LGMASS Problem

[rlspicer]

I'm trying to run a model using NX NASTRAN 4.0 using the Large Mass Method and I keep getting garbage results. When I run the model using the enforced acceleration method I get results that make sense. I'm pretty sure that my set-up is okay because I tried using the same set-up on a different model and it works just fine. I've also run basic model checks and the model appears to check out. When I run using the enforced acceleration method I get the accelerations that match the curves I'm trying to generate. When I run the LGMASS method my accelerations do not fit to any curve that I expected and the values are 3-4 orders of magnitude too small. Any suggestions?

Here is my basic set-up:

DLOAD 1 1. 1. 102
FREQ1 1001 5. 0.1 950
RLOAD2 102 101 1001 LOAD
FORCE 101 100 0 1.0 0.0 1.0E11 0.0
SPC 1 100 456 0.
SUPORT 100 123
CONM2 100 100 0 1.0E11
GRID 100 0 0. -6.81 0. 0
CELAS2 101 1.E+9 1 1 100 1 0.
CELAS2 102 1.E+9 1 2 100 2 0.
CELAS2 103 1.E+9 1 3 100 3 0.
CELAS2 104 1.E+11 1 4 100 4 0.
CELAS2 105 1.E+11 1 5 100 5 0.
CELAS2 106 1.E+11 1 6 100 6 0.

 

[wvillers]

My first guess would be a units mismatch, i.e. the force you are applying is not correct... The large mass method should work just fine and should give similar results...