rigid element for 3D analysis NASTRAN
rigid element for 3D analysis NASTRAN
(OP)
I am working with 3D elements (CHEXA) using NASTRAN. I need to use rigid elements and I am using RBE2s but they are not rigid at all for 3D analysis. I have alread used those elements before (2D models) and they work great but when I try and connect brick elements the rigid elements RBE2 are not rigid anymore.
The displacement of the slave node is not equal to the displacement of the master (I thought of a rigid rotation but even the lenght of the rigid is different).
Does anyone know why this happens and how to solve this problem?
cheers
The displacement of the slave node is not equal to the displacement of the master (I thought of a rigid rotation but even the lenght of the rigid is different).
Does anyone know why this happens and how to solve this problem?
cheers





RE: rigid element for 3D analysis NASTRAN
Hope this helps.
RE: rigid element for 3D analysis NASTRAN
I thought about coating CHEXAs with CQUADs but the problem is...what property and thickness should I give the CQUADs in order not to affect the analysis?
RE: rigid element for 3D analysis NASTRAN
It should not make too much difference, use 1/100th stiffness of HEXA elements. We typically scale stiffness by this factor and use a 0.1mm thick (our structures are typically 0.5-10m long and 2-3mm thickness) You could try different values and see how it affects the results.
RE: rigid element for 3D analysis NASTRAN
This infomation was really useful.
Cheers
RE: rigid element for 3D analysis NASTRAN
a rigid element stay rigid in linear analysis, dosn't matter if its 2D or 3D.
you wrote:
"The displacement of the slave node is not equal to the displacement of the master".
The displacements are not necessarily equal.
check your model by replacing the rigid element with a pyramid made of bars, ans see what happens
cheers