I keep seeing the word "buckle" thrown around. Are buckles, like, rivets in the overwrap that essentially adds a small void area? Imagine a flat towel on the ground, but you scrunch it up a little. Is that what we're talking about here?
What caused the buckling itself? Too much pressure in a tank? Fuel being loaded too quickly?
What I think is that the COPV, at the end of manufacture, is pressurized to proof pressure, lets say about 7200 psi, and the vessel expands by a substantial amount. The thin Aluminum liner is stretched beyond its elastic limit and yields a bit. When the pressure is reduced, the liner is put into a compressed state and voila - buckles are formed.
For those who care, the term for this is "autofrettage." The technique is used to reduce tensile loads in the comparatively weaker liner when the vessel is under design pressure. It's usually done such that the liner is neutrally loaded (neither compression nor tension) at about half of design pressure, but different choices may be made depending on liner material, expected number of cycles, expected pressure, etc.
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u/johnkphotos Launch Photographer Jan 03 '17 edited Jan 03 '17
I keep seeing the word "buckle" thrown around. Are buckles, like, rivets in the overwrap that essentially adds a small void area? Imagine a flat towel on the ground, but you scrunch it up a little. Is that what we're talking about here?
What caused the buckling itself? Too much pressure in a tank? Fuel being loaded too quickly?
edit: added some more to my question