Quality Optimization Of Clinching Joint For Steel And Aluminum Sheet Based On Material Flow Control

The upgrading and application of lightweight body materials is the basic way to promote the development of lightweight design.With the popularization of multi-material design concept,the joining technology of dissimilar light materials,especially high strength steel and aluminum alloy materials,which are widely used in automobile body,has become a hot topic in the automotive industry.Due to differences in physical properties of steel and aluminum materials,it is difficult to form high-quality solder joints with traditional spot welding,while the clinching technology which relies on the plastic deformation of materials to realize the mechanical joining of sheets,provides a solution for the connection of dissimilar sheets such as steel and aluminum alloy.However,in clinching process,high strength steel sheets and aluminum alloy sheets have difficulties in forming because of poor plasticity,and the strength of the joint is usually unable to meet the requirements.Aiming at the above problems,the preforming method is introduced into the clinching process by using the material flow control strategy,in order to improve the performance of the high strength steel to aluminum alloy clinching joint.Focusing on the quality optimization of clinching joints,the following research work has been carried out:(1)The preforming-clinching process of high strength steel and aluminum sheet based on material flow control was studied.The deformation process of DP600 high strength steel and AA6061 aluminum alloy sheet in traditional clinching process was simulated by finite element software,and plastic flow and forming mechanism of the joint were analyzed.A preforming step was designed to improve the flow behavior of the strength steel sheet in the lower layer,and the feasibility of improving joint quality by preforming-clinching process was verified by simulation.By optimizing the shape of the preformed punch,the advantages of the preforming-clinching process were further highlighted.(2)Automatic modeling method and forming law of preforming-clinching process were studied.With the help of Python language,the automatic modeling and simulation script program of preforming-clinching process based on ABAQUS software was developed,which improved the efficiency of finite element analysis.By using the program to carry out simulation analysis,the influence of process parameters on the preforming state of steel sheet and metal plastic flow in the preforming stage were studied by single factor experiment.Based on sensitivity analysis,the main influencing factors of clinching stage were selected,and the influence rule of each factor on the forming quality of the joint was analyzed,and the range of the factors was determined.(3)The stepwise optimization technology of preforming-clinching process was studied.Combined Latin hypercube sampling method,Kriging model,multi-objective genetic algorithm and orthogonal experimental method,a stepwise optimization strategy for the quality of preforming-clinching joints was established.Firstly,aiming at the process parameters of clinching stage,the Latin hypercube sampling method was used to design the simulation experiment scheme,and combined with the Kriging model and multiobjective genetic algorithm,the optimization of the process parameters was completed.Secondly,based on the optimal parameters in the clinching stage,the matching optimization of preforming stage’s parameters were completed by orthogonal experiment.Thus,the quality optimization of high strength steel to aluminum sheet joint was realized,and the overall mechanical properties of the joint was improved.