Modelling attemps to predict fretting fatigue life in turbine components
Abstract
Wherever two or more turbine components are in tight contact, Fretting-Fatigue becomes a relevant failure mechanism. Despite of on-going research on Fretting Fatigue, life prediction under fretting conditions continues being a challenge. To analytically predict fretting-fatigue life, key driving factors need to be identified and quantified in mechanical terms (stress and strain). Due to the intrinsic characteristics of contact, stress and strain fields around contact areas evolve with the loading history. They, together with material non-linearity and contact conditions need to be taken into account in order to perform a reliable life prediction. The present paper focuses on identifying the driving factors for fretting damage on blade-disk attachment under real engine conditions. Two-dimensional finite element contact calculations were carried out to quantify the influence of the key factors on mechanical quantities (stress and strain). Special attention was paid to material models and surface interaction (friction coefficient and contact conditions) in order to balance computational effort with result’s accuracy. Finally, the multi-axial fatigue criteria developed by Dang Van and co-workers is used to predict failure. For validation purposes life prediction is compared with experimental results.
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