Fatigue crack growth predictions based on damage accumulation calculations ahead of the crack tip

Models are proposed to predict the fatigue crack growth (FCG) process using crack initiation properties and critical damage concepts. The crack is modeled as a sharp notch with a very small but finite tip radius to remove its singularity, using a strain concentration rule. In this way, the damage caused by each load cycle and the effects of residual stresses can be calculated at each element ahead of the crack tip using the hysteresis loops caused by the loading, without the need for adjustable parameters. A computational algorithm is introduced to calculate cycle-by-cycle crack growth using the proposed methodology. A quite good agreement between the εN-based crack growth predictions and experiments is obtained both for constant and for variable amplitude load histories.