Re: Titanium Disks
- There are some things in this post which don't quite mesh with my
understanding of material science. Comments are included in-line.
--- In TeslaTurbine@y..., "Kent L. Aldershof" <Aldershof-MSI@J...>
> Marshall, titanium is pound for pound at least five times as strongas
> steel, and it has a higher melting point. Also has more abrasionstrong
> resistance. That's why they use it to build Mach 3 aircraft, space
> shuttles, and the like. A titanium disk of .020" is every bit as
> as the much heavier steel disk of .050".<snip>
Titanium and steel both have similar tensile strengths, somewhere
between 125~200kpsi, depending on temper. Ti metallurgy is complicated
with alpha and beta phase alloys, similar in concept to the idea of
martensitic and austenitic steels.
> You can build a TT with steel disks, which won't warp when you pour
> energy to it, but you would have to make it inordinately heavy andbroad.
Ti has the strength of steel, but the stiffness is closer to that of
aluminum, the density is somewhere in between. So Ti structures have a
lower frequency than the equivalent in Al or steel.
> extra mass rotating, the internal stresses can get pretty high. Thethe
> least bit of imbalance, or the smallest internal flaw or scratch on
> steel disk, can cause it to explode at very high RPM.way to
> This could produce an exciting spray of shrapnel, carrying all the
> the next county,<snip>
This is true for ANY rotating machinery, The amount of energy that is
released in the failure is the rotational kinetic energy (substantial)
minus the energy it takes to rupture the disc (usually very small)
> If you are going to build a high-energy TT, then you should use
> that are suitable for very high-stress and severe environments.There is
> certainly some upper limit, past which no amount of steel is goingto be
> as good as using a disk of titanium or inconel.<snip>
Titanium is nice, but it isn't kryptonite or anything either. At high
temperatures it is sensitive to Chlorine and other halogens, as well
as cadmium. On the SR-71 (the aforementioned mach 3 airplane) ALL
tools had to be specially treated and periodically checked to make
sure that they had no cadmium. Parts had to be heat treated in
specially de-chlorinated water. No PVC, neoprene, or other chlorinated
polymer could be used on the plane. A better material might be rene41,
waspalloy, or hastelloy. regardless - use a scatter shield (blast
shield is a better term) The SR-71 air conditioning turbine/compressor
set (with known defects) was spun up to 120 KRPM in qual testing and
when it failed the pieces were unrecognizable - a lot of energy.
released in a short time - enormous power - like dynamite.
P.E. and former SR-71 environmental control system Engineer
- Is the person that was selling titanium disks still around? I read
some earlier posts about the disks he was selling and was wondering
if he had anymore for sale.