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From: WVE~ol.com
Date: Fri, 11 Oct 1996 16:05:27 -0400
Subject: coaxing and strain aging

In a previous post, I quoted Prof. Dieter's definition of coaxing from his
book Mechanical Metallurgy. The quoted paragraph said that metals that
exhibited strain aging also were subject to coaxing. This begged the
question "What is strain aging?" Quoting from the same book:

"Strain aging is a type of behavior, usually associated with the yield-point
phenomenon, in which the strength of a metal is increased and the ductility
is decreased on heating at a relatively low temperature after cold-working."

There are two pages of text on strain aging. Steel is the only metal
discussed in particular in the discussions of coaxing and strain aging.
Strain aging occurs after the yield point. The yield point occurs when the
metal, as it is stressed, begins to bend to the extent that it will not
return to its original shape when the stress is removed. A relatively low
temperature is < 300F. Strength is the maximum stress (greater than the
yield stress) that a metal part will take without breaking. Cold working is
bending, mashing, or stretching metal (without heating it) to change its
shape. Ductility is a measure of the amount of bending/stretching a metal
part will take without breaking. A paper clip is very ductile...a needle is
not ductile but brittle. Stress is the amount of force applied to a part
divided by the cross-section area of that part. Thus a big chain and a small
chain of the same material will break at different forces but approximately
the same stress. Strain is the amount of stretch of a metal part expressed as
a % of its length. These definitions are intended to satisfy laymen, not
engineers who need to know all the exceptions and second-order effects.

I conclude that coaxing and strain aging are not relevant to break-in of
harmonica reeds but I (in spite of owning some books on the subject) am not
an expert in metallurgy. There may be experts yet to be heard from...such as
Scott Mitchell's dad, Larry.

Vern