Estimation of remaining fatigue life with an energy-based model considering the effects of loading sequence and load interaction

Accurate estimation of remaining fatigue life is crucial to assess the structural durability and reliability of engineering components. For this purpose, an energy-based model is proposed in this paper for modeling the process of fatigue damage accumulation under multistep loading. To account for the effects of loading sequence and load interaction, two parameters, a concept of normalized fatigue driving energy (NFDE) and a load interaction factor, are introduced in the model. The former is based on variable energy-life curves and the latter is formulized as an exponential function of the loading intensity ratio and the number of loading cycles. The implementation procedure of such model only requires the loading information and materials’ basic fatigue properties. Moreover, extensive experimental results of six metallic materials under two-, four- and eight-step loadings with different loading sequences are employed for model comparative study. The results indicate that, compared with several existing damage models, the proposed model can provide better remaining fatigue life estimations under multistep loading.