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Flashcards in Exam 2 Deck (56):
1

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

copper

2

A pair of cation vacancy-anion vacancy is called:

Schottky defect

3

Which of the following is a 2D defect?
Frenkel defect, Schottky defect, edge dislocation, screw dislocation, grain boundary

grain boundary

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

adding Ni to Cu increases its resistivity

5

As temperature increases, the diffusion coefficient D:

increases

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

both concentration and flux depend on time

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

both concentration and flux do not depend on time

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

initial concentration inside a sample

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

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

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

80 MPa

11

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

increases

12

As %CW in metallic alloy is increased

yield strength increases and ductility decreases

13

As %CW in metallic alloy is increased

yield strength increases and tensile strength increases

14

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

ductile

15

What type of point defects do you know?

vacancies, interstitials, substitutional

16

How does the number of vacancies change with increasing temperature?

increases

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)?

no, the radius is > 15%

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)?

no, they have different crystal structures

19

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

true

20

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

silver

21

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

polyethylene

22

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

increases

23

If temperature increases electrical conductivity of a metal:

decreases

24

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

25

A cation vacancy-cation interstitial pair is called:

Frenkel defect

26

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

27

For a screw dislocation Burgers vector is:

parallel to the dislocation line

28

For an edge dislocation Burgers vector is:

perpendicular to the dislocation line

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

terrace, kink, adatom, and ledge

30

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

smaller

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

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

32

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

33

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

decreases D

34

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

true

35

What type(s) of diffusion do you know?

vacancy diffusion and interstitial diffusion

36

Engineering stress is calculated by

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

37

Engineering strain is

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

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

the resulting strain will be the same

39

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

from .25 to .5

40

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

polyester

41

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

yield strength

42

Young's modulus is defined as

ratio of stress over strain

43

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

44

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

perpendicular

45

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

slip

46

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

highest linear density

47

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

increases

48

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

false

49

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

ductile

50

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

parallel

51

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

true

52

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

false

53

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

the highest planar density

54

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

55

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

no direct influence

56

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

decreases tensile strength