 정도의 차이는 아래 애니메이션에 나와 있습니다. 온도 윤곽에서 시간이 지남에 따라 용액의 수치 확산은 1 Temperature 접근 방식으로 보여지고 계면 물리를 완전히 가리게 됩니다.

단순화 된 모델 : 2 Fluid, 1 Temperature

종합 모델 : 2 Fluid, 2 Temperature

공기중 드롭 용접(Drop welding in air)

이 낙하 용접 사례 연구에서 액체 금속은 중력 하에서 2300K에서 공기를 통해 고체화 된 금속 베드로 떨어집니다. 공기 및 베드 초기 온도는 293K입니다. simplified model에서는 수치 확산으로 인해 액체 금속 낙하 온도가 베드에 도달하기 전에도 급격히 감소하기 시작합니다. 반면에 comprehensive model에서는 방울이 초기 온도를 유지하여 훨씬 더 나은 솔루션을 제공합니다.

단순화 된 모델을 사용한 온도 필드 진화

종합 모델의 온도 필드

FLOW-3D의 2 Fluid, 2 Temperature 모델과 유체 인터페이스 추적을 결합하면 사용자는 특히 연료 슬로싱 시스템과 같이 복잡한 열전달 및 위상 변화 문제를 정확하게 모델링 할 수 있습니다.

이 새로운 모델에 대한 제안이나 의견은 adwaith@flow3d.com에 문의하십시오.

The realm of operations of FLOW-3D

ADDITIVE MANUFACTURING SIMULATIONS

Capabilities of FLOW-3D

FLOW-3D는 자유 표면 유체 흐름 시뮬레이션을 전문으로하는 다중 물리 CFD 소프트웨어입니다. 자유 표면의 동적 진화를 추적하는 소프트웨어의 알고리즘인 VOF (Volume of Fluid) 방법은 Flow Science의 설립자인 Tony Hirt 박사가 개척했습니다.

또한 FLOW-3D에는 금속 주조, 잉크젯 인쇄, 레이저 용접 및 적층 제조 (AM)와 같은 광범위한 응용 분야를 시뮬레이션하기위한 물리 모델이 내장되어 있습니다.
적층 제조 시뮬레이션 소프트웨어, 특히 L-PBF (레이저 파우더 베드 융합 공정)의 현상 유지는 열 왜곡, 잔류 응력 및지지 구조 생성과 같은 부분 규모 모델링에 도움이되는 열 기계 시뮬레이션에 초점을 맞추고 있습니다.

유용하지만 용융 풀 역학 및 볼링 및 다공성과 같은 관련 결함에 대한 정보는 일반적으로 이러한 접근 방식의 영역 밖에 있습니다. 용융 풀 내의 유체 흐름, 열 전달 및 표면 장력이 열 구배 및 냉각 속도에 영향을 미치며 이는 다시 미세 구조 진화에 영향을 미친다는 점을 명심하는 것도 중요합니다.

FLOW-3D와 이산 요소법 (DEM) 및 WELD 모듈을 사용하여 분말 및 용융 풀 규모에서 시뮬레이션 할 수 있습니다.
구현되는 관련 물리학에는 점성 흐름, 열 전달, 응고, 상 변화, 반동 압력, 차폐 가스 압력, 표면 장력, 움직이는 물체 및 분말 / 입자 역학이 포함됩니다. 이러한 접근 방식은 합금에 대한 공정을 성공적으로 개발할 수 있게 하고, AM 기계 제조업체와 AM 기술의 최종 사용자 모두에게 관심있는 미세 구조 진화에 대한 통찰력을 제공하는데 도움이 됩니다.

The realm of operations of FLOW-3D
The realm of operations of FLOW-3D

FLOW-3D는 레이저 분말 베드 융합 (L-PBF), 직접 에너지 증착 (DED) 및 바인더 제트 공정으로 확장되는 기능을 가지고 있습니다.
FLOW-3D를 사용하면 분말 확산 및 패킹, 레이저 / 입자 상호 작용, 용융 풀 역학, 표면 형태 및 후속 미세 구조 진화를 정확하게 시뮬레이션 할 수 있습니다. 이러한 기능은 FLOW-3D에 고유하며 계산 효율성이 높은 방식으로 달성됩니다.

예를 들어 1.0mm x 0.4mm x 0.3mm 크기의 계산 영역에서 레이저 빔의 단일 트랙을 시뮬레이션하기 위해 레이저 용융 모델은 단 8 개의 물리적 코어에서 약 2 시간이 걸립니다.
FLOW-3D는 모든 관련 물리 구현 간의 격차를 해소하는 동시에 업계 및 연구 표준에서 허용하는 시간 프레임으로 결과를 생성합니다. 분말 패킹, 롤러를 통한 파워 확산, 분말의 레이저 용융, 용융 풀 형성 및 응고를 고려하고 다층 분말 베드 융합 공정을 위해 이러한 단계를 순차적으로 반복하여 FLOW-3D에서 전체 AM 공정을 시뮬레이션 할 수 있습니다.

FLOW-3D의 다층 시뮬레이션은 이전에 응고된 층의 열 이력을 저장한다는 점에서 독특하며, 열 전달을 고려하여 이전에 응고된 층에 확산된 새로운 분말 입자 세트에 대해 시뮬레이션이 수행됩니다.
또한, 응고 된 베드의 열 왜곡 및 잔류 응력은 FLOW-3D를 사용하여 평가할 수 있으며, 보다 복잡한 분석을 수행하기 위해 FLOW-3D의 압력 및 온도 데이터를 Abaqus 및 MSC Nastran과 같은 FEA 소프트웨어로 내보낼 수 있습니다.

Sequence of a multi-layer L-PBF simulation setup in FLOW-3D

Ease of Use

FLOW-3D는 다양한 응용 분야에서 거의 40 년 동안 사용되어 왔습니다. 사용자 피드백을 기반으로 UI 개발자는 소프트웨어를 사용하기 매우 직관적으로 만들었으며 새로운 사용자는 시뮬레이션 설정의 순서를 거의 또는 전혀 어려움없이 이해합니다.
사용자는 FLOW3D에서 구현 된 다양한 모델의 이론에 정통하며 새로운 실험을 설계 할 수 있습니다. 실습 튜토리얼, 비디오 강의, 예제 시뮬레이션 및 기술 노트의 저장소도 사용할 수 있습니다.
사용자가 특정 수준의 경험에 도달하면 고급 수치 교육 및 소프트웨어 사용자 지정 교육을 사용할 수 있습니다.

Available Literature

실험 데이터에 대해 FLOW-3D 모델을 검증하는 몇 가지 독립적으로 발표된 연구가 있습니다. 여기에서 수록된 저널 논문은 레이저 용접 및 적층 제조 공정으로 제한됩니다. 더 많은 참조는 당사 웹 사이트에서 확인할 수 있습니다.

Laser Welding

  1. L.J.Zhang, J.X.Zhang, A.Gumenyuk, M.Rethmeier, S.J.Na, Numerical simulation of full penetration laser welding of thick steel plate with high power high brightness laser, Journal of Materials Processing Technology, Volume 214, Issue 8, 2014.
    A study by researchers from BAM in Germany, KAIST in Korea, and State Key Laboratory of Mechanical Behavior of Materials in China that focuses on keyhole dynamics and full penetration laser welding of steel plates.
  2. Runqi Lin, Hui-ping Wang, Fenggui Lu, Joshua Solomon, Blair E.
    Carlson, Numerical study of keyhole dynamics and keyhole-induced porosity formation in remote laser welding of Al alloys, International Journal of Heat and Mass Transfer, Volume 108, Part A, 2017.
    General Motors (GM) and Shangai University collaborated on a study on the influence of welding speed and weld angle of inclination on porosity occurrence in laser keyhole welding.
  3. Koji Tsukimoto, Masashi Kitamura, Shuji Tanigawa, Sachio Shimohata, and Masahiko Mega, Laser Welding Repair for Single Crystal Blades, International Gas Turbine Congress, Tokyo, 2015.
    Mitsubishi Heavy Industry’s study on laser welding repair using laser cladding for single Ni crystal alloys used in gas turbine blades.

Additive Manufacturing

  1. Yu-Che Wu, Cheng-Hung San, Chih-Hsiang Chang, Huey-Jiuan Lin, Raed Marwan, Shuhei Baba, Weng-Sing Hwang, Numerical modeling of melt-pool behavior in selective laser melting with random powder distribution and experimental validation, Journal of Materials Processing Technology, Volume 254, 2018
    This paper discusses powder bed compaction with random packing for different powder-size distributions, and the importance of considering evaporation effects in the melting process to validate the melt pool dimensions.
  2. Lee, Y.S., and W.Zhang, Mesoscopic simulation of heat transfer and fluid flow in laser powder bed additive manufacturing, Proceedings of the Annual International Solid Freeform Fabrication Symposium, Austin, TX, USA. 2015
    A study conducted by Ohio State University researchers to understand the influence of process parameters in formation of balling defects.
  3. Y.S. Lee, W.Zhang, Modeling of heat transfer, fluid flow and solidification microstructure of nickel-base superalloy fabricated by laser powder bed fusion, Additive Manufacturing, Volume 12, Part B, 2016
    A study conducted by Ohio State University researchers to understand the influence of solidification parameters, calculated from the temperature fields, on solidification morphology and grain size using existing theoretical models in laser powder bed fusion processes.

 

 

FLOW-3D CAST Bibliography

FLOW-3D CAST bibliography

아래는 FSI의 금속 주조 참고 문헌에 수록된 기술 논문 모음입니다. 이 모든 논문에는 FLOW-3D CAST 해석 결과가 수록되어 있습니다. FLOW-3D CAST를 사용하여 금속 주조 산업의 응용 프로그램을 성공적으로 시뮬레이션하는 방법에 대해 자세히 알아보십시오.

Below is a collection of technical papers in our Metal Casting Bibliography. All of these papers feature FLOW-3D CAST results. Learn more about how FLOW-3D CAST can be used to successfully simulate applications for the Metal Casting Industry.

33-20     Eric Riedel, Martin Liepe Stefan Scharf, Simulation of ultrasonic induced cavitation and acoustic streaming in liquid and solidifying aluminum, Metals, 10.4; 476, 2020. doi.org/10.3390/met10040476

20-20   Wu Yue, Li Zhuo and Lu Rong, Simulation and visual tester verification of solid propellant slurry vacuum plate casting, Propellants, Explosives, Pyrotechnics, 2020. doi.org/10.1002/prep.201900411

17-20   C.A. Jones, M.R. Jolly, A.E.W. Jarfors and M. Irwin, An experimental characterization of thermophysical properties of a porous ceramic shell used in the investment casting process, Supplimental Proceedings, pp. 1095-1105, TMS 2020 149th Annual Meeting and Exhibition, San Diego, CA, February 23-27, 2020. doi.org/10.1007/978-3-030-36296-6_102

12-20   Franz Josef Feikus, Paul Bernsteiner, Ricardo Fernández Gutiérrez and Michal Luszczak , Further development of electric motor housings, MTZ Worldwide, 81, pp. 38-43, 2020. doi.org/10.1007/s38313-019-0176-z

09-20   Mingfan Qi, Yonglin Kang, Yuzhao Xu, Zhumabieke Wulabieke and Jingyuan Li, A novel rheological high pressure die-casting process for preparing large thin-walled Al–Si–Fe–Mg–Sr alloy with high heat conductivity, high plasticity and medium strength, Materials Science and Engineering: A, 776, art. no. 139040, 2020. doi.org/10.1016/j.msea.2020.139040

07-20   Stefan Heugenhauser, Erhard Kaschnitz and Peter Schumacher, Development of an aluminum compound casting process – Experiments and numerical simulations, Journal of Materials Processing Technology, 279, art. no. 116578, 2020. doi.org/10.1016/j.jmatprotec.2019.116578

05-20   Michail Papanikolaou, Emanuele Pagone, Mark Jolly and Konstantinos Salonitis, Numerical simulation and evaluation of Campbell running and gating systems, Metals, 10.1, art. no. 68, 2020. doi.org/10.3390/met10010068

102-19   Ferencz Peti and Gabriela Strnad, The effect of squeeze pin dimension and operational parameters on material homogeneity of aluminium high pressure die cast parts, Acta Marisiensis. Seria Technologica, 16.2, 2019. doi.org/0.2478/amset-2019-0010

94-19   E. Riedel, I. Horn, N. Stein, H. Stein, R. Bahr, and S. Scharf, Ultrasonic treatment: a clean technology that supports sustainability incasting processes, Procedia, 26th CIRP Life Cycle Engineering (LCE) Conference, Indianapolis, Indiana, USA, May 7-9, 2019. 

93-19   Adrian V. Catalina, Liping Xue, Charles A. Monroe, Robin D. Foley, and John A. Griffin, Modeling and Simulation of Microstructure and Mechanical Properties of AlSi- and AlCu-based Alloys, Transactions, 123rd Metalcasting Congress, Atlanta, GA, USA, April 27-30, 2019. 

84-19   Arun Prabhakar, Michail Papanikolaou, Konstantinos Salonitis, and Mark Jolly, Sand casting of sheet lead: numerical simulation of metal flow and solidification, The International Journal of Advanced Manufacturing Technology, pp. 1-13, 2019. doi.org/10.1007/s00170-019-04522-3

72-19   Santosh Reddy Sama, Eric Macdonald, Robert Voigt, and Guha Manogharan, Measurement of metal velocity in sand casting during mold filling, Metals, 9:1079, 2019. doi.org/10.3390/met9101079

71-19   Sebastian Findeisen, Robin Van Der Auwera, Michael Heuser, and Franz-Josef Wöstmann, Gießtechnische Fertigung von E-Motorengehäusen mit interner Kühling (Casting production of electric motor housings with internal cooling), Geisserei, 106, pp. 72-78, 2019 (in German).

58-19     Von Malte Leonhard, Matthias Todte, and Jörg Schäffer, Realistic simulation of the combustion of exothermic feeders, Casting, No. 2, pp. 28-32, 2019. In English and German.

52-19     S. Lakkum and P. Kowitwarangkul, Numerical investigations on the effect of gas flow rate in the gas stirred ladle with dual plugs, International Conference on Materials Research and Innovation (ICMARI), Bangkok, Thailand, December 17-21, 2018. IOP Conference Series: Materials Science and Engineering, Vol. 526, 2019. doi.org/10.1088/1757-899X/526/1/012028

47-19     Bing Zhou, Shuai Lu, Kaile Xu, Chun Xu, and Zhanyong Wang, Microstructure and simulation of semisolid aluminum alloy castings in the process of stirring integrated transfer-heat (SIT) with water cooling, International Journal of Metalcasting, Online edition, pp. 1-13, 2019. doi.org/10.1007/s40962-019-00357-6

31-19     Zihao Yuan, Zhipeng Guo, and S.M. Xiong, Skin layer of A380 aluminium alloy die castings and its blistering during solution treatment, Journal of Materials Science & Technology, Vol. 35, No. 9, pp. 1906-1916, 2019. doi.org/10.1016/j.jmst.2019.05.011

25-19     Stefano Mascetti, Raul Pirovano, and Giulio Timelli, Interazione metallo liquido/stampo: Il fenomeno della metallizzazione, La Metallurgia Italiana, No. 4, pp. 44-50, 2019. In Italian.

20-19     Fu-Yuan Hsu, Campbellology for runner system design, Shape Casting: The Minerals, Metals & Materials Series, pp. 187-199, 2019. doi.org/10.1007/978-3-030-06034-3_19

19-19     Chengcheng Lyu, Michail Papanikolaou, and Mark Jolly, Numerical process modelling and simulation of Campbell running systems designs, Shape Casting: The Minerals, Metals & Materials Series, pp. 53-64, 2019. doi.org/10.1007/978-3-030-06034-3_5

18-19     Adrian V. Catalina, Liping Xue, and Charles Monroe, A solidification model with application to AlSi-based alloys, Shape Casting: The Minerals, Metals & Materials Series, pp. 201-213, 2019. doi.org/10.1007/978-3-030-06034-3_20

17-19     Fu-Yuan Hsu and Yu-Hung Chen, The validation of feeder modeling for ductile iron castings, Shape Casting: The Minerals, Metals & Materials Series, pp. 227-238, 2019. doi.org/10.1007/978-3-030-06034-3_22

04-19   Santosh Reddy Sama, Tony Badamo, Paul Lynch and Guha Manogharan, Novel sprue designs in metal casting via 3D sand-printing, Additive Manufacturing, Vol. 25, pp. 563-578, 2019. doi.org/10.1016/j.addma.2018.12.009

02-19   Jingying Sun, Qichi Le, Li Fu, Jing Bai, Johannes Tretter, Klaus Herbold and Hongwei Huo, Gas entrainment behavior of aluminum alloy engine crankcases during the low-pressure-die-casting-process, Journal of Materials Processing Technology, Vol. 266, pp. 274-282, 2019. doi.org/10.1016/j.jmatprotec.2018.11.016

92-18   Fast, Flexible… More Versatile, Foundry Management Technology, March, 2018. 

82-18   Xu Zhao, Ping Wang, Tao Li, Bo-yu Zhang, Peng Wang, Guan-zhou Wang and Shi-qi Lu, Gating system optimization of high pressure die casting thin-wall AlSi10MnMg longitudinal loadbearing beam based on numerical simulation, China Foundry, Vol. 15, no. 6, pp. 436-442, 2018. doi: 10.1007/s41230-018-8052-z

80-18   Michail Papanikolaou, Emanuele Pagone, Konstantinos Salonitis, Mark Jolly and Charalampos Makatsoris, A computational framework towards energy efficient casting processes, Sustainable Design and Manufacturing 2018: Proceedings of the 5th International Conference on Sustainable Design and Manufacturing (KES-SDM-18), Gold Coast, Australia, June 24-26 2018, SIST 130, pp. 263-276, 2019. doi.org/10.1007/978-3-030-04290-5_27

64-18   Vasilios Fourlakidis, Ilia Belov and Attila Diószegi, Strength prediction for pearlitic lamellar graphite iron: Model validation, Metals, Vol. 8, No. 9, 2018. doi.org/10.3390/met8090684

51-18   Xue-feng Zhu, Bao-yi Yu, Li Zheng, Bo-ning Yu, Qiang Li, Shu-ning Lü and Hao Zhang, Influence of pouring methods on filling process, microstructure and mechanical properties of AZ91 Mg alloy pipe by horizontal centrifugal casting, China Foundry, vol. 15, no. 3, pp.196-202, 2018. doi.org/10.1007/s41230-018-7256-6

47-18   Santosh Reddy Sama, Jiayi Wang and Guha Manogharan, Non-conventional mold design for metal casting using 3D sand-printing, Journal of Manufacturing Processes, vol. 34-B, pp. 765-775, 2018. doi.org/10.1016/j.jmapro.2018.03.049

42-18   M. Koru and O. Serçe, The Effects of Thermal and Dynamical Parameters and Vacuum Application on Porosity in High-Pressure Die Casting of A383 Al-Alloy, International Journal of Metalcasting, pp. 1-17, 2018. doi.org/10.1007/s40962-018-0214-7

41-18   Abhilash Viswanath, S. Savithri, U.T.S. Pillai, Similitude analysis on flow characteristics of water, A356 and AM50 alloys during LPC process, Journal of Materials Processing Technology, vol. 257, pp. 270-277, 2018. doi.org/10.1016/j.jmatprotec.2018.02.031

29-18   Seyboldt, Christoph and Liewald, Mathias, Investigation on thixojoining to produce hybrid components with intermetallic phase, AIP Conference Proceedings, vol. 1960, no. 1, 2018. doi.org/10.1063/1.5034992

28-18   Laura Schomer, Mathias Liewald and Kim Rouven Riedmüller, Simulation of the infiltration process of a ceramic open-pore body with a metal alloy in semi-solid state to design the manufacturing of interpenetrating phase composites, AIP Conference Proceedings, vol. 1960, no. 1, 2018. doi.org/10.1063/1.5034991

41-17   Y. N. Wu et al., Numerical Simulation on Filling Optimization of Copper Rotor for High Efficient Electric Motors in Die Casting Process, Materials Science Forum, Vol. 898, pp. 1163-1170, 2017.

12-17   A.M.  Zarubin and O.A. Zarubina, Controlling the flow rate of melt in gravity die casting of aluminum alloys, Liteynoe Proizvodstvo (Casting Manufacturing), pp 16-20, 6, 2017. In Russian.

10-17   A.Y. Korotchenko, Y.V. Golenkov, M.V. Tverskoy and D.E. Khilkov, Simulation of the Flow of Metal Mixtures in the Mold, Liteynoe Proizvodstvo (Casting Manufacturing), pp 18-22, 5, 2017. In Russian.

08-17   Morteza Morakabian Esfahani, Esmaeil Hajjari, Ali Farzadi and Seyed Reza Alavi Zaree, Prediction of the contact time through modeling of heat transfer and fluid flow in compound casting process of Al/Mg light metals, Journal of Materials Research, © Materials Research Society 2017

04-17   Huihui Liu, Xiongwei He and Peng Guo, Numerical simulation on semi-solid die-casting of magnesium matrix composite based on orthogonal experiment, AIP Conference Proceedings 1829, 020037 (2017); doi.org/10.1063/1.4979769.

100-16  Robert Watson, New numerical techniques to quantify and predict the effect of entrainment defects, applied to high pressure die casting, PhD Thesis: University of Birmingham, 2016.

88-16   M.C. Carter, T. Kauffung, L. Weyenberg and C. Peters, Low Pressure Die Casting Simulation Discovery through Short Shot, Cast Expo & Metal Casting Congress, April 16-19, 2016, Minneapolis, MN, Copyright 2016 American Foundry Society.

61-16   M. Koru and O. Serçe, Experimental and numerical determination of casting mold interfacial heat transfer coefficient in the high pressure die casting of a 360 aluminum alloy, ACTA PHYSICA POLONICA A, Vol. 129 (2016)

59-16   R. Pirovano and S. Mascetti, Tracking of collapsed bubbles during a filling simulation, La Metallurgia Italiana – n. 6 2016

43-16   Kevin Lee, Understanding shell cracking during de-wax process in investment casting, Ph.D Thesis: University of Birmingham, School of Engineering, Department of Chemical Engineering, 2016.

35-16   Konstantinos Salonitis, Mark Jolly, Binxu Zeng, and Hamid Mehrabi, Improvements in energy consumption and environmental impact by novel single shot melting process for casting, Journal of Cleaner Production, doi.org/10.1016/j.jclepro.2016.06.165, Open Access funded by Engineering and Physical Sciences Research Council, June 29, 2016

20-16   Fu-Yuan Hsu, Bifilm Defect Formation in Hydraulic Jump of Liquid Aluminum, Metallurgical and Materials Transactions B, 2016, Band: 47, Heft 3, 1634-1648.

15-16   Mingfan Qia, Yonglin Kanga, Bing Zhoua, Wanneng Liaoa, Guoming Zhua, Yangde Lib,and Weirong Li, A forced convection stirring process for Rheo-HPDC aluminum and magnesium alloys, Journal of Materials Processing Technology 234 (2016) 353–367

112-15   José Miguel Gonçalves Ledo Belo da Costa, Optimization of filling systems for low pressure by FLOW-3D, Dissertação de mestrado integrado em Engenharia Mecânica, 2015.

89-15   B.W. Zhu, L.X. Li, X. Liu, L.Q. Zhang and R. Xu, Effect of Viscosity Measurement Method to Simulate High Pressure Die Casting of Thin-Wall AlSi10MnMg Alloy Castings, Journal of Materials Engineering and Performance, Published online, November 2015, doi.org/10.1007/s11665-015-1783-8, © ASM International.

88-15   Peng Zhang, Zhenming Li, Baoliang Liu, Wenjiang Ding and Liming Peng, Improved tensile properties of a new aluminum alloy for high pressure die casting, Materials Science & Engineering A651(2016)376–390, Available online, November 2015.

83-15   Zu-Qi Hu, Xin-Jian Zhang and Shu-Sen Wu, Microstructure, Mechanical Properties and Die-Filling Behavior of High-Performance Die-Cast Al–Mg–Si–Mn Alloy, Acta Metall. Sin. (Engl. Lett.), doi.org/10.1007/s40195-015-0332-7, © The Chinese Society for Metals and Springer-Verlag Berlin Heidelberg 2015.

82-15   J. Müller, L. Xue, M.C. Carter, C. Thoma, M. Fehlbier and M. Todte, A Die Spray Cooling Model for Thermal Die Cycling Simulations, 2015 Die Casting Congress & Exposition, Indianapolis, IN, October 2015

81-15   M. T. Murray, L.F. Hansen, L. Chilcott, E. Li and A.M. Murray, Case Studies in the Use of Simulation- Improved Yield and Reduced Time to Market, 2015 Die Casting Congress & Exposition, Indianapolis, IN, October 2015

80-15   R. Bhola, S. Chandra and D. Souders, Predicting Castability of Thin-Walled Parts for the HPDC Process Using Simulations, 2015 Die Casting Congress & Exposition, Indianapolis, IN, October 2015

76-15   Prosenjit Das, Sudip K. Samanta, Shashank Tiwari and Pradip Dutta, Die Filling Behaviour of Semi Solid A356 Al Alloy Slurry During Rheo Pressure Die Casting, Transactions of the Indian Institute of Metals, pp 1-6, October 2015

74-15   Murat KORU and Orhan SERÇE, Yüksek Basınçlı Döküm Prosesinde Enjeksiyon Parametrelerine Bağlı Olarak Döküm Simülasyon, Cumhuriyet University Faculty of Science, Science Journal (CSJ), Vol. 36, No: 5 (2015) ISSN: 1300-1949, May 2015

69-15   A. Viswanath, S. Sivaraman, U. T. S. Pillai, Computer Simulation of Low Pressure Casting Process Using FLOW-3D, Materials Science Forum, Vols. 830-831, pp. 45-48, September 2015

68-15   J. Aneesh Kumar, K. Krishnakumar and S. Savithri, Computer Simulation of Centrifugal Casting Process Using FLOW-3D, Materials Science Forum, Vols. 830-831, pp. 53-56, September 2015

59-15   F. Hosseini Yekta and S. A. Sadough Vanini, Simulation of the flow of semi-solid steel alloy using an enhanced model, Metals and Materials International, August 2015.

44-15   Ulrich E. Klotz, Tiziana Heiss and Dario Tiberto, Platinum investment casting material properties, casting simulation and optimum process parameters, Jewelry Technology Forum 2015

41-15   M. Barkhudarov and R. Pirovano, Minimizing Air Entrainment in High Pressure Die Casting Shot Sleeves, GIFA 2015, Düsseldorf, Germany

40-15   M. Todte, A. Fent, and H. Lang, Simulation in support of the development of innovative processes in the casting industry, GIFA 2015, Düsseldorf, Germany

19-15   Bruce Morey, Virtual casting improves powertrain design, Automotive Engineering, SAE International, March 2015.

15-15   K.S. Oh, J.D. Lee, S.J. Kim and J.Y. Choi, Development of a large ingot continuous caster, Metall. Res. Technol. 112, 203 (2015) © EDP Sciences, 2015, doi.org/10.1051/metal/2015006, www.metallurgical-research.org

14-15   Tiziana Heiss, Ulrich E. Klotz and Dario Tiberto, Platinum Investment Casting, Part I: Simulation and Experimental Study of the Casting Process, Johnson Matthey Technol. Rev., 2015, 59, (2), 95, doi.org/10.1595/205651315×687399

138-14 Christopher Thoma, Wolfram Volk, Ruben Heid, Klaus Dilger, Gregor Banner and Harald Eibisch, Simulation-based prediction of the fracture elongation as a failure criterion for thin-walled high-pressure die casting components, International Journal of Metalcasting, Vol. 8, No. 4, pp. 47-54, 2014. doi.org/10.1007/BF03355594

107-14  Mehran Seyed Ahmadi, Dissolution of Si in Molten Al with Gas Injection, ProQuest Dissertations And Theses; Thesis (Ph.D.), University of Toronto (Canada), 2014; Publication Number: AAT 3637106; ISBN: 9781321195231; Source: Dissertation Abstracts International, Volume: 76-02(E), Section: B.; 191 p.

99-14   R. Bhola and S. Chandra, Predicting Castability for Thin-Walled HPDC Parts, Foundry Management Technology, December 2014

92-14   Warren Bishenden and Changhua Huang, Venting design and process optimization of die casting process for structural components; Part II: Venting design and process optimization, Die Casting Engineer, November 2014

90-14   Ken’ichi Kanazawa, Ken’ichi Yano, Jun’ichi Ogura, and Yasunori Nemoto, Optimum Runner Design for Die-Casting using CFD Simulations and Verification with Water-Model Experiments, Proceedings of the ASME 2014 International Mechanical Engineering Congress and Exposition, IMECE2014, November 14-20, 2014, Montreal, Quebec, Canada, IMECE2014-37419

89-14   P. Kapranos, C. Carney, A. Pola, and M. Jolly, Advanced Casting Methodologies: Investment Casting, Centrifugal Casting, Squeeze Casting, Metal Spinning, and Batch Casting, In Comprehensive Materials Processing; McGeough, J., Ed.; 2014, Elsevier Ltd., 2014; Vol. 5, pp 39–67.

77-14   Andrei Y. Korotchenko, Development of Scientific and Technological Approaches to Casting Net-Shaped Castings in Sand Molds Free of Shrinkage Defects and Hot Tears, Post-doctoral thesis: Russian State Technological University, 2014. In Russian.

69-14   L. Xue, M.C. Carter, A.V. Catalina, Z. Lin, C. Li, and C. Qiu, Predicting, Preventing Core Gas Defects in Steel Castings, Modern Casting, September 2014

68-14   L. Xue, M.C. Carter, A.V. Catalina, Z. Lin, C. Li, and C. Qiu, Numerical Simulation of Core Gas Defects in Steel Castings, Copyright 2014 American Foundry Society, 118th Metalcasting Congress, April 8 – 11, 2014, Schaumburg, IL

51-14   Jesus M. Blanco, Primitivo Carranza, Rafael Pintos, Pedro Arriaga, and Lakhdar Remaki, Identification of Defects Originated during the Filling of Cast Pieces through Particles Modelling, 11th World Congress on Computational Mechanics (WCCM XI), 5th European Conference on Computational Mechanics (ECCM V), 6th European Conference on Computational Fluid Dynamics (ECFD VI), E. Oñate, J. Oliver and A. Huerta (Eds)

47-14   B. Vijaya Ramnatha, C.Elanchezhiana, Vishal Chandrasekhar, A. Arun Kumarb, S. Mohamed Asif, G. Riyaz Mohamed, D. Vinodh Raj , C .Suresh Kumar, Analysis and Optimization of Gating System for Commutator End Bracket, Procedia Materials Science 6 ( 2014 ) 1312 – 1328, 3rd International Conference on Materials Processing and Characterisation (ICMPC 2014)

42-14  Bing Zhou, Yong-lin Kang, Guo-ming Zhu, Jun-zhen Gao, Ming-fan Qi, and Huan-huan Zhang, Forced convection rheoforming process for preparation of 7075 aluminum alloy semisolid slurry and its numerical simulation, Trans. Nonferrous Met. Soc. China 24(2014) 1109−1116

37-14    A. Karwinski, W. Lesniewski, P. Wieliczko, and M. Malysza, Casting of Titanium Alloys in Centrifugal Induction Furnaces, Archives of Metallurgy and Materials, Volume 59, Issue 1, doi.org/10.2478/amm-2014-0068, 2014.

26-14    Bing Zhou, Yonglin Kang, Mingfan Qi, Huanhuan Zhang and Guoming ZhuR-HPDC Process with Forced Convection Mixing Device for Automotive Part of A380 Aluminum Alloy, Materials 2014, 7, 3084-3105; doi.org/10.3390/ma7043084

20-14  Johannes Hartmann, Tobias Fiegl, Carolin Körner, Aluminum integral foams with tailored density profile by adapted blowing agents, Applied Physics A, doi.org/10.1007/s00339-014-8377-4, March 2014.

19-14    A.Y. Korotchenko, N.A. Nikiforova, E.D. Demjanov, N.C. Larichev, The Influence of the Filling Conditions on the Service Properties of the Part Side Frame, Russian Foundryman, 1 (January), pp 40-43, 2014. In Russian.

11-14 B. Fuchs and C. Körner, Mesh resolution consideration for the viability prediction of lost salt cores in the high pressure die casting process, Progress in Computational Fluid Dynamics, Vol. 14, No. 1, 2014, Copyright © 2014 Inderscience Enterprises Ltd.

08-14 FY Hsu, SW Wang, and HJ Lin, The External and Internal Shrinkages in Aluminum Gravity Castings, Shape Casting: 5th International Symposium 2014. Available online at Google Books

103-13  B. Fuchs, H. Eibisch and C. Körner, Core Viability Simulation for Salt Core Technology in High-Pressure Die Casting, International Journal of Metalcasting, July 2013, Volume 7, Issue 3, pp 39–45

94-13    Randall S. Fielding, J. Crapps, C. Unal, and J.R.Kennedy, Metallic Fuel Casting Development and Parameter Optimization Simulations, International Conference on Fast reators and Related Fuel Cycles (FR13), 4-7 March 2013, Paris France

90-13  A. Karwińskia, M. Małyszaa, A. Tchórza, A. Gila, B. Lipowska, Integration of Computer Tomography and Simulation Analysis in Evaluation of Quality of Ceramic-Carbon Bonded Foam Filter, Archives of Foundry Engineering, doi.org/10.2478/afe-2013-0084, Published quarterly as the organ of the Foundry Commission of the Polish Academy of Sciences, ISSN, (2299-2944), Volume 13, Issue 4/2013

88-13  Litie and Metallurgia (Casting and Metallurgy), 3 (72), 2013, N.V.Sletova, I.N.Volnov, S.P.Zadrutsky, V.A.Chaikin, Modeling of the Process of Removing Non-metallic Inclusions in Aluminum Alloys Using the FLOW-3D program, pp 138-140. In Russian.

85-13    Michał Szucki,Tomasz Goraj, Janusz Lelito, Józef S. Suchy, Numerical Analysis of Solid Particles Flow in Liquid Metal, XXXVII International Scientific Conference Foundryman’ Day 2013, Krakow, 28-29 November 2013

84-13  Körner, C., Schwankl, M., Himmler, D., Aluminum-Aluminum compound castings by electroless deposited zinc layers, Journal of Materials Processing Technology (2014), doi.org/10.1016/j.jmatprotec.2013.12.01483-13.

77-13  Antonio Armillotta & Raffaello Baraggi & Simone Fasoli, SLM tooling for die casting with conformal cooling channels, The International Journal of Advanced Manufacturing Technology, doi.org/10.1007/s00170-013-5523-7, December 2013.

64-13   Johannes Hartmann, Christina Blümel, Stefan Ernst, Tobias Fiegl, Karl-Ernst Wirth, Carolin Körner, Aluminum integral foam castings with microcellular cores by nano-functionalization, J Mater Sci, doi.org/10.1007/s10853-013-7668-z, September 2013.

46-13  Nicholas P. Orenstein, 3D Flow and Temperature Analysis of Filling a Plutonium Mold, LA-UR-13-25537, Approved for public release; distribution is unlimited. Los Alamos Annual Student Symposium 2013, 2013-07-24 (Rev.1)

42-13   Yang Yue, William D. Griffiths, and Nick R. Green, Modelling of the Effects of Entrainment Defects on Mechanical Properties in a Cast Al-Si-Mg Alloy, Materials Science Forum, 765, 225, 2013.

39-13  J. Crapps, D.S. DeCroix, J.D Galloway, D.A. Korzekwa, R. Aikin, R. Fielding, R. Kennedy, C. Unal, Separate effects identification via casting process modeling for experimental measurement of U-Pu-Zr alloys, Journal of Nuclear Materials, 15 July 2013.

35-13   A. Pari, Real Life Problem Solving through Simulations in the Die Casting Industry – Case Studies, © Die Casting Engineer, July 2013.

34-13  Martin Lagler, Use of Simulation to Predict the Viability of Salt Cores in the HPDC Process – Shot Curve as a Decisive Criterion, © Die Casting Engineer, July 2013.

24-13    I.N.Volnov, Optimizatsia Liteynoi Tekhnologii, (Casting Technology Optimization), Liteyshik Rossii (Russian Foundryman), 3, 2013, 27-29. In Russian

23-13  M.R. Barkhudarov, I.N. Volnov, Minimizatsia Zakhvata Vozdukha v Kamere Pressovania pri Litie pod Davleniem, (Minimization of Air Entrainment in the Shot Sleeve During High Pressure Die Casting), Liteyshik Rossii (Russian Foundryman), 3, 2013, 30-34. In Russian

09-13  M.C. Carter and L. Xue, Simulating the Parameters that Affect Core Gas Defects in Metal Castings, Copyright 2012 American Foundry Society, Presented at the 2013 CastExpo, St. Louis, Missouri, April 2013

08-13  C. Reilly, N.R. Green, M.R. Jolly, J.-C. Gebelin, The Modelling Of Oxide Film Entrainment In Casting Systems Using Computational Modelling, Applied Mathematical Modelling, http://dx.doi.org/10.1016/j.apm.2013.03.061, April 2013.

03-13  Alexandre Reikher and Krishna M. Pillai, A fast simulation of transient metal flow and solidification in a narrow channel. Part II. Model validation and parametric study, Int. J. Heat Mass Transfer (2013), http://dx.doi.org/10.1016/j.ijheatmasstransfer.2012.12.061.

02-13  Alexandre Reikher and Krishna M. Pillai, A fast simulation of transient metal flow and solidification in a narrow channel. Part I: Model development using lubrication approximation, Int. J. Heat Mass Transfer (2013), http://dx.doi.org/10.1016/j.ijheatmasstransfer.2012.12.060.

116-12  Jufu Jianga, Ying Wang, Gang Chena, Jun Liua, Yuanfa Li and Shoujing Luo, “Comparison of mechanical properties and microstructure of AZ91D alloy motorcycle wheels formed by die casting and double control forming, Materials & Design, Volume 40, September 2012, Pages 541-549.

107-12  F.K. Arslan, A.H. Hatman, S.Ö. Ertürk, E. Güner, B. Güner, An Evaluation for Fundamentals of Die Casting Materials Selection and Design, IMMC’16 International Metallurgy & Materials Congress, Istanbul, Turkey, 2012.

103-12 WU Shu-sen, ZHONG Gu, AN Ping, WAN Li, H. NAKAE, Microstructural characteristics of Al−20Si−2Cu−0.4Mg−1Ni alloy formed by rheo-squeeze casting after ultrasonic vibration treatment, Transactions of Nonferrous Metals Society of China, 22 (2012) 2863-2870, November 2012. Full paper available online.

109-12 Alexandre Reikher, Numerical Analysis of Die-Casting Process in Thin Cavities Using Lubrication Approximation, Ph.D. Thesis: The University of Wisconsin Milwaukee, Engineering Department (2012) Theses and Dissertations. Paper 65.

97-12 Hong Zhou and Li Heng Luo, Filling Pattern of Step Gating System in Lost Foam Casting Process and its Application, Advanced Materials Research, Volumes 602-604, Progress in Materials and Processes, 1916-1921, December 2012.

93-12  Liangchi Zhang, Chunliang Zhang, Jeng-Haur Horng and Zichen Chen, Functions of Step Gating System in the Lost Foam Casting Process, Advanced Materials Research, 591-593, 940, DOI: 10.4028/www.scientific.net/AMR.591-593.940, November 2012.

91-12  Hong Yan, Jian Bin Zhu, Ping Shan, Numerical Simulation on Rheo-Diecasting of Magnesium Matrix Composites, 10.4028/www.scientific.net/SSP.192-193.287, Solid State Phenomena, 192-193, 287.

89-12  Alexandre Reikher and Krishna M. Pillai, A Fast Numerical Simulation for Modeling Simultaneous Metal Flow and Solidification in Thin Cavities Using the Lubrication Approximation, Numerical Heat Transfer, Part A: Applications: An International Journal of Computation and Methodology, 63:2, 75-100, November 2012.

82-12  Jufu Jiang, Gang Chen, Ying Wang, Zhiming Du, Weiwei Shan, and Yuanfa Li, Microstructure and mechanical properties of thin-wall and high-rib parts of AM60B Mg alloy formed by double control forming and die casting under the optimal conditions, Journal of Alloys and Compounds, http://dx.doi.org/10.1016/j.jallcom.2012.10.086, October 2012.

78-12   A. Pari, Real Life Problem Solving through Simulations in the Die Casting Industry – Case Studies, 2012 Die Casting Congress & Exposition, © NADCA, October 8-10, 2012, Indianapolis, IN.

77-12  Y. Wang, K. Kabiri-Bamoradian and R.A. Miller, Rheological behavior models of metal matrix alloys in semi-solid casting process, 2012 Die Casting Congress & Exposition, © NADCA, October 8-10, 2012, Indianapolis, IN.

76-12  A. Reikher and H. Gerber, Analysis of Solidification Parameters During the Die Cast Process, 2012 Die Casting Congress & Exposition, © NADCA, October 8-10, 2012, Indianapolis, IN.

75-12 R.A. Miller, Y. Wang and K. Kabiri-Bamoradian, Estimating Cavity Fill Time, 2012 Die Casting Congress & Exposition, © NADCA, October 8-10, 2012Indianapolis, IN.

65-12  X.H. Yang, T.J. Lu, T. Kim, Influence of non-conducting pore inclusions on phase change behavior of porous media with constant heat flux boundaryInternational Journal of Thermal Sciences, Available online 10 October 2012. Available online at SciVerse.

55-12  Hejun Li, Pengyun Wang, Lehua Qi, Hansong Zuo, Songyi Zhong, Xianghui Hou, 3D numerical simulation of successive deposition of uniform molten Al droplets on a moving substrate and experimental validation, Computational Materials Science, Volume 65, December 2012, Pages 291–301.

52-12 Hongbing Ji, Yixin Chen and Shengzhou Chen, Numerical Simulation of Inner-Outer Couple Cooling Slab Continuous Casting in the Filling Process, Advanced Materials Research (Volumes 557-559), Advanced Materials and Processes II, pp. 2257-2260, July 2012.

47-12    Petri Väyrynen, Lauri Holappa, and Seppo Louhenkilpi, Simulation of Melting of Alloying Materials in Steel Ladle, SCANMET IV – 4th International Conference on Process Development in Iron and Steelmaking, Lulea, Sweden, June 10-13, 2012.

46-12  Bin Zhang and Dave Salee, Metal Flow and Heat Transfer in Billet DC Casting Using Wagstaff® Optifill™ Metal Distribution Systems, 5th International Metal Quality Workshop, United Arab Emirates Dubai, March 18-22, 2012.

45-12 D.R. Gunasegaram, M. Givord, R.G. O’Donnell and B.R. Finnin, Improvements engineered in UTS and elongation of aluminum alloy high pressure die castings through the alteration of runner geometry and plunger velocity, Materials Science & Engineering.

44-12    Antoni Drys and Stefano Mascetti, Aluminum Casting Simulations, Desktop Engineering, September 2012

42-12   Huizhen Duan, Jiangnan Shen and Yanping Li, Comparative analysis of HPDC process of an auto part with ProCAST and FLOW-3D, Applied Mechanics and Materials Vols. 184-185 (2012) pp 90-94, Online available since 2012/Jun/14 at www.scientific.net, © (2012) Trans Tech Publications, Switzerland, doi:10.4028/www.scientific.net/AMM.184-185.90.

41-12    Deniece R. Korzekwa, Cameron M. Knapp, David A. Korzekwa, and John W. Gibbs, Co-Design – Fabrication of Unalloyed Plutonium, LA-UR-12-23441, MDI Summer Research Group Workshop Advanced Manufacturing, 2012-07-25/2012-07-26 (Los Alamos, New Mexico, United States)

29-12  Dario Tiberto and Ulrich E. Klotz, Computer simulation applied to jewellery casting: challenges, results and future possibilities, IOP Conf. Ser.: Mater. Sci. Eng.33 012008. Full paper available at IOP.

28-12  Y Yue and N R Green, Modelling of different entrainment mechanisms and their influences on the mechanical reliability of Al-Si castings, 2012 IOP Conf. Ser.: Mater. Sci. Eng. 33,012072.Full paper available at IOP.

27-12  E Kaschnitz, Numerical simulation of centrifugal casting of pipes, 2012 IOP Conf. Ser.: Mater. Sci. Eng. 33 012031, Issue 1. Full paper available at IOP.

15-12  C. Reilly, N.R Green, M.R. Jolly, The Present State Of Modeling Entrainment Defects In The Shape Casting Process, Applied Mathematical Modelling, Available online 27 April 2012, ISSN 0307-904X, 10.1016/j.apm.2012.04.032.

12-12   Andrei Starobin, Tony Hirt, Hubert Lang, and Matthias Todte, Core drying simulation and validation, International Foundry Research, GIESSEREIFORSCHUNG 64 (2012) No. 1, ISSN 0046-5933, pp 2-5

10-12  H. Vladimir Martínez and Marco F. Valencia (2012). Semisolid Processing of Al/β-SiC Composites by Mechanical Stirring Casting and High Pressure Die Casting, Recent Researches in Metallurgical Engineering – From Extraction to Forming, Dr Mohammad Nusheh (Ed.), ISBN: 978-953-51-0356-1, InTech

07-12     Amir H. G. Isfahani and James M. Brethour, Simulating Thermal Stresses and Cooling Deformations, Die Casting Engineer, March 2012

06-12   Shuisheng Xie, Youfeng He and Xujun Mi, Study on Semi-solid Magnesium Alloys Slurry Preparation and Continuous Roll-casting Process, Magnesium Alloys – Design, Processing and Properties, ISBN: 978-953-307-520-4, InTech.

04-12 J. Spangenberg, N. Roussel, J.H. Hattel, H. Stang, J. Skocek, M.R. Geiker, Flow induced particle migration in fresh concrete: Theoretical frame, numerical simulations and experimental results on model fluids, Cement and Concrete Research, http://dx.doi.org/10.1016/j.cemconres.2012.01.007, February 2012.

01-12   Lee, B., Baek, U., and Han, J., Optimization of Gating System Design for Die Casting of Thin Magnesium Alloy-Based Multi-Cavity LCD Housings, Journal of Materials Engineering and Performance, Springer New York, Issn: 1059-9495, 10.1007/s11665-011-0111-1, Volume 1 / 1992 – Volume 21 / 2012. Available online at Springer Link.

104-11  Fu-Yuan Hsu and Huey Jiuan Lin, Foam Filters Used in Gravity Casting, Metall and Materi Trans B (2011) 42: 1110. doi:10.1007/s11663-011-9548-8.

99-11    Eduardo Trejo, Centrifugal Casting of an Aluminium Alloy, thesis: Doctor of Philosophy, Metallurgy and Materials School of Engineering University of Birmingham, October 2011. Full paper available upon request.

93-11  Olga Kononova, Andrejs Krasnikovs ,Videvuds Lapsa,Jurijs Kalinka and Angelina Galushchak, Internal Structure Formation in High Strength Fiber Concrete during Casting, World Academy of Science, Engineering and Technology 59 2011

76-11  J. Hartmann, A. Trepper, and C. Körner, Aluminum Integral Foams with Near-Microcellular Structure, Advanced Engineering Materials 2011, Volume 13 (2011) No. 11, © Wiley-VCH

71-11  Fu-Yuan Hsu and Yao-Ming Yang Confluence Weld in an Aluminum Gravity Casting, Journal of Materials Processing Technology, Available online 23 November 2011, ISSN 0924-0136, 10.1016/j.jmatprotec.2011.11.006.

65-11     V.A. Chaikin, A.V. Chaikin, I.N.Volnov, A Study of the Process of Late Modification Using Simulation, in Zagotovitelnye Proizvodstva v Mashinostroenii, 10, 2011, 8-12. In Russian.

54-11  Ngadia Taha Niane and Jean-Pierre Michalet, Validation of Foundry Process for Aluminum Parts with FLOW-3D Software, Proceedings of the 2011 International Symposium on Liquid Metal Processing and Casting, 2011.

51-11    A. Reikher and H. Gerber, Calculation of the Die Cast parameters of the Thin Wall Aluminum Cast Part, 2011 Die Casting Congress & Tabletop, Columbus, OH, September 19-21, 2011

50-11   Y. Wang, K. Kabiri-Bamoradian, and R.A. Miller, Runner design optimization based on CFD simulation for a die with multiple cavities, 2011 Die Casting Congress & Tabletop, Columbus, OH, September 19-21, 2011

48-11 A. Karwiński, W. Leśniewski, S. Pysz, P. Wieliczko, The technology of precision casting of titanium alloys by centrifugal process, Archives of Foundry Engineering, ISSN: 1897-3310), Volume 11, Issue 3/2011, 73-80, 2011.

46-11  Daniel Einsiedler, Entwicklung einer Simulationsmethodik zur Simulation von Strömungs- und Trocknungsvorgängen bei Kernfertigungsprozessen mittels CFD (Development of a simulation methodology for simulating flow and drying operations in core production processes using CFD), MSc thesis at Technical University of Aalen in Germany (Hochschule Aalen), 2011.

44-11  Bin Zhang and Craig Shaber, Aluminum Ingot Thermal Stress Development Modeling of the Wagstaff® EpsilonTM Rolling Ingot DC Casting System during the Start-up Phase, Materials Science Forum Vol. 693 (2011) pp 196-207, © 2011 Trans Tech Publications, July, 2011.

43-11 Vu Nguyen, Patrick Rohan, John Grandfield, Alex Levin, Kevin Naidoo, Kurt Oswald, Guillaume Girard, Ben Harker, and Joe Rea, Implementation of CASTfill low-dross pouring system for ingot casting, Materials Science Forum Vol. 693 (2011) pp 227-234, © 2011 Trans Tech Publications, July, 2011.

40-11  A. Starobin, D. Goettsch, M. Walker, D. Burch, Gas Pressure in Aluminum Block Water Jacket Cores, © 2011 American Foundry Society, International Journal of Metalcasting/Summer 2011

37-11 Ferencz Peti, Lucian Grama, Analyze of the Possible Causes of Porosity Type Defects in Aluminum High Pressure Diecast Parts, Scientific Bulletin of the Petru Maior University of Targu Mures, Vol. 8 (XXV) no. 1, 2011, ISSN 1841-9267

31-11  Johannes Hartmann, André Trepper, Carolin Körner, Aluminum Integral Foams with Near-Microcellular Structure, Advanced Engineering Materials, 13: n/a. doi: 10.1002/adem.201100035, June 2011.

27-11  A. Pari, Optimization of HPDC Process using Flow Simulation Case Studies, Die Casting Engineer, July 2011

26-11    A. Reikher, H. Gerber, Calculation of the Die Cast Parameters of the Thin Wall Aluminum Die Casting Part, Die Casting Engineer, July 2011

21-11 Thang Nguyen, Vu Nguyen, Morris Murray, Gary Savage, John Carrig, Modelling Die Filling in Ultra-Thin Aluminium Castings, Materials Science Forum (Volume 690), Light Metals Technology V, pp 107-111, 10.4028/www.scientific.net/MSF.690.107, June 2011.

19-11 Jon Spangenberg, Cem Celal Tutum, Jesper Henri Hattel, Nicolas Roussel, Metter Rica Geiker, Optimization of Casting Process Parameters for Homogeneous Aggregate Distribution in Self-Compacting Concrete: A Feasibility Study, © IEEE Congress on Evolutionary Computation, 2011, New Orleans, USA

16-11  A. Starobin, C.W. Hirt, H. Lang, and M. Todte, Core Drying Simulation and Validations, AFS Proceedings 2011, © American Foundry Society, Presented at the 115th Metalcasting Congress, Schaumburg, Illinois, April 2011.

15-11  J. J. Hernández-Ortega, R. Zamora, J. López, and F. Faura, Numerical Analysis of Air Pressure Effects on the Flow Pattern during the Filling of a Vertical Die Cavity, AIP Conf. Proc., Volume 1353, pp. 1238-1243, The 14th International Esaform Conference on Material Forming: Esaform 2011; doi:10.1063/1.3589686, May 2011. Available online.

10-11 Abbas A. Khalaf and Sumanth Shankar, Favorable Environment for Nondentric Morphology in Controlled Diffusion Solidification, DOI: 10.1007/s11661-011-0641-z, © The Minerals, Metals & Materials Society and ASM International 2011, Metallurgical and Materials Transactions A, March 11, 2011.

08-11 Hai Peng Li, Chun Yong Liang, Li Hui Wang, Hong Shui Wang, Numerical Simulation of Casting Process for Gray Iron Butterfly Valve, Advanced Materials Research, 189-193, 260, February 2011.

04-11  C.W. Hirt, Predicting Core Shooting, Drying and Defect Development, Foundry Management & Technology, January 2011.

76-10  Zhizhong Sun, Henry Hu, Alfred Yu, Numerical Simulation and Experimental Study of Squeeze Casting Magnesium Alloy AM50, Magnesium Technology 2010, 2010 TMS Annual Meeting & ExhibitionFebruary 14-18, 2010, Seattle, WA.

68-10  A. Reikher, H. Gerber, K.M. Pillai, T.-C. Jen, Natural Convection—An Overlooked Phenomenon of the Solidification Process, Die Casting Engineer, January 2010

54-10    Andrea Bernardoni, Andrea Borsi, Stefano Mascetti, Alessandro Incognito and Matteo Corrado, Fonderia Leonardo aveva ragione! L’enorme cavallo dedicato a Francesco Sforza era materialmente realizzabile, A&C – Analisis e Calcolo, Giugno 2010. In  Italian.

48-10  J. J. Hernández-Ortega, R. Zamora, J. Palacios, J. López and F. Faura, An Experimental and Numerical Study of Flow Patterns and Air Entrapment Phenomena During the Filling of a Vertical Die Cavity, J. Manuf. Sci. Eng., October 2010, Volume 132, Issue 5, 05101, doi:10.1115/1.4002535.

47-10  A.V. Chaikin, I.N. Volnov, and V.A. Chaikin, Development of Dispersible Mixed Inoculant Compositions Using the FLOW-3D Program, Liteinoe Proizvodstvo, October, 2010, in Russian.

42-10  H. Lakshmi, M.C. Vinay Kumar, Raghunath, P. Kumar, V. Ramanarayanan, K.S.S. Murthy, P. Dutta, Induction reheating of A356.2 aluminum alloy and thixocasting as automobile component, Transactions of Nonferrous Metals Society of China 20(20101) s961-s967.

41-10  Pamela J. Waterman, Understanding Core-Gas Defects, Desktop Engineering, October 2010. Available online at Desktop Engineering. Also published in the Foundry Trade Journal, November 2010.

39-10  Liu Zheng, Jia Yingying, Mao Pingli, Li Yang, Wang Feng, Wang Hong, Zhou Le, Visualization of Die Casting Magnesium Alloy Steering Bracket, Special Casting & Nonferrous Alloys, ISSN: 1001-2249, CN: 42-1148/TG, 2010-04. In Chinese.

37-10  Morris Murray, Lars Feldager Hansen, and Carl Reinhardt, I Have Defects – Now What, Die Casting Engineer, September 2010

36-10  Stefano Mascetti, Using Flow Analysis Software to Optimize Piston Velocity for an HPDC Process, Die Casting Engineer, September 2010. Also available in Italian: Ottimizzare la velocita del pistone in pressofusione.  A & C, Analisi e Calcolo, Anno XII, n. 42, Gennaio 2011, ISSN 1128-3874.

32-10  Guan Hai Yan, Sheng Dun Zhao, Zheng Hui Sha, Parameters Optimization of Semisolid Diecasting Process for Air-Conditioner’s Triple Valve in HPb59-1 Alloy, Advanced Materials Research (Volumes 129 – 131), Vol. Material and Manufacturing Technology, pp. 936-941, DOI: 10.4028/www.scientific.net/AMR.129-131.936, August 2010.

29-10 Zheng Peng, Xu Jun, Zhang Zhifeng, Bai Yuelong, and Shi Likai, Numerical Simulation of Filling of Rheo-diecasting A357 Aluminum Alloy, Special Casting & Nonferrous Alloys, DOI: CNKI:SUN:TZZZ.0.2010-01-024, 2010.

27-10 For an Aerospace Diecasting, Littler Uses Simulation to Reveal Defects, and Win a New Order, Foundry Management & Technology, July 2010

23-10 Michael R. Barkhudarov, Minimizing Air Entrainment, The Canadian Die Caster, June 2010

15-10 David H. Kirkwood, Michel Suery, Plato Kapranos, Helen V. Atkinson, and Kenneth P. Young, Semi-solid Processing of Alloys, 2010, XII, 172 p. 103 illus., 19 in color., Hardcover ISBN: 978-3-642-00705-7.

09-10  Shannon Wetzel, Fullfilling Da Vinci’s Dream, Modern Casting, April 2010.

08-10 B.I. Semenov, K.M. Kushtarov, Semi-solid Manufacturing of Castings, New Industrial Technologies, Publication of Moscow State Technical University n.a. N.E. Bauman, 2009 (in Russian)

07-10 Carl Reilly, Development Of Quantitative Casting Quality Assessment Criteria Using Process Modelling, thesis: The University of Birmingham, March 2010 (Available upon request)

06-10 A. Pari, Optimization of HPDC Process using Flow Simulation – Case Studies, CastExpo ’10, NADCA, Orlando, Florida, March 2010

05-10 M.C. Carter, S. Palit, and M. Littler, Characterizing Flow Losses Occurring in Air Vents and Ejector Pins in High Pressure Die Castings, CastExpo ’10, NADCA, Orlando, Florida, March 2010

04-10 Pamela Waterman, Simulating Porosity Factors, Foundry Management Technology, March 2010, Article available at Foundry Management Technology

03-10 C. Reilly, M.R. Jolly, N.R. Green, JC Gebelin, Assessment of Casting Filling by Modeling Surface Entrainment Events Using CFD, 2010 TMS Annual Meeting & Exhibition (Jim Evans Honorary Symposium), Seattle, Washington, USA, February 14-18, 2010

02-10 P. Väyrynen, S. Wang, J. Laine and S.Louhenkilpi, Control of Fluid Flow, Heat Transfer and Inclusions in Continuous Casting – CFD and Neural Network Studies, 2010 TMS Annual Meeting & Exhibition (Jim Evans Honorary Symposium), Seattle, Washington, USA, February 14-18, 2010

60-09   Somlak Wannarumon, and Marco Actis Grande, Comparisons of Computer Fluid Dynamic Software Programs applied to Jewelry Investment Casting Process, World Academy of Science, Engineering and Technology 55 2009.

59-09   Marco Actis Grande and Somlak Wannarumon, Numerical Simulation of Investment Casting of Gold Jewelry: Experiments and Validations, World Academy of Science, Engineering and Technology, Vol:3 2009-07-24

56-09  Jozef Kasala, Ondrej Híreš, Rudolf Pernis, Start-up Phase Modeling of Semi Continuous Casting Process of Brass Billets, Metal 2009, 19.-21.5.2009

51-09  In-Ting Hong, Huan-Chien Tung, Chun-Hao Chiu and Hung-Shang Huang, Effect of Casting Parameters on Microstructure and Casting Quality of Si-Al Alloy for Vacuum Sputtering, China Steel Technical Report, No. 22, pp. 33-40, 2009.

42-09  P. Väyrynen, S. Wang, S. Louhenkilpi and L. Holappa, Modeling and Removal of Inclusions in Continuous Casting, Materials Science & Technology 2009 Conference & Exhibition, Pittsburgh, Pennsylvania, USA, October 25-29, 2009

41-09 O.Smirnov, P.Väyrynen, A.Kravchenko and S.Louhenkilpi, Modern Methods of Modeling Fluid Flow and Inclusions Motion in Tundish Bath – General View, Proceedings of Steelsim 2009 – 3rd International Conference on Simulation and Modelling of Metallurgical Processes in Steelmaking, Leoben, Austria, September 8-10, 2009

21-09 A. Pari, Case Studies – Optimization of HPDC Process Using Flow Simulation, Die Casting Engineer, July 2009

20-09 M. Sirvio, M. Wos, Casting directly from a computer model by using advanced simulation software, FLOW-3D Cast, Archives of Foundry Engineering Volume 9, Issue 1/2009, 79-82

19-09 Andrei Starobin, C.W. Hirt, D. Goettsch, A Model for Binder Gas Generation and Transport in Sand Cores and Molds, Modeling of Casting, Welding, and Solidification Processes XII, TMS (The Minerals, Metals & Minerals Society), June 2009

11-09 Michael Barkhudarov, Minimizing Air Entrainment in a Shot Sleeve during Slow-Shot Stage, Die Casting Engineer (The North American Die Casting Association ISSN 0012-253X), May 2009

10-09 A. Reikher, H. Gerber, Application of One-Dimensional Numerical Simulation to Optimize Process Parameters of a Thin-Wall Casting in High Pressure Die Casting, Die Casting Engineer (The North American Die Casting Association ISSN 0012-253X), May 2009

7-09 Andrei Starobin, Simulation of Core Gas Evolution and Flow, presented at the North American Die Casting Association – 113th Metalcasting Congress, April 7-10, 2009, Las Vegas, Nevada, USA

6-09 A.Pari, Optimization of HPDC PROCESS: Case Studies, North American Die Casting Association – 113th Metalcasting Congress, April 7-10, 2009, Las Vegas, Nevada, USA

2-09 C. Reilly, N.R. Green and M.R. Jolly, Oxide Entrainment Structures in Horizontal Running Systems, TMS 2009, San Francisco, California, February 2009

30-08 I.N.Volnov, Computer Modeling of Casting of Pipe Fittings, © 2008, Pipe Fittings, 5 (38), 2008. Russian version

28-08 A.V.Chaikin, I.N.Volnov, V.A.Chaikin, Y.A.Ukhanov, N.R.Petrov, Analysis of the Efficiency of Alloy Modifiers Using Statistics and Modeling, © 2008, Liteyshik Rossii (Russian Foundryman), October, 2008

27-08 P. Scarber, Jr., H. Littleton, Simulating Macro-Porosity in Aluminum Lost Foam Castings, American Foundry Society, © 2008, AFS Lost Foam Conference, Asheville, North Carolina, October, 2008

25-08 FMT Staff, Forecasting Core Gas Pressures with Computer Simulation, Foundry Management and Technology, October 28, 2008 © 2008 Penton Media, Inc. Online article

24-08 Core and Mold Gas Evolution, Foundry Management and Technology, January 24, 2008 (excerpted from the FM&T May 2007 issue) © 2008 Penton Media, Inc.

22-08 Mark Littler, Simulation Eliminates Die Casting Scrap, Modern Casting/September 2008

21-08 X. Chen, D. Penumadu, Permeability Measurement and Numerical Modeling for Refractory Porous Materials, AFS Transactions © 2008 American Foundry Society, CastExpo ’08, Atlanta, Georgia, May 2008

20-08 Rolf Krack, Using Solidification Simulations for Optimising Die Cooling Systems, FTJ July/August 2008

19-08 Mark Littler, Simulation Software Eliminates Die Casting Scrap, ECS Casting Innovations, July/August 2008

13-08 T. Yoshimura, K. Yano, T. Fukui, S. Yamamoto, S. Nishido, M. Watanabe and Y. Nemoto, Optimum Design of Die Casting Plunger Tip Considering Air Entrainment, Proceedings of 10th Asian Foundry Congress (AFC10), Nagoya, Japan, May 2008

08-08 Stephen Instone, Andreas Buchholz and Gerd-Ulrich Gruen, Inclusion Transport Phenomena in Casting Furnaces, Light Metals 2008, TMS (The Minerals, Metals & Materials Society), 2008

07-08 P. Scarber, Jr., H. Littleton, Simulating Macro-Porosity in Aluminum Lost Foam Casting, AFS Transactions 2008 © American Foundry Society, CastExpo ’08, Atlanta, Georgia, May 2008

06-08 A. Reikher, H. Gerber and A. Starobin, Multi-Stage Plunger Deceleration System, CastExpo ’08, NADCA, Atlanta, Georgia, May 2008

05-08 Amol Palekar, Andrei Starobin, Alexander Reikher, Die-casting end-of-fill and drop forge viscometer flow transients examined with a coupled-motion numerical model, 68th World Foundry Congress, Chennai, India, February 2008

03-08 Petri J. Väyrynen, Sami K. Vapalahti and Seppo J. Louhenkilpi, On Validation of Mathematical Fluid Flow Models for Simulation of Tundish Water Models and Industrial Examples, AISTech 2008, May 2008

53-07   A. Kermanpur, Sh. Mahmoudi and A. Hajipour, Three-dimensional Numerical Simulation of Metal Flow and Solidification in the Multi-cavity Casting Moulds of Automotive Components, International Journal of Iron & Steel Society of Iran, Article 2, Volume 4, Issue 1, Summer and Autumn 2007, pages 8-15.

36-07 Duque Mesa A. F., Herrera J., Cruz L.J., Fernández G.P. y Martínez H.V., Caracterización Defectológica de Piezas Fundida por Lost Foam Casting Mediante Simulación Numérica, 8° Congreso Iberoamericano de Ingenieria Mecanica, Cusco, Peru, 23 al 25 de Octubre de 2007 (in Spanish)

27-07 A.Y. Korotchenko, A.M. Zarubin, I.A.Korotchenko, Modeling of High Pressure Die Casting Filling, Russian Foundryman, December 2007, pp 15-19. (in Russian)

26-07 I.N. Volnov, Modeling of Casting Processes with Variable Geometry, Russian Foundryman, November 2007, pp 27-30. (in Russian)

16-07 P. Väyrynen, S. Vapalahti, S. Louhenkilpi, L. Chatburn, M. Clark, T. Wagner, Tundish Flow Model Tuning and Validation – Steady State and Transient Casting Situations, STEELSIM 2007, Graz/Seggau, Austria, September 12-14 2007

11-07 Marco Actis Grande, Computer Simulation of the Investment Casting Process – Widening of the Filling Step, Santa Fe Symposium on Jewelry Manufacturing Technology, May 2007

09-07 Alexandre Reikher and Michael Barkhudarov, Casting: An Analytical Approach, Springer, 1st edition, August 2007, Hardcover ISBN: 978-1-84628-849-4. U.S. Order FormEurope Order Form.

07-07 I.N. Volnov, Casting Modeling Systems – Current State, Problems and Perspectives, (in Russian), Liteyshik Rossii (Russian Foundryman), June 2007

05-07 A.N. Turchin, D.G. Eskin, and L. Katgerman, Solidification under Forced-Flow Conditions in a Shallow Cavity, DOI: 10.1007/s1161-007-9183-9, © The Minerals, Metals & Materials Society and ASM International 2007

04-07 A.N. Turchin, M. Zuijderwijk, J. Pool, D.G. Eskin, and L. Katgerman, Feathery grain growth during solidification under forced flow conditions, © Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved. DOI: 10.1016/j.actamat.2007.02.030, April 2007

03-07 S. Kuyucak, Sponsored Research – Clean Steel Casting Production—Evaluation of Laboratory Castings, Transactions of the American Foundry Society, Volume 115, 111th Metalcasting Congress, May 2007

02-07 Fu-Yuan Hsu, Mark R. Jolly and John Campbell, The Design of L-Shaped Runners for Gravity Casting, Shape Casting: 2nd International Symposium, Edited by Paul N. Crepeau, Murat Tiryakioðlu and John Campbell, TMS (The Minerals, Metals & Materials Society), Orlando, FL, Feb 2007

30-06 X.J. Liu, S.H. Bhavnani, R.A. Overfelt, Simulation of EPS foam decomposition in the lost foam casting process, Journal of Materials Processing Technology 182 (2007) 333–342, © 2006 Elsevier B.V. All rights reserved.

25-06 Michael Barkhudarov and Gengsheng Wei, Modeling Casting on the Move, Modern Casting, August 2006; Modeling of Casting Processes with Variable Geometry, Russian Foundryman, December 2007, pp 10-15. (in Russian)

24-06 P. Scarber, Jr. and C.E. Bates, Simulation of Core Gas Production During Mold Fill, © 2006 American Foundry Society

7-06 M.Y.Smirnov, Y.V.Golenkov, Manufacturing of Cast Iron Bath Tubs Castings using Vacuum-Process in Russia, Russia’s Foundryman, July 2006. In Russian.

6-06 M. Barkhudarov, and G. Wei, Modeling of the Coupled Motion of Rigid Bodies in Liquid Metal, Modeling of Casting, Welding and Advanced Solidification Processes – XI, May 28 – June 2, 2006, Opio, France, eds. Ch.-A. Gandin and M. Bellet, pp 71-78, 2006.

2-06 J.-C. Gebelin, M.R. Jolly and F.-Y. Hsu, ‘Designing-in’ Controlled Filling Using Numerical Simulation for Gravity Sand Casting of Aluminium Alloys, Int. J. Cast Met. Res., 2006, Vol.19 No.1

1-06 Michael Barkhudarov, Using Simulation to Control Microporosity Reduces Die Iterations, Die Casting Engineer, January 2006, pp. 52-54

30-05 H. Xue, K. Kabiri-Bamoradian, R.A. Miller, Modeling Dynamic Cavity Pressure and Impact Spike in Die Casting, Cast Expo ’05, April 16-19, 2005

22-05 Blas Melissari & Stavros A. Argyropoulous, Measurement of Magnitude and Direction of Velocity in High-Temperature Liquid Metals; Part I, Mathematical Modeling, Metallurgical and Materials Transactions B, Volume 36B, October 2005, pp. 691-700

21-05 M.R. Jolly, State of the Art Review of Use of Modeling Software for Casting, TMS Annual Meeting, Shape Casting: The John Campbell Symposium, Eds, M. Tiryakioglu & P.N Crepeau, TMS, Warrendale, PA, ISBN 0-87339-583-2, Feb 2005, pp 337-346

20-05 J-C Gebelin, M.R. Jolly & F-Y Hsu, ‘Designing-in’ Controlled Filling Using Numerical Simulation for Gravity Sand Casting of Aluminium Alloys, TMS Annual Meeting, Shape Casting: The John Campbell Symposium, Eds, M. Tiryakioglu & P.N Crepeau, TMS, Warrendale, PA, ISBN 0-87339-583-2, Feb 2005, pp 355-364

19-05 F-Y Hsu, M.R. Jolly & J Campbell, Vortex Gate Design for Gravity Castings, TMS Annual Meeting, Shape Casting: The John Campbell Symposium, Eds, M. Tiryakioglu & P.N Crepeau, TMS, Warrendale, PA, ISBN 0-87339-583-2, Feb 2005, pp 73-82

18-05 M.R. Jolly, Modelling the Investment Casting Process: Problems and Successes, Japanese Foundry Society, JFS, Tokyo, Sept. 2005

13-05 Xiaogang Yang, Xiaobing Huang, Xiaojun Dai, John Campbell and Joe Tatler, Numerical Modelling of the Entrainment of Oxide Film Defects in Filling of Aluminium Alloy Castings, International Journal of Cast Metals Research, 17 (6), 2004, 321-331

10-05 Carlos Evaristo Esparza, Martha P. Guerro-Mata, Roger Z. Ríos-Mercado, Optimal Design of Gating Systems by Gradient Search Methods, Computational Materials Science, October 2005

6-05 Birgit Hummler-Schaufler, Fritz Hirning, Jurgen Schaufler, A World First for Hatz Diesel and Schaufler Tooling, Die Casting Engineer, May 2005, pp. 18-21

4-05 Rolf Krack, The W35 Topic—A World First, Die Casting World, March 2005, pp. 16-17

3-05 Joerg Frei, Casting Simulations Speed Up Development, Die Casting World, March 2005, p. 14

2-05 David Goettsch and Michael Barkhudarov, Analysis and Optimization of the Transient Stage of Stopper-Rod Pour, Shape Casting: The John Campbell Symposium, The Minerals, Metals & Materials Society, 2005

36-04  Ik Min Park, Il Dong Choi, Yong Ho Park, Development of Light-Weight Al Scroll Compressor for Car Air Conditioner, Materials Science Forum, Designing, Processing and Properties of Advanced Engineering Materials, 449-452, 149, March 2004.

32-04 D.H. Kirkwood and P.J Ward, Numerical Modelling of Semi-Solid Flow under Processing Conditions, steel research int. 75 (2004), No. 8/9

30-04 Haijing Mao, A Numerical Study of Externally Solidified Products in the Cold Chamber Die Casting Process, thesis: The Ohio State University, 2004 (Available upon request)

28-04 Z. Cao, Z. Yang, and X.L. Chen, Three-Dimensional Simulation of Transient GMA Weld Pool with Free Surface, Supplement to the Welding Journal, June 2004.

23-04 State of the Art Use of Computational Modelling in the Foundry Industry, 3rd International Conference Computational Modelling of Materials III, Sicily, Italy, June 2004, Advances in Science and Technology,  Eds P. Vincenzini & A Lami, Techna Group Srl, Italy, ISBN: 88-86538-46-4, Part B, pp 479-490

22-04 Jerry Fireman, Computer Simulation Helps Reduce Scrap, Die Casting Engineer, May 2004, pp. 46-49

21-04 Joerg Frei, Simulation—A Safe and Quick Way to Good Components, Aluminium World, Volume 3, Issue 2, pp. 42-43

20-04 J.-C. Gebelin, M.R. Jolly, A. M. Cendrowicz, J. Cirre and S. Blackburn, Simulation of Die Filling for the Wax Injection Process – Part II Numerical Simulation, Metallurgical and Materials Transactions, Volume 35B, August 2004

14-04 Sayavur I. Bakhtiyarov, Charles H. Sherwin, and Ruel A. Overfelt, Hot Distortion Studies In Phenolic Urethane Cold Box System, American Foundry Society, 108th Casting Congress, June 12-15, 2004, Rosemont, IL, USA

13-04 Sayavur I. Bakhtiyarov and Ruel A. Overfelt, First V-Process Casting of Magnesium, American Foundry Society, 108th Casting Congress, June 12-15, 2004, Rosemont, IL, USA

5-04 C. Schlumpberger & B. Hummler-Schaufler, Produktentwicklung auf hohem Niveau (Product Development on a High Level), Druckguss Praxis, January 2004, pp 39-42 (in German).

3-04 Charles Bates, Dealing with Defects, Foundry Management and Technology, February 2004, pp 23-25

1-04 Laihua Wang, Thang Nguyen, Gary Savage and Cameron Davidson, Thermal and Flow Modeling of Ladling and Injection in High Pressure Die Casting Process, International Journal of Cast Metals Research, vol. 16 No 4 2003, pp 409-417

2-03 J-C Gebelin, AM Cendrowicz, MR Jolly, Modeling of the Wax Injection Process for the Investment Casting Process – Prediction of Defects, presented at the Third International Conference on Computational Fluid Dynamics in the Minerals and Process Industries, December 10-12, 2003, Melbourne, Australia, pp. 415-420

29-03 C. W. Hirt, Modeling Shrinkage Induced Micro-porosity, Flow Science Technical Note (FSI-03-TN66)

28-03 Thixoforming at the University of Sheffield, Diecasting World, September 2003, pp 11-12

26-03 William Walkington, Gas Porosity-A Guide to Correcting the Problems, NADCA Publication: 516

22-03 G F Yao, C W Hirt, and M Barkhudarov, Development of a Numerical Approach for Simulation of Sand Blowing and Core Formation, in Modeling of Casting, Welding, and Advanced Solidification Process-X”, Ed. By Stefanescu et al pp. 633-639, 2003

21-03 E F Brush Jr, S P Midson, W G Walkington, D T Peters, J G Cowie, Porosity Control in Copper Rotor Die Castings, NADCA Indianapolis Convention Center, Indianapolis, IN September 15-18, 2003, T03-046

12-03 J-C Gebelin & M.R. Jolly, Modeling Filters in Light Alloy Casting Processes,  Trans AFS, 2002, 110, pp. 109-120

11-03 M.R. Jolly, Casting Simulation – How Well Do Reality and Virtual Casting Match – A State of the Art Review, Intl. J. Cast Metals Research, 2002, 14, pp. 303-313

10-03 Gebelin., J-C and Jolly, M.R., Modeling of the Investment Casting Process, Journal of  Materials Processing Tech., Vol. 135/2-3, pp. 291 – 300

9-03 Cox, M, Harding, R.A. and Campbell, J., Optimised Running System Design for Bottom Filled Aluminium Alloy 2L99 Investment Castings, J. Mat. Sci. Tech., May 2003, Vol. 19, pp. 613-625

8-03 Von Alexander Schrey and Regina Reek, Numerische Simulation der Kernherstellung, (Numerical Simulation of Core Blowing), Giesserei, June 2003, pp. 64-68 (in German)

7-03 J. Zuidema Jr., L Katgerman, Cyclone separation of particles in aluminum DC Casting, Proceedings from the Tenth International Conference on Modeling of Casting, Welding and Advanced Solidification Processes, Destin, FL, May 2003, pp. 607-614

6-03 Jean-Christophe Gebelin and Mark Jolly, Numerical Modeling of Metal Flow Through Filters, Proceedings from the Tenth International Conference on Modeling of Casting, Welding and Advanced Solidification Processes, Destin, FL, May 2003, pp. 431-438

5-03 N.W. Lai, W.D. Griffiths and J. Campbell, Modelling of the Potential for Oxide Film Entrainment in Light Metal Alloy Castings, Proceedings from the Tenth International Conference on Modeling of Casting, Welding and Advanced Solidification Processes, Destin, FL, May 2003, pp. 415-422

21-02 Boris Lukezic, Case History: Process Modeling Solves Die Design Problems, Modern Casting, February 2003, P 59

20-02 C.W. Hirt and M.R. Barkhudarov, Predicting Defects in Lost Foam Castings, Modern Casting, December 2002, pp 31-33

19-02 Mark Jolly, Mike Cox, Ric Harding, Bill Griffiths and John Campbell, Quiescent Filling Applied to Investment Castings, Modern Casting, December 2002 pp. 36-38

18-02 Simulation Helps Overcome Challenges of Thin Wall Magnesium Diecasting, Foundry Management and Technology, October 2002, pp 13-15

17-02 G Messmer, Simulation of a Thixoforging Process of Aluminum Alloys with FLOW-3D, Institute for Metal Forming Technology, University of Stuttgart

16-02 Barkhudarov, Michael, Computer Simulation of Lost Foam Process, Casting Simulation Background and Examples from Europe and the USA, World Foundrymen Organization, 2002, pp 319-324

15-02 Barkhudarov, Michael, Computer Simulation of Inclusion Tracking, Casting Simulation Background and Examples from Europe and the USA, World Foundrymen Organization, 2002, pp 341-346

14-02 Barkhudarov, Michael, Advanced Simulation of the Flow and Heat Transfer of an Alternator Housing, Casting Simulation Background and Examples from Europe and the USA, World Foundrymen Organization, 2002, pp 219-228

8-02 Sayavur I. Bakhtiyarov, and Ruel A. Overfelt, Experimental and Numerical Study of Bonded Sand-Air Two-Phase Flow in PUA Process, Auburn University, 2002 American Foundry Society, AFS Transactions 02-091, Kansas City, MO

7-02 A Habibollah Zadeh, and J Campbell, Metal Flow Through a Filter System, University of Birmingham, 2002 American Foundry Society, AFS Transactions 02-020, Kansas City, MO

6-02 Phil Ward, and Helen Atkinson, Final Report for EPSRC Project: Modeling of Thixotropic Flow of Metal Alloys into a Die, GR/M17334/01, March 2002, University of Sheffield

5-02 S. I. Bakhtiyarov and R. A. Overfelt, Numerical and Experimental Study of Aluminum Casting in Vacuum-sealed Step Molding, Auburn University, 2002 American Foundry Society, AFS Transactions 02-050, Kansas City, MO

4-02 J. C. Gebelin and M. R. Jolly, Modelling Filters in Light Alloy Casting Processes, University of Birmingham, 2002 American Foundry Society AFS Transactions 02-079, Kansas City, MO

3-02 Mark Jolly, Mike Cox, Jean-Christophe Gebelin, Sam Jones, and Alex Cendrowicz, Fundamentals of Investment Casting (FOCAST), Modelling the Investment Casting Process, Some preliminary results from the UK Research Programme, IRC in Materials, University of Birmingham, UK, AFS2001

49-01   Hua Bai and Brian G. Thomas, Bubble formation during horizontal gas injection into downward-flowing liquid, Metallurgical and Materials Transactions B, Vol. 32, No. 6, pp. 1143-1159, 2001. doi.org/10.1007/s11663-001-0102-y

45-01 Jan Zuidema; Laurens Katgerman; Ivo J. Opstelten;Jan M. Rabenberg, Secondary Cooling in DC Casting: Modelling and Experimental Results, TMS 2001, New Orleans, Louisianna, February 11-15, 2001

43-01 James Andrew Yurko, Fluid Flow Behavior of Semi-Solid Aluminum at High Shear Rates,Ph.D. thesis; Massachusetts Institute of Technology, June 2001. Abstract only; full thesis available at http://dspace.mit.edu/handle/1721.1/8451 (for a fee).

33-01 Juang, S.H., CAE Application on Design of Die Casting Dies, 2001 Conference on CAE Technology and Application, Hsin-Chu, Taiwan, November 2001, (article in Chinese with English-language abstract)

32-01 Juang, S.H. and C. M. Wang, Effect of Feeding Geometry on Flow Characteristics of Magnesium Die Casting by Numerical Analysis, The Preceedings of 6th FADMA Conference, Taipei, Taiwan, July 2001, Chinese language with English abstract

26-01 C. W. Hirt., Predicting Defects in Lost Foam Castings, December 13, 2001

21-01 P. Scarber Jr., Using Liquid Free Surface Areas as a Predictor of Reoxidation Tendency in Metal Alloy Castings, presented at the Steel Founders’ Society of American, Technical and Operating Conference, October 2001

20-01 P. Scarber Jr., J. Griffin, and C. E. Bates, The Effect of Gating and Pouring Practice on Reoxidation of Steel Castings, presented at the Steel Founders’ Society of American, Technical and Operating Conference, October 2001

19-01 L. Wang, T. Nguyen, M. Murray, Simulation of Flow Pattern and Temperature Profile in the Shot Sleeve of a High Pressure Die Casting Process, CSIRO Manufacturing Science and Technology, Melbourne, Victoria, Australia, Presented by North American Die Casting Association, Oct 29-Nov 1, 2001, Cincinnati, To1-014

18-01 Rajiv Shivpuri, Venkatesh Sankararaman, Kaustubh Kulkarni, An Approach at Optimizing the Ingate Design for Reducing Filling and Shrinkage Defects, The Ohio State University, Columbus, OH, Presented by North American Die Casting Association, Oct 29-Nov 1, 2001, Cincinnati, TO1-052

5-01 Michael Barkhudarov, Simulation Helps Overcome Challenges of Thin Wall Magnesium Diecasting, Diecasting World, March 2001, pp. 5-6

2-01 J. Grindling, Customized CFD Codes to Simulate Casting of Thermosets in Full 3D, Electrical Manufacturing and Coil Winding 2000 Conference, October 31-November 2, 20

20-00 Richard Schuhmann, John Carrig, Thang Nguyen, Arne Dahle, Comparison of Water Analogue Modelling and Numerical Simulation Using Real-Time X-Ray Flow Data in Gravity Die Casting, Australian Die Casting Association Die Casting 2000 Conference, September 3-6, 2000, Melbourne, Victoria, Australia

15-00 M. Sirvio, Vainola, J. Vartianinen, M. Vuorinen, J. Orkas, and S. Devenyi, Fluid Flow Analysis for Designing Gating of Aluminum Castings, Proc. NADCA Conf., Rosemont, IL, Nov 6-8, 1999

14-00 X. Yang, M. Jolly, and J. Campbell, Reduction of Surface Turbulence during Filling of Sand Castings Using a Vortex-flow Runner, Conference for Modeling of Casting, Welding, and Advanced Solidification Processes IX, Aachen, Germany, August 2000

13-00 H. S. H. Lo and J. Campbell, The Modeling of Ceramic Foam Filters, Conference for Modeling of Casting, Welding, and Advanced Solidification Processes IX, Aachen, Germany, August 2000

12-00 M. R. Jolly, H. S. H. Lo, M. Turan and J. Campbell, Use of Simulation Tools in the Practical Development of a Method for Manufacture of Cast Iron Camshafts,” Conference for Modeling of Casting, Welding, and Advanced Solidification Processes IX, Aachen, Germany, August, 2000

14-99 J Koke, and M Modigell, Time-Dependent Rheological Properties of Semi-solid Metal Alloys, Institute of Chemical Engineering, Aachen University of Technology, Mechanics of Time-Dependent Materials 3: 15-30, 1999

12-99 Grun, Gerd-Ulrich, Schneider, Wolfgang, Ray, Steven, Marthinusen, Jan-Olaf, Recent Improvements in Ceramic Foam Filter Design by Coupled Heat and Fluid Flow Modeling, Proc TMS Annual Meeting, 1999, pp. 1041-1047

10-99 Bongcheol Park and Jerald R. Brevick, Computer Flow Modeling of Cavity Pre-fill Effects in High Pressure Die Casting, NADCA Proceedings, Cleveland T99-011, November, 1999

8-99 Brad Guthrie, Simulation Reduces Aluminum Die Casting Cost by Reducing Volume, Die Casting Engineer Magazine, September/October 1999, pp. 78-81

7-99 Fred L. Church, Virtual Reality Predicts Cast Metal Flow, Modern Metals, September, 1999, pp. 67F-J

19-98 Grun, Gerd-Ulrich, & Schneider, Wolfgang, Numerical Modeling of Fluid Flow Phenomena in the Launder-integrated Tool Within Casting Unit Development, Proc TMS Annual Meeting, 1998, pp. 1175-1182

18-98 X. Yang & J. Campbell, Liquid Metal Flow in a Pouring Basin, Int. J. Cast Metals Res, 1998, 10, pp. 239-253

15-98 R. Van Tol, Mould Filling of Horizontal Thin-Wall Castings, Delft University Press, The Netherlands, 1998

14-98 J. Daughtery and K. A. Williams, Thermal Modeling of Mold Material Candidates for Copper Pressure Die Casting of the Induction Motor Rotor Structure, Proc. Int’l Workshop on Permanent Mold Casting of Copper-Based Alloys, Ottawa, Ontario, Canada, Oct. 15-16, 1998

10-98 C. W. Hirt, and M.R. Barkhudarov, Lost Foam Casting Simulation with Defect Prediction, Flow Science Inc, presented at Modeling of Casting, Welding and Advanced Solidification Processes VIII Conference, June 7-12, 1998, Catamaran Hotel, San Diego, California

9-98 M. R. Barkhudarov and C. W. Hirt, Tracking Defects, Flow Science Inc, presented at the 1st International Aluminum Casting Technology Symposium, 12-14 October 1998, Rosemont, IL

5-98 J. Righi, Computer Simulation Helps Eliminate Porosity, Die Casting Management Magazine, pp. 36-38, January 1998

3-98 P. Kapranos, M. R. Barkhudarov, D. H. Kirkwood, Modeling of Structural Breakdown during Rapid Compression of Semi-Solid Alloy Slugs, Dept. Engineering Materials, The University of Sheffield, Sheffield S1 3JD, U.K. and Flow Science Inc, USA, Presented at the 5th International Conference Semi-Solid Processing of Alloys and Composites, Colorado School of Mines, Golden, CO, 23-25 June 1998

1-98 U. Jerichow, T. Altan, and P. R. Sahm, Semi Solid Metal Forming of Aluminum Alloys-The Effect of Process Variables Upon Material Flow, Cavity Fill and Mechanical Properties, The Ohio State University, Columbus, OH, published in Die Casting Engineer, p. 26, Jan/Feb 1998

8-97 Michael Barkhudarov, High Pressure Die Casting Simulation Using FLOW-3D, Die Casting Engineer, 1997

15-97 M. R. Barkhudarov, Advanced Simulation of the Flow and Heat Transfer Process in Simultaneous Engineering, Flow Science report, presented at the Casting 1997 – International ADI and Simulation Conference, Helsinki, Finland, May 28-30, 1997

14-97 M. Ranganathan and R. Shivpuri, Reducing Scrap and Increasing Die Life in Low Pressure Die Casting through Flow Simulation and Accelerated Testing, Dept. Welding and Systems Engineering, Ohio State University, Columbus, OH, presented at 19th International Die Casting Congress & Exposition, November 3-6, 1997

13-97 J. Koke, Modellierung und Simulation der Fließeigenschaften teilerstarrter Metallegierungen, Livt Information, Institut für Verfahrenstechnik, RWTH Aachen, October 1997

10-97 J. P. Greene and J. O. Wilkes, Numerical Analysis of Injection Molding of Glass Fiber Reinforced Thermoplastics – Part 2 Fiber Orientation, Body-in-White Center, General Motors Corp. and Dept. Chemical Engineering, University of Michigan, Polymer Engineering and Science, Vol. 37, No. 6, June 1997

9-97 J. P. Greene and J. O. Wilkes, Numerical Analysis of Injection Molding of Glass Fiber Reinforced Thermoplastics. Part 1 – Injection Pressures and Flow, Manufacturing Center, General Motors Corp. and Dept. Chemical Engineering, University of Michigan, Polymer Engineering and Science, Vol. 37, No. 3, March 1997

8-97 H. Grazzini and D. Nesa, Thermophysical Properties, Casting Simulation and Experiments for a Stainless Steel, AT Systemes (Renault) report, presented at the Solidification Processing ’97 Conference, July 7-10, 1997, Sheffield, U.K.

7-97 R. Van Tol, L. Katgerman and H. E. A. Van den Akker, Horizontal Mould Filling of a Thin Wall Aluminum Casting, Laboratory of Materials report, Delft University, presented at the Solidification Processing ’97 Conference, July 7-10, 1997, Sheffield, U.K.

6-97 M. R. Barkhudarov, Is Fluid Flow Important for Predicting Solidification, Flow Science report, presented at the Solidification Processing ’97 Conference, July 7-10, 1997, Sheffield, U.K.

22-96 Grun, Gerd-Ulrich & Schneider, Wolfgang, 3-D Modeling of the Start-up Phase of DC Casting of Sheet Ingots, Proc TMS Annual Meeting, 1996, pp. 971-981

9-96 M. R. Barkhudarov and C. W. Hirt, Thixotropic Flow Effects under Conditions of Strong Shear, Flow Science report FSI96-00-2, to be presented at the “Materials Week ’96” TMS Conference, Cincinnati, OH, 7-10 October 1996

4-96 C. W. Hirt, A Computational Model for the Lost Foam Process, Flow Science final report, February 1996 (FSI-96-57-R2)

3-96 M. R. Barkhudarov, C. L. Bronisz, C. W. Hirt, Three-Dimensional Thixotropic Flow Model, Flow Science report, FSI-96-00-1, published in the proceedings of (pp. 110- 114) and presented at the 4th International Conference on Semi-Solid Processing of Alloys and Composites, The University of Sheffield, 19-21 June 1996

1-96 M. R. Barkhudarov, J. Beech, K. Chang, and S. B. Chin, Numerical Simulation of Metal/Mould Interfacial Heat Transfer in Casting, Dept. Mech. & Process Engineering, Dept. Engineering Materials, University of Sheffield and Flow Science Inc, 9th Int. Symposium on Transport Phenomena in Thermal-Fluid Engineering, June 25-28, 1996, Singapore

11-95 Barkhudarov, M. R., Hirt, C.W., Casting Simulation Mold Filling and Solidification-Benchmark Calculations Using FLOW-3D, Modeling of Casting, Welding, and Advanced Solidification Processes VII, pp 935-946

10-95 Grun, Gerd-Ulrich, & Schneider, Wolfgang, Optimal Design of a Distribution Pan for Level Pour Casting, Proc TMS Annual Meeting, 1995, pp. 1061-1070

9-95 E. Masuda, I. Itoh, K. Haraguchi, Application of Mold Filling Simulation to Die Casting Processes, Honda Engineering Co., Ltd., Tochigi, Japan, presented at the Modelling of Casting, Welding and Advanced Solidification Processes VII, The Minerals, Metals & Materials Society, 1995

6-95 K. Venkatesan, Experimental and Numerical Investigation of the Effect of Process Parameters on the Erosive Wear of Die Casting Dies, presented for Ph.D. degree at Ohio State University, 1995

5-95 J. Righi, A. F. LaCamera, S. A. Jones, W. G. Truckner, T. N. Rouns, Integration of Experience and Simulation Based Understanding in the Die Design Process, Alcoa Technical Center, Alcoa Center, PA 15069, presented by the North American Die Casting Association, 1995

2-95 K. Venkatesan and R. Shivpuri, Numerical Simulation and Comparison with Water Modeling Studies of the Inertia Dominated Cavity Filling in Die Casting, NUMIFORM, 1995

1-95 K. Venkatesan and R. Shivpuri, Numerical Investigation of the Effect of Gate Velocity and Gate Size on the Quality of Die Casting Parts, NAMRC, 1995.

15-94 D. Liang, Y. Bayraktar, S. A. Moir, M. Barkhudarov, and H. Jones, Primary Silicon Segregation During Isothermal Holding of Hypereutectic AI-18.3%Si Alloy in the Freezing Range, Dept. of Engr. Materials, U. of Sheffield, Metals and Materials, February 1994

13-94 Deniece Korzekwa and Paul Dunn, A Combined Experimental and Modeling Approach to Uranium Casting, Materials Division, Los Alamos National Laboratory, presented at the Symposium on Liquid Metal Processing and Casting, El Dorado Hotel, Santa Fe, New Mexico, 1994

12-94 R. van Tol, H. E. A. van den Akker and L. Katgerman, CFD Study of the Mould Filling of a Horizontal Thin Wall Aluminum Casting, Delft University of Technology, Delft, The Netherlands, HTD-Vol. 284/AMD-Vol. 182, Transport Phenomena in Solidification, ASME 1994

11-94 M. R. Barkhudarov and K. A. Williams, Simulation of ‘Surface Turbulence’ Fluid Phenomena During the Mold Filling Phase of Gravity Castings, Flow Science Technical Note #41, November 1994 (FSI-94-TN41)

10-94 M. R. Barkhudarov and S. B. Chin, Stability of a Numerical Algorithm for Gas Bubble Modelling, University of Sheffield, Sheffield, U.K., International Journal for Numerical Methods in Fluids, Vol. 19, 415-437 (1994)

16-93 K. Venkatesan and R. Shivpuri, Numerical Simulation of Die Cavity Filling in Die Castings and an Evaluation of Process Parameters on Die Wear, Dept. of Industrial Systems Engineering, Presented by: N.A. Die Casting Association, Cleveland, Ohio, October 18-21, 1993

15-93 K. Venkatesen and R. Shivpuri, Numerical Modeling of Filling and Solidification for Improved Quality of Die Casting: A Literature Survey (Chapters II and III), Engineering Research Center for Net Shape Manufacturing, Report C-93-07, August 1993, Ohio State University

1-93 P-E Persson, Computer Simulation of the Solidification of a Hub Carrier for the Volvo 800 Series, AB Volvo Technological Development, Metals Laboratory, Technical Report No. LM 500014E, Jan. 1993

13-92 D. R. Korzekwa, M. A. K. Lewis, Experimentation and Simulation of Gravity Fed Lead Castings, in proceedings of a TMS Symposium on Concurrent Engineering Approach to Materials Processing, S. N. Dwivedi, A. J. Paul and F. R. Dax, eds., TMS-AIME Warrendale, p. 155 (1992)

12-92 M. A. K. Lewis, Near-Net-Shaiconpe Casting Simulation and Experimentation, MST 1992 Review, Los Alamos National Laboratory

2-92 M. R. Barkhudarov, H. You, J. Beech, S. B. Chin, D. H. Kirkwood, Validation and Development of FLOW-3D for Casting, School of Materials, University of Sheffield, Sheffield, UK, presented at the TMS/AIME Annual Meeting, San Diego, CA, March 3, 1992

1-92 D. R. Korzekwa and L. A. Jacobson, Los Alamos National Laboratory and C.W. Hirt, Flow Science Inc, Modeling Planar Flow Casting with FLOW-3D, presented at the TMS/AIME Annual Meeting, San Diego, CA, March 3, 1992

12-91 R. Shivpuri, M. Kuthirakulathu, and M. Mittal, Nonisothermal 3-D Finite Difference Simulation of Cavity Filling during the Die Casting Process, Dept. Industrial and Systems Engineering, Ohio State University, presented at the 1991 Winter Annual ASME Meeting, Atlanta, GA, Dec. 1-6, 1991

3-91 C. W. Hirt, FLOW-3D Study of the Importance of Fluid Momentum in Mold Filling, presented at the 18th Annual Automotive Materials Symposium, Michigan State University, Lansing, MI, May 1-2, 1991 (FSI-91-00-2)

11-90 N. Saluja, O.J. Ilegbusi, and J. Szekely, On the Calculation of the Electromagnetic Force Field in the Circular Stirring of Metallic Melts, accepted in J. Appl. Physics, 1990

10-90 N. Saluja, O. J. Ilegbusi, and J. Szekely, On the Calculation of the Electromagnetic Force Field in the Circular Stirring of Metallic Molds in Continuous Castings, presented at the 6th Iron and Steel Congress of the Iron and Steel Institute of Japan, Nagoya, Japan, October 1990

9-90 N. Saluja, O. J. Ilegbusi, and J. Szekely, Fluid Flow in Phenomena in the Electromagnetic Stirring of Continuous Casting Systems, Part I. The Behavior of a Cylindrically Shaped, Laboratory Scale Installation, accepted for publication in Steel Research, 1990

8-89 C. W. Hirt, Gravity-Fed Casting, Flow Science Technical Note #20, July 1989 (FSI-89-TN20)

6-89 E. W. M. Hansen and F. Syvertsen, Numerical Simulation of Flow Behaviour in Moldfilling for Casting Analysis, SINTEF-Foundation for Scientific and Industrial Research at the Norwegian Institute of Technology, Trondheim, Norway, Report No. STS20 A89001, June 1989

1-88 C. W. Hirt and R. P. Harper, Modeling Tests for Casting Processes, Flow Science report, Jan. 1988 (FSI-88-38-01)

2-87 C. W. Hirt, Addition of a Solidification/Melting Model to FLOW-3D, Flow Science report, April 1987 (FSI-87-33-1)

SPATTER IN LASER SPIRAL WELDING OF ZINC-COATED STEELS (아연 코팅 강철에서의 나선형 레이저 용접으로 인한 튐 현상)

튀는 문제에 대한 설명

  • 간격 없이 아연 코팅 강재에 레이저 용접을 하는동안 아연 코팅이 기화되는 표면 사이에선 기화와 축적이 됨
  • 배출시킬 경로가 없으면 아연 증기는 계속해서 녹은 강철 풀에 유입되어 튀는 현상이 발생할 수 있음
  • 게다가 아연 증기는 키홀의 움직임과 공정의 안정성에 영향을 미침
  • 순간적인 아연 증기압을 추정하고 키홀의 움직임을 분석하기 위해 FLOW-3D WELD에서 개발 된 시뮬레이션 모델
    – 튀는 현상이 발생한 부분에서 아연 증기압을 줄이고 적절한 키홀 개방을 유지하기 위해 용접 일정을 재설계

FLOW-3D WELD의 수치 모델

  • 실험 및 모델 설정
    (a) 레이저 스티칭 설정
    (b) FLOW-3D WELD 모델 설정
    (c) 레이저 나선형 용접 설정 및
    (d) 레이저 나선형 스캐닝 경로
  • 아연도 금강의 레이저 용접에서 발생하는 물리적 현상의 개략도

모델 검증


공정 동특성

  • 용융 및 키홀이 접합면을 교차할 때, 축적 된 고압의 아연 증기가 용융 표면 틈에 작용하여 벽의 키홀 압력을 넘어서 튀는 결과로 발생함

용접 계획 개선

  • 제안 된 계획
    (a) 시간에 따른 제안 된 라인 에너지
    (b) 임계 라인 에너지의 개략도
  • 원래 계획과 제안 된 계획의 용접부 비교
    – (a), (b), (c) 및 (d)는 표면 형태, 용접 표면의 용융 영역, 단면 및 원래 계획에서 시뮬레이션 된 단면이며 (e), (f), (g) 및 (h)는 제안 된 계획에 맞게 함.

결론

  • 접합면에서의 순간적인 높은 아연 압력은 용융의 변동을 낮추고 튀는 현상을 야기시킴
  • 접합면에서 계산 된 아연 증기압은 튀는 현상의 형성에 지표가 될 수 있으며 용접 계획 설계를 제안 할 수 있음
  • 나선형 용접의 초기 에너지는 레이저가 접합면을 관통 할 때 심각하게 튀는 현상을 초래하기에 아연 증기압의 증가를 피하기 위해 제한됨

Laser Keyhole Welding (레이저 키홀 용접)

진동이 없는 레이저 키홀 용접


진동이 없는 레이저 용접의 문제점

  • 틈새 조건에서 허용 오차가 낮아지는 좁은 조인트 폭
  • 레이저가 꺼질 때 끝의 큰 구멍
  • 속도가 높아 침투가 불충분 할 수 있음
  • 사용 가능한 레이저 출력으로부터 제한을 받음

진동이 있는 레이저 랩 용접

  • 키홀의 붕괴를 방지하는 고속 스캐닝이 가능
    – 다공성을 최소화함
  • 인터페이스 간극에서 브리지 간격을 조정하여 조인트 폭을 조정할 수 있는 유연성을 제공함

진동이 있는 레이저 용접의 장점

  • 성능 및 스타일링을 위한 제품을 개선
  • 최초의 품질에서 요구를 충족시키기위해 결함을 감소
  • 성능의 요구 사항을 충족시킬 수 있는 맞춤형 용접 형상

진동 용접 : 실험 결과


모델 검증


한 사이클 내의 키홀의 움직임

  • 진동이 없을 때 : 일관된 전도 또는 키홀 용접
  • 진동이 있을 때 : 전도 용접을 하며 경로 및 시간에 따라 한 번의 주기 내에서 얕은 키홀과 깊은 키홀이 용접 간 전환 가능

진동을 이용한 레이저 용접의 장점

  • 진동을 이용한 최초 품질이 향상됨
  • 키홀로 인한 다공성을 피하면서 빠른 용접 속도를 가능하게 함
  • 전력 변조가 사용되지 않는 경우에 각 주기 내에서 키홀과 전도 모델 간의 전환이 가능
  • 진동의 매개 변수를 변경하여 중요한 용접의 너겟 치수 및 강도의 조정이 가능
  • 시트 간의 틈 브리징을 개선

Fluid dynamics modelling for additive manufacturing

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AM프로세스에 CFD를 사용해야하는 이유

  • AM의 용융 풀(Melt pool) 분해능(0.01 – 0.001mm 길이 스케일)에서 유체 흐름을 정확하게 표현
    – 파우더 페드 퍼짐(Powder bed spreading) : DEM(Discrete Element Method)을 통해 파우더 베드 압축 및 흡수 특성을 예측하는데 도움
    – 선택적 레이저 용해 : 결함 설계 공간 및 용융 풀(Melt pooe) 형상 매핑 및 예측
    – 빠른 응고(Solidification) : 구성 분리 및 위상 핵(Phase nucleation) 형성 및 예측

파우더 증착 및 레이저 용융(Powder deposition and laser melting)

  • 모델 입력 : 파우더 크기 분포, 합금 재료 특성 및 레이저 공정 매개 변수
  • 모델 출력 : 가열/냉각 프로파일, 결함 밀도, 조성 변화

연속 및 펄스 레이저 용융

  • Takeaway : 두 매개 변수 세트 모두 고밀도 재료를 생산하지만 열 이력(History)은 상당히 다름

모델 정확도 및 검증

NiTi, Ti64 및 316L에서 수행된 모델 검증

용융 풀(Melt pool) 형태 및 키홀링(Keyholing)

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Spatter in laser spiral welding of zinc-coated steels/아연 코팅된 강철의 레이저 스파이럴 용접 패턴

Problem description

  • 간격이없는 Zn 코팅 강재의 레이저 용접 동안 Zn 코팅은 기화 표면 사이에서 기화 및 축적
  • 배출 채널이 없으면 Zn 증기가 계속해서 녹은 강철 풀(Pool)에 유입되어 스패터(Spatter)가 발생
  • Zn 증기는 또한 키홀(Keyhole) 역학 및 공정 안정성에 영향을 미침
  • 순간 Zn 증기압을 추정하고 키홀(Keyhole) 역학을 분석하기 위해 FLOW-3D WELD에서 개발된 시뮬레이션 모델
  • 스패터(Spatter)가 발생한 지역에서 Zn 증기압을 줄이고 적절한 키홀(Keyhole) 개방을 유지하기 위해 용접 일정을 재설계

FLOW-3D WELD 수치적 모델

모델 검증

프로세스 역학(Process dynamics)

용접 일정(Welding schedule)의 향상

결론

  • Paying 인터페이스에서의 높은 순간 Zn압력은 풀(Pool) 변동 및 스패터(Spatter) 형성으로 이어짐
  • Paying 인터페이스에서 계산된 Zn증기압은 스패터(Spatter) 형성의 지표가 될 수 있으며 용접 일정(Welding schedule) 설계를 안내 할 수 있음
  • 나선형 용접의 초기 라인 에너지는 레이저가 Paying 인터페이스를 관통할 때, 심각한 스패터(Spatter)를 초래하는 Zn증기압의 증가를 피하기 위해 제한

What’s happening at the melt pool?/레이저 가공

Laser keyhole welding

레이저 키홀(Keyhole) 가공(No oscillations/진동 고려하지 않을 경우)

높은 속도에서 다공성을 감소시키는 경우(Reduced porosity at high speed-mechanism)

고속 레이저 가공(진동 고려하지 않음)해석 시 고려사항

  • 틈새 조건에 대한 허용 오차가 낮아지는 좁은 조인트(Joint) 너비
  • 레이저가 꺼질 때 큰 끝 분화구(Large end crater)
  • 속도가 높을 때 불충분한 침투(Penetration)
  • 제한된 사용가능한 레이저 출력 : 6kW

진동을 고려한 레이저 랩(Lap) 용접

  • 키홀(Keyhole) 붕괴를 방지하는 고속 스캐닝 가능
    – 다공성(Porosity) 최소화
  • 인터페이스 간극(Interface gaps)에서 브리지 간격(Bridge gaps)을 조정하여 조인트(Joint) 폭을 조정할 수 있는 유연성 제공

진동을 고려한 레이저 용접 : 실험 결과와 비교

모델 검증

사이클(One cycle) 내에서 키홀(Keyhole) 역학

  • 진동을 고려하지 않을 경우 : 일관된 전도 또는 키홀 용접
  • 진동을 고려할 경우 : 경로와 일정에 따라 한 번의 주기내에서 전도 용접, 얕은 키홀(Keyhole)과 깊은 키홀(Keyhole) 용접 간 전환 가능

진동을 고려한 레이저 가공의 이점

  • 진동을 통한 최초 품질 향상
  • 키홀(Keyhole)로 인한 다공성(Porosity)을 피하면서 높은 용접 속도 가능
  • 전력 변조가 사용되지 않는 경우, 각 주기내에서 키홀(Keyhole) 및 전도 모델간 전환
  • 진동 매개 변수 변경을 통해 중요 용접 너겟(Nugget) 치수 및 강도 조정 가능
  • 시트 간 틈 브리징(Gap gridging) 개선

Laser Welding and Additive Manufacturing

Application

  • Shallow penetration weld (Shallow 침투 용접)
  • Deep penetration weld (Deep 침투 용접)
  • Laser-arc hybrid welding(레이저-아크 하이브리드 용접)
  • Laser repair technology
  • Laser cladding(레이저 클레딩)
  • Laser powder bed fusion process

관련 물리 모델

  • Viscous Flows and Turbulence(점성 유체 및 난류 모델)
  • Surface Tension(표면장력)
  • General Moving Objects(GMO)
  • Heat Transfer(열전달)
  • Visco-elasto-plasticity(점탄성)
  • Solidification(응고)
  • Thermal Stresses(열응력)

Laser/Heat source(레이저/열원)

  • 레이저 출력 및 용접 속도 향상
    – 더 큰 키홀(Keyhole) 개방 및 깊이 변동이 적음
    – 후면 용융 풀 (Moltan Pool)의 난기류가 최소화된 키홀(Keyhole) 앞부분 벽(Wall)에 레이저 빔(Laser beam)이 노출
    – 다공성 형성(Porosity formation) 최소화

Laser beam motion(레이저 빔 모션)

  • 레이저 빔(Laser beam) 기울기 증가
    – 큰 각도에서 유사한 방향을 따라 작용하는 중력 및 반동 압력으로 인해 후면 용융 풀(Moltan pool)에서 층류(Laminar flow)가 관찰
    – 다공성 발생(Porosity occurrence) 최소화

해석 사례

  • Laser metal deposition(레이저 금속 증착) -Single layer
  • 40마이크론 유체 입자 주입 (500,000/sec)
  • 레이저 출력 : 100W
  • 스캔속도 : 1cm/sec
  • 레이저 빔 직경 : 2mm
  • 재질 : IN-718 meterail alloy
  • Laser metal deposition(레이저 금속 증착) – Multilayer
  • Laser powder bed fusion process
  • FLOW-3D DEM 및 FLOW-3D WELD 고려
    – 용융 영역(Melt region)
    – 용융 풀(Melt pool)의 속도 및 온도
    – 고체 영역(Solid fraction)
  • 레이저 방사(Laser irradiation) 조건
    – 출력 : 200W
    – 스캔속도 : 3m/s
    – Spot radius : 0.1mm

Particle Model(입자모델)

Lagrangian particle model(라그랑지안 입자 모델)

라그랑지안 입자 모델(Lagrangian particle model)은 서브 그리드(Sub-grid) 모델로 계산 셀보다 작은 속성과 크기가 다른 구형(Spherical) 입자의 움직임을 추적할 수 있는 계산 모델입니다.

해석 사례

  • Aeration tank modelling(산기 탱크 모델링)
  • Bubble diffuser system(버블디퓨저 시스템)
  • Drug delivery etc.

Particle options

  • Marker particles – Massless
  • Mass particles – Solid spheres
  • Fluid particles – Droplets of fluid
  • Gas particles – Bubbles of gas

가정 및 한계(Assumptions & Limitations)

  • 입자크기(Particle size) << 격자크기(Mesh size)
  • 입자간의 상호작용을 고려하지 않습니다.
  • 입자 갯수에 제한

Marker Particles(마커 입자)

마커 입자(Marker particles)는 흐름(Flow)에 영향을 미치지 않고 주변 유체의 속도에 따라 움직이지 않는 질량이 없는 상태의 입자입니다. 그러므로, 유체 분자의 시각화로 간주될 수 있습니다.

계산영역에 마커 입자(Marker particles)를 적용함으로써, 개별 유체 분자가 따르는 경로(Paths)를 시각화할 수 있습니다.

Mass Particles(질량 입자)

질량 입자(Mass particles)는 특정 직경과 밀도를 가진 고체 구체(Spheres)로 고려됩니다. 따라서, 질량 입자(Mass particles)는 계산 영역에서 현탁된 고체(Suspended solids)의 운동을 모델링하기 위해 사용됩니다.

Fluid particles(유체 입자)

유체 입자(Fluid particles)는 유체#1의 액적(Droplets of Fluid#1)으로 생각할 수 있습니다. 유체 입자(Fluid particles)는 유체 스프레이(Fluid sprays), 적층 제조(additive manufacturing), 용접(Welding) 등과 같은 계산 셀보다 작은 모델링 유체 부피를 포함하는 수많은 시뮬레이션에 사용될 수 있습니다.

Gas particles(가스 입자)

가스 입자(Gas particles)는 가스의 구형(Spherical) 버블과 유체, 공극(Void) 및 고체 물체와의 상호 작용을 시뮬레이션하는데 사용됩니다.