simulation - vacuum load

[mirovyane]

Hi all,
I'm running a FEA simulation of vacuum chamber (without much experience in that area).
It's a simple thin wall chamber (axisymmetric)

I assume to represent vacuum I can just apply 0.1MPa pressure (1bar differential pressure) to the walls inwards.
Could anyone confirm if using this load is the correct approach?
Thanks

 

[gravityandinertia]

It's the approach that I would use. However, I would apply the pressure inward from the outside faces. This is because the stress comes from an unbalanced external pressure vs internal pressure. When you have a vacuum, you are lowering the internal pressure, then the external force becomes larger than the internal. The net difference then has to be carried by the material for equilibrium to be maintained.

 

[TGS4]

The failure mode for this type of arrangement is buckling. An axisymmetric model will automatically exclude all non-symmetric buckling modes. Simply put, symmetry is a bad idea when investigating buckling.

 

[mirovyane]

Hi guys,
thank you for your comments.
I'll run the simulation with the full 3D geometry and pressure applied on the outer faces.

 

[btrueblood]

...and using the nonlinear solver to find eigenvalues and estimate the buckling loads...then knock down those buckling loads by a factor of 0.5 or less, since the fea model will always be stiffer and defect-free than the real thing...