Effects of micro-stresses from machining and shot-peening processes on fatigue life

An investigation of the effects of tensile machining and compressive shot-peening residual stresses on fatigue life is presented. The paper is focused on fatigue life modelling using the finite element method (FEM). A representative broached notched specimen under three-point bending is modelled as a 2D plane stress geometry using the FEM. Inconel 718 mechanical and fatigue material properties at 600°C are used. Machining and shot-peening residual stresses are mapped to the macro FE models using mathematical algorithms around the notched area of the specimen and their influence on the fatigue life experiencing high cycle fatigue (HCF) and low cycle fatigue (LCF) is investigated. The results show that the compressive shot-peening residual stresses significantly increase the life at HCF compared to the LCF.