Optimization of a reshaping rivet to reduce the protrusion height and increase the strength of clinched joints

Conventional mechanical clinching attracted more and more attentions in recent years, but the application of mechanical clinching might be restricted because of the exterior protrusion above the sheets which could affect the performance of clinched joint. In order to reduce the protrusion height and increase the strength of clinched joints, a new method using a reshaping rivet to reshape the clinched joint was proposed in this paper. In the reshaping process, the reshaping rivet was embedded in the clinched joint, then the protrusion was compressed in a single stroke with a pair of flat dies. Finite element simulation and orthogonal design were used to optimize the geometrical parameters of the reshaping rivet in terms of cross-tension strength. The best combination of geometrical parameters of the reshaping rivet was gotten by simulating 25 groups of different combinations. Static strengths of the joints before and after reshaping were compared experimentally to validate the performance of the reshaping method. In the experiment, the protrusion height of the joints was reduced to 1.0 mm. The average cross-tension strength and tension-shearing strength were increased from 957.9 to 1154.9 N and from 1229.4 to 2757.3 N respectively.