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Panos Efthymiadis's blog

Combining UMAT with XFEM

Hi all,
I 'd like to ask whether anyone has applied XFEM for a user-material (UMAT). What is the process to do that? Could anyone provide some advice, documentation or guidelines?

All the best,
            
Panos

p.s. I 've heard that a UEL code is needed to couple XFEM with UMAT.

Crystal Plasticity Modelling

Hi all,

     I want to set up a critical shear strain - normal stress criterion, in UMAT by prof. Huang. For the strains it is easy to get a critical strain along a slip plane; but for the stresses the notation is quite weird. It is not the same! See below:

C       Array STATEV:

Damage modeling with UMAT

Dear all,
      I am using a Abaqus modeller with fortran subroutines. I have written a UMAT subroutine and now want to apply some damage initiation-evolution criteria. But I get the following error: a damage initiation property was used with a user material.
I wanted to apply the criteria externally from the subroutine.. How can I go through with this problem? I tried different criteria (stress and strain based) to check if it is a matter of the output variables... No result..
Is it the case that I should have my damage code within UMAT?
All the best,

Crack Initiation with UMAT

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

 

Voronoi tesselation

Dear all,

      I would like to ask you how is it possible to import into abaqus a 2-D or a 3-D Voronoi structure. so far I ve been able to create my grains into Matlab or fortran but I dont know how to import them into abaqus.

All the best,

    Panos

Fatigue

Dear all,

       I would like to ask you, how is it possible to simulate fatigue in Abaqus. I have created my loading. But if I run it as it is it will never reach a critical value, so you could say there is no damage evolution. Is it the only way is to apply some type of hysteresis loop evolution and say that after some cycles the hysteresis loop changes?

Any advice is more than welcome!

Regards,

            Panos

Fatigue

Hi,

 I d like to ask you how could fatigue loading be modelled in cae. I know that you can set up the load as a sin function with min and max values. But where do you set-up the total nr of cycles? Is at the step part and where exactly?

And another question could anyone provide me with details of the input file for the hysteresis loop, where the stess nd strain resistance of the material drops after certain cycles..

 

Regards,

   Panos

Extrude a solid section

Hi all,

       I am having some troubles with the extrude command in Abaqus cae. I have modeled my sample as a 2-D geometry and now I want to move to 3-D for the same section. But I am having trouble extruding my 2-D section. It seems to me very weird and far to complicated the extrusion process in abaqus for such a simple task...

Thank you,

          Panos

Import geometry into Abaqus

Hi all,

             I would like to ask how is it possible to import  a sketch or a part into Abaqus without using any other software needed, like CATIA, PARASOLID etc... Currently I am using Matlab to create my geometry. What I obtain is my exact geometry in terms of points given by x,y and z coordinates in txt format or inp format. But still struggle to import my geometry into Abaqus. Any help, more than welcome...

Best regards,

              Panos

UMAT code for crystal plasticity

Dear all,

           I would like to ask you something about prof.
Huang's subroutine. I want to verify the code, by using published
stress-strain data. But when I am plotting my stress -strain curve I am
always getting a straight line instead of a curve that shows the hardening effect. What could be a reason for this problem?

         Regards,

         Panos

p.s. I am using a single crystal, single element, and only modify the crystal orientation

Import a plot from Matlab into Abaqus

Dear all,

       I would like to ask you how is it possible to import into Abaqus from Matlab a plot for the geometry of my specimen.How should I save my workspace and what changes should I make to the file to be an input file for Abaqus?

Regards,

          Panos

Voronoi tesselation-grain size and orientation

Dear all,

         I am trying to produce a metallic grain structure  using Voronoi. I am currently using Matlab. Does anyone know how I can control the area of the polygons-grains (impose a Gaussian distribution)? And another point is how can I assign the grain orientation for every polygon?

Regards,

           Panos

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