[Geoqus] Erosion and surface modification with ABAQUS

[Peter Connolly]

Dear Vincent

I'm a little unsure excactly what you are trying to do here. My guess is
that you want to add or remove an arbitaty  set of elements (say ones
that exceed 1000m above sea level) and then remesh the top 2000m so that
you have a fine mesh near the surface for high density data extraction?
This should be doable, but unlike Kasper, I would suggest doing this
inside the FE run as a user subroutine. For the example above this would
handle the check for your "failure criterion (in my example Z>1000m) and
then remove the offending elements, then all the remeshing subrutines.
All doable, but will require a bit of work in fortran and C. 

With regards to Kasper's comment on moving nodes. As long as you know
which, where and how then I think the way to do this would be to move
the nodes (if necessary defined via a user routine) using the *BOUNDARY
option with the step definition. You could always make a dedicate
"passive" step with the nodal displacements to mimimise influence, if
that’s whats needed. Again, a user routine could handle the
identification of which nodes to shuffle.

If you know how your topography evolved and you all want to do is add
and remove elements in a predetermined order then yes, this should be
straightforward. You would have to collect the appropriate elements into
sets that are turned "on or off" in each analysis step. This would be
simple, and if you could use a really fine mesh for the near surface (ie
lots of RAM available or simple rheologies) then remeshing wouldn't be
necessary.

Hope that helps


Peter


-----Original Message-----
From:
geoqus-bounces+peter.connolly=gpi.uni-karlsruhe.de at lists.ruhr-uni-bochum
.de
[mailto:geoqus-bounces+peter.connolly=gpi.uni-karlsruhe.de at lists.ruhr-un
i-bochum.de] On Behalf Of Kasper Fischer
Sent: 16 September 2003 16:37
To: geoqus at lists.ruhr-uni-bochum.de
Subject: Re: [Geoqus] Erosion and surface modification with ABAQUS


Hi Vincent Godard,

first of all I want to welcome You to the Geoqus User Group. You 
will
find more about Geoqus on
http://www.ruhr-uni-bochum.de/geoqus

I am working with Abaqus for many years. During my Ph.D I have 
worked on
the same topic as You. The interaction of tectonic and surface
processes. It is possible to do the task You want to do, but it is a
little bit tricky. I used a feature of Abaqus to add or delete 
elements
during the calculation. This can be done very easily but one has to
figure out which element is affected. The main disadventage is 
that the
topography is very coarse since the size of the elements can't be 
too
small for a good performance. I have done this with the old 
version of
Abaqus (v. 5.8) and an IDL interface which read in the results of 
the
program to calculate the erosion and sedimentation (Golem by Greg
Tucker) and deciding on the results where to add or remove 
elements. The
current version of Abaqus (v. 6.3) has a scripting interface 
(python)
which might make things easier. If You want I can send You the 
IDL scripts.

A other choice would be to move only the surface nodes of the 
elements.
But I was not sure how this can be done in Abaqus and if it is 
possible
what happens to internal stress and strain values of the affected
element. Maybe somebody else has an idea or done this?

I hope that I could help You and I am looking forward to 
discussing this
topic here.

Kasper Fischer

--
+-----------------------------------------------------------------------
+
| Dr. Kasper D. Fischer
<kasper.fischer at ruhr-uni-bochum.de> |
| Ruhr-Universität Bochum
       |
| Institut für Geologie, Mineralogie und Geophysik
       |
| NA 3 / 174                        Tel: +49 234 3227574 
        |
| D-44780 Bochum                    Fax: +49 234 3214181 
        |
| Germany
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Vincent Godard wrote:

>Dear abaqus users,
>
>I am a phd student working on the interactions between tectonics and 
>erosion
>in orogens. One of my methods of investigation is 2D numerical modeling
of 
>the mechanical behaviour of the crust in relation with denudation
processes. 
>I am currently using the finite element code ADELI developed by Cherry
and 
>Hassani. 
>During my computations with ADELI I am confronted to a significant
reduction 
>of the size of the elements close to the surface of my model, due to
erosion. 
> ADELI can't perform mesh modification during the computation, so it is
an 
>important limitation to the lenght of the simulation.
>To solve this problem I am considering to turn to other finite element 
>softwares which can handle re-meshing during simulations, in particular

>ABAQUS (my lab already owns a licence), but before doing so I would
liketo 
>check if ABAQUS is really appropriate for the kind of modelisation I
intend 
>to develop.
>My question concerning ABAQUS is the following: is it possible (and
simple) to 
>remove or add material, at regular steps of the simulation, and
according to 
>user-defined laws?
>By removing or addition of material I just mean to change arbitrarily
the 
>position of the nodes that are defining the topographic surface of the 
>system.
>
>
>Thanks in advance for any advice,
>
>Vincent.
>
>  
>



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