| With the rapid development of lightweight technology,the clinching of heterogeneous metal is used in automobile manufacturing,aerospace,and home appliance manufacturing.The structure of the steel-aluminium hybrid body is also more and more used in automobile design and manufacturing.The steel aluminium connection has the characteristics of lightweight and high connection strength.However,the traditional connection technology is easy to produce heat effect and damage the material itself,restricting the application and development of the hybrid body of steel aluminium structure.Clinching is a new kind of cold extrusion non-destructive joining technology based on rapid stamping and die extrusion.The small punch is used to cooperate with the die,which makes the plate connection produce axial interlock,and realizes the non-destructive connection of the plate.To realize the clinching of heterogeneous materials with different properties,a clinched device and die were developed to solve the connection problem of6061-T6 aluminium alloy and HC340/590 DP dual-phase high strength steel.The forming law of clinching for steel aluminium and the connection quality under different lap forms were analyzed by experiment and finite element simulation.Based on the introduction of the process principle and joint forming process of clinching for heterogeneous thin plate,the extrusion forming mechanism in clinching is analyzed.The experiment of clinching was designed,and the quality of different joints was measured.The best joint was selected is the US2-LA2 joint.Based on the uniaxial tensile test results of high-strength steel and aluminium alloy samples,the stress-strain relationship of the two materials was obtained,and the flow stress model was established.The fitting effect of the model was evaluated by AARE value and R-value.The Voce model of high-strength steel is good.The Swift model of aluminium alloy is good.It provides a basis for the subsequent numerical simulation of clinching.The numerical model of the upper steel-lower aluminium clinched joint forming process is established using the finite element simulation software.The error rate between the numerical simulation results and the experimental measurement is less than 10%,verifying the numerical model’s effectiveness.The distribution characteristics of the stress field in the joint forming process are described by numerical simulation.Taking the neck thickness,embedded value,and bottom thickness as important dimension parameters,the influence of forming process parameters,punch structure parameters and die structure parameters on the forming quality of clinched joint was analyzed.The variation law of cross-section size of clinched joint in the pressure holding unloading stage is introduced.The deformation rate of the critical size of the joint is less than 5%.The failure mode of the clinched joint was analyzed by destructive test.The tensile shear strength and failure mode of the clinched joint were obtained using the shear test and cross tensile test.The results show that the connection quality of the US2-LA2 joint is good,which can meet the production demand.The shear strength is increased by 62.35%,and the tensile strength is increased by 125%.The strength prediction model predicted the strength and failure mode of the joint,and the traditional tensile strength prediction model was modified.The error rate of shear prediction is less than 20%,and the error rate of tensile strength prediction is less than 10%.It solves the problem that many destructive tests are needed to detect clinched joints’ strength and lay a foundation for the in-depth study of the failure analysis of clinched joints of heterogeneous thin plates. |
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