Matsci Exam 3- HW Questions and Answers
According to the tensile test graph shown, which of the following statements is
TRUE?
a). The yield strength is ~ 60 MPa and the ultimate tensile strength is ~ 170 MPa.
b). The ultimate tensile strength is ~ 170 MPa and the Young's modulus is ~60
GPa.
c). The ultimate tensile strength is ~ 170 MPa and the Young's modulus cannot be
estimated.
d). The fracture strength is ~ 150 MPa and the ultimate tensile strength is ~ 150
MPa. - ANS-The ultimate tensile strength is ~ 170 MPa and the Young's modulus is
~60 GPa.
Concrete can take up to ~26 MPa of compressive stress. The density of concrete is
about 2.2 g/cm³. What is the height limit (in the unit of km) of a vertical concrete
pillar to avoid exceeding the maximum compressive stress due to its own weight?
For the acceleration of gravity use g=9.8 m/s².
a). 1.57
b) 1.33
c). 1.45
d). 1.21 - ANS-1.21
A polycrystalline copper sample is loaded past its yield point to 1.5% tensile strain,
then the load is released. We call this sample the "pre-stretched sample." We now
reload this pre-stretched sample to a 1.0% tensile strain. Which of the following
statements is correct?
a). The new yield strength of the pre-stretched sample is higher than that of the
original sample.
b). The yield strengths will be the same in both cases.
c). The new yield strength of the pre-stretched sample is lower than that of the
original sample.
d). Copper is brittle and cannot be strained a second time. - ANS-The new yield
strength of the pre-stretched sample is higher than that of the original sample
Figure shown is a stress vs. strain curve for a FCC metal specimen. The figure on
the right is magnified to show the low strain behavior. Estimate the yield stress
(σYS) in MPa using the 0.2% offset method.
a). 75
b). 68
c). 55
d). 60 - ANS-68
, Figure shown is a stress vs. strain curve for a cylindrical FCC metal. The figure on
the right is magnified to show the low strain behavior. Estimate the elastic modulus
(E) in GPa?
a). 60
b). 0.103
c). 75
d). 7.5 - ANS-75
The stress-strain curves A-C below were obtained from different polymers in
uniaxial tension at room temperature (25˚C). Which of the following is true
a). The relative order of elastic moduli are A ~ B < C
b). The elastic moduli of A and B are almost identical with a value of ~3 GPa
c). The elastic moduli of A and B are almost identical with a value of ~300 MPa
d). A and B have elastic moduli of ~62 MPa and ~35 MPa, respectively. - ANS-The
elastic moduli of A and B are almost identical with a value of ~300 MPa
Which of the following statements is TRUE?
a). Toughness is directly proportional to the yield stress.
b). Toughness can be obtained from the area under the elastic portion of the stress
strain curve.
c). Toughness can be obtained from the area under the interatomic energy versus
distance curve.
d). Toughness can be obtained from the area under the entire stress strain curve. -
ANS-Toughness can be obtained from the area under the entire stress strain curve
If 100.0 MPa is applied along [001] in a FCC crystal, the resolved shear stress
magnitude for the slip system (in MPa) is
a). 244.9
b). 57.7
c). 70.7
d). 40.8 - ANS-40.8
For a single crystal FCC metal, under uniaxial tension test along its [124] direction,
the yield point is 150 MPa. The slip system is . Calculate the critically resolved
shear stress of this particular metal, in units of MPa.
a). 73
b). 80
c). 150
d). 66
e). 309.0 - ANS-73
In the figure shown, a tensile stress, σ, is applied to a single crystal BCC specimen
45° from the normal to the slip plane and 60° from the slip direction. The critical
According to the tensile test graph shown, which of the following statements is
TRUE?
a). The yield strength is ~ 60 MPa and the ultimate tensile strength is ~ 170 MPa.
b). The ultimate tensile strength is ~ 170 MPa and the Young's modulus is ~60
GPa.
c). The ultimate tensile strength is ~ 170 MPa and the Young's modulus cannot be
estimated.
d). The fracture strength is ~ 150 MPa and the ultimate tensile strength is ~ 150
MPa. - ANS-The ultimate tensile strength is ~ 170 MPa and the Young's modulus is
~60 GPa.
Concrete can take up to ~26 MPa of compressive stress. The density of concrete is
about 2.2 g/cm³. What is the height limit (in the unit of km) of a vertical concrete
pillar to avoid exceeding the maximum compressive stress due to its own weight?
For the acceleration of gravity use g=9.8 m/s².
a). 1.57
b) 1.33
c). 1.45
d). 1.21 - ANS-1.21
A polycrystalline copper sample is loaded past its yield point to 1.5% tensile strain,
then the load is released. We call this sample the "pre-stretched sample." We now
reload this pre-stretched sample to a 1.0% tensile strain. Which of the following
statements is correct?
a). The new yield strength of the pre-stretched sample is higher than that of the
original sample.
b). The yield strengths will be the same in both cases.
c). The new yield strength of the pre-stretched sample is lower than that of the
original sample.
d). Copper is brittle and cannot be strained a second time. - ANS-The new yield
strength of the pre-stretched sample is higher than that of the original sample
Figure shown is a stress vs. strain curve for a FCC metal specimen. The figure on
the right is magnified to show the low strain behavior. Estimate the yield stress
(σYS) in MPa using the 0.2% offset method.
a). 75
b). 68
c). 55
d). 60 - ANS-68
, Figure shown is a stress vs. strain curve for a cylindrical FCC metal. The figure on
the right is magnified to show the low strain behavior. Estimate the elastic modulus
(E) in GPa?
a). 60
b). 0.103
c). 75
d). 7.5 - ANS-75
The stress-strain curves A-C below were obtained from different polymers in
uniaxial tension at room temperature (25˚C). Which of the following is true
a). The relative order of elastic moduli are A ~ B < C
b). The elastic moduli of A and B are almost identical with a value of ~3 GPa
c). The elastic moduli of A and B are almost identical with a value of ~300 MPa
d). A and B have elastic moduli of ~62 MPa and ~35 MPa, respectively. - ANS-The
elastic moduli of A and B are almost identical with a value of ~300 MPa
Which of the following statements is TRUE?
a). Toughness is directly proportional to the yield stress.
b). Toughness can be obtained from the area under the elastic portion of the stress
strain curve.
c). Toughness can be obtained from the area under the interatomic energy versus
distance curve.
d). Toughness can be obtained from the area under the entire stress strain curve. -
ANS-Toughness can be obtained from the area under the entire stress strain curve
If 100.0 MPa is applied along [001] in a FCC crystal, the resolved shear stress
magnitude for the slip system (in MPa) is
a). 244.9
b). 57.7
c). 70.7
d). 40.8 - ANS-40.8
For a single crystal FCC metal, under uniaxial tension test along its [124] direction,
the yield point is 150 MPa. The slip system is . Calculate the critically resolved
shear stress of this particular metal, in units of MPa.
a). 73
b). 80
c). 150
d). 66
e). 309.0 - ANS-73
In the figure shown, a tensile stress, σ, is applied to a single crystal BCC specimen
45° from the normal to the slip plane and 60° from the slip direction. The critical
