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Tests under variable amplitude loading on self‐piercing riveted components with semi‐tubular rivets result in longer service lives than those calculated by linear damage accumulation. An overview of the literature shows that damage sums greater than one are found for other types of riveted joints either, while an explanation for this unusual behavior is still missing. Therefore, this behavior is examined in more detail. A correlation is shown between the damage sum and the hardness of the load spectrum. Considering this correlation, the accuracy of the service life estimation can be improved significantly. [ABSTRACT FROM AUTHOR]

Static and fatigue tests have been carried out on 190-mm-wide fibre metal laminate (FML) riveted lap joints. The specimens were made with a Glare 3-3/2-0.3 material, i.e. a laminate composed of three layers of 2024-T3 aluminium alloy, thickness 0.3 mm and two double layers (0/90) of pre-preg FM-94-27%-S2 glass fibre. Seven configurations were tested which differed in the number of rivet rows (two or three), in the rolling direction of metal layers (perpendicular or parallel to the load direction), in the rivet type (solid or special, such as Hi-Lok or Lock-Bolt), in the rivet material for solid rivets (7050-T73 or 2017-T3), in the rivet diameter (4.8 or 5.5 mm) and in the presence of interlaminar doublers in the overlap area (titanium, aluminium, glass fibre). An additional difference was in the pre-formed rivet head: solid rivets had countersunk head, while Hi-Loks and Lock-Bolts had protruding head. The fatigue tests demonstrated the efficiency of a selective local reinforcement in the overlap area; in some cases, the fatigue resistance was so high that fatigue cracks nucleated in the laminates, rather than in the overlap area, as commonly expected. [ABSTRACT FROM AUTHOR]

A study was conducted to characterize fretting fatigue in self-piercing riveted single-lap joints of aluminium alloy 5754 sheets. The experimental results showed that fretting occurred at three different positions in the joint. It was established that fretting led to surface work-hardening and crack initiation as well as early stage crack propagation. Crack initiated at the surface of the riveted sheets as a result of high stress concentration and propagated oblique to the mating surface under the effect of fretting fatigue. The depth of damage due to fretting depended on the applied load and the cycle time. Microhardness measurements allowed the estimation of the depth of damage due to fretting. These results were observed to correlate well with the length of crack propagation. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Traditional machine countersinking practices create a knife-edge condition in one or more of the outer aluminium layers in riveted GLARE joints. Press countersinking (dimpling) provides an alternative method of countersinking that prevents the formation of a knife-edge; however, its application and potential benefits to fatigue performance in GLARE are not known. This paper investigates the dimple-forming process and its application to GLARE, and the resulting benefits in fatigue crack-initiation life in unfilled rivet holes. Initial results showed that the limited formability of GLARE complicates the dimpling process, but that dimpling shows promise as a method for increasing the crack-initiation life of riveted GLARE joints. [ABSTRACT FROM AUTHOR]