Published: Jan 1988
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Based on the S-shaped unloading hysteresis curve a new method for determining the crack closure has been developed in which the plastic deformation near the crack tip is taken into consideration. The crack growth rate can be expressed uniquely by the effective stress intensity range, ΔKeffop = Kmax − Kop or ΔKeffcl = Kmax − Kcl, which is independent of the stress ratio and the loading history. The tip of a nonpropagating crack does not open even under the maximum tensile load during one loading cycle. The measured values of the crack opening ratios Uop(ΔKeffop/Kmax) and Ucl(ΔKeffcl/Kmax) of a steadily propagating crack are mainly controlled by Kmax and the stress ratio R.
fatigue, fatigue crack propagation, crack closure, unloading elastic compliance method, effective stress intensity factor, nonpropagating cracks, carbon steels
Associate professor, Jiang Nan University, Wuxi,
Professor, Faculty of Engineering, Kyushu University, Higashi-ku, Fukuoka,