Experimental and numerical investigation of the effects of shot peening on low-cycle fatigue behaviour of notched geometries

Abstract

In service, turbine components are subjected to low-cycle fatigue (LCF) during start-up and shut-down operations, especially at the fir tree root blade-disc connection which has a complex geometry and corresponding high stress concentration. Shot peening generates compressive residual stress (CRS) and strain hardening which can improve fatigue life. However, prediction of the fatigue life of shot-peened components under LCF is challenging due to the complex interaction between the shot peening induced effects and service conditions, especially in regions of high stress concentration. The current study aims to develop a validated 3-D eigenstrain-based modelling tool, which is capable of simulating the stress/strain evolution under LCF in shot-peened notched samples representative of the real turbine blade fir tree geometry. The residual stress and strain hardening profiles caused by shot peening were first evaluated by experiments and then incorporated into the finite element (FE) model separately. In addition, the Smith – Watson – Topper (SWT) method was used to predict the fatigue life of shot peened samples, based on the stress/strain data generated using the developed FE model