On Wed, 5 Mar 1997, Dave Williams wrote:
>
> -> ferrous metal is OK to use. Suppose that piece of metal has been
> -> used for MANY hours...under hard loads. i.e. a buddy of mine has an
> -> older airplane. About 8,000 hrs on the engine. He has the
> -> When does a piece of metal become unsafe to re-use even if it meets
> -> specs?. How can you tell in a cost effective way.?
>
> As far as I know you can't tell by looking at it. Eventually the rods,
> crank, or other components will fail due to fatigue, but it tends to be
> a rapid process - if you happened to Magnaflux it just as a crack formed
> you'd be okay, but propagation is rapid in fatigued parts.
This thread reminds me of an old movie, No Highway in the Sky, starring
James Stewart as a "boffin" who calculates that the tail assembly will
fall off a new airplane at x hours. This is just an interesting
engineering problem to him, until he gets on one of the airplanes that is
near his calculated maximum hours.
I believe the movie was based on a book by Neville Schute, but I might
have that wrong.
Ray Gibbons Dept. of Molecular Physiology & Biophysics
Univ. of Vermont College of Medicine, Burlington, VT
gibbons@northpole.med.uvm.edu (802) 656-8910
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