Third Asian Conference on Mechanics of Functional Materials and Structures (ACMFMS 2012)

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).

Qualifications:
1.    A PhD in solid mechanics, materials science, or mechanical engineering, or in a related area is required.

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.

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...

Regards,,,

Was

Hi,

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?

Thanks!

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

Soham

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. Therefore, in those regions we can determine the apportionment of the total GND density onto the individual slip systems.

In continuation of our work on yield surfaces

Part- 1 (http://imechanica.org/node/9016)

Part- 2 (http://imechanica.org/node/9073) and

Part- 3 (http://imechanica.org/node/9103) 

 
(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.

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:

A MATERIAL PROPERTY THAT IS NOT ALLOWED WITH A USER MATERIAL HAS BEEN SPECIFIED

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,

         Panos

(Paper to appear in Bollettino della Unione Matematica Italiana - Bulletin of the Italian Mathematical Union)

Luc Tartar and Amit Acharya

Global existence and uniqueness results for a quasilinear system of partial differential equations in one space dimension and time representing the transport of dislocation density are obtained. Stationary solutions of the system are also studied, and an infinite dimensional class of equilibria is derived. These time (in)dependent solutions include both periodic and aperiodic spatial distributions of smooth fronts of plastic distortion representing dislocation twist boundary microstructure. Dominated by hyperbolic transport-like features and at the same time containing a large class of equilibria, our system differs qualitatively from regularized systems of hyperbolic conservation laws and neither does it fit into a gradient flow structure.

In 2010,  Yves-Patrick Pellegrini published a paper in Physical Review B called

 Dynamic Peierls-Nabarro equations for elastically isotropic crystals.  with the abstract

Dear all,

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

The link is:

http://www.cism.it/courses/C1104/

Flyer is attached.

Best regards,

Mubeen

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Original post from CISM website:

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

June 27, 2011 — July 1, 2011

Coordinators:

Dear Colleagues:

We would like to invite you to submit an abstract for the upcoming 2011 Annual Technical Meeting of the Society of Engineering Sciences (SES 2011), to be held October 12-14, 2011, at Northwestern University in Evanston, Illinois (http://ses2011.org/).  The area of the minisymposium is "Mechanics of Crystalline and Composite Nanostructures", and we anticipate having a diverse and well-respected group of theoreticians and experimentalists give presentations on this subject.  Abstracts can be submitted by going to the following conference website:

http://ses2011.org/submit_abstracts.php

where our minisymposium is labeled 3.1.  We look forward to seeing you at Northwestern in the fall of 2011!

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:

ΔT=∫ Χ (σ/(ρ*cp)) dε

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. 

Hi everyone!

Evidence has accumulated recently that a high-capacity electrode of a lithium-ion battery may not recover its initial shape after a cycle of charge and discharge.  Such a plastic behavior is studied here by formulating a theory that couples large amounts of lithiation and deformation.  The homogeneous lithiation and deformation in a small element of an electrode under stresses is analyzed within nonequilibrium thermodynamics, permitting a discussion of equilibrium with respect to some processes, but not others.  The element is assumed to undergo plastic deformation when the stresses reach a yield condition.  The theory is combined with a diffusion equation to analyze a spherical particle of an electrode being charged and discharged at a constant rate.  When the charging rate is low, the distribution of lithium in the particle is nearly homogeneous, the stress in the particle is low, and no plastic deformation occurs.  When the charging rate is high, the distribution of lithium in the particle is inhomogeneous, and the stress in the particle is high, possibly leading to fracture and cavitation. 

In the post

 http://www.imechanica.org/node/9509

Sebastien Turcaud asks the question (my interpretation) of the characterization of  all possible residual elastic distortion fields on a given configuration (interpreted as the current configuration). If one in addition introduces a reference configuration then the deformation gradient w.r.t. this reference is known and depending upon how one defines 'eigendeformation' in nonlinear elasticity, corresponding eigendformation fields to the residual elastic distortion fields can be determined. Such eigendeformation fields can contain fields arising from plastic deformation, non-uniform thermal expansion etc.