The Superposition of Stress Concentration Factors

Abstract

A photoelastic study was made of the superposition of stress raising notches. Recent investigations [1, 2] have indicated that where one stress raising notch is placed in the region of maximum influence of a second notch the resulting stress concentration factor may be determined by taking the product of the concentration factors for the individual notches. Test results presented gave general although not precise agreement with this method of combination. The tests of reference [1] were performed on specific materials for static and repeated loads, and hence combine the effects of stress concentration with the sensitivity of the particular material. The tests of reference [2] run on a brittle material indicate the same general agreement. Normal practice for applying stress concentration factors separates the two effects, i.e., the actual concentration of stress and the sensitivity of the material to such concentration. It was believed that photoelasticity might yield a better verification of the method for combining superposed stresses as photoelastic methods have shown close agreement with theoretical factors of stress concentration. Results of the present investigation indicate that the product gives the combined concentration factor with the same degree of accuracy to which the individual factors are known. A mathematical analysis was made to determine the stresses across the section.