Hello all,

I am working on setting up Calculix Inertial Relief model on a free body model using the 3,2,1 method and comparing the results to a NXNastran equivalent model using Automatic Inertial relief.

When I specify:

*BOUNDARY

node1, 1,3

node2, 2,3

node3, 3

where Node1 is the reference node of a RIGID element attached to the free body CG, Node2 is attached to the reference node of a RIGID element attached to the maximum X part of the structure, and Node3 is node displaced in Y from the CG.

This set of constraints results in a stress distribution that is with about 2% of the NXNastran model, which is great.

HOWEVER

If I change the input model to use:

node1, 1

node1, 2

node1, 3

node2, 2

node2, 3

node3, 3

The 3,2,1 methodology breaks, and it looks like Calculix is not treating each constraint specification as additive when it is on the same node. If that is by design, that is OK, but this leads to a more basic hypothetical question:

How would I specify a constraint on a node of 1,2,3 and 6?

Thanks for any insights

Chris