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non 0 initial velocity in solid mechanics takes no effect in stationary analysis?

Posted Mar 26, 2024, 11:55 p.m. EDT 4 Replies

Carl Xu
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In stationary analysis, if one sets a non 0 initial velocity in solid mechanics, is that simply ignored? That is, stationary analysis doesn't at all allow straight line uniform motion with no acceleration? Or stationary analysis doesn't allow any steady motion at all?

4 Replies Last Post Mar 31, 2024, 1:25 a.m. EDT
Henrik Sönnerlind COMSOL Employee

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Posted: 8 months ago Mar 27, 2024, 6:33 a.m. EDT

Yes, initial velocities do not affect stationary results.

In a stationary analysis, it is necessary that there are enough constraints to suppress any rigid body motions.

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Henrik Sönnerlind
COMSOL
Yes, initial velocities do not affect stationary results. In a stationary analysis, it is necessary that there are enough constraints to suppress any rigid body motions.
Carl Xu
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Posted: 8 months ago Mar 27, 2024, 7:12 a.m. EDT

Thank you. Why do we sometimes see that the solution is still obtained even when there's not enough boundary conditions to suppress rigid body motions?

Thank you. Why do we sometimes see that the solution is still obtained even when there's not enough boundary conditions to suppress rigid body motions?
Henrik Sönnerlind COMSOL Employee

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Posted: 8 months ago Mar 27, 2024, 8:39 a.m. EDT

That can sometimes happen if there are 'enough' numerical inaccuracies so that the stiffness matrix is not identified as singular. Also, sometimes an iterative equation solver can happen to find a solution.

When it happens, there is typically an arbitrary rigid body superimposed over the deformations.

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Henrik Sönnerlind
COMSOL
That can sometimes happen if there are 'enough' numerical inaccuracies so that the stiffness matrix is not identified as singular. Also, sometimes an iterative equation solver can happen to find a solution. When it happens, there is typically an arbitrary rigid body superimposed over the deformations.
Carl Xu
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Posted: 8 months ago Mar 31, 2024, 1:25 a.m. EDT

Thank you

Thank you

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