Study on performance of self-piercing riveted joints of aluminium alloy three-layer sheet for automotive bodies
The self-pierce riveting(SPR)joinability of aluminium alloy three-layer sheet for automotive bodies was researched by optical microscopy,electron back scattered diffraction(EBSD),tensile-shear test,peel test and simulation analysis.The results show that the interlock value and residual bottom thickness of joints for 5182 aluminum alloy three-layer sheet are significantly influenced by the riveting speed.When the riveting speed is 270 mm·s-1,the joint has the maximum interlock value of 0.29 mm and the minimum residual bottom thickness of 0.17 mm.Moving forward,the sample with the highest interlock value was chosen for study.During tensile-shear and peel tests,it is discovered that the failure mode for all samples is the upper layer sheet being pulled out from the lower layer sheet.The average peak shear load reaches 3.05 kN,while the average peak peel load is only 0.67 kN,indicating that the peak shear load of joint is signifi-cantly greater than its peak peel load.The mechanical properties of the riveted joint are greatly influenced by the microstructural character-istics near the joint.The joints were analyzed by microstructure and EBSD.It is found that the closer the upper sheet is to the area near the rivet,the larger the deformation of material.The deformation of middle layer sheet is severe.Both the upper and middle layers sheets exhibit elongated grains due to deformation,but the middle layer sheet develops a distinct fibrous structure.The plastic deformation of the bottom layer sheet is less than that of the upper and middle layers sheets,with grains near the rivet showing clear signs of deformation,while other areas maintain the equiaxed grain structure.
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