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From: WVE~ol.com
Date: Wed, 9 Oct 1996 16:08:59 -0400
Subject: Break-in & coaxing

On 10-8-96 Scott Mitchell and his father Larry contributed to the break-in
debate by describing a process called "coaxing" wherein the fatigue life of a
metal part is extended by cycling at lower stress levels. They referred to
papers by Lehr and Herold in the German language.

The following paragraph on coaxing is from a textbook, Mechanical Metallurgy,
Second Edition by George E. Dieter, Prof of Eng. and Dir. Processing Research
Inst, Carnegie-Mellon U. in Pittsburgh. The emphasis is mine.

"IF a specimen is tested without failure for a LARGE NUMBER of cycles below
the fatigue limit and the stress increased in SMALL INCREMENTS after allowing
a LARGE NUMBER of cycles to occur at each stress level, it is found that the
resulting fatigue limit may be as much as 50 percent greater than the initial
fatigue limit. This procedure is known as COAXING. An extensive
investigation of COAXING (G. M. Sinclair, American Society of Testing
Material, Proceedings vol.52, pp 743-758, 1952) showed a direct correlation
between a strong coaxing effect and the ability for the material to undergo
strain aging. Thus, mild steel and ingot iron show a strong COAXING effect,
while BRASS, aluminum alloys, and heat-treated low-alloy steels show little
improvement in their properties from COAXING."

The cycling regimen to induce coaxing does not seem to be met by the break-in
procedures described in recent posts. The reed material does not seem to be
the type for which coaxing is effective. It would be interesting to dig up
the Sinclair reference.

Vern