analysis on bicycle crank arm using tensile test
TRANSCRIPT
ANALYSIS ON BICYCLE CRANK ARM USING TENSILE TEST
SHAIFATUL SHIMA BINTI SHAARI
This report is submitted in partial fulfillment of the requirement for the
Degree of Bachelor of Mechanical Engineering
(Design & Innovation)
Faculty of Mechanical Engineering
Universiti Teknikal Malaysia Melaka
APRIL 2010
“I hereby declared that I have read through this report and found that is has comply the
partial fulfillment for awarding the degree of Bachelor of Mechanical Engineering
(Design & Innovation)
Signature : ……………………………………….
Supervisor’s I Name : ……………………………………….
Date : ………………………………………..
i
ACKNOWLEDGEMENT
Assalamualaikum, firstly I would like to thanks God because on his mercy I
finally able to complete my final year project of Analysis on Bicycle Crank Arm
Using Tensile Test. I would like to express my deepest appreciation to my supervisor
Mr Asri Bin Yusuff, and also for his invaluable support, guidance, encouragement,
criticism, and insight throughout the research. It was a great pleasure for me to work
with him. And also to Miss Siti Nor Baya Binti Sahadan as my mentor for helped me
to finished up this project.
For many valuable encouragements and discussions on my project, I am
indebted to my colleagues at Universiti Teknikal Malaysia Melaka (UTeM), who has
also involved during the project. I am also grateful to all technicians from structure
department especially to Mr Rashdan Bin Seman who has been an indefatigable
advisor; teach the procedure for my experiment which include to handling the
machine and all the equipment in the laboratories for helping me in my final year
project.
I would like thanks to UTeM for its facilities and resources mainly in the
library, laboratory and their up-to-date equipment. It has indeed been a great help for
me in reducing my expenses and obtaining precise reading and measurement for my
research.
ii
ABSTRACT
The mechanical properties of a material are directly related to the response of
the material when it's subjected to mechanical stresses. The results of tensile tests are
used in selecting materials for engineering applications. Tensile properties frequently
are included in material specifications to ensure quality. Tensile properties often are
measured during development of new materials and processes, so that different
materials and processes can be compared. Since characteristic phenomena or
behavior occur at discrete engineering stress and strain levels, the basic mechanical
properties of a material are found by determining the stresses and corresponding
strains for various critical occurrences. A wealth of information about a material's
mechanical behavior can be determined by conducting a simple tensile test for
bicycle crank arm of uniform cross-section is pulled until it ruptures or fractures into
separate pieces. Finally, tensile properties often are used to predict the behavior of a
material under forms of loading other than uniaxial tension. This mechanical testing
was done by using Instron 8802 Dynamic Machine. Based on the initial geometry of
the sample, the engineering stress-strain behavior (stress-strain curve) can be easily
generated from which numerous mechanical properties, such as yield strength and
elastic modulus, can be determined. The major parameters that describe the stress-
strain curve obtained during the tension test are the tensile strength (UTS), yield
strength or yield point (σy), and elastic modulus (E). By using the X-Ray
Diffractormeter, it can determine the types of material which include in the bicycle
crank arm.
.
iii
ABSTRAK
Sifat-sifat mekanikal sesuatu bahan adalah berkaitan dengan terus untuk
tindak balas bahan tersebut apabila ia di bawah beban mekanikal. Keputusan-
keputusan ujian tegangan adalah digunakan sebagai pemilihan bahan-bahan untuk
aplikasi kejuruteraan. Ciri-ciri tegangan sering didapati dalam setiap bahan yang
terkandung bagi menentukan kualiti bahan tersebut. Ia juga kerap diukur semasa
membuat sesuatu bahan baru dan proses supaya bahan dan proses yang berbeza dapat
dibandingkan. Sejak fenomena tekanan kejuruteraan ini berlaku pada peringkat
terikan, sifat-sifat mekanikal asas sesuatu bahan di temui bagi menentukan beban dan
tegangan yang sesuai untuk pelbagai keadaan kritikal. Banyak maklumat tentang
sifat-sifat mekanikal bahan boleh ditentukan dengan menjalankan satu ujian tegangan
mudah terhadap lengan engkol basikal. Keratan rentas seragam di tarik sehingga ia
pecah atau retak kepada keping-keping berasingan. Akhir nya, ciri-ciri tegangan di
gunakan untuk meramalkan sifat sesuatu bahan. Ujian mekanik ini di lakukan
dengan menggunakan Mesin Instron 8802 Dynamic. Berdasarkan geometri awal
sampel tersebut, sifat mekanikal ketegangan tekanan (lengkung tegasan-terikan)
boleh dibina dengan mudah di mana banyak sifat-sifat mekanikal boleh di perolehi ,
seperti kekuatan alah dan modulus kenyal boleh ditentukan. Parameter utama yang
dapat di huraikan adalah lengkung tegasan-terikan yang diperolehi semasa ujian
tegangan kekuatan tegangan (UTS), kekuatan alah atau takat alah (σy),dan modulus
kenyal (E). Dengan menggunakan X-Ray Diffractormeter, ia dapat menentukan jenis
bahan yang terkandung dalam lengan engkol basikal.
iv
LIST OF CONTENTS
CHAPTER TITLE PAGES
ACKNOWLEDGEMENT i
ABSTRACT ii
LIST OF CONTENTS iv
LIST OF TABLES vi
LIST OF FIGURES vii
LIST OF SYMBOLS xi
CHAPTER 1 INTRODUCTION
1.1 Introduction 1
1.2 Objectives 5
1.3 Problem Statement 5
1.4 Scope of the Research 6
CHAPTER 2 LITERATURE REVIEW
2.1 An Overview of Metal Structure 8
2.2 Introduction to Material Testing and Mechanical
Properties of Metal Structure 14
2.3 Fatigues in Metal Structure. 14
2.4 Bicycle Crank Arm 19
v
CHAPTER 3 METHODOLOGY
3.1 Introduction 22
3.2 Material and Specimen Preparation 24
3.3 Method of Mechanical Testing 26
3.4 Method of Calculation 40
3.5 Material Analysis via X-Ray Diffractormeter 44
(XRD)
CHAPTER 4 RESULT AND DISCUSSION
4.1 Introduction 48
4.2 Result of Tensile Test 48
4.3 Result of X-Ray Diffractormeter (XRD) 59
CHAPTER 5 CONCLUSION AND RECOMMENDATION
5.1 Conclusion 60
5.2 Recommendation 62
REFERENCES 63
BIBLOGRAPHY 64
APPENDICES 67
vi
LIST OF TABLE
BIL TITLE PAGES
1.1 Gantt chart PSM 2 7
3.1 INSTRON 8802 Machine Specification 27
(Source: UTeM Laboratory)
4.1 Experimental Data for bicycle crank arm under Tensile Test 51
vii
LIST OF FIGURE
BIL TITLE PAGES
2.1 Flow for different types of material 9
(Source: Mortimer, 1975)
2.2 Typical fatigue-failure surfaces. 16
(Source: Chalmers, B. 1986)
2.3 Intrusion-extrusion model of fatigue crack initiation. 17
(Source: Roylance, D. 2001)
2. 4 Part of Bicycle 19
(www.wikipedia.com)
2.5 Flow of Mechanical Properties of Composite Material 21
(Source: Minak, (2008))
viii
3.1 Process Flow Chart of Research 23
3.2 Flow of Material Preparation 24
3.3 Part of Bicycle Crank Arm 25
(Source: www.wikipedia org)
3.4 Instron 8802 Machine 26
(Source: UTeM Laboratory)
3.5 Extensometer 28
(Source: www.tensiletest.com)
3.6 Schematic illustration showing how the sample is tested using
extensometer 29
(Source: www.composite.tensile.com )
3.7. Bicycle Crank Arm 32
(Source: UTeM Laboratory)
3.8 Measurement and marked the specimen 32
3.9 Bicycle crank arm with the pin insertion 33
ix
3.10 Position of bicycle crank arm during tensile test 33
3.11 Side view of bicycle crank arm 34
3.12 A close up view of bicycle crank 34
3.13 BLUEHILL Software 35
3.14 Example of graph to show the point of yield point,
Maximum load and load at break 42
3.15 X-Ray Diffractormeter Machine (XRD) 44
3.16 Specimen on the stage 47
3.17 Machine in operation 47
4.1 Bicycle Crank Arm before Tensile Testing 50
4.2 Bicycle Crank Arm after Tensile Testing 50
4.3 A close up view of the bicycle crank arm before and after
tensile test 50
4.4 Graph of Load, kN versus extension, mm under tensile test for
bicycle crank arm 52
x
4.5 Graph of Stress, MPa versus Strain, % under tensile test for
bicycle crank arm. 53
4.6 Graph Stress, MPa versus Strain, % under tensile test for
bicycle crank arm with other value 54
4.7 The region of stress-strain curve for bicycle crank arm under
tensile test 57
xi
LIST OF SYMBOLS
є = True Strain
σ = True Stress, Pa
S = Engineering Stress, Pa
e = Engineering Strain
P = Load, N
A = Area, m2
L = Length, m
l0 = Original Gage Length, m
lf = Final Gage Length, m
tf = Final Thickness, m
E = Modulus Elasticity
σ UTS = Ultimate Tensile Strength
1
CHAPTER 1
INTRODUCTION
1.1 Introduction
Failure of material means the progressive or sudden deterioration of their
mechanical strength because of loadings or thermal or chemical effect.All materials have
different properties that result in advantages and disadvantages. Study and understanding
of these properties is critical to the design of a mechanical system and the selection of
the correct materials for a given part. One crucial failure mode is fatigue. Fatigue is the
weakening or failure of a material resulting from prolonged stress. The strength of a
material is its ability to withstand an applied stress without failure. Yield strength refers
to the point on the engineering stress-strain curve (as opposed to true stress-strain curve)
beyond which the material begins deformation that cannot be reversed upon removal of
the loading. Ultimate strength refers to the point on the engineering stress-strain curve
corresponding to the maximum stress. The applied stress may be tensile, compressive, or
shear.
2
The selected material was choosing is crank arm for paddle bicycle.
This material is structural material which consists of combining two or more
constituents. Normally, cranks are constructed of an aluminum alloy, titanium, carbon
fiber, chromoly steel, or some less expensive steel.This crank arm is the component of
the bicycle that transfers the force exerted on the pedals to the crank set. Crank arms can
crack in a number of places. Sometimes a crack will develop between the pedal
mounting hole and the end of the arm. A crack also will develop at the crotch of the
chaining-mounting arms (spider arms) and the crank arm.
The effects of dynamic loading are probably the most important practical part of
the strength of bicycle crank arm, especially the problem of fatigue. Repeated loading
often initiates brittle cracks, which grow slowly until failure occurs. However, the term
strength of materials most often refers to various methods of calculating stresses in
structural members. The methods that can be employed to predict the response of a
structure under loading and its susceptibility to various failure modes may take into
account various properties of the materials other than material (yield or ultimate)
strength.
In basic, tensile stress is the stress state caused by an applied load that tends to
elongate the material which is bicycle crank arm in the axis of the applied load,
in other words the stress caused by pulling the material. The strength of structures
of equal cross sectional area loaded in tension is independent of cross section geometry.
Materials loaded in tension are susceptible to stress concentrations such as
material defects or abrupt changes in geometry. However, materials exhibiting
ductile behavior (metals for example) can tolerate some defects while brittle
materials (such as ceramics) can fail well below their ultimate stress.
3
Most crucial structures subjected to fatigue failures in metallic structure are a
well-known technical problem. It is of great importance for engineers the time a fatigue
crack will take to grow from initial size to the critical value in designing structures and
determining inspection intervals. Failures apparently occurred without any previous
warning.
Fatigue of materials is a well known situation whereby rupture can be caused by
a large number of stress variations at a point even though the maximum stress is less
than the proof or yield stress. The fracture is initiated by tensile stress at a macro or
microscopic flaw. Once started the edge of the crack acts as a stress raiser and thus
assists in propagation of the crack until the reduced section can no longer carry the
imposed load. While it appears that fatigue failure may occur in all materials, there are
marked differences in the incidence of fatigue.
The total fatigue life of a component can be divided into three phases which is
crack initiation, crack propagation and fracture.After a certain number of fluctuations,
the accumulated damage cause the initiation and subsequent propagation of crack in the
plastically damage regions. This process can many cases does cause the fracture of
components. The more severe the stress concentration, the shorter the time to initiate the
fatigue crack.
4
By using the INSTRON machine it is to determine the mechanical properties of
bicycle crank arm by mechanical testing which is tensile test. From this method to
measure the strength of crank arm. This is to obtain the yield strength of each specimen.
The data will be collected using software BLUEHILL. From the graph, it also can
determine the yield point, % elongation, maximum load, strength of the material, and
also can develop the stress and strain graph. In this research, the tensile test with
constant load is utilized use to discuss the affect of the structure and the strength of the
bicycle crank arm.
5
1.2 Objectives
The objectives of this research are:
a) Learn to conduct an experiment related with tensile test.
b) To analyze the effect of constant load to the bicycle crank arm structure.
c) To study and analyze the material properties of the bicycle crank arms.
1.3 Problem Statement
This research has been carried out due to the strength of material for the selected
material which is bicycle crank arm. The bicycle crank arm is one of the bicycle parts
which received high load. Analysis need to be done to figure out the maximum load
capacity that the crank arm could stand. The tensile test was conducted to measure the
strength of this material under constant load. Due to the matters set out above, this study
will analyze the strength of bicycle crank arm structure under constant loading.
6
1.4 Scope of the Research
This research comprises of the following scope:-
a) To do literature study on metal structure.
b) To carry out tensile test on bicycle crank arm.
c) To anaylize affect to the structure
d) To carry out analyze the experiment data analysis after tensile test.
e) Conclusion and suggestion for future study.
7
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8
CHAPTER 2
LITERATURE REVIEW
2.1 An Overview of Metal Structure.
Material can be anything a finished product in its own right or an unprocessed
raw material. Raw materials are first extracted or harvested from the earth and
divided into a form that can be easily transported and stored, then processed to
produce semi-finished materials. These can be input into a new cycle of production
and finishing processes to create finished materials, ready for distribution,
construction, and consumption. In chemistry materials can be divided into two which
is metals and non metals. [1]
All elements of the world, based on their physical and chemical properties,
are divided into solids, liquids, and gases. Solids can be of two types which is metals
and non metals. This grouping is done mainly on the basis of their physical
properties. Metals are usually elements in solid form that have a shiny body surface.
They are tough, and some are malleable while others are ductile. Most metals are
good conductors of heat. Most of them are also good conductors of electricity. [1]
9
2.1.1 Types of Metal
This is one of the three groups of elements in materials. Some metals and
metal alloys possess high structural strength per unit mass, making them useful
materials for carrying large loads or resisting impact damage. Metal be divided into
three which is ferrous, non ferrous and alloys. [2]
In this research the main objective is
to analyze the metal structure.
Figure 2.1: Flow for different types of material
(Source: Mortimer (1975))
Thermoplastic
Polystyrene
Acrylic
Thermo sets
Melamine
Epoxy Resin
Ferrous
Mild steel
Tool steel
Stainless steel
Cast iron
Non-Ferrous
Aluminum
Brass
Copper
lead
Alloys
Aluminium alloys
Brass
Steel
Solder
Materials
Metal Ceramic Polymer
Crystalline
ceramics Non-Crystalline
ceramics
10
2.1.1.1 Ferrous
Ferrous metals are those metals which contain iron. They may have small
amounts of other metals or other elements added, to give the required properties. All
ferrous metals are magnetic and give little resistance to corrosion. Most commonly
used ferrous metals are mild steel, high speed steel, stainless steel, high tensile steel
and cast iron. [1]
2.1.1.2 Non-Ferrous
Non ferrous metals are those metals which does not contain iron. They are
not magnetic and are usually more resistant to corrosion than ferrous metals. Most
commonly used non ferrous metals are aluminium, copper, brass, lead, tin, gilding
metal and zinc. [1]
2.1.1.3 Alloys
An alloy is a mixture of two or more metals. When a material is needed
which requires certain properties and this does not exist in a pure metal we combine
metals. Pure white aluminium is very soft and ductile. Other elements can be added
to create an aluminium alloy. This can produce a metal which is stronger than mild
steel has improved hardness and is resistant to corrosion while still remaining light in
weight. By changing the properties to form alloys, metals can be easily bent, twisted,
welded and also stretched. [1]
11
2.1.2 Metallic Properties.
Metals are usually shiny solids with high melting points and are very good
conductors of heat and electricity. They are malleable, so they can be beaten into
sheets, and ductile, which means they can be drawn into wires. Most are strong and
cannot be broken easily. Mercury, for example, is a metal that has a low boiling point
and is liquid at room temperature. [1]
In general metal have:
1. Density
2. Ductility
3. Thermal Conductivity
4. High electric
2.1.2.1 Density
The high density of most metals is due to the tightly-packed crystal lattice of
the metallic structure. The strength of metallic bonds for different metals reaches a
maximum around the centre of the transition series, as those elements have large
amounts of delocalized electrons in a metallic bond. [1]