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Problem with DBF file and NASTRAN - Key after the ENDDATA

Hi all,


I'm trying to automatically change a DBF file by replacing the force orientation in it and after run it in NASTRAN. The problem is that I need to not only change the force orientation but also to provide a certain "key" after the ENDDATA at the end of the DBF file.


As an example here is the last three lines of an "x" force:


$* NX Load and Constraint: Force(1)
FORCE 2 965 0 1000.001.000000 0.0000 0.0000
ENDDATA 5b9efbb2


If I want to run a case with a "y" force I have to make the following changes to make NASTRAN run it:


$* NX Load and Constraint: Force(1)
FORCE 2 965 0 1000.00 0.00001.000000 0.0000
ENDDATA 6bcd24f5


So, you can see that I have to get a certain "key" after the ENDDATA that will differ between the "x" and "y" force orientation and the only way to get this "key" is to open NX and generate a new DBF file which is really annoying since I want to automatically change the force orientation and run it in NASTRAN.


Can anyone help me with this?






Re: Problem with DBF file and NASTRAN - Key after the ENDDATA


Typically the NX Nastran solutions are launched within the GUI of FEMAP or NX Advanced Simulation products, this is the case when you run NX Nastran Desktop license.

In fact, in some cases you may want to launch the solution from the operating system command line. This may be helpful when the model is very large, and the solution needs most of the memory available on the computer platform. It is helpful in that situation to write out the NX Nastran input file from FEMAP or NX AdvSim preprocessors, shutdown the preprocessor, and launch the NX Nastran solver from the DOS command prompt using the following command line (in the past I used this trick usually!!):

nxn_executable_directory/nastran.exe input_filename PROG=xxxxx mem=yyyyy sdir=zzzzz

For the PROG keyword, valid options are PROG=DESK for floating NX Nastran Desktop license, or PROG=BUNDLE for the bundled NX Nastran Desktop license, or PROG=FEMAP if you are using FEMAP as preprocessor. Note that with the NX Nastran Desktop license, the solution must be performed on the same machine as the NX AdvSim/FEMAP pre/post that wrote the input file, and the input file cannot be modified.

This is the problem you have, the preprocessor adds the ENDDATA at the end of the nastran input deck.


Then is better to do the modification in the preprocessor itself, and let the preprocessor to write the nastran input deck correctly. Alternatively, use command PREVIEW ANALYSIS where you can edit the nastran deck and click solve.


You are also able to solve the model with NX Nastran Enterprise licenses. In this case, the PROG keyword is not required, and the NX Nastran solution can run on any machine, the ENDDATA keyword is not longer needed.


Best regards,


Blas Molero Hidalgo, Ingeniero Industrial, Director
Blog Femap-NX Nastran:
Accepted by topic author GRA_ASDL
‎08-26-2015 04:32 AM

Re: Problem with DBF file and NASTRAN - Key after the ENDDATA

The "key" you are referring to is the bulk data checksum. The NX Nastran solver recomputes the checksum and validates that it matches the checksum written by NX if you are running with a desktop or bundle license. One of the terms of the desktop/bundle license agreement is that the bulk data cannot be modified outside of a Siemens PLM pre/post application. The other significant term is that the NX Nastran solution must be executed on the same workstation as the bulk data file was written on.


If you want to edit a bulk data deck without a Siemens PLM Pre/Post application; or if you want to solve on a different machine than the one the deck was written on, you will need a NX Nastran  Enterprise license.




Re: Problem with DBF file and NASTRAN - Key after the ENDDATA

Thanks for your quick answers!