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fmpgomes
New member
Username: fmpgomes

Post Number: 2
Registered: 04-2010
Posted on Monday, July 05, 2010 - 01:05 pm:   

Hello, Mr. Nelson.
I found a problem in thermo-elasticity problem.
When Young Modulus is contant, it's ok. When is a function of time, I have numerical problem, I think.
Please, see this example. Where I'm wrong?

The example is: SeparateTens-R0.pde

Thank you for your attention.
Flávio Mamede

application/octet-stream
ThermoElasticity TimeDependent.rar (16.7 k)
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mgnelson
Moderator
Username: mgnelson

Post Number: 197
Registered: 07-2007
Posted on Monday, July 05, 2010 - 03:12 pm:   

The trouble is likely due to the fact that your time dependent Young Modulus starts at 0 and is very small for many timesteps. This means that your material is liquid or gelatinous like toothpaste... Then gets stiffer over time. We arbitrarily added 1000 to your time expression and the script runs okay.

If you really want to model something this soft, you may need to increase the accuracy, using ERRLIM in the SELECT section.
i.e. SELECT ERRLIM = 1e-5
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fmpgomes
Junior Member
Username: fmpgomes

Post Number: 3
Registered: 04-2010
Posted on Tuesday, July 06, 2010 - 09:14 am:   

Thank you for immediatly answer. I've tried like you said and runs just like before. Until four or five hours is ok, after the stress degenerate. Maybe for I'm using student version?

Another question, I would like simulate construction in 'layers'. The domain of problem is increased belong the time. I tried using "if" comand for thermical conductivity and other properties, equal zero before a time 'tz1'. Is it 'legal'?

Thank you.
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mgnelson
Moderator
Username: mgnelson

Post Number: 198
Registered: 07-2007
Posted on Tuesday, July 06, 2010 - 04:19 pm:   

1) When I run this on the Student version it completes in less than a minute.
application/octet-stream
SeparateTens-R0b.pde (11.3 k)


2) Simulating construction in layers can be difficult. Moving mesh and staged geometry are two possibilities, but each pose significant hurdles.

3) It is 'legal' to set properties to 0 before some set time, but you have to evaluate the equations and your system to determine if doing so makes sense or not.
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fmpgomes
Member
Username: fmpgomes

Post Number: 4
Registered: 04-2010
Posted on Wednesday, July 07, 2010 - 02:13 pm:   

Sr. Marek, Muito bom mesmo (very good !!!).
Thank you so much (BUT I DON'T KNOW WHAT YOU DID !!! Well, this is my work now.)
Thank you again
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mgnelson
Moderator
Username: mgnelson

Post Number: 199
Registered: 07-2007
Posted on Wednesday, July 07, 2010 - 06:12 pm:   

I took your time dependent expression (that was in your comments) and added 1000 :

E = 1000*(t-tz2)^0.80/(.080 + .024*(t-tz2)^0.80) +1000

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