Fatigue thresholds of precracked specimens predicted by modified strip-yield model for plasticity-induced crack closure.

• The effects of precrack lengths and material yield stress on crack closure development are examined. • A new master curve equation is proposed for the cyclic R-curve. • The fatigue thresholds of materials with defects are successfully derived. A strip-yield model modified to leave plastically deformed stretch in the wake of the advancing crack tip is applied to simulate the development of plasticity-induced crack closure with crack extension from precracks with various lengths under the stress ratio R = 0. The effects of precrack length and yield stress on fatigue thresholds were systematically examined. Because of a sharp increase of crack opening stress with crack extension, the effective stress intensity range Δ K eff drops initially and then turns to increase. Assuming the threshold value of Δ K eff for steels, a master curve equation is proposed for the cyclic R-curve. The effects of precrcrack length and material yield stress on fatigue thresholds are successfully derived. [ABSTRACT FROM AUTHOR]