I am trying to understand the mechanical behavior of vacuum chambers. For a cylindrical chamber under normal atmosphere with different grades of vacuum pressure inside the chamber. The internal pressure in both cases is so close to zero relative to atmosphere that the net compressive load on the walls is identical for buckling purposes. For ex. low vacuum (0.1 Pa): ΔP = 101325 Pa - 0.1 Pa ≈ 101325 Pa. For UHV (1e-9Pa): ΔP = 101325 Pa - 10^{-9} Pa ≈ 101325 Pa.
this does not makes any sense to me. UHV has have much much more suction force than a normal vacuum. But in simulation during the boundary condition, this difference is minimal. How to understand this paradox?
In case of vacuum, the chamber is actually being compressed by the outside atmosphere. Mechanically from the chamber’s point of view, both loads are practically identical (as you have calculated also). The structural load is almost entirely set by atmospheric pressure, not by the internal pressure. So as per my understanding mechanically both cases are same. For simulation or design point of view you may consider outside atmospheric pressure and inside no pressure (maximum possible load). So, UHV does not apply more compression from outside than a normal vacuum, there is no paradox.
Regards
Naveen
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