STP1450: Extension of a Microstructure-Based Fatigue Crack Growth Model for Predicting Fatigue Life Variability

    Enright, MP
    Senior Research Engineer and Institute Scientist, Southwest Research Institute, San Antonio, TX

    Chan, KS
    Senior Research Engineer and Institute Scientist, Southwest Research Institute, San Antonio, TX

    Pages: 17    Published: Jan 2004


    Abstract

    Most of the existing crack growth models rely on empirical constants derived from curve fits of data at specific test conditions. Although statistical information can be obtained for many of these constants, multiple experimental tests typically must be performed to represent the wide range of the response. In this paper, an alternative approach is presented that links fatigue crack growth parameters to material and microstructural size parameters via a microstructure-based fatigue crack growth (FCG) model. In addition, variation of initial crack size due to microstructural variation is modeled in terms of a crack-size-based fatigue crack initiation model. Variations of microstructural parameters are described in terms of a probabilistic framework. The probabilistic, microstructure-based, FCG approach is illustrated for a Ni-based superalloy in which the influence of changes in the main descriptors of the individual microstructural parameters on initial crack size, crack growth rate, and fatigue life is shown. Stochastic model results are compared with existing experimental data to illustrate the feasibility of the approach for predicting da/dN variability due to microstructure variations.

    Keywords:

    fatigue life variability, microstructure variations, fatigue crack growth, fatigue crack initiation, micromechanics, nickel-based alloys, probabilistic methods


    Paper ID: STP11281S

    Committee/Subcommittee: E08.05

    DOI: 10.1520/STP11281S


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