Finite Element Analysis of the Roller Burnishing Process for Fatigue Resistance Increase of Engine Components

Abstract

Highly stressed components of modern aircraft engines, like turbine and compressor blades, have to satisfy stringent requirements regarding durability and reliability. The induction of compressive residual stresses and strain hardening in the surface layer of these components have been proved to be a very promising method to increase their fatigue resistance significantly. Previous research has shown that an improvement of these characteristics can lead to a slow-down of crack propagation or even complete crack closure due to shakedown effects. The required surface layer properties can be achieved by a number of different manufacturing processes, among which roller burnishing is distinguished by the following substantial advantages: high and deep-reaching compressive residual stresses, high strain hardening, and excellent surface quality. The determination of optimal process parameters in order to achieve a defined state of the surface layer still requires an elaborate experimental set-up and subsequent time-consuming and cost-extensive measurements. Therefore, in this article a novel approach for the quantitative prediction of the induced residual stresses by the roller burnishing process is proposed using finite element analysis (FEA). The developed FE models were verified by comparison of the calculated residual stress state with experimental results of roller burnishing tests for different process parameters and materials. The influence of the induced compressive residual stresses and strain hardening on the materials’ fatigue behaviour was examined subsequently using low cycle fatigue (LCF) tests.