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Command line option for load set selection

Pioneer
Pioneer

Is there Nastran command line option to specify load set to analyze without changing the load set case control in the input file? 

 

I have thousands of load sets to analyze and it would be nice to only have to change the Nastran command line and not have to create thousands of input files.

 

Thank you,

Sam

4 REPLIES

Re: Command line option for load set selection

Siemens Phenom Siemens Phenom
Siemens Phenom

What analysis type? The typical workflow would be to select each load set in it's own subcase, then run a single analysis. This is the most efficient method for linear static analysis as the stiffness matrix is assembled and decomposed only once, then multiplied by each set of loads to produce the individual subcase results (assuming that constraints are not changing as well).

Re: Command line option for load set selection

Pioneer
Pioneer

JimB,

 

Thank you for your response and for reminding me about the inefficiency of having to assemble and decompose the stiffness matrix over and over again.

 

I am running linear static. I understand that, in most cases, it is better to initiate the load set through the use of subcases in one run file. The problem for me is that I have 35,000+ load cases to run and the output file would be too large for my computer to manage. That is why I am creating separate run files for each load case so that I get a separate output file (.f06) for each load case. There will be 35,000+ .f06 files but they will each be small and easy to manage. Is there a way that I can have one run file with all my load sets as subcases and request a separate output file for each subcase? That way, I would not have to re-calculate the stiffness matrix for each subcase as you have pointed out.

 

Thank you,

Sam

Re: Command line option for load set selection

Phenom
Phenom

Hi, I can't help you at the moment, but I have a question: How on earth did you create 35000 and more load cases? Is there a script to do so? - Maybe you could modify your script to define 35000 solutions with one loadcase instead and afterwards you can solve all solutions in a rush. Here I assume you are using Simcenter or FEMAP.

Or did you create your DAT file outside of Simcenter or so? - Best wishes, Michael

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Re: Command line option for load set selection

Phenom
Phenom

If the model is large running it 35,000 times would not be very efficient.

To create so many load cases is not unheard of in the aircraft industry - This is done via databases - None of that Nx, Patran etc type of non-sense. Scripting/automated method is the best way and INCLUDE statment is then used. Each INCLUDE file can represent specific condition for example. You must also have a way of checking that all 35,000 cases have been properly set-up. Not an easy task possibly!

In some instances some enveloping is done to reduce the number of LCs but if 35,000 it is then you have to live with it. Mind you one should question the analysis "strategy". If you have so many cases you know that you'll need to pre & post process them in a very efficent manner. Need some early thinking about it !

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