Optimization of friction stir welding parameters for magnesium alloy AZ91D using Taguchi design
Friction stir welding of magnesium alloy, AZ91D casting materials has been welded and their tensile strength is investigated. Evaluation of FSW process parameters such as tool rotational speed, welding speed and axial force on tensile strength was carried out using Taguchi parametric design and o...
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Senthilraja, R. Naveen Sait, A. 2018-06-14T08:19:08Z 2018-06-14T08:19:08Z 2015 Optimization of friction stir welding parameters for magnesium alloy AZ91D using Taguchi design / R. Senthilraja, A. Naveen Sait // Фізико-хімічна механіка матеріалів. — 2015. — Т. 51, № 2. — С. 36-41. — Бібліогр.: 8 назв. — англ. 0430-6252 https://nasplib.isofts.kiev.ua/handle/123456789/134757 Friction stir welding of magnesium alloy, AZ91D casting materials has been welded and their tensile strength is investigated. Evaluation of FSW process parameters such as tool rotational speed, welding speed and axial force on tensile strength was carried out using Taguchi parametric design and optimization approach. Optimized process parameters are established using ANOVA technique and the percentage contribution of process parameters are also determined. Досліджували зварювання тертям з перемішуванням (FSW) магнієвих сплавів, литих матеріалів AZ91D та вивчали їх границю міцності на розрив. Оцінювали параметри процесу FSW, а саме: швидкість обертання інструменту, швидкість зварювання та дію осьового навантаження на границю міцності на розрив, використовуючи пристрій Тагучі, та оптимізаційний підхід. Оптимізацію параметрів проводили за методикою ANOVA та із врахуванням процентного внеску параметрів процесу. Исследовали сварку трением с перемешиванием (FSW) магниевых сплавов, литых материалов AZ91D и изучали их предел прочности на разрыв. Оценивали параметры процесса FSW, а именно: скорость вращения инструмента, скорость сварки и действие осевой нагрузки на предел прочности на разрыв, используя установку Тагучи, и оптимизационный подход. Оптимизацию параметров проводили по методике ANOVA и с учетом процентного взноса параметров процесса. en Фізико-механічний інститут ім. Г.В. Карпенка НАН України Фізико-хімічна механіка матеріалів Optimization of friction stir welding parameters for magnesium alloy AZ91D using Taguchi design Оптимізація параметрів зварювання під час тертя з перемішуванням магнієвого сплаву AZ91D за допомогою методу Тагучі Оптимизация параметров сварки при трении с перемешиванием магниевого сплава AZ91D с помощью метода Тагучи Article published earlier |
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Digital Library of Periodicals of National Academy of Sciences of Ukraine |
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| title |
Optimization of friction stir welding parameters for magnesium alloy AZ91D using Taguchi design |
| spellingShingle |
Optimization of friction stir welding parameters for magnesium alloy AZ91D using Taguchi design Senthilraja, R. Naveen Sait, A. |
| title_short |
Optimization of friction stir welding parameters for magnesium alloy AZ91D using Taguchi design |
| title_full |
Optimization of friction stir welding parameters for magnesium alloy AZ91D using Taguchi design |
| title_fullStr |
Optimization of friction stir welding parameters for magnesium alloy AZ91D using Taguchi design |
| title_full_unstemmed |
Optimization of friction stir welding parameters for magnesium alloy AZ91D using Taguchi design |
| title_sort |
optimization of friction stir welding parameters for magnesium alloy az91d using taguchi design |
| author |
Senthilraja, R. Naveen Sait, A. |
| author_facet |
Senthilraja, R. Naveen Sait, A. |
| publishDate |
2015 |
| language |
English |
| container_title |
Фізико-хімічна механіка матеріалів |
| publisher |
Фізико-механічний інститут ім. Г.В. Карпенка НАН України |
| format |
Article |
| title_alt |
Оптимізація параметрів зварювання під час тертя з перемішуванням магнієвого сплаву AZ91D за допомогою методу Тагучі Оптимизация параметров сварки при трении с перемешиванием магниевого сплава AZ91D с помощью метода Тагучи |
| description |
Friction stir welding of magnesium alloy, AZ91D casting materials has been welded and
their tensile strength is investigated. Evaluation of FSW process parameters such as tool
rotational speed, welding speed and axial force on tensile strength was carried out using
Taguchi parametric design and optimization approach. Optimized process parameters are
established using ANOVA technique and the percentage contribution of process
parameters are also determined.
Досліджували зварювання тертям з перемішуванням (FSW) магнієвих
сплавів, литих матеріалів AZ91D та вивчали їх границю міцності на розрив. Оцінювали параметри процесу FSW, а саме: швидкість обертання інструменту, швидкість зварювання та дію осьового навантаження на границю міцності на розрив, використовуючи пристрій Тагучі, та оптимізаційний підхід. Оптимізацію параметрів проводили за методикою ANOVA та із врахуванням процентного внеску параметрів процесу.
Исследовали сварку трением с перемешиванием (FSW) магниевых сплавов, литых материалов AZ91D и изучали их предел прочности на разрыв. Оценивали параметры процесса FSW, а именно: скорость вращения инструмента, скорость сварки и действие осевой нагрузки на предел прочности на разрыв, используя установку Тагучи, и оптимизационный подход. Оптимизацию параметров проводили по методике ANOVA и с учетом процентного взноса параметров процесса.
|
| issn |
0430-6252 |
| url |
https://nasplib.isofts.kiev.ua/handle/123456789/134757 |
| citation_txt |
Optimization of friction stir welding parameters for magnesium alloy AZ91D using Taguchi design / R. Senthilraja, A. Naveen Sait // Фізико-хімічна механіка матеріалів. — 2015. — Т. 51, № 2. — С. 36-41. — Бібліогр.: 8 назв. — англ. |
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2025-11-25T23:53:50Z |
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| fulltext |
36
Ô³çèêî-õ³ì³÷íà ìåõàí³êà ìàòåð³àë³â. – 2015. – ¹ 2. – Physicochemical Mechanics of Materials
OPTIMIZATION OF FRICTION STIR WELDING PARAMETERS
FOR MAGNESIUM ALLOY AZ91D USING TAGUCHI DESIGN
R. SENTHILRAJA 1, A. NAVEEN SAIT 2
1 Department of Mechanical Engineering, Jayaram College of Engineering & Technology,
Tiruchirappalli, India;
2 Department of Mechanical Engineering, Chendhuran College of Engineering & Technology,
Pudukkottai, India
Friction stir welding of magnesium alloy, AZ91D casting materials has been welded and
their tensile strength is investigated. Evaluation of FSW process parameters such as tool
rotational speed, welding speed and axial force on tensile strength was carried out using
Taguchi parametric design and optimization approach. Optimized process parameters are
established using ANOVA technique and the percentage contribution of process
parameters are also determined.
Keywords: magnesium alloy, Taguchi, ANOVA, friction stir welding, tensile strength.
Friction stir welding (FSW) is a metal joining process in which heat is generated
by friction between the tool and the workpiece to produce solid state welding [1]. A
recent report reveals that the tensile strength of aluminium and magnesium materials at
the joints is lower than that of the base material except during elongation. Hence
determination of the optimum values of welding parameters such as welding speed,
rotational speed helps in increasing the tensile strength at the weld joints [2]. Won-Bae
Lee et al. analyzed the joint characteristics of friction stir welded AZ91D magnesium
alloy of 4 mm thickness plate. The microstructure analysis reveals that the grain size
decreases with increase in welding speed at the stir zone [3]. An attempt was made by
Elangovan and Balasubramanian to understand the influences of rotational speed and
pin profile of the tool on the friction stir processed (FSP) zone formation in AA2219
aluminium alloy [4]. The AZ31B magnesium alloy was successfully joined without
any macro level defects by using this process. The optimum tool rotational speed,
welding speed, and axial force are 1600 rpm, 0.67 m/s and 3 kN respectively. It is also
reported that the tensile properties are higher when compared with other joining process
[5]. Many researchers evaluated the tensile strength to determine the optimum welding
parameters, namely rotational speed and welding speed. However, the axial force was
seldom considered while determining the optimum process parameters. Taguchi tech-
nique and ANOVA technique are considered to be a robust effective tool for carrying
out experimental work and further processing the experimental data for optimization [6].
The objective of this work is to establish the optimum friction stir welding
parameters of AZ91D magnesium alloy. The main parameters to be considered for
optimization are rotational speed, welding speed and axial force. Optimization of
process parameters is done with the help of ANOVA technique.
Experimental details. Materials and processes. The experiments were carried
out using 6 mm thick plates of AZ91D magnesium alloys. The chemical composition
of AZ91D Mg alloy (mass.%): 9.1 Al; 0.0027 Ni; 0.001 Cu; 0.65 Zn; Bal. Mg and mecha-
nical properties: tensile strength – 293 MPa; yield strength – 222.7 MPa; elongation – 13%.
Corresponding author: A. NAVEEN SAIT, e-mail: naveensait@yahoo.co.in
37
Fig. 1. Friction stir welding tool.
Welding parameters such as tool rota-
tional speed, traverse speed and axial force
play a major role in deciding the weld qua-
lity. Experiments were carried out to join
the AZ91D magnesium alloy plates of size
100 mm (length) × 100 mm (width) × 6 mm
(height). High speed steel is used as FSW
tool material. Fig. 1 shows the tool used for
welding and the welded specimens are pre-
sented in Fig. 2. Magnesium alloys are
most widely used to absorb shock and
vibration energy. For instance, cast Mg alloy AZ91D containing 9% Al and 1% Zn has
been most widely used in aircraft and engine building industries due to its high castabi-
lity, low density, and good mechanical properties. The initial joint configuration was
obtained by securing the plates in position using mechanical clamp. Single pass wel-
ding procedure was used to fabricate the joints. The tensile specimens were prepared to
evaluate the ultimate tensile strength. Tensile test was carried out in 60 tones capacity,
hydraulic universal testing machine.
Fig. 2. Images of the welded specimens.
Procedure of experiments. Two major tools
used in the Taguchi method are the orthogonal
array (OA) and the signal to noise ratio (S/N ratio).
The orthogonal array L9 is selected as shown in
Table 1, which has 9 rows corresponding to the
number of tests with the required columns. OA is a
matrix of numbers arranged in rows and columns.
A typical L9 orthogonal array is shown in Table 1.
In this array, the columns are mutually orthogonal.
That is, for any pair of columns, all combinations
of factor levels occur, thus giving an equal number
of times. Here, there are three parameters: A, B,
and C, each at three levels. This is called an “L9”
design, the 9 representing the nine rows, configu-
rations or prototypes to be tested. Specific test
characteristics for each experimental evaluation
are identified in the associated row of the table.
Thus, L9 means that nine experiments are to be
Table 1. L9 Orthogonal array
Factors
Experiments
A B C
1 1 1 1
2 1 2 2
3 1 3 3
4 2 1 2
5 2 2 3
6 2 3 1
7 3 1 3
8 3 2 1
9 3 3 2
Note: A – rotational speed, rpm;
B – welding speed, mm/min;
C – axial force, kN.
38
carried out to study three variables at three levels. The number of columns of an array
represents the maximum number of parameters that can be studied using that array.
The plan of experiments comprises 9 tests,
where the second column is assigned to the
rotational speed, the third column is assigned to
welding speed and the third column is assigned
to axial force. The factors and assigned levels
are presented in Table 2. By conducting trail
experiments the factors values were determined.
If rotational speed was lower than 1200 rpm,
the weld nugget was observed and it produced
insufficient heat generation and insufficient
metal transportation. When the rotational speed
was higher than 1600 rpm, a tunnel defect was observed and it caused turbulence.
Similarly, when the welding speed was lower than 25 mm/min, a pinhole type of the
defect occurred. For the welding speed higher than 75 mm/min, the insufficient heat
was generated thus giving the inadequate flow of the material. When the axial force
was lower than 2 kN, a tunnel and crack like defect occurred at the middle of the weld
cross section. If the force increased above 8 kN, large mass of flash and excessive
thinning were observed due to a higher heat input. The ranges of process parameters
selected are presented in Table 2.
The Taguchi methodology for optimization can be divided into four phases:
planning, conducting, analysis and validation. Each phase has a separate objective and
contributes towards the overall optimization process. The Taguchi method for optimi-
zation can be presented as a flowchart, shown in Fig. 3.
Fig. 3. Flowchart representing the Taguchi method for optimization:
phase 1 – planning; phase 2 – conducting; phase 3 – analysis; phase 4 – validation.
Results and discussion. Quality of the tensile strength is to be considered for
investigation in FSW joints. Taguchi suggests that the response values for each test
condition are processed by determining the signal to noise ratios (S/N) for each factor.
The S/N ratio (η) is the ratio of signal to noise in terms of power. Another way to look
at it is that it represents the ratio of sensitivity to variability. The higher the SNR, the
better quality of product is. The idea is to maximize the SNR and thereby minimizing
the effect of random noise factors which has significant impact on the process
Table 2. Process parameter
values at three levels
Level
A,
rpm
B,
mm/min
C,
kN
1 1200 25 2
2 1400 50 4
3 1600 75 6
39
performance. Therefore, the method of calculating the S/N ratio depends on whether
the quality characteristic is smaller-the-better, larger-the-better, or nominal-the-best.
We adopt the “Smaller is better” approach. The S/N ratio for this type of response was
used by employing formula,
21
10log ijk
S
Y
N n
= −
∑ , (1)
where n is the number of tests and Yijk is the experimental value of the ith quality
characteristic in the jth experiment at the kth test [7].
In the present study, the tensile strength results were analyzed to determine the
effect of FSW process parameters. The experimental results are transformed into means
and signal – to – noise (S/N) ratio. In this work means and signal to noise ratios are
calculated and the values are presented in Table 3. The analysis of the mean for each of
the experiment will give the better combination of parameter levels that ensures a high
level of precision for tensile strength. The mean for one level was calculated as the
average of all the three responses that were obtained with that level. The mean response
of raw data and S/N ratio of tensile strength for each parameter at level 1, 2, and 3 were
calculated and given in Table 3. The mean and S/N ratio of various parameters change
from the lower to higher levels and are also given in Table 4. It is clear that a larger S/N
ratio corresponds to better quality characteristics. Therefore, the optimal level of process
parameter is the level of the highest S/N ratio [7]. The mean effect and S/N ratio for
tensile strength are further processed by statistical software called Design Expert [8].
Table 3. Experimental test conditions and observed data
Input parameter Response
T1 T2 T3
S.No
A,
rpm
B,
mm/min
C,
kN MPa
Mean
value
S/N
ratio
1 1200 25 2 103 112 110 108.33 40.6925
2 1200 50 4 175 170 178 174.33 44.8259
3 1200 75 6 119 115 121 118.33 41.4618
4 1400 25 4 176 179 171 175.33 44.8771
5 1400 50 6 208 200 194 200.67 46.0496
6 1400 75 2 150 146 152 149.33 43.4829
7 1600 25 6 130 138 135 134.33 42.5634
8 1600 50 2 144 148 140 144.00 43.1672
9 1600 75 4 149 140 151 146.67 43.3268
Note: T1, T2 and T3 – tensile strengths; A – rotational speed, rpm; B – welding speed, mm/min;
C – axial force, kN.
Table 4. Main effects of tensile strength
Means S/N ratio Process
parameter
Level
A B C A B C
L1 133.66 139.33 133.88 42.33 42.71 42.45
L2 175.11 173.00 165.44 44.80 44.68 44.34
Average
value
L3 141.67 138.11 151.11 43.02 42.76 43.36
L2 – L1 41.45 33.67 31.56 2.47 1.97 1.89 Main
effects L3 – L2 –33.44 –34.89 –14.33 –1.78 –1.92 –0.98
Note: A – rotational speed, rpm; B – welding speed, mm/min; C – axial force, kN.
40
Table 5. ANOVA for main effects of tensile strength based on mean value
and S/N ratio value
Source DF SS, Seq SS, Adj MS, Adj SS′ F P Contribution, %
Rotational
speed
2
3002.89
/ 9.795
3002.89
/ 9.795
1501.44
/ 4.898
2975.33
/ 9.481
108.98
/ 31.17
0.009 /
0.031
44.38 / 41.07
Transverse
speed
2
2488.22
/ 7.583
2488.22
/ 7.583
1244.11
/ 3.792
2460.66
/ 7.269
90.30 /
24.13
0.011 /
0.0398
36.17 / 30.49
Axial force 2
1154.89
/ 5.394
1154.89
/ 5.394
577.44
/ 2.697
1127.33
/ 5.079
41.91 /
17.16
0.023 /
0.055
16.89 / 20.63
Error 2
27.56
/ 0.314
27.56
/ 0.314
13.78 /
0.157
221.52
/ 2.514
– – 3.32 / 10.89
Total 8
6673.56 /
2308.64
100.00 / 100.00
Note: numerator – mean value; denominator – S/N ratio value. DF – degrees of freedom; SS, Se;
SS, Adj – sequential and adjusted sum of squares; MS, Adj – adjusted mean squares; SS′ – pure sum of
squares; F – fisher ratio; P – probability that exceeds the 95% confidence level.
To analyze the data obtained from design of experiment, ANOVA technique is
employed to evaluate the statistical significance. The practical significance can be eva-
luated through the sum of squares, line or column charts, and normal probability chart.
Therefore, the optimum level of the process parameter is the level of the highest S/N
ratio. Furthermore, a statistical analysis of ANOVA variance can be performed to see
which process parameter is statistically significant for each quality characteristic [7].
The purpose of the ANOVA test is to investigate the significance of the process parame-
ters which affect the tensile strength of FSW joints. The ANOVA analysis based on mean
and S/N ratio is given in Table 5. The results of ANOVA indicate that the considered
process parameters are highly significant factors that affect the tensile strength of FSW
joints in the order of rotational speed, traverse speed and axial force.
Fig. 4. Trend of process parameters
with respect to the mean and S/N ratio
values: a – rotational speed, rpm;
b – welding speed, mm/min;
c – axial force, kN.
▲ – means; � – ratio.
The present study is aimed at identifying the most influencing significant para-
meter and percentage contribution of each parameter into tensile strength of the friction
stir welded AZ91D magnesium alloy joints by conducting minimum number of expe-
riments using Taguchi orthogonal array. Fig. 4 presents the trend of the process parame-
ters with respect to the mean and S/N ratio values of tensile strength. The factor levels
are controlled accurately by the percentage contribution of each factor. The percentage
41
contribution of the rotational speed, welding
speed, and axial force are shown in Fig. 5. It
must be noted that the above combination of
factor levels A2, B2, C2 are not among the
nine combinations tested for the experiment.
This is expected because of the multifactor
nature of the experimental design employed.
The optimum parameter value of tensile
strength is predicted at the parameters. The
estimated mean of the response characteris-
tics for tensile strength can be computed as
Tensile strength = RS2 + WS2 + AF2 – 2T, (2)
where RS2 is the average tensile strength at the second level of rotational speed,
1400 rpm; WS2 is the average tensile strength at the second level of welding speed,
50 mm/min; AF2 is the average tensile strength at the second level of axial force 4 kN.
Substituting the values of various terms in equation (2), we get
Tensile strength = 175.11 + 173 + 165.44 – 2 × 150.15 = 213.25 MPa.
CONCLUSIONS
The percentage contributions of FSW process parameters were determined. It was
found that the tool rotational speed had 44% contribution, welding speed – 36%
contribution, and axial force – 17% contribution to tensile strength of the welded joints.
The optimum value of the process parameters namely, rotational speed, welding speed
and axial force, are found to be 1400 rpm, 50 mm/min and 4 kN, respectively.
РЕЗЮМЕ. Досліджували зварювання тертям з перемішуванням (FSW) магнієвих
сплавів, литих матеріалів AZ91D та вивчали їх границю міцності на розрив. Оцінювали
параметри процесу FSW, а саме: швидкість обертання інструменту, швидкість зварюван-
ня та дію осьового навантаження на границю міцності на розрив, використовуючи прист-
рій Тагучі, та оптимізаційний підхід. Оптимізацію параметрів проводили за методикою
ANOVA та із врахуванням процентного внеску параметрів процесу.
РЕЗЮМЕ. Исследовали сварку трением с перемешиванием (FSW) магниевых спла-
вов, литых материалов AZ91D и изучали их предел прочности на разрыв. Оценивали па-
раметры процесса FSW, а именно: скорость вращения инструмента, скорость сварки и
действие осевой нагрузки на предел прочности на разрыв, используя установку Тагучи, и
оптимизационный подход. Оптимизацию параметров проводили по методике ANOVA и с
учетом процентного взноса параметров процесса.
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H. Fujii, M. Maeda, and K. Nogi // Scie. and Techn. Weld. and Join. – 2003. – 8. – P. 450–454.
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Received 07.04.2014
Fig. 5. The % contribution of factors into
mean values: I – rotation speed; II – wel-
ding speed; III – axial force; IV – error.
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