抄録
In this paper, an effective and convenient method for estimation of low cycle fatigue life based on the small-crack growth law was proposed, and the factors that control fatigue life were clarified. The main results obtained are as follows:(1)Low cycle fatigue life is controlled by three factors:crack initiation length, crack propagation limit length and relative crack growth rate. (2)Fracture in pearlitic spheroidal graphite cast iron(PDI)starts from a microshrinkage that exists on the neighboring surface in the case of a cylindrical specimen;thus, the crack initiation length in PDI is larger than that in its matrix material(0.85%carbon steel;JIS SK5). (3)Preexisting cracks originating from defects shorten the crack propagation limit length. (4)The relative crack growth rate is accelerated by the increase in crack opening displacement range near the crack tip.
