Abstract
A fatigue crack growth test was performed on a cracked SUS304 test specimen. Fracture surface observation was performed by SEM to clarify whether the fracture surface was due to fatigue crack growth or plastic collapse. The results revealed the following. To investigate the relationship between the crack coalescence behavior and the crack face distance, H, under fatigue conditions, the crack tip distance, S, was fixed, and the effect of H was investigated by fatigue tests. As a result, the cracks did not coalesce in any of the specimens. As a result of fracture surface observation, clear striations were observed from near the front to near the center of the crack tip, crack propagation occurred in the horizontal direction over a relatively long distance due to fatigue, and then gradually plastic collapse appeared on the fracture. However, it was found that the crack propagates horizontally and leads to plastic collapse. Comparing with the results of the previous study under creep conditions, in the high H region, crack coalescence was not observed under both fatigue and creep conditions, showing similar behavior. In the low H region, crack coalescence was observed under creep conditions, but not under fatigue conditions.
