Expt 7 - Tesion Test

ME 218: SOLID MECHANICS LABORATORY

T E NS IO N T E S T EXPERIMENT NO.7

BATCH: A8 07010042-07010046

TENSION TEST EXPERIME NT NO. 7

AIM

To determine the following in axially loaded Mild steel and Aluminium Specimens. (a) The maximum tensile stress (b) The modulus of elasticity. (c) The percentage reduction in cross section. (d) The percentage elongation in gauge length.

A PPA R A TU S 1. 2. 3. 4.

The Universal Testing Machine Vernier Callipers Mechanical Extensometer Scale WORKI NG FORM UL AE

σ = F/A Y = σ/ε Where, F  Load applied on specimen (N) A  Area of cross-section (m2) σ  Stress (Pa) ε Strain Y Young’s Modulus of Elasticity (ratio of stress and strain in the linear region)

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SPECIMEN DIAGRAMS

OBSERVATI ON

Aluminium Specimen :Gauge length (average) = 101 mm Total length (average) = 200 mm

Table 7.1:- ( Diameter ) Sl.No Reading (mm)

1

2

3

7.00

7.01

7.00

dave = 7.00 mm

Area of specimen = (π × d2)/4 = (3.14×72)/4×10-6 = 38.465 × 10-6 m2.

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Table 7.2:-

( Stress and Strain values of Aluminium specimen)

Sl No

Reading of Extensometer (μm)

F (N)

Stress (MPa)

Strain (μm)

1

2

950

24.69778

2

2

4

1293

33.61497

4

3

6

1406

36.55271

6

4

8

1516

39.41245

8

5

10

1915

49.78552

10

6

12

2096

54.4911

12

7

14

2350

61.0945

14

8

16

2659

69.12778

16

9

18

2893

75.21123

18

10

20

3145

81.76264

20

11

22

3426

89.06798

22

12

24

3635

94.50149

24

13

26

3895

101.2609

26

14

28

4053

105.3685

28

15

30

4188

108.8782

30

16

32

4324

112.4139

32

17

34

4772

124.0608

34

18

36

5043

131.1062

36

19

38

5362

139.3995

38

20

40

5548

144.235

40

Mild Steel Specimen :Gauge length (average) = 100.67 mm Total length (average) = 200 mm

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Table 7.3:- ( Diameter ) Sl.No Reading (mm)

1

2

3

7.00

6.98

7.00

dave = 6.993 mm

Area of specimen = (π × d2)/4 = (3.14×6.992)/4×10-6 = 38.355 × 10-6 m2.

Table 7.4:-

( Stress and Strain values of Mild Steel specimen)

Sl No

Reading of Extensometer (μm)

F (N)

Stress (Pa)

Strain (μm)

1

2

2899

75.58337

2

2

4

3816

99.49159

4

3

6

4416

115.1349

6

4

8

5142

134.0634

8

5

10

6067

158.1802

10

6

12

6611

172.3634

12

7

14

7448

194.1859

14

8

16

8406

219.1631

16

9

18

9041

235.7189

18

10

20

9933

258.9754

20

11

22

10546

274.9576

22

12

24

11259

293.5471

24

13

26

12214

318.4461

26

14

28

12877

335.732

28

15

30

13489

351.6882

30

16

32

14162

369.2348

32

17

34

14700

383.2616

34

18

36

15538

405.1102

36

19

38

16079

419.2152

38

20

40

16523

430.7913

40

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G R A PH S

Stress(MPa) Vs Strain (μm) 160 140 120 100

80 60 40 20

Stress

0 0

5

10

15

20

25

30

35

40

45

Graph for Aluminium

Stress(MPa) Vs Strain (μm) 500 450 400 350 300 250 200 150 100

Strain (μm)

50 0 0

5

10

15

20

25

Graph for Mild Steel

6

30

35

40

45

C A L C U LA TI O N S

Aluminium:For yield stress :F = 8910 N A = 38.465 10-6 m2 Y=F/A=231.64 106 Pa For ultimate tensile stress:F = 9710 N A = 38.465 10-6 m2 Y=F/A=252.43 106 Pa For percentage elongation:Gauge length after breaking =115 mm Elongation = 14.3 mm Percentage elongation = (14.3÷ 101) ×100 = 14.15 % For reduction in area:Final diameter of the specimen = 5.64mm Afinal = (3.14 × 5.642)/4 = 24.97 × 10-6 m2 Ainitial = 38.465 ×10-6 m2 Reduction in area=38.465 ×10-6 m2 - 24.97 × 10-6 m2 = 13.49 ×10-6 m2 Percentage reduction= 35.07 % From graph :Value of Young’s Modulus of Elasticity = slope of the graph = 79.32 GPa

Mild Steel :For yield stress :F = 23,300 N A = 38.355 10-6 m2 Y=F/A=607.48 106 Pa For ultimate tensile stress:F = 26,400 N A = 38.355 10-6 m2 Y=F/A=688.31 106 Pa

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For percentage elongation:Gauge length after breaking = 105 mm Elongation = 4.33 mm Percentage elongation = (4.33÷100.67) ×100 = 4.3 % For reduction in area:Final diameter of the specimen = 5.32mm Afinal = (3.14 × 5.322)/4 = 22.22 × 10-6 m2 Ainitial = 38.355 ×10-6 m2 Reduction in area=38.355 ×10-6 m2 - 22.22 × 10-6 m2 = 13.165 ×10-6 m2 Percentage reduction= 34.32 % From graph :Value of Young’s Modulus of Elasticity = slope of the graph = 196.19 GPa

I N FE R E NC E

The following inferences can be drawn :

Specimen

% Reduction in area of cross-section

% Elongation in

Tensile Stress Max

Modulus of Elasticity

Aluminium

252.43 MPa

79.32 GPa

35.07%

14.15%

Mild Steel

688.31 MPa

196.19 GPa

34.32%

4.3%

gauge length

The obtained values of Moduli of Elasticity of Aluminium and Mild Steel are found to be in close agreement with standard values.

SO U RC E S O F ER ROR

1. There is slight difference while taking down the readings from the Universal Testing Machine and the actual reading, hence the graph is not truly linear. 2. There is experimental error due to the rapidly increasing values of load (F). 3. The material might have internal defects or imperfections that could lead to botched results.

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D E TA I L S O F STU D EN TS

Table 7.5 ROLL NUMBER

NAME

07010042

Repaka Jyoti Swaroop

07010043

Sharath Chandra Pawar

07010044

Puvvada N V Prudhvi Teja

07010045

J G M V Pramod

07010046

Vishnu Narayanan Suresh

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