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Constant cavity volume

Dear all,

I am trying to simulate cardiac contraction for a left ventricle. I want have to keep the cavity volume constant for my simulation.
I have read alot of documentations for tyre simulation in abaqus where they give a constant volume for internal air part but no success to find inp example to understand how you can give such boundary conditions.

Anyone can give me some hints where can I find such info?
Any help is very welcomed,

How obtain tension strain concrete(σt0) in damaged plasticity model in ABAQUS?

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How obtain tension strain concrete(σt0) in damaged plasticity model in ABAQUS?

hello engineers

i need help about concrete damaged plasticity

fo example :

if Compressive stress (Fu)= 51.2 MPa

and tension stress (σ t)=0.3 x 51.2^(2/3)=4.136

1)why (σ t) is 2.36 in picture(uploaded)?

2)what is tension strain ? and how? i cant understand.

i cant obtain εt = total tensile strain.

how obtain εcr ?

please help


Periodic boundary condition for RVE (Abaqus)

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i have a problem with the periodic boundary conditions. I want to implement the boundary condition for example

which i found it in the internet. The first equotion is u_facebuttom - u_facetop=0

So i know that we can do this with creating Constraint and selecting Equotion.

Problem in Extracting Mass Matrix in Abaqus

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I am trying to extract mass and stifness matrices of a simple beam using abaqus. The stiffness matrix works fine but when i requested the mass matrix to be exctraced the section in the ASCII related to mass matrix is empty. here my script:



Fixed Beam



how to calculate dispersion relation with ABAQUS ?

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  I wanna get the dispersion relation of acoustic crystals in ABAQUS, so far as I know, the frequencies can be obtained by applying different wave vectors in the IBZ, but I dont know how to opperate in ABAQUS, in what way can we simulate the wave vectors (or the cooresponding wave length) . By applying force or displacement, or acceleration ?

 Attacthed, should I model the whole structure or just the 1st BZ? If the 1st BZ is employed, should the periodic semmetric B.C. be considered in my model?

Any suggestion is appreciated! 

matlab code to create cohesive elements (or UMAT) in any 2D mesh

To use cohesive elements, normally user can add a layer of elements between neighbouring node pairs. This matlab code can help you to process that especially your FE mesh is irregular. The code, the initial .inp file and corresponding out put files are attached for a better illustration. The new generated cohesive elements won't cause any trouble in the element number. Also you can apply this code to generate new UMAT elements in mesh.


Opening for a Sr CFD/FEA Modeling Engineer at Medtronic

Here is the link:

Requisition ID:95396

Experience with phase-chase modeling or FSI is a plus.  

Please feel free to forward this posting to potential candidates.  Thanks!

Open Pit Model Abaqus

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Hi guys, 

I'm new on iMechanica, well at least writing on it, I've been working on a project about geomechanics in order to get my mechanical engineer university degree. The thing is that I'm felling like I can't get all this stuff together, so I would like to ask some questions about my project (Abaqus model of an open pit mining scenario):

Inconsistencies in Abaqus material


i wonder, how the inconsistencies in anisotropic hyperelastic material of Holzapfel-Gasser-Ogden form caused by Macauley-brackets and Heaviside step-function are beeing solved inside Abaqus (cf. Analysis User's Manual 22.5.3).

The Heaviside H(x) is beeing used to allow fiber reinforcement only on extension (in fiber direction). But analytical derivatives of the Macauley-bracket yield terms with H(x), and the Dirac-delta (infinite impulse at x_0).

Incompressibility in hyperelastic ABAQUS-Subroutine

Hello everybody,

in hyperelastic material models incompressibility is normally realised through Lagrange multipliers. But i can't find any instruction, whether i have to code that multiplier in a routine e.g. of type UHYPER, UANISOHYPER_INV or UANISOHYPER_STRAIN! The only instruction is on incompressibility (and hybrid element) flags, that have to be set, cf. Abaqus User Subroutines Reference Manual 1.1.20, 21 and 37.


Properties Lamina/Composite-Composite Layup using Abaqus

Hey everybody,

Actually I don't have the same thickness everywhere(that decreases little by little). I tried to part but it's not exactly the same thickness in the same part. Do you know if that can cause a problem? For example I have a scrap like that 10 mm+-2mm for thickness. I would think to fill in the composite layup like that Ply1 : 2 mm-Core : 6 mm-Ply2 : 2 mm

I use this occasion to ask you two more questions : 

ABAQUS model for viscoelastic peel dynamics

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Hi All,

making a cluster out of 6 computers for abaqus analysis


Hi everybody,

I have 6 desktop computers with the following specifications (all of them are the same):

CPU: 2 GHz, 2 cores, 8 Hyper Threading

RAM: 12 Gb

HDD: 500 Gb

Windows 7 (which I need to change to Windows Server with HPC pack)

I need to connect them together and make a cluster for abaqus analysis. I'm thinking about using Microsoft HPC pack since it seems to be an easy and user friendly option (I don't have any experience in that area).

ABAQUS Element Connectivity


I am trying to mesh the hollow sphere attachged using structured BRICK-8 elements. It turns out in order to have a structured mesh, I have to have 2 partitions such that four quadrants be generated.

What I only need from ABAQUS is the element connectivity. I do not need to solve any problem.

Export Mass Matrices in Abaqus



I have to export stiffness and mass matrices from Abaqus (dynamical simulation)

and I have been using the commands *Matrix Generate and *Matrix Output


I need to export the matrices for different  instants of time  (time intervals) and I have noticed that the entries

of the MASS matrices are not equal at different  time points.


Is that correct or should the MASS matrices be constant for a dynamical simulation?


many thanks

ABAQUS ALE gives random solution

Hi all,


I am simulating an excavation problem using the ALE method. If I rerun exactly the same input file only changing the duration of the last (long) step and compare results of the two analyses at the same analysis time I get significantly different results (e.g. up to 20% different settlements). I have tried changing the last step duration and I get different results again. How can this be? I am really worried about this behaviour!



Question about the tangential behavior of ABAQUS

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Hello everyone, I am using ABAQUS to study the tangential behavior (friction) at the interface between rock-machine. I know tangential behaivour simualtion is key for my model, I read the manual, but still have some puzzels, hoping you could help me, much appreciated in advance!


VUMAT general queries

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I am beginner in abaqus and I want to write a VUMAT for VIB method to simulate fracture, while writing VUMAT i encountered following problems 

1) For 2D plane stress problem how to calculate strainInc(*,3). It is increment for that step or value of strain till that step?

2) What is effect of that defination on answer I am getting?

Load Displacement curve for XFEM in ABAQUS

I am using Maxps Damage criteria for an XFEM crack for a three point bending case. I am using displacement loading on the specimen and wish to plot reaction load v/s mouth opening displacement. I would like to know how to obtain the crack tip opening displacement in ABAQUS. All the journal papers I read show a slump in reaction force after the crack starts to propagate. I plot the results and contour plots show me clearly that the crack has started to propagate. Please help.


Dear friends,

Recently my study is focus on bolt analysis on wheel hub assembly.

In simulation using Abaqus, I try to give a certain value of tightening torque on bolt to determine the clamp force.

But, I do not know how to apply the torque value on FE model.

Can we convert torque to became as an axial force?

Or, convert torque to moment?

software comparison (abaqus, ansys, flac, udec)

hi everyone, right now I am writing my reserach proposal and met some question really need your help. thank you in advance!


is there any command available to skip/suppress the element quality check, while running an analysis in abaqus?


H.Rahnama's picture

A UMAT Code In ABAQUS - Progressive Failure Analysis

I have written a UMAT code in ABAQUS. This UMAT degrades the young modulus of an isotropic elastic material at a point when the VonMises stress at that point reaches a specific value. It can be seen as a simple progressive failure code. I have applied this UMAT code to a Notched plate under uniform tension.

The problem is that exactly before the damage initiation, the ABAQUS/Standard diverges. I am sure that there is a very simple mistake that I just can't see!

Lance C. Hibbeler's picture

ABAQUS: nice colorbar ranges

I have produced a python script that automates setting up reasonable values in the ABAQUS/CAE colorbar, basically setting up Tecplot functionality.  After executing the script from File->Run Script, you have access to a function that you can call in the built-in interpreter,

>>> SetContourRange(minval, maxval)

Gatherin results from multiple points in the parametric study

Hi everybody! 

I am doing a large parametric study of a composite shaft. I am working with 5 variables and the number of simulations and data will be quite big. 

I would like to gather results automatically on a circumferential path around the shaft. (About 60 elements) 
Is it possible to do it with a "gather" command - I think that only one node/integration point can be defined at "gather" command. 

Has anyone already done something like that and how did you solve the problem. 


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