Research On Rivet-free Connection Technology Of Non-equal Thickness Steel-aluminum Heterogeneous Sheet

With the continuous improvement of environmental requirements,the lightweight of automobiles is increasingly valued by major automobile manufacturers,and reducing the weight of automobile bodies is an important way to achieve lightweight of automobiles.High strength steel and aluminum alloy are ideal materials for lightweight automotive applications,and their connectors have the characteristics of light weight and high safety performance,making them increasingly widely used in the design and manufacturing of automobiles.However,due to the limitations of traditional connection technologies,it is difficult to achieve effective connection between heterogeneous plates.The rivetless connection technology,as a new type of cold deformation non-destructive connection process,is simple and has high connection strength,and can achieve the connection of two or more layers of heterogeneous plates.This article takes HC340/590DP dual phase high-strength steel and 5052 aluminum alloy as the research objects.The mechanical properties of high-strength steel and aluminum alloy are tested through uniaxial tensile tests,and the force displacement data of the two materials are measured,and the true stress-strain curve is drawn.Establish three flow stress models:Ludwik,Swift,and Voce,and evaluate the fitting curves of the models.Among them,the Swift model has the best fitting effect and the highest degree of curve fitting.Based on the material properties of high-strength steel and aluminum alloy,non riveted connection tests were designed for different thicknesses of steel and aluminum plates,and the formed cross-sections of different combination joints were observed.Morphological parameters such as neck thickness t_n and interlocking value t_u of the joints were measured.Based on the mold size,a finite element numerical model of non riveted connection was established in ABAQUS,and the forming process of non riveted connection was simulated.The stress state changes in the three areas of the joint neck,bottom middle,and bottom edge were mainly analyzed,and the forming process of non equal thickness plate joints was explained.Comparing the numerical simulation results with the experimental results,the error rates were all below 10%,verifying the effectiveness of the numerical model.Using a finite element model without riveting connection,numerical simulation was conducted on the forming process of different sheet thicknesses and mold parameters.The effects of high-strength steel and aluminum alloy with different thicknesses on the upper and lower sheet were studied,as well as the effects of mold parameters such as punch radius,concave radius,and concave depth on the forming quality of the joint.The changes in key dimensional parameters such as neck thickness,interlocking value,and bottom thickness of the rivetless joint were analyzed.By conducting shear tensile tests and cross tensile tests,the failure forms of joints were measured,and the tensile shear strength and energy absorption of joints with different thicknesses and overlapping methods were studied.The effects of different forming forces and stretching speeds on the forming quality of joints were analyzed.The results show that the S10-A12 joint has the best forming effect,with a maximum shear strength of 2255N and a maximum tensile strength of 1210N.At low and high speeds,both shear and tensile strength remain at high levels;When the forming force of S14-A12 joint is 50KN,the forming quality of the joint is the best,with a maximum shear strength of 2100N and a maximum tensile strength of 920N.