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Materials > Jan Exam > Flashcards

Jan Exam Flashcards

1
Q

What is the equation for secondary creep strain rate?

A

Strain rate = K*sress^n *e^(-Q/RT)

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2
Q

What temperature does strain rate occur?

A

T>0.4Tm

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3
Q

How can you find Q? Graphically.

A

Gradient of ln(strain rate) v 1/T
T in Kelvin
Gradient = -Q/R

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4
Q

How can you find n? Graphically

A

Gradient of ln(strain rate) v ln(stress)

Gradient = n

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5
Q

What is Larson Miller Parameter used for?

A

Extrapolation

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6
Q

What is the equation for LMP?

A

LMP = T(C+logtr)

Where tr = rupture lifetime (in hours)
C normally equals 20

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7
Q

How do you find LMP?

A

From a graph, tr can then be calculated from it.

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8
Q

How is creep strain related to time?

A

Strain = Strain rate * time

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9
Q

Is creep strain total strain?

A

NOOO!
Total strain = creep strain + steady state/instantaneous/primary

Normally given

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10
Q

How would i take 1.5x10^6 as a strain rate?

A

Make it 0.15x10-7 and use that value on the graph.

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11
Q

What type of brackets are used for directions?

A

Square for individual, triangular for family

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12
Q

What brackets are used for planes?

A

circle for individual and curved for family

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13
Q

How do you find interceptions of planes?

A

Planes given in miller indices,
Interception = 1/miller indices.
Note: if infinite then it doesnt touch that axis.

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14
Q

What is linear density?

A

Number of atoms centred on vector/length of vector

Note: number means throughout whole of cube in that direction.

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15
Q

What is planar density?

A

Number of atoms centred on plane/ Area of plane

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16
Q

How is a related to r in BCC

A

root3 a = 4r

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17
Q

How is a related to r in FCC

A

root2 a = 4r

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18
Q

What is the atomic packing factor?

A

Volume of atoms in cell / Volume of cell

Note: atoms volume = 4/3 Pi r^2
Volume of cell = a^3

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19
Q

What is the equation for theoretical density?

A

density = Number of atmos * Atomic mass / Volume of cell * Avogadros number

Note: number of atoms in FCC = 4 BCC=2
Avogadros Number = 6.02x10^23

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20
Q

What wt%C do Cast Irons have?

A

2.14 - 4.5% (after steels)

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21
Q

What are the types of cast iron?

A

Gray, nodular, white, malleable, compact graphite

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22
Q

How do you get pearlitic maleable cast iron?

A

Fast cooled hot white cast iron.

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23
Q

How do you get Ferritic maleable cast iron?

A

Slow cooled hot white cast iron

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24
Q

What does higher damping capacity do?

A

Reduce chatter

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25
Q

What type of castings are there?

A

Sand, Die, Investment, Continuous, Fabrication

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26
Q

What Aluminium alloys are heat treatable?

A

2, 6, 7

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27
Q

What Aluminium alloys are Strain hardened?

A

1, 3, 5, 8

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28
Q

What is precipitation hardening also called?

A

Age hardening

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29
Q

What is strength?

A

Max load at failure, highest stress

30
Q

What is ductility?

A

Ability to deform

31
Q

What is Hardness?

A

Resistance to deformation, indented test

32
Q

What is stiffness?

A

Resistance to elastic deformation, stress/strain Youngs Modulus

33
Q

What is the Ultimate strength?

A

Peak on curve before necking

34
Q

How do you find the yield if it is unclear?

A

0.2% straight line same gradient

35
Q

What is the area under a stress strain graph?

A

Toughness (impact energy that can be absorbed)

36
Q

What is poissons ratio?

A

v = -lateral strain / logitudinal strain

= -delta diameter/diameter. / delta length/length.

37
Q

What is bulk modulus?

A

K
To do with pressures on object
P=-K deltaV / V

38
Q

What is shear modulus?

A

G
Torsion
torque = Gy

Where y = displaced angle

39
Q

How is poissions ratio related to other moduli?

A

V = E/2G - 1

40
Q

How is ductility measured?

A

Strain at failure
%EL = Lf - Lo /Lo

Or same with areas

41
Q

What is engineering stress?

A

Original area used

42
Q

What are point defects?

A

0D

Vacancies, Interstitials, Substitutionals, Frenkel, Shottky

43
Q

What are line defects?

A

1D

Dislocations (screw,Edge)

44
Q

What are planar defects?

A

Grain boundries, Stacking falts

45
Q

What are bulk defects?

A

Pores, inclusions, cracks

46
Q

Are defects useful?

A

They give a material its mechanical properties
So YEA!
always in materials

47
Q

What is the AISI - SAE system?

A

XYWZ

where X = group of carbon steel
Y = Amount of alloying element
WZ = Carbon concentration (20 = 0.2%)

48
Q

What are these parts of a phase diagram called?

alpha, gamma, Fe3C, Fe3c + alpha

A

In order,

Ferrite, Austenite, Cemetite, Pearlite

49
Q

What are the 2 phase diagram reactions and what are they?

A

Eutectoid ( gamma - alpha +Fe3C)

Eutectic ( Liquid - gamma + Fe3C)

50
Q

at what wt%C is a eutectoid steel?

A

0.76

51
Q

What are the other steels in the phase diagram?

A

Hypoeutectiod, eutectoid, hypereutectoid

52
Q

What are the WT%C of ferrite and cementite?

A

0.02% and 6.7%

53
Q

How do you use the lever rule?

A

Amount of LHS weighting = RHS / Total length
Amount of RHS weighting = LHS / Total length

Limits are 0.02 for ferrite, 0.76 (proutectiod) austenite, 6.7 cementite

54
Q

What are the compositions of the following microstructures? Hypoeutectiod, eutectoid, hypereutectoid

A

ferrite + Prelite
100% pearlite
cementite + pearlite

55
Q

How do you find the composition of each phase?

A

draw straight line horizontally to the end of each phase, these will give you the wt% of one element, use this to find the other.

56
Q

How is the strain energy release rate calculated?

A

G = stresspia / E

a = half the length of the crack

57
Q

How do you calculate the critical stress?

A

= (2Eys/pi*a)^1/2

where ys = specific surface energy

58
Q

How do you calculate the fracture toughness?

A

K = Ystressroot(pi*a)

if K > Critical toughness then it will fail. (critical toughness determined using critical strength)

Y= material constant.

59
Q

How do you produce matensite?

A

Quenching: heating to above recrystalisation temp and cooled rapidly in water or oil.

It can then be temered to regain ductiity by heating to below recrystalisation temp and cooled slowly at room temp

60
Q

What will Austenite turn into when cooled at different rates? From a non equilibrium phase digram.

A 
Slow = Pearlite
Medium = Bainite
Fast = Martensite
61
Q

How do you calculate the stress concentration factor?

A

Kt = (1 + 2a/b)
Measure of how much the stress is amplified
Where a = width and b = height of hole/crack

62
Q

What to do when given t bars with fillet radius (stress concentrators)

A

find r/d,
look at graph to find Kt for given D/d (may need to interpolate)
finds stress using smaller d and force
Max stress = SCF * stress

63
Q

What is the graph for cyclic loading?

A

Stress amplitude vs cycles to failure

64
Q

How do you calculate the amplitude on cyclic loading?

A

half of (max stress - min stress)

65
Q

How do you find mean stress?

A

max stress + min stress / 2

66
Q

What type of question could we get for cyclic loading?

A

To find max and min stress,

Find equations for them using mean and amplitude,
Solve simultaneously

67
Q

3 notes for phase diagrams

A

always give compositions of both elements in phase
when pre eutectic, phase grows in grain boundries (give compositions of these phases too)
Always draw straight line to either side if mixed phase. Useful for lever rule and wt%

68
Q

What are the wt%C of the following metals?

Wrought Iron, Steel, Cast Iron

A

<6.7

69
Q

How do you calculate the coefficient of thermal expansion?

A

strain = Alpha(T2-T1)

70
Q

What is the bond energy and how do other factors change as it increases?

A

The energy to create or break a bond between atoms.

As Bond energy increases:
Melting temp increases, Coef of thermal exp decreases, Elastic modulus increases

71
Q

What is the Hall-Patch Equation?

A

Yield strength = Stress. + Ky*d^-0.5

Where stress. and Ky are material constants
d = average grain diameter

Materials (2 decks)

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