The influence of defects on high cycle fatigue of metallic materials

Structural ceramics are known to be particularly sensitive to singular defects such as inclusions, secondary pores, pore clusters, etc. Within this work, it is shown that similar behavior can be found also with high strength/low ductility metallic materials in the case of high cycle fatigue loading. Various types of such defects are described in different metallic materials, those produced by powder metallurgy being particularly suited for these investigations. It is shown that the influence of the singular defects can be described by a modified Kitagawa diagram based on the fatigue limit of the defect-free material and the threshold stress intensity factor. Realistic predictions are however only possible if both the stress field around the defects and possible interaction between adjacent defects are taken into account.