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2021 Sem2 > AMME1362 > Flashcards

AMME1362 Flashcards

1
Q
  1. What different ways can you classify materials?
A

○ Based on chemical bonds - metallic, ionic, covalent
○ Based on conductivity - insulators, semiconductors, conductors, superconductors
○ Based on applications - structural materials, functional materials, biomaterials
Based on grain number in solid, and size of grain - single crystals, polycrystalline materials, coarse grained materials, ultrafine-grained materials, nanocrystalline materials

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2
Q
  1. Types of chemical bonds
A

metallic, ionic, covalent

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3
Q
  1. Types of conductivity
A

insulators, semiconductors, conductors, superconductors

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4
Q
  1. Ways to categorise by grain no. and size
A

single crystals, polycrystalline materials, coarse grained materials, ultrafine-grained materials, nanocrystalline materials

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5
Q
  1. Compare metals to polymers
A

A polymer is a macromolecular material having a large number of repeating units linked to each other via covalent chemical bonds
metals are either pure elements or alloys. Therefore, they have different chemical and physical properties.
The key difference between polymers and metals is that the polymers are lightweight than the metals. However, metals have a lustrous appearance, and high thermal and electrical conductivity. Moreover, the strength to weight ratio of polymer materials is higher than that of metals. Also, another important difference between polymers and metals is that the metals are highly malleable and ductile whereas most of the polymers are not.

Furthermore, polymers contain repeating units linked by covalent chemical bonds that represent the monomers used in the making of the polymer. But, the pure metals have metal cations and electrons attached to each other via metallic bonds and alloys that contain two or more metals and nonmetals as well. Hence, this is a significant difference between polymers and metals.

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6
Q
  1. What is electrical resistivity
A

a measure of the resisting power of a specified material to the flow of an electric current.

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7
Q
  1. What is porosity in relation to materials
A

Porosity or void fraction is a measure of the void (i.e. “empty”) spaces in a material, and is a fraction of the volume of voids over the total volume, between 0 and 1, or as a percentage between 0% and 100%

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8
Q
  1. Outline the materials selection process
A

Materials Selection Process: Application > Properties > Materials > Processing

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9
Q
  1. What is Poisson’s ratio? What does it determine, what principle is it based on?
A

the ratio of the proportional decrease in a lateral measurement to the proportional increase in length in a sample of material that is elastically stretched.

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10
Q
  1. What is shear modulus, what does it measure and how do you calculate it?
A

The shear modulus is defined as the ratio of shear stress to shear strain.
G= E/(2*[1 +v]), where v is Poisson’s ratio
• A large shear modulus value indicates a solid is highly rigid. In other words, a large force is required to produce deformation. A lot of shear stress is needed to produce strain.
• A small shear modulus value indicates a solid is soft or flexible. Little force is needed to deform it.
One definition of a fluid is a substance with a shear modulus of zero. Any force deforms its surface

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11
Q
  1. What are the common states of stress?
A

Compression, tension, torsion, shear

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12
Q
  1. How does Young’s modulus change in response to temperature?
A

Decreases with increased temperature

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13
Q
  1. What is ductility?
A

In materials science, ductility is defined by the degree to which a material can sustain plastic deformation under tensile stress before failure

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14
Q
  1. What is toughness?
A

the energy needed to break a unit volume of material
- Approximate by area under stress-strain curve

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15
Q
  1. What is resilience?
A

the strain energy per unit volume of stress up to point of yielding (how much strain on each area experiencing stress)
- The ability of a material to store energy for elastic deformation
Ur = yield strength squared divided by 2E

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16
Q
  1. Compare true stress/strain to engineering stress/strain.
A

Engineering stress is the applied load divided by the original cross-sectional area of a material. Also known as nominal stress.
True stress is the applied load divided by the actual cross-sectional area (the changing area with respect to time) of the specimen at that load
Engineering strain is the amount that a material deforms per unit length in a tensile test. Also known as nominal strain.
True strain equals the natural log of the quotient of current length over the original length

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17
Q
  1. What is hardness?
A
  • Measure of resistance to permanently indenting the surface
  • Measured by applying a known force, and then measuring the size of indent after removing the load
  • Increased hardness means - resistance to plastic deformation, or cracking in compression
  • Hardness is tested more frequently as the process is simple and inexpensive, non-destructive, can be approximately converted to other properties (tensile strength), has high spatial resolution
  • Hardness is not a well-defined property, not easy to convert between units of hardness
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18
Q
  1. How do you measure hardness?
A
  • Measured by applying a known force, and then measuring the size of indent after removing the load
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19
Q
  1. What are the mechanical properties you can get from a stress/strain plot?
A

Young’s modulus
•Yield strength at a strain offset of 0.002
•Tensile strength, maximum load
•Change in length under a specific stress
•Ductility
•Elastic strain
•Toughness
•Modulus of resilience

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20
Q
  1. Differentiate ductile and brittle fracture. What about moderately ductile?
A
  • Ductile fracture
    ○ Occurs with plastic deformation
    ○ “clean” fracture, significant necking before fracture
    ○ Fracture will result in one/two pieces, lots of deformation
  • Brittle fracture
    ○ Occurs with little or no plastic deformation, catastrophic, occurs with little warning
    ○ No necking
    ○ Fracture will result in many pieces with little deformation
  • Moderately ductile
    Some necking occurs
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21
Q
  1. Is there a quantifiable level of ductility? Or is it relative to other metals?
A

There is a measurable level: %EL= (Lf-L0)/L0 * 100

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22
Q
  1. Outline the process of moderately ductile fracture?
A
  • Some necking > void nucleation > void growth & linkage (voids join together)
  • End points of cone structure have 45 degree angles - highest stress!
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23
Q
  1. Why is stress concentrated at the external edges of a void?
A

Stress concentrations occur when there are irregularities in the geometry or material of a structural component that cause an interruption to the flow of stress.
The external edges of a void have increased stress as there is less SA to bear the tensile load.
Geometric discontinuities cause an object to experience a localised increase in stress. Examples of shapes that cause stress concentrations are sharp internal corners, holes, and sudden changes in the cross-sectional area of the object as well as unintentional damage such as nicks, scratches and cracks. High local stresses can cause objects to fail more quickly, so engineers typically design the geometry to minimize stress concentrations.

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24
Q
  1. Tutorial concepts - How to calculate stress amplitude, range, min, max, mean
A 
Amplitude = r/2
Range = max - min
mean= (max + min)/2
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25
Q
  1. Tutorial concepts - using a graph to determine no. of cycles for x pressure
A
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26
Q
  1. Where is stress concentration at point of void nucleation?
A

At crack tips/tips of voids

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27
Q
  1. What is the shape of dimples created in ductile materials?
A

Spherical

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28
Q
  1. What is the shape of dimples created in brittle materials
A

Radiated lines/ridges

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29
Q
  1. What is the shape of dimples created in britlte, hard, fine-grained materials?
A

No discernible fracture pattern

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30
Q
  1. What is the shape of dimples created in brittle, amorphous materials?
A

Relatively shiny & smooth surface

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31
Q
  1. Compare intergranular with intragranular
A

ans

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32
Q
  1. Compare qualities of perfect materials with real materials.
A

ans

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33
Q
  1. What is the Griffith crack equation? What does it determine?
A

ans

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34
Q
  1. What happens when you increase the radius of a crack vs increasing radius of crack tip?
A

ans

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35
Q
  1. What are the causes of fatigue?
A

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36
Q
  1. What comprises 90% of mech engineering failures
A

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37
Q
  1. What are the different stress cycles a material can be put under?
A

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38
Q
  1. How do you calculate mean stress?
A

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39
Q
  1. How do you calculate stress range?
A

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40
Q
  1. How do you calculate stress ratio?
A

ans

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41
Q
  1. How do you calculate stress amplitude?
A

stress range/2

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42
Q
  1. How to do you calculate stress ratio?
A

min stress/max stress

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43
Q
  1. What does a stress amplitude curve show
A

ans

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44
Q
  1. What does the fatigue limit mean?
A

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45
Q
  1. What is the mechanism of fatigue?
A

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46
Q
  1. What are the factors that affect the rate of fatigue?
A

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47
Q
  1. What are ways to reduce the risk of fatigue?
A

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48
Q
  1. What are the 3 stages of creep?
A

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49
Q
  1. What are the coefficients of friction?
A

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50
Q
  1. What is adhesive wear?
A

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51
Q
  1. What is abrasive wear?
A

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52
Q
  1. How does lubrication reduce friction?
A

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53
Q
  1. Where is stress concentration at point of void nucleation?
A

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54
Q
  1. What is the shape of dimples created in ductile materials?
A

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55
Q
  1. What is the shape of dimples created in brittle materials?
A

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56
Q
  1. What is the shape of dimples created in britlte, hard, fine-grained materials?
A

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57
Q
  1. What is the shape of dimples created in brittle, amorphous materials?
A

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58
Q
  1. Compare intergranular with intragranular
A

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59
Q
  1. Compare qualities of perfect materials with real materials.
A

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60
Q
  1. What is the Griffith crack equation? What does it determine?
A

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61
Q
  1. What happens when you increase the radius of a crack vs increasing radius of crack tip?
A

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62
Q
  1. What are the causes of fatigue?
A

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63
Q
  1. What comprises 90% of mech engineering failures
A

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64
Q
  1. What are the different stress cycles a material can be put under?
A

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65
Q
  1. How do you calculate mean stress?
A

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66
Q
  1. How do you calculate stress range?
A

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67
Q
  1. How do you calculate stress ratio?
A

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68
Q
  1. How do you calculate stress amplitude?
A

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69
Q
  1. How to do you calculate stress ratio?
A

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70
Q
  1. What does a stress amplitude curve show
A

The behaviour of a material at specified no. of stress cycles

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71
Q
  1. What does the fatigue limit mean?
A

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72
Q
  1. What is the mechanism of fatigue?
A

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73
Q
  1. What are the factors that affect the rate of fatigue?
A

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74
Q
  1. What are ways to reduce the risk of fatigue?
A

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75
Q
  1. What are the 3 stages of creep?
A

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76
Q
  1. What are the coefficients of friction?
A

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77
Q
  1. What is adhesive wear?
A

Generated by the sliding of one solid surface along another syrface

The asperities on mutually opposing surfaces become fused together and are the subsequently ruptured b/c of their relative motion

Asperity = bump on surface that come into contact during wear or friction

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78
Q
  1. What is abrasive wear?
A

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79
Q
  1. Does crystal structure impact mechanical properties?
A

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80
Q
  1. What are the 3 different ways to pack atoms in a material? Describe their features
A

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81
Q
  1. Does non-crystalline = amorphous?
A

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82
Q
  1. What is a unit cell?
A

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83
Q
  1. What is the smallest repetitive volume of a crystal called?
A

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84
Q
  1. Compare the hard sphere unit cell and reduced -sphere unit cell
A

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85
Q
  1. What are lattice parameters?
A

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86
Q
  1. What is the coordination number?
A

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87
Q
  1. What is the atomic packing factor?
A

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88
Q
  1. What is the term for the number of nearest neighbour atoms?
A

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89
Q
  1. ….factor is the vol of atoms in unit cell divided by total until cell volume
A

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90
Q
  1. How many possible crystal systems and lattices are there?
A

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91
Q
  1. Why are metallic crystal structures densely packed?
A

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92
Q
  1. What are the 4 types of metallic crystal structures? Outline their features
A

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93
Q
  1. Compare the layer structures of SC, BCC, FCC and HCP structures
A

ans

94
Q
  1. How do you calculate the length of the body diagonal? Why would you need this?
A

ans

95
Q
  1. How do you calculate the APF of a SC?
A

ans

96
Q
  1. Why is a simple cubic structure rare?
A

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97
Q
  1. Compare the number of atoms per unit cell & unit cell structure in SC, BCC and FCC
A

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98
Q
  1. Hexagonal structure?
A

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99
Q
  1. How do you calculate theoretical density of a unit cell?
A

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100
Q
  1. How do you measure the linear density of a unit cell?
A

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101
Q
  1. How do you measure the planar density?
A

ans

102
Q
  1. How do you calculate crystal directions?
A

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103
Q
  1. What is a family of directions
A

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104
Q
  1. Why is a simple cubic structure rare?
A

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105
Q
  1. How do you find the point coordinates of a structure?
A

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106
Q
  1. How do you find the point directions of a structure?
A

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107
Q
  1. How do you determine the Miller indices for a plane?
A

ans

108
Q
  1. Compare single crystals and polycrystals?
A

Single crystal - repeated atom arrangement extends throughout the entirety without interruption

Properties vary with direction - anisotropic

Polycrystal

Properties may/may not vary with direction

109
Q
  1. How are polycrystals forms?
A

ans

110
Q
  1. What is anisotropy?
A

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111
Q

What is polymorphism/allotropy?

A

ans

112
Q
  1. Outline the types of imperfections
A

ans

113
Q
  1. What are point defects?
A

ans

114
Q
  1. How do you calculate the equilibrium concentration of point defects?
A

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115
Q
  1. Equilibrium vacany concentration
A

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116
Q
  1. What are the differences between edge and screw dislocation?
A

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117
Q
  1. How do dislocations appear in TEM?
A

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118
Q
  1. Are all 3D imperfections undesirable?
A

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119
Q
  1. What are vacancies?
A

ans

120
Q
  1. What are self-interstitials?
A

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121
Q
  1. How do point defects impact lattice energy?
A

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122
Q
  1. How does temperature and activation energy impact the equilibrium concentration of pt defects
A

ans

123
Q
  1. How are island defects formed?
A

ans

124
Q
  1. How are substitutional and interstitial insertions caused?
A

2 outcomes if impurity is added to host

Substitional - atoms of solute replaces parts in solvent plane, pt defects

Interstitial- gaps in solvent plane, plane does not change, pt defects

125
Q
  1. Compare substitutional and interstitial solid solution
A

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126
Q
  1. What is the definition of a defect in relation to crystalline arrays
A

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127
Q
  1. What are the interstitial positions you can find in FCC structure? Compare them. How many are there of each one?
A

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128
Q
  1. How do you calculate the weight % and atom% of a solid? When would you use each?
A

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129
Q
  1. What is a dislocation?
A

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130
Q
  1. Describe the features of edge dislocation
A

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131
Q
  1. Describe the features of screw dislocation
A

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132
Q
  1. How do you count a b vector? Compare the B vector of perfect crystal vs defected sample
A

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133
Q

What are planar defects in solids?

A

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134
Q

How are twin faults formed?

A

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135
Q

How are stacking faults formed?

A

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136
Q

How are volume defects formed?

A

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137
Q
  1. What is meant by dislocation motion?
A

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138
Q
  1. In which direction does dislocation motion occur?
A

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139
Q
  1. Slip direction is the same direction as…
A

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140
Q
  1. What is a slip plane?
A

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141
Q
  1. What is a Frank Read source?
A

ans

142
Q
  1. What is dislocation multiplication?
A

ans

143
Q
  1. How do you calculate dislocation density?
A

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144
Q
  1. What are slip systems
A

ans

145
Q
  1. What are some strategies for strengthening
A

ans

146
Q

Compare edge and slip dislocations

A

ans

147
Q

How do dislocations multiply?

A

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148
Q

Which brackets do you use to describe a slip system

A

{hkl}< uvw >

149
Q

How do you calculate resolved shear stress?

A

ans

150
Q

What is the mathematical relationship between applied tensile stress and resolved shear stress

A

ans

151
Q

Mathematicial relationship between yield strength and critical resolved shear stress

A

ans

152
Q

How does slip motion occur in polycrystals

A

ans

153
Q

Compare slip vs twinning

A

ans

154
Q

What are 4 methods used to slow dislocation motion?

A

ams

155
Q

How do hard angle grain boundaries prevent dislocation motion?

A

ans

156
Q

What are solid solutions?

A

ans

157
Q

What is precipitation strengthening?

A

ans

158
Q

What is cold working?

A

ans

159
Q

How do calculate cold work percentage?

A

ans

160
Q

How do you calculate dislocation density?

A

ans

161
Q

What happens if you heat a material after cold-working?

A

ans

162
Q

What is the recovery phase?

A

ans

163
Q

What is the recrystallization phase?

A

ans

164
Q

What is called when a material is quenched in order to increase dislocation density?

A

cold working

165
Q
  1. What is a phase diagram?
A

ans

166
Q
  1. What are components?
A

ans

167
Q
  1. What are phases?
A

ans

168
Q
  1. What is the solubility limit?
A

ans

169
Q
  1. How do you determine the solubility limit from a graph?
A

ans

170
Q
  1. What is a binary system?
A

ans

171
Q
  1. What does an isomorphous phase diagram look like?
A

ans

172
Q
  1. How do you find the composition of each phase?
A

ans

173
Q
  1. How do find the wt% of each phase?
A

ans

174
Q
  1. What does Co stand for?
A

ans

175
Q
  1. What is an isotherm?
A

ans

176
Q
  1. How is the lever rule derived?
A

ans

177
Q
  1. How does solid strengthening impact tensile strength and ductility?
A

ans

178
Q
  1. What is a eutectic phase diagram?
A

ans

179
Q
  1. What is the invariant point?
A

ans

180
Q
  1. What is the solidus?
A

ans

181
Q
  1. What is the liquidus?
A

Liquid only component on phase diagram

182
Q
  1. How does the invariant point impact the phases represented in a diagram?
A

ans

183
Q
  1. What is eutectic transition?
A

ans

184
Q
  1. How do you find primary alpha?
A

ans

185
Q
  1. Example question - find compositions of phases in eutectic diagram
A

ans

186
Q
  1. Example questions - find relative amounts within a eutectic diagram
A

ans

187
Q
  1. What is the eutectic microstructure?
A

ans

188
Q
  1. How does cooling rate impact lamellae formation?
A

ans

189
Q
  1. How do you apply the Lever rule to eutectic phase diagram
A

ans

190
Q

Compare terminal solid solutions and intermediate solid solutions

A

ans

191
Q

What are the 3 different types of transformations, and their features?

A

• Simple diffusion-dependent transformations with no change in phase # and composition:
○ solidification of pure metals
○ allotropic transformations
○ recrystallization and grain growth
• Diffusion-dependent transformations with alteration in phase # and compositions – eutectic, eutectoid reactions
Diffusionless transformations – martensitic transformations, not at equilibrium

192
Q

What is nucleation?

A

– nuclei (seeds) act as template to grow crystals
– for nucleus to form rate of addition of atoms to nucleus must be
faster than rate of loss
– once nucleated, grow until reach equilibrium

193
Q

What happens to the parent phase during growth?

A

The parent phase disappears (all or partial)

194
Q

How does delta T impact nucleation rate?

A

Nucleation rate increases as delta T increases

195
Q

Compare the effect of slow supercooling vs rapid supercooling

A

Small supercooling → few nuclei - large crystals Large supercooling → rapid nucleation - many nuclei, small crystals

196
Q

Compare homogenous and heterogenous nucleation

A
  • Homogenous - uniform nucleation, supercooling 80-300C
    Heterogenous - non-uniform, easier, stable nuclei already exist - could be against wall of mould or impurities in the liquid, solidification with only 0.1-10C supercooling
197
Q

What is the Gibbs Free Energy equation?

A

G = H - TS , where H is enthalpy, S is entropy

198
Q

What is surface free energy

A

see picture

199
Q

What is volume (bulk ) free energy

A

ans

200
Q

How do you calculate total free energy change?

A

ans

201
Q

What is the critial radius

A

ans

202
Q

What is activation free energy

A

ans

203
Q

Solidification (need to review notes)

A

ans

204
Q

How is nucleation rate impacted by temperature?

A

ans

205
Q

How do you calculate the no, of atoms in a critical nucleus?

A

ans

206
Q

What is the growth rate (in relation to nucleation)?

A
207
Q

What are the microconstituents you can get in Fe-C alloys?

A

spheroidite, coarse pearlite, bainite, fine pearlite, tempered martensite, martensite

208
Q

Rank Fe-C microconstituents from hardest to softest.

A
209
Q

Describe the features of spheroidite

A

–a grains with spherical Fe3C –diffusion dependent. –heat bainite or pearlite for long times –reduces interfacial area (driving force)

210
Q

What is the crystal structure of martensite?

A

BCT

211
Q

How is martensite formed?

A

Rapid cooling of austenite

212
Q

What contributes to the hardness of martensite?

A

•Interstitial carbon atoms •Less slip system

213
Q

the ratio of the proportional decrease in a lateral measurement to the proportional increase in length in a sample of material that is elastically stretched.

A
  1. What is Poisson’s ratio? What does it determine, what principle is it based on?
214
Q

Which fracture type has no discernible fracture pattern?

A

brittle, hard, fine-grained materials

2021 Sem2 (4 decks)

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