STP1371: Thermal Strain Fatigue Modeling of a Matrix Alloy for a Metal Matrix Composite

    Halford, GR
    Senior scientific technologist and research engineer, Lewis Research Center, NASA, Cleveland, OH

    Lerch, BA
    Senior scientific technologist and research engineer, Lewis Research Center, NASA, Cleveland, OH

    Arya, VK
    Research Professor, University of Akron, Akron, OH

    Pages: 18    Published: Jan 2000


    Abstract

    The Total Strain Version of the method of Strainrange Partitioning was used as the basis for modeling the thermomechanical fatigue resistance of the matrix material of the metal matrix composite, SCS-6/Ti-15-3. As prescribed by the model, the resistance was assessed through the use of bithermal creep-fatigue experiments. Bithermal temperatures of 205 and 427°C were imposed. A minimal number of strain limit-controlled, in-phase PP (pure fatigue, no creep) and CP (tensile creep) as well as out-of-phase PP (pure fatigue, no creep) and PC (compressive creep) experiments were conducted on conventional, axially-loaded, cylindrical-bar specimens. Inelastic strain range versus cyclic life curves for each of the Strainrange Partitioning bithermal cycles were evaluated and found to be nominally coincident. Cyclic elastic strain range versus inelastic strain range curves as well as elastic strain range versus life curves were documented for pure-fatigue and creep-fatigue conditions. The time-dependencies of these relationships were calibrated with the available data. These results enable the construction of total strain range versus fatigue life curves for thermomechanical fatigue for in- and out-of-phasing and for any arbitrary creep-time per cycle. Results are pplicable to the cyclic life prediction of metal matrix composites using the Ti-15-3 matrix material.

    Keywords:

    metal matrix composites, fatigue (metal), thermal fatigue, thermomechanical fatigue, bithermal fatigue, low cycle fatigue, high temperature fatigue, creep fatigue, life prediction, strainrange partitioning, crack initiation, thermal expansion


    Paper ID: STP15261S

    Committee/Subcommittee: E08.09

    DOI: 10.1520/STP15261S


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