ES230
Lesson
9/
10
: Laboratory Materials Testing
L
ESSON
9/
10
–
L
ABORATORY
M
ATERIALS
T
ESTING
Lab T
i
me:
by arrangement
L
ESSON
O
BJECTIVES
1.
Compute or estimate
the elastic modulus, yield strength (if applicable), ultimate strength,
maximum strain (AKA,
Percentage Elongation or Contraction), and toughness of engineering materials from experimental data.
2.
Distinguish
between material failures such as the crushing of concrete in compression or the yielding/fracture of steel in
tension an
d non

material failures such as occurs in buckling or local buckling of a long and slender compression member.
3.
Compare
the
strengths of steel, aluminum, wood, and concrete.
4.
Describe
the effect of length
on
buckling
load.
R
EADING
:
Philpot Chapter 3.
TESTS
You will perform the following tests.
Tension Tests
1.
Hot

rolled Grade 50 steel in tension
2.
Aluminum 6061 specification, in tension
3.
Concrete in tension
Compression Tests
4.
Wood (
various species
) in compression
5.
Concrete in compression
Buckling Tests
6.
Test 4
different lengths of 1/8”x2”
Grade 50
steel flat in buckling (compression)
Bolt
Tests
7.
Test 3/8” diameter Grade 2 Steel Bolts in Shear
8.
Test 3/8” diameter Grade 2 Steel Bolts in Tension
H
OMEWORK
:
D
UE
N
EXT
W
EDNESD
AY
1.
Submit
your raw notes from the lab:
dimensions, loads, readings
. Unlike other aspects of the assignment, presentation
does not count
for raw data
because it is understood that the data was taken in the lab.
Accuracy
and completeness are
important, but neatness will not count
.
Be sure to re
cord:
Title for the test, cross

sectional dimensions, units used, all loads, all deformations
Graphs
and Computations.
All graphs must be made to scale, must give the units, and must provide a sufficient title that
adequately describes the test that was
performed so that it could be understandable by someone who did not witness the test.
A
brief written description of the test should also be included on the graphs.
2.
Bar Graph #1. Make a bar graph (you may use Excel) that compares the
ultimate strengths o
f Grade 50 Steel
(tension)
,
6061 Aluminum (tension), Douglas Fir (compression), and
Concrete
(tension and compression)
.
Use units of ksi
3.
X

Y Plot #1. Plot the stress

strain curve
for Grade 50
Steel
and 6061 Aluminum
up to a strain of 0.010
in/in), placin
g
strain on the x

axis and strain on the y

axis.
On the graph
, label the values for t
he following: Elastic Modulus and
Yield
Stress
.
Clearly show how the elastic moduli were determined by a
best

fit of the linear portion
of the curves.
4.
X

Y Plot #2. Plo
t the stress

strain curve for Grade 50 Steel and 6061 Aluminum
for their full ranges
(including the period
during which the divider and ruler were used for measurement), placing strain on the x

axis and strain on the y

axis. On
the graph, label the values
for the following: Elastic Modulus, Yield Stress, Ultimate Stress, % elongation, and the
toughness (
refer to notes from lab for more information
). Note that toughness is simply the area under the stress

strain
curve and can be found as the sum of trapez
oidal areas: show your work for this (hint: it is easy to use the data in Excel
to sum trapezoidal areas).
5.
X

Y Plot #3
. Plot the stress

strain curve
s
for Concrete
and Wood
for
their
full range. On the graph, label the values for
the following
: Elastic
Modulus
, Ultimate Stress
(note: concrete and wood do not “yield”. Only metals yield).
Because
both materials are non

linear, determine the elastic modulus as the slope of the line between the origin and a point
corresponding with 40% of the ultimate lo
ad.
6.
X

Y Plot #4.
Plot Ultimate Stress (y

axis) versus Length
(x

axis)
for the buckling specimens. Comment: at zero length,
would the plot approach the
previously determined yield strength of the material?
7.
Compute the sh
ear stre
ngth and tensile strength
of the Grade 2 Steel bolts and determine the ratio of shear strength/tensile
strength (note: this is a constant value for all ductile metals).
Comparisons
Provide written answers to the following:
1.
How many times
stiffer is Steel, compared with Aluminum
(as measured by the elastic modulus)?
2.
Which is more ductile, Steel or Aluminum?
3.
Compare the stiffness (as measured by the elastic modulus) and strength of wood and concrete.
Appendix
Show
examples of
all intermediate calculations (example: the determinati
on of stresses and strains, based on the experimental loads
and deformations)
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