tension report

Use Materials in Engineering

(41978)

Lecturer: Medhat Boutros

Laboratory Work 1 Report

Tension Test

By Gayan Wijetilleke

(041102375)

Table of contents

1. Introduction

1.1 Objective......................................................................................................... 3

1.2 Apparatus........................................................................................................ 3

2. Procedure…………………………………………………………………………………………………………. 4

3. Test 1 – Black mild steel....................................................................................... 5

4. Test 2 – Bright mild steel...................................................................................... 8

5. Test 3 - Aluminium...................................................................................... ……….. 11

6. Test 4 – Brass........................................................................................................ 14

7. Discussion.…………………………………………………………………………………………………………. 17

8. Conclusion............................................................................................................. 17

1. Introduction

The determination of a material’s mechanical properties indicates what type of applications a material can be used for. For example, a material that has a high elastic tendency would be an ideal material to select for the manufacture of a spring, whereas a highly ductile material with a low elastic tendency would be a poor choice. The mechanical properties of a material consist of its yield strength, tensile strength, modulus of elasticity and a host of other properties. This laboratory work comprises of four tests where tension is applied to four types of metals to find out it’s special properties.

1.1 Objective

The aim of this laboratory test is to find the yield, ultimate tensile stress, Young’s Modulus of Elasticity, percentage elongation and percentage reduction in area for four test specimens subjected to tension.

1.2 Apparatus

Hydraulic Universal Testing machine, extensometer, vernier calliper, ruler, black mild steel, bright mild steel, aluminium and brass test specimens.

The Hydraulic Universal Testing machine is mainly designed for tension, compression, bending and cutting test of metal materials and meet with the requirements of elevated temperature tensile testing covered by Australian standards AS 2291. This machine is also used for compression and bending test of non-metal materials, such as cement, concrete and so on. Equipping with special auxiliaries, it can be used for mechanical property testing of fastener, wire rope and components. They are ideal testing instrument for project quality testing section, university and college, research institution and industrial and mining enterprise.

The test is conducted by subjecting a suitably prepared specimen to a steady increasing uni-axial force, as normally continued until the specimen fractures. Ever effort is made to ensure a uniform distribution of the force over the cross-sectional area of the specimen to avoid any other applied or induced stressed. The tensile test machine is essentially a device to exert a ‘pull’ on a test specimen is attached by grips to a fixed crosshead.

An extensometer is a device that is used to measure small/big changes in the length of an object. It is useful for stress-strain measurements and tensile tests. Its name comes from "extension-meter".

http://en.wikipedia.org/wiki/Strain_(materials_science)

http://en.wikipedia.org/wiki/Stress_(physics)

2. Procedure

1. Measure the diameter of the test specimens.2. Examine the extensometer, check that the plates are set to the correct diameter range and

note the gauge length and the calibration.3. Place the specimen between the jaws of the upper platen, locking it securely in place.4. Attach the extensometer to the specimen.5. Load the pointer to zero of the testing machine. Place the maximum load pointer against the

load pointer.6. Adjust the lower platen until the specimen is between its jaws then holding the jaws tight

with the key, apply a slight tensile load until they grip the specimen.7. Remove the key, zero the extensometer’s large dial reading, record the reading of the small

gauge and adjust the loading valve to give a slow rate of load increase.8. Place the pen on the graph.9. Take simultaneous readings of load and extension starting at 1000N, then 1000N increments

until the yield point is reached. At this point the load pointers will stop, then fall back slightly, and finally continue to rise.

10. Immediately the yield point is passed the extensometer must be removed.11. Loading is continued with 1000N increments and the extensions are measured with a ruler.

This needs to go on until the specimen fractures.12. Close the loading valve after the fracture. The fractured ends are examined and sketched

and the minimum diameter and final length measured carefully with the calliper and ruler.13. Remove the pen from the recording position.14. Record the specimen material and failure load on the graph paper.15. Repeat the procedure with the other specimens.

3. Test 1 – Black mild steel

Results and calculations of tension test for Black mild steel

Force (kN) Extension (mm) Strain Stress (MPa)1 0.0000 0.00000 9.972 0.0000 0.00000 19.933 0.0010 0.00002 29.904 0.0030 0.00006 39.875 0.0050 0.00010 49.846 0.0080 0.00016 59.807 0.0090 0.00018 69.778 0.0110 0.00022 79.749 0.0130 0.00026 89.71

10 0.0150 0.00030 99.6711 0.0170 0.00034 109.6412 0.0190 0.00038 119.6113 0.0200 0.00040 129.5814 0.0225 0.00045 139.5415 0.0240 0.00048 149.5116 0.0260 0.00052 159.4817 0.0275 0.00055 169.4418 0.0290 0.00058 179.4119 0.0310 0.00062 189.3820 0.0325 0.00065 199.3521 0.0350 0.00070 209.3122 0.0365 0.00073 219.2823 0.0390 0.00078 229.2524 0.0400 0.00080 239.2225 0.0425 0.00085 249.1826 0.0440 0.00088 259.1527 0.0460 0.00092 269.1228 0.0480 0.00096 279.0829 0.0495 0.00099 289.05

Specimen diameter Initial 11.30mm, Final 5.66mm

Initial gauge length 50mm Upper & lower yield load 36kN, 35kN

Ultimate load 50.8kN Failure load 30kN

Final length 68.5mm

Area = π4

×d2 = 100.29mm2

% Elongation =68.5−5050

×100% = 37%

% Area Reduction =100.29−25.16100.29

×100% = 74.9%

Below is the graph of the table. The graph shows the Young’s Modulus of Elasticity by taking the best line fit and the Young’s Modulus of Elasticity is E = 270.158 GPa.

0 0.0002 0.0004 0.0006 0.0008 0.001 0.00120

50

100

150

200

250

300

350

f(x) = 270158.22829294 x + 20.5958017329332

Stress/Strain Graph

Stress (Mpa)Linear (Stress (Mpa))

According to the Original graph, there are 65.3 units vertical to the ultimate load point.

Therefore one unit is = 50.865.3

= 0.7779 kN per unit

To calculate the horizontal scale,

Two points of forces, 25kN and 5kN are marked using the vertical scale. And the corresponding extension values (0.0425 and 0.005 respectively) are taken from the table. After measuring the gap between these two values the horizontal scale is measured.

The gap between 0.026 and 0.056 is approximately 7 units. Therefore the horizontal scale is,

0.0425−0.0057

= 0.0537 mm per unit

The fracture shape is below

Below is the Original graph put in to scale.

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 50

10

20

30

40

50

60

Black Mild Steel

Extension (mm)

Load

(kN

)

4. Test 2 – Bright mild steel

Results and calculations of tension test for Bright mild steel


10 0.0010 0.00002 99.6711 0.0020 0.00004 109.6412 0.0040 0.00008 119.6113 0.0050 0.00010 129.5814 0.0060 0.00012 139.5415 0.0070 0.00014 149.5116 0.0070 0.00014 159.4817 0.0120 0.00024 169.4418 0.0280 0.00056 179.4119 0.0300 0.00060 189.3820 0.0310 0.00062 199.3521 0.0330 0.00066 209.3122 0.0350 0.00070 219.2823 0.0360 0.00072 229.2524 0.0365 0.00073 239.2225 0.0365 0.00073 249.1826 0.0365 0.00073 259.1527 0.0365 0.00073 269.1228 0.0365 0.00073 279.0829 0.0365 0.00073 289.05

Specimen diameter: Initial 11.30mm, Final 8.28mm

Initial gauge length 50mm Approximate yield load 58.8kN

Ultimate load 59.7kN Failure load 40.8kN

Final length 55.5mm

Area = π4

×d2 = 100.29mm2


×100% = 37%

% Area Reduction =100.29−53.85100.29

×100% = 46.31%


0 0.0001 0.0002 0.0003 0.0004 0.0005 0.0006 0.0007 0.00080

50

100

150

200

250

300

f(x) = 190984.322867436 x + 92.2145245111301

Stress/Strain graph



Therefore one unit is = 59.776.9



Two points of forces, 10kN and 15kN are marked using the vertical scale. And the corresponding extension values (0.026 and 0.056 respectively) are taken from the table. After measuring the gap between these two values the horizontal scale is measured.


0.056−0.0262

= 0.015 mm per unit


0 0.1 0.2 0.3 0.4 0.5 0.60

10

20

30

40

50

60

70

Bright Mild Steel

Extension (mm)

Load

(kN

)

The proof stress value (P0.1%) is found out by drawing a parallel line to the elasticity line and shifting it 0.05mm to the right in the extension/load graph and the value is

5. Test 3 - Aluminium

Results and calculations of tension test for Aluminium


10 0.055 0.00110 99.6711 0.063 0.00126 109.6412 0.645 0.01290 119.6113 0.068 0.00136 129.5814 0.085 0.00170 139.54


Initial gauge length 50mm Approximate yield load 15kN

Ultimate load 17.9kN Failure load 3.5kN

Final length 61.5mm

Area = π4

×d2 = 100.29mm2


×100% = 23%

% Area Reduction =100.29−17.35100.29

×100% = 82.7%

Below is the graph of the table. The graph shows the Young’s Modulus of Elasticity by taking the best line fit and the Young’s Modulus of Elasticity is E = 79.201GPa.

0 0.0002 0.0004 0.0006 0.0008 0.001 0.0012 0.0014 0.0016 0.00180.00

20.00

40.00

60.00

80.00

100.00

120.00

140.00

160.00

f(x) = 79200.7023363029 x + 10.0842812840602

Stress (Mpa)


According to the Original graph, there are 23 units vertical to the ultimate load point.

Therefore one unit is = 17.923



Two points of forces, 5kN and 7kN within the elasticity area are marked using the vertical scale. And the corresponding extension values (0.025 and 0.037 respectively) are taken from the table. After measuring the gap between these two values the horizontal scale is measured.

The gap between 0.025 and 0.037 is approximately 1 unit. Therefore the horizontal scale is,

0.037−0.0251

= 0.012 mm per unit



-0.1 0 0.1 0.2 0.3 0.4 0.5 0.60

2

4

6

8

10

12

14

16

18

20

Aluminium

Extension (mm)

Load

(kN

)


6. Test 4 - Brass

Results and calculations of tension test for Brass

Force (kN) Extension (mm) Strain Stress (Mpa)1 0.0000 0.00000 9.972 0.0000 0.00000 19.933 0.0005 0.00001 29.904 0.0010 0.00002 39.875 0.0040 0.00008 49.846 0.0080 0.00016 59.807 0.0120 0.00024 69.778 0.0180 0.00036 79.749 0.0210 0.00042 89.71

10 0.0260 0.00052 99.6711 0.0310 0.00062 109.6412 0.0350 0.00070 119.6113 0.0500 0.00100 129.5814 0.0550 0.00110 139.5415 0.0560 0.00112 149.5116 0.0560 0.00112 159.4817 0.0590 0.00118 169.4418 0.0750 0.00150 179.4119 0.0800 0.00160 189.3820 0.0850 0.00170 199.3521 0.0860 0.00172 209.3122 0.0865 0.00173 219.2823 0.0865 0.00173 229.2524 0.0900 0.00180 239.2225 0.0930 0.00186 249.18


Initial gauge length 50mm Approximate yield load 49kN

Ultimate load 54kN Failure load 54kN

Final length 51.5mm

Upper yield load

Area = π4

×d2 = 101.7mm2


×100% = 3%

% Area Reduction =101.7−53.85101.7

×100% = 47.05%


0 0.0002 0.0004 0.0006 0.0008 0.001 0.0012 0.0014 0.0016 0.00180

50

100

150

200

250

f(x) = 91733.6341419172 x + 47.0843252148073

Stress (Mpa)



Therefore one unit is = 5468.8



Two points of forces, 10kN and 15kN within the elasticity area are marked using the vertical scale. And the corresponding extension values (0.026 and 0.056 respectively) are taken from the table. After measuring the gap between these two values the horizontal scale is measured.


0.056−0.0262

= 0.015 mm per unit



0.0000 0.1000 0.2000 0.3000 0.4000 0.5000 0.6000 0.7000 0.80000.0000

10.0000

20.0000

30.0000

40.0000

50.0000

60.0000

Brass

Extension (mm)

Load

(kN

)


7. Discussion

From the results of the percent reduction in area calculations, a comparison of the ductility of the four metal test specimens, black mild steel, bright mild steel, aluminum and brass can be made. It was noted that the % of area reduction of the aluminium, 82.7%, had a higher value than the other metals. Bright Mild Steel gave a 46.31% of area reduction which implies that it would be better suited to an application where the strength of the material is an asset and aluminum would be a good choice for an application where a more brittle material is needed.

Out of all these four, black mild steel is stronger and has a long elasticity than the others while aluminium is the least strong and broke quickly. The shape of failure is similar in bright mild steel and black mild steel but aluminium specimen snapped without making any cup or cone shape.

A percent elongation calculation, however, can also be used to determine a material’s ductility. The applied force before testing began may have skewed the actual values. Error is also present in that the extensometer used in the specimen’s tension test may have slipped during the experiment. This would cause the strain values used in calculation to be inaccurate. Improvements to this experiment are few and far between. The tension test is an excellent way to gather certain mechanical properties of materials. The reading s taken at the time of the test are approximate values and it might be different with the graph drawn on the sheet at that time.

The original graph is not that clear hence the values are approximate values but it is very close to the graph and the table. The graph drew according to the table helped us to find the young’s modulus of elasticity by getting the best line fit for that values. The table shows Elasticity of approximately 200GPa for steels, 100GPa for Brass and 80GPa for Aluminium while during the test we got 270Gpa for bright mild steel, 190GPa for black mild steel, 79GPa for Aluminium and 91GPa for brass which are within an acceptable range.

9. Conclusion

This report examines the strength of four specimen and their behaviours when put into test by applying tension on it. The four specimen are black mild steel, bright steel, aluminium and brass. Load is applied uniformly on the specimen and it starts to neck in the middle section and after a special point it breaks. This varies on the specimen used.

The load is applied from zero and increased uniformly until the specimen breaks. When load is applied on the metal it starts to elongate and the elongation depends on the metal. After a point the metal breaks after showing much elongation at its ultimate load point.

The steel specimen has an ultimate tensile strength value which is greater than that of aluminium. This implies that the steel can sustain higher stresses before necking and inevitably fracturing. Therefore, it can be concluded that the steel is a tougher material than the aluminium. Another method of determining the strength of a material is using the stress-strain curve. Develop an equation for the stress-strain curve and integrate it with respect to the strain axis.

In conclusion we found out how much load these metals can sustain until it breaks, the elasticity, fracture shape, metal features, and from the graph we can find the ultimate tensile stress, yield proof stress, % of area reduction and % of elongation.

tension report

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