Local stress at the root of threads

Abstract

The paper presents improvement of the analytical method intended for calculation of the local stress at the root of threads. That includes the analytical expressions obtained here for the Heywood’s formula parameters which are used through calculation of the turn’s load contribution to the local stress. The contribution of the axial tension of the bolt core is expressed by series, factors of which are determined by using Otaki’s numerical values of the ISO thread profile coefficients. Proposed methodology allows primarily to find the location of the maximum stress and further its value for the helical bolt root in the case of the full profile turns engagement as well as in the case of runout.