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Analysis
Convert
the raw position-applied load data collected by the Instron
into an engineering stress-strain
curve by normalizing the data using the
original sample length and cross-sectional area. From this curve compute the
Youngs modulus and yield stress of the material. Compare these values with those
published
for the test material. You will need to use the library or some
reference handbook to get this data.
Calculate the area under the
elastic region of the curve up to the yield stress. This quantity is the
Resilience
of the material and a measure of the strain energy per unit volume
of the material at the point of yield. Locate the maximum of the stress-strain
curve. The stress at this point is known as the Tensile Stress of the material.
Compare the value you measure to the published value. Compute the total
area under the stress-strain curve to sample fracture. This is a measure of
the Toughness of the material.
For the samples tested in compression use
the same procedure to convert the raw data into stress and strain and plot
a stress-strain curve. The initial slope of this curve is Youngs modulus. Does
the value measured in compression agree with the value obtained from the tensile
tests? What happens to the stress-strain behavior when the sample buckles?
Determine the buckling threshold and compare your measured value to that
computed using Euler buckling models. Which model best fits your data? For these
compression samples, compute the area under the stress-strain curve. This
is the work required to deform the tube to its final shape.
How do
your measurements relate to things you would need to know if you were designing
a bicycle? |
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