Damage-based modification for fatigue life prediction under non-proportional loadings

• A new fatigue damage parameter is proposed.
• The proposed model is more accurate than SWT for all studied materials.
• Two damage-based modifications are studied in this work for fatigue life prediction under non-proportional loadings.
• The recommended damage modification could effectively decrease the error of fatigue life prediction.

This paper proposes a new fatigue model based on virtual strain energy to predict fatigue life under both proportional and non-proportional loadings for different materials including, 1045 Steel, 30CrNiMo8HH, Titanium TC4, and AZ31B magnesium. The results were strongly correlated with experimental results available in the literature. In addition, two damage-based modifications for fatigue life prediction under non-proportional loadings are studied. These modifications are then applied to the fatigue parameters including Smith–Watson–Topper, Fatemi–Socie, maximum shear strain, and the proposed parameter for fatigue life predictions of the studied materials. The results show considering these modifications significantly improves the accuracy of the models.