抄録
Low cycle fatigue test were perfonned for austenitic stainless steel, SUS316NG. The effect of pre-strain histoiy on the small crack growth was investigated in detail using cellulose acetate replicas. The pre-strained test revealed that usage factor for fracture, UF_f, decreased with increasing usage factor for pre-strain, UF_<pre>, due to cyclic strain hardening and softening, whose contribution was more remarkable when UF_<pre> of pre-strained test increased. Crack growth characteristics were evaluated by J integral range, which is an elasto-plastic fracture mechanics parameter. Crack growth characteristics were measured under constant amplitude loading and were compared with those measured by pre-strained tests. The decrease in UF_f was explained by these fracture mechanics approach. At the same crack length, crack growth rate in pre-strained tests is larger than that in constant amplitude tests, because stress range in pre-strained test is higher than that in constant amplitude test. Crack growth of pre-strained test was predicted by elasto- plastic fracture mechanics approach, and resulted in decreased UF_f.
