Abstract:Most of the researches published on the numerical modeling of laser welding are looking at similar welding, mainly due to the difficulty of simulating the mixing phenomenon that occurs in dissimilar welding. Furthermore, numerical modeling of dissimilar laser welding of titanium and nickel alloys has been rarely reported in the literature. In this study, a 3D finite volume numerical model is proposed to simulate fluid flow, heat, and mass transfer for similar and dissimilar laser welding of Ti-6Al-4V and Incon… Show more
“…Literature [11] obtained the visual information of the weld surface through a self‐built binocular stereo vision system, analysed and processed the visual information to extract the edge contour of the weld formation, explored the image information representation method of multiple formation parameters of the weld, and finally proposed A new method for judging weld formation based on binocular stereo vision. Literature [12] uses a three‐light path vision sensor system to simultaneously collect images of the molten pool directly in front, diagonally behind, and diagonally below the welding pool, and project the three images onto the same image. The characteristic parameters related to the pool information are finally used for real‐time control of the welding process.…”
In order to explore the mapping recognition of arc welding molten pool characterisation and penetration state, according to the idea of embedded system construction, this article adopts the idea of software and hardware co-design to find the zero-crossing point of the second derivative in welding image edge detection, and give a threshold. When the absolute value of the first-order derivative exceeds the threshold and has a different sign with the first-order derivative of the previous edge, it is judged as a valid edge. The welding current adopts a symmetrical pulsed AC square wave, and the proportion of heat flow input is high. At the base current, the arc light is darker, so a clear image is obtained. This article designs a simulation experiment to verify the effect of the embedded system in this article. From the experimental research, it can be known that the embedded system constructed in this article can play a certain role in the mapping recognition of the arc welding molten pool characterisation and penetration state.
“…Literature [11] obtained the visual information of the weld surface through a self‐built binocular stereo vision system, analysed and processed the visual information to extract the edge contour of the weld formation, explored the image information representation method of multiple formation parameters of the weld, and finally proposed A new method for judging weld formation based on binocular stereo vision. Literature [12] uses a three‐light path vision sensor system to simultaneously collect images of the molten pool directly in front, diagonally behind, and diagonally below the welding pool, and project the three images onto the same image. The characteristic parameters related to the pool information are finally used for real‐time control of the welding process.…”
In order to explore the mapping recognition of arc welding molten pool characterisation and penetration state, according to the idea of embedded system construction, this article adopts the idea of software and hardware co-design to find the zero-crossing point of the second derivative in welding image edge detection, and give a threshold. When the absolute value of the first-order derivative exceeds the threshold and has a different sign with the first-order derivative of the previous edge, it is judged as a valid edge. The welding current adopts a symmetrical pulsed AC square wave, and the proportion of heat flow input is high. At the base current, the arc light is darker, so a clear image is obtained. This article designs a simulation experiment to verify the effect of the embedded system in this article. From the experimental research, it can be known that the embedded system constructed in this article can play a certain role in the mapping recognition of the arc welding molten pool characterisation and penetration state.
“…A three-dimensional Cartesian coordinate system is established with the heat source moving along the x -axis as shown in Figure 1(a) and the sinusoidal oscillation in the x – y plane. The following assumptions were made: ( i ) No gap between the plates is considered; ( ii ) Boussinesq's approximation [17] is used to account for change of density due to temperature variations; ( iii ) The weld pool surface is considered flat; ( iv ) The absorption coefficient of the laser by the workpiece is kept constant as 0.60 [18]. Figure 1 (a) Schematic illustration of geometry and finite element mesh distribution used for the simulations, (b) Weld experiment setup.…”
This study investigated the effect of beam oscillation on the solidification behaviour during laser welding of Al-5754 to Al-6061 alloy. In this study, a finite element model has been developed to simulate temperature and fluid flow fields by implementing different combinations of volumetric heat source models. Solidification parameters such as temperature gradient (G), solidification rate (R), cooling rate (G × R) and G/R are evaluated to understand the mechanism of microstructure formation. It was found that beam oscillation improves the tensile strength by 21.4% for full penetration welding due to an increase in the percentage of formation of equiaxed grains. Modelling results revealed that the cooling rate increases with an increase in oscillation frequency. However, tensile strength followed a parabolic distribution with a peak at the oscillation frequency of 300 Hz.
“…More comprehensive coupled fluid–thermal or fluid–thermal–mechanical models were used to analyze the processes of laser welding of aluminum alloys [ 72 , 73 ], titanium alloys [ 74 ], steels [ 75 , 76 , 77 , 78 ] or various dissimilar joints, especially a combination of different steel grades [ 79 , 80 ] or Al, Mg, Ti, Cu and Fe alloys [ 81 , 82 , 83 , 84 , 85 , 86 , 87 , 88 ].…”
The formation of dissimilar weld joints, including Al/Ti joints, is an area of research supported by the need for weight reduction and corrosion resistance in automotive, aircraft, aeronautic, and other industries. Depending on the cooling rates and chemical composition, rapid solidification of Al/Ti alloys during laser welding can lead to the development of different metastable phases and the formation of brittle intermetallic compounds (IMCs). The effort to successfully join aluminum to titanium alloys is associated with demands to minimize the thickness of brittle IMC zones by selecting appropriate welding parameters or applying suitable filler materials. The paper is focused on the numerical simulation of the laser welding–brazing of 2.0 mm thick titanium Grade 2 and EN AW5083 aluminum alloy plates using 5087 aluminum filler wire. The developed simulation model was used to study the impact of laser welding–brazing parameters (laser power, welding speed, and laser beam offset) on the transient temperature fields and weld-pool characteristics. The results of numerical simulations were compared with temperatures measured during the laser welding–brazing of Al/Ti plates using a TruDisk 4002 disk laser, and macrostructural and microstructural analyses, and weld tensile strength measurements, were conducted. The ultimate tensile strength (UTS) of welded–brazed joints increases with an increase in the laser beam offset to the Al side and with an increase in welding speed. The highest UTS values at the level of 220 MPa and 245 MPa were measured for joints produced at a laser power of 1.8 kW along with a welding speed of 30 mm·s−1 and a laser beam offset of 300 μm and 460 μm, respectively. When increasing the laser power to 2 kW, the UTS decreased. The results exhibited that the tensile strength of Al/Ti welded–brazed joints was dependent, regardless of the welding parameters, on the amount of melted Ti Grade 2, which, during rapid solidification, determines the thickness and morphology of the IMC layer. A simple formula was proposed to predict the tensile strength of welded–brazed joints using the computed cross-sectional Ti weld metal area.
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