A Viscoplastic Constitutive Theory for Monolithic Ceramics-II

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Conference Paper

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Turbo Expo: Power for Land, Sea, and Air


Copyright © 1999 by ASME. This paper, which is the second of two in a series, exercises the viscoplastic constitutive model developed by the authors in the previous article (Janosik and Duffy. 1998), The model accounts for time-dependent phenomena '(e.g., creep, rate sensitivity, and stress relaxation) in monolithic ceramics. Additionally, the formulation exhibits a sensitivity to hydrostatic stress, and allows different behavior in tension and compression. Here, the constitutive equations formulated for the flow law (i.e., the strain rate) and the evolutionary law have been incorporated into computer algorithms for predicting the multiaxial inelastic (creep) response of a given homogeneous state of stress. Numerically simulated examples illustrate the model's ability to capture the timedependent phenomena suggested above. For each imposed service (load) history considered, creep curves and viscoplastic flow surfaces are examined to demonstrate the model's ability to capture the inelastic creep deformation response. No attempt is made here to assess the accuracy of the model in comparison to experiment. A quantitative assessment is reserved for a later date, after the material constants have been suitably characterized for a specific ceramic material.