12,665 research outputs found
Fast Fourier Transform computations and build-up of plastic deformation in 2D, elastic-perfectly plastic, pixelwise disordered porous media
Stress and strain fields in a two-dimensional pixelwise disordered system are
computed by a Fast Fourier Transform method. The system, a model for a ductile
damaged medium, consists of an elastic-perfectly matrix containing void pixels.
Its behavior is investigated under equibiaxial or shear loading. We monitor the
evolution with loading of plastically deformed zones, and we exhibit a
nucleation / growth / coalescence scenario of the latter. Identification of
plastic ``clusters'' is eased by using a discrete Green function implementing
equilibrium and continuity at the level of one pixel. Observed morphological
regimes are put into correspondence with some features of the macroscopic
stress / strain curves.Comment: 6 pages, 5 figures. Presented at the "11th International Symposium On
Continuum Models and Discrete Systems (CMDS 11)" (Ecole des Mines, Paris,
July 30- August 3 2007
Conduction in jammed systems of tetrahedra
Control of transport processes in composite microstructures is critical to
the development of high performance functional materials for a variety of
energy storage applications. The fundamental process of conduction and its
control through the manipulation of granular composite attributes (e.g., grain
shape) are the subject of this work. We show that athermally jammed packings of
tetrahedra with ultra-short range order exhibit fundamentally different
pathways for conduction than those in dense sphere packings. Highly resistive
granular constrictions and few face-face contacts between grains result in
short-range distortions from the mean temperature field. As a consequence,
'granular' or differential effective medium theory predicts the conductivity of
this media within 10% at the jamming point; in contrast, strong enhancement of
transport near interparticle contacts in packed-sphere composites results in
conductivity divergence at the jamming onset. The results are expected to be
particularly relevant to the development of nanomaterials, where nanoparticle
building blocks can exhibit a variety of faceted shapes.Comment: 9 pages, 10 figure
Characterizing the synoptic expression of the Angola low
The Angola low is a key feature of the southern Africa wet season atmosphere that influences precipitation across the continent. This paper uses ERA-Interim to show that the synoptic expression of the Angola low is a combination of dry heat lows and moist tropical low pressure systems. The Angola heat low and Angola tropical low composites are contrasted against similar lows observed in other continental tropical regions and found to be broadly comparable. The implications that the distinction between dry and moist events has for the interannual relationship among the Angola low, precipitation, and ENSO are examined. The tropical lows exhibit unusual semistationary behavior by lingering in the Angola region rather than traveling offshore. This behavior is proposed to be caused by an integrated sea breeze–anabatic wind that enhances (inhibits) cyclonic vorticity stretching and convection inland (near the coast). The combined effect of the heat lows and the anchored tropical lows creates the Angola low in the climatological average. By elucidating the mechanisms of the Angola low, this research improves the foundation of process-based evaluation of southern Africa present and future climate in CMIP and AMIP models
Measure of combined effects of morphological parameters of inclusions within composite materials via stochastic homogenization to determine effective mechanical properties
In our previous papers we have described efficient and reliable methods of
generation of representative volume elements (RVE) perfectly suitable for
analysis of composite materials via stochastic homogenization.
In this paper we profit from these methods to analyze the influence of the
morphology on the effective mechanical properties of the samples. More
precisely, we study the dependence of main mechanical characteristics of a
composite medium on various parameters of the mixture of inclusions composed of
spheres and cylinders. On top of that we introduce various imperfections to
inclusions and observe the evolution of effective properties related to that.
The main computational approach used throughout the work is the FFT-based
homogenization technique, validated however by comparison with the direct
finite elements method. We give details on the features of the method and the
validation campaign as well.
Keywords: Composite materials, Cylindrical and spherical reinforcements,
Mechanical properties, Stochastic homogenization.Comment: 23 pages, updated figures, version accepted to Composite Structures
201
Proceedings of Abstracts Engineering and Computer Science Research Conference 2019
© 2019 The Author(s). This is an open-access work distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. For further details please see https://creativecommons.org/licenses/by/4.0/. Note: Keynote: Fluorescence visualisation to evaluate effectiveness of personal protective equipment for infection control is © 2019 Crown copyright and so is licensed under the Open Government Licence v3.0. Under this licence users are permitted to copy, publish, distribute and transmit the Information; adapt the Information; exploit the Information commercially and non-commercially for example, by combining it with other Information, or by including it in your own product or application. Where you do any of the above you must acknowledge the source of the Information in your product or application by including or linking to any attribution statement specified by the Information Provider(s) and, where possible, provide a link to this licence: http://www.nationalarchives.gov.uk/doc/open-government-licence/version/3/This book is the record of abstracts submitted and accepted for presentation at the Inaugural Engineering and Computer Science Research Conference held 17th April 2019 at the University of Hertfordshire, Hatfield, UK. This conference is a local event aiming at bringing together the research students, staff and eminent external guests to celebrate Engineering and Computer Science Research at the University of Hertfordshire. The ECS Research Conference aims to showcase the broad landscape of research taking place in the School of Engineering and Computer Science. The 2019 conference was articulated around three topical cross-disciplinary themes: Make and Preserve the Future; Connect the People and Cities; and Protect and Care
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