Thermal expansion problem

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Hi, I was trying to build a simple model for the thermal expansion problem, the geometry I used was a 20mmX40mmX0.6mm rectangle, the physics used were solid mechanics and heat transfer in solid (multiphysics-thermal expansion 1). I studied the static state with initial temperature 461K. I've tried to change literally all parameters of the material (CTE, density, thermal conductivity, etc.), even changed the material from nylon to aluminum, but the results remailed the same. The total displacement always seemed rediculously large, 10^4-10^5mm on different axises, no matter how I changed the parameters. I wonder what is going wrong. Thanks.

WJ


4 Replies Last Post Jan 13, 2021, 3:25 PM EST

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Posted: 3 weeks ago Jan 5, 2021, 9:48 PM EST

Hi Wen Jiang,

It's better you attach your model file here in order for me to suggest apropreate answer to your question.

Regards, Rahul Shah.

Hi Wen Jiang, It's better you attach your model file here in order for me to suggest apropreate answer to your question. Regards, Rahul Shah.

Jeff Hiller COMSOL Employee

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Posted: 3 weeks ago Jan 6, 2021, 8:35 AM EST
Updated: 3 weeks ago Jan 6, 2021, 9:14 AM EST

Wen,

You say that the displacements are ridiculously large and don't change with the parameters. Are you saying that based on the way the displacements are rendered on screen, or based on the values on the colorbar? By default, deformations are displayed scaled in such a way that they are easily visible with the naked eye. Their actual magnitude can be read off the colorbar. You can also change the scaling factor manually to 1 if you do not want any scaling, but then you won't be able to really see them.

Best regards,

Jeff

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Jeff Hiller
Wen, You say that the displacements are ridiculously large and don't change with the parameters. Are you saying that based on the way the displacements are rendered on screen, or based on the values on the colorbar? By default, deformations are displayed scaled in such a way that they are easily visible with the naked eye. Their actual magnitude can be read off the colorbar. You can also change the scaling factor manually to 1 if you do not want any scaling, but then you won't be able to really see them. Best regards, Jeff

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Posted: 2 weeks ago Jan 13, 2021, 3:07 PM EST

Wen,

You say that the displacements are ridiculously large and don't change with the parameters. Are you saying that based on the way the displacements are rendered on screen, or based on the values on the colorbar? By default, deformations are displayed scaled in such a way that they are easily visible with the naked eye. Their actual magnitude can be read off the colorbar. You can also change the scaling factor manually to 1 if you do not want any scaling, but then you won't be able to really see them.

Best regards,

Jeff

Hi Jeff, Thanks for replying, I took 1D plots on the cross-sections on two different directions (x and y), and reading from the plots the displacements were above 7500mm on the edges and never change however I change the parameters. The only change happens when I change the CTE to negative, that the displacements become negative.

Wen

>Wen, > >You say that the displacements are ridiculously large and don't change with the parameters. Are you saying that based on the way the displacements are rendered on screen, or based on the values on the colorbar? By default, deformations are displayed scaled in such a way that they are easily visible with the naked eye. Their actual magnitude can be read off the colorbar. You can also change the scaling factor manually to 1 if you do not want any scaling, but then you won't be able to really see them. > >Best regards, > >Jeff Hi Jeff, Thanks for replying, I took 1D plots on the cross-sections on two different directions (x and y), and reading from the plots the displacements were above 7500mm on the edges and never change however I change the parameters. The only change happens when I change the CTE to negative, that the displacements become negative. Wen

Jeff Hiller COMSOL Employee

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Posted: 2 weeks ago Jan 13, 2021, 3:25 PM EST
Updated: 2 weeks ago Jan 13, 2021, 4:11 PM EST

You are saying that you are reading the displacements "from the plots" but that does not answer my question of whether you are eyeballing the displacements magnitude from the general look of their graphic rendition or whether you are reading their values displayed next to the colorbar while plotting the norm of those displacements. If it is the latter, please post your .mph file and I'll take a look at it.

Best,

Jeff

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Jeff Hiller
You are saying that you are reading the displacements "from the plots" but that does not answer my question of whether you are eyeballing the displacements magnitude from the general look of their graphic rendition or whether you are reading their values displayed next to the colorbar while plotting the norm of those displacements. If it is the latter, please post your .mph file and I'll take a look at it. Best, Jeff

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