Prediction Of Low-cycle Fatigue Life Base On Plastic Strain Energy-tention Stress Coupling Model

In engineering practice, many components are working under a complicated multiaxial low cycle fatigue loading, due to the complexity of multiaxial low cycle fatigue. At present, the research of multiaxial low cycle fatigue is still immature. Thus, the further research on the method of life prediction for multiaxial low cycle fatigue has not only the important significance, but also a practical value. The method of the combination of theoretical research and the finite element numerical calculation is adopted and the mechanism of fatigue failure is analyzed. Based on the latest strain energy theory, a new kind of plastic strain energy of multiaxial low cycle fatigue life prediction model is proposed. In this paper, the main contents are as follows:1. The relevant theories of multiaxial low cycle fatigue life prediction are reviewed, and the advantages and disadvantages of various kinds of theory are summarized.2. The finite element numerical analysis method is introduced into fatigue analysis, which solves the difficulties in obtaining the history of stress and strain response under complex loading conditions.3. According to the analysis of the plastic deformation mechanism, a micro crack initiation condition is put forward in the form of snap. Based on the new plastic strain energy of multiaxial low cycle fatigue life prediction model, the first principal stress is introduced. This shows the effects of multiaxis and nonproportional and makes the fatigue life prediction formula with clear physical meaning.4. Using relevant data extracted from finite element numerical analysis to predict the life of GH4169alloy、SAE1045 steel and S460 N steel, which verifies the validity of the model, and the comparism with the F-S model and S-W-T model is made. It’s noticed that the model is capable of making an accurate prediction for low cycle fatigue under proportional and non-proportional loading such complex loading conditions. It also has great scope for multiaxial loading paths and the kind of material, and the calculation of the related parameters of the model is easier compared to the method of critical plane, which is more conducive to engineering application.