High cycle fatigue life assessment of notched components with induced compressive residual stress

A method for predicting the high cycle fatigue life of cyclically loaded components with induced residual stress based on standard S-N curve data, a fracture mechanics crack growth model, and Finite Element Analysis using the ANSYS SMART crack growth modelling tool is proposed. The method is appropriate to high cycle fatigue analysis of components in which the working stress cycle is linear elastic and the conditions required by LEFM and the SMART FEA method are satisfied. The total fatigue life of the component is calculated as the sum of the crack initiation life and crack propagation life. Crack initiation life is evaluated for an assumed initiation crack length by reference to an S-Ni curve relating stress amplitude to number of cycles to crack initiation, generated from standard S-N data and application of SMART FEA to determine the crack growth component of total test specimen life. Crack propagation life is evaluated by superposition of the individual applied load and residual stress fields, where variation in stress intensity factor with increasing crack length is obtained in the form of polynomial equations. Numerical and experimental investigation of double-notch 316L stainless steel tensile specimens show that the proposed method gives an improved estimate of fatigue life when compared to standard stress-life fatigue assessment for specimens both with and without induced compressive residual stress.