Properties and Application of Engineering Materials

This document explores the properties and applications of engineering materials in the development of a mountain bicycle frame, gear set, and braking system. It discusses the use of metals, composites, and thermoplastics in frame manufacturing, and the different materials used in gear systems. It also examines the characteristics of brake pad materials and their selection for optimal performance.

Running Head: PROPERTIES AND APPLICATION OF ENGINEERING MATERIALS 1
: PROPERTIES AND APPLICATION OF ENGINEERING MATERIALS
Name
University

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Task one: Introduction
A Mountain bicycle is designed to handle the roughest terrain while maintaining the
highest level of performance. The bike needs to handle single tracks, fire roads, and other
unpaved surfaces. The ground is mostly occupied with rocks, loose gravel, steep gradients, and
muddy areas (Brongersma, Halas, & Nordlander, 2015). The Manufacture and performance of a
new model of a bicycle depend majorly on the engineering materials selected. The new product
has to meet low production cost and aesthetic expectations of a customer (Smith & Suzuki,
2018). The engineering materials present today which can be used in the bicycle development
are metals, polymers, ceramics, composites and smart materials (Ashby, 2012). Minerals are a
group of engineering materials which are opaque and lustrous. They are good conductors of heat
and electricity. Polymers consist of a class of natural or synthetic substances made up of large
repeating chains of molecules. The next level of materials is known as ceramics which includes
an inorganic compound of metal and a non-metal held by both ionic and covalent bonds.
Composites, on the other hand, constitute two or more materials combined with a material with
different characteristics from individual elements (Aguilar, 2019). Lastly, smart materials
possess one or more properties which can be significantly changed in a controlled manner by
external stimuli.
Task two: Development of the bicycle frame and gear set
I. bicycle frame
A bicycle frame is made to have maximum stiffness and performance (Ashby, 2012). The
structure accommodates both axial and torsional loads which are experienced in cycling. The
structure must be strong to support the own rider weight without compromising the bicycle’s

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performance. During operation, the bicycle frame is subjected to tear and wear (Callister, 2007).
The structure has to be light enough and comfortable to the rider. The main frame components
include front fork, seat post, headset, and bottom bracket. Some materials can be used in
attaining the best capabilities of the bicycle frame, or a single element can be selected. The
excellent article (s) will enable the bicycle to operate under extreme conditions efficiently and
pose little or no manufacturing challenge. The conventional materials used in the manufacture of
the frame are metals or their alloys, composites, and thermoplastics.
Metals
Metals which are used in frame manufacture include aluminum, steel, titanium, and
magnesium. Metals have a good machinability capability which is economical in terms of low
production cost. Metals also have a high modulus of elasticity and show adequate stiffness of
within a huge load span. Metals have high strength of up to 1600 mega Pascal (Mpa) (Ashby,
2012). Corrosion can be controlled easily in metals by coating the metal surface. The mode of
joining in metals is by use of mechanical fasteners, welding and riveting. Also, metals are not
affected by the conversion process except in solder where local heat affected zones (has) occur
due to local heating. During machining of metals, little or no change occurs to the metal structure
hence retaining the original characteristics. Metals have high densities making them not suitable
material for the frame. During the operation period frames made of metals retain their properties
for an extended period. Rework, and maintenance of structures built of metals is easy. Quality
inspection in metals is easy. Nondestructive tests Methods which are used to inspect the metals
are magnetic particle testing, ultrasound and electromagnetic testing make testing of metal
products easy (Callister, 2007).

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Composites
The most common composite used in structure development is carbon fiber. It offers the
advantage of low weight, stiffness, and durability (Joshi, 2017). Carbon fiber body frame can
handle torsional and axial loads efficiently due to its high fiber stiffness. Carbon fiber saves on
the production cost because it does not need secondary manufacturing processes like polishing.
The aesthetic level of carbon fiber is good since colors and texture can be customized. The
structure of carbon fiber enables the building of a light frame which is a desirable feature for any
mountain bicycle (Aguilar, 2019). During the operation cycle, carbon fiber is durable, and it can
retain and release shock due to terrain irregularities. Little energy is used for the propulsion of
the bike through the steep gradient of the terrain due to the overall weight of the bicycle (Tsai,
2018).
Thermoplastics
This is a group of polymers which can be reheated and reshaped into different forms.
Thermoplastics have an excellent product finish saving cost for possible secondary production
processes .thermoplastics have low ability to absorb shock (Peres, Pires, & Oréfice, 2016). The
polymers have low elastic modulus hence low strength (Callister, 2007). Thermoplastics are
affected by high temperatures therefore not desirable to be used in high heat generating areas in
the bicycle.
II. Gear set
Transmission of power in a bicycle is done through a game of gears system. The gear
materials should be having a low coefficient of friction, be self-lubricating, have sufficient

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strength, conduct the heat emitted during power transfer, have an excellent surface finish and low
production cost (Ashby, 2012). Gear materials include a wide range of steel, brass, bronze, cast
iron, and plastics. Steel is the most common material with a combination of desirable
characteristics of high strength to weight ratio, resistance to wear is relatively high and has a
competitive pricing. During operation of the bicycle, steel made gears will be able to handle the
extreme pressure peaks which will provide a smooth ride (Álvarez, Famá, & ", 2017). The gear
system will absorb shock generated by rough terrain the mountain bicycle is designed to operate
in. Gears made from steel, brass or cast iron have a setback of noise production during their
operation. Steel made gears need quality and precise machining to eliminate vibrations produced
during the bicycle operation. Steel made speeds are slightly affected by the machining process
like grinding and forging. During machining and forging steel can be hardened in local areas
hence affecting its overall performance (Ashby, 2012).
Plastics form another type of gear material because of their ability to operate
noiselessly while emitting less heat as compared to the steel made gears. Plastic gears have a
good surface finish reducing the coefficient of friction to a manageable level (Meier, 2019). The
surface roughness of any material affects how the surfaces interact when there is relative motion
between them. The disadvantage with the plastic gears is the maximum limit of stress it can
handle, plastics gears operate within a narrow range of working pressure (Wan & Takahashi,
2016). During operation, the plastics gear system will run smoothly with less noise but within a
close range of the working temperatures. High temperature can contribute to melting or softening
of the gear train affecting the transmission efficiency (Jones, 2018).
Task three: The braking system of bicycle

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Braking system reduces the speed of a bike, brings to a halt or prevents the bike from
moving. The braking system comprises of levers, cables, and brakes. The most common types of
brakes include rim brakes, disc brakes, and drum brakes. The kinetic energy is given by the
equation e=0.5 mv2 (Ashby, 2012). Where e is the kinetic energy possessed by a moving object,
with mass m and which is moving with velocity v. The kinetic energy must be converted into
other forms of power for the bicycle to stop or reduce its velocity. The braking system uses the
friction method saving the kinetic energy to other forms of energy. The different types of energy
to which the kinetic energy is converted to include mostly heat and sound power (Ashby, 2012).
Good brake pad materials must possess characteristics which will give an ultimate result within
the changing conditions in the brakes (Jennings, 2018). Brake pad materials should have
sufficient high friction level to ensure the rider uses minimal brake pedal effort (Callister, 2007).
The friction level should not be so high to avoid cases of a lock. The average coefficient of
friction pad materials is between 0.3 and 0.5 (Jones, 2018).
Brake Pad materials should be resistant to heat fade. The resistance to heat fade assists
the pad material to retain the coefficient of friction within the range of rubbing temperatures the
brakes are subjected to. The ratio of conflict slightly changes with increasing temperatures
possibly because of the materials curing. This lowers the brakes ability to offer resistance
making it dangerous especially along steep gradient slopes. Recovery from fade is another
desirable characteristic of pad materials. This is the ability of friction materials to return to its
initial friction level after cooling when temperatures go down. Good pad material can recover
quickly on cooling even after successive heating and cooling scenario. There is no significant
change in the ability of the brake during and after temperature change. Inferior brake pad
materials crack, char or even break down after repeatedly heating and a cooling situation in the

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bakes. The friction coefficient is significantly altered or changed permanently in poor quality
materials. Brake materials are subject to high rubbing wear. Wear at the brakes is excellent due
to high pressure and speed experienced between the brake pad materials and the tire. Also, high
rubbing temperatures encourage wear. Good quality materials can resist the high rate of wear
experienced while materials of inferior quality wear easily. Low quality brake materials translate
to the high cost which is undesirable. Resistance to rubbing speed is the characteristics of
another material which must be determined for brake materials. In practical, the coefficient
between two rubbing surface slightly reduces with increase in speed although it should be
independent of speed (William F, 2006). Low-quality materials exhibit a high coefficient of
friction causing grab at low rates. Pressure increases drastically when the brakes are applied.
Brake pad materials should be independent of the intensity of tension between the rubbing
surfaces. Brake materials are mostly compounds held together by binders. Stable pressure
materials translate to deceleration proportional to the force applied — elements which are
unstable concerning pressure exhibit inferior performances. Brake materials are designed to
produce the desired results even when they have been contaminated by water. High-quality
materials should be able to recover within the shortest time possible from water contamination
(Gebretsadik, Hardell, & Prakash, 2016).
Moisture sensitive materials should be avoided due to their high self-energizing
characteristics. Resistance to moisture sensitivity is an essential characteristic of brake materials,
and it minimizes the grab situation (Callister, 2007). Atmospheric dampness or dew increase the
friction level in the first instance. In a short time, it can increase brake noise. Moisture sensitive
brake, materials should be avoided because of their high self-energizing characteristics Noton,
2016). The heat generated in the brakes must also be conducted away quickly. Brake materials

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need to have a high thermal conductivity coefficient. This applies to the bicycles which use disc
brake mechanisms where the heat energy must be conducted way efficiently.
Justification of selection of brake pad materials
A mountain bicycle will experience quick acceleration, deceleration within a few
seconds, humid climate and many more unknown parameters. Brake materials which meet the
high demand which translates to top performances must be selected. Most of the materials have
their advantage and limitations. Sintered metals exhibit have a low coefficient of friction but
exhibits long life of service. When Ceramics are mixed with minerals, they forma very rigid
brake material which demonstrates a high coefficient of friction. Brake materials constituting of
less asbestos and soft metals like brass have been developed through asbestos suffers a drastic
reduction in factor during operation (Aguilar, 2019). Brake discs have been made of high-grade
steel which is durable. The high thermal conductivity enables the heat energy produced is
conducted way easily phenomena which is boosted by air cooling. The steel brake discs are
accessible to machine, and they also contribute to the aesthetic importance of the brake system
(Callister, 2007). The two main brake materials which fit the dynamic conditions of the brake
system in a mountain bicycle are steel disc and ceramics mixed with metals. These two materials
serve the essential functions of the brake materials.

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