A procedure proposed in this paper is intended to facilitate better assessment of creep and fatigue life for gas turbine components under varying high temperatures and stresses. The remaining life of a component depends highly on its operating conditions, which can vary significantly with time and from engine to engine due to usage and ambient conditions. This creates two major problems when trying to capture these variations in a life assessment analysis: (1) an analysis of life with constant operating conditions is very time consuming and costly, (2) the variations themselves are difficult to predict. These problems limit the ability to do life assessments using deterministic methods, and, as a result, the prediction of usable life of a component tends to be much lower than it should be. In this paper, Design of Experiments is used in conjunction with the Response Surface Method in order to approximate the analysis. The combination of these methods provides a fast and relatively accurate way to create a physics-based model. This facilitates dealing with the first problem. The extrapolation of future operating conditions and damage accumulation addresses the second problem, because the probabilistic method makes possible an online, real-time life assessment based on the historical operating profile of the component. Thus, the final product can be more accurate than results from a traditional deterministic approach. In addition to studying varying operating conditions, variations in geometry and material properties are investigated as well. These variations are more significant in design or disposition, but they still can be important in assessing the service life. Specifically, creep is chosen to illustrate the methodology, because it is one of the major failure mechanisms for gas turbine components under high temperature and stress. It is expected that the method can be extended to assess fatigue-creep life.
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