THE STUDY OF JOINING STRENGTH BASED ON DIFFERENTIAL JOINING
TECHNIQUE
MOHD NADZRIZAL BIN MOHAMAD GHAAZALI
Thesis submitted in fulfilment of the requirements
for award of the degree of
Bachelor of Mechanical Engineering with Automotive Engineering
Faculty of Mechanical Engineering
UNIVERSITI MALAYSIA PAHANG
JUNE 2013
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ABSTRACT
In this thesis, the objective is to study the joining strength based on different joining
technique. The focus objective joining strength in this thesis is the spot welding and the
adhesive bonding. This technique need to study the effectiveness of the spot welding and
adhesive bonding used to join the car body parts and strength of this method need to be
analyses. The method used in this thesis are used the five different material with
combination with specimen A and A, B and B. The joining used are spot weld and adhesive
been applied with the different thickness in 0.65 mm, 0.7 mm and 1.0 mm. the type
specimen used are SPCUD 35, SPC 440, PR SPCD, SPCD 440, and INR SPCD. To study
the strength of these method, tensile test have been conducted. The experiment been
conducted by load vs displacement and strength vs material. The experiment findings
showed those spot weld and adhesive bonding with same material shows different strength
and also different effect to the parent material. Spot weld bonding will affect the
microstructure of specimen and been harden the bonding of joining spot weld. When the
force applied higher than strength of the joining, the resistance area around nugget of spot
weld start to crack and failure happen at around the nugget itself not at nugget welding. The
strength of the spot weld is depending on the strength of material and thickness of material
applied to the joining. The strength of adhesive bonding is depending on type of adhesive
and surface roughness of the material itself. The shear test shows the adhesive bonding
have an average 5.43 MPa and spot weld joining is 6.79 MPa not much different Based on
experimental result, adhesive bonding is applicable for automotive body joining.
.
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ABSTRAK
Tujuan tesis ini adalah untuk mengkaji kekuatan penyambungan berdasarkan perbezaan
teknik penyambungan yang digunakan. Tujuannya adalah menfokuskan kekuatan
penyambungan dan penyambunganya adalah kimpalan spot dan ikatan adhesive. Teknik
ini memerlukan kajian terhadap keberkesanan kimpalan spot dan ikatan adhesive terhadap
penyambungan yang digunakan dalam pembuatan komponen badan kereta dan kekuatan
teknik ini harus dikaji. Method yang digunakan dalam tesis ini adalah dengan mengunakan
lima material berbeza dengan campuran specimen A dan A, B dan B. Penyambungan
kimpalan spot dan ikatan adhesive dilakukan dengan perbezaan berketebalan 0.65 mm, 0.7
mm dan 1.0 mm. Jenis- jenis spesimen yang digunakan adalah SPCUD 35, SPC 440, PR
SPCD, SPCD 440, dan INR SPCD. Untuk mengkaji kekuatan penyambungan ini,
eksperimen tensile test telah dijalankan. Eksperimen dijalankan mengikut daya melawan
pemanjangan dan kekuatn penyambungan melawan jenis material. Keputusan eksperimen
menunjukkan kimpalan spot dan ikatan adhesive dengan material yang sama menunjukkan
perbezaan kekuatan penyambungan dan juga kesan yang berbeza terhadap material yang
asal. Keputusan kimpalan spot menunjukkan kesan terhadap mikrostruktur specimen and
telah menjadi lebih keras terhadap ikatan penyambungan kimpalan spot. Apabila daya yang
dikenakan melebihi kekuatan penyambungan, kawasan yang bertindak melawan daya
sekitar diameter kimpalan spot mula menjadi retak dan kegagalan berlaku sekitar pada
diameter itu sendiri dan tidak kepada nugget kimpalan. Kekuatan penyambungan kimpalan
spot bergantung kepada kekuatan material dan ketebalan material yang dikenakan semasa
proses penyambungan dilaksanakan. Manakala ikatan adhesive bergantung kepada jenis-
jenis adhesive dan kekasaran permukaan material itu sendiri. Ujian ricih menunjukkan
ikatan adhesive boleh bertahan dalam sekitar 5.43 MPa dan kimpalan spot adalah sekitar
6.79 MPa tidak banyak perbezaannya dari segi nilai purata. Berdasarkan keputusan
eksperimen, ikatan adhesive boleh dilaksakan dalam penyambungan pembuatan automotif.
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TABLE OF CONTENTS
Page
TITLE i
SUPERVISOR’S DECLARATION ii
STUDENT DECLARATION iii
ACKNOWLEDGEMENTS iv
ABSTRACT v
ABSTRAK vi
TABLE OF CONTENTS vii
LIST OF TABLES ix
LIST OF FIGURES x
LIST OF SYMBOL xii
LIST OF ABBREVIATION xiii
CHAPTER 1 INTRODUCTION
1.1 Introduction 1
1.2 Background 1
1.3 Problem Statement 2
1.4 Objective 2
1.5 Scope 2
1.6 Project Flow Chart 3
CHAPTER 2 LITERATURE REVIEW
2.1 Introduction 4
2.2 Spot Welding 5
2.21 Heat Generation 82.3 Adhesive Bonding 9
2.3.1 Adhesive Experiment 122.3.2 Adhesive Application 14
2.4 Tensile Test 16
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2.4.1 The Tensile Testing 16
CHAPTER 3 METHODOLOGY
3.1 Introduction 17
3.2 Preparation Samples 18
3.3 Material Selection 18
3.4 Preparation of Test Joints 19
3.5 Procedure 19
3.5.1 Adhesives 203.5.2 Spot Welding 213.5.3 Tensile Test 22
CHAPTER 4 RESULT AND DISCUSSION
4.1 Introduction 23
4.2 Material Composition 23
4.3 Result of Shear Test 24
4.3.1 Adhesive Bonding Method 244.3.2 Spot Weld Method 34
4.4 Comparison between Different Joining Methods 44
CHAPTER 5 CONCLUSION AND RECOMMENDATION
5.1 Conclusion 49
5.2 Recommendation 50
REFERENCES 51
APPENDIX
A Cutting machine 53B Gantt chart for FYP 1 54C Gantt chart for FYP 2 55
ix
LIST OF TABLES
TABLE NO. PAGE
3.1 List material specimen for tensile test 18
3.2 Spot weld parameter 21
4.1 The Material Compositions of Test Materials, Wt-% 23
4.2 Shear strength properties of the Tail Gate INR specimen 25adhesive bonding
4.3 Shear strength properties of the Panel Roof specimen adhesive 26bonding
4.4 Shear strength properties of the Seat Cushion specimen adhesive 30bonding
4.5 Shear strength properties of the Panel RR Floor specimen 28adhesive bonding
4.6 Shear strength properties of the Tail Gate OTR specimen 29adhesive bonding
4.7 Shear strength properties of the Tail Gate INR specimen 36spot weld
4.8 Shear strength properties of the Panel Roof specimen 48spot weld
4.9 Shear strength properties of the Seat Cushion specimen 40spot weld
4.10 Shear strength properties of the Panel RR Floor specimen 42spot weld
4.11 Shear strength properties of the Tail Gate OTR specimen 44
4.12 The data of the maximum load, maximum displacement and 45shear strength in adhesive bonding .
4.13 The data of the maximum load, maximum displacement and 45shear strength between adhesive bonding and spot weld bonding.
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TABLE OF FIGURES
FIGURE NO. TITLE PAGE
1.1 Flow Chart of the project 3
2.1 Joining methods currently used in body assembly process 4
2.2 Resistance and tungsten inert gas spot weld comparison 5
2.3 Basic period of Spot welding 6
2.4 Spot weld time cycle 7
2.5 Samples of adhesive applications in car production. 10
2.6 Bonded joint loading: a) Tensile, b) Shear, c) Peel 11
2.7 Basic failure types of bonded joints 12
2.8 Basic failure types of bonded joints 12
2.9 Basic failure types of bonded joints 13
2.10 Shearing strength test results 13
2.11 Examples of adhesive and sealant applications in the body shop 15
3.1 Flow chart of the methodology 17
3.2 Tensile test size specimens 18
3.3 Standard Tests Join 19
3.4 Type of adhesive been used 20
3.5 Specimen adhesives being clamped 21
3.6 Tensile test machine 22
4.1 Tail Gate INR specimens after the shear test 24
4.2 Load vs Displacement for specimens Tail Gate INR for 25adhesive bonding.
4.3 Panel Roof specimens after the shear test 26
4.4 Load vs Displacement for specimens Panel Roof for adhesive 27bonding
4.5 Seat Cushion specimens after the shear test 28
4.6 Load vs Displacement for specimens Seat Cushion for 29adhesive bonding.
4.7 Panel RR Floor specimens after the shear test for adhesive 30bonding
4.8 Load vs Displacement for specimens Panel RR Floor for 31adhesive bonding.
4.9 Tail Gate OTR specimens after the shear test 32
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4.10 Load vs Displacement for specimens Tail Gate OTR for 33adhesive bonding.
4.11 Tail Gate INR specimens after the shear test for spot weld 35
4.12 Load vs Displacement for specimens Tail Gate INR for 35spot weld.
4.13 Panel Roof specimens after the shear test 37
4.14 Load vs Displacement for specimens Panel Roof for spot weld 36
4.15 Seat Cushion specimens after the shear test 39
4.16 Load vs Displacement for Seat Cushion specimens for 39spot weld.
4.17 Panel RR Floor specimens after the shear test 41
4.18 Load vs Displacement for specimens Panel RR Floor for 41spot weld.
4.19 Tail Gate OTR specimens after the shear test 43
4.20 Load vs Displacement for specimens Tail Gate OTR for 43spot weld.
4.21 Comparison maximum loads between spot weld and adhesive 46bonding
4.22 Comparison maximum displacement between spot weld 47and adhesive bonding
4.23 Comparison shear strength between spot weld and adhesive 48bonding
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LIST OF SYMBOLS
P - PressureF - ForceA - Area
σ - Stressτ - Shear StrengthH - HeatI - CurrentR - ResistanceT - ThicknessK - Heat Losses
xiii
LIST OF ABBREVIATION
TGI - Tail Gate Inner
TGO - Tail Gate Outer
PRR - Panel RR Floor
PR - Panel Roof
SC - Seat Cushion
OTR - Outer
INR - Inner
CHAPTER 1
INTRODUCTION
1.1 INTRODUCTION
In automotive industry, different joining techniques is being used in manufacture
the body parts of the car like adhesive bonding, spot welding, laser and others. Between the
different joining techniques used, the joining strength method between the spot welding and
adhesive bonding will be studied to be better method.
1.2 BACKGROUND
Adhesive bonding is used for various applications in the modern automotive
industry, ranging from flexible car body sealing to high-performance structural adhesives.
Adhesive types with specific properties are available for miscellaneous processing. The
requirements for adhesive bonds have increased due to the extended life of the car. In
adhesive processing, industrial health and environmental protection aspects have become
more and more important. Therefore, it is more difficult but nevertheless necessary to
determine requirements for the adhesives to be used in the future. In addition, the demand
for quality standards requiring better quality management is increasing. By using welding
there is often problem about joint different kinds of materials which effect outer surface
quality of welded parts. Complex shape or space which is hard to weld can take advantage
of adhesive bonding.
2
1.3 PROBLEM STATEMENT
In car manufacturing industry, spot welding is majorly used as a joining process to
join car body parts. In order to improve the joining method, adhesive bonding and a spot
weld need to be comparing to study the strength of the joining.
1.4 OBJECTIVE
The objective of the research is:
i. To compare the effectiveness of adhesive bonding and spot weld used to
join the car body parts
ii. To study the strength of these methods.
1.5 SCOPES
The application of adhesive for the joining of parts of different material grades and
thickness is commonly used in low volume automotive manufacturing. This study will
investigate the strength comparison of the adhesive bonding and spot welding by using the
same material specifications. To study the strength of the method used, the shear test be
used in the experiment.
3
1.6 PROJECT FLOW CHART
The Figure 1.1 below is the flow project that has been done in 2 semesters to finishthe project research about adhesive and spot weld joining.
Yes
Figure 1.1: Flow chart of the project
Project Start
Define Problem Statement, Objectiveand Scope of the Study
Literature Review
Methodology
Preparation of the workpieces
RunningExperiment
Slide Presentation forFYP 1
No
Data
Result Analysis
Discussion and ConclusionSlide Presentation
for FYP 2Project End
Searching the workpieces andExperiment Parameter
CHAPTER 2
LITERATURE REVIEW
2.1 INTRODUCTION
This chapter provides an overview of current research of the adhesive bonding and
spot welding included theoretical, experiment result, application and others. Some of the
information in this chapter can give extra information which can be useful while doing this
project.The pictures below are Figure 2.1 is joining methods currently used in body
assembly process in manufacturing industry (Larsoon J. K., 2012).
Figure 2.1: Joining methods currently used in body assembly process
Source: High Quality Welding Of Weight Optimized Passenger Car Bodies byLarsson J. K., 2012
5
2.2 SPOT WELD
Resistance welding is happen when current is caused to flow through electrode
tips and the separate pieces of metal to be joined together. The resistance of the base
metal to electrical current flow causes localized heating in the joint, and the weld is
made. The resistance spot weld is unique because the actual weld nugget is formed
internally in relation to the surface of the base metal. The nugget is shape formed from
the welding. The picture below is Figure 2.2 shows a resistance spot weld nugget
compared to a gas tungsten-arc spot weld (Miller, 2012).
Figure 2.2: Resistance and tungsten inert gas spot weld comparison
Source: Article Handbook for Resistance Spot Welding by Miller, 2012
Resistance spot welding is one of the oldest of the electric welding processes in
use by industry today, especially in the automotive industry. The weld is made by a
combination of heat, pressure, and time. As the name resistance welding implies, it is
the resistance of the material to be welded to current flow that causes a localized heating
in the part. The pressure exerted by the tongs and electrode tips, through which the
current flows, holds the parts to be welded in intimate contact before, during, and after
the welding current time cycle. The required amount of time current flows in the joint is
determined by material thickness and type, the amount of current flowing, and the
cross-sectional area of the welding tip contact surfaces (Cho Y., 2003).
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During the welding process, the amount of electric current is flow from the
electrodes to the work pieces. The shape and size of the form weld are controlled by the
size and contour of the electrode. This process is also depending to the welding time
where the timer controls by four different steps as shown in Figure 2.3 and Figure 2.4
(Jeffus L., 2011).
1. Squeeze time, or the time between the first application of electrode force
and the first application of welding current
2. Weld time or the actual time where the current is flow through the work
piece. The right or suitable amount of pressure was applied on the
workpiece is very important in order to obtain the quality of the weld.
3. Hold time, the period during which the electrode force is applied and the
welding current is shut off.
4. Off period, or the time during which the electrodes are not contacting the
work piece.
Figure 2.3: Basic period of spot welding.
Source: Welding principals and Applications Fourth Edition, pp. 678–681 by Larry
Jeffus, 2011.
7
Figure 2.4: Spot weld time cycle
Source: Welding principals and Applications Fourth Edition, pp. 678–681 by Larry
Jeffus, 1999.
When electric current is flow through electrode tips to the separate work pieces
of metal to be joined, the resistance of the base metal to electrical current flow causes
heat and the heat is limited to the area which the tip of the electrode and weld area
contacts. While the welding force is maintained, the heat is generating. In the holding
stage where the pressure is still maintained, the current is switched off and the nugget is
cooled under the pressure (Salem J. et al., 2012).
The major advantages of spot welding are high speed and adaptability for
automation in high-volume and/or high-rate production. Despite these advantages, RSW
suffers from a major problem of inconsistent quality from weld to weld. This problem
results from both the complexity of the basic previous term process next term as well as
from numerous sources of variability, noise, and errors. Any or all of these complicate
automation, reduce weld quality, demand over-welding like the production of more
welds than are structurally needed, if each were perfect, and drive up production costs.
(Jou M., 2003)
8
Resistance spot welding uses the surface resistance of the materials to be joined
to generate an intense localized heat under pressure with a short passage of a high
current. Use of coated sheet in vehicles for corrosion resistance has presented problems
related to the electrode life. The electrode life may get reduced to 50~500 welds before
maintenance (tip dressing) as against 3000~6000 welds in case of uncoated plain steels.
With introduction of HSLA steels, the need for reliability of weld quality has become
much more demanding. Suitable shop floor quality tests are vitally important. (Cho, Y.,
and Rhee, S. 2003)
Weld timers provide the ability to monitor each spot weld so that its peak
current level is within predetermined limits. Dynamic resistance principle measuring the
variation of resistance over time during the weld is also used to ensure a higher level of
guaranteed quality. A sophisticated dynamic resistance system may incorporate an
adaptive control feature that varies the weld settings within certain limits to achieve
correct weld quality. The system also includes a weld current stepper function linked to
the counting of welds executed. The parameter limits are established for the specific
application and programmed for control. With capability of microprocessor based
controls, the constant current system could easily be attained for ensuring weld quality
2.2.1 Heat Generation
A modification of Ohm’s Law may be made when watts and heat are considered
synonymous. When current is passed through a conductor the electrical resistance of the
conductor to current flow will cause heat to be generated. The basic formula for heat
generation may be stated in Equation 2.1 (Muller, 2012).
= (2.1)
H = HeatI2= Welding Current SquareR = Resistance
9
The secondary portion of a resistance spot welding circuit, including the parts to
be welded, is actually a series of resistances. The total additive value of this electrical
resistance affects the current output of the resistance spot welding machine and the heat
generation of the circuit. The key fact is, although current value is the same in all parts
of the electrical circuit, the resistance values may vary considerably at different points
in the circuit. The heat generated is directly proportional to the resistance at any point in
the circuit.
Previously, the formula for heat generation was used. With the addition of the
time element, the formula is completed as follows in Equation 2.2:
= (2.2)
H = HeatI2 = Current SquaredR = ResistanceT = TimeK = Heat Losses
Control of time is important. If the time element is too long, the base metal in
the joint may exceed the melting and possibly the boiling point of the material. This
could cause faulty welds due to gas porosity. There is also the possibility of expulsion
of molten metal from the weld joint, which could decrease the cross section of the joint
and weaken the weld. Shorter weld times also decrease the possibility of excessive heat
transfer in the base metal.
2.1.1 ADHESIVE BONDING
Adhesive bonding are used for various applications in the modern automotive
industry like Figure 2.5. Adhesive types with specific properties are available for
miscellaneous processing. The requirements for adhesive bonds have increased due to
the extended life of the car. In adhesive processing, industrial health and environmental
protection aspects have become more and more important. Therefore, it is more difficult
10
but nevertheless necessary to determine requirements for the adhesives to be used in the
future. In addition, the demand for quality standards requiring better quality
management is increasing (Cordes E.H., 2003).
Figure 2.5: Samples of adhesive applications in car production.
Sources: Adhesives in the Automotive Industry by Cordes E. H., 2003.
During car-body design and production is not nowadays just too convectional
jointing technologies for stampings. Important role for jointing individual car-body
parts plays bonding technology is possible application of adhesives. These days using
adhesives do not serve only for sealing function, anti-acoustic or anti-vibration barriers
but are also using like structural jointing types which into great extent influence strength
and stiffness of car-body and thus its safeness and whole comfort.
For car-body design are up to now using the thinnest sheets which are
subsequently jointed mainly by welding. However nowadays there is still increasing
tendency to use just bonded joints due to their advantages which represents for jointing
of car-body parts. Properly design of bonded joints can in many cases both get out
11
problems with welding and also give the whole construction other profitable properties.
Structural bonded joints taken place in automotive industry in many variants both from
the design point of view and from the functional loading point of view. Precondition for
fine strength and sufficient bonded joints capacity represents mainly suitable joint
design.
Bonded joints are known for their very high shearing strength. Tensile strength
is much lower and the worse properties are given under peel loading like Figure 2.6
Principles about suitable using of bonded joint are given firstly by character of used
adhesive and also by requirement to reduce or eventually minimize tensile and peel
loading .If there is not possibility to reduce these factors and is necessary to increase
joint safety, bonding is combines with other jointing technologies. In many cases are
bonded joints used in combination with spot welding example door trims (Kolnerove M.
et al., 2010).
a) b) c)
Figure 2.6: Bonded joint loading: a) Tensile, b) Shear, c) Peel.
Source: Kolnerove M., Doubek P., Solfronk P. and Sobotka J., 2010. Strength ofAdhesive Bonding Joints for Classical and Progressive Materials Used ForCar-Body Design. Journal of Materials Processing Technology, 93 (3): 102
12
2.3.1 Adhesive Experiment
For evaluation bonded joint quality is another possible criterion to evaluate
bonded joint failure type according CSN ISO 10365 like Figure 2.7. Basic failure types
are shown with course of peeling test in Figure 2.8 (Kolnerove M. et al., 2010).
Figure 2.7: Basic failure types of bonded joints.
Source: Strength of Adhesive Bonding Joints for Classical and Progressive Materials
Used For Car-Body Design by Kolnerove M. et al., 2010.
Figure 2.8: Peeling Test
Source: Strength of Adhesive Bonding Joints for Classical and Progressive Materials
Used for Car-Body Design by Kolnerove M. et al., 2010
CF – CohesionType
SCF – SpecialCohesion
type
AF – AdhesionType
13
Figure 2.9: Peeling strength test results.
Source: Strength of Adhesive Bonding Joints for ClassicalandProgressive Materials
Used For Car-Body Design by Kolnerove M. et al., 2010
Figure 2.10: Shearing strength test results.
Source: Strength of Adhesive Bonding Joints For Classical And Progressive Materials
Used for Car-Body Design byKolnerove M. et al., 2010
14
Measured results proved presumptions about lower strength of bonded joints
from aluminium alloys wit comparison to steel sheets both under shearing loading like
Figure 2.9 and also for peel test like Figure 2.10. Such reality is also because due to
lower mechanical properties for tested aluminium alloy, however measured values
fulfill parameters of bonded joints utility properties. It is really necessary to remind that
bonded joints test quality results to a great extent depend on many parameters which
influence final values like example. Amount and type of used lubricants, type of used
substrate and its surface morphology. With respect to these and many others influences
can be stated that for each combination of lubricant, substrate and adhesive have to be
tested. Great number of parameters makes testing of bonded joints quality very difficult
and there is necessity to carry out another testing and deepening knowledge about
individual factors influence and their combination onto bonded joints properties with
respect to specific requirements from automotive industry.
2.3.2 Adhesive Applications
In this part, adhesive bonding and sealing in automobile production are
subdivided schematically into two ranges of application: mechanical parts production,
and the body shop. Depending on the variety of applications, adhesives must satisfy a
wide range of requirements. Generally, the bond strength adhesive ability must perform
under severe conditions for the life of the car (Cordes E.H, 2003).
Further requirements depend on:
a) Function of the material (e.g. are spot-weld sealants): good corrosion protection,
weldability, or chlorine emitted to cause corrosion when over baked, good
adhesion on the substrates
b) Processing technique: manual or automatic application, bonding at the assembly
line or at a separate working site
c) Specific material characteristics like moisture and or hot-curing adhesive: curing
time, stability in storage, flexibility at low temperatures, hydrolytic stability,
aging resistance, adhesion properties
