Optimization Of Spot Welding Sequence For Passenger Car Side Girth

The side girds of passenger vehicles are welded by several plates that meet the expected strength requirements.The automation and intelligence of body manufacturing has always been recognized as the key technology in the industry.Due to the complexity of the side girth structure,the joint of the outer plate of the body in white is particularly strict to the precision of spot welding after the stamping and forming.A large number of welding practices show that different welding sequences in the process of spot welding will inevitably lead to different degrees of residual deformation.In the process of spot welding of multiple plates such as side assembly,welding sequence has a particularly obvious influence on the consistency of welding quality and geometric accuracy.In order to minimize the influence of welding sequence on the precision of welded parts,the thermal deformation and thermal stress models in spot welding process were established based on the analysis of spot welding process around the side of passenger car based on heat transfer.The numerical method was used to solve the models,and the temperature field,stress field and strain field of each welding spot were obtained.Finally,the welding sequence optimization model is established and solved.The main contents and innovations are as follows:(1)Analysis of side spot welding process.Combined with the characteristics of the side girth structure,the influences of welding methods,welding fixtures and positioning datum selection of the component assembly to be welded on the welding quality were analyzed.On this basis,the precise welding classification of each component of the side girth assembly was carried out.(2)Obtain the optimal welding sequence.Based on the Fourier heat transfer formula,the unsteady temperature field model and welding deformation model of spot welding process were established.The APDL command flow method was used to solve the stress-strain field of welded parts according to different welding sequences.Taking the absolute value of the difference between the maximum and minimum stress variables of each solder joint and the product of the attribute constants of the welds as the objective function,the welding sequence model of the spot welding around the passenger car was established.The stress-strain field data of the welds obtained based on the APDL command flow was imported into the Mathmatical modeling software program,and the optimization model was solved based on the locust algorithm.(3)Verification of optimal welding sequence solution results based on APDL.Based on APDL method,the dynamic relationship between the temperature field,stress and strain field of welded parts and the coordinate of solder joint was established.On this basis,for different welding sequences,the maximum shape variable was extracted from the APDL operating data,and compared with the maximum shape variable of the optimal welding sequence obtained by the locust optimization algorithm,to verify the effectiveness of the locust optimization algorithm in solving the optimization model.(4)Experimental verification.According to the optimal welding sequence,the post-welding deformation data of each welding spot of the side circumference parts welded in the field were measured by the coordinate measuring instrument,and compared with the solution data based on locust optimization algorithm and the simulation data based on APDL.The results show that the optimization model and optimization results of the spot welding sequence of passenger car side circumference are consistent with the engineering practice.