CALCULATION METHOD FOR THE FATIGUE LIMIT OF PARTS OF CASE-HARDENED STEELS

Based on the weakest link concept a method is developed, from which th e survival probability of every surface and volume element of a case h ardened part, which is loaded near the fatigue limit, can be calculate d. Prerequisite of the calculation is the knowledge of the hardness an d residual stress distribution, the surface roughness, and the surface oxidation depth. By multiplication of the survival probabilities of n eighboured elements the survival probability of a limited region or of the whole part can be calculated, which includes a fatigue limit dete rmination. It is shown, that this method can be applied successfully t o unnotched specimens of case hardened steels. The necessary calculati on parameters can be gained from a set of reference parts. Because of the possibility to formulate a survival probability for every volume a nd surface element, there are no geometrical restrictions to the parts which shall be calculated. (C) 1997 Elsevier Science S.A.