Calculation method for the fatigue limit of parts of case hardened steels

Based on the weakest link concept a method is developed, from which the survival probability of every surface and volume element of a case hardened part, which is loaded near the fatigue limit, can be calculated. Prerequisite of the calculation is the knowledge of the hardness and residual stress distribution, the surface roughness, and the surface oxidation depth. By multiplication of the survival probabilities of neighboured elements the survival probability of a limited region or of the whole part can be calculated, which includes a fatigue limit determination. It is shown, that this method can be applied successfully to unnotched specimens of case hardened steels. The necessary calculation parameters can be gained from a set of reference parts. Because of the possibility to formulate a survival probability for every volume and surface element, there are no geometrical restrictions to the parts which shall be calculated.