Effect Of Warping Defects Of Steel Plate Resistance Spot Welding On Average Stress Intensity Factor

With the rise of new technologies such as the internet,artificial intelligence and electrification,electric smart made cars and new energy vehicles are gradually becoming the future new definition,but quality is still under the new trends in the automobile industry is a very seriously problem,the car quality problem still hindering our country automobile industry development,Improving fatigue durability of the car is still one of the important measures to improve the quality of China's automobile.A typical car body-in-white structure usually contains 3,000 to 5,000 solder joints.Under the dynamic random load of a car body,it is easy to cause stress concentration around the solder joints,which causes fatigue damage,and a large part of the fatigue damage of the solder joints causes the car body.The fatigue of the structure leads to the reduction of various functional indicators of the car,which endangers the durability and safety of the car.During the welding process of the car body,various factors lead to the occurrence of solder joint defects,such as false welding,overburning and desoldering.These defects will reduce the fatigue life of the solder joint.In addition,during the welding process of the car body,uncontrollable factors such as sheet metal shape size and installation error make sheet metal welding easily cause warping defects,which significantly affects the welding quality and fatigue life.The main research work of this paper is as follows:Firstly,through the finite element simulation of resistance spot welding process,the simulation model of qualified solder joint and warpage defect solder joint was obtained.And then,the simulation model was processed by the pre-processing software,and the solder joint model was modularized.Among them,the interval before warping solder joint welding is fixed interval 5mm.Secondly,the average stress intensity factor can effectively predict the fatigue life of solder joints.This article addresses the effect of warping defects on the average stress intensity factor.The average stress intensity factor can effectively predict the fatigue life of solder joints.By comparing and analyzing the average stress intensity factor of qualified solder joints and warping defect solder joints,determine the influencing factors and influence rules,and compare the average stress intensity factor of the two under the same loading force to find the influencing factors affecting warping defects.There are the thickness t of the plates,the interval b between the welded plates before welding,and the angle a formed after the welding is completed.Finally,by analyzing the warping factor for the first time,and obtaining the expression of the warping factor C,it can be more clearly expressed.The influence of each factor on the stress intensity factor.Finally,the applicability of the warping factor is verified by simulation analysis whose average error between simulation analysis and theoretical derivation is within 6%.The average stress intensity factor accuracy of the warping defect solder joints corrected by the warping factor is 83% through experimental verification.The work of this thesis shows that the warping factor can effectively reflect the effect of warping defects on the average stress intensity factor of solder joints,and has good accuracy and applicability for the fatigue life prediction of warping defect solder joints.