Bearings Types of Damages and Their Causes: Kushal Dhungana Ab13 Professor: José Brigas and Pedro Alves Indice

BEARINGS
TYPES OF DAMAGES AND THEIR CAUSES
Kushal Dhungana
Ab13
MODULE 7
PROFESSOR: JOSÉ BRIGAS AND
PEDRO ALVES
INDICE
INTRODUCTION--------------------------------3
1
BEARINGS----------------------------------------4
WHY ARE THEY IMPORTANT? --------------5
TYPES OF BEARINGS
 PLAIN BEARINGS--------------------------6
 BALL BEARINGS---------------------------7
 ROLLER BEARINGS-----------------------8
TYPES AND CAUSES OF DAMAGES-------9
TYPES AND CAUSES OF DAMAGES------10
TYPES AND CAUSES OF DAMAGES------11
CONCLUSION----------------------------------12
BIBLOGRAPHY-------------------------------13
INTRODUCTION
In this project we will learn about bearings. This is one of the
many projects of module 7 that we are doing in order to fulfil our
practical hours that we couldn’t do due to Covid-19.
2
Bearings is one of the important parts in an aircraft. It is useful to
reduce friction between the movable parts. They help to move the
movable parts easily. In this project we will learn about what are
bearings, and why they are important. We will also learn about
what are the different types of bearings, what causes them to
wear and what are the various methods of prevention to protect
them.
Since they can be delicate and small as well as large like in some
parts of airplane, care should be taken while protection and
handling these tools. We will take reference from the manual of
module 7 that is available in Moodle as well as various sites of the
internet for the better understanding of bearings.
BEARINGS
Bearings are "parts that assist objects' rotation". They support

the shaft that rotates inside the machinery. Machines that use
bearings include automobiles, airplanes, electric generators and so on.
They are even used in household appliances that we all use every day,
such as refrigerators, vacuum cleaners and air-conditioners. Bearings
support the rotating shafts of the wheels, gears, turbines, rotors, etc. in
those machines, allowing them to rotate more smoothly.
3
In this way, all sorts of machines require a great many shafts for
rotation, which means bearings are almost always used, to the point
where they have become known as "the bread and butter of the
machine industry". At first glance, bearings may seem like simple
mechanical parts, but we could not survive without bearings.
A good bearing must be composed of material that is strong enough to
withstand the pressure imposed on it and should permit the other
surface to move with a minimum of friction and wear. The parts must
be held in position within very close tolerances to provide efficient
and quiet operation, and yet allow freedom of motion. To accomplish
this, and at the same time reduce friction of moving parts so that
power loss is not excessive.
WHY ARE THEY IMPORTANT?
Bearings has an important role in the movement of movable

parts. Two of the main importance of bearings are as follows.
1: Reduce friction and make rotation more smooth
Friction is bound to occur between the rotating shaft and the
part that supports the rotation. Bearings are used between
these two components.
The bearings serve to reduce friction and allow for smoother
rotation. This cuts down on the amount of energy consumption.
This is the single most important function of bearings.
2: Protect the part that supports the rotation, and maintain
the correct position for the rotating shaft
4
A large amount of force is needed between the rotating shaft
and the part that supports the rotation. Bearings perform the
function of preventing damage from being done by this force to
the part that supports the rotation, and also of maintaining the
correct position of the rotating shaft.
TYPES OF BEARINGS
There are mainly three types of bearings that are in general use.
They are plain bearings, roller bearings and ball bearings.
Plain Bearings
Plain bearings are generally used for the crankshaft, cam ring,
camshaft, connecting rods, and the accessory drive shaft bearings.
Such bearings are usually subjected to radial loads only, although
some have been designed to take thrust loads. Plain bearings are
usually made of nonferrous (having no iron) metals, such as silver,
bronze, aluminium, and various alloys of copper, tin, or lead. Master
rod or crankpin bearings in some engines are thin shells of steel,
plated with silver on both the inside and the outside surfaces and with
lead-tin plated over the silver on the inside surface only. Smaller
bearings, such as those used to support various shafts in the accessory
section, are called bushings. Porous Oolite bushings are widely used
in this instance. They are impregnated with oil so that the heat of
friction brings the oil to the bearing surface during engine operation.
5
Plain bearings
BALL BEARINGS
A ball bearing assembly consists of grooved inner and outer races,

one or more sets of balls, in bearings designed for disassembly, and a
bearing retainer. They are used for shaft bearings and rocker arm
bearings in some reciprocating engines. Special deep-groove ball
bearings are used to transmit propeller thrust and radial loads to the
engine nose section of radial engines. Since this type of bearing can
accept both radial and thrust loads, it is used in gas turbine engines to
support one end of a shaft (radial loads) and to keep the shaft from
moving axially (thrust loads).
6
BALL BEARINGS
ROLLER BEARINGS
Roller bearings are made in many types and shapes, but the two types
generally used in the aircraft engine are the straight roller and the
tapered roller bearings. Straight roller bearings are used where the
bearing is subjected to radial loads only. In tapered roller bearings, the
inner- and outer-race bearing surfaces are cone-shaped. Such bearings
withstand both radial and thrust loads. Straight roller bearings are
used in high power reciprocating aircraft engines for the crankshaft
main bearings. They are also used in gas turbine applications where
radial loads are high. Generally, a rotating shaft in a gas turbine
engine is supported by a deep-groove ball bearing (radial and thrust
loads) on one end and a straight roller bearing (radial loads only) on
the other end.
7
ROLLER BEARINGS
TYPES AND CAUSES OF DAMAGES

Since bearings are movable parts and they also have to support
various loads, they are subject to various types of damages during
their lifetime. Proper inspection should be made on them to prevent
the further damage and proper functioning of aircraft. Some of the
damages that generally occur in bearings are as follows.
Wear, abrasive contamination
Foreign material (i.e., sand, fine metal) in the bearing can cause
excessive abrasive wear. In tapered bearings, the roller ends and cone
rib will wear to a greater degree than the races. This wear causes
increased end play or internal clearance, which can reduce fatigue life
and create misalignment in the bearing.
8
Excessive heat generation caused complete seizure of this bearing.
Inadequate lubrication
It’s important that the right lubricant amount, type, grade, supply
system, viscosity and additives be properly engineered for each
bearing system. Selection should be based on history, loading,
speeds, sealing systems, service conditions and expected life.
Without proper consideration of these factors, bearing and
application performance may be underwhelming.
Misalignment
Misalignment will shorten bearing life depending on the degree of
misalignment. To achieve longer life, the seats and shoulders
supporting the bearing must be within the specified limits set by the
manufacturer. If the misalignment exceeds those limits, the load on
the bearing won’t be distributed along the rolling elements and
races as intended.
Handling and installation damage
9
Care must be taken when handling and assembling bearings so the
rolling elements, race surfaces and edges aren’t damaged. Deep
gouges in the race surface or battered and distorted rolling elements
will make metal rise around damaged areas. High stresses will
occur as the rolling elements go over these surfaces, creating
premature, localized spalling.
failure of ball bearing

Brinell and impact damage
Brinelling from improper bearing assembly and disassembly
happens when a force is applied against the unmounted race. When
mounting a bearing on a shaft with a tight fit, pushing the outer race
will exert an excessive thrust load and bring the rolling elements
into sharp contact with the race, causing brinelling. Extremely
heavy impact loads can also result in brinelling of the bearing races,
or even fracture the races and rolling elements.
False brinelling
False brinelling is fretting wear caused by slight axial rolling-
element movements while the bearing is stationary. Vibration can
make the rolling element slide back and forth across the race,
wearing a groove into it. Roller bearings also exhibit false
brinelling when used in positions that encounter very small
reversing angular oscillation – less than one complete rotation of
the rolling element.
To distinguish false brinelling from true, examine the depression or

wear area. False brinelling will wear away the surface texture,
whereas the original texture will remain in the depression of a true
Brinell.
10
CONCLUSION
Bearings are the mechanical parts that make the world go round.
Bearings play a crucial role in our daily lives, but it is precisely
because of their importance that we must constantly strive to make
them more precise and durable. Additionally, it is vital to the
development of machine technology that we continue going forward
to develop bearings that can work under ever harsher and more
specialized conditions.
Bearings will no doubt continue to evolve and change, and to improve
our livelihoods by "making the world go round".
Through this project we learned a lot about bearings and why they are
important. We also learned what could cause bearings failure and as
well as what types of bearings are used in aviation industry. We
learned a lot from the module 7 English manual and as well as from
the various sites of internet which will be mentioned in bibliography.
11
BIBLOGRAPHY
https://koyo.jtekt.co.jp/en/2019/06/column01-01.html
https://www.pitandquarry.com/determining-types-of-bearing-damage/
ENGLISH MANUAL OF MODULE 7.
12

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BEARINGS

TYPES OF DAMAGES AND THEIR CAUSES

Bearings are "parts that assist objects' rotation". They support

WHY ARE THEY IMPORTANT?

Bearings has an important role in the movement of movable

A ball bearing assembly consists of grooved inner and outer races,

TYPES AND CAUSES OF DAMAGES

Handling and installation damage

failure of ball bearing

To distinguish false brinelling from true, examine the depression or

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