Multiaxial fatigue behavior of a 2198-T8 Al-Li alloy under proportional and nonproportional loading

2198-T8 Al-Li alloy was examined under different loading path. Uniaxial and multiaxial proportional and nonproportional loading tests were conducted to determine the material fatigue constant, and to study the multiaxial fatigue behavior, respectively. The multiaxial fatigue life was estimated by various criteria. The results show that, the torsional fatigue performance is better than the tension-compression fatigue performance. The fatigue life of nonproportional loading increases firstly and then decreases with the increase of phase difference from 0 degrees to 90 degrees. Shear Findley model and SWT model were modified by introducing shear damage parameters. The modified models provide fine results which are all within a factor of two.