Amit Acharya's picture

Scaling theory of continuum dislocation dynamics in three dimensions: Self-organized fractal pattern formation

Y. S. Chen, W. Choi, S. Papanikolaou, M. Bierbaum, J. P. Sethna

 We focus on mesoscopic dislocation patterning via a continuum dislocation
dynamics theory (CDD) in three dimensions (3D). We study three distinct
physically motivated dynamics which consistently lead to fractal formation in
3D with rather similar morphologies, and therefore we suggest that this is a
general feature of the 3D collective behavior of geometrically necessary
dislocation (GND) ensembles. The striking self-similar features are measured in
terms of correlation functions of physical observables, such as the GND
density, the plastic distortion, and the crystalline orientation. Remarkably,
all these correlation functions exhibit spatial power-law behaviors, sharing a
single underlying universal critical exponent for each type of dynamics

Article in Intl. Journal of Plasticity

Article at

Kamyar M Davoudi's picture

Eighty Years of Dislocation Theory and Work Hardening

On February 7, 1934, two consecutive papers by Sir Geoffrey Ingram Taylor were received and so the dislocation theory was born and the first attempt at describing work hardening was made. Before that date, it was known that there was a big gap between the ideal and the experimentally observed shear strength. While according to the calculations, the shear strength had to be of the order of one tenth (or with finer models one thirtieth) of the shear modulus, the measured shear strength was several orders of magnitude smaller. This large discrepancy brought about Geoffrey I.Taylor, Egon Orowan and Michael Polyani to independently postulate the existence of dislocations. Papers by Orowan and Polyani were published consecutively in one volume of Zeitschrift für Physik.

Jizhou Song's picture

Caltech: secrets of the world’s number one university

Good International news on Caltech and engineering. Ares Rosakis, chair of the Division of Engineering and Applied Science,describes Caltech as “a unique species among universities…a very interesting phenomenon”.More can be found in the attachment or at the link below

Rongmei niu's picture

instability induced by incoherent twin boundary in nanotwinned copper

1. Strain hardening and softening in nanotwinned Cu:

Nanotwinned Cu foils with about 99% coherent twin boundaries (TBs) among all the boundaries were made. These coherent

TBs, with an average spacing of 25 nm, were engineered approximately parallel to foil surfaces. Low plane-strain deformation

enhances the hardness by refining microstructure and introducing dislocations. High plane-strain deformation results in crystallographic

lattice rotation and reaction between dislocations and coherent TBs, and induces incoherent TBs, thus twin coarsening and

even diminishing of nanotwins accompanied by recovery and recrystallization, which cause softening.

SIMULIA's picture

Early Bird gets the...... Discount!

Way less gross than worms ;) Register today  for the SIMULIA Community Conference and save $200!

Oden Warren's picture

UPDATED: Nanobrücken 2014 Nanomechanical Testing Workshop

Dear Colleague: You are cordially invited to participate in the Nanobrücken 2014 Nanomechanical Testing Workshop, which will take place March 26-28, 2014 at INM - Leibniz Institute for New Materials in Saarbrücken, Germany. This will be the 4th edition of the annual Nanobrücken workshop series. This year's Keynote Speaker will be Andrew Minor (University of California, Berkeley).

Post-doctorate Positions in Offshore Engineering at National University of Singapore

The Department of Civil and Environmental Engineering at the National University of Singapore (NUS) is recruiting 2 post-doctorate research fellows to pursue research on ice-structure interaction in the Keppel-NUS Corporate Laboratory. As part of the S$75 million collaboration between Keppel Corporation and NUS, the team comprising of Prof. Andrew Palmer, Dr. Bai Wei, and Dr. Pang Sze Dai, seeks to develop solutions for offshore rigs to meet the challenges of harsh arctic environments in oil and gas exploration and production.

Francois Barthelat's picture

Post-doctoral position in bio-inspired micro-architectured materials at McGill University

I have an open position for a Post-doctoral researcher in the area of biomimetic materials, starting immediately. The successful candidate will explore and optimize bioinspired microarchitectures to increase the mechanical performance of engineering materials (glasses, ceramics, polymers).  This work will expand on our recent progress on overcoming the brittleness of glass ( Materials and systems of interest include nacre-like ceramic / polymeric composites, multilayered conch-shell like composites and fish-scale inspired flexible protective systems.

Zhigang Suo's picture

Inglis (1913) vs. Griffith (1921)

I have updated my notes on the Griffith paper.  I added more description on the experimental determination of surface tension of solids.  Griiffith himself determined the surface tension of glass by an experimental setup.  Udin et al (1949) described a setup based on the same principle.  This setup is now known as the zero creep experiment.

Grants for 3rd International Workshop on Physics Based Material Models and Experimental Observations Cesme/Turkey 2-4 June

In 2012 and 2013 we organized very successful Workshops on
"Physics-based material models and experimental observations" funded
by the European Union's Enlargement programme. We cordially invite you to
submit an abstract to the 3rd International Workshop on Physics Based
Material Models and Experimental Observations
to be held on 2-4 June
2014 in Cesme-Izmir/Turkey.

Davide Bigoni's picture

Extremely deformable structures. CISM 2014 Advanced School: Udine, Italy, June 2 - 6 2014 .


Basile Audoly - Université Pierre et Marie Curie and CNRS, Paris, France

Katia Bertoldi - University of Harvard, Cambridge, MA, USA

Davide Bigoni - Università di Trento, Italy

Alain Goriely - University of Oxford, UK

Sébastien Neukirch - Université Pierre et Marie Curie and CNRS, Paris, France

Sergio Pellegrino - California Institute of Technology, Pasadena, CA, USA


see the attachment for details on the course and the registration

Geotechnical Engineering position at the Assistant Professor level

The Civil Engineering Department at Universidad EAFIT in Medellín, Colombia is seeking applicants for a tenure track position in the field of Geotechnical Engineering. Interested candidates must have a PhD degree in the field.  The selected candidate is expected to conduct research in the area of Geotechnical Engineering, and create and promote graduate courses.

Horacio Espinosa's picture

Research Engineer Position at iNfinitesimal LLC

Research Engineer Position in  Microfluidics/BioMEMS at iNfinitesimal LLC

2014 James Watt PhD Scholarship available (in Multiscale Tissue Mechanics) at Heriot-Watt University, Edinburgh, UK

2014 James Watt PhD Scholarship, School of Engineering and Physical Sciences, Heriot-Watt University, Edinburgh, UK


More details can be found at


Graduate positions at Universidad EAFIT-Colombia

The applied mechanics group through its research lines in Seismic Engineering and Computational Mechanics is offering three graduate student positions at the MsC and PhD levels to conduct research in projects related to:

Xuanhe Zhao's picture

Call for Abstracts: Symposium on Mechanics of Soft Materials - ASME IMECE 2014

Dear Colleagues:

We would like to invite you to present your work at "Symposium on Mechanics of Soft Materials" in ASME 2014 International Mechanical Engineering Congress & Exposition ASME Congress and Exposition, Montreal's downtown convention center, 14-20 November 2014.

Symposium Description

A multiscale modeling scheme based on peridynamic theory

A multiscale modeling scheme based on peridynamic theory

Rezwanur Rahman

Postdoctoral fellow, Center for simualtion, visualization and real time prediction (SiViRt), University of Texas at San Antonio)

John Foster

Assistant Professor, Department of Mechanical Engineering, University of Texas at San Antonio

Anwarul Haque

c.tasan's picture

MSc, PhD and Post-doc Vacancies in Max-Planck Institute @ Dusseldorf, Germany

Openings at various levels are immediately available in Max-Planck Institute for Iron Research, for projects on experimental micro-mechanics and/or alloy design. The positions are in the group of Cem Tasan (Adaptive Structural Materials), in the Microstructure Physics and Alloy Design department of prof. Dierk Raabe.

For more details on the openings and the group, please visit

For more information regarding the institute, please visit 

To apply, please send an email to or

SIMULIA's picture

STOP! Hey, what's that sound? Everybody look what's goin' down............. in the SIMULIA Learning Community!

I think you all will be happy to hear a few amazing accomplishments that
occurred in 2013 in the SIMULIA Learning Community. We are so pleased
to announce that the SLC contains well over 12,000 members and is
growing daily - THANK YOU!!! These members include SIMULIA users,
advocates, academics, commercial customers, researchers and more!

Additionally, we received our first few CUSTOMER blog posts created and
published to the community and we could not be more excited about it.
As always, I want to emphasize that this community is for YOU. We strive
to always provide you with the most exciting and useful content on a
regular basis - so please continue to check back often!

Cédric Bellis's picture

Post-Doc position with Del Duca – Academie des Sciences Foundation at LMA Marseille, France

Applications are invited for a postdoctoral position in the area of large-scale inversion and imaging using acoustic waves and high-performance computing.

At the interface between the fields of solid mechanics, acoustics and numerical modeling, the present job offer focuses on inverse problems with the aim of extending applications of the spectral-element method and petascale high-performance computing to (1) ocean acoustics and for (2) non-destructive material testing.  

What is prony series about ?

Hi everyone, 

I cannot get the actual significance regarding the usage of Prony  series and Shift factors in the material modelling of the viscoelastic material. 

Please can anyone post some insights into this. Would be helpful. 

ruzzene's picture

Vibration testing of a football helmet

Dear All

please find a link to a story describing the results of a final project that I assigned for my graduate "Experimental Structural Dynamics" class. This is timely, on this Superbowl Sunday and the broad coverage of safety issues related to Football and head injuries.

mohsenzaeem's picture

Call for Abstracts in Mini-Symposium on "Computational Modeling of Microstructural Evolution II”- ASME Congress 2014

Dear Colleague,

We would like to invite you to participate in a mini-symposium entitled “Computational Modeling of Microstructural Evolution II” in ASME 2014 International Mechanical Engineering Congress & Exposition (
ASME Congress and Exposition will be held in Montreal's downtown convention center, 14-20 November 2014.

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