What's a CBUSH Element?

[Naffoussi]

Hi,

Can anyone explain to me what's a CBUSH element ? what is the mathematical model representing this element? and when we have to use this type of element? if someone have a link for more informations, that will be great.

Thanks

 

[rb1957]

it's a zero length spring, so you can model shear stiff/flexible joints (like rivets).

if it helps, it used to be called CELAS.

look them up in the NASTRAN user manuals.

 

[SWComposites]

Its the most misnamed element on the planet.

You don't have to use it if you don't need to. Its often used to model fasteners, sometimes correctly.

To echo the above post, read the manuals.

 

[BlasMolero]

Hello!,
Since I know well the CBUSH element this is the only spring element I use in FEMAP & NX NASTRAN, is great!.
The CBUSH element is a generalized spring-damper structural scalar element connecting two noncoincident grid points, or two coincident grid points, or one grid point with an associated PBUSH entry. This combination is valid for any structural solution sequence. To make frequency dependent the PBUSH need only have an associated PBUSHT Bulk Data entry. The PBUSHT entry for frequency dependency is only used in SOL 108 and SOL 111. You can also use the PBUSHT entry to define load-displacement dependency in SOL 106.

The use of CBUSH element is all advantages over CELASi elements. For example, if you use CELASi elements and the geometry isn’t aligned properly, internal constraints may be induced. The CBUSH element contains all the features of the CELASi elements plus it avoids the internal constraint problem. The CBUSH element as a replacement for scalar element for static analysis. The analysis joins any two grid points by user-specified spring rates, in a convenient manner without regard to the location or the displacement coordinate systems of the connected grid points. This method eliminates the need to avoid internal constraints when modeling, OK?.

In dynamic analysis, the CBUSH elements can be used as vibration control devices that have impedance values (stiffness and dampling) that are frequency dependent.

Best regards,
Blas.

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Blas Molero Hidalgo
Ingeniero Industrial
Director

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[Naffoussi]

Thank you for answering