INDUSTRIAL TRIBOLOGY
UNIT-I
1.1 Introduction
The word tribology was first reported in a landmark report by Jost (1966). The
word is derived from the Greek word tribos meaning rubbing, so the literal
translation would be "the science of rubbing." Its popular English language
equivalent is friction and wear or lubrication science, alternatively used. The latter
term is hardly all-inclusive. Dictionaries define tribology as the science and
technology of interacting surfaces in relative motion and of related subjects and
practices. Tribology is the art of applying operational analysis to problems of great
economic significance, namely, reliability, maintenance, and wear of technical
equipment, ranging from spacecraft to household appliances. Surface interactions in
a tribological interface are highly complex, and their understanding requires
knowledge
of
various
disciplines,
including
physics,
chemistry,
applied
mathematics, solid mechanics, fluid mechanics, thermodynamics, heat transfer,
materials science, rheology, lubrication, machine design, performance, and
reliability.So study of friction ,wear and lubrication(tri-three discipline ) it’s called
Tribology as shown in fig.1.1
Fricti
on
Wea
r
Lubricati
on
Tribology
Fig.1.1 tri-three discipline
1.1.1 Industrial Tribology
Tribology locates the applications in all industrial sectors to investigate the
question of lubrication education, research and the needs of industry as
followed.

Aerospace industries

Automotive industries

Construction industries

Textile industries

Mining industries

Petrochemical machinery & tools

paper mill , transport

Power plant

Steel plant

Cement plant

Military vehicles

Transport

Metallurgy Equipments

Agriculture and food industries
1.1.3 Friction
Friction is a force that opposes the relative motion between two surfaces of
objects in contact. The force of friction always acts in a direction of opposite to
the applied force as shown in fig 1.2. The Friction exists between two surfaces
due to irregularities on the surfaces of the objects in contact or interlocking of
micro-level irregularities of the two surfaces or ploughing of harder surfaces into
smoother surfaces.
1.2 Friction
1.1.4 Types of friction
The Friction is classified in to four types according to the contact between two
surfaces.
(i)
Object is not moved
(ii)
Object is moved
(iii)
Objects is rolling and objects moving in liquid or air as shown in fig 1.3
Friction
Static
Sliding
Rolling
Fluid
Fig.1.3 Types of friction
1.2 Dry friction
When two solid surfaces are in micro contact or macro contact without aid of air
or liquid it’s described the dry friction and examples of dry friction is static and
sliding friction. The fluid is resist to the object while object is moving to the fluid
surface it’s called as fluid friction, in this chapter gives details information of dry
friction and theory of dry friction
i) Static friction: The Pushing force and opposing forces are equal then object is
not moved its called as static friction or else solid object is motionless with self
weight. The examples are

Pushing the wall

Pushing the lathe machine

Books rest on table

Man rest on chair or standing on ground etc…
ii) Sliding friction: When the two surfaces encompass sliding relative to each other
then friction two surfaces is known as sliding friction or solid friction .the examples
are

Pushing or pulling the book on table

Ice skating

Computer mouse moving on table

Oldham’s coupling rectangular bar sliding over the one surface to another
surface.

Reciprocating mechanism

Tail stock moving over the Lathe bed etc….
iii) Rolling friction: when one surface is rolling over to another surface then
generated friction between the two surfaces is known as rolling friction. The
examples are

Tyre moving on road surface

Train wheel on track

Elevator wheel on rail

Iron balls rotating in bearing (rolling iron ball between inner recess and outer
recess)
iv)Fluid friction: when solid object slides through the water or air it’s known as
fluid friction

Water flow in pipe (water slides against pipe)

Swimming (man sliding on water)

Flight flying (flight sliding on air)
Fig. 1.4 Static, Sliding and Rolling Friction
The static friction, sliding friction and rolling friction coefficient are high, medium
and low respectively as shown in fig. Here assume the pushing force and block is
same for all the friction,

Solid is not moved (static friction)

Solid is moved at X1 distance (Sliding friction)

Solid is moved X2 (Rolling Friction)
1.2.1 Variables in dry friction
In automobile braking application after applying braking force the brake shoe
contact with the brake drum in dry conditions then the contacting surfaces are free
from oxide and moisture. The variables in dry friction are

Friction co efficient of soft material

External load

Surface roughness

Linear velocity or angular velocity

Types of contact and energy dissipation and dry friction as show in fig 1.5
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