Abstract
The plasticity-induced fatigue crack closure behaviour has been studied in aluminium alloys 2024-T3 and 7075-T6 using a compliance gauge. Centre-cracked sheet specimens have been tested with stress ratios in the range 0.1–0.4 under a similar stress amplitude condition. The opening stress intensity factor K op as well as the K op/ K max ratio have been investigated as functions of measurement location, yield strength, maximum stress intensity factor K max and stress ratio R. K op and K op/ K max decrease with increasing distance behind the crack tip and decreasing crack length. The K op/ K max ratio is, however, independent of crack length in the close vicinity of crack tip. Whereas R is found to have only a marginal effect on K op, the latter is found to increase with K max and then subsequently to decrease. The findings have been discussed. Empirical formulae have been suggested to predict ΔK eff, R and K max using the multiple-regression method. ΔK eff is found to increase with increasing K max and ΔK.
Published Version
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