疲労き裂成長特性に及ぼす二軸応力条件およびその変化の影響
1988 年 37 巻 420 号 p. 1084-1089
詳細
1988 年 37 巻 420 号 p. 1084-1089
Fatigue tests have been conducted on the cruciform flat specimens of a stainless steel with a center crack by using a high-cycle biaxial fatigue test facility, in order to investigate the effect of biaxial stress on the fatigue crack growth properties ΔKI-da/dN. From the comprehensive experiments, no effect of biaxial stress was found on ΔKI-da/dN relation, if the crack was large and the stress level was low. However, a significant effect of biaxial stress appeared when the crack was small and the stress level was high.
In this paper, the critical region where the effect of biaxial stress appears was clarified quantitatively, based on the crack length measured and the stress level used in the biaxial fatigue tests.
Moreover, the effect of changing biaxial stress condition on the fatigue crack growth properties ΔKI-da/dN was investigated. Significant acceleration of the crack propagation was observed just after the uniaxial or equibiaxial stress condition was changed into the shear stress condition. This acceleration cannot be explained by the crack closure and one of the reasons for this acceleration seems to be the change of plastic zone shape at the crack tip.
