Theses and Dissertations

Issuing Body

Mississippi State University

Advisor

Bammann, Douglas J.

Committee Member

Horstemeyer, Mark F.

Committee Member

Hammi, Youssef

Committee Member

Ostien, Jakob B.

Date of Degree

8-15-2014

Document Type

Dissertation - Open Access

Major

Mechanical Engineering

Degree Name

Doctor of Philosophy

College

James Worth Bagley College of Engineering

Department

Department of Mechanical Engineering

Abstract

A material model capable of reproducing the anisotropic behavior of polycrystalline materials will prove to be useful in simulations in which directional properties are of key importance. The primary contributor to anisotropic behavior in polycrystalline materials is the development of texture through the rotation and alignment of slip systems due to plastic deformation. A large concentration of aligned slip systems will influence the glide of dislocations in the respective global deformation direction resulting in a directionally dependent flow stress. The Evolving Microstructural Model of Inelasticity (EMMI) is modified to account for evolving anisotropy due to the development of texture. Texture is characterized via a second order orientation tensor and is incorporated into EMMI through various modifications to the EMMI equations based on physical assumptions. Evolving anisotropy is captured via a static yield surface through a modification to the flow rule based on the assumption loading is entirely elastic within the yield surface. A separate modification to EMMI captures evolving anisotropy through an apparent yield surface via a modification to the EMMI internal state variable evolution equations. The apparent yield surface is the result of a smaller yield surface translating through stress space and assumes the state of the material is disturbed at stresses much lower than indicated by experimental yield surfaces.

URI

https://hdl.handle.net/11668/20158

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