Exam 2

Question 1

Which of the materials below has the lowest electrical resistivity?
polypropylene, copper, titanium dioxide, silicon

Answer 1

copper

Question 2

A pair of cation vacancy-anion vacancy is called:

Answer 2

Schottky defect

Question 3

Which of the following is a 2D defect?

Frenkel defect, Schottky defect, edge dislocation, screw dislocation, grain boundary

Answer 3

grain boundary

Question 4

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

Answer 4

adding Ni to Cu increases its resistivity

Question 5

As temperature increases, the diffusion coefficient D:

Answer 5

increases

Question 6

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

Answer 6

both concentration and flux depend on time

Question 7

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

Answer 7

both concentration and flux do not depend on time

Question 8

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

Answer 8

initial concentration inside a sample

Question 9

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

Answer 9

ratio of a lateral strain over a tensile strain multiplied by -1

Question 10

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

Answer 10

80 MPa

Question 11

As the impurity concentration in solid solution of a metal is increased, the tensile strength:
decreases
increases
remains unchanged

Answer 11

increases

Question 12

As %CW in metallic alloy is increased

Answer 12

yield strength increases and ductility decreases

Question 13

As %CW in metallic alloy is increased

Answer 13

yield strength increases and tensile strength increases

Question 14

A metal having a crystal structure with many operable slip systems will be relatively:
ductile
brittle

Answer 14

ductile

Question 15

What type of point defects do you know?

Answer 15

vacancies, interstitials, substitutional

Question 16

How does the number of vacancies change with increasing temperature?

Answer 16

increases

Question 17

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)?

Answer 17

no, the radius is > 15%

Question 18

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)?

Answer 18

no, they have different crystal structures

Question 19

T/F: Two metals with similar electronegativity values can form substitutional solution

Answer 19

true

Question 20

Which of the materials below has the highest electrical conductivity:
silver
silicon
polystyrene

Answer 20

silver

Question 21

Which of the materials below has the lowest electrical conductivity:
iron
silicon
polyethylene
aluminum oxide

Answer 21

polyethylene

Question 22

If a concentration of impurities increases electrical resistivity of a metal:

Answer 22

increases

Question 23

If temperature increases electrical conductivity of a metal:

Answer 23

decreases

Question 24

Which of the following is a (are) 0D defect(s) in ceramics?

Schottky defect, screw dislocation, Frenkel defect, grain boundary, edge dislocation

Answer 24

Schottky defect and Frenkel defect

Question 25

A cation vacancy-cation interstitial pair is called:

Answer 25

Frenkel defect

Question 26

``` Which of the following is a (are) 1D defect(s)? Frenkel defect grain boundary Schottky defect edge dislocation screw dislocation ```

Answer 26

edge dislocation and screw dislocation

Question 27

For a screw dislocation Burgers vector is:

Answer 27

parallel to the dislocation line

Question 28

For an edge dislocation Burgers vector is:

Answer 28

perpendicular to the dislocation line

Question 29

Which of the following is a (are) 3D defect(s)? | terrace, kink, Frenkel defect, edge dislocation, adatom, ledge, screw dislocation, grain boundary, Schottky defect

Answer 29

terrace, kink, adatom, and ledge

Question 30

If G-number is larger the corresponding grain size is:

Answer 30

smaller

Question 31

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

Answer 31

diffusion coefficient for N in Fe at 700°C is higher than that for Cr in Fe at 700°C

Question 32

You have a concentration gradient dB(x)/dx. What is the direction of the flux of species B:

Answer 32

from high values of B to low values of B

Question 33

Increasing activation energy Q(D) in expression for diffusion coefficient, D,

Answer 33

decreases D

Question 34

T/F: The first Fick's low postulates a linear dependency between concentration gradient and flux

Answer 34

true

Question 35

What type(s) of diffusion do you know?

Answer 35

vacancy diffusion and interstitial diffusion

Question 36

Engineering stress is calculated by

Answer 36

dividing applied load by initial cross-section area of a sample

Question 37

Engineering strain is

Answer 37

relative (to the original length) change of the sample's elongation

Question 38

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

Answer 38

the resulting strain will be the same

Question 39

Poisson's ratio for the majority of the materials lies within the following range

Answer 39

from .25 to .5

Question 40

Which material from the list below has a lowest Young’s modulus? polyester, Cu alloys, carbon fibers, molybdenum, magnesium

Answer 40

polyester

Question 41

The σ(y) value marked on the plot is called

Answer 41

yield strength

Question 42

Young's modulus is defined as

Answer 42

ratio of stress over strain

Question 43

How elastic modulus calculated using true stress and strain related to the one calculated using engineering values

Answer 43

different, but almost the same for small strain value

Question 44

The direction of motion of a screw dislocation's line is ______ to the direction of an applied shear stress.

Answer 44

perpendicular

Question 45

The process by which plastic deformation is produced by dislocation motion that is called ________.

Answer 45

slip

Question 46

For a particular crystal structure, the slip direction is the direction in the slip plane having the

Answer 46

highest linear density

Question 47

As the impurity concentration in solid solution of a metal is increased, the tensile strength

Answer 47

increases

Question 48

T/F: After an edge dislocation has passed through some region of a crystal, the atomic arrangement of that region is disordered

Answer 48

false

Question 49

A metal having a crystal structure with many operable slip systems will be relatively

Answer 49

ductile

Question 50

Relative to the direction of an applied shear stress, the direction of motion of an edge dislocation's line is ______.

Answer 50

parallel

Question 51

T/F: Reducing the grain size of a metal increases its yield strength

Answer 51

true

Question 52

T/F: Reducing the grain size of a metal increases its ductility

Answer 52

false

Question 53

For a particular crystal structure, the slip plane is the plane having

Answer 53

the highest planar density

Question 54

Which of the following correctly represents, for an amorphous polymer, the sequential change in mechanical state with increasing temperature?

Answer 54

glass, then transition to rubbery solid, then transition to viscous liquid

Question 55

How does the decrease in molecular weight influence a tensile modulus of a polymer?

Answer 55

no direct influence

Question 56

How does the decrease in molecular weight influence a tensile strength of a polymer?

Answer 56

decreases tensile strength