displacement calculation with RBE3

[LauMTL]

Hello all,

I perform dynamics analysis (sol 103, 145 & 146). I would like to obtain the displacements and the modes on one point which will be the mean of the displacements of an area of my structure.

So I defined a reference grid point and attached it to some points of my structures with a RBE3. The DOFs component requested are 123456 and the constraint DOFs are 123. I don't use any specific weighting. This point is not used to intruduced any loading. It is only used to observe the displacements.

However in some cases the obtained displacements are quite strange for me : values are not in the envelopp of the displacements of the other RBE3 grid points (problem observed on one translation and one rotation).

All information I found on RBE3 formulation is about the method used to distribute a load applied on the reference grid point. But I can't find any precise information on the method to calculate the dispacements of this reference grid point.

Does someone have some precisions on this displacement calculation method ?
Does the displacement calculation depends on the RBE3 geometry (for exemple distance between reference point and the other ones) ? Shall the reference point be placed between the other points in all directions ?
I read that rotations are calculated bys using translations. How this calculation is performed ?

Thank you for your help
Laurent

 

[BlasMolero]

Dear Lauren,
In fact, the use of RBE3 elements is correct in the way you explain, I take advanced of RBE3 elements a lot, but make sure to setup the RBE3 element as follows: in the DEPENDENT "NODE" side activate 1,2,3 DOFs, and in the INDEPENDENT "NODES" (nodes to average) activate "only" 1,2,3 DOFs and use factor =1, simply, OK?.

Best regards,
Blas.

~~~~~~~~~~~~~~~~~~~~~~
Blas Molero Hidalgo
Ingeniero Industrial
Director

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