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Loading an .op2 file and retrieving Frequency values and Modal Partecipation Mass Fractions

Hi All,

I'm using Hypermesh 2021.2 version with MSC Nastran as a processor. Usually I get an .op2 file as a result file.

As showed in the topic title, the question addresses to finding a way to load an .op2 file and getting frequency values and Modal Partecipation Mass Fractions.

I'm currently able to get from an .op2 file the CBUSH forces (using readvector or readmultivectors), but I'm not able to get frequencies value list and Modal Partecipation Mass Fractions by using the same method.

Is there a different method or a command to use?

Thank you very much

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Compose

English

v2021.2

Accepted answers

Roberta Varela_20843

Giuseppe,

I see now where the problem is: this result is only written in the .f06 file, which is a text file but not exactly recognized as a result file in the sense that it cannot be seamlessly interpreted by readvectorbuilder.

We have an alternative here, which is finding the blocks of data of interest within the .f06 files, after all they are comprised by text and could be read in Compose anyway. The idea is to:

1. Identify a tag with which the data of interest starts (e.g.: it could be that every time that you see the tag MODAL PARTICIPATION MASS FACTORS in your .f06 file, you will identify the information that you care about

2. Identify a tag with which the data of interest ends (e.g.: right after a certain block of data is read, there could be a certain character or a certain string that clearly signalizes the end of it)

3. Read the .f06 file as a whole

4. Look for that specific tag of step #2 within the .f06 file and read it until the tag of step #3 is identified

All of this is possible because these files are autogenerated by the solvers and have a fixed format.

I shared an example that shows how to do it:

Regards,

Roberta

All comments

Roberta Varela_20843

Giuseppe,

How exactly are you extracting the CBUSH forces?

There are 2 articles that might help you understand how to use the CAE/Test readers that we have in Compose:

Regards,

Roberta

Giuseppe Pavano

Hi Roberta,

thank you very much for your reply :-).

I have used the 'readvectorbuilder' command to open the Readvector Panel and to understand which command is suitable for Cbush Force extraction ('readmultivector' or 'readvector' for a single element).

For CBUSH Forces extraction, I have used the command 'readmultivectors', creating a matrix for a specific subcase containing all the forces (x, Y, Z) for each cbush element.

Then I tried to load on Readvector Panel an .op2 file containing results coming from a SOL103 (Normal Modes). Recalling the 'readvectorbuilder' command I'm not able to find a suitable command for Mode number extraction (Frequencies) and Modal Partecipation Mass Fraction.

I'm going to read the links you suggested me, I will let you know.

Thank you

Roberta Varela_20843

If you can also attach screenshots of what you see in readvectorbuilder when you load the file, it would be helpful.

Cheers,

Roberta

Giuseppe Pavano

Hi Roberta,

please, attached you can find a screenshot of what I see loading a Normal mode .op2 file.

Thanks,

Giuseppe

Image_1.1.jpg

Image_2.1.jpg

Roberta Varela_20843

Giuseppe,

The frequencies would be stored in Time step field actually, not in Type. Although it sounds a bit strange that the list of frequencies is stored in the Time step field, this is how we can see the data in other post-processing software, such as HyperView and HyperGraph.

If you expand the time step dropdown list, you will see the difference frequencies, and you could now use gettimesteplist to assign them to a variable.

Regards,

Roberta

Giuseppe Pavano

i Roberta,

thank you very much:-) Now I can take the mode frequencies and store them in a variable.

Do you know how to get Modal Partecipation Mass Fractions??

Thanks,

Giuseppe

Roberta Varela_20843

Giuseppe,

I think it depends on what you are asking to be saved when you are doing the pre-processing - in OptiStruct, for example, there is a card called Global Output Request to ask for outputs that may not be written by default, or if you want them to be a in special/different file format etc.

Once you made sure that your output file will have the desired result, we would simply see it available in that file when you load it. This result will likely be in of these 3 fields in the readvectorbuilder utility, depending on what it is:

Type
Request
Component

Regards,

Roberta

Giuseppe Pavano

Hi Roberta,

thank you very much, you're a very kind and skilled expert.

The problem is that I'm using MSC Nastran as a solver. In Nastran the card/param for requesting Modal Mass Partecipation Factor is MEFFMASS(PRINT,PARTFAC,MEFFM,MEFFW,FRACSUM,SUMMARY) = YES.

Unfortunately, this card is not supported by Hypermesh and it is grouped under Case_Unsupported_Cards along with ECHO, CEND and other unsupported cards.

Infact, once Nastran has performed the analysis, I'm can get Modal Partecipation Mass Factors only by opening the .f06 file and reading the specific rows and columns.

I guess for the same reason, I can't get Modal Partecipation Mass Factors on Hyperview as well.

I will try to get these results in a different way with a different approach and I will let you know I will be able to.

Thanks,

Giuseppe

Roberta Varela_20843

Giuseppe,

We have an alternative here, which is finding the blocks of data of interest within the .f06 files, after all they are comprised by text and could be read in Compose anyway. The idea is to:

3. Read the .f06 file as a whole

4. Look for that specific tag of step #2 within the .f06 file and read it until the tag of step #3 is identified

All of this is possible because these files are autogenerated by the solvers and have a fixed format.

I shared an example that shows how to do it:

Regards,

Roberta

Giuseppe Pavano

Hi Roberta,

thank you very much for your advice, it is exactly what I was looking for :-).

I'm looking at the example you share with me in order to find the commands needed to identify start and end tags for Modal Mass Partecipation Fraction in .f06 file.

I will let you know as soon as I will get the results and if I'll be able to get them.

Thanks

Giuseppe

Roberta Varela_20843

Giuseppe,

Anytime! And please keep us posted how it goes or if you are not able to parse the .f06 file and need further help.

Regards,

Roberta