Re: Questions about the DH Comet

Date:         25 Sep 97 01:39:44 
From: (Gerard Foley)
Organization: The Greater Columbus FreeNet
References:   1 2 3 4 5
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David Lesher ( wrote:
: J& (Janet and John) writes:

: >>Any strength of materials textbook.....

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

Fatigue failure has been recognized for more than 70 years, and the
behavior of many materials was well known before WWII.

: By some measures, the entire field of fatigue behaviour started
: only a few years before, when the Allies tried to figure out why
: brand new Liberty Ships in the North Atlantic were suddenly
: cracking in half and sinking.

The failure of welded ships in cold weather does not involve
fatigue.  It is a result of brittleness (measured by impact
testing) at reduced temperatures.  It is true that the subtle
variations in steel making that raise the temperature at which
brittle failure occurs was not well known when welded ships
became common.  Rivetted ships relieved themselves of stress
by having the steel plates shift by small amounts, but with so
many plates and joints as to amount to a considerable increase
in stress relief.

: The history of any technological development is strewn with the
: victims of its failures along the way. This is no exception.