Accession Number : ADA136956

Title :   Evaluation of Fatigue-Creep Crack Growth in an Engine Alloy.

Descriptive Note : Master's thesis,

Corporate Author : AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OH SCHOOL OF ENGINEERING

Personal Author(s) : Christoff,J R

PDF Url : ADA136956

Report Date : Dec 1983

Pagination or Media Count : 80

Abstract : This study investigates fatigue-creep interaction effects in alloys and evaluates the effectiveness of predictive models currently in use by the aircraft engine industry. The state-of-the-art crack growth rate prediction models are supplied by the General Electric Company (MSE) model, and the Pratt and Whitney Aircraft Group (SINH) model. They are used to predict crack growth rates under a range of conditions which involve fatigue-creep interactions. Another aspect of this study involves the development of an empirical model to predict fatigue-creep crack growth based on creep crack growth rate data and knowledge of the loading wave-form. This study is primarily directed toward high temperature ( or = 1000 F) fatigue-creep interaction at low test frequencies and positive stress ratios. The SINH model proves to be more accurate than the MSE model in predicting crack growth rates for the data analyzed. Both models predict linear relationships for the variations of crack growth rates for the MSE model in predicting crack growth rates for the data analyzed. Both models predict linear relationships for the variation of crack growth rates (da/dN) with the length of hold-time or the frequency rate on logrithmic coordinates.

Descriptors :   *Alloys, *Aircraft engines, *Fatigue(Mechanics), Crack propagation, Creep, Growth(General), Rates, Loads(Forces), Models, Predictions

Subject Categories : Metallurgy and Metallography
      Mechanics
      Jet and Gas Turbine Engines

Distribution Statement : APPROVED FOR PUBLIC RELEASE