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1 atm vacuum flange FEA constraints?

1 atm vacuum flange FEA constraints?

1 atm vacuum flange FEA constraints?

(OP)
Hi all,

This is my first foray onto these forums, having found them via a google search.  I'm a mechanical engineer with access to Mechanica FEA in ProE.  I've not done any B&PV designs before.

I have a mostly rectangular (rectangular but for a square removed from one corner) vacuum chamber flange which is 450 mm x 200 mm, and sealed with an o-ring whose groove is in the mating part.  The chamber is evacuated and so the pressure delta is 1 atm in use.

My question is how does one model the deflection of such a flange to see if vacuum leaks will occur?  My first blush attempt was to simply fix a strip of material on the bottom of the flange, following the contours of the footprint, then apply a uniform 1 atm load across the top surface.

This gave reasonable results, but it doesn't really tell me if the seal will fail, since I explicitly told the FEA system that my region of interest is fixed.  How does one apply constraints to such a system?  After the o-ring is compressed, there is metal-to-metal contact, but I can imagine that under enough central deformation, the corners of the flange could flex up sufficiently to cause a leak.

Can anyone offer some advice, or point me in the direction of some helpful reference material?

Thanks,
Adam Hartman

RE: 1 atm vacuum flange FEA constraints?

Repost in a FEA forum-particular to your software

RE: 1 atm vacuum flange FEA constraints?

I don't know Mechanica and I've never done something similar, anyway, I'd suggest to try modelling the o-ring (proper modulus of elasticity) putting contact elements between the o-ring and both the cover and the groove metal surfaces; for a first analysis "glue" type should be sufficient.
First load step: gasket seating.
Second load step: vacuum.
A comparison between the initial and final contact pressure should give some information about potential leak.

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