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implementation of nonlinear fem

Hello everybody,

 In the implementation of nonlinear FEM, there are two ways, namely the Voigt notation and the full matrix notation. Obviously, using Voigt notation, one only stores vector instead of matrix. So, by using the symmetry of the Cauchy and second Piola Kirchhoff stress tensors, it is always possible to implement nonlinear FEM using Voigt notation. 

 So, my question is why the full matrix implementation still exists? It is mentioned in the famous book of Ted Belytschko. Only due to historical reason or there are some advantages? 

ANSYS ANIMATION problem: how can I animate the results of a loop (of element death over time)?

I previously posted asking for help with writing command line code to model melting via element death over time.  Biswajit kindly helped me write a loop to kill off any "melted" elements.  Now I would like to animate the results.  I would be very grateful for any suggestions on how to save results from the loop calculations and then animate them.  My aim is to get an animation that shows temperature contours evolving as well as elements disappearing as they achieve a specified temperature.  I am a new user and would find detailed suggestions most helpful.  

vicky.nguyen's picture

Faculty Position Open at The Johns Hopkins University

The Johns Hopkins University, Department of Mechanical Engineering, invites applications for a full-time tenure-track faculty position in the general area of mechanics and materials. Modeling and simulations are of particular interest, but all outstanding candidates will be considered.

Ban.NguyenVan's picture

Ask for contact problem in ABAQUS?

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Hello all,

I'm modeling the railways track system, in which the rail wil be  affixed to the cross tie by Fastening to against the vertical force. 

Now instead of modeling the Fastening, I would like to model the contact between Rail and cross Tie in ABAQUS. I have try surface to surface; surface to node and also tie constrains, but somehow  the results are not reasonable (not agree to experiment result). I thinks the problem is contact properties.

So are there any one can helo me on the problem?

PDF position at the University of New Brunswick, Canada

A post-doctoral position is available in the area of material modeling of composite at the University of New Brunswick, Fredericton, Canada. Particularly, expertise is sought in finite element simulation of damage/fracture and thermomechanical properties of fiber composite. Experience in multiscale finite element modeling of fracture and damage behavior of composite materials is required.

Please contact Dr. Zengtao Chen at the University of New Brunswick for more information. Email:, phone: 1-506-458-7784.

Teng Li's picture

Symposium on Materials and Devices for Flexible and Stretchable Electronics at 2009 MRS Spring Meeting

Call for papers

2009 MRS Spring Meeting, San Francisco, CA, April 13-17

Symposium PP: Materials and Devices for Flexible and Stretchable Electronics

Abstract Deadline: 3 November 2008

Dynamic fracture toughness of PMMA decreases with crack velocity

Dear Alls;

I am loking for the paper which said the Dynamic fracture toughness of PMMA decreases with crack velocity under impact loading, but after crack starts propagation, crack velocity is a decreasing function with crack propagation length.

So, if you know the paper which related to that problem, Could you please show me its title?


Thank you very much,

Best Regards,


Glass thermal stress and fracture

I have an investigation on glass fracture in fire.

I have a fortran program and it can calculate the thermal stress with steady-state temperature and force load using finite element method, Now I want to change it to transient temperature and force load.

I wonder which method should be taken? I'd like to calculate the fracture at last.

Please help me! 

Thank you very much.

you can email to me : or

QS Wang



I am trying to model a tube closed at the two ends by 2 plates.  The cavity enclosed by the two plates and the tube is filled with fluid.  I fix one end and apply a force to the other end.  The tube is a very flixible material and thus all the force should be present as a pressure detected by the fluid.

 When I try to do 2-way-FSI in ANSYS WB with CFX, all the force is taken up by the tube and none by the fluid.  any suggestions?

Active Materials for Medical Devices

In conjunction with the 2nd International Joint Conference on Biomedical Engineering Systems and Technologies - BIOSTEC 2009


mesh refinement for eigen-properties of a cracked body

 It is a common technique in modelling cracked bodies with finite element method, to refine the mesh near the crack tip. It is mentioned in text books, mesh refinement is nessecary to increase the acuuracy of the computed stress intensity factor for the crack tip. Is meshrefinement nessecary for computing eigen-properties ( natural frequencies and natural modes ) as well as SIF? or eigen properties are not affected much by the near crack tip field?

An Elastic Plate Problem

It would be very helpful for me if somebody clarifies the following problem: Suppose a beam with simply-supported boundary condition is loaded by uniformly distributed load. One can find out the moment and shear force at any point on the beam by finding forces at the boundaries and then considering equilibrium of some section of the beam.

ramdas chennamsetti's picture

Why rate equations in Nonlinear FE?

Hi all!

I have a very fundamental question as follwing.

In Nonlinear FE formulations, we use rate equations (virtual work), but, in linear FE we don't use rate equations. Why???

Is it because Nonlinear solution is iterative solution (time may be virtual time).

I request those who have an idea to give some explanations.

Thanks in advance,


- Ramdas


Automobile engineering

can anyone give me the address of the best website about car where i can find everything about car--engine, transmission, ignition..... everything, from basic to advanced knowledge, from old to new technologies. free or paid site.

Yuri Estrin's picture

Postdoctoral Fellowship at CSIRO, Melbourne, Australia


Applications are invited for an OCE Postdoctoral Fellowship in the research area "Local Property Enhancement in Light Alloys". The appoitment, for a period of three years. will be with the Light Metals Flagship and CSIRO Division of Materials Science and Engineering.

D.Rittel's picture

Adiabatic shear banding

The subject of adiabatic shear banding is quite classical and the main assumption is that it consists of  structural/mechanical instability in which the thermal softening effects play a dominant role in the generation of the band (Zener-Hollomon).

I would like to focus on the phase that precedes global failure, namely up to the peak stress or strain) at which the material starts to exhibit negative strain hardening.

A TEM postdoc position is available at Sandia National Lab.

Job Description: The CINT Science Department is searching for a postdoctoral appointee to pursue research in the area of leading-edge electron microscopy of nanomaterials and their properties. The successful candidate will work closely with the staff scientist heading electron microscopy research activities at CINT on topics related to the structural, mechanical, thermal, and electrical properties of modern nanomaterials.

Journal Club Forum for October 15th: Experimental Solid Mechanics at the Nanoscale

Browsing through past themes, I realize that this is the third time the topic of experimental mechanics at the nanoscale has been highlighted in the jClub forum. There are many problems that require experimental research at the nanoscale that we can do this a few more times without being repetitive. I would like to focus this discussion on the fundamental issue of friction.

Faculty Position in Sustainable Material Synthesis and Characterization at the University of Pittsburgh

The Department of Civil and Environmental Engineering at the University of Pittsburgh invites applications for a faculty position effective September 1, 2009. The search is open to all ranks depending on qualifications and experience. 

Li Han's picture

Determining the elastic modulus and hardness of an ultra-thin film on a substrate using nanoindentation

Abstract – A data analysis procedure has been developed to estimate the contact area in an elasto-plastic indentation of a thin film bonded to a substrate. The procedure can be used to derive the elastic modulus and hardness of the film from the indentation load, displacement, and contact stiffness data at indentation depths that are a significant fraction of the film thickness. The analysis is based on Yu’s elastic solution for the contact of a rigid conical punch on a layered half-space and uses an approach similar to the Oliver-Pharr method for bulk materials.

Teng Li's picture

iMechanica: 9000 registered users, 30,000,000+ web hits

The number of registered users of iMechanica reached 9000 on 13 October 2008, after two years and one month since the website launch. The total number of posts is 4036, the total number of comments is 8888, and the total web hits is estimated to be more than 30,000,000.

Hosted at Harvard School of Engineering and Applied Science and maintained by a growing number of volunteers, iMechanica aims

David J Unger's picture

J-Integral Elliptical Hole (Plane Stress) Perfectly Plastic Material

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The fracture mechanics community may be interested in a new evaluation of a J-Integral for a fundamental geometry:  an elliptical hole in a perfectly plastic material under the Tresca yield condition for plane stress loading conditions. The analysis is exact and involves only elementary functions.  This makes the problem suitable as a classroom example or as a homework problem for a graduate level course in fracture mechanics.  See J. Elasticity (2008) 92:217-226.

Shear Locking vs. Membrane Locking?

Could anyone briefly explain what is the difference between "Shear Locking" and "Membrane Locking". Does this apply to plain strain elements?

 Thank you.


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