Units in results of explicit dynamic analysis

[VidyakinA]

Hi

What units are used in explicit dynamic analysis results? And where i can tune them?

Please see image attached for details.

[KubliJ]

Hi @VidyakinA,

Sorry about that, there is a known issue with the explicit solver not writing out the unit system.

But the unit system should be based off of what the model/analysis units are.

If you right click on Units in the tree and select edit, you can find the length and force units.

In my screenshot, we can see the length is mm and the force is Newton, so my stress would be in units of N/mm^2 or MPa.

Thanks,

James

[John_Holtz]

Just to clarify one point which is hopefully obvious but perhaps easy to overlook. The units in the results file is based on the unit system when the model was analyzed. If you change the unit system after the analysis and do not remember what the original units were when the analysis was performed, then you are out of luck.

In other words, James solution only works when you know what the original unit system was.

[VidyakinA]

Dear @KubliJ  and @John_Holtz ,

Thanks for fast reply!

I know how to choose or set units for analysis. Let's look to static stress analysis - There is no difference what Unit system your use, because you can choose (any from list) result units for contour plot while working with results. Isn't it? I checked it in 2021 release also. Please see image attached for details. But when explicit dynamic analysis is finished then i don't see any unit and can't choose.

After your comments i still don't understand: Is it bug with units in explicit dynamic analysis or impossible to indicate result units in this type of analysis or smth else.

John, you say "In other words, James solution only works when you know what the original unit system was.". OK. But why in results window i have possibility to choose units for contour plot (in static stress analysis for example)?

John, you say "If you change the unit system after the analysis and do not remember what the original units were when the analysis was performed, then you are out of luck." Ok, But if i am working with results or stress report of my collegue for example and i need immidiate information about units he used? In any case units must be indicated in any plots. I hope this fact don't need discussion.

I am going to make presentation "Whats new in Inventor Nastran 2021" for our customers and simulation community. And when i will show explicit dynamic analysis in action then first question for sure will be about units. Stress engineers very attentive persons))

Best regards,

Alexey Vidyakin

[benoit.neu-faber]

Hi @VidyakinA 

If I'm right, there is a "bug" that is not displaying the unit results in explicit Analysis. You are right it should be displyed as in static ananlysis, but it's not the case.

So to know the units in results you have to check and know the unit of the model before you run the analysis.

What @John_Holtz is saying is if you change the unis AFTER you have run the analysis, you will have issues.

It's a good practice to always work with the same units. In case you write a report, it's better to clarify manually the units.

@John_Holtz @KubliJ , correct me if something is wrong.

Benoit Neu-Faber

Autodesk Service Provider

https://www.linkedin.com/in/benoit-neu-faber/

Please accept solution and give likes if applicable

[VidyakinA]

Hi, @benoit.neu-faber 

I think  we need to clarify what means "change the unis AFTER you have run the analysis". If i have results with any unit i can easily get needed unit without CAE Software (you too, for sure). But why Software can't perform the same units transformation for our convenience in contour plot? It is simple task for developers to realise such transformation. We have list available units in contour plot results, so choose what you need. We don't change initial units after running the analysis.

Now there is a "bug" with displaying units in explicit dynamic analysis - that is all i wanted to understand.

Best regards,

Alexey Vidyakin

[John_Holtz · Accepted solution]

Hi @VidyakinA 

The explicit dynamics analysis is a different solver (a different program) from all of the other analysis types. Because it is a different program, some things are programmed differently or not programmed at all.

Inventor "knows" the units that were set during the analysis because the "old" Nastran solvers write the units information into the results file (the FNO file). The "new" explicit dynamics solver is not programmed yet to write out the unit system that was used during the analysis. Since the unit system is not written to the results file (the FNO file), Inventor has no way to know what the units are for the results. Therefore the contour plot cannot have the dropdown option to let the user change the units for the results plots.

[VidyakinA]

Hi @John_Holtz 

Thank you for explanation! Now all clear.

Best regards,

Alexey Vidyakin