A new cumulative fatigue damage model under biaxial loading

Criteria of fatigue damage play a key role in life prediction of structures subjected to random loadings. In previous works, a cumulative damage model called damage stress model was developed. This model takes into account not only the loading history but also the nonlinear evolution of damage. Damage stress model improved its predictive capability of fatigue life for several materials such as steels and aluminum alloys. In this paper, a new approach of cumulative damage, based upon the damage stress model parameter, is investigated for different loading paths under finite life regime. To build the new damage indicator, the damage stress model parameter is coupled with an equivalent stress formulated via Sines, Dang Van and Robert fatigue criteria, respectively. The relevance of the proposed model is examined using series of biaxial tests performed on cruciform specimens made of an aluminum alloy. Several types of loadings composed of constant amplitude fatigue, cumulative fatigue with two/three blocks and repeated blocks were set up. Good agreement is highlighted when the prediction, obtained with the proposed model, is compared to our experimental data.