一方向変化を伴う試験条件下における疲労き裂進展抵抗の弾・塑性破壊力学的評価

概要

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Center-cracked specimens of JIS S35C and SUS 304 steels were low-cycle fatigued under test conditions accompanies by ratchet deformation, and crack opening displacement, crack closure and crack growth were examined. Then, crack growth rates were analyzed in terms of elastic-plastic fracture mechanics parameters. The effect of ratchet deformation on crack growth rate appeared in the log da/dN vs. log ΔJ plot in the way of accelerating crack growth rate, where da/dN is crack growth rate and ΔJ is cyclic J-integral range. Such an acceleration of crack growth rate occurred under test conditions satisfying both of σ^max_net>σ_y and U = 1.0, where σ^max_net, σ_y and U are maximum net cross-section stress, static yield stress and crack opening load range ratio, respectively. The parameter of ΔJ(1-Φ^min_t/Φ^max_t)^0.3 was proposed for evaluating the crack growth rate on a ΔJ basis, where the minimum and maximum values of crack tip opening displacement were denoted by Φ^min_t and Φ^max_t. The da/dN plotted against this parameter forms a straight line independent of ratchet deformation on double logarithmic controlling the croak growth rate under test condition including ratchet deformation.
一般社団法人日本機械学会の論文
1988-05-25