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Volumetric Swelling

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Hello,

I am trying to increase the volume of a material as a function of temperature, this cannot be included in the thermal expansion coefficient as in this case a reduction in temperature does not cause the volume to reduce by the same amount it had increased. Any advice would be appriciated.

Thank you kindly.

2 Replies Last Post Oct 7, 2009, 9:38 a.m. EDT
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)

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Posted: 1 decade ago Oct 7, 2009, 8:58 a.m. EDT
Hi

it depends what you are trying to do, I'm not sure I get it correct, but if you do not use the thermal expansion "alpha", with a little care you can use it for a non linear "swelling" by defining a function and set your alpha (normal material expansion) to this function. This is the way the material detabase define non-linear material.

There are quite some text in the help/documentation about interpolated data functions

Does it help ? Hope so

Good luck
Ivar
Hi it depends what you are trying to do, I'm not sure I get it correct, but if you do not use the thermal expansion "alpha", with a little care you can use it for a non linear "swelling" by defining a function and set your alpha (normal material expansion) to this function. This is the way the material detabase define non-linear material. There are quite some text in the help/documentation about interpolated data functions Does it help ? Hope so Good luck Ivar

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Posted: 1 decade ago Oct 7, 2009, 9:38 a.m. EDT
Hello,

I did consider including this swelling in my expansion coefficient, but I would have to include logical statements, which would change the equation dependent on some other variable I have in my model.

e.g.

alpha = (if stage=1 then a + b*T + c*T^2, if stage=2 then d+ e*T + f*T^2)

this is to ensure the volume does not decrease with temperature, the same way it increased, giving a hysterisis graph of material swelling.
Hello, I did consider including this swelling in my expansion coefficient, but I would have to include logical statements, which would change the equation dependent on some other variable I have in my model. e.g. alpha = (if stage=1 then a + b*T + c*T^2, if stage=2 then d+ e*T + f*T^2) this is to ensure the volume does not decrease with temperature, the same way it increased, giving a hysterisis graph of material swelling.

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