thermal stress analysis on heavy truck disc brake rotor...

THERMAL STRESS ANALYSIS ON HEAVY TRUCK DISC BRAKE ROTOR

BY USING FINITE ELEMENT ANALYSIS (ABAQUS)

RUSELI KIEN

This report is written as a partial fulfillment of terms in achieving the award for

Bachelor of Mechanical Engineering (Thermal-Fluid)

Faculty of Mechanical Engineering

Universiti Teknikal Malaysia Melaka

MAY 2009

ii

‘I approve that i have read this thesis thoroughly and in my opinion, this thesis is has

fulfilled the criteria covering all the aspects of scope and quality and satisfied to be

Awarded for Bachelor of Mechanical Engineering (Thermal-Fluid).’

Signature :……………………

Supervisor I :……………………

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

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“I hereby admit that this report is all written by me except for the summary and the

article which I have stated the source for each of them.”

Signature :…………………...

Writer : Ruseli Kien

Date :……………………

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ACKNOWLEDGEMENTS

First of all, the author would like thank to God for the blessing given that allow

the author being able to finish this report within the time. The author wishes to

express his sincere gratitude to Mr Mohd.Zaid Akop for contributing valuable time,

advice and assistance. Very special thanks are due to the author’s parents for their

understanding, patience and encouragement throughout the course of this study. The

author also would like to thanks to Dr. Abdul Rahim Abu Bakar from Universiti

Teknologi Malaysia and Prof Andrew Day from Bradford University for sharing the

valuable knowledge about finite element analysis technique and the behavior of the

thermal stress analysis on the brake disc rotor. Special thanks to staff of Webb Brake

disc USA manufacturer especially to Mr. Jeremy and also Mr. Charles for the

cooperation given. Thank you to all members of the BCMT student for the

interesting time and the support given. Finally to Mrs. Cornelia, without her never

ending belief and encouragement, this research would never have been completed.

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ABSTRACT

Braking system is the most important component in all kinds of vehicles.

While braking, most of the kinetic energy is converted into thermal energy and

increase the disc temperature. Problems such as premature wear of brake pads and

thermal cracking of brake discs are attributed to high temperatures. Consequently

controlling the temperature profiles and thermal stresses are critical to proper

functioning of the braking system. This research project consists of thermal stress

analysis on heavy truck brake disc rotor for steady state & transient analysis. The

variation of thickness will cause the thermal stress occur during the friction between

the pad and disc. The dissipated heat transfer during the periodic braking via

conduction, convection and radiation which also affected the thermal distribution of

rotor. To determine the thermal stress analysis of brake disc rotor, transient finite

element techniques are used to characterize the temperature fields of the ventilated

rotor with appropriate thermal boundary conditions. In order to get the stable and

accurate result of element size, time step selection is very important and all these

aspects are discussed in this paper. The findings of this research provide a useful

design tool and improve the brake performance of disc brake system.

vi

ABSTRAK

Sistem pembrekan adalah merupakan komponen terpenting dalam keenderaan.

Sewaktu membrek, hampir kesemua tenaga kinetik ditukarkan kepada tenaga haba

dan meningkatkan suhu cakera brek. Masalah yang sering berlaku adalah seperti

kesan pramatang pelapik brek dan juga tegasan terma yang berlebihan dalam cakera

brek adalah berpunca daripada kesan pemindahan suhu tinggi. Oleh itu adalah

penting untuk mengawal suhu dan kesan tegasan terma untuk sistem pembrekan

berfungsi dengan baik. Projek penyelidikan ini merupakan projek yang melibatkan

analisis tegasan terma ke atas cakera brek bagi kenderaan berat untuk keadaan

mantap serta keadaan berubah dengan masa. Ketebalan yang berbeza-beza akan

menyebabkan proses tegasan haba berlaku semasa geseran di antara pad brek dan

cakera disk. Pemindahan haba semasa pembrekan berkala dipindahkan melalui

konduksi, perolakan dan juga sinaran menjejaskan taburan terma bagi cakera disk.

Untuk menentukan terma analisis tegasan bagi cakera brek, teknik unsur terhingga

digunakan untuk menunjukkan bagaimana tegasan terma itu dipindahkan ke seluruh

permukaan cakera brek kesan daripada peningkatan suhu dengan menggunakan

syarat-syarat sempadan yang sesuai. Untuk mendapatkan hasil keputusan yang tepat,

pemilihan langkah-langkah yang sesuai adalah penting dan segala aspek

mengenainya dibincangkan dalam kajian ini. Berdasarkan hasil daripada penemuan

penyelidikan ini, ianya boleh digunakan sebagai rujukan awal dalam proses

rekabentuk cakera brek yang berongga.

vii

TABLE OF CONTENTS

CHAPTER ITEMS PAGE

TITLE i

DECLARATION iii

ACKNOWLEDGEMENTS iv

ABSTRACT v

ABSTRAK vi

TABLE OF CONTENTS vii

LIST OF FIGURES xi

LIST OF TABLES xiv

NOMENCLATURE xv

CHAPTER I INTRODUCTON

1.1 Background of Research 1

1.2 Objectives of The Study 2

1.3 Scope 2

1.4 Problem of Statement 3

1.5 PSM Structure 4

CHAPTER II LITERATURE REVIEW

2.1 Overview 5

2.2 Introduction of Braking System 6

2.3 History 8

2.4 Air Disc Brake

2.4.1 Introduction 9

2.4.2 How the Brake Functions 10

viii

CHAPTER ITEMS PAGE

2.4.3 Disc Brakes Component 11

2.4.4 Brake Disc Advantage and Disadvantage 18

2.5 Brake Disc Rotor


2.5.2 Ventilated Brake Discs 20

2.6 Heat Transfer Finite Element Theory


2.6.2 Conduction 22

2.6.3 Convection 24

2.6.4 Radiation 25

2.6.5 Steady-State Analysis 26

2.6.6 Transient Analysis 27

2.6.7 Accuracy of Properties and Boundary Conditions 28

2.7 Finite Element Analysis


2.7.2 ABAQUS Software 30

2.7.3 Application 31

2.7.4 Finite Element Modeling 31

2.7.5 Finite Element Analysis Stage 32

2.8 Review of Previous Research 33

CHAPTER III LOAD ANALYSIS

3.1 Overview 34

3.2 Assumption in Heat Input Calculation 36

3.3 Heavy Truck Model


3.3.2 Dimension 38

3.3.3 Brake Disc Rotor 39

3.3.4 Disc Material 40

3.4 Heat Flux Analysis


3.4.2 Braking Energy and Braking Power 42

ix

CHAPTER ITEMS PAGE

3.4.3 Heat Flux per Unit Area 46

3.5 Boundary Condition


3.5.2 Heat Transfer C. (Braking Surface) 48

3.5.3 Heat Transfer C. (U. Inner Ring Surface) 51

3.5.4 Heat Transfer C. (L. Inner Ring Surface) 53

3.5.5 Heat Transfer C. (U. Outer Ring Surface) 55

3.5.6 Heat Transfer C. (Outer Ring Surface) 57

3.5.7 Heat Transfer C. (Inner Vane Passage) 59

CHAPTER IV FINITE ELEMENT MODELLING

4.1 Overview 64

4.2 ABAQUS Software


4.2.2 Preprocessing (ABAQUS/CAE) 65

4.2.3 Simulation (ABAQUS/CAE) 66

4.2.4 Post processing (ABAQUS/CAE) 66

4.3 Step Analysis

4.3.1 Importing File from IGES 66

4.3.2 Creating a Material Property 68

4.3.3 Model Assembly 69

4.3.4 Define the Step Analysis 70

4.3.5 Interaction 71

4.3.6 Load and Boundary Condition 72

4.3.7 Meshing 73

4.3.8 Job Manager 74

4.3.9 Result of the Simulation 75

CHAPTER V RESULT AND DISCUSSION

5.1 Overview 76

5.2 Steady State Condition

5.2.1 Temperature & Thermal Stress Analysis 77

x

CHAPTER ITEMS PAGE

5.3 Transient Condition

5.3.1 Temperature & Thermal Stress Analysis 78

5.4 Thermal Stress Discussion 84

5.5 Brake Disc Deformation 88

5.6 Validation of Results


5.6.2 Analytical Method 90

CHAPTER IV CONCLUSION

6.1 Overview 94

6.2 Recommendation 95

REFERENCES 96

APPENDIXS 99

xi

LIST OF FIGURES

No. TITLES PAGES

2.1 Stopping distances from 60 mph on dry road 7

(Source, NHTSA, 1988)

2.2 Early model braking system 8

(Source: www.fuso.com.au)

2.3 Truck air brake disc 9

(Source: Arvin Meritor. 2002)

2.4 Air disc brake cutaway view 10

(Source: Arvin Meritor. 2002)

2.5 Components of a disc brake system 11

(Source: Okon D. Anwana, 2002)

2.6 Caliper body 12

(Source: Arvin Meritor, 2002)

2.7 Caliper side view 12


2.8 Fixed caliper 13


2.9 Caliper assembly 14


2.10 Seal 15


2.11 Seal assembly 15


2.12 Protective part 16

xii

No. TITLES PAGES

2.13 Section of a pad 17

2.14 The type of rotor 19

2.15 Ventilated brake disc 20

2.16 Heat dissipation from disc rotor 21

(Source: Limpert, 1999)

2.17 The diagram of conduction through plane wall 22

(Source: Phong Van, 2003)

2.18 Radiative heat transfer coefficient versus rotor temperature 26

(Source: D. A. Johnson, 2003)

2.19 ABAQUS/CAE, ABAQUS/Viewer and the analysis module 30

(Source: Arul M Britto, 2005)

3.1 An overview of the process in the rotor thermal analysis 36

3.2 Volvo Tractor 37

3.3 Model heavy duty truck 37

(Source: www.fuso.com.au)

3.4 Disc rotors 39

3.5 Pearlitic grey cast iron and ferrite grey cast iron 40

3.6 The first cycle of the braking cycle 41

3.7 Heat flux generated 42

3.8 Maximum brake powers 45

(Source: Limpert, 1999)

3.9 Cooling process at the braking surface 49

3.10 Cooling process at the upper inner ring surface 51

3.11 Cooling process at the lower inner ring surface 53

3.12 Cooling process at the upper outer ring surface 55

3.13 Cooling process at the outer ring surface 57

3.14 Cooling process at the inner vane passage surface 59

3.15 Inner vane passage surface 60

3.16 Air flow at inner vane passage 61

xiii

No. TITLES PAGES

4.1 Step analyses in ABAQUS 65

4.2 Importing file from Solidworks 67

4.3 Material property 68

4.4 Model assembly 69

4.5 Step analysis 70

4.6 Interaction module 71

4.7 Define loads 72

4.8 Define boundary condition 73

4.9 Meshing 74

4.10 Job manager 75

5.1 Temperature analysis steady state condition 77

5.2 Thermal stress analysis steady state condition 77

5.3 Temperature analysis at 2th

cycle (heating) 78


cycle (cooling) 79

5.5 Thermal stress analysis at 2th

cycle (heating) 79


cycle (cooling) 80


cycle (heating) 81


cycle (cooling) 81


cycle (heating) 82


cycle (cooling) 82


cycle (heating) 83


cycle (cooling) 83


cycle (heating) 84


cycle (cooling) 84

5.15 Temperature rise at the inboard and outboard surface 85

5.16 Misses stress at the inboard and outboard surface 85

5.17 The maximum Von Misses stress 87

5.18 The hot spot at the braking surface 88

5.19 Magnitude displacement 90

5.20 Temperature rise of brake disc rotor 93

xiv

LIST OF TABLES

No. TITLES PAGES

3.1 Volvo truck brake disc rotor dimension 21

5.1Temperature of brake disc surface 92

xv

NOMENCLATURE

sA = Surface Area

fA = Projected Frontal Area

CFD = Computational Fluid Dynamics

D = Aerodynamic Drag Force (N)

oD = Outer Diameter of Rotor

iD = Inner Diameter of Rotor

bE = Braking Energy

FD = Finite Difference

FE = Finite Element

FFT = Fast Fourier Transform

h = Convection Heat Transfer Co-efficient

zH = Hertz

l = Characteristic Length

q = Mass Flowrate

N = Revolution per Minute

air = Density of Air

or = Outer Radius of Rotor

sT = Surface Temperature

= Velocity

ave = Average Velocity

= Angular Velocityܿ = Specific heat kJ/kgK݄ோ = Convective heat transfer coefficient (W/m2k)

xvi

Nu = Nusselt number

Q = Thermal energy

Qcond = Conduction heat flow rate kW

Qrad = Radiation heat flow, kW

VA = Vane angle

Vnu = Vane offset糠 = Thermal diffusivity, m2/s降 = Angular velocity, rad/s購 = Stefan Boltzmann constant, W/m

2K

4綱 = Emissivity航 = Friction coefficient

1

CHAPTER I

INTRODUCTION

1.0 Background of Research

The disc brake is a device for slowing or stopping the rotation of a wheel. The

brake caliper is forced mechanically or pneumatically against both sides of the disc

of the heavy truck to stop the vehicle. The friction between the pads with the disc

rotor of the heavy truck leads to heat flux generation which can be significantly can

decrease the braking performance. The rate of heat generation is due to the kinetic

energy and potential energy were transferred into thermal energy during the braking

process are depends on the vehicles mass, velocity, and rate of deceleration. The

large amount of heat is created and has to be absorbed by brake components in a very

short space of time and the allowable temperatures of the brake and surrounding

components have a limited amount of thermal energy a brake can be stored. The

absorbed heat must be effectively dissipated through the ventilated disc rotor to

achieve satisfactory performance of the braking system. The cooling process of heat

transfer is dissipated through convection, conduction and radiation. The finite

element analysis is used to predict the thermal distribution inside the rotor in steady

state and transient condition.

http://en.wikipedia.org/wiki/Wheel

http://en.wikipedia.org/wiki/Pneumatics

2

1.2 Objectives of the Study

The research focuses on thermal stress analysis on the solid state condition and

during the transient condition to show the temperature distribution of disc brake of

the heavy truck. The main objectives of this study are:

To understand the working principles, components, standard & theories

through a literature study.

To understand the working principle of FEA software (ABAQUS).

To analyze the thermal distribution on brake disc when the friction

occur at the each cycle of the repeating braking and also the effect of

the thermal distribution.

To clearly justify the result of the thermal stress analysis of the front brake

disc rotor.

1.3 Scope

The scopes of the thermal stress analysis on brake disc rotors are:

Literature review on the working principles, components, standard and

theories.

Construction of 2D & 3D model of disc brake rotor

FE model (Meshing of geometry model)

Finite element analysis on steady state & transient analysis which shows

the temperature distribution of disc brake rotor

Final justification of the thermal stress analysis on the heavy truck

brake disc rotor.

3

1.4 Problems of Statement

The kinetic energy of a vehicle increases with the square of its velocity which

makes it possible to stop a vehicle within a shorter period of time. This leads to very

high power rates transmitted to the rotor disk. The kinetic energy of the heavy truck

is transformed into heat energy which is can’t dissipate fast enough into the air

stream from the brake to the ventilated brake disc rotor.

There are two main problem of brake disc related with thermal such as

excessive heat and severe thermal distortion. For heavy truck its required high power

rates transmitted to brake pad to stop the rotor disc within shorter period of time. The

friction between the brake pad with brake disc rotor produce the non-uniform

excessive heat along the rotor surface due the rotor is rotating. The different

temperatures in shorter period of time create thermal stress which caused by the

changing of disc thickness. The high energy required to be handled by the rotor can

lead to disk surface failure. In particular, it is recognized that repeated severe brake

application under high speed driving may lead to thermal cracking of brake rotors

due to inelastic cyclic strain accumulation .The rate of heat dissipated out from the

rotor is low due to the short braking period as the conduction and convection are not

large enough to take it all away. Thus the surface temperature rises much more

rapidly than the main body of the disk and undergoes higher expansion. If the

temperature gradient is steep enough, compressive plastic strain are generated at the

surface and while cooling afterwards tensile residual stresses are induced which may

be great enough to cause surface failure in one cycle . Thermal judder occurs as a

result of non-uniform contact cycles between the pad and the disk brake rotor, which

is primarily an effect of the localized Thermo-Elastic Instabilities (TEI) at the disk

brake rotor surface. Localized TEI act at the friction ring surface generating

intermittent hot bands around the rubbing path which may in turn leads to the

development of hot spots, (D.Eggleston, 2000)

4

1.5 PSM Structure

The structure of this research is as follows:

Chapters 1 introduce the objective of the research, scope of the work and also include

the problem of statement.

Chapter 2 provides basic information on the selected model heavy truck, the working

component of brake disc, theory of the heat transfer inside the rotor, the information

about the finite element analysis and includes a detailed review of the relevant

background literature.

Chapter 3 describes the heat flux analysis of the heavy truck and also the calculation

of the cooling process at the brake disc surface due to the force convection.

Chapter 4 provides the step used of the finite element modeling by using ABAQUS

software.

Chapter 5 includes the result thermal stress analysis of the both condition at the each

cycle of the repeated braking and followed by the validation of the result by using the

analytical solution method.

Chapter 6 covers the conclusion based on the result of the experiment and the

suggested recommendation of the research in the future.

5

CHAPTER II

LITERATURE REVIEW

2.1 Overview

In this chapter, the working principle of the typical components of commercial

vehicle (heavy truck) brake disc rotor are explained and the heat flux generated due

to the friction are absorbed by the brake disc rotor itself and the heat dissipated

through the atmosphere via convection, conduction and radiation to the nearby

component. The increasing temperature due to frictional heat generation cause axial

and radial deformation of the rotor along with pad expansion. The resulting change

in shape affects the contact between the rotor and pad surface area and thus will

influence the load distribution at the friction interface that can lead to the disc surface

failure. The discussion concepts of the heat transfer are explained including the

boundary condition, thermal transient and also modeling consideration. The finite

element analysis (ABAQUS software) is being used for detailed visualization of

where structures bend or twist and indicates the distribution of stresses inside the

rotor surface. The history of brake disc development and the typical component of air

disc brake will be discussed at the next section.

6

2.2 Introduction of Braking System

The most important system in any commercial vehicle and critical for its safe

operation is a brake system. The brake system are used ensure the safety control of a

vehicle during the braking and enable the vehicle to a smooth stop within the shortest

possible distance under the emergency situations, normal operation and also parking

brakes.

The efficient brake system on any type of vehicle are must be able to provide

the necessary braking torque to the wheel to control the vehicle while dissipate the

heat flux generated due to the friction between the brake pad with the brake disc

rotor. The braking action is usually achieved by mounting the brake on the wheel as

known as the foundation brakes that apply a braking torque directly on the wheel.

The another type of braking actions is by using the brakes on the transmission shaft

of the vehicle that generates higher braking force at the wheel compare to the

foundation brakes but can only provide low braking torque at low vehicle speed,

(T.K. Garrett, 2001).

This research focused on the air brake disc system which widely used in

commercial vehicle such as trucks, tractor-trailer combination and buses. Truck

brakes rely on friction and brake lining material to provide sufficient torque to slow

and stop a vehicle weighing as much as 80,000 pounds within a reasonable distance.

Repeated or continuous brake use (such as on long or steep hills) generates high

temperatures that cause the brake linings to lose effectiveness either from fading or

disintegration. Thus, on a 60 percent grade, an 80,000-pound tractor-trailer requires

167 times more braking power than a 3,000-pound passenger car, even though the

tractor-trailer weighs only 27 times more sources from National Highway Traffic

Safety Administration of USA.

7

Figure 2.1 Stopping distances of heavy air braked vehicles from 60 mph on dry road

(Source: NHTSA, 1988)

The commercial vehicle brakes are designed and balanced for fully loaded

condition and this result excessive heat generated. The braking performance of

commercial vehicle is governed by the Federal Motor Carrier Safety Regulation

(FMCSR) Part 393. These regulations specify the stopping distance, deceleration and

brake force that should be achieved during stopping.

8

2.3 History

The early years of automotive development were an interesting time for the

designing engineers where the period of innovation without established practice and

virtually all ideas were new ones and worth trying. The development of the braking

system is quite rapidly, however the design of many components stabilized in

concept and so it was with brakes; the majority of vehicles soon adopted drum. The

need for an efficient braking system became more relevant as the speed of the cars

increased especially for emergency stop purpose.

Figure 2.2 Early model braking system

The early disc brakes design were patented by Frederick Willian Lanchester at

Birmingham factory in 1902 but still not as effective at braking as the contemporary

drum brakes of that time and was soon forgotten. Another important development

occurred in the 1920’s when drum brakes were used at all four wheels instead of a

single brake to halt only the back axle and wheels such as on the Ford model T. The

disc brake was again utilized during World War II in the landing gear of aircraft. The

developments in both England and America were very much influence by the results

of the racing cars using disc brakes and resulted in the adoption of this system to the

mass produced family cars during the 1960s.

thermal stress analysis on heavy truck disc brake rotor...

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