Relation between characyeristics of low-cycle and high-cycle fatigue of threaded parts and residual stresses

The dependence of low-cycle and high-cycle fatigue characteristics of threaded parts on the criterion of average integral residual stresses is examined in the article. These characteristics play an essential role in ensuring reliability of aeronautical equipment. The study was carried out using titanium-alloy M6 bolts with various ways of producing residual stresses. In all the cases the dependences are quadratic. Further analysis showed linear dependence between the increment of cycle life and the limiting cycle amplitude under changes of residual stresses. This conclusion holds for all examined ways of producing residual stresses. The increments mentioned are linear functions of the criterion of average integral residual stresses. A procedure for determining the increment of the limiting cycle amplitude with the use of the criterion of average integral stresses is presented. Special attention is given to the method of finding the coefficient of residual stress influence on the limiting cycle amplitude for the constant mean stress. The approach to determining the increment of cycle life by a known value of the increment of the limiting cycle amplitude calculated with the use of the criterion of average integral residual stresses is validated.