Path: utzoo!utgpu!watserv1!watmath!att!cbnews!military
From: raymond%europa@uunet.UU.NET (Raymond Man)
Newsgroups: sci.military
Subject: Liberty Ships
Message-ID: <1990Jul10.024846.10201@cbnews.att.com>
Date: 10 Jul 90 02:48:46 GMT
Sender: military@cbnews.att.com (William B. Thacker)
Organization: AME Dept., Univ. of Arizona at Tucson
Lines: 27
Approved: military@att.att.com



From: raymond%europa@uunet.UU.NET (Raymond Man)

In <1990Jul8.053547.8339@cbnews.att.com> Douglas S. Miller asked about
 Liberty Ships. I have no reference, but from an engineering class,
I learnt that they were mass produced to make up the convoy across the
Alantic. The hull is all welded to speed production. But a very strange
structural failure mode happened later. The hull suddenly broke up in
two in calm water, eg. inside harbor, at near freezing temperature. This
lead to the development of the field of Fracture Mecahnics. Near zero
temperature is sufficient to lower the fracture toughness of steel which
is then so brittle that catastrophic failure can occur following the 
initiation of even a small crack. The seamless joints of the all-welded
hull allowed the cracks to go all the way through and break the ship in
half.
Just call me `Man'. 
"And why take ye thought for "    --   Matt. 6:28
raymond@jupiter.ame.arizona.edu


[mod.note;  The phenomenon is known as the "ductile-brittle transition."
The ductile-brittle transition temperature of steel depends upon the
chemical composition, and it was found at that time that proper alloying
additions could decrease this transition temperature and solve the 
problem.   A more modern implementation took place when designing
steels for use in the trans-Alaskan pipeline.  - Bill ]