Study On Hot Clinching Technology And Joint Mechanical Properties Of Steel-Aluminium

With the development of technology in the automotive industry in recent years,the requirement of structural lightweight has become higher and higher,and the hybrid structure of high-strength steel and high-strength aluminium alloy has been favoured by the automotive industry for its advantages of high strength and light mass.However,due to the heterogeneous characteristics of the two materials,how to build an effective connection to ensure the mechanical properties of the joint has been a hot topic of research in the academic and engineering fields.For the effective connection of steel and aluminium heterogeneous materials,this paper taking 22 Mn B5 high-strength steel and 7050 aluminium alloy as the research object,proposes a clinching plastic jointing process with induction hot riveting and eddy current cooling valve cooling,develops a device and mould for hot clinching jointing process,and combines experiments and finite element modelling to investigate the forming law and the joint quality of the formed joint of steel and aluminium hot clinching plastic jointing.The main elements are as follows:Determination of mechanical parameters of steel and aluminium heterogeneous metal materials and the establishment of the constitutive model.The first step is to understand the principles of the joining process and the forming process of heterogeneous metal sheets,to design two types of tensile tests:room temperature and heated,and to make experimental measurements of the thermodynamic parameters of the material.Then,based on the results of the unidirectional tensile tests on steel and aluminium,the stress-strain curves relating the sheet temperature to the strain rate are obtained.The Hansel-Spittle thermoviscoplastic constitutive model is used for high-strength steel and the segmented linear plasticity model is used for aluminium alloy.The model parameters are solved to establish the constitutive model of the material and the reliability of the constitutive model of the high-strength steel is verified.Finite element simulation analysis of the hot clinching plastic jointing of steel and aluminium heterogeneous sheet metal.Based on the measured thermomechanical parameters and the constitutive model,a finite element model of the hot clinching plastic jointing was established using software Abaqus.The simulation results were compared and analysed with the key dimensional parameters of the formed joint in the cross-sectional metallographic drawing of the riveted joint test,and it was found that the deviation rate of the neck thickness value was 5.63%,the deviation rate of the self-locking value was 3.76%and the deviation rate of the bottom thickness value was 1.64% for both.The results of the simulation are similar to the real test results,which verifies the feasibility and accuracy of the finite element model.The results of finite element simulations are used to analyse the stress-strain distribution in the forming process of joints under different working conditions of hot clinching plastic jointing process.The neck thickness value t N,the selflocking value tu and the bottom thickness value d are used as important characteristic dimensional factors to assess the quality of the formed joints,and the influence of temperature,punch stroke,punch and die structure parameters on the formed joints during the forming process is analysed.A study of the mechanical properties of steel and aluminium hot clinching plastic joints.The shear and tensile load resistance of formed joints is a key factor in assessing the mechanical properties of joints.The effect of different initial temperatures and cooling methods on the mechanical properties of clinching plastic joints in steel/aluminium heterogeneous sheets was investigated by comparative analysis of one-lap shear and crosslap tensile tests.The results show that the best joint effect is achieved with the top aluminium and bottom steel lap joint method.The best joint quality is determined through comparative analysis when 22 Mn B5 high-strength steel is heated to 700°C,aluminium is connected without riveting by heat conduction only and treated with valve cooling,and the shear and tensile strengths are effectively improved,providing an idea for further plastic connection of steel and aluminium heterogeneous materials.