SEDL / STP / STP982-EB / STP27226S

Analytical and Experimental Study of Crack Closure Behavior Based on an S-Shaped Unloading Curve

Chen, D
Associate professor, Jiang Nan University, Wuxi,

Nisitani, H
Professor, Faculty of Engineering, Kyushu University, Higashi-ku, Fukuoka,

Pages: 14    Published: Jan 1988

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Abstract

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, ΔK^effop = K^max − K^op or ΔK^effcl = K^max − K^cl, 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 U^op(ΔK^effop/K^max) and U^cl(ΔK^effcl/K^max) of a steadily propagating crack are mainly controlled by K^max and the stress ratio R.