Optimization of FSW Process Parameter to Achieve Maximum Tensile Strength of Aluminum Alloy

International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395 -0056
Volume: 03 Issue: 02 | Feb-2016 www.irjet.net p-ISSN: 2395-0072
© 2016, IRJET | Impact Factor value: 4.45 | ISO 9001:2008 Certified Journal | Page 936
OPTIMIZATION OF FSW PROCESS PARAMETER TO ACHIEVE MAXIMUM
TENSILE STRENGTH OF ALUMINUM ALLOY AA6061
Ram D. Shinde 1, Mahendra G. Rathi 2
1Department of Mechanical Engineering, Government College of Engineering,
Aurangabad - 431 005, Maharashtra (India)
2Department of Mechanical Engineering, Government College of Engineering,
Aurangabad - 431 005, Maharashtra (India)
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Abstracts - This paper reports on an examination of the
effect and optimization of welding parameters on the
tensile shear strength in Friction Stir Welding process. The
experimental readings were conducted under varying Tool
Rotation Speed (rpm), Tool Traveling Speed (mm/min),
and Tool Tilt Angle (degree). The settings of welding
parameters were determined by using the Taguchi
experimental design method. Experiments were conducted
on AA6061 Aluminium alloy in a Vertical Machining
Machine Centre. The output factors are measured in UTM.
Results show strong relation and robust comparison
between the weldment strength and process parameters.
Hence FSW process variable data base is to be developed
for wide variety of metals and alloys for selection of
optimum process parameters for efficient weld. The level
of importance of the welding parameters on the tensile
shear strength is determined by using analysis of variance
(ANOVA). The optimum welding parameter combination
was found by using the analysis of signal-to-noise (S/N)
ratio. The validation tests indicated that it is possible to
increase tensile shear strength significantly by using the
Taguchi method. The experimental results confirmed the
validity of the used Taguchi method for enhancing the
welding performance and improving the welding
parameters in the Linear Friction Stir welding process.
Key Words: Tool rotation and travel speed and tool tilt
angle. ANOVA, S/N ratio, OA.
1. INTRODUCTION
Friction stir welding (FSW) is an advanced welding
process commonly known as a solid state welding process.
This opens up whole new areas in welding technology. It is
mainly appropriate for the welding of high strength alloys.
The process uses a revolving, non-consumable tool, similar
to a taper reamer, to produce frictional heat in the
workpiece. By pressing this tool into contact with a seam
to be welded, the base metal heats up and once it material
is literally stirred together forming a weld without melting.
These welds require low energy input and are without the
use of filler materials and distortion. Initially developed for
non-ferrous materials such as aluminium, by reaches
about 80% of its melting point it becomes soft and deforms
easily. By protection the tool rotating and moving it along
the seam to be joined, the softened using suitable tool
materials the use of the method has been extended to
harder and higher melting point materials such as steels
titanium alloys, copper and High Stainless steel (HSS)
Material. This paper will concentrate on improvements for
the friction stir welding of aluminium alloys.
2. SELECTION OF MATERIAL
The base material (BM) used in this investigation is
aluminum alloy AA6061. Chemical composition of the
material and mechanical properties is given in Table 1, 2
respectively.
Table – 1: Percentage of chemical composition of
aluminum alloy -AA6061
Si Fe Cu Zn Ti Mn Mg Cr Other Al
0.4-
0.8
0.7
0.15-
0.4
0.25 0.15
0.2-
0.8
0.8-
1.2
0.15-
0.35
0.05 98.70
Table – 2: Mechanical properties of base metal –AA6061
Material
Yield
Strength
(MPa)
Ultimate
Tensile
Strength (MPa)
Elongation
( %)
Hardness
(0.5Kg)
Base
Metal
235 283 26.4 105

2.1 Cutting aluminium alloy plate
First of all eighteen pieces having size
200x125x6mm of AA6061 material are prepared for
friction stir welding purpose. For this firstly AA6061
material blank is pressed in a press to make it straight and
stress free. After that from this material blank, eighteen
plates of size 200x125x6mm are cut by power hacksaw
and milling machine. Square butt joint configuration, as
shown in figure 1 has been prepared to fabricate FSW
joints.
Particular’s Values
Work Piece Material Al 6061
Work piece Dimensions 200 (L) x 125 (W) x 6 (H) mm
Figure – 1: Dimensions for the work piece
2.2 Design of Tool
Tool specification detail given in table and shown
in drawing as given below:
Figure – 2: Square tool pin profile
Table – 3: Tool specification
Particular’s Index Value
Total Tool Length L1 75 mm
Head of Tool L2 50 mm
Shoulder Length L3 25 mm
Pin Height L4 5.5 mm
Pin Length L5 5 mm
Pin Width L6 5 mm
Dia. of Tool Head D 15 mm
Shoulder Diameter D 18 mm
Tool Material High Speed Steel (HSS)
Hardness for Shank, Shoulder and Pin
Profile
60-62 HRC
2.3 Design of Fixture
Fixture is a job holding device which is mainly
made up of MS steel plate. A fixture is something used to
consistently test some item or device. We used a MS steel
plate fixture for the process of friction stir welding. Joining
a suitable sheet as required on the base of fixture, the
sheet should have the required strength to withstand with
operations. There may be many nuts on the fixture
according to the requirement to hold the work piece. But
in the experiment we used six nuts and bolt to hold the job
in the fixture.
Table give detail dimensions specification required for
design fixture.
Table – 4: Dimensions of Fixture
Sr. No. Fixture Part Name Dimensions
1 Fixture Base Plate 300(L) x 200(W) x 10 (H) mm
2 Clamping Plate 270(L) x 40 (W) x 6 (H) mm
3 M18 (Nut Bolt) 2 Nos.
4 M15 (Nut Bolt) 4 Nos.
Photograph – 1: Special design fixtures

3. TENSILE TESTING OF THE WELDED SPECIMEN
The welded joints are sliced using power hacksaw
and then machined to the required dimensions to prepare
tensile specimens as shown in figure 4. American Society
for Testing of Materials (ASTM E8M-04) guidelines is
followed for preparing the test specimens. Tensile test has
been carried out in 100 ton, electro-mechanical controlled
Universal Testing Machine at room temperature. The
specimen is loaded at the rate of 1.5 KN/min as per ASTM
specifications, so that tensile specimen undergoes
deformation. The specimen finally fails after necking and
the load versus displacement has been recorded. The
ultimate tensile strength and percentage of elongation and
joint efficiency have been evaluated.
Figu
re – 3: Dimensions of tensile specimen according to ASME
E8M-04
Photograph – 3: Specimens in UTM
(Material AA606 – after test)
Photograph – 4: Typical un-notch (Smooth) tensile tested
specimens
Table – 5: Tensile strength testing result of welded specimen (Experimental Reading)
Sr.
No.
Type
Width In
MM
Thickness
In Mm
Area
In MM2
Gauge
Length In
MM
Final
Length In
MM
Ultimate Load
In N
U. T. S. In
N/mm2
% Elongation
Joint Efficiency In
%
1 A 13.08 6.04 78.91 25.00 27.23 9640.00 122.17 8.92 72.62
2 B 13.40 6.23 83.44 25.00 27.20 8800.00 105.46 8.80 63.10
3 C 13.05 6.10 79.61 25.00 26.25 5560.00 69.84 5.00 41.37
4 D 14.40 6.06 87.25 25.00 27.00 8800.00 100.86 8.00 60.12
5 E 13.80 6.04 83.36 25.00 27.50 10080.00 120.92 10.00 72.02
6 F 13.05 5.86 76.48 25.00 27.35 8400.00 109.84 9.40 65.48
7 G 13.80 5.78 79.68 25.00 27.05 10520.00 132.03 8.20 78.57
8 H 13.15 6.10 80.14 25.00 27.00 8320.00 103.82 8.00 61.61
9 I 12.85 5.89 75.70 25.00 27.15 8000.00 105.68 8.60 62.20

The welding experiments were carried out on the
FSW machine by following the Taguchi designed matrix L9
in random order, as presented in Table 5 Mechanical
properties like tensile strength, yield strength and
percentage elongation were found out for the welded
plates and the results are presented in Table 5. Each of the
experimental results presented in Table 5 is an average of
at least of two readings.
4. TAGUCHI ORTHOGONAL ARRAY
If there is an experiment having 3 factors which
have three values, then total number of experiment is 27.
Then results of all experiment will give 100 accurate
results. In comparison to above method the Taguchi
orthogonal array make list of nine experiments in a
particular order which cover all factors. Those nine
experiments will give 99.96% accurate result. By using this
method number of experiments reduced to 9 instead of 27
with almost same accuracy.
The three factors used in this experiment are the
rotating speed, tool tilt angle and travel speed. The factors
and the levels of the process parameters are presented in
Table 6 and these parameters are taken based on the trials
to weld the FSW of steels. The experiment’s notation is
also included in the L9 orthogonal array which results in
an additional column, in order to represent the
parameters, as presented in Table 7.
Table – 6: FSW process parameter / Factor and levels to
be taken
Symbol
Welding Parameter
/ Factors
Unit Level 1 Level 2
Level
3
A Tool Rotation Speed rpm 1000 1500 2000
B Tool Travel Speed mm/min 30 35 40
C Tilt Angle
degree
(°)
0° 1° 2°
Table – 8: The Input parameter of L9 orthogonal array
S
r.
N
o.
Experimen
t’s
Notation
Friction Stir Welding Parameter Level
Tool Rotation
Speed
In rpm
(A)
Tool Travel
Speed
In mm/min
(B)
Tilt Angle
In degree
(C)
1 A 1000 30 0
2 B 1000 35 1
3 C 1000 40 2
4 D 1500 30 1
5 E 1500 35 2
6 F 1500 40 0
7 G 2000 30 2
8 H 2000 35 0
9 I 2000 40 1
Table – 9: Response table for single to noise ratio (S/N
ratio) and mean
E
x.
N
o.
Tool
Rotation
al Speed
(rpm)
Tool
Travers
e Speed
(mm/mi
n)
Tilt
Angle
(Degr
ee)
UTS
(N/m
m2)
Joint
Efficie
ncy In
%
S/N
Ratio
Mean
A 1000 30 0
122.1
7
72.62 38.91 97.31
B 1000 35 1
105.4
6
63.10 37.69 84.55
C 1000 40 2 69.84 41.37 34.03 55.44
D 1500 30 1
100.8
6
60.12 37.27 80.56
E 1500 35 2
120.9
2
72.02 38.84 96.51
F 1500 40 0
109.8
4
65.48 38.02 87.74
G 2000 30 2
132.0
3
78.57 39.60
105.2
9
H 2000 35 0
103.8
2
61.61 37.49 82.56
I 2000 40 1
105.6
8
62.20 37.57 83.35
In these tests, nine different welding parameter
combinations were used. Therefore, the effect of each
welding parameter on the weld strength cannot be clearly
understood from the result of Table 9. Using MINITAB
statistical software was used to explain the welding
parameter effect [23]. From the results of Table 9,
diagrams were drawn to display the welding parameters
effects on the weld strength.
Chart – 1: Effect of FSW parameter on tensile strength
The effect of the friction stir welding parameters on the
tensile test results for the design of the experiments are
shown in Chart 1. As shown in Table 9, these tensile test
results and the corresponding S/N ratio were calculated
with Eq. (1).
…………………. (1)

5. ANALYSIS OF VARIANCE (ANOVA)
The relative importance among the welding parameters on
weld strength is needed to be determined so that optimal
combinations of the parameter levels can be assessed
accurately. This can be achieved by using the analysis of
variance. The purpose of the analysis of variance (ANOVA)
is to investigate the importance of the welding parameters
on the quality characteristic [13].
Table – 10: Analysis of variance (ANVAO) for tensile
strength (SN Ratios)
Source DF
Seq.
SS
Adj
SS
Adj
MS
F P
Percentage of
Contribution
Tool
Rotational
Speed
(RPM)
2 3.207 3.207 1.604 0.340 0.747 15.929
Tool
Travel
Speed
(MM/min)
2 6.664 6.664 3.332 0.710 0.586 33.099
Tilt Angle
( Degree )
2 0.812 0.812 0.406 0.090 0.921 4.031
Error 2 9.451 9.451 4.726 - - 46.941
Total 8 20.134 - - - - 100.000
Table – 11: Analysis of variance (ANOVA) for tensile
strength (Means)
Source DF Seq. SS Adj SS Adj MS F P
Percentage
of
Contribution
Tool
Rotational
Speed
(RPM)
2 222.630 222.630 111.310 0.290 0.775 14.029
Tool
Travel
Speed
(MM/min)
2 537.490 537.490 263.750 0.700 0.588 33.870
Tilt Angle
( Degree )
2 60.710 61.710 30.360 0.080 0.927 3.826
Error 2 766.090 766.090 383.040 - - 48.275
Total 8 1586.920 - - - - 100.000
Note: DF- Degree of Freedom, Seq. SS – Sequential Sum of
Square, Adj SS –Adjusted Sum of Squares, Adj MS –
Adjusted Mean Square, F test of hypothesis or Fisher ratio,
P value of hypothesis
Chart – 2: ANOVA analysis for optimum tool rotational
speed and tilt angle on ultimate tensile strength.
Chart – 3: ANOVA analysis for optimum tool rotational
speed and tool travel speed travel on ultimate strength.
Chart – 4: ANOVA analysis for optimum tilt angle and tool
travel speed on ultimate tensile strength.

The purpose of ANOVA is to determine which welding
parameters highly affect the quality feature statistically
[27, 30]. According to the results that are shown in Table 9,
the Charts show the influence of the welding parameters
on the tensile strength of Al 6061 sheet joined by FSW. The
Charts are shown in Chart 2, 3. All of the dark green zones
in the Charts show the maximum ultimate tensile strength.
Chart shows ANOVA analyses for the optimum tool
rotation speed and tilt angle on the ultimate tensile
strength. For the relation between the tool rotation speed
and tilt angle the maximum UTS was confirmed by welding
parameters of 2000 rpm and 2˚ as shown in Chart 2. The
relation between tool rotation speed, tool traverse speed
and tilt angle in Chart 3 and 4 similar trends were
observed as shown in Chart 2.
6. RESULTS OF TESTING
From the experimental results (tensile strength and
MINITAB software), it is found the joint fabrication
Friction Stir Welding 6061 aluminium alloy exhibited
superior tensile properties by using parameter as tool
rotational speed, tool travel speed and tool tilt angle. The
possible cause for the effects of different welding
parameters on tensile strength is interpreted and
presented as follows.
6.1 Mean and signal to noise ratio
The Mean and signal to noise ratio are the two
effects which influence the response of the factors. The
influencing level of each selected welding parameter can
be identified. The tensile strength of the FSW weld is taken
as the output characteristic. The response table for the S/N
ratio shows that the tool tilt angle ranks first in the
contribution of good joint strength, while travel speed and
rotation speed take the second and third ranks. The same
trend has been observed in the response table of the mean
which is presented in Tables 12 and 13 respectively. The
responses for the plot of the S/N ratio and Mean are shown
in Fig.4. The tensile strength is estimated to be the
maximum at 2000 rpm rotation speed, 2° tool tilt angle
and 8 mm/min travel feed; which is optimal from the plots
obtained.
Table – 12: Response table for signal to noise ratio (S/N
Ratio)
Level
Tool rotational
speed
Tool travel
speed
Tool tilt angle
1 36.88 38.60 38.14
2 38.04 38.01 37.51
3 38.23 36.55 37.49
Delta 1.35 2.05 0.65
Rank 2 1 3
The Optional setting parameters based on mean A3 B1 C1
Table – 13: Response table for mean
Level
Tool rotational
speed
Tool travel
speed
Tool tilt angle
1 79.09 94.40 89.26
2 88.21 87.82 82.90
3 90.65 75.74 85.79
Delta 11.56 18.86 6.35
Rank 2 1 3
The Optional setting parameters based on mean A3 B1 C1
6.2 Percentage of contribution
The percentage of contribution is the portion of
the total variation observed in the experiment attributed
to each significant factors and/or interaction which is
reflected. The percentage of contribution is a function of
the sum of squares for each significant item; it indicates
the relative power of a factor to reduce the variation. The
percentage of contribution of the rotational speed, welding
speed and axial force for all responses are shown in Chart
5 (a) (b).
Chart - 5(a): Percentage contribution of factors S/N Ratio.

Chart -5(b): Percentage contribution of factors Mean
Ratio.
6.3 Effects of process parameter on tensile
strength (Base on Experimental Data Calculation)
From Table 9 as explain below:
Chart – 6: Effect of rotational speed on tensile strength
Chart – 7: Effect of tool travel speed on tensile strength
Chart – 8: Effect of tool tilt angle on tensile strength
In order to study the welding process parameters effects
on tensile strength of the joints, tool which produced
better welds was used.
Figure 6 shows the effect of tool rotational speed
on tensile strength of the joints. The maximum UTS of
about 132.03 was obtained at the tool rotational speed of
2000 rpm. With the rotational speed of 1000rpm, the
wormhole phenomenon at the retreating side of the weld
due to insufficient frictional heat generation and
insufficient matrix transportation. The formation of this
defect may be attributed to excessive turbulence of the
weld caused by high tool rotational speed. Therefore, with
the rotational speed of 2000 rpm, a just sufficient amount
of frictional heat is generated which with proper
turbulence of the weld results in the highest tensile
strength.
The effect of work tool travel speed on tensile
strength of the joints is not significant as shown in Chart 7.
This is more obvious especially at speeds higher than 40
mm/min. When the travel speed is increased from 30 to 40
mm/min., the tensile strength decreases with a sharp
slope compared to the speed between 35 and 40 mm/min.
The excessive heat input per unit length of the weld at
higher travel speeds and inadequate flow of the matrix
which may cause tunnel defect factors contributing to
lower strength of the higher tool travel speeds.
The influence of tool tilt angle on tensile strength
of the welds is illustrated in Chart 8. Tilt angle affects the
vertical and horizontal flow of the weld material tilt angle
may cause tunnel and crack welds. At 0° tilt angle, the
insufficient vertical and horizontal flow of the weld
material may cause these defects that reduce the strength
tilt angle, improves the flow characteristics of the material
and hence, tool movement forges the weld material better
to fill the defects and consequently increases the weld
strength. Tensile strength of the welds increased when tilt
angle was changed form 0˚ or 2˚.
7. CONFIRMATION TEST
The final step is verifying the improvement in responses
by conducting experiments using optimal conditions.
Three confirmation experiments were conducted at the
optimum setting of process parameters. The rotational
speed, welding speed and axial force were set at level 3
and the average tensile strength of friction stir welded
6061 aluminium alloy was found to be 131.36N/mm2, as
shown in Table 14, which was within the confidence
interval of the predicted optimal of tensile strength.

Table – 14: Confirmation experiment for Tensile strength
Sr.
No.
Tool
Rotational
Speed in
(rpm)
Tool
Travel
Speed in
(mm/min)
Tilt
Angle
in (˚)
Ultimate
Tensile
Strength
in
(N/mm2)
Actual
UTS in
(N/mm2)
Predicted
UTS in
(N/mm2)
1 2000 30 2˚ 134.86
135.50 132.032 2000 30 2˚ 135.57
3 2000 30 2˚ 136.07
8. CONCLUSIONS
From the present experimental investigation the following
conclusions are derived:
 Base metal AA 6061 was found to exhibit the best
characteristics for Friction Stir Welding.
 Tool material (HSS) found to withstand for 6082-
T6 base metal without tool breakage.
 The tool pin geometry (square pin shape) had a
significant effect on weld appearance and tensile
strength.
 The Taguchi method has been used to optimize
the welding parameters of friction stir welding to
weld a 6mm plate of IS: 3039.
 Using Minitab software and counter plot to
maximum the Ultimate Tensile Strength of
welding joints, for the given set of parameters, the
optimum parameters were obtained as:
o Optimum tool rotational speed:
2000rev/min.
o Optimum tool travel speed (Transvers
speed): 30 mm/min.
o Optimum tilt angle: 2˚ Degree.
 The prediction of the Taguchi design approach
was in good agreement with the experimental
result.
 The L9 Taguchi orthogonal designed experiments
of FSP on ASNCs were successfully conducted and
the process parameters have a critical role in the
quality of the obtained composites
ACKNOWLEDGEMENT
I acknowledge my sincere thanks to M/s Govind
INDUSTRIES and M/s OM INDUSTRIES Tiny Industries Co-
Op., Industrial Estate Ltd., MIDC Area, Chikalthana,
Aurangabad, also MATTEST Laboratory MIDC Waluj Area,
Aurangabad who gave me an opportunity to carry
experimental work in his industry and doing Test in his
laboratory for preparing test report.Cordial thanks, to my
mechanical engineering department’s professor those who
helped me.
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Optimization of FSW Process Parameter to Achieve Maximum Tensile Strength of Aluminum Alloy

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