A novel nonparametric model for life assessment of high cycle fatigue under uniaxial variable amplitude loading using intrinsic damage dissipation

Several nonparametric models for HCF fatigue life predictions under variable amplitude loading (VAL) have been proposed and gained broad attention from practicing engineers due to their simplicity and ease of application. However, for practical application, the existing standards still use the Palmgren-Miner model, which does not consider the damage due to loading sequence and causes inaccurate life predictions. Hence, an urgent need exists for an equally simple, easy-to-apply, and accurate nonparametric model for engineering applications. Therefore, this study proposes a novel nonparametric model for HCF fatigue life assessment under VAL, which considers the influences of the load sequence. The proposed model is based on cumulative intrinsic damage dissipation under fully reversed tensional loading, which can be modeled based on continuum damage mechanics. A new damage transfer concept based on cumulative intrinsic damage dissipation under fully reversed tensional loading is also proposed for fabricating the proposed model. The proposed model provides better correlations with experimental results than the Palmgren-Miner and other recent nonparametric models. These experimental results cover the total fatigue lives of five materials under two-level, multilevel block loading, multiple periodic overloading, and involute gear under two-stage loading conditions. Furthermore, the proposed model provides a novel approach to easy application for accurately predicting HCF fatigue life under VAL.