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volume expansion

Posted Apr 8, 2014, 10:47 p.m. EDT Structural Mechanics Version 4.3a 3 Replies

Huashun Wen
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Hi,

I'd like to simulate volume expansion of one materials by using Structural Mechanics, when the temperature change from room temperature (300K) to a high temperature (for example, 1350K). I want to get 2.2 times volume expansion. But no matter how big the CTE (coefficient of thermal expansion) is, I did not get 2.2 times volume expansion. There is only a small volume expansion. I want to ask how to simulate the large volume expansion. Thank you.
3 Replies Last Post Apr 10, 2014, 1:30 a.m. EDT
Nagi Elabbasi Facebook Reality Labs
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Posted: 1 decade ago Apr 8, 2014, 11:05 p.m. EDT
Hi Huashun,

It may be just a post-processing issue. COMSOL could be getting you large volume change but then when plotting the results it scales displacements. In most cases the displacements the displacements are much smaller than the structure and are scaled up so that you can see the deformed geometry. However, in cases where you have large displacements they will be scaled down. Turn off displacement scaling and also calculate the volume integral.

Nagi Elabbasi
Veryst Engineering
Hi Huashun, It may be just a post-processing issue. COMSOL could be getting you large volume change but then when plotting the results it scales displacements. In most cases the displacements the displacements are much smaller than the structure and are scaled up so that you can see the deformed geometry. However, in cases where you have large displacements they will be scaled down. Turn off displacement scaling and also calculate the volume integral. Nagi Elabbasi Veryst Engineering
Huashun Wen
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Posted: 1 decade ago Apr 9, 2014, 8:58 p.m. EDT


Hi Nagi,

Thanks for answering. Followed what you said, I have gotten large volume expansion by setting the scale factor=1. Another question is how to calculate the volume after expansion. The volume of the initial structure is calculated, but I do not know how to calculate the volume after expansion. Thank you so much.

Wen



Hi Huashun,

It may be just a post-processing issue. COMSOL could be getting you large volume change but then when plotting the results it scales displacements. In most cases the displacements the displacements are much smaller than the structure and are scaled up so that you can see the deformed geometry. However, in cases where you have large displacements they will be scaled down. Turn off displacement scaling and also calculate the volume integral.

Nagi Elabbasi
Veryst Engineering


Hi Nagi, Thanks for answering. Followed what you said, I have gotten large volume expansion by setting the scale factor=1. Another question is how to calculate the volume after expansion. The volume of the initial structure is calculated, but I do not know how to calculate the volume after expansion. Thank you so much. Wen [QUOTE] Hi Huashun, It may be just a post-processing issue. COMSOL could be getting you large volume change but then when plotting the results it scales displacements. In most cases the displacements the displacements are much smaller than the structure and are scaled up so that you can see the deformed geometry. However, in cases where you have large displacements they will be scaled down. Turn off displacement scaling and also calculate the volume integral. Nagi Elabbasi Veryst Engineering [/QUOTE]
Henrik Sönnerlind COMSOL Employee

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Posted: 1 decade ago Apr 10, 2014, 1:30 a.m. EDT
Hi,

In order to compute the deformed volume, you can integrate the number '1' over the volme. The integral must be performed on the Spatial frame. In order to have a spatial frame which reflects the deformed coordinates, the study must be geometrically nonlinear.

Note that with volume changes as large as in your problem, the interpretation of thermal expansion coefficients is nontrivial.

Regards,
Henrik

Hi, In order to compute the deformed volume, you can integrate the number '1' over the volme. The integral must be performed on the Spatial frame. In order to have a spatial frame which reflects the deformed coordinates, the study must be geometrically nonlinear. Note that with volume changes as large as in your problem, the interpretation of thermal expansion coefficients is nontrivial. Regards, Henrik

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