METHODOLOGY AND INSTRUMENTATION

TENSILE TESTING LAB

Aaron Teager

Methodology

• Determine dimensions• Mark the sample with lines at 10mm intervals• Zero instrumentation• Set up the equipment• Slowly increase the load, recording the results with Hounsfield

test paper• Remove extensometer at 0.2mm extension• Remove the sample when it fractures and record the

necessary measurements.

Instrumentation

Extensometer• Measures the change in length of an

object• Two types: Contact and Non-Contact• Contact is normally cheaper, yet still

have high precision• Non – contact usually involves lasers• Lindley dial gauge extensometer used in

experiment

Instrumentation

Hounsfield Hand Operated Testing Machine• Allows for a sample to be

tested under tension• Often equipped with a

mercury force gauge and a roll of test paper

Instrumentation

Instron Tests• More expensive than the

Hounsfield• Greater accuracy• Not used in Lab because of

expense.

.

THEORY BEHIND TENSILE TESTING

TENSILE TEST LABTomos St John

For

ce, F

(N

)

Elongation, Dl (m)

Plastic Deformation

Elastic Deformation

The Tensile Test

Elastic Deformation

Bonds stretching

Returns to it’s original size when force is released

Metals don’t stretch much elastically

Plastic Deformation

Atoms slide over one another due to dislocations in the structure

Sample won’t return to original size

Metals deform more plastically than elastically

Equations

F

A

Stress

In Pa or N.mm2

0

Le

L

Strain

No units

Elastic Behavior

E e

Hooke’s Law

E= Young’s modulus

A measure of stiffness

Plastic Behavior

Eng. Strain

En

g. S

tres

sContinuous Yielding

No unique yield point

Use PROOF STRESS instead

Eng. Strain

En

g. S

tres

s Upper Yield Stress (UYS)

Lower Yield Stress (LYS)

Discontinuous Yielding

UYS is hard to pin point

LYS commonly used as yield point

Ductility

Either measured as

% elongation to failure

Or

% reduction in area at failure

ALUMINIUM

TENSILE TESTING LAB

Prajwal Vittapanhally Chandra Shekara

Aluminium

• General information Chemical formula: Al Molecular weight: 26.98 gm It is the second most malleable metal and sixth most

ductile. • Composition 1000 series (Al, Si) 3000 series (Al, Mn, Cu, Mg, Si, Fe) 5000 series ( Al, Mg, Mn, Si, Fe, Zn) 8000 series (Al, Sn, Ni, Si, Fe)

Properties of Aluminium

Physical Properties Density: 2.7 g/cm3 melting point : approx 5800C

Mechanical properties Young's modulus - 68-72 GPa Poisson's ratio - 0.33 Tensile Strength - 70-360 MPa Hardness- Vickers - 30-100 Hv Yield Strength - 30- 286 MPa compressive strength – 30- 286 MPa Elongation - 2-41 %

Table of results explained Load, F [kN] Stress, σ [Mpa] Extension, [10-6] Strain , ε [10-6]

0.2 8.15 4 800.4 16.30 11 2200.6 24.45 19 3800.8 32.60 23 4601.0 40.75 29 5801.2 48.90 38 7601.4 57.05 47 9401.6 65.20 58 11601.8 73.35 71 14202.0 81.50 88 17602.2 89.65 113 22602.4 97.80 152 3040

Sample CalculationsModulus of Elasticity = Stress/ Strain = 52.975 × 106 / 1088.3 × 10-6 = 48.69 GPa Limit of Proportionality and Tensile Strength is Calculated by plotting Load, F[kN] vs

Extension, [10-6 m ] and Stress Vs Strain Graph.

Comparing graphs

0 500 1000 1500 2000 2500 3000 35000

20

40

60

80

100

120

Aluminium

Strain, ε(10-6)

Stre

ss

(MPa

)𝞼

BRASS

TENSILE TESTING LAB

Yang Zhang

Composition • Alloy (copper with 5-40% zinc)

Properties• Young’s modulus 90-110 GPa• Yield strength 95-500 MPa• Tensile strength 310-550 MPa• Elongation 5-60 %• Vickers hardness 65-220 HV ——Good malleability and corrosion resistance

Zinc content increases

Density , electrical and thermal conductivities decrease

The tensile strength and Vickers hardness increase

Results(Overall & Extensometer)

0 0 0 00.3 15.8 8 1600.6 31.6 15 3000.9 47.4 23 4601.2 63.3 31 6201.5 79.1 38.5 7701.8 94.9 47 9402.1 111 55 11002.4 127 63 12602.7 142 72.5 1450

3 158 82 16403.3 174 93 18603.6 190 109 21803.9 206 129 25804.2 221 161 3220

Load,F(kN)Stress(MPa)

Extension(10 -̂6m)

Strain(10 -̂6)Original Length 50 mm

Final Length 69 mm

Original Area 18.97 mm 2̂

Final Area 14.53 mm 2̂

Elongation 38%

Reduction in area 23%

Graph (Extensometer)

0 500 1000 1500 2000 2500 3000 35000

50

100

150

200

250

Strain (10 -̂6)

Stre

ss

(MPa

)

Results(Extensometer)

• The shape of the stress-strain curve is nearly a straight line

• Young’s modulus is the gradient of the straight line

•

Results(“Hounsfield”)

Yield Stress

Tensile Strength

Calculation& Comparison

All calculation results correspond with the textbook values.

MILD STEEL

TENSILE TESTING EXPERIMENT

Muhammad Amin Ismail

COMPOSITON AND PROPERTIES OF MILD STEEL

Also known as Low-Carbon Steel.

Composition:-• Ferum: 99.70%wt - 99.98%wt• Carbon: 0.02%wt – 0.25%wt

General properties:• Density: 7800 – 7900 kgm-3

Mechanical properties:Modulus of Elasticity 200 – 250 GPa

Yield Strength 250 – 395 MPa

Tensile Strength 345 – 580 MPa

Elongation 26% – 47%

Hardness 107.5 – 172.5 HV

TABLE OF RESULTLoad, F

(kN)Stress, σ

(MPa)Extension, δ

(10-6 m)Strain, ε

(10-6)0.0 0 0 0

0.4 12.9 6 120

0.8 25.8 13 260

1.2 38.7 19 379

1.6 51.6 26 519

2.0 64.5 32 639

2.4 77.3 37 739

2.8 90.2 43 859

3.2 103.0 50 999

3.6 116.0 56 1118

4.0 129.0 62 1238

4.4 142.0 67 1338

4.8 155.0 74 1478

30TABLE 1: Table of Stress, Extension, and Strain for respective Load of Mild Steel.

TABLE OF RESULT

31

Original length (mm) 50

Final Length (mm) 66

Original Area (mm2) 31.03

Final Area (mm2) 28.50

   

% Elongation 32.00

% Reduction in Area 8.15

TABLE 2: The Cross-sectional dimensions of Mild Steel

THE RELATIONSHIP BETWEEN STRESS AND STRAIN FOR MILD STEEL

32

0 200 400 600 800 1000 1200 1400 16000

20

40

60

80

100

120

140

160

180

Strain, ε (10-6)

Stre

ss, σ

(MPa

)

FIGURE 1: Graph of Stress vs Strain.

THE RELATIONSHIP BETWEEN LOAD AND EXTENSION FOR MILD STEEL

33FIGURE 2: Graph of Load vs Extension.

Ultimate Tensile Stress

Upper Yield StressLower Yield Stress

SAMPLE CALCULATION

34

7.0 COMPARISON SECTION

TENSILE TESTING LAB

James Alexander Douthwaite

7.1 Why do we compare?

36

•Allows trends to be identified and plotted.

•To determine how are results might effect real life applications.

•To develop a standard, with which to compare others.

•It allows us to predict what might happen in later experiments (e.g. What a combination of the materials might exhibit).

37

7.2 Our Results

0 200 400 600 800 1000 1200 1400 1600 1800 2000 2200 2400 2600 2800 3000 3200 34000

20

40

60

80

100

120

140

160

180

200

220

240

0

12.9

25.8

38.7

51.6

64.5

77.3

90.2

103

116

129

142

155

0

15.8

31.6

47.4

63.3

79.1

94.9

111

127

142

158

174

190

206

221

Aluminium Brass Steel

Stress, ɛ (10^-6)

Stra

in, σ

(MPa

)

A comparison of the relationships between stress and strain for the metals Aluminium, Brass and Mild Steel.

38

7.2 Our Results

Aluminium:Brass:Mild Steel:

• The three metals behaved in very different ways.• Aluminium was the softest, more ductile of the

three samples.• Brass behaved in a less ductile manner.• Mild Steel was the stiffest of the three metals.• The ultimate tensile strength (UTS) varied greatly

between metals.

39

7.3 Interpretation

It is clear from the graph that....

The way these metals behaved in this test reflects how they are used in the real world.

Everyday products take advantage of materials chosen for their unique properties.

These days materials made to very exact specifications by splicing the properties of two or metals together to get the characteristics needed.

40

7.4 Application

• Low energy plastic deformation.

• Low Density- Lightweight.

• Highly recyclable.

41

7.4 Application- Aluminium

Key properties:

Key Properties:

42

7.4 Application- Brass

• Relatively Low Density.

• Higher elastic/plastic limit than aluminium, however still relatively low- malleable.

• Corrosive/tarnish resistant due to its zinc content.

• Decorative.

Key Properties:

43

7.4 Application- Mild Steel

• High UTS

• Very “stiff”- ideal for a wide range of civil applications.

• Cheap, carbon content.

ERRORS & CONCLUSION

TENSILE TESTING LAB

Simon Sladden

Systematic Errors

Incorrect data analysis E.g. manual calculation of strain value led to results

being incorrect by a power of 10

Zero error Incorrect calibration of mercury scale on Hounsfield test machine due to air bubble

Engineering stress and strainEngineering stress and strain were used to make comparison to true stress and strain values in

textbooks.

Random Errors Irregular data recording intervals

Small variations in stress & strain could have been missed on force-extension graphs e.g. UYS and LYS of mild-steel

Uncontrolled temperature Small room warms up after time with group of people.

Reading off small scalesSmall & non-conventional scales on Force-Extension

graph axes making it hard to read accurately

Micrometer scale may be misread

Improvements

Use Instron Testing MachineDigitally plots force-extension graphs at regular intervals

– more accurate

Calibration of measurement scales automatic

Repeat testing to calculate mean valuesCalculate mean values from 3 samples of each metal

Laser extensiometerMore accurate measurement of extension without

making contact with sample.

Industrial Applications Wide range of uses for tensile testing:

Aerospace: Turbine blades

Automotive: Seatbelts/Bumpers/Mudflaps

Packaging: Ring pulls/tight packaging

Sport: Racquet strings

SUMMARY Tensile test of 3 metals

Mild Steel: Highest UTS & stiffnessBrass: Most ductileAluminium:

Use to industry:Appropriate material selection based on tensile

properties Meet safety, strength, deformation constraints

Ensure manufacturing quality and consistency

Material applications:Mild steel: structural material (e.g. Bridges) due to high stiffness and strength.Brass:Aluminium:

ANY QUESTIONS?

THANK YOU FOR LISTENING