Method of installing interference fit sleeved fasteners having radiused intersection for stress coining

摘要

In this fastening system two or more layers of material are fastened together by inserting a hollow sleeved fastener such as a rivet or a bolt into the hole in a high interference fit to expand the hole radially. The sleeve is configured either as a collar and a straight shank or as an angled upper portion combined with a shank for counterbored applications. The intersections between either the collar and the shank or the angle portion and the straight shank are designed with an enlarged radius such that when the sleeve is expanded after the insertion of the fastener inside of it, this radius is expanded, which in turn stress coins the adjacent edge of the hole in the layers. This localized stress coining as well as the hoop stress in the hole surrounding the hole dramatically increases the fatigue strength of the fastened layers in a structure assembly.