Influence of initial fit tolerance and squeeze force on the residual stress in a riveted lap joint

Abstract

Residual stress in a riveted lap joint is tightly related to the fatigue performance of the structure. This paper is devoted to a comprehensive study of the residual stress distribution in a plate that resulted from the riveting process, concerning the influence of initial fit tolerance and the squeeze force. Following a finite element (FE) simulation, an analytical model of the riveting process was built based on the deformation theory of elasticity and plasticity. The result shows that nonuniform expansion along the axis of the hole was observed which resulted in a nonuniform distribution of through-thickness stress. Huge compressive stress in the tangential direction was observed surrounding the hole, which explains the long life effect due to interference fit. Both increasing the squeeze force and initial fit tolerance would lead to increased residual stresses in the plate. Compared to a bigger squeeze force, the initial interference fit is more likely to produce a high residual stress level. In the case of initial interference fit, the residual stress variation will be less sensitive to the change of the squeeze force than that for clearance fit. With increasing squeeze force, the riveted lap joint may appear in different crack morphology and location under the fatigue load. Except for the fretting, secondary bending, and compressive residual stress, the boundary of the hardening zone at which the tangential stress turns into maximum tensile stress accounts for such phenomenon.