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Difference Between Fixed Constraint and Rigid Connector .

Posted Mar 21, 2013, 7:40 a.m. EDT Modeling Tools & Definitions, Parameters, Variables, & Functions, Structural Mechanics Version 4.0, Version 4.0a, Version 4.1, Version 4.2a, Version 4.3, Version 4.3a 2 Replies

Victor Soares
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Whats the difference between fixed constraint and rigid connector ??

I'm trying to simulate a Frequency Response Analysis on a Aluminum Box that has a 'shaker' on it's lid and the lid is fixed to an arm. So I'm using a rigid connector, because if Fixed Constrained it won't work.

So I'd like to understand better those two concepts.
2 Replies Last Post Mar 21, 2013, 10:56 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 Mar 21, 2013, 9:15 a.m. EDT
Hi
There are many issues here: some I can easily explain, to get a full view you need to dig into the formulas (equations)

Fixed means that u-0, v-0 w-0 is respcted i.e NO motion w.r.t. absolute reference.
A RC (rigid connector) applied to a (or more) boundary(ies) will make the boundary rigid (no relative deformation possible) only global displacements with respect to a CoR (centre of Rotation) and you can impose restricted position/motion (with respect to a global fixed reference) of this centre of rotation. An RC also generates a series of lumped variables such as 3 angles global displacements (w.r.t. CoR) if applicale, you can apply forces or moments to an RC.

Read through in detail the different BC, these are many and can be tailored to astonishing (and unexpeced) uses often via equations ;)

--
Good luck
Ivar
Hi There are many issues here: some I can easily explain, to get a full view you need to dig into the formulas (equations) Fixed means that u-0, v-0 w-0 is respcted i.e NO motion w.r.t. absolute reference. A RC (rigid connector) applied to a (or more) boundary(ies) will make the boundary rigid (no relative deformation possible) only global displacements with respect to a CoR (centre of Rotation) and you can impose restricted position/motion (with respect to a global fixed reference) of this centre of rotation. An RC also generates a series of lumped variables such as 3 angles global displacements (w.r.t. CoR) if applicale, you can apply forces or moments to an RC. Read through in detail the different BC, these are many and can be tailored to astonishing (and unexpeced) uses often via equations ;) -- Good luck Ivar
Victor Soares
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Posted: 1 decade ago Mar 21, 2013, 10:56 a.m. EDT
Thank you very much .



I have one more question...

I'm running this model, and I keep getting this error when I do the Frequency Sweep . 0 to 2000 Hz , 1Hz increment.

Error '' Failed to find a solution for the initial parameter.
Maximum number of Newton iterations reached.
Returned solution is not converged. ''


What is that I'm doing wrong for it to crash this way.
Thank you very much . I have one more question... I'm running this model, and I keep getting this error when I do the Frequency Sweep . 0 to 2000 Hz , 1Hz increment. Error '' Failed to find a solution for the initial parameter. Maximum number of Newton iterations reached. Returned solution is not converged. '' What is that I'm doing wrong for it to crash this way.

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