Analysis of the effect of cold-working of rivet holes on the fatigue life of an aluminum alloy

An experimental and analytical program was carried out to assess the effect of cold-working by hole expansion on the fatigue life of Alclad 2024-T3 aluminium alloy. The magnitude of the residual stresses introduced into the specimens due to cold expansion was evaluated by an X-ray diffraction procedure. Specimens containing non-cold-worked and cold-worked holes were tested under cyclic loading at an R-ratio of 0.1. The rates of fatigue crack propagation were determined by measurement of striation spacing. A main outcome of the present work was the determination of the crack-opening stress intensity as a function of the range of the stress intensity factor. For the cold-worked specimens an inverse methodology was adopted to estimate the crack-opening stress intensity as influenced by the residual stress field. Finally, a crack growth model was used to provide a correlation with the experimental fatigue lifetimes.