On 8/10/06, Gerhard Fiedler <lists@connectionbrazil.com> wrote:
> William Couture wrote:
>
> > If you heat the middle (containing a hole) of a piece of metal, it will
> > expand.  But the rest of the piece isn't getting out of it's way to make
> > expansion easy.  This introduces stress in the piece of metal.
>
> Right: "introduces stress". So what does this stress do to the hole?
>
> This is a normal situation when (gas) welding, isn't it? I don't think
> people usually heat the complete sheet up to welding temperature when they
> weld a piece to a sheet. So there is then a hot area in the middle,
> surrounded by a cooler area. What happens to a hole in the hot area in the
> middle? (You probably shouldn't try that with cast iron, but that's a
> different story.)
>
> So far even Tony's argument ("'Gadzooks!'") didn't really sound too
> scientific about what happens in this situation to a hole.

I suggest an experiment:
   1) A piece of metal with a hole in it
   2) A THIN-WALLED glass "jar" the exact size of the hole in the metal
       (a light bulb will do)
   3) Appropriate heat source.

Put glass "jar" in hole.  Apply heat.

See if "jar" breaks.   If it does, the hole has shrunk.

If it falls out, the hole has expanded.

Let me know how this turns out.

Bill

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