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| Other Laboratory
Experiments and Demonstrations
 This page contains experiments we used to do, or sometimes do,
or use in outreach events. Some are meant as classroom demonstrations,
some are shortened versions of the experiments we use in undergraduate
courses. Contents
- The Black Box Experiment
- The Slope of a Line
- Measuring Grain Size
- The Hot Wire Demonstration
- Laser and Electron Diffraction
- Heat Treatment of Aluminum Alloys,
Precipitation Hardening
- Heat Treatment of Steels, Eutectoid
Systems
- Kinetics of Grain Growth
- Hardenability of Steels
- Griffith Flaws in Brittle Materials
- Design, Fabrication, and Testing of Composites
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1. The Black Box Experiment
This experiment is done in physics courses across the country to
demonstrate essential elements of science. Students are asked to
examine a black box to try to determine what is inside. They make up
a series of experiments (tipping, shaking, weighing, etc.) and in doing so
propose and test their hypotheses as to what the object is. When
they think the know what is in the box, or as it often turns out, when
they have learned all they can about the box's contents, they present
their findings to fellow students for comment and criticism.
Students never get to open the box.
 | Procedure - Notes and the complete procedure for this experiment. |
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2. The Slope of a Line
This simple experiment is designed to teach how different people, looking
at the same data, can come up with different results. Students are
presented with a graph containing only data points, no lines, from a real
experiment and asked to draw their own line on the graph. They are
then asked to explain why they drew the line they way they did and to
interpret the results (a brief description of the experiment is given).
| Procedure - Notes and the complete procedure for this experiment. |
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3. Measuring Grain Size
This simple experiment is used to illustrate the importance of
standardized techniques, in this case, an ASTM method for measuring grain
size. Students use the mean lineal intercept method to measure grain
size from the same micrograph. Everyone should get the same results,
within the limits of statistical error.
| Procedure - Notes and the complete procedure for this experiment. |
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Artificially generated microstructure used in this
experiment. |
4. The Hot Wire Experiment
This is a classic demonstration of an unexpected behavior of a steel wire.
When heated it expands, presumably due to thermal expansion. When
cooled again, it shrinks but the it also does something unexpected.
We use this experiment to demonstrate the importance of the observational
skills of a scientist.
| Procedure - Notes and the complete procedure for this experiment. |
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5. Laser and Electron Diffraction
In this experiment students use a laser to project the diffraction
patterns of different mesh grids on the wall, then they measure the
locations and angles between the diffraction spots to determine the mesh
size, symmetry, and orientation of the grid. Next, the students
perform a similar analysis on an electron diffraction pattern obtained
using a transmission electron microscope to again determine the size,
symmetry and orientation of the unit cell.
| Procedure - Notes and the complete procedure for this experiment. |
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Left: Image and Fourier transform of a TEM grid, Right:
image and diffraction pattern of the same TEM grid. |
6. Heat Treatment of Aluminum Alloys, Precipitation Hardening
Aluminum alloys are strengthened primarily by precipitating many fine hard
particles from a saturated "solid solution". In this experiment the
students solution treat and age three aluminum alloys and observe the
influence of time and temperature on peak hardness, the stages of the
aging process and the effect of over-aging.
| Procedure - Notes and the complete procedure for this experiment. |
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TEM image of copper precipitates in an aluminum-copper
alloy. |
7. Heat Treatment of Steel, Eutectoid Systems
There are many ways to harden steel and the
method used is based not only the desired hardness but also the desired strength,
ductility, toughness and cost. In this experiment students learn which factors determine
the maximum attainable hardness and the responsiveness of several steels to heat
treatment. They heat treat the steels, hardness test them and examine their
microstructures using the optical microscopes. From this one can begin to understand the
basic reasons for the observed relationships between the heat treatments, the evolution of
the microstructure and the mechanical properties.
| Procedure - Notes and the complete procedure for this experiment. |
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The eutectoid structure of 1095 steel. A small amount
of proeutectoid cementite can be seen at the grain boundaries. |
8. Kinetics of Grain Growth
Many materials are polycrystalline and the size of these
crystals (grains) can range from nanometers to inches. In this experiment the students
anneal specimens of brass, examine the resulting microstructure using optical microscopes
and measure the grain size using standard stereological techniques. The results are
analyzed in terms of the ideal grain growth behavior and are discussed in terms of the
role of the diffusivity of the copper and zinc in the brass.
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Large grains produced by annealing 70/30 brass for one hour
at 750C. |
9. Hardenability of Steels
Hardenability is the ability to harden a steel at a given distance from
the surface. If the steel has good hardenability it may be possible to get high hardness
several inches into the material. In this experiment students anneal 1-inch diameter steel
rods at over 900C then water quench them on only one end. The hardness is then measured
every sixteenth of an inch or so from the quenched end and the distance where the hardness
starts to fall off is noted. This is the classic Jominy End-Quench test. Using it the
students learn that the carbon content in a steel determines its maximum hardness while it
is the other alloying elements that determine its hardenability.
| Procedure - Notes and the complete procedure for this experiment. |
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Jominy sample mounted in the hardness tester. |
10. Griffith Flaws in Brittle Materials
This experiment is based on Ernsberger's work in the 1960's where he
demonstrates the existence of pre-existing Griffith flaws in glass, flaws
which are too small to see using high-resolution microscopes. The
procedure employed an ion-exchange process using KNO3 and NaNO3
to introduce stresses in the surface of glass microscope slides.
| Procedure - Notes and the complete procedure for this experiment. |
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11. Design, Fabrication, and Testing or Composites
In this experiment students design, fabricate, and 3-point bend test
plaster-based composite bricks they designed and made. Students can
select from a number of available reinforcing materials (wire, screen,
string, sand, saw dust, etc.) and using molds make their own composite
bricks. When fully hardened teach brick is 3-point bend tested to
failure. The failure load and the type of failure is noted, and the
results, including the strength per weight and cost per weight ratios,
are compiled.
| Procedure - Notes and the complete procedure for this experiment. |
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3-point bend testing of composite samples. |
