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Title Towards modeling the anisotropic behavior of polycrystalline materials due to texture using a second order structure tensor
URL
Publication Date
Degree PhD
Discipline/Department Mechanical Engineering
Degree Level doctoral
University/Publisher Mississippi State University
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.
Subjects/Keywords polycrystalline; texture; orientation distribution function; structure tensor; anisotropy; EMMI
Contributors Douglas J. Bammann (chair); Mark F. Horstemeyer (committee_member); Youssef Hammi (committee_member); Jakob B. Ostien (committee_member)
Language en
Rights unrestricted
Country of Publication us
Format application/pdf
Record ID oai:library.msstate.edu:etd-07022014-113740
Repository msstate
Date Retrieved
Date Indexed 2020-10-15
Grantor MSSTATE

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…orientation of developing substructure within the material obstructing deformation along the preferred directions of deformation. Other factors that may contribute to the anisotropic behavior of a polycrystalline material include grain size and shape…

…conclusion of the work and Chapter 6 discusses the extension of the presented model in future work. 3 1.2 Microstructure Development Polycrystalline materials are aggregates composed of many grains with each grain pos- sessing its own crystallographic…

…1934, metallic grains plastically deform along their discrete slip systems via dislocation slip. The anisotropic behavior of a polycrystalline aggregate is not effected by the orientation of a single grain within the aggregate, but is dictated by a…

…cumulative effect of many grains [46]. Processing conditions present in the fabrication of polycrystalline metals can produce seemingly random grain orientations, resulting in apparent isotropic behavior of the aggregate. With the onset of plastic…

polycrystalline 8 simulation using a crystal plasticity model[19, 18]. However, Mathur and Dawson [121] extended the work presented by Kocks [91, 93] to implement a material point simulator capable of predicting the evolving texture…

…when compared to the volume of a typical component, defining a material point as single grain is not feasible for large scale simulations. Some of the earliest models to consider polycrystalline materials were proposed by Taylor [176, 175, 174]…

…also modeled using an orientation distribution function (ODF) or tensorial variable describing the distribution function. Rashid [149] determined the orientational effects of yield stress of a polycrystalline material in biaxial…

…tensor. Plastic spin of this form is in agreement with a form described by Dafalias [45] and Loret [113] using representation theorems with a second order structure tensor and a scalar parameter. Bammann and Aifantis [53]…

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