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TPE331/t76 Turboprop Propulsion Engine Durability

Report Number: AFWAL TR 82-4069
Author(s): Larry P. Wynn
Corporate Author: Garrett Turbine Engine Company
Date of Publication: 1982-08-01
Pages: 176
AD Number: ADA122962

Abstract:
This report on retirement-for-cause is based on the Garret TPE331/T76 turboprop engine second-stage turbine wheel. This second-stage turbine wheel is an integrally bladed wheel with continuous rim slots between each blade at the rim. The slot is ended with a circular hole. The slot and hole reduce thermal and centrifugal stresses existing at the heated outer rim and extend turbine low-cycle-fatigue life. This program was planned to develop criteria from examination and analysis of field service wheels that would allow the Air Force to define how much life remained in the wheel with an observed crack. The investigated wheel displayed significant scatter in cycles to initiate a given crack size. This scatter was traceable to the large variation in gran size at the rim of these cast integrally bladed wheels. Crack propagation analysis was able to predict the observed crack-growth rate. However, no correlation between crack initiation and usage could be identified during this program that would aid implementation of retirement-for-cause.

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