Fatigue Life of Components with Two Types of Defects

In design against fatigue with models that take defects into account, most attention is paid to the largest defects. Medium-sized defects, however, are seldom considered as potential sites of failure. In this paper, a model material is studied, containing a substantial proportion of medium-sized defects. The influence of their distributions has been investigated, using FCG computations. These computations were performed as post-processing of FE-results, using a modified Paris law. It is shown that the medium-sized defects can cause fatigue failure, given that there is a relatively large region of intermediate stresses. Further, it is shown that the statistical distributions used for describing the defects have a clear influence on the fatigue life of a component. The effects of removing the largest defects, or reducing the density of the defects, are studied as well.