Using interpolation to define temperature-dependent material properties

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Kaushik Biswas

Kaushik Biswas

December 30, 2012 5:53pm UTC

Using interpolation to define temperature-dependent material properties

Hi,

I am a COMSOL beginner. Trying to added a file containing temperatures and measured material properties and then utilize an interpolation function to define the temperature-dependent material properties. I have attached both the COMSOL file and the material property file. The first and third columns contain the temperatures and the 2nd and 4th columns are the corresponding measured properties. (I've attached the 'xlsx' file as I couldn't attached the 'csv' file I used in the model)

Any advice will be appreciated. Perhaps there already exist examples that I can follow to complete my model.

Thanks in advance.

KB

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Art

Art

January 2, 2013 11:15pm UTC in response to Kaushik Biswas

Re: Using interpolation to define temperature-dependent material properties

I had the same problem-temperature dependent structural and thermal properties. This is messy.

The first thing I would do would be to separate this table into two tables with only two columns for each table - independent variable (temperature) and dependent variable (ie, k or Cp).

Right click under basic properties or others (elasticplastic) - comes up with functions-click for interpolation. Comes up with an input request.

Name your function i.e. Cp, Cp1, etc at top row.

Below the blank table listing is the option to read in the list-this includes browsing. Browse for your file (all mine were txt in desktop.

Read in and save.

Very important for me and causing much misery was the fact that the independent variable, dispite all common sense, is not T (temperature) but mod1.T2.Where it says independent variable at the lower part of the interpolation table put in mod1.T2.

You can plot the table at this point. If it is correctly read in it will plot.

Now go back to basic variables say Cp. Type in name of function and units! in place of value.
i.e. Cp1(mod1.T2[1/K])[your units for Cp]-assuming Kelvin. Why this? I don't know. It just seems to work.

If mod1.T2 does not work, look at the error messages. Where "dependent variables" are listed will be the real name of your temperature variable. It is not immediately obvious what the name of the independent variable actually works in the program.


My tables are on another PC right now, but if you need one for clarification, I can get it.


--
Arthur Rupel

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Ivar Kjelberg

Ivar Kjelberg

January 3, 2013 7:17am UTC in response to Art

Re: Using interpolation to define temperature-dependent material properties

Hi

Check the names of the dependent variables in the main physics node. If you call in several physics with the same dependent variables, COMSOL calles them i.e "T", "T2", "T3" ... this holds also if you later delete one of the physics, the name remain. Therefore you might have either 2 "T"'s or its "just" that xyour temperature variable is T2 and not T as you thought

--
Good luck
Ivar

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Art

Art

February 6, 2013 9:32pm UTC in response to Ivar Kjelberg

Re: Using interpolation to define temperature-dependent material properties

The most merciful thing I can do in this probem is to give my own. mph file with the temperture dependent properties.

The geometry and mesh were extrracted as not necessary. This is 4.3a.

In the input procedures for this file

1. material-materials1-basic properties:
a) at basic properties I to double right clicked to get functions. Pick interpolation. You can read or input your info. You may need ony to rightr click once.
table was read in as a simple txt file but you can also use excell.

1st column temperature
2nd column material property
Note the temperature name under independent variable. For a structural thermal analysis this is what the program will see a the s temperate name. This is what caused me the most grief. For a long while I simply named this as temerature or degC (guessing). For other analyses name of temperature can be determined at end statement tof analysis (whether it runs or not).


If you have any questions, please ask.

Arthur Rupel
The function is given a name.

Under the material block this name is the name of your properites. Note how the units are described in this listing.
This is not obvious but is that format that was used and is successful.
t


--
Arthur Rupel

Attachments:   tempprop.mph  

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Shaojie Liu

Shaojie Liu

February 11, 2013 3:54pm UTC in response to Art

Re: Using interpolation to define temperature-dependent material properties

Hi!
I have some problems about input the temperature-dependent material properties.
What's your meaning of following words:

"Note the temperature name under independent variable. For a structural thermal analysis this is what the program will see a the s temperate name. This is what caused me the most grief. For a long while I simply named this as temerature or degC (guessing). For other analyses name of temperature can be determined at end statement tof analysis (whether it runs or not)."

I cannot open your file because of the later version.

Maybe I can attach my file here, i hope you know the problem.

My problems are about the how to input the "Value" (Materials>Aluminum>>>>material Contents)

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Ali Anderson

Ali Anderson

October 21, 2013 11:45pm UTC in response to Art

Re: Using interpolation to define temperature-dependent material properties

Just in case someone else is facing the same issue:

I had to use mod1.solid.T for independent variable. Function used: anlSi(mod1.solid.T[1/K])

Version: 4.3b.


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