Abstract
An experimental study of fatigue crack propagation and crack closure behaviour, in compact tension specimens of AISI 316 (N) weld has been conducted. The crack closure load was determined from the changes in the slope of the load–displacement curves using global crack mouth opening displacement (GCMOD) type gauge. The results were compared with those measured by acoustic emission technique which showed good agreement with each other. The experimental data bear clear evidence of fatigue crack closure. The crack opening force was found to increase moderately with crack length and increasing R-ratio, under a constant P max of 5 kN. Above a critical R-ratio of 0.45 (approximately), the crack closure load is smaller than the minimum applied load. A good correlation was obtained for Δ K eff/Δ K = 0.6684 – 2.4135 R + 7.0077 R 2 in the range 0 ⩽ R ⩽ 0.5. The magnitude of crack closure is used to interpret observed crack growth behaviour at different R-ratios.
Published Version
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