STP520

    Ductility Exhaustion Model for Prediction of Thermal Fatigue and Creep Interaction

    Published: Jan 1973


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    Abstract

    Extensive laboratory testing of typical alloys used in gas turbine blading has shown that there is a strong interaction of the thermal fatigue and creep damage modes which is nonlinear in nature. Consequently, a model for cumulative damage analysis was developed using an exhaustion of ductility concept in which the total available ductility is derived from baseline thermal fatigue tests or, alternatively, estimated from stress-rupture tests. A cycle-by-cycle reckoning of ductility used and remaining is made with the use of a digital computer program, and cracking is ultimately predicted at the point where the remaining ductility is insufficient to complete another cycle.

    The developed analysis is shown to correlate with laboratory test results. The understanding and design procedure developed make it possible to simulate complex service conditions in digital computer programs and evaluate designs and materials in simulated “fly offs.”

    Keywords:

    fatigue (materials), ductility, exhaustion, thermal fatigue, creep properties, damage, creep rupture strength, fatigue tests, failure


    Author Information:

    Polhemus, JF
    Assistant project engineer, project engineer, and assistant project engineer, Pratt & Whitney Aircraft, Division of United Aircraft Corp., East Hartford, Conn.

    Spaeth, CE
    Assistant project engineer, project engineer, and assistant project engineer, Pratt & Whitney Aircraft, Division of United Aircraft Corp., East Hartford, Conn.

    Vogel, WH
    Assistant project engineer, project engineer, and assistant project engineer, Pratt & Whitney Aircraft, Division of United Aircraft Corp., East Hartford, Conn.


    Paper ID: STP38874S

    Committee/Subcommittee: E08.05

    DOI: 10.1520/STP38874S


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