structural analysis of new modular and...
TRANSCRIPT
STRUCTURAL ANALYSIS OF NEW MODULAR AND LIGHTWEIGHT
AUTOMOBILE BODY STRUCTURE
ALI FAROKHI NEJAD
UNIVERSITI TEKNOLOGI MALAYSIA
iii
DEDICATION
The world of knowledge is fast developing day to day, and only persons can be
efficient who are dominant on today’s knowledge.
This thesis is dedicated to all people who endeavor to develop knowledge, and to my
beloved and kind parents who always supported me and filled my heart with nothing
but their love and finally to all peaceful people of Iran.
STRUCTURAL ANALYSIS OF NEW MODULAR AND LIGHTWEIGHT
AUTOMOBILE BODY STRUCTURE
ALI FAROKHI NEJAD
A project report submitted in partial fulfilment of the
requirements for the award of the degree of
Master of Engineering (Mechanical)
Faculty of Mechanical Engineering
Universiti Teknologi Malaysia
JUNE 2013
iv
ACKNOWLEDGMENT
In the Name of God
I would like to express my deepest gratitude to PROF. MOHD NASIR BIN
TAMIN, who always advised and encouraged me with his perfect knowledge
throughout the project. His constant support and invaluable suggestions made this
work successful. This research project would not have been possible without the help
of many people.
Special thanks to my family for the support they provided me through my
entire life.
v
ABSTRAK
Penambahbaikan keselamatan, pengurangan penggunaan tenaga dan
pengurangan pelepasan gas menjadi salah satu isu yang amat diketengahkan dalam
industri automotif beberapa tahun kebelakangan ini. Salah satu penyelesaian terbaik
ialah pelaksanaan badan kereta yang ringan seperti yang diterangkan dalam projek
ini. Reka bentuk, pelaksanaan, dan pencirian parameter badan kereta yang ringan
juga diambil kira. Selain daripada itu, struktur modular meningkatkan kadar
pembelian dan pengeluaran. Dengan mengambil kira spesifikasi reka bentuk, konsep
casis modular baru dan ringan telah diiktiraf. Di peringkat awal, simulasi model
rasuk telah digunakan. Tiga simulasi utama iaitu kekukuhan lenturan, kekukuhan
kilasan dan analisis modal telah dilaksanakan. Oleh itu, keputusan yang telah
disahkan digunakan sebagai asas untuk membuat model yang lebih kompleks. Model
ini menggunakan elemen kerangka, di mana ia boleh digunakan untuk melaksanakan
simulasi kedua yang lebih tepat dan serasi dengan simulasi keupayaan struktur
melindungi penumpang semasa pelanggaran. Dengan mencapai keputusan yang
betul, proses reka bentuk yang dicadangkan telah diluluskan. Aliran reka bentuk
meruapakan hasil akhir projek ini. Prosedur ini membawa kita untuk mereka bentuk
casis yang ringan dan modular berdasarkan piawaian SAE.
vi
ABSTRACT
Improvement of safety, reduction of energy consumption, and reduction of
emission become one of the most highlighted issues for automotive industry in recent
years. One of the most significant solutions, i.e. lightweight car body has been
described in this project. Design, implementation, and characterization of parameters
of lightweight car body are used as well. Moreover, modular structures enhanced the
rate of purchase and production. Based on design specification, the new modular and
lightweight chassis concept has been established. In the beginning of the simulation a
beam model has used. Three primary simulations, bending stiffness, torsional
stiffness, and modal analysis have implemented. Therefore, the confirmed results
used as a baseline for making a more complex model. This model used shell element,
which it can be used for performing second simulation that is more accurate and
compatible with crashworthiness simulation. To get the reason appropriate results,
proposed design process has been approved. This design flow is the last outcome of
this project. Following this procedure leads us to design a lightweight and modular
chassis based on SAE standard.
TABLE OF CONTENTS
CHAPTER TITLE PAGE
DECLARATION
DEDICATION
ACKNOWLEDGEMENTS
ABSTRAK
ABSTRACT
TABLE OF CONTENTS
LIST OF TABLES
LIST OF FIGURES
LIST OF SYMBOLS
ii
iii
iv
v
vi
vii
xi
xii
xv
1
INTRODUCTION
1.1 Back ground of Study
1.2 Research Objectives
1.3 Research Scopes
1
1
4
5
2
Literature and research background
2.1 Introductions
2.2 Lightweight Structure
2.2.1 Steel Body
2.2.2 Aluminum body
2.2.3 Polymer Composite Body
6
6
6
8
9
9
vii
2.3 Electric motor and battery
2.4 Driven front axles
2.4.1 Advantages and disadvantages of
front-wheel drive
2.4.2 Suspension systems
10
12
13
14
3
RESEARCH METHODOLOGY
3.1 Introduction
3.2 Design Characteristic
3.3 First Finite Element Model
3.3.1 FE Modeling
3.3.2 Material Properties
3.3.3 Bending Stiffness
3.3.4 Applying Load and Boundary
Condition
3.3.5 Torsion Test
3.3.6 Applying Boundary Condition
3.3.7 Modal Analysis Test
3.4 Second Finite Element Model
3.4.1 Developed Shell Model
3.4.2 Material Property
3.5 Preliminary to Crash Simulation
3.5.1 Applied Boundary Condition
3.5.2 Material Properties
3.6 Crash Worthiness Simulation
3.6.1 Frontal Crash Test
3.6.1.1 Applied Boundary
Condition
3.6.2 Rear Crash Test
3.6.2.1 Applied load and
Boundary Condition
3.6.3 Roof Crash Test
16
16
19
20
20
21
22
23
24
24
25
26
26
27
27
28
29
29
30
30
31
31
32
32
viii
3.6.3.1 Boundary Condition and
Applied Load
3.6.4 Lateral Crash Test
3.6.4.1 Boundary Condition and
Applied Load
33
33
4
RESULT AND DISCUSSION
4.1 Introduction
4.2 Conceptual Design
4.2.1 Main Module
4.2.2 Front Module
4.2.3 Rear Module
4.2.4 Roof Module
4.2.5 Suspension System
4.2.6 Final Conceptual Design
4.3 First Model Finite Element Results
4.3.1 Bending Stress
4.3.2 Evaluation of Bending Stiffness
4.3.3 Torsional Stiffness Simulation
4.3.4 Stress Distribution from Torsion
Forces
4.3.5 Torsional Stiffness Calculation
4.3.6 Modal Test with Beam Element
4.4 Second Finite Element Model
4.4.1 Developed Shell Model
4.4.2 Bending Stiffness of Shell Element
4.4.3 Torsional Stiffness of Shell Element
4.4.4 Modal Analysis of Shell Element
4.5 Preliminary to Crash Testing
4.5.1 Results and Discussion
4.6 Crash worthiness evaluation
4.6.1 Frontal Crash Simulation Result
34
34
34
35
35
36
37
37
38
39
39
40
41
41
42
43
44
44
44
46
47
48
48
50
51
ix
4.6.2 Lateral Crash Simulation
FMVSS 214 Result
4.6.3 Rear Crash Simulation FMV SS 301
Result
4.6.4 Roof Crash Simulation FMV SS 216
Result
4.7 Outcome Design Methodology
4.8 Summary
52
54
55
56
58
5
CONCLUSION
59
REFRENCES 61
x
0
LIST OF TABLE
TABLE NO. TITLE PAGE
2.1
3.1
3.2
3.3
3.4
3.5
4.1
5.1
Type of electrical motor
Design specification
Profile cross-section dimensions
Material properties
Mass distribution
Bending test boundary condition
Torsional stiffness for beam model
Comparison between target and obtained results
12
19
21
22
22
24
42
60
xi
0
LIST OF FIGURES
FIGURE NO. TITLE PAGE
1.1
1.2
1.3
2.1
2.2
2.3a
2.3b
3.1
3.2
3.3
3.4
3.5
3.6
3.7
3.8
3.9
3.10
3.11
4.1
4.2
Electrical components alignment
AC Motor/Controller Kit, 67 hp, 72/108 volt,
650 Amp
Unit Module Design-50Ah lithium-ion batteries
Passenger Car Mass Distribution
Front driven axle with double Wishbone
suspension system (AUDIA6 1997)
MC person strut
Double wishbone suspensions
Flowchart of project
The initial3D model of car chassis
Bending test boundary condition
Applied boundary condition
The shell3D model of car chassis
Applied boundary condition
Stress – strain curve –low carbon steel
NCAP test boundary condition
FMVSS301Standard test boundary condition
FMVSS216 Standard test boundary condition
FMVSS214 Standard test boundary condition
Main module and battery package
Front module and double wishbone suspension
system
3
4
4
7
13
15
15
18
20
23
25
27
28
29
30
31
32
33
35
36
xii
4.3
4.4
4.5
4.6a
4.6b
4.7
4.8
4.9
4.10
4.11
4.12
4.13
4.14
4.15
4.16
4.17
4.18
4.19
4.20
4.21
4.22
4.23
4.24
Rear module set
Roof module and related joints
Double wishbone suspension system
Final conceptual designs- side view
Final conceptual designs
Bending stresses(a) Vertical deflection (b)
Stress distributions from torsion test with Beam
element
Maximum vertical deflection from torsion test
with Beam element
Modal analysis of HSS structure
Von misses stress from bending stiffness test
The Maximum vertical deflection for bending
test by shell element
Von misses stress from torsional stiffness test
for shell element
The Maximum vertical deflection from
torsional test by shell element
The modal analysis of shell element
Stress – Strain curve –low carbon steel
Low carbon steel strain rate
The energy absorption comparison
The US NCAP frontal test in different time
steps
The maximum intrusion on foot well from
frontal test
The maximum intrusion from lateral test -
FMVSS214
The equivalent plastic strain from lateral test -
FMVSS214
The maximum intrusion from rear test –
FMVSS301
The maximum deformation from roof test –
36
37
38
38
39
40
41
42
43
45
45
46
46
47
48
49
50
51
52
53
53
54
55
xiii
4.25
4.26
FMVSS216
The Von Misses stress from roof test –
FMVSS216
Outcome design process
56
57
xiv
xv
LIST OF SYMBOLS
U1 - Horizontal displacement
U2 - Vertical displacement
UR3 - Rotational displacement around Z-axis
- Torsional stiffness
T - Torque
F - Applied load
B - Width track of car body
- Angular deflection of driver seat
- Angular deflection of passenger seat
- Average of angular deflection
V1 - Velocity along X-axis
V3 - Velocity along Z-axis
g - Passengers foot well acceleration
1
CHAPTER 1.0
INTRODUCTION
1.1 Background of Study
The automotive industry has in recent years successfully attempted to build
lighter vehicles with more energy efficient motors in order to significantly reduce
fleet consumption in accordance with legal requirements. Significantly lower fuel
consumption and CO2 emissions have been the immediate compromised of such
developments. On the other hand, demand for Electric Vehicles (EVs) has
increased during the last years, especially after the peak oil prices experienced in the
last few years. In spite of the technology that supports the EVs been well known
since many years, vehicle manufactures have presented some reluctance to
introduce it in the market [1]. However, the oil prices increase associated to the
present pressure introduced by some national and regional authorities to reduce the
environmental impacts of the transportation sector, is acting as a driver for
vehicle manufactures changing the status-quo and start a regular production of EV
models.
One of the major requirements to improve performance of a vehicle is the
efficient design of the body and the structure. The chassis frame of the car is
2
expected to provide r i g i d i t y f o r accurate handling, provide m o u n t i n g
p o i n t s for t h e suspensions, steering mechanism, gearbox, and seating for the
occupant. While fulfilling these functions, the chassis should be light enough to
reduce inertia and offer satisfactory performance. It should also be tough enough to
resist fatigue loads that are produced due to the interaction between the driver, the
engine and power transmission and the road. Reduced mass of the vehicle could be
achieved through optimized design of the chassis or frame. Since the chassis is a
critical load-bearing structure, such design is made possible with the aid of numerical
simulation for displacement and stress analysis. In this respect, finite element (FE)
anal ys i s i s an es tab l i shed versa t i l e design tool r e ad i l y avai lable for
engineers.
A direct weight reduction can also be accomplished by substituting the
structural member with lightweight materials. Two common choices for the
materials are aluminum and fiber-reinforced polymer (FRP) composites. Testing of
critical components and full scale testing of the chassis structure prototype is
indispensible both for validation of FE prediction and qualifying the parts for
structural safety. The structure stiffness must be considered in relation to the
weight to assess the efficiency of structure.
Performance of a vehicle is also evaluated in terms of ride comfort and
handling. This vehicle dynamic behavior is primarily characterized by the response
of the vehicle suspension system to road profile and distributed loading. Prediction
of dynamic responses of the system (comprises of vehicle body and masses,
suspension system and road surface profile) is commonly analyzed.
Modeling and analyzing the effect of the chassis framework for the
electric vehicle is obtain through Finite Element software ABAQUS 6.9Ef. This tool
is very important to identifying the structure failure before manufacturing and test.
This software is used efficiently for calculating structure properties, such as
static displacement and static stress, natural frequencies and mode shapes,
3
forced harmonic response amplitude. The finite element analysis is very useful tool
to identify dynamic characteristics such as natural frequencies and mode shapes. A
finite element stress analysis is carried out at the failure region to determine the
stress distribution and possible design improvement [2].However; the finite
e lement resul ts are ex tremely sensitive to mesh refinement, especially with
respect to singularities at the ends of the joint.
In this project, the electric vehicle uses an Azure Dynamics AC24LS 5.5
KW 4- pole, three-phase air-cooled AC electric motor. The corresponding digital
motor controller DMOC445 has been suggested. T h e m o t o r can spin up to a
maximum of 11,000 rpm, and which offers 47 KW (63 hp) of peak power and 92
Nm of maximum torque, working with a single-gear transmission and a 15 KWh,
50Ah lithium-ion battery. The battery consists of eight separate modules, and each
module is made up of 40 cells (in a four-in-parallel, 10-in-series configuration),
and together the assembly weighs in at 240 kg. Incidentally, weight-wise, the
Electric Vehicle has 150 kg .Weight more than a standard vehicle, with the battery
being the hefty lad.
Figure 1.1 electrical components alignment
4
Figure 1.2 AC Motor/Controller Kit, 67 hp, 72/108 volt, 650 Amp
Figure 1.3 Unit Module Design-50Ah lithium-ion batteries
1.2 Research Objectives
The objectives of this project are as follows.
To develop design methodology for modular and lightweight automobile body
structures
To design a prototype modular and lightweight body structure for an electric vehicle
Establish structural crash response on the structure
5
1.3 Research Scopes
The first scope of this project focused on material properties. In this case,
according to previous investigation the high strength steel choose as used material.
Perform FE simulation of the structure for vibration response, deformation and stress
analysis. Assess adequacy of the structure with respect to strength of materials and
structural stability. Develop methodology for designing modular and lightweight
automobile body structure, for a given set of design constraints. Establish the
crashworthiness evaluation based on SAE standard, which it focused on four most
important crash test simulation.
61
REFRENCES
[1] SUN Hongtu HP, MA Ning ,SHEN Guozhe ,LIU Bo and ZHOU
Dinglu. Application of Hot Forming High Strength Steel Parts on Car
Body in Side Impact. 2010;23.
[2] Stodolsky F, A. Vyas, et al. Life-Cycle Energy Savings Potential
from Aluminum- Intensive Vehicles. 1996.
[3] Ota. Total Life Cycle Conference & Exposition. 1995.
[4] Kragtwijk NAJLSP. The Application of Steel and Aluminum in a
New Lightweight Car Body Design. 1998.
[5] ULSAB. Data distributed by the ULSAB organization. 1997.
[6] Kelkar A. Analysis of Aluminum in Auto Body Designs and its
Strategic Implications for the Aluminum Industry. 2000.
[7] Andrew Mills MFaAC. Development of a Carbon Fibre Composite
Ultra Lightweight Vehicle Structure for the Aero-Stable Carbon Car
– Fastframes. 2002. [8] Stoll D-IJRIH. The Automotive Chassis.
2002:456.
[9] Warrendale P. Automotive Handbook, Society of Automotive
Engineers. 1995.
[10] George WBRaAR. Design, Analysis and Testing of a Formula SAE
Car Chassis.2002.
62
[11] Barari STEEaA. Methods to Determine Torsion Stiffness in an
Automotive Chassis. 2011.
[12] Shulze SRGTKaRC. Design nd Analysis of a Conceptual
Modular Aluminun spaceframe Platform. 2005.
[13] Fenton J. Handbook of Vehicle Design Analysis. 1996.