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Michael Peetros
September 15, 2009
Friction and Wear of Materials
Homework #1
1. The word tribology, literally translated from its components tribos (rubbing) and
-logy (English form of the Greek “logia”, meaning body of knowledge), means
“the study of rubbing.” Though derived from Greek roots, the word tribology
was not actually used first by the Greeks, but rather much later in the year 1966
in The Jost Report. The Jost Report described the large amounts of money lost
in Great Britain due to friction, wear, and corrosion. Now, tribology is
technically known as “the art of applying operational analysis to problems of
great economic significance, namely, reliability, maintenance, and wear of
technical equipment” (Bhushan, 2002).
2. According to CorrosionSource.com, corrosion and wear cost the United States
$440 billion in 1998, when the GDP was about $9 trillion. Based on these
numbers, the losses due to wear, friction, and corrosion amounts to about 4.8%
of the GDP. Currently, the U.S.A. GDP is approximately $14 trillion. Using the
percentage of 4.8, the current losses due to ignorance of tribology in the U.S.A.
is approximately $672 billion, potentially more or less depending on the source
of the estimated percentage. However, most sources put the estimated
percentage of GDP somewhere between 2 and 5 percent, so this is likely a god
approximation given the difficulty in quantifying the actually monetary losses.
Using existing knowledge, approximately 1-2% of the GDP could be saved.
3. In my work experience, I have been involved in the design of a track roller for
the passenger door of an aircraft. The roller must act as a bearing under the
weight of the door when it opens and closes and under cabin pressure during
flight. The following technical/scientific disciplines have a bearing on the
problem and the design of the solution:
Chemistry/Material Science: The self lubricating solid material used
internally within the bearing that I am designing was created by chemists
and material scientists to provide the lowest coefficient of friction and
wear rate while maximizing the material’s load carrying capabilities. The
self lubricating material may also introduce separated particles as it wears,
acting as an additional lubricant.
Material Science/Engineering: Material scientists/engineers selected
the PH13-8MO steel used in much of the interfacing bearing surface of the
track roller bearing, based on its properties under fatigue, the given
stresses in the application, and the corrosion resistance it would offer
when exposed to the elements during operation. Material scientists also
selected the electroless nickel plating on the surface which the track roller
will run for its combination or hardness, resistance against galling with
stainless steels, and its added resistance to corrosion and to extend the
wear life of the track surface.
Heat Transfer: As the roller rides on the mating track, some amount
of heat may be generated due to the associated friction.
Fluid Dynamics: The door guide track roller may be exposed to
contaminants such as water and de-icing fluid, both of which could serve
as a thin film liquid lubricant between either the outer portion of the roller
and the track or the inner components of the roller. These could change
the friction and wear properties of both interfaces.