Considerations of grain orientation and work hardening on short-fatigue-crack modelling: de los Rios, E.R. and Navarro, A. Philos. Mag. A Mar. 1990 61, (3), 435–449

Abstract

Centrally cracked specimens of JIS SM58Q and HT80 steels were fatigued. The fatigue crack growth rates, da/dn, and the stress intensity threshold levels, ΔKth were measured over the range of stress ratio, R, from −1 to 0.8 by the use of an automatic method of continuously decreasing stress intensity factor with crack extension. The measured ΔKth was well represented as |ΔKth/2|R=(1−R)γ|ΔKth/2|R=0; and the propagation rate, as da/dn = A(1−R)γm[(ΔK/2)m − {(1 − R)γ|ΔKth/2|R=0}m] for −1≦R≦0.33 or da/dn = A(1 − 0.33)−γm [(ΔK/2)m {(1 − R)γ |ΔKth/2|R=0}m] for 0.33 < ≦ 0.8.