Using Strain as variable for a user define function

Numerical methods and mathematical models of Elmer
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Matthew
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Using Strain as variable for a user define function

Post by Matthew »

Hello everyone,

I have a problem which requires the use of the trace of strain, E (which is used to find the volume changes) in a user define function that calculate the change of concentration within a solid material. Can you guys give some idea on how can I determine the Tr(E) and use it in a user define function?

My idea now is to write this in .sif file in Body Force before sending it in procedure to calculate the concentration changes:

Body Force 1
Name = "BodyForce1"
Heat Source = Variable Strain
Procedure "..." "..."
...
End

Is this possible? Or do I actually need to recalculate the strain by using the displacement and local coordinate variables and send it into the Procedure to calculate strain and then Trace of strain?

Thank you in advance,
Jamil
Matthew
Posts: 31
Joined: 19 Jun 2014, 18:22
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Re: Using Strain as variable for a user define function

Post by Matthew »

Hello all,

It seems that my post has no reply from anyone. I will try to explain my problem simpler as given in the attachment below:

I want to create a user define function to calculate the concentration changes, but how can I calculate the trace of strain? Can anybody give some idea? My idea so far is to get the variable Displacement and local node coordinate but I hope there is another way to calculate it.

Thank you
Jamil
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raback
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Re: Using Strain as variable for a user define function

Post by raback »

Hi Jamil

The trace happens to be the divergence of the vector field. So apply the DivergenceSolver to your displacement field to get a new variable. See Ch. 41 in http://www.nic.funet.fi/pub/sci/physics ... Manual.pdf

Then use this for the concentration in a MATC expression as in

Code: Select all

$ns=1.23
$s0=4.56
Concentration = Variable "Div Displacement"
  Real MATC "ns*s0/(tx+ns)"
-Peter
Matthew
Posts: 31
Joined: 19 Jun 2014, 18:22
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Re: Using Strain as variable for a user define function

Post by Matthew »

Thanks Peter! You are my savior! I will try and let you know.

Thanks again.
Jamil
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