Numerical Simulation Of Laser Welding Of Stainless Steel Carriage

Laser welding as a new welding process,because of its small welding deformation,green,efficient and other advantages,is widely used in railway vehicles.Side wall is a large structure with high requirements for flatness in stainless steel carriage components.As the indentation problem of traditional spot welding process,laser welding has been gradually used to replace spot welding in the production of stainless steel carriage side wall in recent years.Although laser welding has certain advantages over traditional spot welding in deformation control,laser welding has high thermal cycle rate and more intense melting and solidification process,which inevitably cause stress after welding deformation,the influence on the performance of the side wall of the geometric and mechanical properties.How to further optimize the welding process so as to control the welding deformation effectively has become a key consideration in the research and development of the railway vehicle body.Based on welding numerical simulation technology,this paper studies the welding deformation law of stainless steel bus side wall by laser welding and the welding process optimization scheme for deformation control,so as to provide theoretical and technical support for the welding deformation control of a certain type of stainless steel railway vehicle body side wall by laser welding.The main contents are as follows:(1)Establish the local and global finite element models of SUS301 L austenitic stainless steel carriage side wall laser welding.The finite element analysis is carried out using the moving heat source method based on three-dimensional thermo-elasto-plasticity on the local model,and the influence of the shape parameters of Gaussian surface + cylindrical composite heat source on the shape of molten pool is studied.Finally,the heat source is checked.Compared with the test,the errors of the simulated surface fusion width,intermediate fusion width and penetration depth are 6.10%,6.67% and 2.17% respectively.The simulation results show that the heat source can be used in laser welding.(2)Aiming at the problems of large amount of nonlinear calculation and long solution time in welding simulation,two different coarse and fine mesh models are established,and nine schemes are designed in combination with the number of segments of different thermal cycle curve methods to study the accuracy and efficiency of thermal cycle method.The comparison of nine schemes shows that the thermal cycle curve method can greatly improve the efficiency of welding simulation under the condition of ensuring the calculation accuracy.(3)Based on the thermal cycle curve method,the models of exterior wall panel and 8 small beams are established,and eight different welding sequence schemes(4 single welding gun schemes + 4 multi welding gun schemes)are designed.On the basis of ensuring the calculation accuracy,the thermal elastic-plastic finite element analysis of small beams is completed efficiently.Results show that by optimizing welding sequence can effectively reduce welding deformation of the structure,welding torch and work with more reasonable welding sequence can effectively control the deformation within 1 mm of the cladding.(4)Under the optimal welding sequence of the small beam,the welding simulation of the upper beam and the lower beam of the window of the side wall is carried out,and the maximum deformation of the side wall is finally predicted to be 1.26 mm,mainly for the vertical deformation along the thickness direction.