Review: Inelastic Constitutive Modeling: Polycrystalline Materials.

This article provides a literature review that details the development of inelastic constitutive modeling as it relates to polycrystalline materials. This review distinguishes between inelastic constitutive models that account for nonlinear behavior at the microstructural level, time-independent classic plasticity models, and time-dependent unified models. Particular emphasis is placed on understanding the underlying theoretical framework for unified viscoplasticity models where creep and classical plasticity behavior are considered the result of applied boundary conditions instead of separable rates representing distinct physical mechanisms. This article establishes a clear understanding of the advantages of the unified approach to improve material modeling. This review also discusses recent topics in constitutive modeling that offer new techniques that bridge the gap between the microstructure and the continuum.

SEM and TEM data of nuclear graphite and glassy carbon microstructures.

Micrographs of multiple nuclear graphite grades were captured using scanning electron microscopy (SEM) and transmission electron microscopy (TEM), complementing the data contained in the related manuscript, "A multi-technique image library of nuclear graphite microstructures of historical and modern grades." The SEM micrographs show the differences among filler particles, binder, and thermal cracks contained in nuclear graphite. This library of microstructures serves as a baseline of as-received material and enables understanding the phases and differences between nuclear grades. TEM micrographs included in this manuscript elucidate the content of a common material contained in the binder phase known as quinoline insoluble (QI) particles. These particles are a phase of graphite that can be used as a forensic fingerprint of the neutron irradiation effects in graphite. The manuscript also contains some data of glassy carbon, an allotrope of carbon that shares similarities with some of the chaotic structures in nuclear graphite. Combined, these micrographs provide a detailed overview of the microstructures of various graphite grades prior to neutron irradiation.

Nitrogen adsorption data, FIB-SEM tomography and TEM micrographs of neutron-irradiated superfine grain graphite.

This manuscript provides raw nitrogen gas adsorption data, images and videos obtained from a technique that combines Focused Ion Beam (FIB) and Scanning Electron Microscopy (SEM) known as FIB-SEM tomography and Transmission Electron Microscopy (TEM) micrographs. This collection of data is useful for characterization of the effects of high fluence neutron irradiation in nuclear graphite as described in the associated manuscript, "Mesopores development in superfine grain graphite neutron-irradiated at high fluence" (Contescu et al., 2019). Nitrogen adsorption isotherms at 77 K are provided for graphite samples before and after neutron irradiation at 300, 450, and 750 °C at fluences before and after turnaround. FIB-SEM tomography reveals porosity of unirradiated and irradiated samples. Using this technique, four data sets were obtained, of which the first three are presented in video format, whereas the fourth one is a series of images provided in raw format unique to this manuscript. All microscopy data document the microstructure, surface area and porosity of superfine grain graphite G347A (Tokai Carbon, Japan) before irradiation and irradiated after turnaround at 400 °C. TEM micrographs provide unique information on irradiation damage at high neutron fluence (>27. 8 displacements per atom, dpa) in the microstructure and crystal lattice of graphite. Additional TEM micrographs are provided here, which do not duplicate the research paper published elsewhere (Contescu et al., 2019). These data sets are unique, as samples at high irradiation doses have never been measured or imaged before with the aforementioned techniques.