微小な疲労き裂の伝ぱに対する一つのモデル

抄録

The growth behavior of small fatigue cracks is clearly different from that of long fatigue cracks. In this paper, a growth law of small fatigue cracks is proposed based on the stochastic damage accumulation model for long fatigue crack growth. It contains the following three parts. (1) The growth rate of small crack growing in a grain is proportional to some power of the process region which is limited by the grain boundary. (2) A transgranular small crack propagates into the next grain over the grain boundary, when the stress is beyond the fatigue limit. (3) A small crack growing through the noncontinuum propagation begins the continuum one, when the plastic zone size of crack tip becomes larger than the average grain size. Many experimental facts about small fatigue cracks are explained on the basis of this growth law.