The Study Of Cylindrical Tube Under Quasi-Static Loading.
“I hereby declared that I have read through this report and found that it has comply
the partial fulfillment for awarding the degree of Bachelor of Mechanical Engineering
(Material and Structure)”
Signature
: ……………………………………
Supervisor’s ζame
: Prof. Dr. Md. Radzai Bin Said
Date
: 18th MAY 2009
THE STUDY OF CYLINDRICAL TUBE UNDER QUASI-STATIC LOADING
ILLY SALWANA BINTI ABD RAZAK
UNIVERSITI TEKNIKAL MALAYSIA MELAKA
ii
“I hereby declared this report is mine except summary and each quotation that I have
mentioned the resources”
Signature:…………………………
Author’s ζame: Illy Salwana Abd Razak
Date: 18th May 2009
iii
To my beloved father and mother
iv
ACKNOWLEDGEMENT
The author would like to express gratitude to her supervisor, Prof. Dr. Md.
Radzai Said, for his help, time and encouragement during the course of this project.
The author takes this opportunity to also thank the Faculty of Mechanical
Engineering’s laboratory management for their cooperation especially to the technicians
during performing experimental works at the laboratory.
Special thanks are due to all who has involved in helping to finish this project
v
ABSTRACT
Vehicle’s crash caused a lot of trouble and undesired things. Though, the effect
of the crash can be minimized or prevented as stated as crashworthiness. The
crashworthiness of a vehicle depends on its material and structural. Thus, impact energy
absorption devices is introduced and used in all vehicles structural nowadays. The
impact energy absorption devices are consumable mechanical structure which useable
and useful in any collisions. Thus cylindrical tube is being studied on axially and
laterally impact. An investigation into energy absorption requires an understanding of
materials engineering and structural mechanics. Performance of energy absorbers is
determined from various parameters. From material properties, the common parameters
those are important were determined by hardness test and compression test.
Experimental works and theoretical analysis using theorems from previous studies are
discussed and compared. Axially loading gave better result in energy absorbing
compared to laterally loading.
vi
ABSTRAK
Perlanggaran antara kenderaan menyebabkan pelbagai masalah dan perkaraperkara yang tidak diingini. Bagaimanapun, kesan daripada perlanggaran tersebut boleh
diatasi ataupun dielakkan seperti mana yang disebut sebagai ketahanan kepada kesan
perlanggaran. Ketahanan kepada kesan perlanggaran bergantung kepada bahan yang
digunakan dan struktur kenderaan tersebut. Oleh sebab itu alat penyerapan tenaga pasak
diperkenalkan dan digunakan dalam struktur semua jenis pada hari ini. Alat penyerapan
tenaga pasak adalah bahagian struktur mekanikal yang boleh diganti yang mana boleh
digunakan dan sangat berguna ketika apa jua perlanggaran. Oleh sebab itu tiub silinder
diperkenalkan sebagai satu kajian baru yang mana memfokuskan tentang cara mencipta
dan merekabentuk bahan dan struktur yang boleh menyerap tenaga kinetic secara
berkesan dan boleh dijangka. Kajian tentang penyerapan tenaga memerlukan
pemahaman tentang kejuruteraan bahan dan mekanik struktur. Pelaksanaan alat
penyerap ditentukan oleh bebarapa terma. Dua jenis ujikaji dijalankan bagi menentukan
kebolehan tiub silinder dalam menyerap tenaga. Keputusan ujikaji dan analisis teori
menggunakan teorem daripada kajian yang telah dijalankan sebelum ini dibincang dan
dibandingkan.Daya mampatan secara tegak memberikan keputusan yang lebih baik
dalam penyerapan tenaga berbanding daya mampatan secara dari sisi.
vii
TABLE OF CONTENTS
CHAPTER TOPIC
DECLARATION
ii
DEDICATION
iii
ACKNOWLEDGEMENT
iv
ABSTRACT
v
ABSTRAK
vi
TABLE OF CONTENT
vii
LIST OF TABLES
xi
LIST OF FIGURES
xii
LIST OF ABBREVIATIONS AND SYMBOLS
xv
LIST OF APPENDICES
1
PAGE
xviii
INTRODUCTION
1
1.1 Background of study
1
1.2 Objectives
2
1.3 Scope
2
viii
CHAPTER TOPIC
2
PAGE
1.4 Chapter outline
3
LITERATURE REVIEW
4
2.1 Energy and momentum in car crashes
4
2.2 Crashworthiness
5
2.3 Energy absorption
7
2.3.1 Mechanical properties of energy absorbers
8
2.3.1.1 Yield strength
9
2.3.1.2 Young's Modulus
10
2.3.1.3 Strain Hardening
10
2.3.1.4 Density
10
2.3.1.5 Strain-rate effects
10
2.4 Energy absorption system
11
2.4.1 Axial crushing on single cylindrical tube
12
2.4.2 Lateral crushing on single cylindrical tube
14
2.4.3 Lateral crushing on multilayer cylindrical tubes
15
2.5 Hardness testing
17
ix
CHAPTER TOPIC
2.5.1 Rockwell Hardness Test
18
2.5.2 Brinell Hardness Test
19
2.5.3 Vickers Hardness Testing
20
2.6 Crash test
3
PAGE
21
2.6.1 Side impact crash testing
21
2.6.2 Ratings criteria
23
METHODOLOGY
25
3.1 Specimen preparation
25
3.1.1 Material used confirmation
25
3.1.2 Specimen for hardness testing
25
3.2 Hardness measurement methods
3.2.1 Procedure for Rockwell Hardness Test
26
27
3.3 Specimen for compression test
28
3.4 Compression test method
29
3.5 Sigmaplot analysis method
30
x
CHAPTER TOPIC
4
PAGE
RESULTS AND DISCUSSIONS
31
4.1 Hardness testing result and discussions
31
4.2 Compression test results
33
4.2.1 Axial loading on a single cylindrical tube
33
4.2.1.1 Comparison between experimental and theory
for axial loading
38
4.2.2 Lateral loading on a single cylindrical tube
45
4.2.3 Lateral loading on multilayer cylindrical tubes
48
4.3 Comparison between single and multilayer cylindrical
tube under lateral loading
5
53
4.4 Energy absorption results
54
CONCLUSION
56
58
REFERENCES
60
APPENDICES
xi
LIST OF TABLES
NO TITLE
PAGE
3.1 Rockwell scales
26
4.1 Rockwell hardness testing result
31
4.2 Hardness value converted to Brinell and Vickers
31
4.3 Dimension of cylindrical tube specimen
39
4.4 Results of cylindrical tube under axial loading
40
4.5 Comparison between experimental and theoretical value of
41
cylindrical tube under axial loading
4.6 Single cylindrical tube under lateral loading
45
4.7 Multilayer cylindrical tubes under lateral loading
49
4.8 Energy absorption results for all loading types
55
xii
LIST OF FIGURES
NO TITLE
PAGE
2.1 The collisions opponent
6
2.2 Load paths on car body elements during frontal impact
7
2.3 Yield strength curve
9
2.4 Tensile tests on sheet steel at strain rate
11
2.5 Impact attenuator features “smart plastic” cylinders
12
2.6 Results for (a) cylindrical tube average diameter D=61.5mm, length
13
L=120.0mm, and thickness t=1.5mm
(b) Average diameter D=45.0mm, length L=150.0mm, and
thickness t=1.5mm.
2.7 The response of a CIPSS compressed under quasi-static conditions
16
2.8 The numerical and experimental force, energy-deflection response of a
16
CIPSS
2.9 Hardness testing techniques
17
2.10 Hardness testing machine
18
2.11 Hardness testing apparatus
18
2.12 Hardness testing concept
19
xiii
NO TITLE
PAGE
2.13 Hardness testing sample result
19
2.14 Brinell number formulation
20
3.1 Hardness testing specimen
25
3.2 Hardness testing machine
27
3.3 Specimen during lathe machining
28
3.4 Finished specimen for single cylindrical tube
28
3.5 Finished welded specimen for multilayer cylindrical tubes
29
3.6 Axial loading on single cylindrical tube
29
3.7 Lateral loading on single cylindrical tube
30
3.8 Lateral loading on multilayer cylindrical tubes
30
4.1
Graph of load against displacement for single cylindrical tube for
specimen 1
34
4.2 Specimen 2 under axial loading
36
4.3 Specimen 3 under axial loading
37
4.4 Graph of load against displacement for all specimens and its average
under axial loading
38
4.5 Graph load against displacement for lateral loading for specimen 1
46
4.6 Specimen 2 under lateral loading
46
4.7 Specimen 3 under lateral loading (from side view)
47
4.8 Graph of load against displacement for all specimens and its average
48
xiv
NO
TITLE
PAGE
4.9
Graph of load against displacement for lateral loading on multilayer
50
cylindrical tubes for specimen 1
4.10 Specimen 2 for multilayer cylindrical tubes under lateral loading
51
4.11 Specimen 3 for multilayer cylindrical tubes under lateral loading
52
4.12 Graph of load against displacement for all multilayer cylindrical
53
tubes and its average
4.13 Graph of compressive load against compressive extension for
single and multilayer tube under lateral loading
54
xv
LIST OF ABBREVIATIONS AND SYMBOLS
A
= Cross Sectional Area ( m 2 )
E
= Young’s εodulus ( N / m2 )
= Stress ( N / m2 )
LMV = Low mass vehicle
SUV = Sports utility vehicles
SID
= Side impact dummies
CIPSS = circular in-plane standard system
xvi
LIST OF APPENDICES
NO
TITLE
A
Project proposal
B
Journal of The crash energy absorption of the vehicles front structure
C
Journal of Numerical simulation of axial crushing of circular tubes
D
Journal of lateral crushing of circular and non-circular tube systems under
quasi static conditions
E
Results for axial loading on single cylindrical tube
F
Results for lateral loading on single cylindrical tube
G
Results for lateral loading on multilayer cylindrical tubes
1
CHAPTER 1
INTRODUCTION
1.1
Background of study
Crashes occur because of various factors including the driver, vehicle,
roadway and environment. Crashes are rare events. Crash and catastrophe analysis has
been discussed frequently in pastimes- traditional engineering. But then, in recent
time, experimental and theoretical analyses became a part of everyday planning as
the world of transportation has become a major sector in the world, and the used of
transports has been a necessity to peoples. The main criteria of safety issue are
vehicles deceleration pulses and deformation of the compartment where good crash
energy management allows increasing the safety of both, vehicles and passengers.
This concept is called crashworthiness; the ability of the vehicles to prevent injuries
to the occupants in the event of a collision.
One measure to view the impact of crash energy is crash analysis. The Crash
analysis depends upon deterministic view such the stochastic view, statistical
analysis and frequency. These parameters play an important role where crash
situations that occur most frequently are chosen from these statistics and are used as
crash test parameters. However, the crash tests costs a huge amount of money
implication that there are only some numbers of tests is realized annually per factory.
Crash analysis helps the experts to investigate accidents as they needed data and
simulations. Through the analysis, the obtained result will helps in creating or
modifying the vehicles structure. The energy absorbed is the most important factors
2
in the analysis, thus it needs more correct techniques in new modeling and
calculating methods. The same goes to other energy absorption devices. As it used
widely for road user safety system or even at construction site, these devices are
tested many times before they are qualified.
This project investigated the crash energy absorption in the study of
cylindrical tube under axial, lateral loading and multilayer cylindrical tube under
lateral loading quasi statically to determine the important parameters by performing
compression test.
1.2
Objectives
In this project, energy absorption, lateral or side impact in a crash will be
studied theoretically. Other than that are to determine the material properties and the
behaviors collapsed and energy absorbed by cylindrical tube.
1.3
Scope
This study will cover the crashworthiness in vehicle’s crash and the energy
absorption during the crash, besides laterally and axially loaded on cylindrical tube.
Hardness test is performed and continued by compression test. Then, the results from
both testing are discussed. The proposal for this project can be referred in Appendix
A.
3
1.4
Chapter outline
This study covered the study of cylindrical tube that is loaded laterally and
axially. First chapter will explain briefly about the background and the objectives of
this study. Then second chapter, will cover about crashworthiness, energy absorption
system and previous studies about crushing on cylindrical tube. After that, methods
and procedure that used in this study will be explained on the third chapter. The next
chapter will be the results and discussion after getting the output .Lastly, the final
chapter will conclude about this study.
4
CHAPTER 2
LITERATURE REVIEW
2.1
Energy and momentum in car crashes
What happens in a crash? When a car traveling at 89 km/h hits a solid object,
the following occurs: At 0.1 second, front bumper and grill collapse. At 0.2 second,
the hood crumples rises and strikes the windshield. Spinning rear wheels lift from the
ground. Fenders begin to wrap themselves around the solid objects. Instinct causes
the driver to stiffen his legs against the impending crash. They snap at the knee joint.
Although the car's frame has been halted, the rest of the car is still going at 89.km/h.
At 0.3 second, the steering wheel starts to disintegrate and the steering column aims
for the driver's chest. At 0.4 second, two feet of the car's front is wrecked, the rear is
still moving at 57 km/h. The driver's body is still traveling at 57 km/h. At 0.5 second,
driver is impaled on the steering column. The blood rushes into his lungs. At 0.6
second, the driver's feet are ripped out of tightly-laced shoes. The brake pedal snaps
off. The car frame buckles in the middle. The driver's head smashes into the
windshield. The rear wheels, still spinning, fall back to the ground. At 0.7 second,
hinges rip loose, doors fly open, and the seats break free striking the driver from
behind. At 0.8 second, the seat striking the driver does not bother him because he is
already dead. 0.9 Second to 1.0 second, the last 3 tenths of a second mean nothing to
the driver. [1]
5
2.2
Crashworthiness
Crashworthiness is defined as capability of motor vehicle structure to
provide adequate protection to its occupant from injury and to its cargo from damage
in the event of crash. [2] Compatibility is the important key to be considered if the
best possible safety for cars of different size and weight is to be achieved, especially
for the design of low mass vehicles (LMV) without excessive reduction of safety
level compared to heavier cars. δεV’s could contribute to reduce fuel consumption
in traffic, provided that they are able to offer a level of safety comparable to larger
cars.
Compatibility in frontal collisions calls for significantly different
deceleration-time curves in rigid barrier impacts for cars with different weight. Cars
designed according to compatibility criteria can change future accident and injury
statistics in a way that injury severity in LMV’s can be reduced significantly. This
lack of compatibility is considered to be the main reason for the unfavorable
appearance of small vehicles in accident statistics. The reasons for the higher injury
risk for occupants of small vehicles can be found in the low mass, which results in a
higher total change of velocity in car to car collisions, and in comparison to heavier
cars, in a usually lower stiffness of the crush zone and the cabin structure. [3]
Crashworthiness is divided into two types which are external crashworthiness
and internal crashworthiness. The external crashworthiness is the first impact during
the collisions. While the internal crashworthiness is the second impact such as
occupant strikes. [4] The condition during the collision between two vehicles is
shown in Figure 2.1.
6
Figure 2.1 The collisions opponent.
It is important to understand the basics of vehicle crash management. The
basic idea is to design vehicle structures which minimize the amount of injurycausing crash energy that reaches the occupants. Generally, this can be accomplished
by developing structural zones that absorb crash energy outside the passenger
compartment which called "crush zones" and they collapse in a prescribed way at
specified loads, thereby providing the appropriate energy absorption and deceleration
of the passenger compartment. Meanwhile, passengers are protected inside the
passenger compartment by restraint systems such as seat belts and air bags. There
has been lot of research and development has been carried out over the years to
design and integrate these systems. In the case of the crush zones, the energy is
absorbed by the folding and bending deformation of the metal structure.
To the strongest extent, automotive engineers attempt to maximize the
transmission of crash energy through the structure axially so that the structure folds
like an accordion as it absorbs the crash energy. This design is rational because
frontal impacts are the most frequent vehicle crashes and cause the most injuries and
fatalities. In vehicle crashes, most of the crash energy is absorbed through the in and
out folding of the side plates of the main energy absorbing structural beams during
the collapse process. The longitudinal beams at the front end of a vehicle generally
act as the main structural members for absorbing crash energy in a frontal impact,
and the crushable length of these components defines the distance over which the
crash energy can be absorbed. Bumper to frame rail attachments are designed to
transfer the impact force directly to the lower front rails. The upper rails also need to
7
be part of the load path to absorb some of the impact energy, and to transfer some of
the force of the crash in order to minimize vehicle bending moment. The design
objective for rails is to balance the load path into the passenger cell of the body
structure so as to distribute the loads between the roof and the floor. The structure
between the rails and the rockers also must be strong enough to resist plastic
deflection into the passenger space. To allow proper functioning of the passenger
restraint system, the bending moment on the passenger compartment must be limited
to avoid collapse of the roof structure and floor bending. Other than axial collapse
resulting from front and rear end crashes, bending collapse is the other common
mode of energy absorption in automotive structural components. A-pillars,
windshield headers and roof side rails are typical structural members where
combined forces cause bending mode collapse. Such collapse is typically caused
either by buckling of the compressed surface or by cracking and tearing of the
surface under tensile stress. Buckling is the preferred mode of collapse because it
results in a more stable and predictable energy absorption. [5]
2.3
Energy absorption
In term of vehicles, during the frontal crash, the longerons absorb most
energy of all vehicles construction elements as shown in Figure 2.2 by load paths on
car body elements during frontal impact. In order to assess the crashworthiness of
longerons, the crash analysis is performed.
Figure 2.2 Load paths on car body elements during frontal impact
the partial fulfillment for awarding the degree of Bachelor of Mechanical Engineering
(Material and Structure)”
Signature
: ……………………………………
Supervisor’s ζame
: Prof. Dr. Md. Radzai Bin Said
Date
: 18th MAY 2009
THE STUDY OF CYLINDRICAL TUBE UNDER QUASI-STATIC LOADING
ILLY SALWANA BINTI ABD RAZAK
UNIVERSITI TEKNIKAL MALAYSIA MELAKA
ii
“I hereby declared this report is mine except summary and each quotation that I have
mentioned the resources”
Signature:…………………………
Author’s ζame: Illy Salwana Abd Razak
Date: 18th May 2009
iii
To my beloved father and mother
iv
ACKNOWLEDGEMENT
The author would like to express gratitude to her supervisor, Prof. Dr. Md.
Radzai Said, for his help, time and encouragement during the course of this project.
The author takes this opportunity to also thank the Faculty of Mechanical
Engineering’s laboratory management for their cooperation especially to the technicians
during performing experimental works at the laboratory.
Special thanks are due to all who has involved in helping to finish this project
v
ABSTRACT
Vehicle’s crash caused a lot of trouble and undesired things. Though, the effect
of the crash can be minimized or prevented as stated as crashworthiness. The
crashworthiness of a vehicle depends on its material and structural. Thus, impact energy
absorption devices is introduced and used in all vehicles structural nowadays. The
impact energy absorption devices are consumable mechanical structure which useable
and useful in any collisions. Thus cylindrical tube is being studied on axially and
laterally impact. An investigation into energy absorption requires an understanding of
materials engineering and structural mechanics. Performance of energy absorbers is
determined from various parameters. From material properties, the common parameters
those are important were determined by hardness test and compression test.
Experimental works and theoretical analysis using theorems from previous studies are
discussed and compared. Axially loading gave better result in energy absorbing
compared to laterally loading.
vi
ABSTRAK
Perlanggaran antara kenderaan menyebabkan pelbagai masalah dan perkaraperkara yang tidak diingini. Bagaimanapun, kesan daripada perlanggaran tersebut boleh
diatasi ataupun dielakkan seperti mana yang disebut sebagai ketahanan kepada kesan
perlanggaran. Ketahanan kepada kesan perlanggaran bergantung kepada bahan yang
digunakan dan struktur kenderaan tersebut. Oleh sebab itu alat penyerapan tenaga pasak
diperkenalkan dan digunakan dalam struktur semua jenis pada hari ini. Alat penyerapan
tenaga pasak adalah bahagian struktur mekanikal yang boleh diganti yang mana boleh
digunakan dan sangat berguna ketika apa jua perlanggaran. Oleh sebab itu tiub silinder
diperkenalkan sebagai satu kajian baru yang mana memfokuskan tentang cara mencipta
dan merekabentuk bahan dan struktur yang boleh menyerap tenaga kinetic secara
berkesan dan boleh dijangka. Kajian tentang penyerapan tenaga memerlukan
pemahaman tentang kejuruteraan bahan dan mekanik struktur. Pelaksanaan alat
penyerap ditentukan oleh bebarapa terma. Dua jenis ujikaji dijalankan bagi menentukan
kebolehan tiub silinder dalam menyerap tenaga. Keputusan ujikaji dan analisis teori
menggunakan teorem daripada kajian yang telah dijalankan sebelum ini dibincang dan
dibandingkan.Daya mampatan secara tegak memberikan keputusan yang lebih baik
dalam penyerapan tenaga berbanding daya mampatan secara dari sisi.
vii
TABLE OF CONTENTS
CHAPTER TOPIC
DECLARATION
ii
DEDICATION
iii
ACKNOWLEDGEMENT
iv
ABSTRACT
v
ABSTRAK
vi
TABLE OF CONTENT
vii
LIST OF TABLES
xi
LIST OF FIGURES
xii
LIST OF ABBREVIATIONS AND SYMBOLS
xv
LIST OF APPENDICES
1
PAGE
xviii
INTRODUCTION
1
1.1 Background of study
1
1.2 Objectives
2
1.3 Scope
2
viii
CHAPTER TOPIC
2
PAGE
1.4 Chapter outline
3
LITERATURE REVIEW
4
2.1 Energy and momentum in car crashes
4
2.2 Crashworthiness
5
2.3 Energy absorption
7
2.3.1 Mechanical properties of energy absorbers
8
2.3.1.1 Yield strength
9
2.3.1.2 Young's Modulus
10
2.3.1.3 Strain Hardening
10
2.3.1.4 Density
10
2.3.1.5 Strain-rate effects
10
2.4 Energy absorption system
11
2.4.1 Axial crushing on single cylindrical tube
12
2.4.2 Lateral crushing on single cylindrical tube
14
2.4.3 Lateral crushing on multilayer cylindrical tubes
15
2.5 Hardness testing
17
ix
CHAPTER TOPIC
2.5.1 Rockwell Hardness Test
18
2.5.2 Brinell Hardness Test
19
2.5.3 Vickers Hardness Testing
20
2.6 Crash test
3
PAGE
21
2.6.1 Side impact crash testing
21
2.6.2 Ratings criteria
23
METHODOLOGY
25
3.1 Specimen preparation
25
3.1.1 Material used confirmation
25
3.1.2 Specimen for hardness testing
25
3.2 Hardness measurement methods
3.2.1 Procedure for Rockwell Hardness Test
26
27
3.3 Specimen for compression test
28
3.4 Compression test method
29
3.5 Sigmaplot analysis method
30
x
CHAPTER TOPIC
4
PAGE
RESULTS AND DISCUSSIONS
31
4.1 Hardness testing result and discussions
31
4.2 Compression test results
33
4.2.1 Axial loading on a single cylindrical tube
33
4.2.1.1 Comparison between experimental and theory
for axial loading
38
4.2.2 Lateral loading on a single cylindrical tube
45
4.2.3 Lateral loading on multilayer cylindrical tubes
48
4.3 Comparison between single and multilayer cylindrical
tube under lateral loading
5
53
4.4 Energy absorption results
54
CONCLUSION
56
58
REFERENCES
60
APPENDICES
xi
LIST OF TABLES
NO TITLE
PAGE
3.1 Rockwell scales
26
4.1 Rockwell hardness testing result
31
4.2 Hardness value converted to Brinell and Vickers
31
4.3 Dimension of cylindrical tube specimen
39
4.4 Results of cylindrical tube under axial loading
40
4.5 Comparison between experimental and theoretical value of
41
cylindrical tube under axial loading
4.6 Single cylindrical tube under lateral loading
45
4.7 Multilayer cylindrical tubes under lateral loading
49
4.8 Energy absorption results for all loading types
55
xii
LIST OF FIGURES
NO TITLE
PAGE
2.1 The collisions opponent
6
2.2 Load paths on car body elements during frontal impact
7
2.3 Yield strength curve
9
2.4 Tensile tests on sheet steel at strain rate
11
2.5 Impact attenuator features “smart plastic” cylinders
12
2.6 Results for (a) cylindrical tube average diameter D=61.5mm, length
13
L=120.0mm, and thickness t=1.5mm
(b) Average diameter D=45.0mm, length L=150.0mm, and
thickness t=1.5mm.
2.7 The response of a CIPSS compressed under quasi-static conditions
16
2.8 The numerical and experimental force, energy-deflection response of a
16
CIPSS
2.9 Hardness testing techniques
17
2.10 Hardness testing machine
18
2.11 Hardness testing apparatus
18
2.12 Hardness testing concept
19
xiii
NO TITLE
PAGE
2.13 Hardness testing sample result
19
2.14 Brinell number formulation
20
3.1 Hardness testing specimen
25
3.2 Hardness testing machine
27
3.3 Specimen during lathe machining
28
3.4 Finished specimen for single cylindrical tube
28
3.5 Finished welded specimen for multilayer cylindrical tubes
29
3.6 Axial loading on single cylindrical tube
29
3.7 Lateral loading on single cylindrical tube
30
3.8 Lateral loading on multilayer cylindrical tubes
30
4.1
Graph of load against displacement for single cylindrical tube for
specimen 1
34
4.2 Specimen 2 under axial loading
36
4.3 Specimen 3 under axial loading
37
4.4 Graph of load against displacement for all specimens and its average
under axial loading
38
4.5 Graph load against displacement for lateral loading for specimen 1
46
4.6 Specimen 2 under lateral loading
46
4.7 Specimen 3 under lateral loading (from side view)
47
4.8 Graph of load against displacement for all specimens and its average
48
xiv
NO
TITLE
PAGE
4.9
Graph of load against displacement for lateral loading on multilayer
50
cylindrical tubes for specimen 1
4.10 Specimen 2 for multilayer cylindrical tubes under lateral loading
51
4.11 Specimen 3 for multilayer cylindrical tubes under lateral loading
52
4.12 Graph of load against displacement for all multilayer cylindrical
53
tubes and its average
4.13 Graph of compressive load against compressive extension for
single and multilayer tube under lateral loading
54
xv
LIST OF ABBREVIATIONS AND SYMBOLS
A
= Cross Sectional Area ( m 2 )
E
= Young’s εodulus ( N / m2 )
= Stress ( N / m2 )
LMV = Low mass vehicle
SUV = Sports utility vehicles
SID
= Side impact dummies
CIPSS = circular in-plane standard system
xvi
LIST OF APPENDICES
NO
TITLE
A
Project proposal
B
Journal of The crash energy absorption of the vehicles front structure
C
Journal of Numerical simulation of axial crushing of circular tubes
D
Journal of lateral crushing of circular and non-circular tube systems under
quasi static conditions
E
Results for axial loading on single cylindrical tube
F
Results for lateral loading on single cylindrical tube
G
Results for lateral loading on multilayer cylindrical tubes
1
CHAPTER 1
INTRODUCTION
1.1
Background of study
Crashes occur because of various factors including the driver, vehicle,
roadway and environment. Crashes are rare events. Crash and catastrophe analysis has
been discussed frequently in pastimes- traditional engineering. But then, in recent
time, experimental and theoretical analyses became a part of everyday planning as
the world of transportation has become a major sector in the world, and the used of
transports has been a necessity to peoples. The main criteria of safety issue are
vehicles deceleration pulses and deformation of the compartment where good crash
energy management allows increasing the safety of both, vehicles and passengers.
This concept is called crashworthiness; the ability of the vehicles to prevent injuries
to the occupants in the event of a collision.
One measure to view the impact of crash energy is crash analysis. The Crash
analysis depends upon deterministic view such the stochastic view, statistical
analysis and frequency. These parameters play an important role where crash
situations that occur most frequently are chosen from these statistics and are used as
crash test parameters. However, the crash tests costs a huge amount of money
implication that there are only some numbers of tests is realized annually per factory.
Crash analysis helps the experts to investigate accidents as they needed data and
simulations. Through the analysis, the obtained result will helps in creating or
modifying the vehicles structure. The energy absorbed is the most important factors
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in the analysis, thus it needs more correct techniques in new modeling and
calculating methods. The same goes to other energy absorption devices. As it used
widely for road user safety system or even at construction site, these devices are
tested many times before they are qualified.
This project investigated the crash energy absorption in the study of
cylindrical tube under axial, lateral loading and multilayer cylindrical tube under
lateral loading quasi statically to determine the important parameters by performing
compression test.
1.2
Objectives
In this project, energy absorption, lateral or side impact in a crash will be
studied theoretically. Other than that are to determine the material properties and the
behaviors collapsed and energy absorbed by cylindrical tube.
1.3
Scope
This study will cover the crashworthiness in vehicle’s crash and the energy
absorption during the crash, besides laterally and axially loaded on cylindrical tube.
Hardness test is performed and continued by compression test. Then, the results from
both testing are discussed. The proposal for this project can be referred in Appendix
A.
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1.4
Chapter outline
This study covered the study of cylindrical tube that is loaded laterally and
axially. First chapter will explain briefly about the background and the objectives of
this study. Then second chapter, will cover about crashworthiness, energy absorption
system and previous studies about crushing on cylindrical tube. After that, methods
and procedure that used in this study will be explained on the third chapter. The next
chapter will be the results and discussion after getting the output .Lastly, the final
chapter will conclude about this study.
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CHAPTER 2
LITERATURE REVIEW
2.1
Energy and momentum in car crashes
What happens in a crash? When a car traveling at 89 km/h hits a solid object,
the following occurs: At 0.1 second, front bumper and grill collapse. At 0.2 second,
the hood crumples rises and strikes the windshield. Spinning rear wheels lift from the
ground. Fenders begin to wrap themselves around the solid objects. Instinct causes
the driver to stiffen his legs against the impending crash. They snap at the knee joint.
Although the car's frame has been halted, the rest of the car is still going at 89.km/h.
At 0.3 second, the steering wheel starts to disintegrate and the steering column aims
for the driver's chest. At 0.4 second, two feet of the car's front is wrecked, the rear is
still moving at 57 km/h. The driver's body is still traveling at 57 km/h. At 0.5 second,
driver is impaled on the steering column. The blood rushes into his lungs. At 0.6
second, the driver's feet are ripped out of tightly-laced shoes. The brake pedal snaps
off. The car frame buckles in the middle. The driver's head smashes into the
windshield. The rear wheels, still spinning, fall back to the ground. At 0.7 second,
hinges rip loose, doors fly open, and the seats break free striking the driver from
behind. At 0.8 second, the seat striking the driver does not bother him because he is
already dead. 0.9 Second to 1.0 second, the last 3 tenths of a second mean nothing to
the driver. [1]
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2.2
Crashworthiness
Crashworthiness is defined as capability of motor vehicle structure to
provide adequate protection to its occupant from injury and to its cargo from damage
in the event of crash. [2] Compatibility is the important key to be considered if the
best possible safety for cars of different size and weight is to be achieved, especially
for the design of low mass vehicles (LMV) without excessive reduction of safety
level compared to heavier cars. δεV’s could contribute to reduce fuel consumption
in traffic, provided that they are able to offer a level of safety comparable to larger
cars.
Compatibility in frontal collisions calls for significantly different
deceleration-time curves in rigid barrier impacts for cars with different weight. Cars
designed according to compatibility criteria can change future accident and injury
statistics in a way that injury severity in LMV’s can be reduced significantly. This
lack of compatibility is considered to be the main reason for the unfavorable
appearance of small vehicles in accident statistics. The reasons for the higher injury
risk for occupants of small vehicles can be found in the low mass, which results in a
higher total change of velocity in car to car collisions, and in comparison to heavier
cars, in a usually lower stiffness of the crush zone and the cabin structure. [3]
Crashworthiness is divided into two types which are external crashworthiness
and internal crashworthiness. The external crashworthiness is the first impact during
the collisions. While the internal crashworthiness is the second impact such as
occupant strikes. [4] The condition during the collision between two vehicles is
shown in Figure 2.1.
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Figure 2.1 The collisions opponent.
It is important to understand the basics of vehicle crash management. The
basic idea is to design vehicle structures which minimize the amount of injurycausing crash energy that reaches the occupants. Generally, this can be accomplished
by developing structural zones that absorb crash energy outside the passenger
compartment which called "crush zones" and they collapse in a prescribed way at
specified loads, thereby providing the appropriate energy absorption and deceleration
of the passenger compartment. Meanwhile, passengers are protected inside the
passenger compartment by restraint systems such as seat belts and air bags. There
has been lot of research and development has been carried out over the years to
design and integrate these systems. In the case of the crush zones, the energy is
absorbed by the folding and bending deformation of the metal structure.
To the strongest extent, automotive engineers attempt to maximize the
transmission of crash energy through the structure axially so that the structure folds
like an accordion as it absorbs the crash energy. This design is rational because
frontal impacts are the most frequent vehicle crashes and cause the most injuries and
fatalities. In vehicle crashes, most of the crash energy is absorbed through the in and
out folding of the side plates of the main energy absorbing structural beams during
the collapse process. The longitudinal beams at the front end of a vehicle generally
act as the main structural members for absorbing crash energy in a frontal impact,
and the crushable length of these components defines the distance over which the
crash energy can be absorbed. Bumper to frame rail attachments are designed to
transfer the impact force directly to the lower front rails. The upper rails also need to
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be part of the load path to absorb some of the impact energy, and to transfer some of
the force of the crash in order to minimize vehicle bending moment. The design
objective for rails is to balance the load path into the passenger cell of the body
structure so as to distribute the loads between the roof and the floor. The structure
between the rails and the rockers also must be strong enough to resist plastic
deflection into the passenger space. To allow proper functioning of the passenger
restraint system, the bending moment on the passenger compartment must be limited
to avoid collapse of the roof structure and floor bending. Other than axial collapse
resulting from front and rear end crashes, bending collapse is the other common
mode of energy absorption in automotive structural components. A-pillars,
windshield headers and roof side rails are typical structural members where
combined forces cause bending mode collapse. Such collapse is typically caused
either by buckling of the compressed surface or by cracking and tearing of the
surface under tensile stress. Buckling is the preferred mode of collapse because it
results in a more stable and predictable energy absorption. [5]
2.3
Energy absorption
In term of vehicles, during the frontal crash, the longerons absorb most
energy of all vehicles construction elements as shown in Figure 2.2 by load paths on
car body elements during frontal impact. In order to assess the crashworthiness of
longerons, the crash analysis is performed.
Figure 2.2 Load paths on car body elements during frontal impact