Probabilistic High Cycle Fatigue Analysis of Turbine Engine Components

Abstract

This paper presents the three step approach to computing the probability of high cycle fatigue in turbine engine components that has been implemented in the ProFES probabilistic finite element software. The first step is to develop a probabilistic Campbell Diagram for mode interaction screening. The probabilistic diagram is developed considering uncertainties in material properties, boundary conditions, geometry, and operating conditions. This approach is an improvement over the deterministic approach as the closeness of a mode to an operating frequency can be measured in a probabilistic sense and gives engineers the capability to answer questions of the type, “What is the probability that modes interact within 5Hz over the lifetime of the engine.” The second step is to perform a probabilistic dynamic analysis. This step is done for interactions that are deemed critical from the step one analysis. The actual structural response is determined and the probability of exceeding a critical level is determined. The third step applies a cumulative damage model to the stress distributions from step two to find the fatigue failure probability. This step is applied for modes that are found to be critical in the step two analysis. The complete process is automated using the ProFES probabilistic finite element software which allows pre and post processing of the FEM model to be integrated into one probabilistic analysis.