Tensile Testing Masterclass

Martin Carr(Schools Liaison Officer)Department of MaterialsParks RoadOxford OX1 3PH

Tel. 01865 273 710 Email:Martin.Carr@materials.ox.ac.uk

Aims

• To raise awareness of Materials Science to schools.

• To encourage closer contact between schools and Materials Science Departments.

• To enable schools to have access to expertise and equipment that is beyond the reach of most schools.

Pedagogy - Preliminary• Teachers should

introduce Tensile Testing, strss – strain charts and relevant terminology BEFORE the Masterclass.– Plasticine and sand

“Model” – Preliminary Experiments

Pedagogy - Preliminary

• Plastic behaviour of metals is modelled by the plastic behaviour of plastic-ine.

• “Sand” mimics the effect of carbon• Measurements and observations can

be made.– The “Feel” of the stress-strain chart.– Fracture surface appearance.– Necking.– Ductility.

Pedagogy - Masterclass• Tensile Test Specimens are

broken. Measurements and Observations are made and compared to % C content…– % increase in length– % reduction in area– Microstructure– Hardness– Strength

Results: Stress-Strain Charts Stress-Strain Plots for Different Carbon Contents

0.00E+00

1.00E+02

2.00E+02

3.00E+02

4.00E+02

5.00E+02

6.00E+02

7.00E+02

8.00E+02

9.00E+02

1.00E+03

0.00E+00 5.00E-02 1.00E-01 1.50E-01 2.00E-01 2.50E-01 3.00E-01 3.50E-01 4.00E-01 4.50E-01 5.00E-01

Mil

lio

ns

Strain

Str

es

s /

Pa

0.02% C 0.18% C 0.41% C 0.54% C 0.8%C 3%C

Results: Mechanical Properties

Plot of Hardness as a Function of Carbon Content

0

50

100

150

200

250

300

350

400

-0.50 0.00 0.50 1.00 1.50 2.00 2.50 3.00 3.50

Carbon Content / % Carbon

Ha

rdn

es

s

Hardness Hardness - CI

Plot of % Reduction in Area as a Function of Carbon Content

-20

0

20

40

60

80

100

-0.50 0.00 0.50 1.00 1.50 2.00 2.50 3.00 3.50

Carbon Content / % Carbon

% R

ed

uc

tio

n i

n A

rea

% Area Reduction % Area Reduction - CI

Plot of % Elongation as a function of Carbon Content

0

10

20

30

40

50

60

-0.50 0.00 0.50 1.00 1.50 2.00 2.50 3.00 3.50

Carbon Content / % Carbon

% E

lon

ga

tio

n

% Elongation % Elongationm - CI

Plot of Tensile Strength for Carbon Steels

0.000E+00

1.000E+08

2.000E+08

3.000E+08

4.000E+08

5.000E+08

6.000E+08

7.000E+08

8.000E+08

9.000E+08

1.000E+09

-0.50 0.00 0.50 1.00 1.50 2.00 2.50 3.00 3.50

% Carbon

Te

ns

ile

Str

en

gth

Tensile Strength Tensile Strength - CI

Overview• Initial learning curve is very steep.

• Students split into groups of about 4– Team work– Allocation of responsibilities– Collection of data.– Some, not all, students get good results.

• Data from each group is collected at the end of the session and copied onto a USB memory stick for the teacher to take away together with specimen data.

Benefits To The School• Experience of working in an undergraduate teaching

lab on a cut-down undergraduate experiment.

• Interaction with student demonstrators.

• Concrete experience of an abstract part of a teaching course.

• Teacher could use data for coursework.

• Links with the department which could be developed further.

Benefits To The Department• One aspect of Materials Science is highlighted.

• Opportunity to raise awareness further

• Links with teachers may result in more sixth formers considering Materials Science as a career.

• Can be linked with “Aspiration” / “Gifted and Talented” and similar initiatives.

• Promotes Physical Sciences and Engineering on a broader basis.

Materials UsedMaterial Supplier…Orchard Materials LtdUnit 7, Brunel WayThornbury Industrial Estate, ThornburyBristol   BS35 3UR

Remko Iron 0.02%C080A15 0.18%C080A42 0.41%C070M55 0.54%CS202 0.82%C

Heat Treatment – in HouseNormalise all steel in the same way…• Heat in the furnace and hold at 860˚C for 1 hour.

• Remove from furnace and air cool out of draughts.

Engineering Supplies

CNC MachiningJacobs and SonsUnit 6, Park Farm Industrial EstateGreetGloucestershire,   GL54 5BX

For bulk orders, machining approx. £1.55 to £1.65 each.