The Numerical Simulation Of Welding Deformation For Body Bolster On Subway Underframe

In recent years, with the high-speed urbanization of China, enlargement of city scale and explosion of population makes traffic problem stands out in big cities. In order to solve this problem, many cities began to construct the urban rail transit. In rail transit equipment manufacturing industry, both bogie and vehicle are welding structure, the welding residual stress and deformation of which affects the manufacturing quality and vehicle running security.The research object of this paper is the body bolster of a new subway body bolster designed by CRRC Qingdao sifang rolling stock co LTD. Against the difficulty of huge structure and numerous weld seams, this paper employed the SYSWELD software developed by ESI group in France to simulate the process of welding deformation of this structure based on the thermal elastic-plastic theory and the method of inherent strain. The main content of this paper is as follows:1. First, this paper established the double ellipsoid plus 3Dgaussian composite heat source model for laser-arc hybrid welding method used in body bolster and verified the rationality of the model by heat source check.2. Second, Using the verified heat source model to calculate the stress and train field of all local joint models of the whole body bolster in order to get the inherent strain values, then load the values as inherent strain on structure to simulate the whole welding deformation process of body bolster. The result showed that the body bolster structure showed mainly the waves deformation. The X-direction shrinkage distortion and the angular distortion at the cover plate edge area is obvious, the deformation respectively reaches 2.84mm and 2.59mm; The Y-direction shrinkage distortion, the X-direction bending deflection and the angular distortion at the cover plate middle area is less obvious, the deformation respectively reaches 0.51mm,0.16mm and 0.85mm.3. At last, according to the characteristic of the body bolster structure and weld distribution, this paper set the other two kinds of different welding sequence and welding direction. The welding deformation of all pre-set solutions was simulated. The result showed that the welding sequence mostly affect X-direction bending deflection, the percentage rate of variation reached 6.67%.The effects of different welding sequence to welding deformation is not significant; the welding direction mostly affect X-direction bending deflection, the percentage rate of variation reached 166.58%.By optimizing the welding direction can effectively decrease welding deformation of structure.