Energy-based low cycle fatigue analysis of low yield point steels

As examples of the new advanced high-performance structural steels, low yield point steels have attracted increasing interest owing to their excellent properties in the technology of energy dissipation and seismic design. Because dynamic cyclic loading is inevitable during service life in engineering applications, it is critical to develop in-depth understanding of the fatigue behavior of this material. Here, the low cycle fatigue behavior of low yield point steels produced in China, namely LY100, LY160, and LY225, is investigated using an energy-based approach. Axial steel coupons are tested by fully reversed and push-pull cyclic loading with a nominal strain ratio R = −1 at a constant strain rate of 0.1% S−1. The strain amplitudes range from 0.5% to 6.0% in 0.5% increments. First, experimental details and results of fatigue life are introduced. Subsequently, using an energy-based approach, the cyclic plastic strain energy, cyclic hysteresis loop properties, and fatigue life prediction are thoroughly analyzed. Finally, a simplified method for fatigue life prediction is proposed. The results show that plastic strain energy density is an important parameter for predicting the low cycle fatigue life of low yield point steels with an acceptable degree of accuracy. The proposed simplified method can provide an effective and reliable alternative for low cycle fatigue life prediction of low yield point steels.