Combined Fatigue Stress Concentration Factor Determination

Abstract

The paper begins with a panoramic view of the state of the art embracing the spectrum of methods employed by different designers to account for all stress concentration effects in calculations for use in the design of machine elements and components subjected to combined/fatigue loadings. Then, on the basis of the widely accepted von Mises-Goodman approach, and the method deemed the best for incorporating combined stress concentration effects, a general expression is derived for the combined fatigue stress concentration factor which is applicable to any machine element or component subjected to any combination of fatigue loadings. Various load combinations are considered not only to illustrate the use of the derived expression, but also to demonstrate other methods which may lead to calculations which are incorrect depending upon the nature and magnitude of the parameters involved. The specific machine component, that of a stepped shaft subjected to combined fatigue loadings, is selected for particular, detailed and further demonstration. Demonstrative tables and a curve plot are also included.