Re: Questions about the DH Comet

Date:         17 Sep 97 02:49:24 
From:         shafer@ferhino.dfrc.nasa.gov (Mary Shafer)
Organization: NASA Dryden Flight Research Center, Edwards CA
References:   1 2 3 4 5
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On 11 Sep 97 03:35:30 , gfoley@freenet.columbus.oh.us (Gerard Foley) said:

G> Janet and John (J&J@nospam.demon.co.uk) wrote:

G> : On 29 Aug 97 08:10:43 , in
G> <airliners.1997.2000@ohare.Chicago.COM>, : michael piersdorff
G> wrote: : >My understanding of the problem was that most of the
G> in-flight : >breakups were explosive decompressions of the fuselage
G> resulting from : >fatigue failure ... Any strength of materials
G> textbook will show that : >a square-ish corner is a tremendous
G> stress raiser in a tension stress : >situation, as a pressurised
G> fuselage most certainly is.  The solution, : >of course, was to go
G> to the more or less oval windows one sees today.

G> : You should say "any strength of materials textbook written since
G> the : Comet crash investigations". Fatigue behaviour was not well
G> known at the : time, and the Comet crashes aided the development of
G> the science : immeasurably,

G> As a person working on endurance (fatigue) testing of materials
G> (including uranium as well as duralumin) in the period 1940-1945 I
G> take issue with the statement.  I believe poor calculation of
G> stress raising, or complete neglect of pressurization cycles as a
G> source of fatigue stress, was the reason for the fault.

However, fatigue was sufficiently mysterious that Nevil Shute could
write "No Highway" (the movie was "No Highway in the Sky" with Jimmy
Stewart, I think) some time between 1945 and 1950 and present fatigue
failure as a phenomenon with no accepted explanation.  Since he was an
aeronautical engineer, I don't think he'd have written this had
fatigue been a sufficiently well-explained phenomenon at the time.
--
Mary Shafer               NASA Dryden Flight Research Center, Edwards, CA
SR-71 Flying Qualities Lead Engineer     Of course I don't speak for NASA
shafer@ferhino.dfrc.nasa.gov                               DoD #362 KotFR
URL http://www.dfrc.nasa.gov/People/Shafer/mary.html
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