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Potential surface and yield surface


Would you please tell me the basic difference between potential plastic surface and yield surface with a physical meaning, if possible. I know that if both the surfaces match, then it is associated flow-rule, otherwise it is a non-associative flow rule.

I know that this is a very basic question, but I am facing difficulty in completely understanding it.


Thanks in advance.


tigerofmahdi's picture

Temperature dependent material

Hi Dears and of course metallurgist.

Who person can tell me the relation between the material properties such as Yang modulus, density, thermal coefficient etc. and temperature??

All of properties follow from one relation to temperature? For example if E(T)=Ea+100T then the density and another property have the same relation like P(T)=Pa+100T ??



tigerofmahdi's picture

Elastic wave propagation

Hi Dears:

Who works on Elastic wave propagation and its reflection? How I can fine the formolations of elastic wave after its reflection from arbitrary boundaries ?? Can you intruducing any refrences to me??

qieasa's picture

[Help] How to define a variation of volume during a phase change in Abaqus?

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Dear friends,

I am a beginner in using Abaqus. Now I am doing a project which calls for a simulation of the phase change probleme (two demensional Stephan problem).

I did a simple simulation with water, more prescisely a water slab of 10 C at the left I impose a temperature -10 C, so I got the results of the profils of temperature in every increment of time. 

Jianliang Xiao's picture

Professor John Rogers elected to NAS

Professor John Rogers, Swanlund Chair Professor of Department of Materials Science and Engineering, University of Illinois at Urbana-Champaign, was recently elected to the National Academy of Sciences. Congratulations to John!

Here is the link to the NAS press release:

Rui Huang's picture

Ken Liechti will receive the 2015 Adhesion Society Award for Excellence

Professor Kenneth M. Liechti of the University of Texas at Austin has been selected to recieve the 2015 Award for Excellence in the Adhesion Society. The Adhesion Society’s Award for Excellence, sponsored by 3M, is the Society’s premier award for outstanding achievements in scientific research relating to adhesion.

Rui Huang's picture

K. Ravi-Chandar will recieve the 2015 Drucker Medal

Professsor Krishnaswamy Ravi-Chandar of the University of Texas at Austin has been selected to receive the 2015 Daniel C. Drucker Medal, one of the ASME society awards for achievement.

Call for Gallagher Young Investigator Nominations

The US Association for Computational Mechanics (USACM) is calling for nominations for the Gallagher Young Investigator Medal.  The description from the USACM Awards page reads:

Weijie Liu's picture

How to understand the oscillating behaviour during calculating stress

Dear all,

Why we have an oscillating behaviour when calculating stress in FEM?

I saw the sentences in the paper:

'Another reason is that stresses are less accurately predicted than strains in FE simulations. Calculated stresses do also show a tendency for an oscillating behaviour, especially in dynamic explicit simulations.'

'stress is less accurate predicated than strain' is easier to understand, but I was wondering the existence of oscillating behaviour for calculating stress.


Any comments are welcome.

tigerofmahdi's picture

weighted residual

Hi dears:

why weighted residual is equal to zero ?? why integration of residual multiply by a weight function, over it's domain is equal to zero??

Anisotropic stiffness of isotropic material

Dear colleagues,


Consider a simple non-linear elastic material with stress given as

σ = D(εdev) εdev + B εiso

where εdev is the norm of εdev, D is a function of εdev and B is constant. The material is isotropic since the principal directions of  σ and ε will coincide.

If we differentiate σ wrt ε to obtain the material stiffness the form of the stiffness tensor will be

Professor Wei Lu Received the 2014 Gustus L. Larson Memorial Award

Professor Wei Lu received the 2014 Gustus L. Larson Memorial Award. This award was presented to Dr. Lu by the president of ASME, jointly with the president of Pi Tau Sigma, during the 2014 ASME International Mechanical Engineering Congress & Exposition. 

Pradeep Sharma's picture

Reminder (Deadline, Dec 5th): Call for Nominations for the Eshelby Mechanics Award for Young Faculty

It is my pleasure to solicit nominations for the "Eshelby Mechanics Award for Young Faculty". This award, launched in 2012, is given annually to rapidly emerging junior faculty who exemplify the creative use and development of mechanics. The intent of the award is to promote the field of mechanics, especially among young researchers. While interdisciplinary work that bridges mechanics with physics, chemistry, biology and other disciplines is encouraged, the ideal awardee will demonstrate clear inspiration from mechanics in his/her research.

Ted Belytschko passed away

It is with great sadness that we post this entry.  Ted Belytschko passed away early this morning, 15 September 2014.  

Non Linear Analysis Ansys

When Working on Ansys Non Linear Static Structural Analysis, I couldn't comprehen while defining and assigning material properties to corrosponding bodies.

When I give different random values for density in Engineering Data and runing the jobs parallely the results look SIMILAR for all the independent values, I couldn't fish out on what basis do the software is giving out results.

Lagrange Multipliers in Multi-body Finite Element Code

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I'm working on a Multibody dynamics code using the finite element method to simulate the behaviour of flexible beams (using this paper if anyone is interested/ it is relevant). I'd like to model joints, and as I only need spherical friction free joints I believe this should be easy using Lagrange multipliers.

James R. Rice will receive the 2014 Theodore von Karman Medal

Professor James R. Rice, of Harvard University, will receive the 2014 Theodore von Karman Medal.  Here is a link to an announcement.

Lallit Anand will receive the 2014 Drucker Medal

Lallit Anand will receive the 2014 Drucker Medal.  There will be a symposium in his honor at the International Mechanical Engineering Congress & Exposition, 14-20 November, Montreal, Canada.  See you there.

Abaqus dynamic explicit

Hi all,


Would you please let me know if it's possible, how to identify the length of mesh, time period of step, factor scaling, ... of an Abaqus dynamic explicit problem.

Thanks in advance, 

Stress Recovery in XFEM

Hello all,

I am new to imechanica so pls forgive me if I make a mistake.

I have a coplue of doubts while recovering stresses from XFEM.

My problem statement has an inclusion with some eigen strain, embedded in  an infinite matrix. I have solved the problem for displacements using XFEM. I need to get the stresses at a point close to the interface.

The 2nd Sandia Fracture Challenge is here!

update, 7/24/2014: The information packet ("SFC2-challenge-v5.ppt") is no longer attached to this post (iMechanica has a file size limit of 1 MB, so we can not attach the 6 MB file). IF YOU WOULD LIKE THE INFO PACKET, PLEASE E-MAIL ME, and copy Dr. Sharlotte Kramer, If you have an older version of the information packet, please also e-mail for the newest (v5) info packet.

We intend to send the shear calibration data to all those whose e-mail address I have by August 1st (sorry for the delay!).

Source for Mooney-Rivlin coeffcients for silicon rubber

Hi everyone,

I am trying to simulate the behavior of a silicon rubber membrane which is being compressed due to the displacement od an additional part which is bonded to it. I want to model the membrane as a Mooney-Rivlin hyperelastic model. Can therefore anyone provide me with a source giving C10 and CO1 coefficients for silicon rubber?

Any help will be appreciated,



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