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temperature dependent material properties

Posted 20.05.2014, 08:09 GMT-4 Heat Transfer & Phase Change 6 Replies

Michael Cloots
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Hello everybody

for my modell i am working with two materials, which have different thermal properties up to the melting point.
material 1 = bulk material;
material 2 = powder

Both materials have the same melting point. During the heating phase the temperature evelution in both materials is completely different.

But when the powder reaches the melting point, its material properties should change to the properties of the bulk material, independent of the following temperature.

Does have anybody an idea how to realize this in comsol?

My status: beginner

Thanks a lot

Michael
6 Replies Last Post 20.05.2014, 11:41 GMT-4
Pieter Westerik
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Posted: 1 decade ago 20.05.2014, 11:03 GMT-4
Hi Michael,

Maybe you can put
if(T<{Tmelt},{powder property},{bulk property})
for all the relevant material properties?
Hi Michael, Maybe you can put if(T
Michael Cloots
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Posted: 1 decade ago 20.05.2014, 11:10 GMT-4

Hi Michael,

Maybe you can put
if(T<{Tmelt},{powder property},{bulk property})
for all the relevant material properties?


I think this doesn't work because during the cooling phase the temperature is smaller than the melt temperature and the material 1 (powder) would have again (with your condition) the properties of powder. But it should have the properties of material 2 (bulk material).

Thanks for your help

Michael
[QUOTE] Hi Michael, Maybe you can put if(T
Pieter Westerik
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Posted: 1 decade ago 20.05.2014, 11:27 GMT-4
Ah sorry, I missed 'independent of the following temperature' in your first post. Is the temperature just raised once and then lowered or is it going back and forth between molten and solid states?
Ah sorry, I missed 'independent of the following temperature' in your first post. Is the temperature just raised once and then lowered or is it going back and forth between molten and solid states?
Michael Cloots
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Posted: 1 decade ago 20.05.2014, 11:29 GMT-4
it is just one cycle....
heating --> cooling... finish ;-)
it is just one cycle.... heating --> cooling... finish ;-)
Henrik Sönnerlind COMSOL Employee

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Posted: 1 decade ago 20.05.2014, 11:37 GMT-4
Hi,

This is a type of question which appears now and then. You can solve the problem using the following method:

Introduce an extra ODE for an 'indicator variable' (lets call it 'q'). Give it the initial value 0, and the equation



The variable q will then jump from zero to a nonzero value once Tmelt has been exceeded, and you can use an expression like

if (q==0,early_data,later_data)

to switch the material properties.

Regards,
Henrik
Hi, This is a type of question which appears now and then. You can solve the problem using the following method: Introduce an extra ODE for an 'indicator variable' (lets call it 'q'). Give it the initial value 0, and the equation [MATH] \frac{dq}{dt} = (T>Tmelt) [/MATH] The variable q will then jump from zero to a nonzero value once Tmelt has been exceeded, and you can use an expression like if (q==0,early_data,later_data) to switch the material properties. Regards, Henrik
Michael Cloots
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Posted: 1 decade ago 20.05.2014, 11:41 GMT-4
Hello Hendrik

thank you very much...
i will try to implement your suggestion

With warmest regards

Michael
Hello Hendrik thank you very much... i will try to implement your suggestion With warmest regards Michael

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