Probabilistic Analysis on Turbine Disk Under LCF-Creep

Abstract

This paper establishes a structural model of the turbine disk of a certain aero-engine subjected to loads due to centrifugal force and duration at elevated temperature, and calculates the plastic and creep deformation with finite element (FE) analysis software. During creep analysis, the Norton constitutive equation was taken into account. After the temperature field distribution of the turbine disk had been obtained, structural static analysis results showed that the maximum equivalent stress and strain appeared at the area near to the disk center, which was taken as the critical point. The Manson-Coffin formula was used to predict low cycle fatigue (LCF) life based on the calculations derived from cyclic plastic-creep analysis, and creep life was obtained by applying the Larson-Miller equation. Lognormal distributions of LCF life and creep life were used as pointed out in the literature, which mainly considered the uncertainties in material parameters. Taking the lives and loads as random variables including LCF life, creep life, fatigue load and hold time, a probabilistic analysis on the turbine disk was performed under LCF-Creep, in which a failure function was proposed based on linear cumulative damage rule (LCDR). The probabilistic method of response surface (RS) was applied to fit the regression model of the LCF-Creep life with a quadratic approximation function including cross-terms. The Monte Carlo Simulation sampling technique was employed to carry out probabilistic analysis on the turbine disk life, resulting in the conclusion that the life of turbine disk under LCF-Creep follows a lognormal distribution. Furthermore, the effect of different random variables on the disk life was investigated through sensitivity analysis in order to increase the component’s life and improve its reliability. However, studies on the distributions of loads and damage theory of the component under LCF-Creep still need to be discussed in future study.