Reliability Study and Life Estimation of a Centrifugal Impeller, Under Multiaxial Variable Amplitude Loading

Abstract

An application level study of multiaxial variable amplitude loading condition is presented here, by taking centrifugal impeller used in a gas turbine engine as the model for the study. Algorithms proposed by Bannantine and Socie (BS) and Wang and Brown (WB) were used for counting the damage cycles resulting from the service loading conditions. To estimate the damage parameter and fatigue damage, multiaxial fatigue damage models proposed by Fatemi and Socie (FS) and Smith–Watson–Topper (SWT) were used. The theoretical results were validated through a reliability study using Weibull models. Field data for this study were collected from 18 centrifugal impeller sets removed from different gas turbine engines that were brought to the shop for inspection. The reliabilities of life estimated by the FS model using algorithms proposed by BS and WB were found to fall within 80 and 82%, respectively. The SWT model estimated the life of the centrifugal impeller with reliabilities of 98 and 98.5% using the same algorithms. Appreciable differences in fatigue life were not observed for this application when algorithms proposed by BS or WB were used to count the damage cycles.