Analytical Study On Control Of Buckling Lobe Onset For Hollow Circular Tube Under Axial Impact.
SUPERVISOR DECLARATION
“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 Structures)”
Signature : ……….
Supervisor’s Name : MR. HAIRUL BIN BAKRI
Date : ……….
Signature : ……….
Supervisor’s Name : PROF. DR. MD RADZAI
Date : ……….
(2)
ANALYTICAL STUDY ON CONTROL OF BUCKLING LOBE ONSET FOR
HOLLOW CIRCULAR TUBE UNDER AXIAL IMPACT
DZULHUSNI BIN OTHMAN
A report submitted in partial fulfillment of
the requirements for the award of the degree of
Bachelor of Mechanical Engineering (Structure and Materials)
Faculty of Mechanical Engineering
Universiti Teknikal Malaysia Melaka
(3)
iii
“I hereby declared that this report entitled “Analytical Study on Control of Buckling
Lobe Onset for Hollow Circular Tube under Axial Loading” is written all by me and it is
my own effort except the summary and each quotation that I have mentioned their
resources”
Signature
: ……….
Name of Candidate
: DZULHUSNI BIN OTHMAN
(4)
iv
To my beloved father and mother
(5)
v
ACKNOWLEDGEMENT
“In the name of Allah, the most Gracious, most Powerful, and the most Merciful”
All praise to the Almighty for His blessings and guidance, I can finish-up this
“Projek Sarjana Muda 1 (PSM 1)”. Without the strength gave to me from the God, this
project report can’t be finish within the time provided. First of all, I would like to
express my biggest appreciation to my beloved Project Supervisor; Encik Hairul bin
Bakri for all his precious supports and advises during completing this project report.
Furthermore, he guides me consistently and give full dedication throughout the semester.
After that, I would like to thank Professor Madya Ahmad Rivai for teaching me to
perform the finite element analysis to the solid structure.
I also would like to thank my beloved parents especially my father and my
mother for giving me the truly support and motivation to finish this project report. I am
very appreciating of their understanding towards my commitment to finish the PSM 1
report. My big thanks to my friends especially to Nik Muhd Afiq bin Nik Muhd Arif
who gave me the precious help and support in completing this project. Last but not least,
I would like to thanks all the people who have involve directly and indirectly to give
contribution to complete the PSM 1.
(6)
vi
ABSTRACT
Nowadays, the thin-walled tubular structures are commonly used as the
strengthening members of a car’s body in automotive industry. In car’s body, the
strengthening members are the most critical and important parts because it can protect
the car’s users from suffering the bad injury during accident by absorbing the impact
energy that arises during the collision. In order to control the deformation of the solid
structure due to impact energy, the solid mass is attached to that structure. The buckling
lobe is expected to be occurring at the position where the solid mass is attached. This is
due to the inertia forces that causes the bending deformation occur due to a great
velocity change during collision at the solid mass attached area. Thus, the deformation
of the solid structures can be control. This project will focus on the analytical study on
control of buckling lobe onset for hollow circular tube under axial impact. The hollow
cylindrical tube is used in this project and the solid mass that use the material of steel
SS400 is attached to it. The aluminum A6063-T6 is used as a material of hollow
cylindrical tube because it is used widely in automotive industry to replace the steel. The
analysis of the deformation of the hollow cylindrical tube will be carry on by using the
ABAQUS analysis software. The main focus of the analysis is to compare the
deformation pattern result between the hollow cylindrical tube that attached with solid
mass and without solid mass attachment. At the end of the project, the analysis result
shows that the first buckling lobe onset is occur at the location where the solid mass is
attached. The velocity of the impact also affect the deformation pattern of the hollow
cylindrical tube where high velocity of the impact will bring large deformation to the
hollow cylindrical tube compared to the small impact velocity. Finally, this project show
that the deformation of the aluminum A6063-T6 hollow cylindrical tube structure can be
controlled and predicted and further study need to be to this mechanism before it can be
applied in real world especially in automotive and construction sectors.
(7)
vii
ABSTRAK
Pada masa kini, struktur bererongga yang mempunyai dinding nipis kebiasaanya
telah digunakan sebagai penguat rangka kereta dalam industri automotif. Pada rangka
kereta, penguat rangka kereta merupakan komponen yang paling kritikal dan penting
kerana ia dapat melindungi pengguna kereta daripada menanggung kecederaan yang
serius sewaktu kereta mengalami pelanggaran dengan menyerap tenaga hentaman yang
timbul sewaktu perlanggaran tersebut. Dalam usaha untuk mengawal pencacatan
struktur pepejal disebabkan tenaga hentaman, jisim padat disangkut pada struktur
berkenaan. Lobus pembengkokan pertama dijangka berlaku pada kawasan di mana jisim
padat diletakkan. Ini adalah disebabkan daya inersia yang menyebabkan pencacatan
lengkungan berlaku disebabkan perubahan kelajuan yang sangat besar di kawasan jisim
padat disangkut sewaktu perlanggaran. Oleh itu pencacatan struktur pepejal boleh
dikawal. Projek ini akan member fokus kepada pembelajaran analitikal untuk mengawal
pembentukan lobus pembengkokan untuk tiub silinder yang berongga apabila hentaman
berlaku pada paksi lurus. Tiub silinder berongga digunakan dalam projek ini dan jisim
padat yang diperbuat daripada besi SS400 disangkut pada silinder tersebut. Aluminium
A6063-T6 digunakan sebagai bahan untuk tiub silinder berongga kerana ia digunakan
secara meluas dalam industri automotif menggantikan besi. Analisa kecacatan pada tiub
silinder berongga dijalankan dengan menggunakan perisian analisa ABAQUS. Fokus
utama analisa adalah untuk membandingkan keputusan corak kecacatan di antara tiub
silinder berongga yang disangkut dengan jisim padat dan tiub yang tidak disangkut. Di
akhir projek, keputusan analisis menunjukka lobus pembengkokan pertama berlaku di
lokasi di mana jisim padat diletakkan. Kelajuan hentaman juga memberi kesan kepada
corak kecacatan pada tiub silinder di mana kelajuan yang tinggi memberi kecacatan
yang besar berbanding kelajuan yang perlahan. Akhirnya, projek ini menunjukkan
bahawa kecacatan pada struktur tiub silinder boleh dikawal dan dijangka.
(8)
viii
TABLE OF CONTENT
CHAPTER
TOPICS
PAGE
DECLARATION
i
DEDICATION
iv
ACKNOWLEDMENT
v
ABSTRACT
vi
ABSTRAK
vii
TABLE OF CONTENT
viii
LIST OF TABLES
xi
LIST OF FIGURES
xii
LIST OF APPENDICES
xiv
LIST OF ABBREVIATIONS AND
SYMBOLS
xv
CHAPTER 1
INTRODUCTION
1.0 Introduction
1
1.1 Problem Statement
1
1.2 Objectives
2
1.3 Scopes
3
CHAPTER 2
LITERATURE REVIEW
2.1 Introduction
4
2.2 Buckling mechanism
4
2.3 Aluminum alloy tube used in car
5
(9)
ix
2.4 Aluminum A6063 alloy used as
car’s body space frame
6
2.5 Control of onset of buckling lobe
with the aid of inertia effect
11
2.6 Project paper review
14
2.6.1 Project paper 1
14
2.6.2 Project paper 2
15
2.6.3 Project paper 3
16
CHAPTER 3
METHODOLOGY
3.1 Introduction
17
3.1.1 Major Project Flowchart
18
3.1.2 Project Design Process Flowchart
19
3.2 Project flow chart
20
3.3 Data collection
22
3.4 Specimen dimension
22
3.5 Specimen and solid mass material
properties
24
3.6 Creating the specimen parts
24
3.7 Defining material properties
29
3.8 Parts assembly
34
3.9 Meshing process
36
3.10 Material section
38
3.11 Steps
40
3.12 Interaction
42
3.13 Defining boundary condition
44
3.14 Load and impact velocity
47
(10)
x
3.16 Research parameters
52
3.16.1 Value of load attach to
specimen (axial load)
52
3.16.2 Attachment of solid mass
52
3.16.3 Point of solid mass
52
3.16.4 Velocity of the load applied
53
3.16.5 Specimen materials
53
CHAPTER 4
RESULT
54
4.1 Introduction
54
4.2 Results
55
4.2.1 Analysis of different velocities
of loading
55
4.2.2 Analysis of different point of
solid mass attachment
62
CHAPTER 5
DISCUSSION
5.1 Introduction
65
5.2 Deformation pattern when velocities
are varied
66
5.3 Deformation pattern when point of
solid mass is varied
69
5.4 Graph analysis
71
5.4.1 Analysis of graph for solid mass
attached at top of tube
71
5.4.2 Analysis of graph for solid mass
attached at middle of tube
73
5.4.3 Analysis of graph for solid mass
attached at bottom of tube
(11)
xi
5.4.4 Analysis of graph for the tube
without solid mass attached
77
5.4.5 Analysis of combination graph
79
5.5 Calculation for inertia force P and Q
81
CHAPTER 6
CONCLUSION AND
RECOMMENDATION
86
4.1 Conclusion
86
4.2 Recommendation
87
REFERENCES
BIBLIOGRAPHY
88
92
(12)
xi
LIST OF TABLE
TABLES NO.
TITLE
PAGE
3.4.1
Specimen shape and dimension
23
(13)
xii
LIST OF FIGURES
FIGURE NO.
TITLE
PAGE
2.4.1
Aluminum A6063 alloy extruded tube specimens
with thickness of 1.5mm.
8
2.4.2
Load displacement curves obtained from the
dynamic compressive test for the aluminum A6063
alloy extruded tube specimen with thickness of
1.5mm.
8
2.4.3
Load displacement curves obtained from the
dynamic compressive test with strain rate of 1[1/s]
for the Aluminum A6063 alloy extruded tube
specimens.
10
2.4.4
Aluminum A6063 alloy extruded tube specimens
with thickness of 1.5, 2.0, and 3.0 mm for specimen
B, C, and D respectively deformed after the
dynamic compressive test
10
2.5.1
Inertia forces arisen by rectangular solid mass
attached to the wall
11
2.5.2
Collapse pattern of the specimen
13
3.2.1
Major Project Flowchart
20
3.2.2
Project Design Process Flowchart
21
3.4.1
Specimen assembly geometry
22
3.6.1
Part icon in AbaqusCAE 6.9-EFI software
26
3.6.2
ABAQUS create part interface
27
(14)
xiii
3.7.1
Materials icon in AbaqusCAE 6.9-EFI software
29
3.7.2
Material density interface for Aluminum A6063-T6
alloy materials
30
3.7.3
Material properties defining for the Aluminum
A6063-T6 alloy materials
31
3.7.4
Material defining interface for Steel SS400 material
32
3.7.5
Plastic behaviours rate dependent interface
32
3.7.6
Material density interface for Steel SS400 materials
33
3.8.1
3.8.2
Assembly icon in AbaqusCAE 6.9-EFI software
Create Instance interface
34
36
3.9.1
The meshing interface for the hollow cylindrical
tube
36
3.9.2
Global seeds interface
37
3.9.3
Element type interface in meshing commands
37
3.10.1
Material Section icon
38
3.10.2
Material Section interfaces
39
3.10.3
Material Section Assignment for the hollow
cylinder and the solid mass
39
3.11.1
The “Step” icon in AbaqusCAE software
40
3.11.2
The “Step” command interfaces
41
3.12.1
“Interaction” command icon in AbaqusCAE
software
42
3.12.2
Interaction command interface
43
3.12.3
Surface selection interface
43
3.13.1
Boundary condition of the top plate
45
3.13.2
Boundary condition of the hollow cylindrical tube
45
3.13.3
Boundary condition of the bottom support
46
3.14.1
Inertia command icon
47
3.14.2
Velocity command icon
48
3.14.3
Inertia command interfaces
48
3.14.4
Velocity command icon
49
(15)
xiv
3.15.1
“Job” icon in the AbaqusCAE software
50
3.15.2
“Job” command interfaces
51
3.15.3
Simulation process interface
51
4.1
Deformation pattern of hollow cylindrical tube
without solid mass attachment at different time
intervals.
57
4.2
Deformation pattern of hollow cylindrical tube with
solid mass attachment at the top of the tube at
different time intervals.
57
4.3
Deformation pattern of hollow cylindrical tube
without solid mass attachment at different time
intervals.
59
4.4
Deformation pattern of hollow cylindrical tube with
solid mass attachment at the top of the tube at
different time intervals.
59
4.5
Deformation pattern of hollow cylindrical tube
without solid mass attachment at different time
intervals.
61
4.6
Deformation pattern of hollow cylindrical tube with
solid mass attachment at the top at different time
intervals.
61
4.7
Deformation pattern of hollow cylindrical tube with
solid mass attachment at the top of the tube at
different time intervals.
62
4.8
Deformation pattern of hollow cylindrical tube with
solid mass attachment at the middle of the tube at
different time intervals.
63
4.9
Deformation pattern of hollow cylindrical tube with
solid mass attachment at the bottom of the tube at
different time intervals
(16)
xv
5.1
Buckling lobe onset region above solid mass
attachment area
66
5.2
The Aluminum A6063-T6 hollow cylindrical tube
deformation pattern at 0.04s
67
5.3
Area of initial buckling lobe
69
5.4
The deformation pattern of the Aluminum
A6063-T6 hollow cylindrical tube without solid mass
attached
70
5.5
Graph of Impact force versus time interval for the
Aluminum A6063-T6 hollow cylindrical tube that
was attached by solid mass on top
71
5.6
Graph of Impact force versus time interval for the
Aluminum A6063-T6 hollow cylindrical tube that
was attached by solid mass at the middle
73
5.7
Graph of Impact force versus time interval for the
Aluminum A6063-T6 hollow cylindrical tube that
was attached by solid mass on the bottom
75
5.8
Graph of Impact force versus time interval for the
Aluminum A6063-T6 hollow cylindrical tube that
was not attached by solid mass
77
5.9
Graph of Impact force versus time interval for the
Aluminum A6063-T6 hollow cylindrical tube for 4
cases
(17)
xiv
LIST OF APPENDICES
APPENDIX
TITLE
PAGE
A
Abaqus Simulation data
92
B
Gantt chart PSM 2
118
(18)
xv
LIST OF ABBREVIATION AND SYMBOLS
w
=
width of square tube
ρ
=
density
=
length of square tube
a
=
acceleration at solid mass
x
=
distance
P
=
force push the wall
Q
=
force acts along the wall
E
=
Young Modulus
V
=
Poisson ratio
σ
=
yield stress
n
=
exponent
C
=
multiplier
d0
=
outer diameter
di
=
internal diameter
t
=
thickness
(19)
1
CHAPTER 1
INTRODUCTION
1.0 Introduction
This chapter will cover on the objective of the project, the problem statement,
and the project scope. Furthermore, the information of the project will be stated clearly
to enhance the understanding as a method to achieve the project goal. In this research,
the focus is given on investigating the deformation of hollow circular tube subjected to
the axial impact.
1.1 Problem Statement
Nowadays, in car manufacturing industry, the vehicle body is properly designed
to absorb the impact energy efficiently during the collision. The vehicle body must be
built properly using the proper designs and materials to ensure that the life of the vehicle
users is protected. The two main factors that need to be focus when designing the car
body are the safety factor and the environmental factor. In terms of safety factor, the
structure of the vehicle body must have the capability to control the buckling during the
collision. For example, the car body can be set to deform at the frontal part only so that
the car’s users life can be protected.
(20)
2
To enhance the capability of the vehicle body to absorb the impact energy during
the collision and save the life of the vehicle users, the well strengthening member of the
car body need to be designed and built. One of the methods is to attach the solid mass at
the structure to control the deformation of the structure.
In terms of environmental factor, the car’s body must have lighter weight and
build by the material that can be recycled. The lighter weight of a car’s body can help
reducing the raw material usage and thus can save the energy used in moving cars. Thus,
the production of the green house gases can be reduced. This gas is known as Carbon
Dioxide (C ). In Malaysia, the air pollution is the main environmental problem that is
yet to be totally solved. The bus and lorry is the main vehicles that produce a lot of
gases. If the car’s body weight is heavy, then, a lot of the energy is needed to move the
car. So, the selection of the material needed to build the car’s body is also important in
term of safety factor and environmental factor.
The three important criteria that are used to select the material of the car’s body
are the strength of the material, the weight, and the recycle capabilities. Therefore, the
aluminum material is widely used in automotive industry to replace the steel because it
is not only give the lighter weight to the car’s body but can also efficiently absorb the
impact energy well.
1.2 Objectives
1.2.1 To investigate whether buckling process of the hollow cylindrical tube can
be controlled or not
1.2.2 To design numerical model by using FEM or ABAQUS in order to control
the deformation of the hollow circular tube when the axial impact is
applied.
(21)
3
1.3 Scope
The scope of the project will mainly focus on:
1.3.1 Literature review on buckling mechanism and method to control buckling
1.3.2 Design numerical model and conduct numerical analysis on controlling the
deformation of hollow cylinder tube when the solid mass is attached
1.3.3 Investigate and conclude the mechanism of deformation of hollow circular
(22)
4
CHAPTER 2
LITERATURE REVIEW
2.1 Introduction
This chapter will cover on the overview of the project which consists of the
buckling mechanism of cylindrical shells under axial impact, the inertia force theory,
and the material selection. Besides that, this project will review about the characteristics
of the aluminum alloy in terms of its deformation pattern, strength, and its performance
behavior. Furthermore, this chapter will also cover the deformation control using the
solid mass attached.
2.2 Buckling Mechanism
In the structure analysis, the buckling mechanism is the critical part that must be
exactly determined by the designers and engineers. The buckling of the structure must
be properly controlled to avoid failure in the structure when the load or force is applied
to the structure.
(23)
5
According to the (Xinsheng, X et al. 2009), the buckling mechanism of the
cylindrical shells under axial impact are divide into two categories which are the
short-wave buckling and the long-short-wave buckling. The short-short-wave buckling is also known as
dynamic local buckling and the long-wave buckling is known as global buckling.
Wang (2002) stated that the axisymmetric and non-axisymmetric buckling
mechanism will depend on the axial impact velocity and the cylindrical shells thickness.
Cylindrical shells that have very thin walls are easy to bulk when the axial compressive
loads are subjected to the structure. Mandra and Mazzolani (1997) stated that the
cylindrical shells are very sensitive to initial geometric imperfections.
2.3 Aluminum Alloy tube used in car body
The movement towards using light weight vehicles body represents a significant
engineering challenge to the design and manufacturing sectors of the automotive
industry. Nowadays, the automotive industry needs to consider aluminum alloy as a
potential replacements for low-strength steel structural components. The change of the
material used to replace the steel must not risk the structural integrity of the parts or
sacrifice the energy absorption characteristics of the vehicle in a collision event. (Dong,
K. et al. 1998)
Several automotive parts are being fabricated from the tube-stock and undergo
various stages of forming that can consume a considerably degree of material ductility.
According to the Oliveira and Michael (2005), the two main types of energy absorption
structures used in automobiles are axial crush and s-rail structures. S-rails are used in
side-rail support frames and may be stamped from sheet metal and welded together or
fabricated from the tube stock using a pre-bending and hydro-forming operation. (Dong,
K. et al.1998)
(24)
6
Bouchet and Jacquelin (2002), review about the value of impact force and the
acceleration that must not exceed a certain impulse span. The objective is to reduce the
disparities between the initial and the final level of deceleration and force by increasing
the energy absorption capacities within the free crushing space available in the vehicle
front part. Thus, the damage of the people and the structure can be minimized.
During a collision, the longitudinal girders are the one of the most important
components for absorbing the energy. (Dong, K. et al. 1998)
Tubes based on steel and aluminum alloys collapse by plastic buckling in a
concertina or diamond mode with the formation of a series of progressive plastic folds
absorbing typically in range of 15 to 30kJ/kg in energy.
Wang (2002) state that the development of body parts and structural elements
based on the aluminum alloy can cause some problems in the case of external stresses
due to the shock or impact besides extreme environmental conditions. (Dong, K. et al.
1998)
The type of aluminum alloy that used in designing the car body space frame is an
A6063 alloy. The aluminum A6063 alloy are the major precipitation strengthening
alloys and have the merit of high extrusion efficiency compared with the other types of
aluminum alloy. The behavior of the aluminum A6063 alloy used in the car body has
been analyzed.
2.4 Aluminum A6063 Alloy used in car body Space Frame
Instead of replacement of the use of the steels with the aluminum alloys in saving
the weight of a vehicle body, space frame has recently been developed and is use widely
in designing the structure of a car body. The space frame use the aluminum alloys
extruded in the form of thin tube that has the dimension approximately within 1 to 3
millimeters thickness with the same width, and complicated geometry to carry the load.
(1)
CHAPTER 1
INTRODUCTION
1.0 Introduction
This chapter will cover on the objective of the project, the problem statement, and the project scope. Furthermore, the information of the project will be stated clearly to enhance the understanding as a method to achieve the project goal. In this research, the focus is given on investigating the deformation of hollow circular tube subjected to the axial impact.
1.1 Problem Statement
Nowadays, in car manufacturing industry, the vehicle body is properly designed to absorb the impact energy efficiently during the collision. The vehicle body must be built properly using the proper designs and materials to ensure that the life of the vehicle users is protected. The two main factors that need to be focus when designing the car body are the safety factor and the environmental factor. In terms of safety factor, the structure of the vehicle body must have the capability to control the buckling during the collision. For example, the car body can be set to deform at the frontal part only so that the car’s users life can be protected.
(2)
To enhance the capability of the vehicle body to absorb the impact energy during the collision and save the life of the vehicle users, the well strengthening member of the car body need to be designed and built. One of the methods is to attach the solid mass at the structure to control the deformation of the structure.
In terms of environmental factor, the car’s body must have lighter weight and build by the material that can be recycled. The lighter weight of a car’s body can help reducing the raw material usage and thus can save the energy used in moving cars. Thus, the production of the green house gases can be reduced. This gas is known as Carbon Dioxide (C ). In Malaysia, the air pollution is the main environmental problem that is yet to be totally solved. The bus and lorry is the main vehicles that produce a lot of gases. If the car’s body weight is heavy, then, a lot of the energy is needed to move the car. So, the selection of the material needed to build the car’s body is also important in term of safety factor and environmental factor.
The three important criteria that are used to select the material of the car’s body are the strength of the material, the weight, and the recycle capabilities. Therefore, the aluminum material is widely used in automotive industry to replace the steel because it is not only give the lighter weight to the car’s body but can also efficiently absorb the impact energy well.
1.2 Objectives
1.2.1 To investigate whether buckling process of the hollow cylindrical tube can be controlled or not
1.2.2 To design numerical model by using FEM or ABAQUS in order to control the deformation of the hollow circular tube when the axial impact is applied.
(3)
1.3 Scope
The scope of the project will mainly focus on:
1.3.1 Literature review on buckling mechanism and method to control buckling 1.3.2 Design numerical model and conduct numerical analysis on controlling the
deformation of hollow cylinder tube when the solid mass is attached 1.3.3 Investigate and conclude the mechanism of deformation of hollow circular
(4)
CHAPTER 2
LITERATURE REVIEW
2.1 Introduction
This chapter will cover on the overview of the project which consists of the buckling mechanism of cylindrical shells under axial impact, the inertia force theory, and the material selection. Besides that, this project will review about the characteristics of the aluminum alloy in terms of its deformation pattern, strength, and its performance behavior. Furthermore, this chapter will also cover the deformation control using the solid mass attached.
2.2 Buckling Mechanism
In the structure analysis, the buckling mechanism is the critical part that must be exactly determined by the designers and engineers. The buckling of the structure must be properly controlled to avoid failure in the structure when the load or force is applied to the structure.
(5)
According to the (Xinsheng, X et al. 2009), the buckling mechanism of the cylindrical shells under axial impact are divide into two categories which are the short-wave buckling and the long-short-wave buckling. The short-short-wave buckling is also known as dynamic local buckling and the long-wave buckling is known as global buckling.
Wang (2002) stated that the axisymmetric and non-axisymmetric buckling mechanism will depend on the axial impact velocity and the cylindrical shells thickness. Cylindrical shells that have very thin walls are easy to bulk when the axial compressive loads are subjected to the structure. Mandra and Mazzolani (1997) stated that the cylindrical shells are very sensitive to initial geometric imperfections.
2.3 Aluminum Alloy tube used in car body
The movement towards using light weight vehicles body represents a significant engineering challenge to the design and manufacturing sectors of the automotive industry. Nowadays, the automotive industry needs to consider aluminum alloy as a potential replacements for low-strength steel structural components. The change of the material used to replace the steel must not risk the structural integrity of the parts or sacrifice the energy absorption characteristics of the vehicle in a collision event. (Dong, K. et al. 1998)
Several automotive parts are being fabricated from the tube-stock and undergo various stages of forming that can consume a considerably degree of material ductility. According to the Oliveira and Michael (2005), the two main types of energy absorption structures used in automobiles are axial crush and s-rail structures. S-rails are used in side-rail support frames and may be stamped from sheet metal and welded together or fabricated from the tube stock using a pre-bending and hydro-forming operation. (Dong, K. et al.1998)
(6)
Bouchet and Jacquelin (2002), review about the value of impact force and the acceleration that must not exceed a certain impulse span. The objective is to reduce the disparities between the initial and the final level of deceleration and force by increasing the energy absorption capacities within the free crushing space available in the vehicle front part. Thus, the damage of the people and the structure can be minimized.
During a collision, the longitudinal girders are the one of the most important components for absorbing the energy. (Dong, K. et al. 1998)
Tubes based on steel and aluminum alloys collapse by plastic buckling in a concertina or diamond mode with the formation of a series of progressive plastic folds absorbing typically in range of 15 to 30kJ/kg in energy.
Wang (2002) state that the development of body parts and structural elements based on the aluminum alloy can cause some problems in the case of external stresses due to the shock or impact besides extreme environmental conditions. (Dong, K. et al. 1998)
The type of aluminum alloy that used in designing the car body space frame is an A6063 alloy. The aluminum A6063 alloy are the major precipitation strengthening alloys and have the merit of high extrusion efficiency compared with the other types of aluminum alloy. The behavior of the aluminum A6063 alloy used in the car body has been analyzed.
2.4 Aluminum A6063 Alloy used in car body Space Frame
Instead of replacement of the use of the steels with the aluminum alloys in saving the weight of a vehicle body, space frame has recently been developed and is use widely in designing the structure of a car body. The space frame use the aluminum alloys extruded in the form of thin tube that has the dimension approximately within 1 to 3 millimeters thickness with the same width, and complicated geometry to carry the load.