Fatigue of single- and double-rivet self-piercing riveted lap joints

The fatigue behaviour of single- and double-rivet aluminum alloy 5754-O self-piercing riveted (SPR) lap joints has been investigated experimentally and analytically. With the single rivet, the experimental program involves a set of 27 cyclic tension tests on joints with 1-, 2- or 3-mm-thick sheet coupons. In most cases (85%), fatigue cracks are found to initiate in the gross section on the faying surface of the upper sheet. With two rivets (installed in two rows), the experimental program consists of nine cyclic tension tests, three for each of the three combinations of riveting orientation possible, on SPR joints consisting of 2-mm-thick sheet specimens. The fatigue life of double-rivet joints is found to be strongly dependent on the orientation combination of the rivets. Monotonic tests with the double-rivet joints also reveal an influence of orientation combination. In addition to experiments, values of local stress and rivet-sheet microslip in the single-rivet joints have been evaluated through three-dimensional elastic finite-element analysis. The analyses are used to interpret experimental observations of fatigue crack initiation location, life and fretting damage severity.