Hi FakeCaptainGabriel,
I'm not too suse how you setup your analysis/deck. I'm only using nastran.exe and editor, not the autodesk modeler... I'm using large mass method for random analysis. So basically, you want to shake a large mass, let say about 1e+7 time larger than your object to be tested. Then, reviewing your results, note that normally you want to look at 3sigma stresses, so basically 3 times the RMS output. Here a basic deck that should help you in setting up a random analysis. I guess you can figure the relation ant format of each card using the reference manual :
$SOL 111
SOL SEMFREQ
CEND
TITLE = Random
SUBTITLE = RANDOM_X
ECHO = NONE
SET 6 = 1 THRU 3
DISPLACEMENT(SORT2,PLOT,PHASE,PSDF) = 6
ACCELERATION(SORT2,PLOT,PHASE,PSDF) = 6
STRESS(SORT2,PLOT,PHASE,CORNER,PSDF) = ALL
ELFORCE(SORT2,PLOT,PHASE,PSDF) = ALL
SPC = 2
FREQUENCY = 1
METHOD = 1
SDAMPING = 4
RANDOM = 400
DLOAD = 40
BEGIN BULK
$
$**********************PARAM****************************************************
PARAM,OGEOM,NO
PARAM,AUTOSPC,NO
PARAM,GRDPNT,0
PARAM,FREQRESPRSLTOUT,OFF
$
$**********************RANDOM ANALYSES DEFINITION*******************************
EIGRL 1 350. MASS
$ Solution Frequencies
FREQ1 1 2. 2.0 50
FREQ4 1 2. 50. .05 3
$ Nastran Load Set 1 : Enforced Accel X
DLOAD 40 1. 1. 301
RLOAD2 301 302 55 LOAD
FORCE 302 1 1+7 9810. 0. 0.
RANDPS 400 1 1 1. 0. 52
$ Function 2 : Accel PSD Input X, To define
TABRND1 52 LOG LOG +
+ ENDT
$ Function 4 : Damping Function, To define
TABDMP1 4 Q +
+ 1. 25. 2000. 25.ENDT
$ Function 5 : Accel Function
TABLED2 55 0. +
+ 1. 1. 1000. 1.ENDT
$ Constraint Set 2 : BC
SPC1 2 23456 1
SUPORT 1 1
$
$****************************BULK DATA******************************************
$
$-----------------------------------------------------
INCLUDE 'xxx.nas'
$-----------------------------------------------------
CONM2 80000000 1 1+7 0. 0. 0. +
+ 0. 0. 0. 0. 0. 0.
ENDDATA
