Study On Hole-clinching Of Magnesium Alloy And High Strength Steel Dissimilar Plate

In recent years,with the rapid development of automobile industry,automobile lightweight technology has been paid more and more attention.The main way to realize automobile lightweight technology is to use light alloy materials and high strength materials instead of traditional body materials.The simultaneous application of magnesium alloy and high-strength steel materials make the joining technology become the key of engineering application.Because of the characteristics of low plasticity of magnesium alloy materials and high yield strength and high surface hardness of high strength steel materials,the traditional joining technology can not realize the effective joining between magnesium alloy plate and high strength steel plate.In this paper,the effective joining between AZ31 magnesium alloy and 22MnB5 high strength steel plate is realized by hole-clinching,which is of great significance to solve the joining problem between magnesium alloy and high strength steel plate.Firstly,the CAD model of hole-clinching between magnesium alloy and high strength steel plate is established,and the process is simulated by DEFORM finite element analysis software.The results show that the force of punch increases with the increase of vertical displacement,and the main factors affecting the quality of joint are neck thickness,undercut and bottom thickness.Through the analysis of the stress,strain and damage of the joint,it is known that the main factor affecting the quality of the joint is the neck thickness of the joint.Through the failure mode of the hole-clinching joint is analyzed by uniaxial tension finite element simulation.The results show that the neck fracture failure occurs when the joint is stretched along the axial direction,when the joint is stretched along the tangential direction,the upper plate is cut off directly at the neck of the joint.It can be seen that the main failure mode of the joint is neck fracture failure.Then,the effects of the neutrality of the die and the draft angle of the punch,the radius of the punch,the radius and the depth of the die on the joint strength are analyzed.The results show that in the process of hole-clinching,the offset of the die will directly affect the joint strength of the hole-clinching joint.Through the control variable method and the orthogonal test method,it is found that different die parameters have different effects on the joint strength,in which the greatest influence on the neck thickness is the draft angle of the punch,the second is the depth of die.and then is the punch radius,the radius of the die has the least influence of the joint.The factor that has the greatest influence on the undercut is the draft angle of the punch,the second is the radius of the punch,and then is the radius of the die,the depth of die has the least influence of the joint.The factor that has the greatest influence on the bottom thickness is the draft angle of the punch,the second is the radius of punch,and then is the radius of die,the depth of die has the least influence of the joint.On this basis,the optimal die parameters of hole-clinching are obtained,and the feasibility of the process is verified by hole-clinching experiment.In the end,the effect of temperature on the strength of hole-clinching joint is studied by means of finite element simulation and experiment.The simulation results show that the lower temperature of the upper plate makes the greater equivalent strain of the upper plate,the greater equivalent stress of the lower plate,the greater damage of the joint and less likely the joint is to form a "C" interlock structure.The experiment results show that the lower temperature makes the worse plastic fluidity of magnesium alloy sheet,and the easier it is to fracture.With the increase of temperature,the plastic fluidity of magnesium alloy increases,and it is easier to form effective joints.Through the simulation and experiment,it is concluded that in order to realize the effective joining between magnesium alloy and high strength steel heterogeneous plate,the optimal experiment temperature of magnesium alloy sheet is 220?.