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CBUSH Forces from Random Analysis

Pioneer
Pioneer

Hi

I have printed my RMS CBUSH forces in my f06 file for my random analysis, and I get the odd looking output whereby every second element (the odd numbered elements) has the identical RMS force. There is no structural reason for this since the CBUSH elements are scattered through the structure. Any thoughts??? Is this a bug? I am using NX Nastran 10.1

Thanks

Peter

 

      RANDOM EXCITATION IN X AXIS                                                                                                  
0                                                                                                            RANDOM  200           
 
                                 F O R C E S   I N   B U S H   E L E M E N T S        ( C B U S H )
                                    ( ROOT MEAN SQUARE; RMSSF SCALE FACTOR =  1.00E+00 )
 
                  ELEMENT-ID        FORCE-X       FORCE-Y       FORCE-Z      MOMENT-X      MOMENT-Y      MOMENT-Z 
0                      20000      4.575163E+01  4.519274E+01  2.387460E+01  2.618248E-02  4.294705E+00  1.326333E-02
0                      20001      1.058912E+01  8.931543E-02  1.720516E+00  1.525297E+01  0.0           0.0
0                      20002      5.488483E+01  4.866644E+01  2.835940E+01  3.698419E-02  4.296089E+00  1.326333E-02
0                      20003      1.058912E+01  8.931543E-02  1.720516E+00  1.525297E+01  0.0           0.0
0                      20004      1.113303E+02  7.227651E+01  3.771737E+01  1.127954E-02  4.302186E+00  1.326333E-02
0                      20005      1.058912E+01  8.931543E-02  1.720516E+00  1.525297E+01  0.0           0.0
0                      20006      6.616685E+01  4.382249E+01  6.088460E+01  2.881108E-01  4.276686E+00  1.326333E-02
0                      20007      1.058912E+01  8.931543E-02  1.720516E+00  1.525297E+01  0.0           0.0
0                      20008      6.341368E+01  6.731493E+00  4.263287E+01  1.543699E-01  4.233518E+00  1.326333E-02
0                      20009      1.058912E+01  8.931543E-02  1.720516E+00  1.525297E+01  0.0           0.0
0                      20010      7.089388E+01  4.721143E+00  9.756075E+01  1.909317E-01  4.234123E+00  1.326333E-02
0                      20011      1.058912E+01  8.931543E-02  1.720516E+00  1.525297E+01  0.0           0.0
0                      20012      1.100172E+02  4.152062E+01  6.580973E+01  2.156969E-01  4.263972E+00  1.326333E-02
0                      20013      1.058912E+01  8.931543E-02  1.720516E+00  1.525297E+01  0.0           0.0
0                      20014      4.859082E+01  2.863206E+01  6.135286E+01  2.890896E-01  4.348578E+00  1.326333E-02
0                      20015      1.058912E+01  8.931543E-02  1.720516E+00  1.525297E+01  0.0           0.0
0                      20016      5.562118E+01  6.090413E+00  3.952355E+01  1.525556E-01  4.402057E+00  1.326333E-02
0                      20017      1.058912E+01  8.931543E-02  1.720516E+00  1.525297E+01  0.0           0.0
0                      20018      6.453154E+01  3.816318E+00  9.318201E+01  1.847750E-01  4.414215E+00  1.326333E-02
0                      20019      1.058912E+01  8.931543E-02  1.720516E+00  1.525297E+01  0.0           0.0
0                      20020      1.157061E+02  3.713385E+01  7.070361E+01  2.606463E-01  4.390158E+00  1.326333E-02
0                      20021      1.058912E+01  8.931543E-02  1.720516E+00  1.525297E+01  0.0           0.0
0                      20022      1.047741E+02  6.775125E+01  3.204050E+01  2.052855E-02  4.334414E+00  1.326333E-02
0                      20023      1.058912E+01  8.931543E-02  1.720516E+00  1.525297E+01  0.0           0.0
0                      20024      1.350745E+02  2.666779E+01  1.771207E+01  4.465656E-02  4.351019E+00  1.326333E-02
0                      20025      1.058912E+01  8.931543E-02  1.720516E+00  1.525297E+01  0.0           0.0
0                      20026      1.344452E+02  2.519767E+01  2.008661E+01  2.965471E-02  4.348310E+00  1.326333E-02
0                      20027      1.058912E+01  8.931543E-02  1.720516E+00  1.525297E+01  0.0           0.0
0                      20028      4.273521E+01  2.838417E+01  8.616064E+01  2.411083E-01  4.306466E+00  1.326333E-02
0                      20029      1.058912E+01  8.931543E-02  1.720516E+00  1.525297E+01  0.0           0.0
0                      20030      6.163299E+01  5.139896E+00  7.716213E+01  1.923653E-01  4.266183E+00  1.326333E-02

 

2 REPLIES

Re: CBUSH Forces from Random Analysis

Siemens Phenom Siemens Phenom
Siemens Phenom

Can you share your model? or at least a portion to see how the cbush and surrounding eleemnts are defined? I have never seen an issue like that and it would be very helpful to see the actual model .

Re: CBUSH Forces from Random Analysis

Siemens Phenom Siemens Phenom
Siemens Phenom

This turns out to be an issue in Nastran when the CBUSH force output request is limited by using an output set instead of "ALL". The issue is also limited to the punch and f06 results, the op2 results are correct.

The CBUSH forces are correct in the pch,f06 and op2 when "all" force output request is used.