On Mon, 20 Apr 2015 12:45:03 -0400, "Jim Wilkins"
wrote:

"Ed Huntress" wrote in message
.. .
On Mon, 20 Apr 2015 10:42:34 -0400, "Jim Wilkins"
wrote:


You could try gently and unobstrusively bending a 3/8" steel rod in
a
hardware store to get a hands-on feel for how stiff steel is, and
isn't.

-jsw


Coat hangers are good for that, too. They're what I use to
demonstrate
the principle to people. When you're talking about how even the
crappiest steel has the same elastic properties as, say, 200,000
psi-yield music wire of the same diameter, it makes a good demo.
Steel
doesn't come much crappier than coat hangers.

--
Ed Huntress

How did you do it?

I usually had a bench vise and drywall screws available in the labs
where I worked. My demo was less convincing in someone's office with
only paper clips and a lighter, though they are enough to show how
fire severely weakens steel.

-jsw

If I'm in my shop, I take a 1-foot length of coat-hanger wire and
round spring wire (I always have lots of music wire around) and clamp
them with a scrap of wood between them, horizontally, in my vise, so
most of the foot of material is hanging out and there's maybe a 1-inch
gap between the two wires.

I wrap a few wraps of string around the outer tip of each, so the
weights won't slip off. Then I tie foot-long pieces of string at the
tips, and tie fishing sinkers to the ends of the string. A couple of
4- or 5-ounce sinkers, IIRC, will show equal bends. Then I lift up on
the sinkers to let the wires spring back.

Then I load on more sinkers until I get a permanent bend in the
coat-hanger wire. The demo shows the equal deflection (close, anyway)
within the elastic limit, and then what "elastic limit" means.

--
Ed Huntress