topic Re: Inaccurate FEA Results in Fusion Design, Validate & Document Forum

Inaccurate FEA Results

ReachShaun — Sat, 02 Oct 2021 22:58:18 GMT

I'm not sure what's going on here. These FEA results don't seem to be accurate. Can someone take a look and tell me where I went wrong?

Re: Inaccurate FEA Results

jhackney1972 — Sun, 03 Oct 2021 00:55:20 GMT

The results look correct to me for your setup. I do not think your selection of the Constraints are correct. Two of the legs of this table should be free to slide on the floor so Fixed should be replaced with Frictionless. The maximum displacement for your configuration is 11.75mm, with Frictionless constraints it is 12.36mm. As you would expect, since the table leg, on one side, can slide on the floor, due to the flexing of the legs, you get a different maximum displacement. My model is attached.

Re: Inaccurate FEA Results

ReachShaun — Sun, 03 Oct 2021 15:44:27 GMT

Update: After changing the fixed constraints to frictionless constraints, I am now getting failed results during the solving process.

Re: Inaccurate FEA Results

ReachShaun — Sun, 03 Oct 2021 15:48:29 GMT

I see you made only the back legs frictionless, which passed the test. However, wouldn't both legs slide on the floor when a load is applied?

Re: Inaccurate FEA Results

jhackney1972 — Sun, 03 Oct 2021 15:48:35 GMT

Please note that I only changed "two" fixed constraints into frictionless constraints. You can take a look at my supplied model. You have to have two legs, on one side, with fixed constraints to keep the table in position. I would expect a failed solution if you change all the leg fixed constraints to frictionless.

Re: Inaccurate FEA Results

jhackney1972 — Sun, 03 Oct 2021 15:51:18 GMT

Sorry, your post came in as I was typing. Well in real life all legs will try and spread but in this simulation Fusion 360 cannot compute that condition. If two legs slide on the floor, you will get the same result. Think about it, if you put the table legs, on one side against the wall or some stop, the other two legs would just move as required.

Re: Inaccurate FEA Results

ReachShaun — Sun, 03 Oct 2021 16:08:57 GMT

Thank you for your help! I will mark your advice as the solution.

Re: Inaccurate FEA Results

TheCADWhisperer — Sun, 03 Oct 2021 17:08:01 GMT

@ReachShaun wrote:
...wouldn't both legs slide on the floor when a load is applied?

You are doing Static Analysis - not Motion Analysis.