Evaluation of concepts to predict the endurance limit of P/M parts considering individual notch sensitivities

摘要

Structural parts made of P/M materials are increasingly used in lightweight construction for higher performances applications. Due to their low density they substitute wrought steel in automotive applications e.g. gears or synchronizer hubs. This raises the need for reliable fatigue design concepts.The authors have investigated and evaluated different concepts to predict the endurance limit of notched components based on a broad database including different steel-based P/M parts. The sensitivity to notches of PM materials is strongly depending on the chemical composition and the density, which makes it laborious to fit empirical models (e.g. stress gradient based) 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.