Rigid Connections

Question

I saw a demo for a ProMechanica analysis using rigid connections as a constraint. It looked very useful. Then I tried to get some more detail info on it's use using the online help. The write-up seemed very technical and hard to understand. Can anyone break it down to simplier terms and maybe give a few practical examples of it's usage.

Thanks!!

JonathanHodgson · Answer

Hi Greg,

I've also seen a demo of Rigid and Weighted Links - I'd seen them in a
features list, and as I'd hoped they do work similarly to Nastran RBE2
and RBE3 elements, respectively. If you have Nastran-using FEA
colleagues, ask them about these.

I've yet to use them in anger in Pro/M, but basically RLs should work as
rivets or similar fasteners - they constrain two features (surfaces,
edges, points) - or however many they are attached to - to have equal
displacement, i.e. to move rigidly together.

WLs, I believe, force the displacement of the 'central' point to be
equal to the average displacement of the other geometry they're attached
to (or similar maths to this). The main use I have will be to constrain
a shaft as if it is supported in a bearing: by connecting the 'central'
point to a fixed point via a spring, I can allow the bearing journal to
tilt and rotate whilst still transmitting forces - or, I think, to
transmit a torque without being constrained in displacement. Neither of
these is possible with conventional constraints, even with a cylindrical
coordinate system.

You can also use RBE3 elements to act as 'virtual brackets' for loads
applied to a point outside your model geometry; but Pro/M already has
Total Load At Point for this.

Best regards,
Jonathan

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