Date of Award

2018

Degree Type

Dissertation

Degree Name

Doctor of Engineering

Department

Mechanical Engineering

First Advisor

Duffy, Stephen

Subject Headings

Mechanical Engineering

Abstract

Graphite material is used extensively in nuclear reactors however the material has a limited strain range for elastic behavior. This provides the motivation to derive a constitutive model that captures the inelastic deformations exhibited by this material. This dissertation first presents details of an isotropic constitutive model derived using continuum principles of engineering mechanics that accounts for different inelastic behavior in tension and compression. An inelastic dissipation function was developed using an integrity basis proposed by Green and Mkrtichian (1977) for the isotropic version of the model. This isotropic model was then extended to capture anisotropic stress-strain behavior using directional tensors associated with the material symmetry. In the case of anisotropic graphite the material typically exhibits transversely isotropic behavior. The model parameters were characterized using stress-strain data from several grades of nuclear graphite. Once the model parameter were characterized several benchmark structural components were analyzed with the intent of showing that the model's predictive capability relative to simple component level behavior.

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