Enhancing joint performance with reshaping self-piercing riveting: A comparative study of die structures and optimization techniques

Self-piercing riveting (SPR) is a widely used assembly technique in automotive and aerospace manufacturing, valued for its ability to join dissimilar materials. However, the bottom protrusion of SPR joints may compromise performance, limiting its broader application. To reduce bottom protrusion and enhance joint strength, this study proposes a reshaping self-piercing riveting (RSPR) method. This study investigates the RSPR process through simulations and experiments using Al6061 and 5052-H34 aluminum alloys. A multi-objective genetic algorithm with a Kriging model and orthogonal experiments was employed to optimize both pip and flat dies. The stress and strain distribution and forming characteristics during reshaping were analyzed, and the mechanical properties and failure mechanisms of SPR and RSPR joints were compared. The results show that the reshaping method significantly reduces the bottom protrusion height and guides secondary flaring of the rivet. After reshaping, the maximum shear strength increased by 20 % for the pip die and 28 % for the flat die, while peel strength improved by 24 % and 25 %, respectively. The flat die showed superior reshaping performance. The Kriging model combined with the multi-objective genetic algorithm proved effective in guiding the optimization of SPR joints. This research lays a robust foundation for further investigations into the scalability and applicability of RSPR across various industrial sectors.