topic Re: inventor pro 2018- FEA huge reactions on constraints in Inventor Forum

inventor pro 2018- FEA huge reactions on constraints

jlkono — Thu, 01 Feb 2018 16:07:17 GMT

I am getting huge off the chart reactions on my FEA constraints with all loads and gravity turned off.

The inventor FEA result model weight is comparable with the autocad solid mass model weight although, that shouldn't matter if gravity is turned off. Material density was also verified and that too shouldn't matter with gravity off.

Any thoughts? I have attached the model.

Re: inventor pro 2018- FEA huge reactions on constraints

TheCADWhisperer — Thu, 01 Feb 2018 16:12:43 GMT

@jlkono wrote:

Any thoughts?

An assembly must include parts.

Re: inventor pro 2018- FEA huge reactions on constraints

jlkono — Thu, 01 Feb 2018 16:24:36 GMT

Attachment re-posted with all part files.

Re: inventor pro 2018- FEA huge reactions on constraints

TheCADWhisperer — Thu, 01 Feb 2018 17:26:41 GMT

Is there a reason you did not do Thin Features (Manual Mid-Plane) on the brackets?

Also, I see issues indicated with four of your Bonded Contacts.

Re: inventor pro 2018- FEA huge reactions on constraints

jlkono — Thu, 01 Feb 2018 18:27:40 GMT

Thank you. The entire assembly translated automatically to thin bodies which had not captured the brackets of your mention. On attempting to manually select the brackets, a warning came up advising not to. The bracket L/t ratio is apparently acceptable as a sold body. The erroneous contacts were removed and corrected. With the above said, I wouldn't discount the sold body braackets as being an issue, just don't know what to do about it.

No change on the constraint reactions. Super high order of magnitude, no gravity/no loads.

Re: inventor pro 2018- FEA huge reactions on constraints

TheCADWhisperer — Thu, 01 Feb 2018 19:43:03 GMT

I had a similar problem that I found the cause and solution for - but I don't have access to the assembly at the moment.

If someone else doesn't come up with the solution before tomorrow - be sure to bump this thread back to the top so that I check my other assembly.

Re: inventor pro 2018- FEA huge reactions on constraints

TheCADWhisperer — Fri, 02 Feb 2018 19:54:29 GMT

OK, I found some times to take a deeper look at this.

While I am looking, I recommend that you install the latest Updates for 2018.

Re: inventor pro 2018- FEA huge reactions on constraints

TheCADWhisperer — Fri, 02 Feb 2018 21:33:46 GMT

The sum of the Reaction Forces at the 8 pads should total the weight of the assembly.

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http://autode.sk/2nCBAP2

Re: inventor pro 2018- FEA huge reactions on constraints

jlkono — Sun, 04 Feb 2018 18:54:54 GMT

Many thanks for your time and review of my model. Indeed it appears to have been the translation to thin shell where the support brackets remained as solid bodies and contact gaps were then subsequently introduced. FYI, with no loads I was originally getting constraint reaction forces in the 100 millions of pounds magnitude ("huge"). I was not aware of potential consequences in the thin shell translation.

FYI on the vertical and horizontal shell seams. Horizontal were breaks for introducing stepped hydrostatic loads, the vertical were to introduce a wind pressure load.

Thanks again! All your points in your video are well taken.