Optimal shot peening residual stress profile for fatigue

S Aguado-Montero,J Vázquez,C Navarro,J Domínguez

doi:10.1016/j.tafmec.2021.103109

S Aguado-Montero, J Vázquez + Show 2 more

Open Access

https://doi.org/10.1016/j.tafmec.2021.103109

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Abstract

Shot peening (SP) is frequently used as a palliative measure against metal fatigue in many engineering components. The performance of this surface treatment depends on different factors including the material, shape and loading conditions of the component, as well as process parameters. Fatigue improvement due to SP depends to a great extent upon the in-depth compressive residual stress profile produced in the specimen.In this work, we study the optimum shape for a residual stress profile in terms of fatigue behaviour. For this task, we assume a residual stress profile that is qualitatively similar to that produced by SP in many metals. Based on this generic profile, we analyse the optimum shape for two simple, but noteworthy, fatigue cases: plain fatigue and notch fatigue. The analysis is conducted in the “fatigue damage tolerance design” framework, in which a certain initial defect is assumed to be present in the component under study.

Highlights

Fatigue is a material damage phenomenon that is present in many engineered metallic components
It occurs when components are subjected to time-fluctuating loads, and its most recognizable effect is the appearance of cracks, which, under suitable conditions, can propagate until the complete fracture of the component, causing catastrophic failure in some cases
We consider a situation where a previously generated defect is present in the specimen’s domain. This condition can represent some type of manufacturing imperfection as the ones found in metal welding or additive manufacturing. This already existing defect can act as a crack whose initiation life can be neglected, considering that it will start propagating right away, resulting in fatigue crack growth life of this specimen being equal to its complete fatigue life since the defect already exists and no crack initiation life needs to be taken into account

Summary

Introduction

Fatigue is a material damage phenomenon that is present in many engineered metallic components. This condition can represent some type of manufacturing imperfection as the ones found in metal welding or additive manufacturing This already existing defect can act as a crack whose initiation life can be neglected, considering that it will start propagating right away, resulting in fatigue crack growth life of this specimen being equal to its complete fatigue life since the defect already exists and no crack initiation life needs to be taken into account. Assuming that the shape of the shot peening induced residual stress profile can be properly described with a sinusoidal decay function, a new set of more comprehensive parameters is first proposed, and a nondimensional analysis is developed for the problem In this way, we try to obtain the optimum value for the parameters governing the sinusoidal decay function, maximizing the component’s fatigue strength. The crack growth life spent in region III is very small as compared to that in zones I and II, and the integration of the Paris crack growth law over zones I, II and III may be reasonable in many situations

Mathematical modelling of a residual stress profile

Optimization criteria

Plain fatigue

Notch fatigue

Conclusions