Rajdeep Banik_14PME021_ppt

Department of Mechanical Engineering

National Institute of Technology, Agartala

RAJDEEP BANIK.

Enrollment:- 14PME021

Optimization of process parameters for Friction Stir Welding of AA6061 and AA7075 alloys

Under the guidance of Dr. Subrata Kumar Ghosh & Mr. Barnik Saha Roy

For the award of degree

of

Master of Technology

OUTLINE

1. Introduction about FSW.

2. Parameters.

3. Literature survey.

4. Conclusions from review papers.

5. Motivation of work.

6. Objective of present study.

7. Experimental plan.

8. Observations and analysis.

9. Taguchi - Grey Optimization.

10. Conclusions.

11. Future scopes.

12. References.

2

Friction Stir Welding (FSW)

• Recently (1991)

developed solid state

welding technique [1].

• Uses mechanical

stirring to join metals.

• Yields high weld

strength.

• Can be used to join

aluminum, copper.

3

Figure 1: The principle of Friction Stir Welding [2]

Parameters

• Tool rotation speed

• Tool Traverse speed

• Plate position

• Tilt angle

• Surface roughness

4

Literature Survey

5

Serial

No. Author & year Workpiece material Remarks

1 Hasan I. Dawood et.

al., 2015 6061 aluminium alloy

Least surface roughness gives the

best tensile strength for AA6061

alloy.

2 V. Saravanan et. Al,

2014

AA2014-T6 and AA7075-T6

aluminum alloy

D/d ratio of 3 gives a sound

welding.

3 S. Ravikumar et. al.,

2014

AA6061 and AA7075 aluminum

alloy

Taper cylindrical threaded tool

gives the best mechanical

properties.

4 Sefika Kasman et.

al., 2013


alloy

Maximum hardness was achieved

at harder alloy side, irrespective

of welding conditions.

5 J.F. Guo et. al. ,

2013


alloy

Softer alloy was kept on the

advancing side.

6 M. Koilraj et. al.,

2012


alloy

A D/d ratio of 3 contributes to

60% of the overall weld strength.

7 M Jayaraman et.

al., 2008 A319 aluminum alloy

Tool rpm is the dominant

parameter for the tensile strength,

followed by welding speed.

Literature Survey (continued)

6

Serial

No. Author Workpiece material Remarks

8 R. K. Kesharwani et.

al., 2014

AA5052-H32 and

AA5754-H22 aluminum

alloy

For 2mm thin plates, very high tool

rpm (1800 rpm) can be used.

9 M. Cabibbo et. al., 2007 AA6056 aluminum alloy

Tensile strength is weaker for the

welded joint compared to an

unwelded specimen.

10 Chang Hee Suh et. al.,

2010 6K21-T4 aluminum alloy

Sheets below 1 mm shows drastically

reduced tensile strength.

11 Long Wan et. al., 2014 6082-T6 aluminum alloy

Tensile fracture occurs at the HAZ

adjacent to the TMAZ on the softer

alloy side.

12 T. Venugopal et. al.,

2004 AA7075 aluminum alloy

TMAZ-nugget interface is softest part

followed by the nugget zone.

13 K.V.P.P Chandu et. al.,


Square tool pin profile gives the best

welding due to its pulsating action.

14 Inderjeet Singh et. al.,


Insignificant effect of welding

parameters on the impact strength was

observed.

Conclusions from review papers

• For cylindrical tool, a D/d ratio of 3 gives the best welds.

• Tool rpm is the dominant parameter, followed by welding speed.

• Welding efficiency is always less than 100%.

• TMAZ-nugget interface hardness is low as compared to the nugget

zone.

• Least surface roughness gives the best tensile strength.

• Maximum hardness is achieved at harder alloy side.

7

Motivation of work

• AA7075 alloy is a very costly alloy used in aerospace, marine and

space industries.

• AA7075 alloy is difficult to weld by fusion welding process [3].

• AA 6061 alloy is cheap and available easily.

• Attaching a 6061 alloy part to a 7075 alloy body will reduce the

total cost.

• Some loss in strength of welded joints occur in present situations [4].

8

Comparison of material composition and mechanical properties

9

[5]

[5]

Objective of present study

• To weld aluminium alloy 6061 and 7075 by FSW

• To study the effect of process parameters on Ultimate tensile strength of joint (UTS)

• To study the effect of process parameters on percentage elongation during tensile testing of the joint

• To study the effect of process parameters on Vickers’s microhardness of the joint (HV 0.1)

• To study of the microstructure of the welded joint.

• To develop a mathematical model to predict the mechanical properties of the joint by Regression Analysis using commercial software MINITAB

• To optimize the process parameters using Grey Relational Analysis

• To perform a confirmatory test as per the result obtained from Grey Relational Analysis.

10

Experimental plan

6mm plates of 7075 and 6061 aluminium alloy have been purchased.

The plates have been cut into pieces of 300 X 65 mm.

The cut pieces have been machined into straight edges using the shaper

machine.

Trial experiments have been performed based on the parameters obtained

from literature reviews, and a level for each parameters have been decided

based on the resulting welds.

L16 orthogonal array have been designed taking four parameters each with

four levels.

11

Tool pin profile

12

Figure 5: Shape of the tool used in the friction stir welding operation.

Parameter table

Levels Surface

roughness

Tool rotational

speed (rpm)

Welding speed

(mm/sec)

Tilt angle

(deg)

1 A 800 1 0

2 B 1200 2 1

3 C 1600 3 2

4 D 2000 4 3

13

Table 2: Parameter table for performing the experiments.

14 Table 3: L16 orthogonal array for performing the experiments.

Serial Surface

roughness Tilt angle RPM

Speed

(mm/sec)

1 A 0° 800 1

2 A 1° 1200 2

3 A 2° 1600 3

4 A 3° 2000 4

5 B 0° 1200 3

6 B 1° 800 4

7 B 2° 2000 1

8 B 3° 1600 2

9 C 0° 1600 4

10 C 1° 2000 3

11 C 2° 800 2

12 C 3° 1200 1

13 D 0° 2000 2

14 D 1° 1600 1

15 D 2° 1200 4

16 D 3° 800 3

Experimental plan (continued)

The work pieces have been polished using different grades of emery paper,

viz., 400, 600, 800, 1000, to achieve different levels of surface roughness.

The surface roughness for each workpiece have been measured using the

3D profilometer.

The surface roughness was measured in three areas in each work piece and

then an average value of the ‘Ra’ value have been taken as a parameter.

Welding have been done as per the design of experiments.

Samples for tensile, impact, hardness and microstructure have been cut

from the welded plates.

15

Emery paper

grade

Aluminium

6061

Aluminium

7075

Surface

roughness

400 0.336 µm 0.286 µm A

600 0.524 µm 0.409 µm B

800 0.255 µm 0.153 µm C

1000 0.265 µm 0.167 µm D

16

Table 4: Surface roughness (Ra) values obtained after polishing.

Locations of sample extraction

17

Figure 9: Sample extraction regions

18

Figure 10: Tensile specimens made from the welded samples along with samples from base metals.

Tensile specimens

19

Figure 11: Charpy Impact specimen made from base metal.

Impact specimen

20

Figure 12: Locations of hardness testing.

Hardness indentation points

21

Figure 13: Hardness graph from AA6061 to 7075

OBSERVATION TABLE

Serial no. Surface

roughness

Tilt

angle RPM

Speed

(mm/sec) UTS (MPa)

Percentage

elongation

Hardness

(HV 0.1)

Toughness

(Nm)

1 A 0° 800 1 198.8 1.91 135.80 10

2 A 1° 1200 2 218.66 1.77 133.87 11.5

3 A 2° 1600 3 238.94 2.78 135.687 7.5

4 A 3° 2000 4 194 1.112 138.14 9.5

5 B 0° 1200 3 187.46 1.42 138.35 5.0

6 B 1° 800 4 200.66 1 145.45 7.5

7 B 2° 2000 1 233.06 2.525 130.944 14

8 B 3° 1600 2 241.46 2.8 129.907 11

9 C 0° 1600 4 200 0.96 144.275 4.5

10 C 1° 2000 3 228.8 1.193 128.271 10.5

11 C 2° 800 2 240 2.56 135.394 9

12 C 3° 1200 1 224.26 2.786 124.20 11

13 D 0° 2000 2 160.4 0.7 135.016 9

14 D 1° 1600 1 224.4 2.46 129.705 12.5

15 D 2° 1200 4 240.66 2.79 145.15 10.5

16 D 3° 800 3 239.6 2.925 141.635 8.5

22

Table 5: Experimental observation table.

Microstructure study

23

Figure 15: Micrograph showing the material mixing in the stir zone.

24

Figure 16: Further magnification shows the grains in the stir zone.

Regression equations for UTS

25

Figure 15: Scatterplot of the experimental data versus the theoretical values.

26


27

Regression equations for elongation

28


29


30

Regression equations for hardness

31


32


33

Regression equations for toughness

34


35


36

Taguchi - Grey Optimization

Step 1:

• Normalized values of responses:

• For Larger the better: x = (𝑥)−min(𝑥)

max(𝑥)− min(𝑥)

• For Smaller the better: x = max(𝑥)− (𝑥)

max(𝑥)− min(𝑥)

37

SL no. UTS Elongation Hardness Toughness

1 0.47372 0.54382 0.54588 0.57895

2 0.71873 0.48090 0.45506 0.73684

3 0.96891 0.93483 0.54056 0.31579

4 0.41451 0.18517 0.65600 0.52632

5 0.33383 0.32360 0.66588 0.05263

6 0.49667 0.13483 1.00000 0.31579

7 0.89637 0.82022 0.31736 1.00000

8 1.00000 0.94382 0.26856 0.68421

9 0.48853 0.11685 0.94471 0.00000

10 0.84382 0.22157 0.19158 0.63158

11 0.98199 0.83596 0.52678 0.47368

12 0.78781 0.93753 0.00000 0.68421

13 0.00000 0.00000 0.50899 0.47368

14 0.78954 0.79101 0.25906 0.84211

15 0.99013 0.93933 0.98588 0.63158

16 0.97705 1.00000 0.82047 0.42105

Table 6: Normalised values for ‘larger the better’ of each performance characteristics 38


Step 2:

• Grey relation coefficients of the responses:

• The grey relation coefficients ξi (k) are calculated as:

39

SL no. UTS Elongation Hardness Toughness

1 0.48720 0.52291 0.52404 0.54286

2 0.63998 0.49063 0.47850 0.65517

3 0.94146 0.88469 0.52114 0.42222

4 0.46062 0.38028 0.59242 0.51352

5 0.42875 0.42503 0.59943 0.34545

6 0.49834 0.36625 1.00000 0.42222

7 0.82832 0.73553 0.42278 1.00000

8 1.00000 0.89899 0.40603 0.61290

9 0.49433 0.36149 0.90043 0.33333

10 0.76199 0.39110 0.38214 0.57576

11 0.96523 0.75297 0.51376 0.48718

12 0.70206 0.88894 0.33333 0.61290

13 0.33333 0.33333 0.50454 0.48718

14 0.70377 0.70523 0.40292 0.76001

15 0.98064 0.89179 0.97254 0.57576

16 0.95611 1.00000 0.73580 0.46341

Table 7: Grey Relation Coefficient of Each Performance Characteristics (𝜓=0.5). 40


Step 3:

• Grey relation grades are calculated as:

41

SL no. Surface

roughness

Tilt

angle

Rotational

speed

Welding

speed

Grey relation

grade

S/N

ratio

1 1 0 800 1 0.519253 -5.69241

2 1 1 1200 2 0.56607 -4.94259

3 1 2 1600 3 0.692377 -3.19314

4 1 3 2000 4 0.486708 -6.25463

5 2 0 1200 3 0.449667 -6.94217

6 2 1 800 4 0.571704 -4.85657

7 2 2 2000 1 0.746659 -2.53755

8 2 3 1600 2 0.72948 -2.73973

9 3 0 1600 4 0.522397 -5.63998

10 3 1 2000 3 0.527747 -5.55148

11 3 2 800 2 0.679784 -3.35258

12 3 3 1200 1 0.634308 -3.95399

13 4 0 2000 2 0.414595 -7.64751

14 4 1 1600 1 0.642981 -3.83603

15 4 2 1200 4 0.855182 -1.35882

16 4 3 800 3 0.788833 -2.06029

Table 8: Grey Relation Grade for each of the experiments.

42

43

Figure 18: The set of optimum parameters using ‘larger is better’ signal-to-noise.

ANOVA TEST

44

Source of

variation

Sum of

squares

Degrees

of

Freedom

Mean of

squares F- value

Percentage

contribution

(%)

Surface

roughness 0.02679 3 0.00893 8.6615 12.537

Tool

rotation 0.027233 3 0.009077 8.804 12.744

Tilt angle 0.1565717 3 0.05219 50.6207 73.272

Welding

speed 0.003093 3 0.001031 1.447

Error 4

Total 0.213688 100

Table 9: ANOVA table showing percentage contribution of parameters.

CONFIRMATION TEST

45

Tests Initial welding

(experiment) Prediction

Confirmation

test Improvement

Parameter

levels A4-B3-C2-D4 A4-B3-C3-D1 A4-B3-C3-D1

0.739 % Grey relation

grade 0. 855182 0.8950 0.90162

Table 10: Improvement of grey relation grade after performing the confirmation test.

CONCLUSIONS

Two different aluminium alloys have been successfully welded by friction stir welding.

Tool tilt angle have been found out as the most dominant parameter.

Regression equations have been developed for each tests based on the observed values.

From Grey relational optimization, the optimum parameters obtained are surface roughness of 0.2 µm, 1600 rpm of tool rotational speed, 1mm/sec of welding speed and tilt angle of 2 degrees.

Mathematical model for Grey Relational Grade (GRG) has developed and the confirmatory test have shown an improvement of 0.739% in the GRG.

46

FUTURE SCOPES

Bend test can be performed on the welded samples

Fatigue test can be performed on the welded samples

SEM investigation may be used to study the failure location and provide

the confidence so that the AA6061 and AA7075 can be used for automobile

and aerospace structures.

Measurement of generated forces and torque and correlating them to the

resulting material properties.

Different types of tool pin profile as another parameter.

47

REFERENCES 1. Sefika Kasman & Zafer Yenier. The dissimilar friction stir welding of AA5754 and AA7075

aluminum alloys. Int J Adv Manuf Technol (2014) 70:145–156.

2. Hasan I. Dawood, Kahtan S. Mohammed, Azmi Rahmat, Uday M.B. The influence of the

surface roughness on the microstructures and mechanical properties of 6061 aluminium

alloy using friction stir welding. Surface & Coatings Technology 270 (2015) 272–283.

3. V. Saravanan, Nilotpal Banerjee, R. Amuthakkannan, S. Rajakumar. Microstructural

Evolution and Mechanical Properties of Friction Stir Welded Dissimilar AA2014-T6 and

AA7075-T6 Aluminum Alloy Joints. Metallogr. Microstruct. Anal. (2015) 4:178–187.

4. J.F. Guo , H.C. Chen, C.N. Sun, G. Bi, Z. Sun, J. Wei. Dissimilar AA6061 and AA7075 Al

alloy using friction stir welding with a variety of different process parameters. Materials

and Design 56 (2014) 185–192.

5. M. Koilraj, V. Sundareswaran, S. Vijayan, S.R. Koteswara Rao. Optimization of parameters

using Taguchi technique for friction stir welding of dissimilar aluminum alloys AA2219 to

AA5083. Materials and Design 42 (2012) 1–7.

48

REFERENCES 6. M Jayaraman, R Sivasubramanian, V Balasubramanian, A K Lakshminarayanan. Optimized

the process parameters for friction stir welding of cast aluminium alloy A319 by Taguchi

method. Journal of Scientific & Industrial Research Vol. 68, January 2009, pp. 36-43.

7. R. K. Kesharwani, S. K. Panda, S. K. Pal. A multi objective optimization of parameters

affecting weld quality in tailored friction stir butt welding of 2.0 mm thin dissimilar sheets

of AA5052-H32 and AA5754-H22 using Taguchi grey based approach. Procedia Materials

Science 6 ( 2014 ) 178 – 187.

8. M. Cabibbo, H.J. McQueen, E. Evangelista, S. Spigarelli, M. Di Paola, A. Falchero.

Microstructure and mechanical property studies of AA6056 friction stir welded plate.

Materials Science and Engineering A 460–461 (2007) 86–94.

9. Chang Hee Suh, Yun-Chul Jung and Young Suk Kim. Effects of thickness and surface

roughness on mechanical properties of aluminum sheets. Journal of Mechanical Science and

Technology 24 (10) (2010) 2091~2098.

10. Long Wan, Yongxian Huang, Weiqiang Guo, Shixiong Lv, Jicai Feng (2013). Mechanical

Properties and Microstructure of 6082-T6 Aluminum Alloy Joints by Self-support Friction

Stir Welding. J. Mater. Sci. Technol., 2014, 30(12), 1243 - 1250.

49

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