A Method for Multiaxial Fatigue Life Prediction Using Energy Approaches

Fatigue criteria based on the concept of damage energy have been proposed and evaluated with experimental fatigue data generated under uniaxial as well as biaxial loading conditions. Most of the energy-based methods utilize plastic energy of stress-strain hysteresis loops as a correlating parameter. Limited success has been made in predicting fatigue life in the low-cycle fatigue range where the plastic energy of the hysteresis loops is well defined. However, is is difficult to estimate the plastic hysteresis energy in the high-cycle range where the stress-strain behavior is virtually elastic. Failure to adequately predict high-cycle fatigue life is an obvious shortcoming of the plastic energy-based method. A new method is proposed for multiaxial fatigue life prediction using strain energy as a correlating parameter which is physically associated with modes of fatigue fracture on a critical plane of the material that may be sensitive to either axial stress or shear at a given temperature. Biaxial fatigue data were analyzed for type 304 stainless steel and SAE 1045 steel subjected to in-phase and 90{degrees} out-of-phase tension/torsion loading at room and elevated temperatures. Comparisons were made between the experimental data and theoretical predictions to show the effectiveness to the new energy-based approach.