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Re: Titanium Disks

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  • the_maniacal_engineer
    There are some things in this post which don t quite mesh with my understanding of material science. Comments are included in-line. ... wrote: ... as
    Message 1 of 9 , Mar 14, 2002
      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...>
      wrote:

      <snip>

      > Marshall, titanium is pound for pound at least five times as strong
      as
      > steel, and it has a higher melting point. Also has more abrasion
      > 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
      strong
      > 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.

      <snip>

      >
      > You can build a TT with steel disks, which won't warp when you pour
      the
      > energy to it, but you would have to make it inordinately heavy and
      broad.

      <snip>

      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.

      <snip>

      > extra mass rotating, the internal stresses can get pretty high. The
      > least bit of imbalance, or the smallest internal flaw or scratch on
      the
      > steel disk, can cause it to explode at very high RPM.
      >
      > This could produce an exciting spray of shrapnel, carrying all the
      way to
      > 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)

      <snip>

      >
      > If you are going to build a high-energy TT, then you should use
      materials
      > that are suitable for very high-stress and severe environments.
      There is
      > certainly some upper limit, past which no amount of steel is going
      to 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.

      Chris
      P.E. and former SR-71 environmental control system Engineer
    • nailzer
      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
      Message 2 of 9 , Jul 28 2:45 PM
        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.
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