A Novel Energy-Life Theory-Based Approach to Predict Low-Cycle Fatigue Life of Q345B Under Symmetrical Cyclic Loading

The traditional energy-life theory derives from the strain-life theory and is based on the linear damage theory. This paper proposes a new method for predicting low-cycle fatigue life under symmetrical cyclic loading in response to this issue. The energy conversion law of the Q345B smooth specimen during static tensile and fatigue failure was studied in this paper. A nonlinear cumulative equation for fatigue damage was established with total strain energy as the damage parameter. By establishing the functional relationship between the cumulative total strain energy during fatigue failure and the static tensile fracture energy, the calculation method for critical damage was determined. Then, a new method for predicting the fatigue life of materials under symmetrical cyclic loading was derived. The prediction errors are less than 15%, which is a reduction of more than 30% compared to traditional models. The model can provide a reference for metal structure design.