Crack propagation in high stress fatigue

Abstract An examination of the fracture surfaces of ductile metal specimens broken in high stress fatigue has revealed the occurrence of fracture ripples similar in appearance to those resulting from low stresses, but considerably larger. By sectioning specimens strained to various stages of the fatigue stress cycle, it has been shown that crack propagation and fracture ripple formation are the consequences of the successive rounding and sharpening of the crack tip during each stress cycle. The hypothesis that high stress fatigue is different in character from low stress fatigue and results from a ‘delayed static fracture’ is not in accord with the present observations.