Fatigue Rated Fastener Systems: an AGARD coordinated testing programme

Report (1985)
Copyright: Campus only
Aluminium alloys Bending Standardization Costs Flight simulation Parameters Load transfer Surface roughness Machining Lap joints Fatigue life Fatigue tests Statistical correlation International cooperation Fasteners Joints (junctions) Boreholes fittings Surface finishing Tables (data)
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Published Date

31-05-1985

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NLR-TR 85117 U

Abstract

The report contains the description, results and conclusions of a fatigue test programme which assessed the fatigue lives of fastener systems using different joints. High load transfer single shear joints were evaluated in a core programme; secondary bending and load transfer were determined experimentally. About 750 specimens were fatigue tested in seven countries. Tests were carried out mainly under FALSTAFF; some test series were done under MINITWIST and constant amplitude loading. The sheet materials used were from the 2000- and 7000- aluminium alloy series. The fasteners ranged from standard bolts to tapered fasteners, installed in drilled, broached, reamed or cold worked holes. Highlights of the data indicate that: - secondary bending is a prime parameter. At moderate to high values it tends to nullify the effect of fatigue enhancement fastener systems; - at low to moderate secondary bending the fit, clamping and cold work are prime parameters. At high load transfer and at high fatigue load levels the best results are obtained with cold worked holes plus high interference fit fasteners; - double shear joints clearly show a fastener system rating; - the hole quality as such is not a prime parameter; - increasing costs of the fastener system might result in a better fatigue performance. Moderate to high secondary bending tends to nullify the extra costs of fatigue enhancement fastener systems.