Numerical Simulation Of Welding Field And Deformation Of Thin-plate Welded Joints Induced By Laser-arc Hybrid Welding Process

It is essential to investigate vehicles weight reduction due to demand of energy conservation and emission reduction with the rapid development of automotive industry.Generally,there are many approaches to reduce the weight of a car,such as optimization of body structure,application of light alloy materials,and development of new welding method.Particularly,welding is one of the most important methods for connecting automotive parts,and therefore,the development of innovative welding process becomes more critical.Traditionally,the electrical arc welding could induce large distortion when connecting thin plates,which can increase the consumption of capital and time to correct the induced large deformation.Laser welding requires higher quality of joints processing as well as higher cost of welding process due to low energy utilization,although it can avoid the large deformation successfully.However,laser arc hybrid welding can achieve a synergistic effect of "1+1>2",not only improving the energy efficiency of laser welding,but also reducing the welding distortion and processing requirements for joints.Based on the general finite element software ABAQUS,this paper developed a thermal-elastic-plastic finite element method to simulate the laser arc hybrid welding process by computing the temperature field,deformation field and stress field produced by welding,with taking both material nonlinearity and geometric nonlinearity into consideration.A laser arc hybrid welding robot was employed to perform the process test.The effectiveness of the developed numerical simulation method was verified by comparing the simulated results with the experimental data.Besides,the effects of process parameters such as laser power,arc power,filament pitch,and welding speed on the welding temperature field and deformation field were discussed.The optimal process parameters were applied in the later comparison test.Moreover,quantitative comparison of the distribution patterns of temperature field,deformation field and stress field generated by laser welding,arc welding and laser arc hybrid welding was also conducted.The distribution of the deformation field produced by laser arc welding is similar to that of laser welding,while the amount of deformation is much smaller than that of arc welding.The welding deformation of the welding test pieces obtained from the test was measured using a three-coordinate measuring machine and it's consistent with the calculated results,which further verified the validity of the calculation method.Finally,using the developed calculation method,the temperature field and deformation field of laser arc hybrid welding and arc welding of T-joints were compared.The research results show that the developed nonlinear finite element approach can effectively simulate the temperature field and deformation field of low carbon steel sheet during laser arc hybrid welding.Influence on temperature field and deformation field of the welding process parameters are as follows: The filament spacing has a great effect on the temperature field and deformation field.If the filament spacing lies in a certain range,the temperature and deformation change little.Otherwise,the out-of-plane deformation mode can change from convex to concave deformation.The arc power and laser power affects the melting width of the bath and the bath penetration respectively.A stable temperature field and deformation field can be obtained by accelerating welding speed,which indicates that laser-arc hybrid welding can achieve a high speed.Furthermore,the temperature field,deformation field and stress field of laser welding,MIG arc welding and laser-MIG hybrid welding were compared using the large deformation theory.Compared with MIG welding,the laser-MIG hybrid welding can significantly reduce the welding distortion though the out-of-plane deformation mode of laser-MIG hybrid welding is the same as laser welding.The maximum stress value obtained by laser arc welding is lower than the yield stress of low carbon steel sheet,while the maximum stress value obtained by laser welding and MIG welding is higher than its yield stress.Hence,it is proved that laser arc hybrid welding combines the advantages and avoids the shortcomings of both laser and arc welding methods,so that it can effectively reduce the distortion with a moderate heat input.In this paper,the welding temperature field and deformation field of the T-joint are simulated by the developed finite element method.The calculation results are verified by experimental data obtained from proper tests.The finite element methodology developed in this paper is significant for the promotion and application of laser arc hybrid welding in engineering.