27-11-2012, 05:30 PM
Pressure Test of a Pressure Vessel with Glass Dome and Cylinder of Other Material
Pressure Test of a Pressure Vessel with Glass.pdf (Size: 381.09 KB / Downloads: 30)
Abstract
Glass dome is a very good component for pressure vessel. A
sphere by two domes becomes very strong pressure vessel.
However, combination with cylindrical housing of the other
material is not good. Young's modulus of glass is 64GPa and is
very low compared with conventional steel, titanium alloy,
aluminum alloy or ceramics, which means that a glass dome
shrinks larger than a cylinder made of the other material. The
glass dome is very strong against outer pressure when it shrinks
evenly, but when it shrinks unevenly by any reasons, tensile stress
or stress concentration on edge of the dome may come out, which
leads to crack and to collapse of the glass dome. The author tested
a glass dome with ceramic cylinder, but it collapsed at a little
higher pressure than the planned operational pressure. Analysis
showed that the collapse was due to the uneven shrinkage of glass
dome. In order to avoid uneven shrinkage of glass dome, the
friction at the rim of glass dome with the supporting structure
must be zero or very small. However, conventional low-friction
material like Teflon sheet is not good for this purpose because of
the plastic flow by the large contact stress. Thus, the author
introduced a special coating technology, Diamond-Like Carbon
(DLC) coating. This coating requires very smooth surface with
Ra<0.02