Modelling distortion induced in an assembly by the self piercing rivet process

Abstract

Traditionally, prediction of the dimensions of an assembly has concentrated on the variation of the constituent components and fixtures. Although recent methods have accounted for both statistical variation and flexibility of sheet metal components, the impact of the joining process has largely been ignored for riveted and spot-welded assemblies. The self-piercing rivet (SPR) has been used increasingly in the automotive industry for joining lightweight aluminium body structures, but the localized distortion around an SPR has been shown to be greater than that associated with the spot weld commonly used in steel body constructions. Consequently incorporation of such distortion into the simulation process for predicting the overall distortion of assemblies would be useful. This paper presents a simulation method based on a local/global approach where the distortion occurring around a single SPR is projected on to a global assembly at each rivet location. The results for both flat sheet assemblies and a simple top-hat assembly are presented for comparison and show that the method can be valuable in the early design stages by predicting the distortion from the joining process. Some suggestions for improving the method are also discussed.