An Improved Anisotropic Tertiary Creep Damage Formulation

    Authors

    C. M. Stewart; A. P. Gordon; Y. W. Ma;R. W. Neu

    Comments

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    Abbreviated Journal Title

    J. Press. Vessel Technol.-Trans. ASME

    Keywords

    transversely isotropic; continuum damage mechanics (CDM); directionally; solidified; Ni-base superalloy; void induced anisotropy; multiaxial; THERMODYNAMICAL MODEL; RUPTURE; MECHANICS; ELASTICITY; STRESS; GROWTH; COPPER; STATES; Engineering, Mechanical

    Abstract

    Directionally solidified (DS) Ni-base superalloys are commonly used as gas turbine materials to primarily extend the operational lives of components under high load and temperature. The nature of DS superalloy grain structure facilitates an elongated grain orientation, which exhibits enhanced impact strength, high temperature creep and fatigue resistance, and improved corrosion resistance compared with off-axis orientations. Of concern to turbine designers are the effects of cyclic fatigue, thermal gradients, and potential stress concentrations when dealing with orientation-dependent materials. When coupled with a creep environment, accurate prediction of crack initiation and propagation becomes highly dependent on the quality of the constitutive damage model implemented. This paper describes the development of an improved anisotropic tertiary creep damage model implemented in a general-purpose finite element analysis software. The creep damage formulation is a tensorial extension of a variation in the Kachanov-Rabotnov isotropic tertiary creep damage formulation. The net/effective stress arises from the use of the Rabotnov second-rank symmetric damage tensor. The Hill anisotropic behavior analogy is used to model secondary creep and tertiary creep damage behaviors. Using available experimental data for a directionally solidified Ni-base superalloy, the improved formulation is found to accurately model intermediate oriented specimen. [DOI: 10.1115/1.4002497]

    Journal Title

    Journal of Pressure Vessel Technology-Transactions of the Asme

    Volume

    133

    Issue/Number

    5

    Publication Date

    1-1-2011

    Document Type

    Article

    Language

    English

    First Page

    10

    WOS Identifier

    WOS:000294254500001

    ISSN

    0094-9930

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