Two Fatigue Damage Models to Predict Life in SS304 and Al7050 Alloys undergoing Multiaxial Irregular Loading Spectra

Fatigue life of SS304 and Al 7050-T7451 alloys subjected to variable multiaxial loading spectra was evaluated by means of two energy-based models of (i) Ellyin and (ii) Varvani-Farahani. Total strain energy density per cycle in the Ellyin model including elastic and plastic strain energies evaluated fatigue life data by using areas within the axial and shear stress-strain hysteresis loops. The Varvani model assessed fatigue lives based on the integration of the normal and shear energy ranges calculated on the critical plane which was determined through the largest stress and strain Mohr’s circles. Wang-Brown multiaxial cycle counting method was employed to count the reversals over variable multiaxial loading spectra. The assessment of fatigue lives based on the Ellyin, and Varvani damage models showed good correlations with experimentally obtained life data.