Firstly - this vessel is quite unreal because it has no ends(!). It
wouldn't hold pressure.
It's physically unrealistic because, while it has the hoop-stress,
there is no axial stress from the pressure - which is exactly half the
hoop-stress in a cylindrical pressure-container like a pipe or boiler.
That said - it's a useful reference case...
So, quick reality-check really - is all well with the model of the cylindrical part of a pressure vessel?
The overall stress is totally uniform and very close to 1000; the expected mathematical value.
The "exaggerated elastic deformation" plus the undeformed-mesh show something expected from solid-mechanics theory. Without axial stress, under hoop-stress, the cylinder has expanded radially but contracted longitudinally.
(R. Smith, 20May2016)