Simulation Of Deformation And Optimization Of Welding Sequence In The Multi-pass Welding Of Aluminum Alloy Truck Side-Walls

Welding is a crucial manufacturing process and widely used in industries to assemble various products including ships, hoisting machineries and trains. However, welding residual distortion often results in problems such as the beauty of the structure appearance and the reliability of product use during the assembly and increased fabrication costs. Therefore, prediction and reduction of welding distortion are critical to improve the quality of welded structures. In this study, the multi-pass butt welding joints of side walls of aluminum alloy wagons were simulated by adopting the average thermal cycling curves with SYSWELD simulation software. And the average thermal cycling curve is based on thermal elastic-plastic finite element method and double-ellipsoid heat source. In the simulation the full effect of thermo physical properties of materials on the microstructure changes were took into account. Meanwhile, comprehensive considering the problems of efficiency and deformation control, we designed four different welding sequences during the multi-pass welding docking, through the deformation analysis, we determined a more reasonable welding sequence that would be a useful reference for side walls of aluminum alloy wagons welding technology.Research work of this dissertation mainly includes:Firstly, a method of solid-shell elements combining modeling is put forward in this paper. Which means using three-dimensional solid elements in the near-weld zone, while away from the welding seam areas, we used shell elements to reduce the scale of the grid model, this can further increase the computing efficiency. Meanwhile, instead of rigid unit model that connect entities and shell elements, shell element node fusion method was introduced, which avoided the difficulty in solving process.Secondly, according to the characteristic of multi-pass butt welding joints of side walls of aluminum alloy wagons, the multi-pass butt welding process of side walls of aluminum alloy wagons is simulated by adopting the average thermal cycling curve as transient heat source based on thermal elastic-plastic finite element method.Finally, by comparing the deformation simulation results of aluminum truck sidewall under different welding sequence, following several welding deformation prediction and control law, different welding sequences have a certain impact on the transverse and longitudinal shrinkage deformation, but changing the welding sequence has a limited effort; increase the Z-direction constraint can significantly reduce the amount of deflection; for multi-pass welding, first welding the first layer by a welding sequence uniform, and then welding the second layer by the same welding sequence uniform,can have a small deformation.