317 research outputs found
Variational modeling of microstructures in plasticity
No full textThe analysis and simulation of microstructures in solids has gained crucial importance, virtue of the influence of all microstructural characteristics on a material’s macroscopic, mechanical behavior. In particular, the arrangement of dislocations and other lattice defects to particular structures and patterns on the microscale as well as the resultant inhomogeneous distribution of localized strain results in a highly altered stress-strain response. Energetic models predicting the mechanical properties are commonly based on thermodynamic variational principles. Modeling the material response in finite-strain crystal plasticity very often results in a nonconvex variational problem so that the minimizing deformation fields are no longer continuous but exhibit small-scale fluctuations related to probability distributions of deformation gradients to be calculated via energy relaxation. This results in fine structures which can be interpreted as the observed microstructures.
This manuscript is supposed to give an overview of the available methods and results in this field. We start by discussing the underlying variational principles for inelastic materials, derive evolution equations for internal variables, and introduce the concept of condensed energy. As a mathematical prerequisite we review the variational calculus of nonconvex potentials and the notion of relaxation. We use these instruments in order to study the initiation of plastic microstructures. Here we focus on a model of single-slip crystal plasticity. Afterward we move on to model the evolution of microstructures. We introduce the concept of essential microstructures and the corresponding relaxed energies and dissipation potentials, and derive evolution equations for microstructure parameters. We then present a numerical scheme by means of which the microstructure development can be computed, and show numerical results for particular examples in single- and double-slip plasticity. We discuss the influence of hardening and of slip system orientations in the present model
Rate-Independent versus Viscous Evolution of Laminate Microstructures in Finite Crystal Plasticity
No full textIn this chapter we investigate the variational modeling of the evolution of inelastic microstructures by the example of finite crystal plasticity with one active slip system. For this purpose we describe the microstructures by laminates of first order.We propose an analytical partial relaxation of an incompressible neo-Hookean energy formulation, keeping the internal variables and geometric microstructure parameters fixed, thus approximating the relaxed energy by an upper bound of the rank-one-convex hull. Based on the minimization of a Lagrange functional, consisting of the sum of rate of energy and dissipation potential, we derive an incremental strategy to model the time-continuous evolution of the laminate microstructure. Special attention is given to the three distinct cases of microstructure evolution, initiation, rotation, and continuous change. We compare a rate-independent approach with another one that employs viscous regularization which has certain advantages concerning the numerical implementation. Simple shear and tension/compression tests will be shown to demonstrate the differences between both approaches and to show the physical implications of the models introduced
Werte schulischer Begabtenförderung: Begabung und Verantwortung
No full textDie Übernahme von Verantwortung ist Teil der Selbst- und Persönlichkeitsbildung in unterschiedlichen Bereichen des Lernens und des Lebens. Was bedeutet dies aber für Hochbegabte und die Hochbegabtenförderung?
Das Karg Heft 05 setzt sich mit der Verantwortung des Bildungssystems und seiner Akteure hinsichtlich verantwortungsvoller Hochbegabtenförderung auseinander - und thematisiert, wie Orte der Hochbegabtenförderung gedacht und konzipiert sein müssen, in denen Verantwortung sich selbst und anderen gegenüber begabungsfördernd gelebt werden kann.
Das Karg Heft 05 bildet Beiträge und Ergebnisse vom gleichnamigen GADHEIMER KREIS 2011 ab.
Mit Beiträgen von:
Ingmar Ahl, Klaus Amann, Armin Hackl, Annette von Manteuffel, Corinna Maulbetsch, Victor Müller-Oppliger, Jürgen Nielsen-Sikora, Margret Rasfeld, Reinhard Ruckdeschel, Anne Sliwka, Olaf Steenbuck und Gabriele Weigand/Claudia Pauly.https://www.karg-stiftung.de/medien/karg-heft-05-1069/unknow
Using Fiction to Teach Writing and Revision Techniques
No full textWould you like to take your writing and that of your students to the next level? This interactive session, led by award-winning and best-selling author Jo Watson Hackl, will equip you with tools and techniques to use with your students to help make their writing more powerful, more persuasive and more fun. Handouts include writing prompts, brainstorming tools, tips to keep inspiration close at hand, and an author-created bookmark revision tool that can be used for both creative writing and academic essays
A study on the principle of maximum dissipation for coupled and non-coupled non-isothermal processes in materials
No full text
The expression for entropy production owing to diffusion used in Hackl
et al.
(2010
Proc. R. Soc. A
467
, 1186–1196. (
doi:10.1098/rspa.2010.0179
)) has led to some discussion concerning its definition and comparability with terms found in the literature. Therefore, in this addendum, we introduce a slight modification which leads to a more consistent result that can be better interpreted in the light of existing literature.
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A Mississippi Ghost Town, A Reclusive Artist, and a Poetry-Loving Dog: Drawing Inspiration from Real Life
No full textSometimes the best ideas for fiction come from real life. This interactive session by award-winning and best-selling author Jo Watson Hackl presents techniques and tools that participants can use to help their students draw upon their own experiences to create characters who come alive, settings that feel lived-in, and plots that keep the reader engaged from the first page to the last word. Handouts include: worksheets for mining personal experiences for character, setting and plot ideas; and tools and techniques to translate those ideas into stories that connect with readers
Improving draft genome contiguity with reference-derived in silico mate-pair libraries
No full textBackground: Contiguous genome assemblies are a highly valued biological resource because of the higher number of completely annotated genes and genomic elements that are usable compared to fragmented draft genomes. Nonetheless, contiguity is difficult to obtain if only low coverage data and/or only distantly related reference genome assemblies are available. Findings: In order to improve genome contiguity, we have developed Cross-Species Scaffolding - a new pipeline that imports long-range distance information directly into the de novo assembly process by constructing mate-pair libraries in silico. Conclusions: We show how genome assembly metrics and gene prediction dramatically improve with our pipeline by assembling two primate genomes solely based on ~30x coverage of shotgun sequencing data
Poetry to Promote Inclusion and Improve Writing
No full textPoetry is a powerful tool for students to express their diverse perspectives, honor the perspectives of others, and improve writing skills. This session by best-selling and award-winning author Jo Watson Hackl, will provide data on the value of creating and studying poetry, especially for students from historically marginalized communities. She will then present practical techniques that participants can use with students to help them use poetic techniques to become more critical readers and to make their own poetry and prose writing stronger
"Es ist jeder sein eigener Teufel". Humor und Ironie in den Erzählungen von Kurd Laßwitz
No full textL'opera di Kurd Laßwitz usa i modelli della letteratura borghese da salotto di fine Ottocento per divulgare le conoscenze scientifiche del suo tempo: attraverso l'ironia, tuttavia, i presupposti di quella scienza vengono sottilmente messi in discussione. Questo saggio si occupa di definire i meccanismi attraverso i quali ciò avviene
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