Lab 2 Tensile Test
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Transcript of Lab 2 Tensile Test
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ENGR 271
Materials Science Laboratory
Spring 2015
LAB 2 TENSILE TEST
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ENGR 271
2
Stress-Strain Testing
Typical tensile test machine
Adapted from Fig. 6.3, Callister & Rethwisch 8e. (Fig. 6.3 is taken from H.W. Hayden, W.G.
Moffatt, and J. Wulff, The Structure and Properties of Materials, Vol. III, Mechanical Behavior, p.
2, John Wiley and Sons, New York, 1965.)
specimenextensometer
Typical tensile specimen
Adapted from Fig. 6.2, Callister & Rethwisch 8e. .
gaugelength
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ENGR 271
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ENGR 271
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ENGR 271
Linear Elastic Properties
Modulus of Elasticity, E:
(also known as Young's modulus)
Hooke's Law:
s = E e s
Linear-
elastic
E
e
F
Fsimpletensiontest
Units:
E: [GPa] or [psi]
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ENGR 271
Stress at which noticeable plastic deformation has occurred.
when ep = 0.002
Yield Strength, sy by 0.2% offset method
sy = yield strength
Note: for 2 inch sample
e = 0.002 = z/z
z = 0.004 in
Adapted from Fig. 6.10 (a), Callister & Rethwisch 8e. .
tensile stress, s
engineering strain, e
sy
ep = 0.002
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ENGR 271
Plastic tensile strain at failure:
Adapted from Fig. 6.13, Callister & Rethwisch 8e. .
Ductility
Another ductility measure: 100xA
AARA%
o
fo-
=
x 100L
LLEl%
o
of-
=
Engineering tensile strain, e
Engineering
tensile
stress, s
smaller %El (Brittle)
larger %El (Ductile)Lf
AoAfLo
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ENGR 271
Tensile Strength, TS
Adapted from Fig. 6.11, Callister & Rethwisch 8e. .
sy
strain
Typical response of a metal
F = fracture or
ultimate
strength
Neck acts
as stress
concentrator
engin
eeri
ng
stre
ss
engineering strain
Maximum stress on engineering stress-strain curve.
TS = Tensile
Strength
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ENGR 271
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ENGR 271
Why Use True Stress & Strain
Adapted from Fig. 6.11, Callister & Rethwisch 8e.
Specimen area is decreasing
Stress calculated on instantaneous area
is increasing
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ENGR 271
True Stress & Strain True Stress
True Strain
iT AF=s
oiT ln=e ee
ess
=
=
1ln
1
T
T
Adapted from Fig. 6.16, Callister & Rethwisch 8e.
Valid up to
point M
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ENGR 271
LAB 2 TENSILE TEST REQUIREMENTS
Fill out the table, show
all calculations, graphsExperimental Theoretical % Error
Modulus of Elasticity
Yield Strength
Tensile Strength
Fracture Strength
Ductility
Toughness
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ENGR 271
LAB 2 TENSILE TEST REQUIREMENTS
Plot the Engineering vs. True Stress and Strain Diagram.
Comment on your results and include the discussion points
below to your report.
Why does it not make much sense to calculate true stress and true strain using the equations given in the
lab notes after the maximum load is reached?
In general, A36 can be categorized as a ductile material, and cast iron as a brittle material. Based on the results of
the tensile tests, discuss the differences between the
ductile and brittle materials in terms of the overall
deformation and fracture behavior.