Single overload effect in short crack

The effect of single overload on the retardation of fatigue crack propagation and crack arrest was examined on short crack less than a few hundred microns. The effect of stress ratio of baseline load was also investigated. The variation of crack closure stress caused by overload was measured. The retardation occurred even in short crack, which could be explained by the increase of crack closure stress caused by overload. The baseline stress ratio also affected the retardation. Retardation occurred even in 50 μm crack for baseline stress ratio R = 0. In the case of R = -1, however, no retardation occurred in short crack less than 100 μm since the increase of crack closure stress was restrained by the compressive stress of baseline load.