topic Betreff: Inventor: Stress symmetries in FEA on a sphere in Inventor Forum

Inventor: Stress symmetries in FEA on a sphere

Anonymous — Mon, 26 Nov 2018 09:45:23 GMT

I ran a static structural analysis of a simple sphere under external pressure (think of a submarine under water). I sliced that sphere to only leave one eight of it and applied a frictionless constraint on each side of the resulting shell.

The analysis runs well but I end up having a stress that is almost exactly double what I was expecting.

I guess one of my symmetries is somewhat counted twice but I cannot pinpoint which one. Is there a way for Inventor to understand I used symmetries and take that into account?

Below is a screenshot of the results. The shell is 1 mm thick and the radius is 10 mm. Pressure is 1 MPa. I expect the stress to be

S = P*R/(2*t) = 1*10/2 = 5 MPa

But I end up with 10 MPa...

@Anonymous,

marius.gildehaus has edited your subject line and embedded pictures for clarity
Original: Stress symmetries in FEA on a sphere

Betreff: Inventor: Stress symmetries in FEA on a sphere

S_May — Mon, 26 Nov 2018 09:45:52 GMT

Hi @Anonymous,

please upload the model...

Betreff: Inventor: Stress symmetries in FEA on a sphere

Anonymous — Mon, 26 Nov 2018 09:46:01 GMT

There you go!

Betreff: Inventor: Stress symmetries in FEA on a sphere

johnsonshiue — Mon, 26 Nov 2018 09:46:06 GMT

Hi Alex,

The radius in your model is 20mm, not 10mm. The FEA analysis shows roughly 10MPa correctly.

Many thanks!

Betreff: Inventor: Stress symmetries in FEA on a sphere

marius.gildehaus — Mon, 26 Nov 2018 09:47:25 GMT

Hello @Anonymous!

Could the hint from @johnsonshiue solve your problem?

Please hit the Accept as Solution button if a post or posts solves your issue or answers your question.

Thanks!

Betreff: Inventor: Stress symmetries in FEA on a sphere

Anonymous — Mon, 26 Nov 2018 10:09:28 GMT

Indeed! I got confused between the display of a radius and a diameter.