Meso/micro fatigue crack growth involving crystal structure and crack geometry: the effect of crystal structure, crack geometry, stress ratio and component scale

Prediction of the S-N curve in engineering alloys leads to significant overestimation of fatigue life. Short cracks have been held responsible since they propagate faster than longer cracks under the same stress intensity factor conditions. Inasmuch, plastic flow resistance is equated to a deterministic value corresponding to material bulk properties. However, a crack will “favour” specific paths to propagate in order to ease yielding. In terms of crack plasticity the average grain size (in the plastic zone) would exhibit values larger than (tend towards) bulk material given advanced crack growth (greater number of grains). This signifies transition from meso to macro scale. Herein, the slip-mismatch effect is modelled and stress intensification factors are computed. We conclude that using the difference between probabilistic and deterministic values can estimate crack growth rates' uncertainty.