Abstract
Fatigue crack growth behavior and its governing factors were investigated by analysing the test data obtained under K-increasing conditions on various structural materials. The fatigue crack growth rate curves exhibited a trilinear form in the so-called Region II. This trilinear form also appeared in the relationship of da/dn versus the effective stress intensity range ΔKeff and the transition points in the relationship corresponded to those in the plot of the crack opening ratio U against ΔKeff.
Irrespective of materials, the effect of stress ratio on the crack growth rate can be well evaluated in terms of ΔKeff.
The fracture ductility of material εf was found to exert a considerable effect on the fatigue crack growth rate and the following empirical equation was proposed to account for the effect of material properties on the crack growth rate;
da/dn=c/√εf(ΔKeff/E)m
