Concepts to estimate the endurance limit of notched parts – A statistical evaluation using a broad database for P/M steels

Structural parts made of P/M (powder metallurgy) materials are increasingly used in lightweight construction for high performance applications. Due to their low density, they substitute for wrought steel in automotive applications e.g. gears or synchronizer hubs. This raises the need for reliable fatigue design concepts. Different concepts to estimate the endurance limit of notched components have been examined and statistically evaluated based on a broad database of various steel-based P/M materials. The sensitivity to notches of P/M materials is highly dependent on the chemical composition and the density, which makes it difficult to fit empirical models for different P/M materials. El Haddad’s fictitious crack length proves to be a good parameter to account for this dependency. Using the theory of critical distances, the fatigue properties of a material can be transferred to parts effectively and with low scatter.

► Support factor concepts for P/M parts are compared and evaluated.
► A broad database of 153 experimental support factors is considered.
► The Theory of critical distances shows the best results.