A MODEL RELATING LOW CYCLE FATIGUE PROPERTIES AND MICROSTRUCTURE TO FATIGUE CRACK PROPAGATION RATES

Abstract

— The fatigue crack propagation rate is related to the cyclic flow stress and the cyclic ductility of materials by means of a ductility exhaustion mechanism. The da/dN vs. ΔK relationship is derived from the assumption that an elemental crack extension occurs when the sum of the fractional fatigue life of an element at various cycles equals unity. A comparison of predicted crack growth curves with those obtained experimentally for representative alloys shows good agreement. The threshold ΔK behavior has been explained in terms of the existence of a threshold plastic strain amplitude.