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Tensile Testing Masterclass
Martin Carr(Schools Liaison Officer)Department of MaterialsParks RoadOxford OX1 3PH
Tel. 01865 273 710 Email:[email protected]
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.