Re: Materials testing

Date:         23 Apr 97 02:58:15 
From:         Pete Mellor <>
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Tom Keesling wrote:
> Could anyone point me in the direction for finding materials testing
> procedures in the aerospace industry?  I am particulary interested in
> 316L stainless, aluminum and titanium.  I am in the orthopedic fixator
> business, and would like to test these devices for cracks.

An "orthopedic fixator" is presumably one of those sets of plates,
screws and other stuff used to pin together fractured bones, right?

In 1977 I wrote off my bike and nearly myself in a head-on collision
with a car, followed by a quick double-somersault over the roof.
Among my multiple injuries was a compound fracture of the mid-femur,
which was set using a "Kunchner nail". This is a long metal rod with
an "omega" shaped cross-section, which is inserted down the entire
length of the marrow cavity of the femur, leaving half an inch
protuding from the top of the bone (but covered by flesh, of course)
to facilitate removal once the bone has regrown in a couple of
months' time.

Came the day I was due to have the nail out, and the surgeon waved
a radiograph under my nose showing only a very flimsy regrowth, and
sent me home. A few weeks later, I was strolling along the street
with a friend when I felt an agonising pain in my thigh. My friend
half-carried me to his car and drove me to the hospital, where the
X-ray revealed that the pin itself had completely sheared at the
point of the original fracture. The bone had not reformed, and the
pin alone had been supporting my weight for several months.

Result: a new pin (I keep the broken one as a souvenir) and a bone
graft to ensure proper regrowth this time.

My question to Tom is: Am I the only person apart from Robocop to
have been hospitalized due to metal fatigue? :-)

Peter Mellor, Centre for Software Reliability, City University, Northampton
Square, London EC1V 0HB, UK. Tel: +44 (171) 477-8422, Fax: +44 (171) 477-8585