| Aluminum alloys are more and more widely used in body frames because of the ir excellent comprehensive mechanical properties and corrosion resistance.Some automobile manufacturers have used aluminum alloy as the material of the bottom car body to replace the traditional steel structure,but there are many problems in the actual production of the bottom car body of aluminum alloy,such as large amount of welding deformation,assembly difficulties,etc.This is because of the large thermal expansion coefficient of aluminum alloy,which is easy to produce large welding defects.Based on the above problems,this paper takes the aluminum alloy bottom car body of a new energy vehicle as the research object,forecasts the welding deformation and distribution by means of the combination of numerical simulation and test verification,and puts forward the optimization scheme to improve the traditional welding process.The car body model used in this paper used 6 series aluminum alloy as the main material of the structural frame and 5 series aluminum alloy as the auxiliary material.According to the structural characteristics of the model,the joints were selected to test the microstructure and mechanical properties.Secondly,the simulation analysis model of dissimilar aluminum alloy lap welding was established by using the finite element analysis software simufact welding,and the heat source model was verified.The simulation analysis results were compared with the test results to determine the rationality of welding temperature field,thermal cycle curve and deformation.Then,based on the accurate model parameters of welding heat source,welding current,voltage,speed and other welding parameters,the simulation numerical analysis model of the welding of the middle frame of the bottom car body was established,the results of welding temperature field and strain field were analyzed,and the simulation deformation was compared with the welding deformation of the trial production sample car to determine whether the numerical value of the simulation deformation met the accuracy requirements.Finally,the parts with large welding deformation were analyzed,and the welding model was optimized by adjusting the welding sequence and the location of the clamping points,and the multi group weldin g numerical analysis model was restablished to calculate and analyze the results,and the optimal welding sequence optimization scheme and welding constraint optimization scheme were obtained.The results showed that the welding performance of different aluminum alloy lap joint was good.The temperature curve of the simulation analysis of the lap joint plate was consistent with the temperature curve of the welding test,and the maximum relative error of the deformation was 13.3%.The deformation value of the bottom car body simulation analysis was close to the actual welding deformation value,and t he relative error was within 13%.Through the welding constraint optimization scheme,the deformation of the measurement point of the lower body was reduced by 8.2% ? 85.1%compared with the original scheme,and by the welding sequence optimization scheme,the deformation was reduced by 12.8% ? 77.8% compared with the constraint scheme II.In this paper,through the numerical simulation analysis of the bottom car body,the numerical value and distribution of the welding deformation were determined,which were basically consistent with the actual welding results,and the optimal welding constraints and welding sequence optimization scheme were obtained,so that the deviation of the structural parts after welding can meet t he actual requirements of the project.The optimization scheme greatly reduces the deformation trend and distribution of the bottom car body structure,improves the assembly accuracy of the body structure and the production efficiency of the whole vehicle to a certain extent,and provides valuable experience for the production of subsequent models. |
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