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RE: disortion from heating

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Roy,

Residual compressive stresses are trapped in steel as it is rolled.  If the
heat is applied uniformly across an entire surface, the residual compressive
stresses are relieved and the heated section contracts.  That is why heat
cambering uses large heated wedges which will contract and camber the beam.

If heat is applied locally, the heat will cause the local area to expand.
Heat straightening is an art.  It is another of the arts that I can't do,
but I can appreciate.

Welding heat is highly localized.  The only thing I can say about your
example is that the plate will distort.

Regards,
Harold Sprague
The Neenan Company
harold.sprague(--nospam--at)neenan.com


-----Original Message-----
From: RoyLevy(--nospam--at)aol.com [mailto:RoyLevy(--nospam--at)aol.com]
Sent: Tuesday, January 05, 1999 5:37 PM
To: seaint(--nospam--at)seaint.org
Subject: disortion from heating


Many years ago I heard of a team of technicians who had developed a
technique
to straighten deformed steel bridge structures  in place by flame-
straightening.
 
To help me understand the principles, this is my question:

Assume a steel plate say 3/8" thick by 4" wide and 3 ft long, simply
supported
at the ends, say resting on a pair of saw horses.   Heat is applied across
the
top at the center, for example by welding a 1/4 x 4 " wide gusset plate at
the
center, across  and perpendicular  to the plate ( 2  3/16"  f illet welds, 4
'' long , for example)  .

Will the center of the plate rise or will it sag ?  In another form, the
question is which will prevail -  The loss of rigidity while the top is
molten
or the contraction effect upon cooling?