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Post-Doctoral Fellow in Computational Structural/Solid Mechanics and Design

Applicants are sought to fill a post-doctoral position in
computational solid/structural mechanics and design. The selected applicant will work
closely with Prof. Masoud Rais-Rohani and his research colleagues and graduate

In situ nanocompression testing of irradiated copper

Dear colleagues,

we recently published a paper on measuring bulk properties of irradiated copper from nanoscale samples:

Hope you find this interesting!



In situ nanocompression testing of irradiated copper

Dear Colleagues,

we recently published a paper on measuring bulk properties of irradiated from nanoscale compression samples:

Hope you find this interesting!



Kejie Zhao's picture

Lithium-assisted plastic deformation of silicon electrodes in lithium-ion batteries: a first-principles theoretical study

Silicon can host a large amount of lithium, making it a promising electrode for high-capacity lithium-ion batteries.  Recent experiments indicate that silicon experiences large plastic deformation upon Li absorption, which can significantly decrease the stresses induced by lithiation and thus mitigate fracture failure of electrodes. These issues become especially relevant in nanostructured electrodes with confined geometries.

Zhiqiang Wang's picture

Postdoc position available in Compuational Materials Modeling

The Department of Materials Science and Engineering in the College of Engineering at the University of North Texas (UNT) seeks highly qualified applicants for a postdoctoral researcher position in computational materials modeling. The successful candidate will work on multiscale modeling of defects and microstructures (e.g., dislocations, grain boundaries, etc), and damage and failure of materials to design and evaluate advanced superalloys for aerospace applications, as part of the federally-funded research program in the Institute for Science and Engineering Simulation (ISES).

DEM modelling of granular flow

Hi iMechanica,

I want to start a discussion on the current status of DEM modelling of granular media. I know that Luding has published many papers in this area. Please add to the current research on granular flow modelling like viscoplasticity, hypoplasticity etc and the  numerical DEM methods.

Modeling Metal forming in Abaqus...

I'm currently working on my master thesis which is in the area of metal
forming simulation...

I have one question,,, when adding material plasticity in Abaqus using the
power law...

to what limit shall i go in the tabulated form is it to 100% plasticity or
to the maximum strain the material can take...

 in other word,,, if the power law is: σ =250*εp^0.123...

shall i inter the values till at σ=250, ε=1... or shall i stop at let say ε=0.25...



bitamendi's picture

Lemaitre and Caboche mixed hardening model



I'm working in a cyclic loding metal deformation, and I'm interesting about mixed hardening models.


I need help to know what is the "Lemaitre and chaboche(1990)" mixed hardening model, do enyone know? Is similar to the Amstrong-Frederic model??? How is represented the isotropic hardening?





Dear Friends,

I have written a UEL for Strain Gradient Plasticity and is working well when i give Boundary condition as Concentrated force, But when i apply displacement boundary condition the it leads to 'system error 144'.

Iknow that system error 144 corresponds to division by zero or infinity, but then why it is coming in on displacement boundary condition is i am worried about.

I will be extremely helpful to anybody for any type of help on above problem.

Thanking you in advance


Jeffrey Kysar's picture

Measurements of Geometrically Necessary Dislocation Densities on Individual Slip Systems

We have recently published a paper on measurements of the density of geometrically necessary dislocations (GND) associated with wedge indentation of a single face-centered cubic crystal. The deformation field is two-dimensional and there are three effective in-plane slip systems that contribute to the plastic slip. We determine the lower bound on the total GND density with a three micrometer spatial resolution. We also show that in certain regions of the domain, the lower bound on total GND density corresponds to the exact total GND density.

Amit Acharya's picture

On the three-dimensional Filon construct for dislocations

(to appear in the Intl. Journal of Engineering Science)

 Robin J. Knops and Amit Acharya

 The relationship between dislocation theory and the difference of linear elastic solutions for two different sets of elastic moduli, derived by Filon in two-dimensions, is generalised to three-dimensions. Essential features are developed and illustrated by the  examples of the edge and screw dislocations. The inhomogeneity  problem is  discussed within the same context and related to Somigliana dislocations, and  in the limit  to the interstitial atom.

Crack Initiation with UMAT

Dear all,

      I want to model crack initiation and propagation for a user defined material, using Abaqus. When I try to model , I get the following error:


when I take out critical damage initiation, the model works fine; which means that it doesnt allow me to couple UMAT with crack initiation. Does anyone know how to handle this problem?

All the best,



CISM Course: Plasticity and Beyond

Dear all,

please find information about the 5 day - course on Plasticity and Microstructures at CISM Udine, Italy.

The link is:

Flyer is attached.

Best regards,



Original post from CISM website:

Plasticity and Beyond: Microstructures, Crystal-Plasticity and Phase Transitions

Plotting the Johnson-Cook strength model

I'm trying to plot the stress-strain curve described by the Johnson-Cook strength (and eventually damage) models. The strength model is defined as:

σ=[A+Bεn][1+C ln(ε_dot*)][1-T*m]

where A, B, C, n, and m are material constants, ε_dot* is the non-dimensionalized strain rate, and T* is the homologous temperature where T*=(T-T0)/(Tmelt-T0)

To calculate the thermal softening (term in the last bracket of the J-C model), I need to determine the increase in temperature related to an increase in stress (and strain). I'm using the following equation:

Variable Elasticity (Young) Modulus

Free Tags: 

I need to simulate a sheet forming but I must consider the variation of Young modulus with plastic strain.

Has anybody tried this? How can I implement a function for this? I have never worked with UMAT / VUMAT.

Thank you. 

Surface mediated plasticity in sub-10-nm-sized gold crystals

Nature Communications 1, Article number:144 | DOI:10.1038/ncomms1149

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:

Falkingham P.L., Bates K.T., Margetts L. and Manning P.L. (2011) "The 'Goldilocks' effect: Presevational bias in vertebrate track assemblages", Journal of the Royal Society Interface, accepted for publication. Impact factor 4.241.


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