> In explaining this whole thread to an officemate ("so now 
> here's a topic to get a bunch of engineer's in a room arguing 
> about") I came up with these thought models:
> 
> For this test case I assumed the "problem" was:
> Given a sheet of metal with a hole in it, where the hole is 
> subject to local heating that is significantly greater 
> (exponentially) than the temperature of the remaining sheet, 
> will the hole become smaller?  If not then either the 
> material will expand sideways, or the material will expand 
> outward and stress the rest of the sheet, or both.  ( 
> alternately the material is pushed into another dimension :-)
> 
> So the two test cases are as follows:
> 
> Assume an inelastic material with a hole in it.  Place a 
> ceramic liner inside the hole.  place a metal 
> washer/donut/etc into the ceramic liner.
> 
> Now you have a hole in a chunk of metal inside a hole that's 
> insulated from the external material which will no expand.
> 


Everyone is happy with the conditions, just not the outcome.  

We've settled on steel, no weird stuff like case hardening, in the form of a
cylinder.  The cylinder is 200mm in diameter, and 200mm high.  The hole
bored thru the middle is 10mm.  Being thick it won't warp like sheet metal
will.  (200mm = ~8", 10mm = 3/8")

The hole is heated aggressively, but not to the point where the steel loses
strength, melts, etc, so 500 degrees celcius is probably enough.  A metre of
steel will lengthen by 6mm at 500C, so the hole diameter will only change by
0.06mm.  An eyeball test isn't going to cut it :)

Everone agreed that if heated evenly, the hole gets bigger.  The question is
if the hole is heated rapidly, can the tensile strength of the cold steel
(the outside of the cylinder) overcome the pressure caused by the hole
trying to expand.  Does the hole say - well, got to go somewhere, might just
fill up the hole.  Or does the cold steel stretch?

There's nothing except the metal and heat.  No clamps etc.  No cast iron
because it would crack and so on.

The cylinder seems to have become only 20mm thick lately, but that should
still be ok.

Tony

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