DMAP for Modal Analysis (*.op2)

 

This is the guide for the Modal analysis (Normal mode analysis) in MSC(or NX)/Nastran. It is necessary for you to the appreciate DMAP command in order to run your input file for Nastran. This example file is located in “<Install Dir>\Toolkits\Flexible input files\NASTRAN\NASTRAN_normal_OP2.dat”.

 

1.  Delete

•     Delete commands related to the super elements

 

SEALL = ALL

SUPER = ALL

 

2.  Add or Modify

•     Global Mass and Stiffness Matrix

 

COMPILE PHASE1B nolist noref

Alter ‘call sekmr’$

OUTPUT2 MGG,KGG//0/12////$

 

 

•     Stress and Strain Shape

•    The below commands are to create the stress and strain shape data to the OP2 file.

•    Note: If the stress and strain shape is added when you create the RFI file, you should use the Stress/Strian Shape option in Interface Option. (Refer to Interface Options)

 

…

Compile sedrcvr$ nolist

Alter 'call gpstress'(2,0) $

OUTPUT2 ogstr1//0/12///$

CEND

…

GPSTRESS(PUNCH)=ALL

GPSTRAIN(PUNCH)=ALL

…

VECTOR(SORT1,REAL)=ALL

SPCFORCES(SORT1,REAL)=ALL

STRESS=ALL

STRAIN=ALL

$

OUTPUT(POST)

$ Set 6 : write all element ids for

$       output gpstress and gpstrain (element IDs 1 ~ 50)

SET 6=1 THRU 50

$

$$ Solid element : Use VOLUME instead of SURFACE

$VOLUME 1 SET 6,DIRECT,SYSTEM CORD 0

$

$ Shell type element : Use SURFACE instead of VOLUME

SURFACE 1 SET 6,FIBRE ALL,SYSTEM CORD 0

 

…

 

•    The first red box is to write the strain shape data in the OP2 file.

•    The second red box is to write the stress and strain shape in the Punch file and OP2 file

•    The third red box is the necessary command for GPSTRESS and GPSTRAIN.

 

Note

When using the OP2 file after this analysis, the DMAP command of “PARAM,POST,-2” should be added. In addition, if there is “PARAM,OGEOM,NO” in DMAP commands, it must be deleted.