Fatigue crack initiation at notch root under compressive cyclic loading

Systematic experimental investigation was carried out to examine the phenomena of crack initiation under pure compression fatigue condition with samples having different pre-prepared notches. Finite element analysis (FEA) simulation was also conducted to determine the stress concentration and stress distribution for the tested samples. Although a smooth bar tested under the pure compression fatigue condition with a peak compressive load equal to the yield strength did not show any crack formation, crack was indeed detected under compressive fatigue load in those samples whereby a critical stress concentration was reached. Such critical condition may be expressed through a critical von Mises stress level. In addition, experimental observation indicates that such crack initiation process was indeed always associated with localized plastic deformation