Exam 2 Flashcards
Which of the materials below has the lowest electrical resistivity?
polypropylene, copper, titanium dioxide, silicon
copper
A pair of cation vacancy-anion vacancy is called:
Schottky defect
Which of the following is a 2D defect?
Frenkel defect, Schottky defect, edge dislocation, screw dislocation, grain boundary
grain boundary
Which one of the following statements is true?
adding Ni to Cu increases its resistivity
adding Ni to Cu decreases its resistivity
adding Ni to Cu does not affect its resistivity
adding Ni to Cu increases its resistivity
As temperature increases, the diffusion coefficient D:
increases
Which one of the following statements is true for the non steady-state diffusion:
both concentration and flux do not depend on time
concentration depends on time but flux does not
concentration does not depend on time but flux does
both concentration and flux depend on time
both concentration and flux depend on time
Which one of the following statements is true for the steady-state diffusion:
both concentration and flux do not depend on time
concentration depends on time but flux does not
concentration does not depend on time but flux does
both concentration and flux depend on time
both concentration and flux do not depend on time
C(o) in the solution of the Fick’s Second Law fo non steady-state condition is:
initial concentration inside a sample
initial concentration at the samples’ surface at time 0
final concentration at the sample’s surface
final concentration inside the sample
initial concentration inside a sample
Poisson’s ration is defined as:
ratio of a lateral strain over a tensile strain
ratio of a tensile strain over a lateral strain
ratio of a lateral strain over a tensile strain multiplied by -1
ratio of a tensile strain over a lateral strain multiplied by -1
ratio of a lateral strain over a tensile strain multiplied by -1
For a given material with a tensile strength is 480 MPa and a yield strength is 240 MPa. You need to use this material in a device with the factor of safety N=3. What would be the maximum working load allowed for this material? 160 MPa 240 MPa 80 MPa 480 MPa
80 MPa
As the impurity concentration in solid solution of a metal is increased, the tensile strength:
decreases
increases
remains unchanged
increases
As %CW in metallic alloy is increased
yield strength increases and ductility decreases
As %CW in metallic alloy is increased
yield strength increases and tensile strength increases
A metal having a crystal structure with many operable slip systems will be relatively:
ductile
brittle
ductile
What type of point defects do you know?
vacancies, interstitials, substitutional
How does the number of vacancies change with increasing temperature?
increases
Two metals, A and B; both metals have FCC crystal structures. Metal A has an atomic radius of 0.3 nm and metal B has an atomic radius of 0.12 nm. Can these two metals form a complete substitution solid solution ( 0 % -100 % concentration)?
no, the radius is > 15%
Two metals, A and B. Metal A has FCC and metal B has BCC crystal structure. Metal A has an atomic radius of 0.121 nm and metal B has an atomic radius of 0.122 nm. Can these two metals form a a complete substitution solid solution (0 % -100 % concentration)?
no, they have different crystal structures
T/F: Two metals with similar electronegativity values can form substitutional solution
true
Which of the materials below has the highest electrical conductivity:
silver
silicon
polystyrene
silver
Which of the materials below has the lowest electrical conductivity: iron silicon polyethylene aluminum oxide
polyethylene
If a concentration of impurities increases electrical resistivity of a metal:
increases
If temperature increases electrical conductivity of a metal:
decreases
Which of the following is a (are) 0D defect(s) in ceramics?
Schottky defect, screw dislocation, Frenkel defect, grain boundary, edge dislocation
Schottky defect and Frenkel defect
A cation vacancy-cation interstitial pair is called:
Frenkel defect
Which of the following is a (are) 1D defect(s)? Frenkel defect grain boundary Schottky defect edge dislocation screw dislocation
edge dislocation and screw dislocation
For a screw dislocation Burgers vector is:
parallel to the dislocation line
For an edge dislocation Burgers vector is:
perpendicular to the dislocation line
Which of the following is a (are) 3D defect(s)?
terrace, kink, Frenkel defect, edge dislocation, adatom, ledge, screw dislocation, grain boundary, Schottky defect
terrace, kink, adatom, and ledge
If G-number is larger the corresponding grain size is:
smaller
Which one of the following statements is true. Take into account that the Nitrogen is an interstitial impurity in Fe, whereas Cr is a substitutional impurity
- Diffusion coefficient for N in Fe at 700°C is higher than that for Cr in Fe at 700°C
- Diffusion coefficient for N in Fe at 700°C is lower than that for Cr in Fe at 700°C
- Diffusion coefficient for N in Fe at 700°C is equal/similar to that for Cr in Fe at 700°C
diffusion coefficient for N in Fe at 700°C is higher than that for Cr in Fe at 700°C
You have a concentration gradient dB(x)/dx. What is the direction of the flux of species B:
from high values of B to low values of B
Increasing activation energy Q(D) in expression for diffusion coefficient, D,
decreases D
T/F: The first Fick’s low postulates a linear dependency between concentration gradient and flux
true
What type(s) of diffusion do you know?
vacancy diffusion and interstitial diffusion
Engineering stress is calculated by
dividing applied load by initial cross-section area of a sample
Engineering strain is
relative (to the original length) change of the sample’s elongation
For two samples (one of larger and one of smaller initial cross-section area) made of the same material if the applied stress is the same
the resulting strain will be the same
Poisson’s ratio for the majority of the materials lies within the following range
from .25 to .5
Which material from the list below has a lowest Young’s modulus?
polyester, Cu alloys, carbon fibers, molybdenum, magnesium
polyester
The σ(y) value marked on the plot is called
yield strength
Young’s modulus is defined as
ratio of stress over strain
How elastic modulus calculated using true stress and strain related to the one calculated using engineering values
different, but almost the same for small strain value
The direction of motion of a screw dislocation’s line is ______ to the direction of an applied shear stress.
perpendicular
The process by which plastic deformation is produced by dislocation motion that is called ________.
slip
For a particular crystal structure, the slip direction is the direction in the slip plane having the
highest linear density
As the impurity concentration in solid solution of a metal is increased, the tensile strength
increases
T/F: After an edge dislocation has passed through some region of a crystal, the atomic arrangement of that region is disordered
false
A metal having a crystal structure with many operable slip systems will be relatively
ductile
Relative to the direction of an applied shear stress, the direction of motion of an edge dislocation’s line is ______.
parallel
T/F: Reducing the grain size of a metal increases its yield strength
true
T/F: Reducing the grain size of a metal increases its ductility
false
For a particular crystal structure, the slip plane is the plane having
the highest planar density
Which of the following correctly represents, for an amorphous polymer, the sequential change in mechanical state with increasing temperature?
glass, then transition to rubbery solid, then transition to viscous liquid
How does the decrease in molecular weight influence a tensile modulus of a polymer?
no direct influence
How does the decrease in molecular weight influence a tensile strength of a polymer?
decreases tensile strength
