Simulation analysis of crack formation in self-piercing riveting process of 7075 aluminum alloy

To investigate the formation and propagation of cracks in the self-piercing riveting process of high-strength aluminum alloy, the Johnson-Cook constitutive model and fracture criterion were calibrated based on the experimental results of the mechanical properties of 7075 aluminum alloy. A simulation model for the self-piercing riveting forming process was established to analyze crack initiation and growth during the formation of high-strength aluminum alloy self-piercing riveting joints. Experimental validation of the self-piercing riveting process was also conducted. The study has revealed that crack initiation primarily occurs in the mechanical interlock zone and the bottom of the lower sheet, with the lower sheet material being the main region for crack formation. Most cracks propagate radially along the joint, while a small number of circumferentially extending cracks begin to appear at the bottom of the joint as the riveting process progresses. By comparing the load-travel curves from both simulation and experimental processes, as well as the geometric characteristics of the mechanical interlock structure, the errors in the final forming force and the size of the mechanical interlock structure are found to be within 16%. This validates the reliability of the established self-piercing riveting forming simulation model and provides a theoretical foundation for subsequent quality control in the self-piercing riveting process.