変動荷重下の疲労き裂進展速度と開閉口挙動に及ぼす残留応力の影響(<特集>疲労特集)

概要

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Fatigue crack growth tests were carried out under constant amplitede, repeated two-step and random loadings by using the test specimens which have a longitudinal residual stress due to water cooling from a high temperature. Crack closure were measured by using the minicomputer-aided unloading elastic compliance method. The crack opening stress intensity, K_<op>, under varying loading was found to be controlled by the maximum stress intensity range-pair, (Δ_<rp>K_<max>, and its actual stress ratio, R', which is defined as R'={(K)_<min>+K_r}/{(K)_<max>+K_r}, where (K)_<max> and (K)_<min> are the maximum and minimum applied peak stress intensity in the varying loading respectively, and K_r is the stress intensity factor induced by the residual stress. And also, K_<op> was found to coincide with the constant amplitude test results having the identical stress intensity range ΔK and stress ratio R with (Δ_<rp>K)_<max> and R'. The linear accumulation law of crack growth in terms of the effective stress inpair, Δ_<rp>K_<eff>, was confirmed to give a good estimation of the fatigue crack growth rate under varying loadings even in the residual stress field.
1987-10-15