Gerhard Fiedler <lists@connectionbrazil.com> wrote:
> Dave Tweed wrote:
> > The only way the hole can get smaller is if the material gets
> > considerably softer at high temperatures,
> =

> Check out http://midas.npl.co.uk/midas/content/mn049.html
> =

> Young's modulus of steel seems to decrease linearly up to ~600=B0C (~80% =
of
> the modulus at 0=B0C), and then decrease sharply.
> =

> > or if something nonuniform occurs -- the hole wasn't round to begin wit=
h,
> > the edge buckles, or there's an anisotropic component to the expansion.
> > Any of these might apply to your blacksmiths.
> =

> Right. If any of these apply, don't you say the hole could have become
> smaller?

Please forgive me for jumping into this thread late. I assumed that you
were talking more or less theoretically about round holes in uniform,
isotropic materials, and applying heat in the general region of the hole.

Sure, if any of those things apply, some dimensions of the hole will get
smaller. What's your point?

> They simplify the situation by saying let it first expand thermally,
> then apply stress to bring it back into its original form.

Ah, yes, hypothesizing a container that has no elasticity at all kind of
changes the universe of discussion. In that case, shrinkage of the hole
requires a reduction of modulus, as I said before; otherwise, the hole is
simply returned to (or maintained at) its original size.

I'll jump back out of this thread now. Please carry on.

-- Dave Tweed

-- =

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