Abstract
JIS SNCM 439, S 35 C and SUS 304 steels were low-cycle fatigued with mean stress and strain under load-and displacement-controlled conditions. The cyclic J integral range, ΔJ, was not effective for the evaluation of the crack growth rate under test conditions accompanied by ratchet deformation. Therefore, the parameter of ΔJ/{1-(Φcmin/Φcmax)}0.2, which controlled the acceleration of the crack growth rate due to ratchet deformation as well as the crack growth rate under a fully reversed cyclic strain, was usefully proposed here, where Φcmin and Φcmax were the minimum and maximum crack-center opening displacements. The crack tip opening displacement range ΔΦt(200)=A(ΔJ)q. In general, the power exponents, q, were smaller than the values of 1/(n'+1) or 1/(n+1) estimated by assuming the HRR singular field around the fatigue crack tip, where n' and n were the cyclic and monotonic strain hardening exponents of materials
