Title of Experiment: TENSILE TESTING (UNIVERSAL TESTER)Course and Course Code: MECHANICS AND MATERIALS LAB (MEMB221)Semester and Academy Year : SEM 1 2015/2016Day and Date ofExperiment Performed: 17th JUNE 2015Due Date: 22ND JUNE 2015Group Members: 1. RAJKUMAR BALAKRISHNAN (ME093045) 2. KIRIBANATH GANESH (ME093041) 3. SURENDERAN LOGAN (ME093015) 4. ANANTHAKUMAR MARIAPPAN (ME093037) 5. DIVEYAA GOVINDARAJU (ME093023)Section and Group Number: SECTION 06 , GROUP 01Instructor Name: NURASLINDA BINTI ANUAR

TABLE OF CONTENT

CONTENT PAGES

Summary/ Abstract

Objective

Theory

Description of Apparatus

Procedure

Observations

Analysis and Results

Discussions

Conclusions

References

Appendices

SUMMARY

The objective of this experiment is to understand the principles of tensile testing. Besides to investigate stress-strain relationship of two types of materials specimens under a tensile test. Materials that been investigated are aluminum and brass. By doing the tensile test, we can determine the elongation at fracture, tensile strength, yield strength and modulus of elasticity. This experiment is used to determine the materials properties and is used in very wide range of industries.

The experimental procedures are then followed. Readings of elongation and its corresponding force are taken and tabulated. The stress-strain values are calculated and a graph of load against elongation is plotted. From this graph, the mechanical properties such as modulus of elasticity, yield strength, tensile strength and elongation at fracture are determined.

THEORY

If a load is static or changed relatively slowly with time and is applied uniformly over a cross section /surface of a member, the mechanical behaviour may be ascertained by a simple stress-strain test. These tests are most commonly conducted for metals at room temperature. There are three principal ways in which the load may be applied: tension, compression and shear. Tension is one of the most common mechanical stress-strain tests. The stress-strain diagram shows the different behaviour of the individual materials particularly clearly. Each material has a characteristic pattern of stress and strain. A standard specimen is deformed, usually to fracture with a gradually increasing tensile load that is applied uniaxially along the long axis of a specimen. Most of the tension tests for metals are conducted according to the ASTM Standard E 8 and E 8M, Standard Test Methods for Tension Testing of Metallic Materials.

a) Fundamental Principles of the Tensile Test

Figure 1

The tensile test is the best known test in material testing. It determines tensile strength, one of the most important properties of material. Furthermore, it is also possible to determine elongation at fracture as a toughness measurement of the material.

In the tensile test, a mono-axial stress is generated in a material sample. This stress is included via external loading of the sample in a longitudinal direction via a tensile force. There is then an even distribution of direct stress in the test cross-section of the sample. (Figure 1)

In order to determine the strength of the material, loading of the sample is slowly and continuously increased until it fails. The maximum test force occurring is a measurement of the strength of the material. The so-called tensile strength, RM is calculated from the maximum test force, FB and the initial cross-section area, A0 of the sample:-

The simplest way to of determining the maximum test force is via the maximum pointer on the force display. In the tensile test itself, the cross-section of the sample is reduced it is constricted and the actual stresses are considerably higher.

The elongation at fracture, A refers to the change in length of the sample compared with its original length, L0 and is calculated using the length, LU of the sample after fracture:-

In order to measure the lengths, two measuring marks are applied to the test bar. After fracture, two ends of the sample are placed together neatly at the fracture point and the distance between the two measuring marks is measured.

b) Fundamental Principles of Stress-Strain Diagram

Figure 2

The stress-strain diagram (Figure 2) shows the different behaviour of the individual materials particularly clearly. Each material has a characteristic pattern of stress and strain.

Important material data can be read from the stress-strain diagram. In addition to tensile strength, RM, the limit proportionality, RP is particularly interesting. Beneath this limit, the material conforms to Hookes Law with the Modulus of Elasticity, E: Strain, is proportional to stress, :-

When this stress is exceeded, deformation is no longer proportional to the load.

One particular important parameter from technical point of view is the yield point, RE. From this point onwards, the material becomes continuously plastically deformed. Deformation remains when load is relieved. To safeguard the function of the component, it should not be loaded any further.

With some materials, such as annealed soft steel, pronounced creeping occurs from the yield onwards. The sample is elongated without the load being increased further. In materials without pronounced creeping, the proof stress Rp0.2 is specified. In such a case, the material has a permanent elongation of 0.2% which remains after relief of the loadThe diagram (Figure 3) shows the curves of mild steel and an aluminium alloy.

Figure 3

The mild steel ruptures virtually without plastic deformation but has a very high tensile strength .In the aluminium alloy, the stress-strain curve rises less steeply in the elastic zone than the other steel materials because of the lower modulus of elasticity.

Figure 4

The stress-strain diagram (Figure 4) is produced from the values for force and the elongation recorded during the tensile test.

And

Alternatively, the load extension diagram may be drawn directly for pre-determined sample dimensions. In such a case, the characteristic remain unaltered, but the time-consuming conversion of measurements into strain and stress is unnecessary.

Poissons Ration

Poissons ration is defined as Wherex = the strain perpendicular to the tensile axisz = the longitudinal strain

In general increases during the run, starting about 0.3 in the elastic region and about 0.5 after the material begins to deform plastically.

PROCEDURE

Set up test device as following:

1. The hand wheel on the master cylinder is untwisted as far as it will go and the load frame is moved down to its lowest position.1. The gripping heads in the upper cross-member and cross-head is inserted.1. The gripping heads is screwed down with the short bolt at the bottom and with pressure pad. 1. Gripping head with the long bolt is screwed at the top 1. The required tensile sample is inserted. 1. The test length LO of the sample is measured and noted down between two marks. 1. The sample is screwed by hand into the lower gripping head as far as the end stop. 1. The sample is screwed into the upper gripping head as far as the end stop, by rotating the gripping head itself. 1. The nut on the upper gripping head is tighten by hand until he gripping head is seated without slack in the upper cross-member. 1. The dial gauge is adjusted1. The dial gauge is pushed upwards on the support bar until the tracer pin is touching the drive.1. The rotating scale on the dial gauge is set to zero.1. The maximum pointer on the force display is set to zero.

Experimental steps

1. Slowly and constantly loaded by rotating the hand wheel.1. Application of the force should spread over a time interval of 5-10 minutes.1. It is important to avoid sudden, jerky force application.1. Observe the dial gauge and the sample. 1. Read the force from the display every 0.1 mm and make note of it with the corresponding extension. From 1 mm extension the reading interval can be extended to 0.2 mm.1. Monitor the sample and note when constriction begins. From now on, the force will no longer increase, but instead will tend to decrease.1. ATTENTION: Do not be startled. Particularly with some material, fracture will occur with a loud bang.1. Read the maximum test force from the maximum pointer and make note of it.1. Remove the sample from the gripping heads.1. Twist back the hand wheel on the master cylinder as far as it will go and move the load frame down.1. Repeat the same procedures with the other specimen.

Data and ObservationData collected for the elongation of the aluminum specimen

Extension(mm)Force (kN)

0.10

0.20

0.30.1

0.40.2

0.50.3

0.60.4

0.70.5

0.80.6

0.90.8

11

1.21.4

1.41.8

1.62.2

1.82.6

23

2.23.5

2.44

2.64.5

2.85

35.5

3.26

3.46.5

3.66.8

3.87.2

47.4

4.27.5

4.47.6

4.67.7

4.87.8

57.8

5.27.8

5.47.8

5.67.8

5.87.8

67.8

6.27.8

6.47.8

6.67.8

6.87.8

77.8

7.27.8

7.47.8

7.67.8

7.87.8

87.8

8.27.8

8.47.8

8.67.9

8.87.9

97.9

9.27.9

9.47.9

9.67.9

9.87.9

107.9

10.27.9

10.48

10.68

10.88

118

11.28

11.48

11.68

11.88

128

12.28

12.48

12.68

12.88

138

13.28

13.48.1

13.68.1

13.88.1

148.1

14.28.1

14.48.1

14.68.1

14.88.1

158.1

15.28.1

15.48.1

15.68.1

15.88.1

168.1

16.28.1

16.48.1

16.68.1

16.88.1

178.1

17.28.1

17.48.1

17.68.1

17.88.1

188.1

18.28.2

18.48.2

18.68.2

18.88.3

198.3

19.28.3

19.48.3

19.68.4

19.88.4

208.5

20.28.5

20.48.5

20.68.5

20.88.5

218.5

21.28.5

21.48.5

21.68.5

21.88.5

228.5

22.28.5

22.48.5

22.68.5

22.88.5

238.5

23.28.5

23.48.5

23.68.5

23.88.5

248.5

24.28.5

24.48.5

24.68.5

24.88.5

258.5

25.28.5

25.48.5

25.68.5

25.88.5

268.5

26.28.5

26.48.5

26.68.5

26.88.5

278.5

27.28.5

27.48.5

27.68.5

27.88.6

288.6

28.28.6

28.48.6

28.68.6

28.88.6

298.6

29.28.6

29.48.6

29.68.6

29.88.6

308.7

30.28.7

30.48.7

30.68.7

30.88.7

318.7

31.28.7

31.48.7

31.68.7

31.88.7

328.7

32.28.7

32.48.7

32.68.7

32.88.7

338.7

33.28.7

33.48.7

33.68.7

33.88.7

348.7

34.28.7

34.48.7

34.68.7

34.88.7

358.7

35.28.7

35.48.7

35.68.7

35.88.7

368.7

36.28.7

36.48.7

36.68.6

36.88.6

378.6

37.28.6

37.48.6

37.68.6

37.88.6

388.6

38.28.6

38.48.6

38.68.6

38.88.6

398.6

39.28.6

39.48.6

39.68.6

39.88.6

408.6

40.28.6

40.48.6

40.68.6

40.88.6

418.6

41.28.6

41.48.6

41.68.6

41.88.6

428.6

42.28.6

42.48.6

42.68.6

42.88.6

438.5

43.28.5

43.48.5

43.68.5

43.88.5

448.5

44.28.5

44.48.4

44.68.4

44.88.4

458.4

45.28.4

45.48.4

45.68.4

45.88.4

468.4

46.28.4

46.48.3

46.68.3

46.88.3

478.3

47.28.3

47.48.3

47.68.2

47.88.2

488.2

48.28.1

48.48.1

48.68.1

48.88

498

49.28

49.48

49.68

49.87.8

507.8

50.27.8

50.47.8

50.67.8

50.87.6

517.6

51.27.6

51.47.6

51.67.5

51.87.5

527.5

52.27.5

52.47.4

52.67.4

52.87.4

537.4

53.27.4

53.47.2

53.67.2

53.87.2

547.2

54.27.2

54.47.2

54.67.2

54.87

557

55.27

55.47

55.67

55.87

566.7

56.26.7

56.46.7

56.66.7

56.86.7

576.7

57.26.7

57.46.7

57.66.5

57.86.5

586.5

58.26.2

58.46.2

58.66.2

58.86.2

596.2

59.26.2

59.46

59.66

59.8

Data collected for the elongation of the brass specimen

Extension(mm)Force (kN)

0.10.1

0.20.2

0.30.4

0.40.5

0.50.8

0.61

0.71.3

0.81.5

0.91.7

11.9

1.22.4

1.42.9

1.63.4

1.83.9

24.4

2.25

2.45.5

2.66

2.86.5

37

3.27.5

3.47.9

3.68.1

3.88.4

48.6

4.28.8

4.48.9

4.69

4.89.05

59.1

5.29.1

5.49.1

5.69.1

5.89.1

69

6.29

6.49

6.69

6.89

79

7.29

7.49

7.69

7.89

89

8.29

8.49

8.69

8.89

99

9.29

9.49

9.69.2

9.89.2

109.2

10.29.2

10.49.2

10.69.2

10.89.2

119.2

11.29.2

11.49.2

11.69.2

11.89.2

129.2

12.29.2

12.49.2

12.69.1

12.89.1

139.1

13.29.1

13.49.1

13.69.1

13.89.1

149.1

14.29.1

14.49

14.69

14.89

159

15.29

15.49

15.69

15.89

169

16.29

16.49

16.69

16.89

179

17.29

17.49

17.69

17.89

188.9

18.28.9

18.48.9

18.68.8

18.88.8

198.8

19.28.8

19.48.6

19.68.6

19.88.6

208.6

20.28.6

20.48.6

20.68.6

20.88.6

218.6

21.28.6

21.48.6

21.68.6

21.88.6

228.6

22.28.5

22.48.5

22.68.5

22.88.5

238.5

23.28.5

23.48.5

23.68.5

23.88.5

248.5

24.28.5

24.48.5

24.68.5

24.88.5

258.5

25.28.5

25.48.5

25.68.5

25.88.5

268.5

26.28.5

26.48.5

26.68.5

26.88.5

278.5

27.28.5

27.48.5

27.68.5

27.88.5

288.5

28.28.4

28.48.4

28.68.4

28.88.3

298.3

29.28.3

29.48.2

29.68.2

29.88.2

308.2

30.28.2

30.48.2

30.68.2

30.88.1

318.1

31.28.1

31.48.1

31.68.1

31.88.1

328.1

32.28.1

32.48.1

32.68.1

32.88.1

338

33.28

33.48

33.68

33.88

348

34.28

34.47.9

34.67.9

34.87.9

357.8

35.27.8

35.47.7

35.67.7

35.87.7

367.6

36.27.6

36.47.6

36.67.6

36.87.6

377.6

37.27.5

37.47.5

37.67.5

37.87.4

387.4

38.27.4

38.47.3

38.67.3

38.87.2

397.2

39.27.1

39.47.1

39.67.1

39.87.2

407

40.26.9

40.46.9

40.66.8

40.86.7

416.6

41.26.6

41.46.6

41.66.6

41.86.6

426.5

42.26.5

42.46.4

42.66.4

42.86.3

436.3

43.26.2

43.46.2

43.66.2

43.86.1

446.1

44.26.1

44.46.1

44.66.1

44.86.1

456

45.26

45.4

Observations:

For the brass specimen, when the specimen was about to rupture, there was a necking phenomenon which occurred. The specimen did not break with a loud sound. Whereas for the aluminum specimen, there was little necking and the specimen made a loud bang sound when the specimen ruptured.

Analysis

Below are the graphs of the force applied versus the extension of the metal.

Graph 1: Stress Strain Diagram for the Aluminum Specimen

Graph 2: Stress Strain Diagram for the Brass Specimen

Calculations:

307699556.6 Pa

285981538.4 Pa