A fatigue limit evaluation method based on plastic strain incremental energy dissipation theory

Metallic materials frequently undergo fatigue failure during long-term service. Therefore, the study of fatigue performance detection methods with high precision and wide application ranges is crucial to reduce fatigue failures and accidents of materials and structures. In this study, a plastic strain incremental energy dissipation theory (PSIEDT) is established, and a general expression for fatigue limit is derived with the starting point of the plastic strain increment. Taking 42CrMo4 steel as an example, and its temperature and deformation fields are obtained synchronously using infrared thermal imaging and digital image correlation. Its fatigue limit is evaluated using the energy dissipation theory based on the plastic strain increment. The results show that the relative error between the fatigue limit measurement accuracies of the developed method and the method proposed by Luong is 1.64 %. The relative error of the fatigue limit obtained for the local damage region is only 0.18 %, which has a high measurement accuracy. At the microscopic level, the onset of plastic strain corresponds to a change in the microstructure of the material from reversible deformation (viscoelastic) to permanent deformation (plasticity). Therefore, the strain measurements have higher sensitivity than the temperature measurements. Considering the limited heat release of many materials, the new method has a wide application range, can rapidly obtain material fatigue properties, and has good engineering application prospects.