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Hey everyone, I have modelled my roll cage in SolidWorks using weldments and now trying to run a linear static analysis in Autodesk inventor Nastran environment. I am trying to do the roll-over analysis. For this, I have applied the materials, created the mid-surface, applied the constraints and loads, applied the contacts, meshed the model and ran my setup. But I am getting error
I could not find the solution as how to rectify mine analysis. I have to use shell analysis only. Also, I have used two different types of cross-sections
I have attached the file.
Please help me out in performing the simulation using mid-surfacing technique. 🙏
Hi @Prashant_Jha ,
Seeing your questions brings back memories from when I participated in the SAE Baja competition. Sigh . . . oh to be young again.
This autodesk article has a bunch of information about that error and will provide more detail in case my guess below is not right - your Inventor file still did not have any inventor Nastran information in it?
First a piece of advice: Start small!
Rather than taking the whole project and trying to analyze the whole thing in one go, just do a small piece first, like in the picture below (even though you see the whole frame, only a small part is meshed, for you - I recommend going completely basic, save a copy and delete most of the frame just to be sure). It will be much quicker to set up, run, debug, and localize specific issues. Once you get that figured out, you slowly add complexity until you have what you need.
and the most likely answer is:
Based on your picture, I would guess that the shell elements are not connected from one property to the next. Zoom in and see if you can see disconnected elements. The image below has two examples of this:
First is the gap between the coped pipe and bent pipe - to fix that you must use a "Contact". Sadly, Inventor Nastran cannot automatically detect this type (edge to surface on shells), so you will have to manually create this connection for every joint - which will take alot of time.
Second, since the bent pipe is actually modelled as a straight and curved sections as two separate bodies - and meshed as two entities, they must also be connected - I purposefully meshed the two with different mesh sizes to demonstrate the Inventor Nastran does not automatically merge nodes. Inventor Nastran does not really have any tools to fix this, I recommend you combine those two bodies in CAD - then they will mesh continuously and it will be more realistic anyway.
To help find which parts are "floating", it is common to run an eigenvalue analysis and view the results of vibration modes at ~0 Hz.
Although Inventor Nastran technically can do midsurfacing, in my opinion it more of an underdeveloped side feature in this software. Normally, I whole heartedly encourage the use of shells, but Inventor Nastran just does not have a good toolset for shell elements. If using shells is a requirement for your project, I would suggest you inquire from your professors which software your university has that would be best.
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