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Abstract

A new model of a growing fatigue crack is proposed based on the rigid-plastic-strip yielding approximation under the assumption that the pressure distribution existing between contacting crack faces behind the tip determines the value of stress intensity factor at the crack-tip opening point and also affects the amount of subsequent opening of crack faces.This model was verified in the experiment of fatigue crack propagation in two kinds of quenched-and-tempered carbon steel, where the behavior of opening and closure of crack faces was examined with an optical microscope. The amount of contact pressure was found to be a sole function of the mean value of the applied stress intensity factor.Finally, the propagation rate of a fatigue crack was expressed as a function of the reduced range of stress intensity factor without respect to the values of stress ratio R.