High Cycle Fatigue Model Based on Brittle Damage Mechanism

An isotropic continuum damage mechanics model for high cycle fatigue derived from irreversible thermodynamic dissipative theory is presented.The model is different from Lemaitre model in damage mechanisms.The former is based on a brittle mechanism,and the later is ductile.The model incorporates successfully the high cycle fatigue into a unified thermodynamic framework.The effect of stress ratio R is considered in its damage evolution law.According to the high cycle fatigue SN curve under symmetrical loading,a Log S Log N curve for an arbitrary stress ratio R can be derived by using this model.The model has been applied to the smooth specimen of LC9 high strengthen aluminum alloy.A good agreement between theoretical Log S Log N curves and experimental ones is obtained.