Fatigue crack propagation behaviour of rotor and wheel materials used in steam turbines |
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Authors: | C Poon D Vitale M Singh D Hoeppner |
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Affiliation: | 1. Dr Poon and Professor Hoeppner are with the Department of Mechanical Engineering, University of Toronto, Canada;2. Mr Vitale and Mr Singh are both with the Turbodyne Corporation of Wellsville, NJ, USA |
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Abstract: | The fatigue crack propagation characteristics of several rotor and wheel materials that are commonly used in rotating components of steam turbines were investigated. Particular emphasis was placed on the behaviour at near-threshold growth rates, ie below 10?5 mm/cycle, approaching the fatigue-crack propagation threshold, . The lifetimes of the cracks of interest lie mostly in this region, and it is also the region where few data are available.The effects of load ratio on the fatigue crack growth rates were examined, as well as the tensile, Charpy V-notch and fracture toughness properties of the rotor and wheel materials. The relationship between fatigue crack propagation behaviour and fractographic features was examined. Fatigue crack growth rate data, vs stress intesity range , were fitted with a four parameter Weibull survivorship function. This curve fitting can be used for life estimation and establishment of . The results show that load ratio and microstructure play a role in determining the fatigue crack threshold and fatigue crack growth behaviour. |
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Keywords: | fatigue fatigue crack growth fatigue thresholds microstructure alloy steels |
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