A modification of Shang-Wang fatigue damage parameter to account for additional hardening

Based on the critical plane approach, the Shang-Wang fatigue damage parameter is analyzed. It is discovered that the effect of the additional cyclic hardening on fatigue life cannot be reflected by the normal strain excursion well. In order to solve this problem, this fatigue damage parameter is modified by using the Huber-Mises criterion. The modified damage parameter combined maximum shear strain range with normal strain range on the critical plane, and a new stress-correlated factor is introduced to account for the additional cyclic hardening. It is demonstrated that the modified criterion gives satisfactory results for all the six checked materials.