RBE3 Interpolation Factor?

[EddyC]

Hi Folks,

I'm a recent Femap/Nastran user and have run into the RBE3 vs. RBE2 issue. I understand that the RBE2 is infinitely rigid. The RBE3 appears to have an elasticity that is defined via the Interpolation Factor. I am wondering how this Interpolation Factor relates to the real world? What do 1, 2, 3, etc factors mean in regular terms? Are they a percentage of full stiffness? I have something that I am modeling that I can calculate a stiffness of in lbs/inch, but don't know how my stiffness relates to the Interpolation Factor? I would appreciate some insight from more experienced users.

 

[40818]

Spring elements are what you want to use (or bush elements), and not RBE3 if you have calculated stiffness. RBE3 elements dont work in the way your wanting them to.

 

[jakeline6]

You are correct that an RBE2 is rigid. An RBE3 is an interpolation element. It does not add stiffness but instead is used for 3 basic features:

1. distributing loads from a single point to several points.

2. distributing mass from a single point to several points

3. connecting dissimilar element types like solids to shells.

I would not recommend changing the weighting factors. This would normally be done to alter the load distribution on the averaging grid points. It is normally not required to change these. typically you would have either 123456 or 123 at the reference grid and 123 at the averaging grids for a 3d model.