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How to generate different OP2 output file for each subcase?

How to generate different OP2 output file for each subcase?

How to generate different OP2 output file for each subcase?

(OP)
Hi,

I have 3 different load subcases for 1G loads in X, Y and Z directions. I would need to have Nastran write 3 different different OP2 output files, one for each subcase. Is it possible? What case control cards should I use?

For instance:
==
SUBCASE 1 ---> 1GX ---> output file: ...1GX.op2
SUBCASE 2 ---> 1GY ---> output file: ...1GY.op2
SUBCASE 3 ---> 1GZ ---> output file: ...1GZ.op2

BTW, I am using NX Nastran solver 2021.2.

Thanks,
Francesco.

RE: How to generate different OP2 output file for each subcase?

At the risk of frustrating you in case you don't have access to MSC Nastran as well, there is a case control command in MSC Nastran called POST. It may only be available for SOL 101, which appears to be your context. When used with the TOFILE keyword, the POST command may be used to put results from each SUBCASE onto a different post processing unit which you can declare with a name in the FMS section using an ASSIGN statement.

The other possibility is to do what we used to do before POST was available in MSC Nastran. You run the job with the 3 load cases as normal, but request NO data recovery; run the job with the scr=no command line keyword. When the job has finished, you should have the .MASTER and .DBALL database files from this job still in the directory where you ran the job. Now define a read only restart input file where you add the data recovery requests to a different SUBCASE in each restart job. The op2 files created by the restarts will contain only the results for the SUBCASEs where you requested output. If you use a read only restart, you can restart off the same primary database as many times as you want and it will not affect that primary database. If you do the restart correctly, the job does not resolve the problem - the database already contains the solution to your 3 applied loads; in the restarts, once everything has been checked to make sure you didn't change anything (except the data recovery requests), the job jumps straight to data recovery and computes what you asked for.

There is a section about restarts in the Linear Static Analysis User's Guide.

DG

RE: How to generate different OP2 output file for each subcase?

(OP)
Thank you DG!

I am using NX Nastran (sad), so POST case control command has not been implemented in that solver. I guess I will go with the second option as a workaround. When you mention "no data recovery in the initial run for building the .MASTER/.DBALL database", do you mean no output request (no displacements, no stresses, no forces, etc.)?

Cheers,
Marcos.-

RE: How to generate different OP2 output file for each subcase?

Yes, no output requests in the initial run - this is just a suggestion as you said you wanted to obtain 3 separate op2 files of results, and it seemed to simplest way to approach things. You could ask for some output requests in the first job (called the cold start) if you wanted to; doing this would not impact what you can do in the restarts, I just suggested it for simplicity.

DG

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