Fatigue life prediction of scratch damaged shot peened components

Abstract

Purpose -This paper aims to present a methodology, based on traditional approaches, to predict the fatigue life and non-propagating cracks of shot peened components and the damaging effect of a scratch created over the treated surface. Design/methodology/approach -The finite element method is used to determine the actual strain at surface and fracture mechanics parameters calculated from cracks at the surface. The model considers residual stress (in order to introduce the effect of shot peening) and the scratch geometry. The total fatigue life is obtained by adding initiation life, to early and long crack propagation life using appropriate criteria. Findings -Numerical predictions were compared with previous experimental tests, showing that this method is quite reliable for predicting both fatigue life and non-propagating cracks of shot peened components, including the effect of damage due to a scratch. Research limitations/implications -The proposed method provides good results and a clear understanding of the fatigue process, however it requires a considerable amount of both material and shot peening parameters. Practical implications -The methodology presented in this paper allows the determination of fatigue life and the prediction of non-propagating cracks for components, including the effects of shot peening and scratch damage. These results can be used to quantify the scratch damage limits of components improved by shot peening. Originality/value -This paper provides a useful tool for prediction of the effects of shot peening and scratch damage on fatigue life, using traditional approaches.

Low cycle fatigue life prediction in shot‐peened components of different geometries – part II: life prediction

“…, the actual local strain range (Δ ε xx ) cannot uniquely characterise the fatigue life data for conditions with different surface treatments and geometries, even when the effects of compressive residual stresses and strain hardening are taken into account. This is thought to be a result of the mean stress level or the stress/strain ratios within the surface layer during fatigue loading being changed by shot peening, compared with the unpeened condition . Consequently, in order to predict the fatigue life of shot‐peened components using total life approaches, a damage parameter applying to situations with varying loading amplitudes and mean stress levels should be selected instead of the local strain range.…”