A continuous low cycle fatigue damage model and its application in engineering materials

In this study, the low cycle fatigue (LCF) damage evolution of the engineering materials is studied by use of continuum damage mechanics (CDM) theory. Based on thermodynamics, on a continuum damage variable, D, and on the effective stress concept, a continuum damage model of isotropic LCF is derived and is used to analyze the strain-controlled LCF damage evolution of steam turbine blade material 2Cr13 steel. The damage variable D = 1 - Δσ/Δσ0 is selected and measured during strain-controlled LCF tests to verify the model, which is in good agreement with the results. The parameters in the model have clear physical meaning and can easily be determined. The evolution of microstructure during fatigue is observed by transmission electron microscopy, which gives the microscopic explanation for LCF damage evolution law of 2Cr13 steel.