Plasticity
Surface mediated plasticity in sub-10-nm-sized gold crystals
Although deformation processes in submicron-sized metallic crystals are
well documented, the direct observation of deformation mechanisms in
crystals with dimensions below the sub-10-nm range is currently lacking.
Here, through in situ high-resolution transmission electron
microscopy (HRTEM) observations, we show that (1) in sharp contrast to
what happens in bulk materials, in which plasticity is mediated by
dislocation emission from Frank-Read sources and multiplication, partial
dislocations emitted from free surfaces dominate the deformation of
Soil Mechanics and Fossil Dinosaur Trackways
My PhD student Peter Falkingham (who graduated 15 December 2010) has published some interesting papers on Dinosaur Trackways. These might be of interest to those teaching Soil Mechanics, to give some examples that might be more stimulating than foundation design or traditional geotechnical engineering.
References below:
Research associate position at University of Sheffield
The successful candidate will work on the EPSRC funded research project 'Ultimate and permissible limit state behaviour of soil-filled masonry arch bridges', which is being undertaken in collaboration with the University of Salford and various industrial partners (Network Rail, ADEPT, the International Union of Railways and Balfour Beatty Rail). This is an exciting opportunity to help develop the next generation of analysis and assessment techniques for masonry arch bridges, thus helping to ensure a sustainable future for structures that continue to form a vitally important part of the rail and regional road networks of the UK and other countries.
Research assistant and PhD position at PoliMi on micro-plasticity models
In the last decade, different
cyclic plasticity models, based on the “continuum” approach, have been proposed
in order to account for different mechanical effects (such as ratchetting,
strain range dependence, non-proportional loading and memory effect), [1, 2]. A
disadvantage of this approach is the elevated number of model parameters
introduced in order to correctly predict the material behaviour. The determination
of these parameters, usually difficult and expensive, is one of the reasons why the modern
constitutive models are not widely used in finite element simulations of
APS March Meeting Focus session: "Fracture, Friction, and Deformation Across Length Scales"
Abstracts due Friday, Nov. 19, 2010
APS March Meeting Focus session: "Tribophysics: Friction, Fracture and Deformation Across Length Scales"
March 21 - 25, 2011, Dallas, Texas
Details at http://www.aps.org/meetings/march/scientific/focus2.cfm#12.7.3
Invited speakers: Michael Marder (Univ. of Texas); Julia Greer (Caltech)
Organizers: Robin Selinger (Kent State), Jacqueline Krim (NCSU), Noam Bernstein (NRL)
Microcanonical Entropy and Mesoscale Dislocation Mechanics and Plasticity
(Journal of Elasticity, Carlson memorial Volume)
A methodology is devised to utilize the statistical mechanical entropy of an isolated, constrained atomistic system to define the dissipative driving-force and energetic fields in continuum thermomechanics. A thermodynamic model of dislocation mechanics is discussed. One outcome is a definition for the mesoscale back-stress tensor and the symmetric, polar dislocation density-dependent, Cauchy stress tensor from atomistic ingredients.
Plasticity Data in Vumat
Hello everyone,
I am using a VUMAT with isotropic hardening in my three dimensional model. Can someone tell me how is plasticity data passed into this subroutine? In VUMAT for kinematic hardening we define the yield stress and hardening modulus along with E and poisson's ratio in *User Material. I did not find any isotropic hardening VUMAT examples in manual. Do we define the hardening modulus or the yield stress-plastic strain data in isotropic hardening VUMAT? I will be really thankful if anyone can help me.
Thank you
Swapnil
Disparity in Simple Shear solution in ABAQUS
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Dear All,
We tried to simulate simple shear using ABAQUS and compared it with the analytical solution. To our surprise, even though the equivalent stress and strain matched perfectly, the component stress and strain had a large deviation between the semi analytical and ABAQUS methods. The zero components in the analytical model were calculated to be non-zero in the results of ABAQUS. This paradox could not be understood clearly as whether it is a case of software deficiency or conceptual error. A COMPLETE ANALYSIS OF THE PROBLEM IS ATTACHED AS A REPORT.
A new postdoc position is available
A new postdoctoral position in continuum mechanics is available at the Weizmann Institute of Science. Candidates should have a strong background in physics and/or theoretical mechanics, as well as experience with analytical and computational methods for solving partial differential equations. Possible projects include the mechanics of frictional sliding, the mechanics of biomaterials, the mechanics of glassy materials and dislocation-mediated plasticity. Highly motivated candidates are requested to send their CV, publications list and statement of research interests to Dr.