Evaluation of an energy-based fatigue approach considering mean stress effects

In this paper, an attempt is made to extend the total strain energy approach for predicting the fatigue life subjected to mean stress under uniaxial state. The effects of means stress on the fatigue failure of a ferritic stainless steel and high pressure tube steel are studied under strain-controlled low cycle fatigue condition. Based on the fatigue results from different strain ratios, modified total strain energy density approach is proposed to account for the mean stress effects. The proposed damage parameter provides convenient means of evaluating fatigue life with mean stress effects considering the fact that the definitions used for measuring strain energies are the same as in the fully-reversed cycling (R = -1). A good agreement is observed between experimental life and predicted life using proposed approach. Two other mean stress models (Smith-Watson-Topper model and Morrow model) are also used to evaluate the low cycle fatigue data. Based on a simple statistical estimator, the proposed approach is compared with these models and is found realistic.