[Shotimes] Fretting

[Jason Hartberger]

 From the Navy publication on Corrosion (actually it's from chapter four 
of the Aviation Maintenance Ratings [AMR, NAVEDTRA 14022] if you're 
interested, but it's from the 504 originally) states:

Fretting corrosion is a limited but highly damaging
type of corrosion. It is caused by a slight vibration,
friction, or slippage between two contacting surfaces
that are under stress and heavily loaded. It is usually
associated with machined parts. Examples of these
parts are the area of contact of bearing surfaces, two
mating surfaces, and bolted or riveted assemblies. At
least one of the surfaces must be metal. In fretting
corrosion, the slipping movement on the contacting
surface destroys the protective films that are present
on the metallic surface. This action removes fine
particles of the basic metal. The particles oxidize and
form abrasive materials, which further agitate within
a confined area to produce deep pits. Such pits are
usually located in an area that increases the fatigue
failure potential of the metal. Early signs of fretting
corrosion are surface discoloration and the presence of
corrosion products in lubrication. Lubrication and
securing the parts so that they are rigid are effective
measures to prevent this type of corrosion.

Yes, the navy has a publication on everything. Yes, even proper condom 
usage. If it exists, the navy has it documented at length. *sigh*

Jason

George Fourchy wrote:
> On Thu, 17 Feb 2005 17:36:04 -0500, Jim & Debbie Leyden wrote:
> 
> 
>>It is a condition known as
>>"fretting" that occurs when two metal parts work against each other.  
> 
> 
> Interesting....
> 
> I've had several engines apart in the front, and the only one that had anything like
> this sort of appearance was mine, with all the fine metal filings from the crank and
> key spread out all over the place.  It sure looks like small spots of rust on that
> sprocket in the picture.
> 
> Why doesn't this condition occur all the time, or at least, more often?
> 
> By the way, dictionary.com does not have this definition for this word....I checked
> there, just to see if there were synonyms I could check out to find out more about
> the process.
> 
> 
> 
> George
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