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authorJaron Kent-Dobias <jaron@kent-dobias.com>2020-01-30 13:06:58 -0500
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+%
+% poster_05.2014.tex - description
+%
+% Created by on Tue May 13 12:26:55 PDT 2014.
+% Copyright (c) 2014 pants productions. All rights reserved.
+%
+\documentclass[portrait]{a0poster}
+
+\usepackage[utf8]{inputenc}
+\usepackage[T1]{fontenc}
+\usepackage[]{amsmath}
+\usepackage{amssymb,latexsym,mathtools,multicol,lipsum,wrapfig}
+\usepackage[font=normalsize,labelfont=bf]{caption}
+\usepackage{tgheros}
+\usepackage[helvet]{sfmath}
+\usepackage[export]{adjustbox}
+\renewcommand*\familydefault{\sfdefault}
+
+\mathtoolsset{showonlyrefs=true}
+
+
+\setlength\textwidth{194pc}
+\begin{document}
+
+\setlength\columnseprule{2pt}
+\setlength\columnsep{5pc}
+\renewenvironment{figure}
+ {\par\medskip\noindent\minipage{\linewidth}}
+ {\endminipage\par\medskip}
+
+ \renewcommand\section[1]{
+ \vspace{3pc}
+ \noindent\huge\textbf{#1}\large
+ \vspace{1.5pc}
+ }
+
+ \newcommand\unit[1]{\hat{\vec{#1}}}
+ \renewcommand\vec[1]{\boldsymbol{\mathbf{#1}}}
+ \newcommand\norm[1]{\|#1\|}
+ \def\rr{\rho}
+ \newcommand\abs[1]{|#1|}
+ \def\dd{\mathrm d}
+ \def\rec{\mathrm{rec}}
+\def\CC{{C\kern-.05em\lower-.4ex\hbox{\cpp +\kern-0.05em+}} }
+\font\cpp=cmr24
+\def\max{\mathrm{max}}
+
+ \noindent\hspace{177pc}\includegraphics[width=18pc]{CULogo-red120px.eps}
+ \vspace{-24.5pc}\\
+ \Huge \textbf{Elastic properties of hidden order in URu$_{\text2}$Si$_{\text2}$ are reproduced by\\ staggered nematic order}
+ \bigskip\\
+ \huge \textbf{Jaron~Kent-Dobias, Michael Matty \& Brad J Ramshaw}
+ \vspace{1pc}
+
+
+ \begin{multicols}{2}
+
+ \section{Introduction}
+ \Large
+
+ \begin{wrapfigure}{r}{.25\textwidth}
+ \centering
+ %\includegraphics[width=0.25\textwidth]{imgs/crack.jpg}
+ \caption{Cracking in concrete.}
+ \end{wrapfigure}
+
+ Understanding material cracking and fracture is necessary for
+ understanding the aging and failure of those materials in our buildings
+ and infrastructure. In ordinary brittle materials like glass, stress at
+ the tip of a crack causes it to quickly and cleanly propagate through the
+ material. In ductile materials like metals, this stress is reduced by
+ plastic deformation around the crack tip, forming the crack's
+ \textbf{process zone}. In quasi- (or disordered) brittle materials like
+ concrete, this stress is reduced by opening a complicated network of
+ microcracks in the process zone. This makes the structure of the
+ quasibrittle process zone and crack propagation
+ difficult to study by ordinary means.
+
+
+ \section{Fuse Networks}
+
+ \begin{wrapfigure}{l}{.25\textwidth}
+ \centering
+ %\includegraphics[width=0.12\textwidth]{imgs/square_network.pdf}
+ %\includegraphics[width=0.12\textwidth]{imgs/square_high_beta.pdf}\\
+ %\includegraphics[width=0.12\textwidth]{imgs/voronoi_network.pdf}
+ %\includegraphics[width=0.12\textwidth]{imgs/voronoi_high_beta.pdf}
+ \captionof{figure}{Contrasting the square (top) and voronoi (bottom) networks. {\bf Left:} Unbroken fuse networks. {\bf Right:} A
+ fracture surface in each at low disorder ($\beta=10$).}
+ \label{nets}
+ \end{wrapfigure}
+
+ \Large
+
+ We model quasibrittle cracking and fracture using simulations of fuse
+ networks, which are electrical systems of resistive fuses whose random
+ current thresholds $t$ are cumulatively distributed by $t^\beta$. $\beta$
+ parameterizes the amount of disorder in the system: large
+ $\beta$ corresponds to vanishing disorder, small $\beta$ to very large
+ disorder. Fracture is performed adiabatically: the fuse whose ratio of
+ current to threshold is largest breaks, and the current across the
+ networks is recomputed. In order to reduce lattice effects, which become large for
+ small disorder (see Figure \ref{nets}), we use voronoi meshes for our fuse networks.
+
+
+ \section{Homogeneous Scaling}
+
+ \begin{wrapfigure}{r}{0.25\textwidth}
+ \centering
+ %\includegraphics[width=0.25\textwidth]{imgs/ashivni.png}
+ \captionof{figure}{The `phase diagram' for fracture in homogeneous
+ systems.}
+ \label{ashivni}
+ \end{wrapfigure}
+
+ \Large
+
+ The problem of fracture in fuse networks was unresolved until recently.
+ For low disorder, fracture is nucleation-like, similar to that of ordinary
+ brittle systems. At large disorder, fracture occurs after a very large
+ amount of uncorrelated damage, and appears percolation-like.
+ Sethna and Shekhawat developed a theory which unifies these behaviors with
+ an {\sc rg} crossover at intermediate disorder characterized by mean-field
+ avalanches. The percolation-like behavior at high disorder was shown to
+ be unstable under course-graining, and therefore any nonzero $\beta$
+ will cause nucleated fracture at a sufficiently large system size (see
+ Figure \ref{ashivni}).
+
+ In unpublished work, Shekhawat and Sethna found a scaling form for the
+ distribution of network strengths $\sigma_\max$, the largest current
+ applied to the network before it has broken. It is given by
+ \begin{equation}
+ P(\sigma_\max\mid\beta, L,u)=\sigma_\max^{-\tau_\sigma}\mathcal P(\beta
+ L^{1/\nu_f},\sigma_\max L^\delta,uL^{-\Delta/\nu_f})\label{form}
+ \end{equation}
+ where $\tau_\sigma$, $\nu_f$, $\delta$ and $\Delta$ are universal
+ exponents, $L$ is the system size, and $u$ is an irrelevant scaling
+ variable.
+
+ \begin{figure}
+ \vspace{1pc}
+ \centering
+ %\includegraphics[width=0.325\textwidth]{imgs/voronoi_homo_big.pdf}
+ %\includegraphics[width=0.325\textwidth]{imgs/voronoi_homo_med.pdf}
+ %\includegraphics[width=0.325\textwidth]{imgs/voronoi_homo_lit.pdf}\\
+ \begin{minipage}[c]{0.325\textwidth}\centering$\pmb{\beta=3}$\end{minipage}
+ \begin{minipage}[c]{0.325\textwidth}\centering$\pmb{\beta=0.5}$\end{minipage}
+ \begin{minipage}[c]{0.325\textwidth}\centering$\pmb{\beta=0.03}$\end{minipage}\\
+ \captionof{figure}{Fractured fuse networks at various $\beta$. Each colored region shows a
+ contiguous cracked cluster. The black region shows the surface of
+ the spanning crack.}
+ \label{homo}
+ \vspace{1pc}
+ \end{figure}
+
+
+ \section{Scaling in the Process Zone}
+
+ \begin{figure}
+ \centering
+ %\includegraphics[width=0.245\textwidth]{imgs/sample_16.pdf}
+ %\includegraphics[width=0.245\textwidth]{imgs/sample_32.pdf}
+ %\includegraphics[width=0.245\textwidth]{imgs/sample_64.pdf}
+ %\includegraphics[width=0.245\textwidth]{imgs/sample_128.pdf}\\
+ \begin{minipage}[c]{0.245\textwidth}\centering$\pmb{L=16,\;\beta=1.9}$\end{minipage}
+ \begin{minipage}[c]{0.245\textwidth}\centering$\pmb{L=32,\;\beta=1.2}$\end{minipage}
+ \begin{minipage}[c]{0.245\textwidth}\centering$\pmb{L=64,\;\beta=0.78}$\end{minipage}
+ \begin{minipage}[c]{0.245\textwidth}\centering$\pmb{L=128,\;\beta=0.5}$\end{minipage}\\
+ \captionof{figure}{Notched fuse networks at critical stress. The
+ disorder for each system is tuned so that $\beta L^{1/\nu_f}$ is
+ constant, and the statistics of each should scale trivially.}
+ \vspace{1pc}
+ \label{notches}
+ \end{figure}
+
+ \Large
+ We have made progress for developing a scaling theory of damage and stress
+ in the process zone of quasibrittle cracks. We have essentially taken the
+ scaling behavior of \eqref{form} as an ansatz for how the corresponding
+ qualities of a critically semi-cracked network should scale. We have
+ begun demonstrating the validity of this theory. Figure \ref{notches}
+ shows critically cracked networks at constant $\beta L^{1/\nu_f}$, an
+ invariant scaling combination under this theory. As can be seen in Figure
+ \ref{collapse}, the disorder-averaged stress profiles caused by each
+ collapses nicely.
+
+ \begin{figure}
+ \centering
+ %\includegraphics[width=0.5\textwidth]{imgs/legends.pdf}\\
+ \vspace{-.5em}
+ %\includegraphics[width=0.505\textwidth,valign=t]{imgs/sample_collapse_1.pdf}\hfill
+ %\includegraphics[width=0.48\textwidth,valign=t]{imgs/sample_collapse_2.pdf}\\
+ \vspace{-.5em}
+
+ \captionof{figure}{Disorder-averaged stress $\sigma$ as a function of
+ distance $x$ from the tip of a critical crack. $\beta L^{1/\nu_f}$ is
+ constant for each curve. \textbf{Left:} The unmodified stress.
+ \textbf{Right:} The stress collapsed.}
+ \label{collapse}
+ \end{figure}
+
+ \section{Next Steps}
+
+ \begin{wrapfigure}{r}{0.25\textwidth}
+ \centering
+ \vspace{-2em}
+ %\includegraphics[width=.25\textwidth]{imgs/voronoi_heir.pdf}
+ \captionof{figure}{A hierarchical voronoi lattice.}
+ \end{wrapfigure}
+
+ \Large
+
+ The voronoi networks we are able to generate allow us great flexibility
+ for future multiscale computational modelling. Once we have hashed out
+ our scaling theory more thoroughly, we plan on using it to probe much
+ larger systems than previously feasible using networks whose fuse density
+ becomes smaller in regions of less importance. This should allow us to
+ see cleaner stress and damage scaling and cleanly stitch our discrete system to a
+ continuum approximation.
+
+ \end{multicols}
+\end{document}
+