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Problem with defining corner BC/constraint

Hello all,

I'm trying to model the buckling of a shell structure under thermal load.

The structure is square-shaped.

The left edge must be kept straight. To achieve that, I applied MPC Tie Constraint for its nodes.

The bottom edge must be fixed so that the BC applied at its nodes was U1 = U2 = U3 = 0.

Temperature is applied as a predefined field.

However, when I run the simulation the corner that connects both edges deforms very strangely which makes me question how to model it.

I appreciate any input. Thanks.

Lumped heat capacitance matrix and temperature oscillation.



When I was reading the Abaqus manual about transient analysis in thermal field, I found a sentence that says 'In transient analyses using first-order elements the heat capacity terms are lumped, which eliminates such oscillations....' (Transient analysis in Abaqus Analysis User's Guide 6.5.3). 

I think that this 'oscillations' is related to not only explicit time integration, but also implicit time integration (such as Backward Euler method).

Piezoelectric Stack Modelling in ABAQUS

How does one model a piezoelectric stack Actuator in ABAQUS?

Abaqus User defined Routines

I have been using an Abaqus dll created using a user-defined routine. Things work well on a serial case. The issue comes when I try to use it in parallel. I am trying to do this on windows 7. The error I get is

forrtl: severe (59): list-directed I/O syntax error, unit 12,

in Fortran I/O but I do not get this error when I run the simulation serially. Any ideas will be helpful.



Abaqus Python : reading odb file for field frame data


I am running a python script to do some post processing on Abaqus odb file. While running it on Abaqus/Explicite output file I found it was taking more than usual time. And after timing the run I got the surprise that the most time consuming thing what just to read the time value for each frame. I have the script below.

def main():


Emilio Martínez Pañeda's picture

New release of Abaqus2Matlab: GUI, reading .odb and much more!

A2M GUI interface 

Dear imechanicians,

A new version of Abaqus2Matlab has just been released and I hope that it is of interest to you.

This new release constitutes a very significant step forward in the development of this well-known software to connect Abaqus and Matlab.

Question reg ABAQUS-VUMAT and Updated Lagrangian formulation.

Hello all,

I am working on implementing a viscoelastic constitutive model from a hyperelastic stored energy potential (for finite-elasticity) and a dissipation potential (for the viscouls evolution). The elastic constitutive relation, hence derived from the stored energy potential is rate-independent and it is expressed as T(Cauchy's Stress) = f(B), where B is the Left-cauchy green deformation tensor.

The evolution equation is derived out in an objective rate form, which I am integrating over time using a 2nd order accurate explicit method.

My question:

User-defined amplitudeS using UAMP subroutine in ABAQUS

Choose a channel featured in the header of iMechanica: 

Dear all,

I need to use two user-defined amplitudes in my model in order to apply two separate variable-dependent forces on two separate partitions. I have been struggling with this for long now, and the documentation says "There is one exception in Abaqus/Standard: only one solution-dependent amplitude (used for superplastic forming) can be active during each step."

I see the possibility of defining multiple solution-dependent amplitudes in CAE, but in UAMP the variables such as ampValueOld, ampValueNew, etc. may take only one value. 

Frank Richter's picture

Bone remodeling: Komarova model

Dear Community,

I make a code public for bone remodeling, using the Komarova model. It was developed by me alone. I provide the code as is, without warranty.

The agreement between my data and the ones from a reference are very good for fixed loading, but deviate for a more intricate loading. Lacking access to Abaqus with a Fortran compiler, I am at present unable to pinpoint the cause for the discrepancy between my data and data from the reference. The code can serve as a starting point and I give directions how to identify the cause for that discrepancy.

Abaqus element surface.

Dear all,

I'm using abaqus to build a spherical model, which applies C3D8 linear brick element.  I output the connectivities of one element on the surface and the corresponding coordinates. 

For a linear brick element, the four nodes A,B,C and D on the same surface should lie on the same plane.  However, I got two different normals which are from A,B,C as well as A,B,D.

Is it reasonable or do I misunderstand something?



rajan_prithivi's picture

How does abaqus calculate deformation gradient in presence of thermal expansion

When we only have mechanical loading, I understand that abaqus calculates the total deformation gradient using F = I + partial_U/partial_X and U = N_i*U_i where U_i is the displacement at the nodes  and N is the shape function .

If I use a thermal expansion in addition to mechanical loading , Does abaqus give the total deformation gradient incorporating both mechanical loading and  thermal expansion ?
F = I + partial_Utot/partial_X ; Utot = U_mechanical + U_thermal

Frank Richter's picture

reflection and transmission coefficients in long elastic bars


Dear iMechanica Community,

I'd like to ask for advice on modelling reflection and transmission coefficients when two bars with different cross-sectional areas contact each other and are exposed to pulse loading.

I have modelled this process in Abaqus/Explicit as a two-dimensional simulation. The investigation was conveniently done as a parametric study, defining the lateral dimension as parameter. Both bars are slim (length 2 m, diameter 2 cm) and elastic.

Surendran M's picture

CFD simulation

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How to simulate air flow over 3d curved solids using Abaqus? I saw a conventional aerofoil model in youtube. Anything more general?

How to plot path length over time in Abaqus?

Dear Abaqus users,

I intend to plot the true distance of a path over all the steps of my simulation. 

One way is to create xy-data of an arbitrary output field over the true distance of the path, for each step.  Do you have any suggestion how I can get (true distance vs time) straightforwardly and faster?  

Thank you for your time and consideration 


Best regards,



Identifying fracture energy in ductile damage in ABAQUS

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I am trying to find out how to identify specified parameters of ductile damage material in its stress-strain curve in Abaqus. I created a one-element model with a dimension of 1x0.2x1 (0.2 in y-direction) and simulated a tensile test in y-direction with a displacement condition of 0.02mm.


Dear All, 

We are working on Equal Channel Angular Pressing (ECAP) project and we are trying to implement CPFEM with Abaqus UMAT, there are few examples online but we could not able to run them on abaqus 6.13 with any subroutine. Does anyone have any working subroutines on related subject?

Kind Regards


Yunus Emre Kulhan

ABAQUS: Access stress of integration point of elements during calculation

Hi all,

I'm using ABAQUS and UMAT for structural simulation. I used quadratic element (CPS4) with 4 integration points (IP).

During the calculation (which calling my UMAT), at each time step, for each element, I need to calculate the average stress of these IPs and produce a state variable for these IPs from this average stress. Then, I would need to update this state variable back to these IPs in that element. But as far as I know, the ABAQUS call UMAT for every IP and calculate everything within this current IP.

Emilio Martínez Pañeda's picture

Abaqus2Matlab: A suitable tool for finite element post-processing

A new piece of software has been presented that connects the well-known FE code Abaqus with Matlab. The source code, detailed documentation and a large number of tutorials can be freely downloaded from 

Some interesting applications are addressed in the associated journal article: (a pre-print is available at

Comparing performance of user subroutines in Abaqus

Dear Mechanics community,

My current research work is focused on simulation of NiTi stents.

I need to benchmark my UMAT subroutine against inbuilt VUMAT subroutine for SMA in Abaqus.

It would be great to have suggestions on how can I go ahead on this task (like typical benchmark analysis, simulation of CAD models etc.,).

The basic idea is to analyse the limits of both the subroutines.

Warm Regards,

CompMech enthusiast...

Calculating material jacobian matrix for ABAQUS UMAT subroutine

Hello everyone, 


I found that there is no comprehensive topic about how to calculate material jacobian matrix for UMAT while it's one of the most complicated and important parts of writing a subroutine and a lot of the researchers deal with it. 

I think it would be great if experts share their sources and experiences here for all. I personally, try to provide the basics and essential materials as well. 

Here is an essential available PDF on Imechanica:

Free Lunch & Learn Seminar with Simpleware and SIMULIA, Jan 17th, CA

Date / Time: Tuesday, January 17, 2017 / 10:00 am - 3:00 pm

Venue: Dassault Systemes | 3979 Freedom Circle, Suite 750 | Santa Clara, CA 95054-1249

Fee: The workshop is free, but pre-registration is required as seats are limited.

Language: English

Register here:

rajan_prithivi's picture

creating a perfect spherical hole in an orphan mesh (Abaqus)

Hello All,

I have an 3D orphan mesh (Abaqus)  that I obtained from the Gmsh software. I would like to insert a perfect spherical hole in that mesh.


I selected all the elements inside a sphere and deleted them but i am getting a very coarse surface, look at the figure attached

Is there a way to create a perfect spherical hole in a 3D Abaqus mesh ( I do not have the part geometry)  ?


I thought something like,  smooth the inside of the surface of the mesh deletion, but I donot know how to do that.


Properties of cohesive surface on cohesive elements

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Hello everyone,

I have a simple ABAQUS model with cohesive surface and I want to create a comparable model with cohesive elements instead of the surface. Applying the same properties onto the cohesive elements does not give me the desired results. Then I read somewhere that the properties cannot be applied on the elements directly the same way.

So how do I apply my interface properties onto the material of the cohesive elements? I thought that I should consider the thickness of the elements, but still until now I have not succeeded yet...

Thank you in advance.

Which theory Abaqus' Contour Integral for the determination of SIFs is based on?

I am actually using Abaqus' Contour Integral for the determination of stress intensity factors. But I do not know, which theory it is based on. Is it the same like the path-independent determination of J integral? Or is there a difference?

Modeling and Simulation Engineer Position at Schlumberger India Engineering Center

We, Schlumberger India Technology Center Pvt. Ltd (Located at Pune, India), looking for fresh graduates for our Modeling and Simulation Group. The candidate should be completed or on the completion of his/her Ph. D. in the area of Applied Mechanics (Structural/Fluid) with a strong academic background. As a mechanical modelling and simulation engineer, he/she will execute and lead analytical simulation effort, with the FEA/CFD modelling techniques, for complex mechanical parts/assemblies and complex physics. The details of the job description will be communicated later. If you are interested kindly send your resume on


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