[AR] Re: Project update - propellant tank hydro tests
- From: Henry Spencer <henry@xxxxxxxxxxxxxxx>
- To: Arocket List <arocket@xxxxxxxxxxxxx>
- Date: Thu, 21 Nov 2013 23:34:50 -0500 (EST)
On Thu, 21 Nov 2013, Robert Watzlavick wrote:
> I hadn't thought about the screws on the outside of the tank becoming
> brittle. I assumed they would just get stronger as they're the normal
> alloy cap screws (180 ksi typ)...
The two are not incompatible, alas. Metals *do* generally get stronger at
cryo temperatures; the reason why some get brittle is that their yield
strength increases faster than their ultimate strength does, and when the
two curves cross over, the ductility is gone.
My understanding is that there is no substitute for test data on the exact
alloy used, but non-stainless steels generally should be viewed with some
suspicion. (For that matter, not all stainless steels are immune to the
problem, although the odds are much better.)
You could always dunk a few in LN2 for a minute, and then apply a hammer
and see what happens!
Henry Spencer
henry@xxxxxxxxxxxxxxx
(hspencer@xxxxxxxxxxxxx)
(regexpguy@xxxxxxxxx)
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