Lightweight Design Of Aluminum Alloy Welding Bracket Structure For A Vehicle And Research On Influence Of Welding Seam

For automotive structural design,lightweight structure,lightweight material,and lightweight process are three important ways to achieve automotive lightweight.As a lightweight material with low density,high strength ratio and corrosion resistance,aluminum alloy is more and more favored by the automotive industry.However,the material properties of aluminum alloy itself determine that its welding form is different from steel,and the optimization design method of aluminum alloy welding structure should also be different.Based on the above considerations,this paper took the welding structure of aluminum alloy bracket of LNG gas cylinder as the research object,carried out the integrated multi-objective optimization based on topology optimization and implicit parametric model,and then studied the influence of overlap MIG welding seam on the welding structure optimization design of bracket,the specific contents are as follows:Firstly,according to the relevant national standards,the welding structure of the aluminum alloy support of the initial LNG cylinder was simulated and calculated,and the performance gap between the initial structure and the target value was obtained.Based on the initial structure,this article used the weighted flexibility method to optimize the design space twice with the minimum weighted strain energy as the design objective.The welding structure of aluminum alloy support was improved according to the final topological optimization results.The simulation results showed that the performance of the support had been improved,but some of the performances still didn’t meet the target value requirements.Secondly,an implicit parametric model of the welding structure of the aluminum alloy bracket with topology optimization was established,in which the welding structure was replaced by common node and rigid element connection.29 parameters were selected from the three parameters of thickness,location and cross-section shape.After considering the contribution and main effect of each parameter to each performance response,16 parameters were selected as the design variables for subsequent multi-objective optimization.The radial basis function neural network approximation model between design variables and performance response was established,and the multi-objective optimization of aluminum alloy bracket welding structure was carried out by using the approximation model.The multi-objective optimization results showed that the overall quality of the stent decreased by 17.94% on the premise of ensuring the performance of the stent to meet the target value.It showed that the automatic optimization process based on parametric model and radial basis function neural network approximation model was suitable for the design and optimization of aluminum alloy bracket welding structure.Finally,based on the multi-objective optimization of aluminum alloy bracket welding structure,the influence of overlapping MIG welding seam on bracket structure optimization design was fully considered.The mechanical properties and the real stressstrain curve of lap MIG weld were obtained by welding and tensile test,which were used to establish the shell element model of lap MIG weld.After substituting the shell element model of lap weld into the topology optimization of aluminum alloy bracket welding structure,we took the base weld and saddle weld at the bottom of the bracket as new design variables,and added 16 previously selected variables,a total of 18 design variables were selected to carry out the multi-objective optimization of bracket welding structure considering the influence of weld.The results showed that: after the multi-objective optimization considering the influence of welding seam,the overall quality of the support was greatly reduced,and the performance was greatly improved compared with the structure before the optimization,reaching the target value requirements.In addition,the stress distribution of the lap weld of the aluminum alloy bracket welding structure was more reasonable,and the maximum stress in the weld area was less than the allowable stress.It showed that after the lightweight design of the aluminum alloy bracket was carried out considering the considering the influence of weld,it can not only achieve the purpose of structural lightweight design,but also optimize the distribution of welding seam,which provides optimization ideas for lightweight design of aluminum alloy welding structure.