Copy analysis created from frame generator model

[DavidWarta]

I have an analysis of a frame generator model. The model has no reuse members as they are not recognized by Inventor Nastran. I would like to analyze 8 different configurations of this model. When a copy the analysis in Inventor Nastran it creates copies of the idealizations. This makes opening and saving the model very slow. 

When I have the analysis model I would like to optimize the design so the stresses are acceptable as well as the reaction forces (so the model has optimal stiffness). This would require some modifications to the geometry and rerun of the analyses.

What would be a recommended workflow? Creating one analysis and copying creates a very slow responding model when opening saving and switching between analyses.

Currently I am trying to remove all created copies of beam and shell idealizations and refer in all analyses to the same idealizations.

[John_Holtz]

Hi,

I have not noticed anything appearing under the "Model" branch of the Model Tree to add to the size or speed of the model. That is, copies of the idealizations should not have an effect. What adds to the time and file size is the mesh and checking if the model has changed when activating an analysis. Most likely, that is true regardless of whether the analysis uses the same/original idealization or a copy. (Of course, you can delete the copied idealization and paste the original idealization into the duplicate analysis if that is what you really want to do.)

1. Most frame models use beam elements which should have a minimal impact on the file size and speed. You mentioned shell idealizations. If you are using the midsurface command to create shells from solids, that is where the slow speed comes from.  (It is better to create a surface model in Inventor than a solid and use Nastran to convert it to a surface.)
2. Where is the model saved? On the local computer hard drive or on a network drive? Network communications is very slow. Avoid doing an analysis when the model is on a network drive.

As for the question of duplicating the Inventor model (and have N Inventor models, 1 analysis each) or duplicating the analysis (and having 1 Inventor model, N analyses), either method will work.

• If you duplicate the Inventor model, you can have multiple models open which makes it a little easier to switch between models to compare the results.
• If you use one Inventor model, you should be able to use different Model States to have different "versions" of the model in the same file. In Nastran, the "Analysis > Edit > Model State" is where you indicate which Model State you want to use for the analysis.

John

[DavidWarta]

Thanks for the fast response!

My current model has approximate 200 beams (generated from frame generator, so each beam has its own idealization), 24 rectangular plates which are also converted by Nastran to midsurfaces. The number of nodes is around 5000. The software Nastran 2024 is responsive and fast. When I copy that analysis 8 times it grinds to a halt.

1. Is it possible to skip the check if the geometry has changed? This would be very helpful. Maybe add an update button.

2. Would it be better to use frame generator and the reuse beam function and assign the idealizations manually to the rest of the model?

[John_Holtz]

Hi @DavidWarta 

I just created a test model where I used either 1 idealization for 200 beams, or used 71 idealizations. (Sorry, I got tired of creating the idealizations one by one from my sketch.) It does appear that having more idealizations takes longer to load into Nastran.

I am trying another test now where I use the same idealizations in the duplicates analysis instead of using copies of the idealization. So instead of having 8*71 idealizations, there will only be 71 idealizations used 8 times. This should tell me whether copies are the problem or just the total number. (That is your question 2.)

I agree with your suggestion 1 about letting the user decide when to refresh the model. That option does not exist. 

John

[DavidWarta]

Easiest way to create a lot of idealizations is to use frame generator ;).  I will try and create just one idealization per type. 

How would you go about creating an analysis from a frame generator model? Would you let Nastran create one idealization per type and then assign those to the rest of the model or create the idealizations from scratch.