Studies on the Fatigue Crack Initiation and Propagation : Report 1, Effects of Crack Length, Stress Range and Minimum Stress on Fatigue Crack Propagation

Abstract

The fatigue crack propagation behaviors were investigated on HT80 steel plates under net section stress control in which stress range and minimum stresses were widely varied. The fatigue crack growth rates were proportional to the effective crack length 2a_e which was an actual crack length 2a modified by the finite width effect of the specimen. When minimum stress δ_min was in compression side, the growth rate depended on maximum stress δ_max and in tension side, it depended on stress range Δδ_n. As the result, the effects of crack length, stress range and minimum stress on the fatigue crack propagation can unifyingly be shown such that the crack growth rate is proportional to the cyclic plastic zone size at a crack tip[numerical formula]. Where, δ_y is yield strength of material and δ_n is δ_max when δ_min≤0 and is Δδ_n When δ_min≥0