Effect of loading cycle asymmetry on cyclic crack resistant characteristics of heat-stable steels

Results of studies performed with large-sized specimens are presented to reveal the effect of loading cycle asymmetry on regularities of fatigue crack propagation (FCP) in heat-stable steels of various strength - 15Kh2MFA(1), 15Kh2MFA(2) and 08Kh18N10T. The specimen thickness was 150 mm; the loading cycle asymmetry factor varied within 0.1-0.75. A 0.1-0.75 increase in the cycle asymmetry factor is shown to appreciably reduce the FCP rate in the mean- and high-amplitude domain, to considerably decrease the critical FCP rate and to exert no influence on the critical stress intensity factor under cycling loading. Dependence of the FCP rate on the swing of the crack apex opening value is found to be invariant to the loading cycle asymmetry in both the elastic and elastoductile domains for all the steels studied