Fatigue crack initiation from a notch tip under a cyclic compressive load

Notched specimens of 30Cr2WV, an ultra-high-strength steel, were subjected to cyclic compressive and tensile loading, and the length of initiated cracks was measured using a microscope. It is found that a fatigue crack can initiate from a notch under cyclic compressive loading, but the number of cycles required for crack initiation is four times as large as under cyclic tensile loading. It is also found that under cyclic compressive loading, a crack does not propagate after reaching a certain size. However, when the minimum cyclic load is near zero, the number of cycles to crack initiation under compressive loading significantly decreases and the fatigue crack propagates continuously.