Paper Title
Two Energy-Based Damage Descriptions to Predict Fatigue Life of Steel Samples Subjected to Multiaxial Loading Spectra

Two energy-based models of Varvani-Farahani (VF) and Łagoda-Macha (LM) are employed to evaluated Fatigue life of different steel alloys subjected to irregular non proportional loading paths. The VF model assessed fatigue life through summation of both ranges of normal and shear energy on the critical plane. These ranges are determined from the largest stress and strain Mohr’s circles over the counted loading and unloading reversals. LM damage model evaluated the life of samples based on the equivalent strain energy densities over reversals of the applied stress and strain histories on the critical plane. The reversals over loading histories were counted by means of the equivalent relative strain method of the Wang-Brown. Damage values were calculated for each counted reversal and then accumulated based on the Miner-Palmgren linear damage rule. Fatigue life is calculated from the overall damage based on two damage models. As predicted lives based on these damage models compared with those of reported experimental data showed that estimated lives based on VF model have a better agreement. Index Terms - Critical plane criteria, Cycle counting, Fatigue Life prediction, Irregular nonproportional path.