Multi-planar injection lap riveting

Abstract

This paper is focused on multi-planar hybrid busbars made from copper and aluminum for electric energy distribution systems. The objective is to provide an overview of its assembly by injection lap riveting in multidirectional tools and to compare the electrical performance of its joints against that of conventional (in-plane) busbars.

The injected lap riveted joints require a dovetail ring hole and a countersunk hole to be first machined in the overlapped copper and aluminum sheets and then to inject the semi-tubular rivets by compression through the lined-up holes in order to fix the sheets in position. In this work, the injection of the semi-tubular rivets was carried out in a laboratory multidirectional tool set that converts the vertical press stroke into two-orthogonal horizontal movements by means of cam slide units consisting of compression punch holders and sliding wedge actuators attached to the upper bolster.

Experimental results obtained for a multi-planar, three-conductor, rake-shaped elbow of a hybrid busbar system allow concluding that while the required compression force is proportional to the number of injected lap riveted joints, the electrical performance is non-proportional due to changes in the distribution of electric current density. Numerical simulation with finite elements gives support to the discussion and allows readers to recognize the pitfalls of designing busbar joints exclusively based on mechanical requirements.