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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
«~
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.