Page 14 - Tribology in Machine Design

/ Introduction to the concept of

tribodesign

The behaviour and influence offerees within materials is a recognized basic
subject in engineering design. This subject, and indeed the concept of
transferring forces from one surface to another when the two surfaces are
moving relative to one another, is neither properly recognized as such nor
taught, except as a special subject under the heading friction and lubrication.
The interaction of contacting surfaces in relative motion should not be
regarded as a specialist subject because, like strength of materials, it is basic
to every engineering design. It can be said that there is no machine or
mechanism which does not depend on it.
Tribology, the collective name given to the science and technology of
interacting surfaces in relative motion, is indeed one of the most basic
concepts of engineering, especially of engineering design. The term
tribology, apart from its conveniently collective character describing the
field of friction, lubrication and wear, could also be used to coin a new word
- tribodesign. It should not be overlooked, however, that the term tribology
is not all-inclusive. In fact, it does not include various kinds of mechanical
wear such as erosion, cavitation and other forms of wear caused by the flow
of matter.
It is an obvious but fundamental fact that the ultimate practical aim of
tribology lies in its successful application to machine design. The most
appropriate form of this application is tribodesign, which is regarded here
as a branch of machine design concerning all machine elements where
friction, lubrication and wear play a significant part.
In its most advanced form, tribodesign can be integrated into machine
design to the extent of leading to novel and more efficient layouts for
various kinds of machinery. For example, the magnetic gap between the
rotor and stator in an electric motor could be designed to serve a dual
purpose, that is, to perform as a load-carrying film of ambient air
eliminating the two conventional bearings. The use of the process fluid as a
lubricant in the bearings of pumps and turbo-compressors, or the
utilization of high-pressure steam as a lubricant for the bearings of a steam
turbine are further examples in this respect. Thus, it can be safely concluded
that tribodesign is an obvious, and even indispensible, branch of machine
design and, therefore, of mechanical engineering in general.
In any attempt to integrate tribology and tribodesign into mechanical
engineering and machine design, it is advantageous to start by visualizing