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# master slave connection model?

Experimenter

hi, i would like to create a master slave connection. i have a right circular tube, and at 100mm above one of the free end, i wish to apply a load, so this point at 100mm should be the master and the perimeter/boundary of the circle should have the slave joints.. please assist.

6 REPLIES

# Re: master slave connection model?

Siemens Genius

It sounds to me like you might want to consider an RBE2 or RBE3 element, depending on how you want your model to behave.

My apologies, but I also don't fully understand your question either so I really can't provide much further guidance. If you could post a picture, someone may be able to provide more guidance.

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# Re: master slave connection model?

Solution Partner Phenom

Dear RKR,

To apply remoted loads a way we have in FEMAP & NX NASTRAN is using rigid elements:

• The RBE2 (Rigid Body Element, type 2) element defines a rigid body whose independent degrees of freedom are specified at a single point and whose dependent degrees of freedom are specified at an arbitrary number of points. The RBE2 element uses constraint equations to couple the motion of the dependent degrees of freedom to the motion of the independent degrees of freedom. Consequently, RBE2 elements do not contribute directly to the stiffness matrix of the structure and ill-conditioning is avoided.

The RBE2 provides a very convenient tool for rigidly connecting the same components of several grid points together

• The RBE3 element is a powerful tool for distributing applied loads and mass in a model. Unlike the RBE2 elements, the RBE3 doesn’t add additional stiffness to your structure. Forces and moments applied to reference points are distributed to a set of independent degrees of freedom based on the RBE3 geometry and local weight factors.

Best regards,

Blas.

Blas Molero Hidalgo, Ingeniero Industrial, Director
IBERISA • 48004 BILBAO (SPAIN)
WEB: http://www.iberisa.com
Blog Femap-NX Nastran: http://iberisa.wordpress.com/

# Re: master slave connection model?

Creator
Dont suppose you could elaborate on what are the dependent and independent dofs? what do they depend on?

# Re: master slave connection model?

Solution Partner Phenom

Hello!,

With the NX NASTRAN solver, the RBE2 and RBE3 elements behave differently:

• RBE2: The active degrees of freedom of the single core node (independent) enforce the active degrees of freedom of the leg nodes (dependent). Therefore, the active degrees of freedom of all nodes included in an RBE2 element are considered rigidly connected.

Please remember: The DOF at the center of the ‘spider’ is the independent DOF. The others are dependent DOF and should not be dependent on another rigid or constraint element.

• RBE3: Unlike the RBE2, the RBE3 element is flexible (not infinitely rigid), due to the allowable freedom of the leg nodes. Common uses for this element type include adding and distributing mass without adding stiffness, and distributing a load from multiple points to a single point.

The following picture shows a typical application where the element representing the bolt is connected to the mesh of the bolted medium using RBE2 spider elements.

And here you are the animation of the results:

Best regards,

Blas.

Blas Molero Hidalgo, Ingeniero Industrial, Director
IBERISA • 48004 BILBAO (SPAIN)
WEB: http://www.iberisa.com
Blog Femap-NX Nastran: http://iberisa.wordpress.com/

# Re: master slave connection model?

Creator

Thanks Blas,

That clears it up for me. I need to use an RBE2 element for my application.

Also the meshing on those models looks great. Wish mine looked like that!

Brett

# Re: master slave connection model?

Creator

Hi Blas,

I just checked out your website.

Looks very imformative.

I say looks because it is not in English and thus I can't read up on all the wonderful FEmap knowledge you've put on the site.

Is there an English version?

Brett