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PSZ 19:16 (Pind. 1/97) UNlVERSITI TEKNOLOGI MALAYSIA

BORANG PENGESAHAN STATUS TESISu

JUDUL : STUDY OF DYNAMIC BERA VIOUR OF TRUCK CHASSIS

SESI PENGAJIAN 2005/2006

Saya _____ I_Z_Z_UD_D_IN_B_IN_Z_AMAN __ ....::@~B_U_J_AN_G _____ _

(HURUF BESAR)

mcngaku mcmbenarkan tcsis (PSMISarjanalGekffir falsafah)* ini disimpan di Pcrpustakaan Universiti Tcknologi Malaysia dcngan syarat-syarat kegunaan scpcrti berih.llt :

1. Tcsis adalah hak milik Univcrsiti Teknologi Malaysia. 2. Perpustakaan Univcrsiti Teknologi Malaysia dibcnarkan membuat salinan untuk tujuan pcngajian

sahaja. 3. Pcrpustakaan dibcnarkan mcmbuat salinan tcsis ini scbagai bahan pertukaran di antara institusi

pengajian tinggi. 4. **Sila tandakan (-/ )

D D D

SULIT

TERHAD

TIDAK TERHAD

(Mcngandungi maklumat yang bcrdarjah kcsclamatan atau kcpentingan Malaysia seperti yang termah.iub di dalam AKT A RAHSIA RASMI 1972)

(Mengandungi maklumat TERHAD yang tclah ditcntukan oleh organisasi/ badan di mana penyelidikan dijalankan)

(TANDATANGAN PENULIS)

Alamat Tctap:

(T ANDAT ANGAN PENYELlA )

Nama Pcnyclia:

NO.9 JALAN 24/10 A,

TAMAN BA TU MUDA,

68100 BATU CAVES, PROF. DR. ROSLAN ABD. RAHMAN

SELANGOR DARUL EHSAN

Tarikh : Tarikh :

28 DECEMBER 2005 28 DECEMBER 2005

CAT A T AN: * Potong yang tidak bcrkcnaan. * .. Jika Tcsis ini SULIT atau TERHAD, sila lampirkan surat daripada pihak bcrbJasai

organisasi berkenaan dcngan menyatakan sckali tcmpoh tesis ini perlu dikclaskan sebagai SULIT atau TERHAD.

lJ Tcsis dimaksudkan sebagai tesis bagi ljazah Doktor Fa/safah dan Sarjana sccara pcnyclidikan, alau disertasi bagi pengajian sccara kcIja kursus dan pcnyelidikan, atau Laporan Projck SaIjana Muda (PSM).

"I declare that 1 have already read this report and from the point of

my view that this report is qualify for its scope and quality to fulfiIl

the award of degree of Master of Engineering (Mechanical-Pure)"

Signature

Supervisor

Date

: PROF. DR. ROSLAN ABD RAHMAN

: 28 DECEMBER 2005

STUDY OF DYNAMIC BEHAVIOUR OF TRUCK CHASSIS

IZZUDDIN BIN ZAMAN @ BUJANG

A dissertation submitted in partial fulfillment of the

requirement for the award ofthe degree of

Master of Engineering (Mechanical-Pure)

Faculty of Mechanical Engineering

Universiti Teknologi Malaysia

DECEMBER 2005

"I hereby declared that this dissertation is the result of my own

research except those cited in reference."

Signature

Name of Author

Date

: IZZUDDIN BIN ZAMAN @ BUJANG

: 28 DECEMBER 2005

ii

Specially

To my beloved family members and girlfriend for motivation

To Prof Dr. Roslan Abdul Rahman for the guidance

To my housemate for their support

To whoever provided help and contributions

111

IV

ACKNOWLEDGEMENT

Alhamdulillah, all praise and thanks goes to Allah S.W.T who was gave the

strength and blessings for me to make it possible to complete the thesis title Study of

Dynamic Behaviour of Truck Chassis.

Special thanks to my supervisor, Prof. Dr. Roslan for the fullest support,

advices, guidance in making this project successful and not to forget to the research

officer, En. Romaizi and tedmician, En. Affendi for guiding in the experimental

conduct.

And also I would like to extend my appreciation to my family, my girlfriend;

Numlyun Shafie, housemates and friends for their endless support whenever I face

problems. Without the mentioned parties, it is impossible for me to complete this

thesis successfully.

THANK YOU

\'

ABSTRACT

Tmck chassis is a major component in a vehicle system. It inte!:-Tfates the main

component systems such as the suspension, engine, cab and trailer. Thus it often

identified for refinement in order to develop vehicles with reduced cost and weight.

Nowadays with the capabilities of advanced computer aided design and engineering

tools, the process of chassis design in the automotive industry has been significantly

refined. The application of FEA such as structural modification and optimization is

used to reduce component complexity, weight and subsequently cost. Because the

level of model complexity can be high, the opportunity for error can also be high. For

this reason, some fonn of model verification is needed before design decisions made

in the FEA environment can be implemented in production with high confidence.

This thesis project describes the application of dynamic correlation techniques for

verification of the FEA models of truck chassis. The dynamic characteristic of tmck

chassis such as the natural frequency and mode shape will be detenllined using finite

element method. Experimental measurement has been carried out to validate the

analytically derived dynamic models. Modal testing is one of the methods that apply

the experimental technique in detennining the modes of vibration. Initial results from

both analysis show that the truck chassis experienced I >1 torsion mode for I >t natural

frequency, 1 SI bending mode for 2nd natural frequency, 2nd torsion mode for 3rd

natural fi"equency and 2nd bending mode for 4th natural frequency. However there is a

small discrepancy in tenns of frequency. Thus. the model updating of tTIlck chassis

model has been carried by adjusting the selective properties such as Modulus Young

and Poisson ratio in order to get better a!:-Tfeement in the natural frequency between

both analysis. Finally. the modifications of the updated FE tTIlck chassis model has

been suggested such as by consider adding the stiffener. The purpose is to reduce the

vibration as well as to improve the strength of the tTIlck chassis.

VI

ABSTRAK

Casis trak adalah komponen penting dalam sesebuah sistem kenderaan. Ia

digunakan untuk menyokong komponen utama sistem trak seperti suspensi, enjin dan

treler. Oleh itu pembaikian sering dilakukan ke atasnya untuk mendapatkan sebuah

kenderaan yang lebih murah dan ringan. Dengan kecanggihan rekabentllk berbantu

komputer yang ada ketika ini, proses rekabentuk casis trak dalam industri automotif

dapat dipertingkatkan. Analisis unsur terhingga seperti modifikasi struktur dapat

diaplikasikan untuk mengurangkan bentuk komponen yang kompleks dan seterusnya

mengurangkan koso Oleh kerana tahap kompleks model yang tinggi, maka peluang

untuk berIahmya ralat juga adalah tinggi. Oleh sebab itu, suatu bentuk pengesahan

model diperlukan sebelum sebarang keputusan rekabentuk dibuat dalam analisis

unsur terhingga dilaksanakan dalam proses pembuatan. Projek tesis ini menerangkan

mengenai applikasi tekllik korelasi dinamik dalarn mengesahkan model unsure

terhingga bagi casis trak. Ciri-ciri getaran casis trak seperti frekuensi tabii dan bentuk

ragam akan diperolehi dan ditentukan menggunakan kaedah unsur terhingga.

Eksperimen ujikaji modal telah dijalankan untuk mengesahkan keputusan yang

diperolehi model analisis unsur terhingga. Bentuk ragam bagi casis tTak juga dapat

ditentukan melalui ujikaji modal. Hasil keputusan awal daripada eksperimen dan

simulasi komputer menunjukkan casis trak men gal ami bentlIk ragarn yang sarna.

Walaubagaimanapun terdapat sedikit perbezaan nilai frekuensi tabii bagi kedua-dua

analisis. Maka, kemaskini model unsur terhingga telah dijalankan dengan rnenukar

cirri sifat bahan seperti Modulus Young dan nisbah Poisson bagi rnendapatkan

keputusan frekllensi tabii yang lebih jitu di an tara model unsur terhingga dan model

eksperimen. Seterusnya, beberapa ubahsuaian seperti menambah penguat terhadap

casis tTak telah dilak'.1kan unhik mengurangkan kesan getaran disamping mcnguatkan

lagi kekuatan casis.

TABLE OF CONTENTS

CHAPTER TITLE

TITLE PAGE

DECLARATION

DEDICATION

ACKNO'VLEDGEMENT

ABSTRACT

ABSTRAK

CONTENTS

LIST OF TABLES

LIST OF FIGURES

LIST OF SYMBOLS

LIST OF APPENDIXES

CHAPTER 1 INTRODUCTION

1.1 Objectives

1.2 Scopes of Project

1.3 Outline

CHAPTER 2 LITERATURE REVIEWS

'.

VII

PAGE

II

III

IV

V

VI

VII

x

XI

XIII

XIV

3

3

4

5

VIII

CHAPTER 3 BACKGROUND THEORY 10

3.1 Truck Chassis 10

3.1.1 Ladder Frame Chassis 11

3.1.2 Structure of Ladder Frame Chassis 13

3.1.3 Mode of Ladder Frame Deflection 14

3.1.4 Strengthening of the Ladder Frame Chassis 14

3.2 Theory of Structural Vibration 16

3.2.1 Causes of Vibration 16

3.2.2 Reduction of Vibration 17

3.2.3 Analysis of Structural Vibration 18

3.2.4 Natural Frequency 18

3.2.5 Mode Shape 19

3.2.6 Resonance 19

3.3 Finite Element Method 20

3.3.1 Conceptual in Finite Element Analysis 21

3.3.2 Nonnal Mode Analysis 23

3.4 Modal Analysis 25

3.4. I Ftmdamentals of Modal Analysis 26

3.4.2 Theoretical of Modal Analysis 26

3.4.3 Experimental Modal Analysis 28

3.4.4 Basic Measurement System 29

3.5 Pre-Test Analysis 32

3.6 Validation, Correlation and Model Updating 32

3.6.1 Comparison of Modal Properties 33

3.6.2 The Modal Assurance Criterion 34

CHAPTER 4 METHODOLOGY 35

4.1 Finite Element Analysis 38

4.2 Pre-Test Analysis 41

4.3 Experimental Modal Analysis 42

4.3.1 List of Instrumentation 43

4.3.2 Preparation of Specimen 48

4.3.3 Experiment Sehlp 49

CHAPTERS

CHAPTER 6

REFERENCES

APPENDIX

4.4

4.5

4.6

4.3.4 E'-:periment Procedure

4.3.5 Analysis of Testing Data

Corrclation

ivIodel Updating

Stmctural Modification

RESULT AND DISCUSSION

5.1 Finite Elemcnt Analysis Results

5.1.1 Natural Frcqucncies

5.1.2 rVlode Shape

5.2 Experimcntal lvlodal Analysis Results

5.2.1 Impact Hammcr Tcsting Result

5.2.2 Shakcr Testing Rcsult

5.3 Corrclation Rcsults

5.3.1 Natural Frcqucncics Comparison

5.3.2 Mode Shapcs Comparison

5.4 iVlodcl Updating Results

5.5 StTIlctural lvlodification Rcsults

CONCLUSION AND RECOMMENDATION

6.1

6.2

6.2

Summa!)'

Conclusion

Rccommcndation for Future Rcsearch

1'-:

5·1

57

5~

58

59

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6.2

(l5

el7

()8

()9

73

7()

TABLE NO.

2.1

5.1

5.2

5.3

5.4

5.5

5.6

5.7

5.8

x

LIST OF TABLES

TITLE PAGE

Results of the modal testing and finite element analysis 7

Natural frequency result for finite element analysis 58

Comparison of modal parameter by using different modal 64

testing methods

Mode pairs with frequency difference 68

MAC-matrix value oftmck chassis before model updating 70

Comparison between natural frequencies before and 73

after updating the FE model

MAC diagonal values before and after model updating

FE model

74

Natural frequencies values before and after modification 76

Maximum displacement oftmck chassis in the first mode 77

shape

fIGURE NO.

2.1

2.2

2.3

3.1

3.2

3.3

3.4

3.5

3.6

3.7

3.8

3.9

3.10

3.11

3.12

3.13

4.1

4.2

4.3

4.4

4.5

4.6

:\1

LIST Of FIGURES

TITLE PAGE

Experimental modal analysis setup for truck chassis 6

Test setup: I vertical excitation and II horizontal excitation 7

Result of pretest analysis for center member bar

Chassis frames for commercial vehicles

The main stTIlctures of ladder-type chassis

i'dode of chassis fTame deflection

Frame flitch

K-member to stiffen the chassis fTame

The Tacoma Bridge swayed violently caused by wind

Finite element simulation lIsing T\,1SC.visual Nastran

Types of element

Meshing procedure with hexahedral element

Finite element analysis procedure

9

12

1.1

14

IS

15

17

20

21

Schematic representation basic hardware for modal testing 29

Impact hammer details 30

Piezoelectric accelerometer

Research Methodology flow-chart

Parallel ladder type fTame with bo:\ section

IsometTic view of the tnIck chassis

Tmck chassis model meshed with the tetrahedral-I 0

elements

Optimal exciter location for Y -direction

PAI-: Data analyzer

.II

.16

.17

39

-40

XI1

4.7 Laptop 45

4.8 Accelerometer with the cable --16

4.9 Equipment used in impact hammer testing --16

4.10 Charge amplifier 47

4.11 Equipment used in shaker testing 47

4.12 Excitation points 48

4.13 A typical experimental set-up for impact hammer test 49

4.14 A typical experimental set-up for shaker test 50

4.15 Modification on truck chassis by adding stiffener 55

5.1 FEA first mode shape @ 43.74 Hz 60

5.2 FEA second mode shape @ 64.81 Hz 60

5.3 FEA third mode shape @ 99.09 Hz 61

5.4 FEA fourth mode shape @ 162.34 Hz 61

5.5 Superimposed FRF for tmck chassis in log Y scale by 63

impact hammer

5.6 Curve fitting of the superimposed FRF for tmck chassis 63

by impact hammer

5.7 Experimental mode shape oftmck chassis by impact 64

hammer

5.8 Superimposed FRF for tmck chassis in log Y scale by 65

shaker

5.9 Superimposed FRF after exponential windowing process 66

5.10 Experimental mode shape oftmck chassis by shaker 66

5.11 Superimposed view of FE model and Experimental model 67

5.12 Graph comparison of natural frequency between FE and 68

EMA

5.13 MAC -matrix before updating 69

5.14 Superimposed view of the first paired mode shape 70

5.15 Superimposed view of the second paired mode shape 71

5.16 Superimposed view of the third paired mode shape 71

5.17 Superimposed view of the fourth paired mode shape 72

5.18 Chassis E changes as a result of updating 75

5.19 Chassis p changes as a result of updating 75

5.20 FE results after modification oftnIck chassis 77

f

T

F

k

x

m

x

c

x

OJ

[K]

[M]

{ii}

{ll } {¢ }

A,

{f}

E

P u

LIST OF SYMBOLS

Natural fTequency

Period ofhannonic motion

Force

Spring stiffTIess

Displacement

Mass

Acceleration

Damping coefficient

Velocity

Natural frequency

Time

Stiffness matrix to represent elastic properties of a model

Mass matrix to represent inertial properties of a model

Acceleration matrix

Displacement matrix

Eigenvector or mode shape

Eigenvalues (the natural or characteristic fTcqucncy)

Vector of applied forces

Young"s lvlodulus

ivlass density

Poisson ratio

:\111

:\1 \'

LIST OF APPENDIXES

APPENDIX TITLE PAGE

A Experiment set-up 85

B Engineering drawing 87

C Result of Experimental Modal Analysis 94

0 Result of Nonnal !vlodes 97

E Ghant Chart 102

F Tmck catalogue 104

CHAPTERl

INTRODUCTION

Chassis used in off-road vehicles have almost the same appearance since the

models developed in 20 or 30 years ago. This indicates that the evolution of these

structures is still slow and stable along the years [1]. Therefore many researchers in

automotive industry have taken this opportunity to be involved in the chassis

manufacturing technology and development. Malaysia had invested large amount of

money in automotive industry. However, the automotive industry in Malaysia

especially in truck manufacturing is still in the development phase and much relying

on foreign technology.

Nowadays, the current trend in truck design involves the reduction of costs

and increase in transportation efficiency. The pursuit of both these objectives results

in lighter truck, which uses less material and carries less dead weight. At the same

time, the comfort oftlle driver cannot be neglected as the driver has to operate safely

and comfortably for many hours. Chassis is one of the parts in the truck that is

strongly influenced by these guidelines of weight and cost reduction [2]. The

consequence of a lighter chassis is a vehicle that has structural resonance within the

range of typical rigid body vibrations of the truck subsystems. On the other hand, the

vibration also can be fonned due to dynamic forces induced by the road

irregularities, engine, transmission and more. Thus under these various dynamic

excitation, the chassis will tend to vibrate and can lead to ride discomfort, ride safety

problems, road holding problems and also to cargo damage or destnlction [3].

However, it is worried most if one of the excitation forces coincides with the natural

frequencies of tnlck chassis. It can cause resonance to occur where the chassis will

undergo dangerously large oscillation. This can result in excessive deflection and

failure.

To solve this problem, the study of dynamic characteristics of tmck chassis is

essential by detennining the natural fTequency and mode shape of the system. The

tmck chassis can be avoided from vibrating at dangerous level by making sure that

the excitation forces frequency does not coincide \,~th the natural frequency of tnlck

chassis. Besides that by understanding the dynamic charactelistics; mode shape of

tnlck chassis, the suitable mounting location of the components such as engine,

suspension, cab and transmission can be detennined. Modification of chassis

stnlcture has also become one of the important stages in a truck chassis development.

This can be done by modifying the dynamic behavior of the chassis which result in

enhancing the stmchlre fatigue characteristic, reduce the vibration effect and improve

the strength of tnlck chassis. Adding stiffener is the most common method used in

stnlctural modification [4].

3

1.1 Objective

The objectives of this project are:

I. To detennine the natural frequency and mode shape of the tmck chassis by

using finite element method and modal analysis.

1I. To improve the dynamic behavior ofthe truck chassis.

1.2 Scope of Project

The scopes of this project are:

I. Literature review and critical analysis of dynamic characteristic of tmck

chassis.

1I. Analysis of 1 tonne loading truck chassis

iii. Simulation work by using finite element method.

IV. Experimental work by modal analysis.

v. Correlation of finite element analysis and modal analysis.

VI. Modal updating analysis on FE model by adjusts the selective properties.

VII. Proper modification and improvement of truck chassis to suit desired

requirement.

4

1.3 Outline

Chapter 2 discusses on the Iiterahlre study of tmck chassis based on recent

papers and journals that have been carried out lately. The entire literature searches

are basically related to the recent stmctural dynamic analysis, modal analysis testing,

finite element analysis and model updating on the truck chassis.

The theory and mechanics of vibration as they are used in this Stlldy are

explained in Chapter 3. An explanation of tmck chassis such as the ladder frame

chassis, fundamentals of finite element methods and modal analysis testing are also

discussed.

Chapter 4 provides an outline of the tmck chassis setup at the Stmctural

Dynamic Laboratory for vibration testing. It includes the chassis installation for fTee­

free vibration test and the data acquisition system for modal testing. Meanwhile the

steps and work procedure for finite element analysis are also been clarified JI1

Chapter 4. The correlation and updating process are also defined in this chapter.

Chapter 5 discusses on the experimental results and the analytical predictions

by finite element analysis of the tmck chassis vibration. All the discussion related to

this Shldy such as the correlation analysis, model updating and the stTuctural

modification of truck chassis are also discussed in this part.

Finally, Chapter 6 summarizes and concludes the results of the study and

provides recommendations for fuhlre research.

CHAPTER 2

LITERATURE REVIEW

An extensive literature search in the area of vehicle vibration prediction

especially for truck and method of testing was conducted. It has been done to get

some idea for the project. The databases such as Society Automotive Engineers

(SAE) Technical Papers and Science Direct, which are a leading source literature for

automotive, vibration and engineering research, were used to complete the search.

Mostly the literature reviews that have been found are based on a previous

researcher's technical papers from Society Automotive Engineers. The literature

search is basically related on recent structural dynamic analysis, modal analysis

testing, finite element analysis and model updating on the truck chassis. In tllis

section, there are 5 papers tllat related to the studies will be discussed.

RRossi Pinto FilllO et al. [1] have carried out a research for a commercial

off-road vehicle chassis. The work consists in obtaining an optimized chassis design

for an off-road vehicle with tlle appropriate dynamic and structural behavior, taking

into account the aspects relative to the economical viability of an initial small scale

production. In tlus paper, tlle authors have divided the work into tlrree main parts,

first are the experimental test done to the chassis to find the torsional stiffuess and

modal parameters, second are tlle validation of tlle finite element model of the

chassis using experimental data, and third are tlle optimization of tlle chassis based

on the validated finite element model to increase in the structural stiffuess but with

maintenance of the center of gravity of height and total weight of the structure.

Because of the scope of the thesis, only the modal analysis. the validation of finite

element model and the optimization of the chassis will be discussed. In a modal

testing analysis, the real structure of chassis was sustained by strings to repre nt a

free-free boundary condition. In this experimental test, 6 accelerometers, an inertial

hammer, 7 signal conditioners and an acquisition board attach to a Laptop was used

for data acquisition. This experimental setup is shown in Figure 2.1.

Figure 2.1: Experimental modal analysis setup for truck chassis [I]

While in the fmite element analysis, the chassis model was built using the

ANSYS program. A combination of several elements such as a quadrilateral shell

elements and triangular shell element were used in the meshing analysis. The re ults

of the modal testing and finite element analysis are shown in Table 2.1. The natural

frequencies for the first 7 modes are shown in this table. The authors also found that

the first mode of the chassis is torsion, the second mode is bending in y axis and the

third mode is bending in z axis. Besides that, the author had discovered the optimized

structure presented increase in torsional stiffness, increase of height of center gra ity

and increase in total mass.