Inventor Nastran (2020) is unstable

[Max.H.Pour]

G'day All,

It looks like Nastran 2020 is unstable. I tried to open an analysis I've done with NIC 2019,18 and it crashed a few times. Then tried to open more analysis and it kept crashing every time I opened more complex models. It opens less complex models, no problem.

I was wondering if anyone else is having this problem?

Regards,

Max

[Roelof.Feijen]

Hello @Max.H.Pour ,

Purely out of curiosity, what is your definition of complex models. Analysis type, number of nodes, contacts? What error messages do you get? Are these reproducible on another workstation?

[Max.H.Pour]

@Roelof.Feijen 

If you have 2020 version installed, Please try to open older solved models  (your definition of more/less complexity) and see whether you experience the same issue or not. 

This is what I get:

[Roelof.Feijen]

No problem. I will do that and let you know what my experience is with the 2020 release. 

Still wondering, does it crash during solving or post processing?

From the image it is hard to tell wether Inventor crashes or the Nastran add in. The title suggests it is an Inventor crash, but it could also be the Nastran add in. Did you send the error report to Autodesk?

[Max.H.Pour]

@Roelof.Feijen 

It crashed during loading the FEA model. picture below is what I see right before it crashes. As you can see, it's loading the FEA model. I dug a bit more. It looks like models more than 1+E6 elements will crash at this stage(loading%). 1E6 element is just a rough estimate based on my investigations. 🙂 

I've sent the error msg to Autodesk twice. 

[shigeaki.k]

Hello @Max.H.Pour ,

after opening the assembly file,  could you hit the save button. If you get a dialogue with "Yes to All" or "No to All" options, please select "Yes to All". Then close Inventor. What we are trying to do is to convert all the parts to Inventor 2020 format. (If you need to keep the older format, I recommend keeping a copy of it somewhere).

Alternatively, could you open all the parts and assemblies individually and save them to update them to the latest format. Then close Inventor.

If you are still encountering issue, are you able to share the model with us. If required, could you send me or @John_Holtz  the link to download the file.

Regards,

Shigeaki K.

[Max.H.Pour]

Hi @shigeaki.k 

I've sent one of the models to @John_Holtz .

I just tried "Yes to All" save to couple of models and it did't work. 

[John_Holtz]

Hi @Max.H.Pour 

Thanks for the model. I was able to reproduce the crash. I will give the model to the developers so that they can figure out what is causing the problem.

I found two different ways to get into Inventor Nastran:

1. If you suppress the weldment (assembly) in the Inventor modeling space so that there is "no model", and then go into the Inventor Nastran (formerly In-CAD) environment, it will load without crashing. You can exit the Nastran environment, unsuppress the assemblies, and go back in successfully. 
2. I copied the folder B-B DrawBar (which has the G007205 KAG assembly and supporting files) to a new folder. In Inventor, I set the project to the default, and then opened the G007205 KAG assembly. While opening, I skipped the assemblies that were missing. The model opened, and I was able to get into the Nastran environment. (This showed that the mesh was at a different location than the solids.)

In both cases, some of the loads, constraints, connectors, etc. could no longer be associated with the model. This usually happens when the model is changed so that the face designation changes. But at least the input exists (as far as I can tell), so you can edit the loads, etc. and assign them to the proper geometry.

 Let me know if one of those options works for you.

[John_Holtz]

Just some more thoughts. Either of these may be related to the crash, but I am not sure if these are problems on my system, or if the crash may be related to modifications that need to be made to the assembly. (For example, I do not have Vault, so cannot "check out" the files).

• When I open the assembly file, Inventor reports that updates need to be applied. But when I try to update the assembly, there are some errors. Are these "missing faces" also causing a problem with Nastran? (See the image below.)
• Some of the files are marked as "read only", possibly because they were not checked-out from Vault before creating the pack-and-go file. (Just speculation on my part.) I changed the read only property, but that did not prevent the crash.

[John_Holtz]

Hi @Max.H.Pour 

I wanted to follow up with you. Have you been able to get the model into Nastran using any of my suggestions?

Based on feedback from development, the problem is related to the unresolved or outdated components in the assembly. So perhaps another solution is to update the assembly.

[Max.H.Pour]

Hi @John_Holtz 

Thank you for your reply. Please see below:

1. If you suppress the weldment (assembly) in the Inventor modeling space so that there is "no model", and then go into the Inventor Nastran (formerly In-CAD) environment, it will load without crashing. You can exit the Nastran environment, unsuppress the assemblies, and go back in successfully. It works for the 1st model. However, I have some other models that I used cut extrusions on the top level assembly to apply Symmetrical Constraint later in Nastran space. In these models, suppressing the assemblies to "no model" and enter into Nastran works fine, but when back to Inventor to unsuppress the assemblies, the cut extrusions get inactive and this will ruin the whole model and of course fails to enter back to Inventor Nastran space. 
2. I copied the folder B-B DrawBar (which has the G007205 KAG assembly and supporting files) to a new folder. In Inventor, I set the project to the default, and then opened the G007205 KAG assembly. While opening, I skipped the assemblies that were missing. The model opened, and I was able to get into the Nastran environment. (This showed that the mesh was at a different location than the solids.) Again, it works for the 1st model, but not for the other models with cut extrusion and other modifications.
3. Updating the model: Since in most cases, I clean the model (remove threads or irrelevant Chamfers/fillets or even cut extrudes for symmetrical constraints) updating the model will remove all the model preparations and modifications.

This issue has only showed up since I installed the new release. I have been running the same models occasionally for small design changes or producing reports for different clients without any issue.   

[Max.H.Pour]

Hi @John_Holtz 

Update on this:

After struggling for a few weeks and experiencing the same issues with more models, I finally decided to remove 2020 design package (Inventor, Nastran and Vault) and reinstalled 2019 version of design package. PROBLEM SOLVED! 

Prior to posting this update, I went and tried all the models I've had crash issue with only to make sure this was the case. All those models - that used to crash during entering into Nastran space - open in NIC2019 space without any issues and now I have access to all of my old FEA models.