Double-flush riveting by punching and compression

Abstract

This paper presents a new double-flush riveting process to fabricate flat lap joints that can be easily integrated in progressive or transfer multistage tool systems. The process is based on a punching-compression sequence and the design methodology combines experimentation and finite element modeling followed by destructive peel testing. Special emphasis is placed on the identification and selection of punch-to-die clearances to produce tapered cut surfaces that are appropriate for subsequent compression of the solid rivets into double-flush riveted lap joints. Results confirm that rivet materials with lower mechanical resistance than the sheet materials allow fabricating double-flush riveted lap joints with flat surfaces on both sides in which the mechanical interlocking in the undercut area is obtained by plastic deformation of the rivets instead of the sheets. The utilization of aluminum sheets and copper rivets allows extending the process scope of application from structural to energy distribution parts in which the electrical resistance of joints is a critical design parameter.