Application of crack-tip-strain loop to fatigue-crack propagation - Local crack-tip-strain loop of propagating fatigue crack was applied to fatigue-crack propagation. Corrected parameter ΔK_eff^T and newly defined parameter, crack-tip-strain range, {Mathematical expression}, were proposed, were proposed

Cyclic strain at the tip zone of a fatigue crack could be measured continuously by the fine-grating method. At one cycle of fatigue, the loop between strain at the crack tip and applied load was called by the authors the 'crack-tip-strain loop' (CTS loop). The CTS loop, which was thought to imply keys of the crack-growth problems, was applied to the fatigue-crack propagation. ΔK_eff^T was defined from the stress (or load) range of CTS loop as one corrected parameter of ΔK. Moreover, cyclic crack-tip-strain range, {Mathematical expression}, from the strain range of CTS loop was proposed as one possible parameter for fatigue-crack propagation.