Assessing the effects of riveting induced residual stresses on fatigue crack behaviour in lap joints by means of fractography

The interference fit provided by solid rivets induces a residual stress field beneficial to the fatigue performance of riveted lap joints. Attributing benefits in crack growth nucleation and growth behaviour within this residual stress field is non-trivial. Once fatigue cracks become visible on the surface of a joint they have already grown beyond the region of beneficial residual stress. In order to circumvent this problem, fractographic techniques were employed to evaluate postmortem the influence of the rivet squeeze force and resulting residual stress field on crack behaviour. Results demonstrated that within the range of rivet squeeze forces studied, a 3-fold reduction in crack growth rate is achievable at high rivet squeeze forces, representing a marked improvement in damage tolerance of the joint.