Numerical study of the effect of double cold expansion of rivet hole on the residual stresses distribution

Abstract

The hardening of rivet hole is a mechanical process used to reduce the level of the resulting stresses due to loading in order to delay the crack initiation and propagation. This technique is used to improve fatigue life and to increase the intervals between structural inspections. The experimental tests have shown that the low residual stresses resulting from cold expansion and the first fatigue cracks are located at the entrance face used for hardening. To solve this problem, a double cold expansion of rivet hole in the opposite direction is proposed. This article presents the results of three-dimensional finite element simulation of double cold expansion process in the opposite direction using Abaqus software. The residual stress distribution in rivet hole of aluminum alloy Al2024-T3 induced by tapered pin was analyzed. The obtained results show that the residual stresses vary through the material depth, are maximal in mid-depth and are strong at the exit face and moderate at the entrance face. They also show that the double cold expansion in the opposite direction increases the residual stresses at the entrance face of the pin, and these stresses reached the values of those generated on the exit face, enhancing the fatigue life.