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A viscoplastic constitutive theory for monolithic ceramics. 1

Journal Article · · Journal of Engineering for Gas Turbines and Power
DOI:https://doi.org/10.1115/1.2818069· OSTI ID:290095
 [1];  [2]
  1. NASA Lewis Research Center, Cleveland, OH (United States)
  2. Cleveland State Univ., OH (United States)
This paper, which is the first of two in a series,provides an overview of a viscoplastic constitutive model that accounts for time-dependent material deformation (e.g., creep, stress relaxation, etc.) in monolithic ceramics. Using continuum principles of engineering mechanics, the complete theory is derived from a scalar dissipative potential function first proposed by Robinson (1978), and later utilized by Duffy (1988). Derivations based on a flow potential function provide an assurance that the inelastic boundary value problem is well posed, and solutions obtained are unique. The specific formulation used here for the threshold function (a component of the flow potential function) was originally proposed by William and Warnke (1975) in order to formulate constitutive equations for time-independent classical plasticity behavior observed in cement and unreinforced concrete. Here constitutive equations formulated for the flow law (strain rate) and evolutionary law employs stress invariants to define the functional dependence on the Cauchy stress and a tensorial state variable. This particular formulation of the viscoplastic model exhibits a sensitivity to hydrostatic stress, and allows different behavior in tension and compression.
Sponsoring Organization:
USDOE
OSTI ID:
290095
Report Number(s):
CONF-960608--
Journal Information:
Journal of Engineering for Gas Turbines and Power, Journal Name: Journal of Engineering for Gas Turbines and Power Journal Issue: 1 Vol. 120; ISSN JETPEZ; ISSN 0742-4795
Country of Publication:
United States
Language:
English