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simulation of deformation after removing fixed constraints

Posted Jul 19, 2013, 3:06 p.m. EDT Structural Mechanics Version 4.2a 3 Replies

Wei Zhu
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Dear all,

I want to simulation the final deformation of a plate after removal of its bottom fixed contraint

I have a solid plate with its bottom fixed to the ground. Its temperature changes from 70 degree to 30 degree, which will cause thermal shrinkage. however, not much deformation(shrinkage) will be generated since its bottom is fixed. Then, I want to remove the plate from the ground. large deformation is expected to be generated since the bottom constraint is removed and the plate will be free to move under the release of its internal stressed generated during the temperature drop process.

I don't know how to use its internal stress generated during the temperature drop process. How to get the final deformation? Can anybody give me some suggestions? Thanks in advance.


Wei
3 Replies Last Post Jul 22, 2013, 8:52 a.m. EDT
Josh Thomas Certified Consultant
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Posted: 1 decade ago Jul 19, 2013, 4:46 p.m. EDT
Wei,

Do you expect plastic (permanent) deformation during the cooling process with the bottom plate fixed?

If not, you can solve directly for the final configuration without the intermediate step of including the fixed bottom constraint. In a purely elastic analysis the results will be path independent.

You will also need to think of how to constrain the rigid body modes now that the plate is not fixed along the entire length of the bottom.

Best regards,
Josh Thomas
AltaSim Technologies
Wei, Do you expect plastic (permanent) deformation during the cooling process with the bottom plate fixed? If not, you can solve directly for the final configuration without the intermediate step of including the fixed bottom constraint. In a purely elastic analysis the results will be path independent. You will also need to think of how to constrain the rigid body modes now that the plate is not fixed along the entire length of the bottom. Best regards, Josh Thomas AltaSim Technologies
Wei Zhu
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Posted: 1 decade ago Jul 19, 2013, 6:35 p.m. EDT
Thanks for your reply, Josh.

I do not quite understand. Do you mean that for the purely elastic model, in my plate case,
path 1: bottom fixed, temperature T drops from 70 to 30 degree, then remove the bottom fixed contraints
path 2: temperature T drops from 70 to 30 degree with the bottom free

they have the same deformation?


originally, I tried to use path 1, in two steps, in the first step the temperature drops with bottom fixed . and in the second step,using the stress released to get its final deformation.

The problem is that I don't know how to use the released stress in COMSOL.
Thanks for your reply, Josh. I do not quite understand. Do you mean that for the purely elastic model, in my plate case, path 1: bottom fixed, temperature T drops from 70 to 30 degree, then remove the bottom fixed contraints path 2: temperature T drops from 70 to 30 degree with the bottom free they have the same deformation? originally, I tried to use path 1, in two steps, in the first step the temperature drops with bottom fixed . and in the second step,using the stress released to get its final deformation. The problem is that I don't know how to use the released stress in COMSOL.
Josh Thomas Certified Consultant
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Posted: 1 decade ago Jul 22, 2013, 8:52 a.m. EDT
Yes, they should have the same deformation. If you are interested in this elastic analysis, I would just start without the bottom fixed constraint. Then you don't have to worry about the released stress.

-Josh
Yes, they should have the same deformation. If you are interested in this elastic analysis, I would just start without the bottom fixed constraint. Then you don't have to worry about the released stress. -Josh

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