Stress in weld and plate do not match over whole model.

[Anonymous]

Dear Forum,

I am new to the Inventor Pro software. Just ran my first FEA and have some questions. 

I am analyzing the stress in the curved plate and the weld. In some locations, the stress is not a continuous value when looking at the weld interface with the plate. In one area the weld is showing a red and the plate is showing green. In another area, the weld and the plate are showing red continuous.

I would also like to know how to get the weld and the plate mesh to be the same. I am thinking these two issues may be related. 

I am new to Inventor and just loaded Inventor Pro on the computer last week. 

I have added the model and a screenshot of the issue. 

Thank you for your help.  

Mike 

[imajar]

Hi @Anonymous ,

welcome to the forum!  I was unable to open the files you attached (missing parts, I suggest using pack and go in the future for this).

Modeling welds like that is generally discouraged for FEA.  This Autodesk webinar recording has some great information about welds in FEA and recommended methods:  https://www.youtube.com/watch?v=K6MPCb6V02M

The general stress pattern looks about right to what I would have expected with stress risers at the ends given the geometry and loads.  

If I had to guess as to why the stress is discontinuous between the weld and plate, I would look at the mesh in the area.  Unfortunately, Inventor does not have any tools for mesh matching between parts, so the best things you could do instead is refine the mesh, but since your model has discontinuities you will end up with singularities (hotspots) at the ends and possibly at the root of the weld.  (this goes back to why modeling welds is discouraged).  

I would recommend you watch the video and use traditional weld calculation methods.

[Anonymous]

Thanks Aaron,

I watched the video. Great to see Vince Adams is still doing this! I like him and always pick tips up from him. It looks like I need to try the weld calculator. Assuming this is part of Inventor Pro. 

How do I do this "pack and go" for next time? 

Thanks again.

Mike 

[imajar]

There are a few ways to do a pack and go.  If it is open in Inventor click File --> expand save as menu --> click pack and go.  A pack and go will collect all the files associated with your assembly and package copies in a new folder.

Rather than giving a long description, I would suggest you google "Inventor pack and go" and watch a video about it to learn what it does and what all the options do.  

The weld calculator is available in Inventor Pro, but only in a weldment assembly.

[Anonymous]

Hi Aaron,

I have a pack n go made. The file maximium of 3 is reached. How do I get the assembly and 2 parts loaded into the forum?

Mike 

[imajar]

you zip it.

[Anonymous]

Hello Aaron,

Attached should be a zipped file of all the parts in the assembly. 

Would you please take a look? 

I am wondering the best way to make changes to the parts and re-run the analysis?  

Do I back out of the FEA analysis and go back to the Assembly and make the part change?

Save the assembly as a new assembly revision? 

Any tips on making the work flow?

Please advise-

Thanks,

Mike

[imajar · Accepted solution]

The beauty of Analysis in Inventor is how easy it is to change the parts and update the analysis.  Having used dedicated FEA software in the past, I love this feature.  On the flip side, the in-cad FEA capabilities (even with Inventor Nastran) are very limited comparatively.

So:  yes, you would exit the analysis environment, make the changes in the assembly and parts, then reenter the analysis environment, fix any thing that broke, make sure all your contact, loads, constraints etc are still good and rerun.  

If you want to keep track of versions, then I recommend doing a pack and go each time.  (If you just do a save as on the assembly file and save the assembly as a new revision, that wont do any good, the part files the assembly is referencing will still be referenced by the old revision assembly and any changes you make to those will propagate to the new and old assemblies alike - hence why I would do pack and go).

PS: that is quite the assembly with some massive loads, massive plate thicknesses, etc!

PSS:  If you subscribe to the design collection, you can use Inventor Nastran, which is a much more powerful FEA tool compared to the stress analysis add in.  It has a bigger learning curve though.

[Anonymous]

Hi Aaron,

OK. Thanks for the tip. Pack and go to another folder. Then modify the parts and as you say, make sure the FEA items are not broken. I have noticed how well the FEA software knows what you are trying to do. Pretty good for me to be able to start right up. NASTRAN does look like a formidable learning wall.

The parts are BIG. Isn't that cool? I love the size. 

Thanks again. 

Talk to you later.

Mike