FATIGUE ANALYSIS OF STEERING KNUCKLE

AMMER EZHAR B MOHD RAZALLI (B041110209)

This thesis is submitted in fulfillment of the requirements for the degree of

Bachelor Degree of Mechanical Engineering (Design and Innovation)

Fakulti Kejuruteraan Mekanikal

Universiti Teknikal Malaysia Melaka

JUN 2015

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SUPERVISOR DECLARATION

“I hereby declare that I have read this thesis and in my opinion this thesis is sufficient in

terms of scope and quality for the award of the degree of

Bachelor of Mechanical Engineering (Design & Innovation)”

Signature :...................................

Supervisor :...................................

Date :...................................

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DECLARATION

“I hereby declare that the work in this thesis entitle Fatigue Analysis of

Steering Knuckle

is my own except for summaries and quotations which have been duly

acknowledged.”

Signature : ...................................

Author : AMMER EZHAR B MOHD RAZALLI

Date : JUNE 2015

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Special for my mum, Mrs. Ainon binti Zakaria and my dad Mr. Mohd. Razalli bin

Abu Bakar, my oldest brother Ahmad Mourshedi bin Mohd. Razalli for everlasting

supports, friends, and also lecturer Dr. Kamarul Ariffin bin Zakaria for preparation of

this thesis.

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ACKNOWLEDGEMENTS

Praise to Allah almighty for giving me that strength and chance to complete

my thesis. The special gratitude go to my constructive supervisor, Dr. Kamarul

Ariffin bin Zakaria for providing me an excellent advice, full support and

encouragement in doing this project.

The co-operation is significantly indeed appreciated. I have taken hard work

in this project. However, it would not have been achievable without the generous

support and help of numerous individuals in particular and the faculty as well. I

would like to extend my sincere thanks to every one of them.

Apart from that, I would like to express my gratitude towards my parents &

lecturers for their kind co-operation and support which help me in finishing of this

project. Parallel thereby, my innermost gratitude to the panel for contributes in

finishing this project.

End said, I hope so that my book was full report might be preparing a few

knowledge and information and I really hope it can satisfy all groups and may be

also it serve as one valuable reference to students. Thank you.

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ABSTRACT

Generally, the steering knuckle works as a support in car which holds the

tires besides ensuring a good handling, comfort and safety driving experience. Due to

the problem occur on steering knuckle where design is not really reliable beside

excessive material used on certain places where force in not present. An investigation

and analysis is done by having the 3D CAD drawing and simulation using

SolidWorks in order to determine the fatigue life behavior under various loading

conditions. Forces that acted on the steering knuckle can either comes from the car or

the road. The forces is not static and differ with time varying. SolidWorks is used to

simulate as it has the ability to measure the fatigue life of a component by having a

simulation based design. This helps to obtain all the data needed example like the life

cycle, the reliability of the product, the identification of which the minimum stress is

present and also the critical in steering knuckle where force is exerted in a huge

amount. Perodua Myvi steering knuckle is choose in this project as it can help

increase the handling and safety in that car. The results can be used in the future for

further study.

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ABSTRAK

Secara umumnya, sendi buku stereng berfungsi sebagai sokongan di dalam

kereta yang memegang tayar selain memastikan kawalan kenderaan yang baik,

keselesaan, dan juga keselamatan sewaktu pemanduan. Oleh kerana masalah yang

datang pada sendi buku stereng di mana reka bentuknya tidak boleh di percayai

selain berlaku lebihan bahan pada tempat yang tidak dikenakan sebarang beban.

Sebuah kajian dan penyelidikan telah dijalankan bagi mengenal pasti tingkah laku

hayat lesu sendi buku stereng apabila dikenakan beban dari pelbagai nilai dengan

menggunakan simulasi dari SolidWorks. Beban yang dikenakan pada sendi buku

stereng datang sama ada dari kereta mahupun jalan raya. Beban yang dikenakan tidak

tetap dan berubah mengikut waktu. Simulasi SolidWorks digunakan untuk melihat

hayat lesu bagi setiap komponen. Ini akan membantu dalam menghasilkan data

seperti jangka hayat dan kitaran sesuatu bahan, keboleharapan, dan pengenalpastian

di mana beban yang paling kurang dan juga beban yang paling maksimum yang akan

dikenakan. Sendi buku Stereng Perodua Myvi di pilih dalam projek ini bagi

membantu meningkatkan pengendalian dan keselamatan di dalam kereta. Keputusan

yang diperoleh boleh digunakan untuk rujukan lanjut pada masa yang akan datang.

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CONTENTS

CHAPTER TITLE PAGES

SUPERVISOR DECLARATION i

DECLARATION ii

DEDICATION iii

ACKNOWLEDGEMENT iv

ABSTRACT v

ABSTRAK vi

CONTENT vii

LIST OF TABLE x

LIST OF FIGURE xi

LIST OF ABBREVIATION xiii

LIST OF APPENDICES xiv

CHAPTER I INTRODUCTION

1.1 Background study 1

1.2 Problem statement 2

1.3 Objective 2

1.4 Scope 2

CHAPTER II LITERATURE REVIEW

2.1 Introduction 4

2.2 Fatigue life 5

2.2.1 Introduction to fatigue life 5

2.2.2 Factor affecting fatigue life 6

2.3 Car suspension system 7

2.3.1 Introduction 8

2.3.2 Type of suspension system 8

2.3.2.1 Solid beam axle 8

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2.3.2.2 Swing axle suspension 9

2.3.2.3 Trailing link suspension 9

2.3.2.4 Strut suspension 10

2.3.2.5 Short/long arm suspension 11

2.4 Manufacturing process of steering knuckle 12

2.4.1 Research on material 13

2.5 Finite element analysis 14

2.5.1 Introduction to FEA 14

2.5.2 Comparison of finite element analysis

with other method 15

2.5.3 Application of FEA 16

CHAPTER III METHODOLOGY

3.1 Introduction 18

3.2 Flow chart for PSM 1 18

3.3 Finding information 19

3.4 Part selection 20

3.5 Dimensioning and geometry 21

3.6 CAD drawing 23

3.7 Flow chart for PSM 2 23

3.8 Data selection process for analysis 24

3.9 Analysis of steering knuckle 26

CHAPTER VI RESULTS AND DISCUSSION

4.1 Static and fatigue results 32

4.1.1 Results for first test 33

4.1.2 Results for second test 35

4.1.3 Results for third test 38

4.1.4 Results for fourth test 41

4.1.5 Results for fifth test 44

4.2 Discussion 47

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CHAPTER V CONCLUSION AND RECOMMENDATION

5.1 Conclusion 50

5.2 Recommendation 51

REFERENCES 53

APPENDIX A 55

APPENDIX B 58

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LIST OF TABLES

NO. TITLE PAGE

2.1 Effect of surface roughness on fatigue life 7

3.1 Force acting on knuckle 25

3.2 Material properties for grey cast iron 27

3.3 Mesh setting 27

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LIST OF FIGURES

NO. TITLE PAGE

2.1 Steering knuckle system 5

2.2 Beam axle design 8

2.3 Swing axle suspension 9

2.4 Trailing link suspension 10

2.5 MacPherson suspension system 11

2.6 SLA suspension system 12

2.7 S-N curve for the three material 13

2.8 Different type of solution 16

2.9 FEA for the engine block 17

2.10 FEA for cast ceramic 17

3.1 Flow chart for PSM 1 19

3.2 Perodua Myvi knuckle 21

3.3 3D scanner workplace 22

3.4 Images generated 22

3.5 CAD drawing for knuckle 23

3.6 Flow chart for PSM 2 24

3.7 Location of forces 26

3.8 SolidWorks Simulation for static analysis 28

3.9 Applying material to steering knuckle 29

3.10 The interface for fatigue 30

3.11 The S-N curve for grey cast iron 30

3.12 Static analysis overview 31

3.13 Fatigue analysis overview 31

4.1 Von mises stress for first test 33

4.2 Displacement for first test 34

4.3 Factor of safety for first test 34

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4.4 Damage percentage for first test 35

4.5 Life plot for first test 35

4.6 Von mises stress for second test 36

4.7 Displacement for second test 36

4.8 Factor of safety for the second test 37

4.9 Damage percentage for second test 38

4.10 Life plot for second test 38

4.11 Von mises stress for third test 39

4.12 Displacement for third test 39

4.13 Factor of safety for third test 40

4.14 Damage percentage of third test 40

4.15 Life plot for third test 41

4.16 Von mises stress for fourth test 42

4.17 Displacement for fourth test 42

4.18 Factor of safety for fourth test 43

4.19 Damage percentage for fourth test 43

4.20 Life plot for fourth test 44

4.21 Von mises stress for fifth test 44

4.22 Displacement for fifth test 45

4.23 Factor of safety for fifth test 45

4.24 Damage percentage for fifth test 46

4.25 Life plot for fifth test 46

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LIST OF ABBREVIATIONS

DVVT - Dynamic Variable Valve Timing

CAD - Computer Aided Drawing

CATIA - Computer Aided Three Dimensional Interactive Application

FEA - Finite Element Analysis

PSM - Projek Sarjana Muda

PSB - Prolonged Sip Band

SAE - Society of Automotive Engineers

CNC - Computer Numerical Control

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LIST OF APPENDICES

NO. TITLE PAGE

A1 Gantt chart for PSM 1 56

A2 Gantt chart for PSM 2 57

B1 Knuckle image 1 59

B2 Knuckle image 2 59

B3 3D scanner image inside CATIA 59

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CHAPTER 1

INTRODUCTION

1.1 BACKGROUND STUDY

Nowadays, the automobile industry becomes one of the assets for economic

development. The automobile industry has grown rapidly since the production of the

first car by Henry Ford. Cars have been improved dramatically from year to year in

term of design, safety, technology and also performance. Steering module which

related to handling is a piece of automobile suspension system which related to an

exact vehicle stability and position. Steering knuckle is one of the automotive part on

car and specifically been used in suspension system. The steering knuckle functions is

to allow the wheels to turn. On cars with conventional suspension frameworks, the

steering knuckle includes a spindle and connects the lower and upper ball joints. For

modern cars which use MacPherson strut suspension systems, the steering knuckle

connects the strut assembly to the lower ball joint.

Every vehicle will have four steering knuckle which located at the both rear

and front-side in which on the front-side control arm joined together the left side of

steering knuckle with the other side knuckle. Ball joint connect the steering knuckle

with control arm. Ball joint helps lowering the unsprung mass of the suspension

systems which would enhanced road holding. Both joint and pivot will experienced

wear or crack after being exposed with movement and mechanism under a period of

time. A lot of improvement was done by engineers and researches in order to produce

the best design of the mechanism of steering knuckle which involved in steering

system. Because of this scenario, in order to design a good and effective steering

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knuckle, the right application should be consider and the analysis on reliability of the

steering knuckle must be done. For future recommendation, this research need to

analysed and study the fatigue life for various type and structure of steering knuckle.

1.2 PROBLEM STATEMENT

In today automobile vehicle, speed and handling plays an important factor in

car construction. Because of this, steering knuckle need to have higher strength and

stiffness but also must be lighter in weight and also size. In developing power output

vehicle, the important goes to how to place the exact weight of linier and angular parts

in steering knuckle. The overall performance of steering knuckle is affected by higher

inertia force especially during driving which generated by the moving parts in the

vehicle. This inertia comes from the uneven forces that act on the steering knuckle

which can affect the lifetime and also the performance itself. Besides that, waste on

material can also occur due to lack of knowledge and study in stress distribution on

steering knuckle. Thus, an investigation on steering knuckle needs to be done In order

to prevent any failure which can affect the car performance.

1.3 OBJECTIVE

The objective for this project are:

I. To apply 3D CAD modelling and Finite Element Analysis on steering knuckle.

II. To investigate the fatigue life behaviour of steering knuckle under various

loading conditions.

1.4 SCOPES

There are several lists of scopes which will be applied thorough out the project.

The scopes are:

I. To study the effect of steering knuckle under multiaxial load.

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II. To analysed effect of acting force in steering knuckle using Finite Element

Analysis.

III. To use SolidWorks Simulation as the simulation software to analysed fatigue

failure.

IV. To identify the minimum stress area in steering knuckle.

V. To identify the critical part in steering knuckle when force is exerted.

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CHAPTER 2

LITERATURE REVIEW

2.1 INTRODUCTION

In today manufacturing industry, the detail and specifications of steering

knuckle comes in various design and shape for automobile vehicles. The configuration

incorporates the specification vehicle whether it is suit or not with the vehicle itself. In

addition, the design also emphasize the of reliability component whether the part can

oblige the force that subjected on it. Although there are plenty of steering knuckle in

the market today, the most important problem that occur in all automobile industry is

the durability and reliability of the knuckle itself. Because of this problem, the

understanding on stress and strain analysis and principle which experienced by the

steering knuckle is needed in order to overcome the problem.

Steering knuckle can be names under part of suspension system, steering

system, brake system and also as a part in wheel’s assembly. Generally, the function

of steering knuckle is to help in steering the car, brake and support the wheels. Steering

knuckle also permits the front wheel to rotate and connect rotating components to

suspension component beside helps distributing loads that comes from the road to body

evenly. Inside a suspension systems, many parts are joined together to perform work

which include steering knuckle. Parts like spring, shock absorbers, spindle, ball-joint

and control arm are examples of suspension system. Steering knuckles have different

shape for every different type of suspension system. Figure 2.1 shows the steering

knuckle system that contain several part that attach to the steering knuckle such as disc

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brake and the calliper. For Double Wishbone the knuckle is placed between upper and

lower ball joints, while for MacPherson strut the lower ball joint with the strut itself.

Figure 2.1: Steering knuckle system

(Source: Azrulhisham et. al, 2010)

2.2 FATIGUE LIFE

2.2.1 Introduction to Fatigue Life

Fatigue is the weakening of an element resulting from repetitively applied loads. It is

the gradual and localized structural damage that takes place when an element is

experiencing cyclic loading. The nominal highest stress values that result in such

damage could be a lot less than the strength of the element generally set as the ultimate

tensile stress limit or the yield stress limit. Fatigue takes place when a material is

experiencing repetitive loading and unloading. If the loads are above the particular

limit, microscopic cracks takes place to develop at the stress concentrators for instance

the surface area, prolonged slip bands ( PSBs ), and also grain interfaces (Kim & Laird,

1978). Eventually when the crack reach a critical limit, the crack will generate

suddenly, and the framework will begin fracture. The appearance of the structure will

significantly influence the fatigue life example a square holes or sharp corners will

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probably result in increased local stresses in which fatigue cracks can initiate while

circular holes and smooth transitions or fillets will therefore raise the fatigue strength

of the structure (Kim & Laird, 1978).

Fatigue life can be divided into four stages before the material begin to failure.

The first stage is the crack initiation features the beginning of growth and development

of fatigue damage that could be eliminated by an effective thermal anneal. Secondly,

slip-band crack enhancement includes the deepening of the primary crack on planes of

higher shear stress. This normally is known as stage one crack growth. Thirdly, crack

growth on planes of higher tensile stress includes growing of distinct crack in direction

normal to maximum tensile stress. Commonly known as stage two crack growth.

Ultimate ductile failure happens when the crack actually gets to adequate length as a

result the remaining cross section are unable to support the applied load.

2.2.2 Factor Affecting Fatigue Life

There are several factors which can affect the fatigue life of a material.

Geometry for a material is important as the variation in cross section of a material can

cause the stress to be focused in certain point where crack can occur. Fatigue life, along

with the characteristic during cyclic loading, differs widely for numerous materials

such as composites and polymers vary significantly from metals (eFunda, 2014).

Extreme higher or lower temperatures may also reduce fatigue strength. For several

typical types of loading, for example bending and also torsion, the maximum stress

happens at the surface area. In addition, the surface area is exposed to severe

surroundings that include corrosion, or unexpected loads like scratch and impact

(eFunda, 2014). Furthermore, studies indicate that even the failing of axial loading

generally starts at the surface area. Together with all the evidences indicating the

surface area, it is necessary to fully understand the impact of surface area roughness

and the solutions improving surface properties (eFunda, 2014). Table 2.1 shows the

effect of surface roughness experiment done by using SAE 3130 steel specimens under

stress at 655 MPa proves that a uniform and smooth surface can affect the fatigue life.

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Table 2.1: Effect of surface roughness on fatigue life

Finish Surface roughness

(micron)

Median fatigue life

(kilo-cycles)

Lathe-formed 2.67 24

Partial hand-polished 0.15 91

Hand polished 0.13 137

Ground 0.18 217

Ground and Polish 0.05 234

Superfinished 0.18 212

(Source: eFunda, 2014)

2.3 CAR SUSPENSION SYSTEM

There are many types of car suspension system. The most common one is the

MacPherson strut suspension system. It can be seen on many cars on the road.

Different types of suspension system give different experiences in term of handling.

This is because some vehicles are made for racing, daily drive and many more.

2.3.1 Introduction

Steering knuckle is one of the suspension component which helps to hold car

and tyres besides ensuring a smooth ride. The steering knuckle shape is mostly depends

on how the suspension system will work and the component that will attached to it.

Different type of suspension system can have different design of steering knuckle. The

design can also differ according to the car even though the suspension system is the

same. This ensure that the steering knuckle can fit exactly on it position. The most

common suspension system is the MacPherson strut suspension which has been used

widely in car.

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2.3.2 Type of Suspension System

The suspension system have many design in which give different driving

experience to the driver. However, all the suspension system are related to each other

and provide the same function to the vehicle.

2.3.2.1 Solid Beam Axle

Getting into chronological order, the very first mass produced front part

suspension design and style was the solid beam axle. In the same way that it looks, in

the beam axle setup the two of the front wheels are linked to each other by a solid axle

(Isaac-Lowry, 2004) as shown in figure 2.2. This design was brought over to the first

automobiles from the horse driven carriages of earlier times and worked adequate to

ensure that in the beginning no other suspension even necessary to be considered

(Isaac-Lowry, 2004). As a matter of fact the beam axle can certainly still be discovered

these days. New improvements in springs, roll bars, and shocks have kept the solid

axle convenient for certain applications. This design continue used on semi-trucks as

well as the large trucks due to the strength of the axle (Kilchermann, 2015).

Figure 2.2: Beam axle design

(Sources: Isaac-Lowry, 2004)

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2.3.2.2 Swing Axle Suspension

After designers had recognized the significant downsides of the solid axle front

suspension, they proceed forward to create an initiative independent design of front

suspension. One of those design is the swing axle suspension which is shown in figure

2.3. It is, as the term indicates, set up so that the axles pivot around a location at some

place near the center of the vehicle and enable the tires to travel up and down

throughout their specific arcs (Isaac-Lowry, 2004). This design was used by some

sports car in the 50s such as the Mercedes 300SL Gullwing. However, the problem

raised when applying this suspension is the unloading of the tires after encountering a

bump in the road (Kilchermann, 2015). Soon, designers add a universal joint between

the axle and the wheel which allowed the wheel to remain at its position whenever hit

a bump.

Figure 2.3: Swing axle suspension

(Sources: Isaac-Lowry, 2004)

2.3.2.3 Trailing Link Suspension

Another earlier type of front independent suspension is known as the trailing

link suspension. This suspension design and style uses a number of arms positioned