S0301-1-4 低サイクル疲労を受ける切欠付オーステナイトステンレス鋼のき裂先端開口角解析(疲労特性に及ぼす各種因子の影響(1))

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The crack tip opening angle (CTOA) is a viable ductile fracture criterion and could be used for elastic-plastic, crack propagation analysis without the constraint of LEFM. This paper reports on our investigation to correlate ΔCTOA with the crack propagation rate, da/dN, in stainless steel (SUS 316), single edged notch bend (SENB) specimens. The SENB specimens were cyclically loaded at various constant load amplitudes with a load ratio, R〜0.01. ΔCTOA at the initial phase of fatigue crack extension was measured by moire interferometry and inferred from a ΔCTOA versus ΔCMOD master curve, which was constructed through CMOD and crack profile measurements, during the latter phase of fatigue crack extension. The fatigue data was then used to construct a da/dN versus ΔCTOA relation, similar to Paris' law of LEFM, in the presence of small to large crack tip deformation and net section yielding.
2009-09-12