1
Q
What are physical properties?
A
- Measurable characteristics
- Examples: Density, melting point, conductivity, coefficient of expansion
Physical properties can be quantified and are essential for material identification and application.
2
Q
Define thermal conductivity.
A
Measure of heat flow through a material
It is quantified as 1 degree per unit of time, per unit of cross-sectioned area, per unit of length.
3
Q
What does corrosion resistance describe?
A
Ability to prevent chemical or electrochemical attack
Corrosion can take forms like pitting, galvanic reaction, and stress corrosion.
4
Q
Density is defined as __________.
A
mass/volume
Density is often expressed in pounds per cubic inch or grams per cubic centimeter.
5
Q
What is the melting point?
A
Temperature at which a substance changes from solid to liquid
It defines the equilibrium condition between solid and liquid phases.
6
Q
Define specific heat capacity.
A
Heat energy required to raise temperature per unit mass
It is an extensive property, proportional to the size of the system.
7
Q
What is hardenability?
A
Ability of steel to transform from austenite to martensite
It describes the depth at which steel can harden under specific cooling conditions.
8
Q
What does weldability refer to?
A
Ability of materials to weld with similar materials
It is also known as joinability.
9
Q
Define permittivity.
A
Ability to store electrical potential energy in an electric field
Measured as the ratio of capacitance with the material as dielectric to that with a vacuum.
10
Q
What is recyclability?
A
Ability of a material to be recycled into similar or other forms
It helps minimize waste, pollution, and resource usage.
11
Q
What does thermal expansion refer to?
A
Fractional change in size due to temperature change
Includes linear, areal, and volumetric expansion.
12
Q
Define permeability in electromagnetism.
A
Measure of magnetisation in response to an applied magnetic field
Measured in Henries per metre (H/m) or newtons per ampere squared (N/A^2).
13
Q
What are mechanical properties?
A
How a material performs under applied forces
Includes strength, ductility, and wear resistance.
14
Q
What is fatigue strength?
A
Maximum stress a material can withstand under repeated stresses
Important for components subjected to repetitive load conditions.
15
Q
Define shear strength.
A
Resistance to sliding forces within a material
Important in applications like bolts and beams.
16
Q
What does tensile strength refer to?
A
Load a material can withstand before breaking
Measured in newtons per square millimetre (MPa) or pounds per square inch.
17
Q
Yield strength describes the point after which a material will no longer return to its __________.
A
original position or shape
This transition is from elastic to plastic deformation.
18
Q
What is toughness?
A
Ability to absorb impact without fracturing
Measured using the Charpy impact test.
19
Q
Define hardness.
A
Ability to resist permanent indentation
Measured by methods like Brinell, Rockwell, and Vickers tests.
20
Q
What is ductility?
A
Ability to deform without fracturing
Often measured as a percentage of elongation before failure.
21
Q
Define malleability.
A
Ability to be formed without breaking
High malleability allows materials to withstand higher pressure.
22
Q
What does elasticity describe?
A
Tendency to return to original size after distortion
Measured by Young’s modulus.
23
Q
Plasticity is the tendency of a material to hold its new shape when subjected to __________.
A
forming forces
Materials transition from elastic to plastic behaviour at the yield point.
24
Q
What is brittleness?
A
Failure without deformation under stress
Common in materials like ceramics and glass.
25
What are **ferrous metals**?
Materials containing iron in their composition
## Footnote
Non-ferrous metals do not contain iron.
26
What is **pig iron**?
Impure product of the blast furnace
## Footnote
Cast into small ingots or pigs.
27
Define **cast iron**.
Selected grades of pig iron re-melted and cast into shapes
## Footnote
Typically using sand moulds.
28
What is **wrought iron**?
Refined iron containing slag
## Footnote
Known for its ductility and toughness.
29
What is the primary component of **steel**?
Iron and carbon
## Footnote
Contains between 1% and 5% carbon.
30
What are common forms of **supply** for metals?
* Square bar
* Round bar
* Sheet steel
* I-beam
* C-beam
## Footnote
Forms depend on the application and use of the material.
31
What is **aluminium** known for?
* Malleable
* Corrosion resistant
* Conductor of heat and electricity
## Footnote
Widely used in aerospace and automotive sectors.
32
What is **copper** commonly used for?
* Household pipes
* Electrical wiring
* Cooking utensils
## Footnote
Malleable and corrosion resistant.
33
What is **zinc** used for?
Protective coating for mild steel components
## Footnote
Known for its ductility and moderate conductivity.
34
Brass is composed of __________.
copper and zinc
## Footnote
It has a higher malleability than zinc or copper.
35
What is **bronze** made of?
Copper and tin
## Footnote
Resists corrosion and metal fatigue better than steel.
36
What is **phosphor bronze**?
8% tin bronze with about 0.3% phosphorus
## Footnote
Known for high tensile strength and corrosion resistance.
37
What are **thermoplastics**?
Resins that become plastic upon heating
## Footnote
They can be reheated and reshaped.
38
What are examples of **thermoplastics**?
* Polyethylene (PE)
* Polycarbonate (PC)
* Polyvinyl chloride (PVC)
## Footnote
They are used in processes like injection-moulding.
39
Define **thermosets**.
Harder and more rigid than thermoplastics
## Footnote
Cannot be softened by reheating.
40
What is a significant aspect of **thermoplastics**?
**Reversibility** – ability to undergo reheating, melt again and change shape
## Footnote
This allows for additional processing of the same material, even after being prepared as a solid.
41
Name some **examples of thermoplastics**.
* Polyethylene (PE)
* Polycarbonate (PC)
* Polyvinyl chloride (PVC)
## Footnote
These materials are known for their ability to be reshaped upon heating.
42
What characterizes **thermosets** compared to thermoplastics?
**Harder and more rigid**; cannot be softened by reheating
## Footnote
A chemical change occurs when heat and pressure are applied, leading to crosslinking of polymers.
43
List some **examples of thermosets**.
* Polyester resin fiberglass systems
* Sheet moulding compounds
* Bulk moulding compounds
* Epoxy resin
## Footnote
Thermosets are used in various applications due to their durability.
44
What are **elastomers**?
**Loosely crosslinked polymers** with characteristics of rubber
## Footnote
They can be stretched easily and return to their original shape when the force is removed.
45
What are **composites** also known as?
**Fibre-reinforced polymers (FRPs)**
## Footnote
Composites combine a polymer matrix with reinforcing materials to enhance strength and stiffness.
46
Define **tensile strength**.
Amount of stress a material can handle before it fails
## Footnote
Measured in megapascals (MPa), varies by material.
47
What does **shear strength** describe?
Material's ability to resist strain when layers shift or slide
## Footnote
Important for understanding how materials behave under stress.
48
What is **compressive strength**?
Performance of a material when compressed or flattened
## Footnote
Composites typically have higher tensile strengths than compressive strengths.
49
Name some **examples of composites**.
* MDF
* Plywood
* Glass reinforced plastic (GRP)
* Carbon fibre reinforced plastic (CRP)
## Footnote
These materials are engineered for specific applications.
50
What are the three categories of **ceramic products**?
* Whiteware
* Refractory
* Engineering products
## Footnote
Each category serves different applications and industries.
51
What are the three categories of **wood**?
* Softwoods
* Hardwoods
* Engineered woods
## Footnote
Each type has distinct characteristics and uses in construction and manufacturing.
52
Define **smart materials**.
**Materials that respond** in a controllable and reversible way to external stimuli
## Footnote
Also known as responsive materials.
53
What is a **shape memory alloy (SMA)**?
An alloy that returns to its original shape when reheated
## Footnote
Composed of metals like copper, zinc, nickel, aluminium, and titanium.
54
What is **covalent bonding**?
Bond formed between non-metallic atoms by sharing electrons
## Footnote
Creates a strong attractive force between the nucleus and outer shell electrons.
55
What is **ionic bonding**?
Bond occurring between metals and non-metals through electron transfer
## Footnote
Results in atoms achieving noble gas configurations.
56
What is **metallic bonding**?
Bond where metal atoms share electrons in their outer shell
## Footnote
Valence electrons are not tightly bound, contributing to metallic properties.
57
What are **Van der Waals forces**?
Short-range forces existing in all materials due to fluctuations in electron clouds
## Footnote
Important in plastics and polymers.
58
What are the two types of **composite reinforcement**?
* Fibre reinforced composites (FRPs)
* Particle reinforced composites (PRCs)
## Footnote
Each type utilizes different mechanisms for enhancing material properties.
59
What is the difference between **crystalline** and **amorphous** solids?
* Crystalline: Ordered alignment, geometric shape
* Amorphous: Random alignment, no defined edges
## Footnote
These structural differences affect material properties.
60
What is **plastic deformation**?
Permanent change in shape of a material when force exceeds yield strength
## Footnote
Common in metal forming processes.
61
What is **bending** in metal forming?
Process using a brake press to shape metal sheets
## Footnote
The die creates a bending force without punching a hole.
62
What is **hot rolling**?
Rolling process above the recrystallisation temperature
## Footnote
Enhances toughness and ductility of steel.
63
What is the purpose of **roll forming**?
Shapes metal as it passes through rollers to achieve desired cross-section
## Footnote
Used for long lengths or large production runs.
64
What is the **roll forming** process used for?
To shape metal as it passes through successive sets of rollers
## Footnote
It is generally used to produce components with long lengths or for large production runs.
65
What is the key difference between **hot working** and **cold working**?
Hot working is performed at temperatures above the recrystallisation temperature; cold working is done below it
## Footnote
Hot working allows for recrystallisation while deforming, whereas cold working strengthens the metal through dislocation movements.
66
What happens during the **hot working** process?
* Internal stresses are not built up
* Cracks and faults can be removed
* Increases ductility of metal
* Reduces yield strength
## Footnote
Hot working is performed above the recrystallisation temperature.
67
Define **cold working**.
Strengthening a metal by plastic deformation at temperatures below the recrystallisation temperature
## Footnote
This process can lead to internal stresses and may propagate cracks.
68
What is **stretching** in metal processing?
A forming process that stretches and bends the workpiece simultaneously over a die
## Footnote
It is used to shape large parts that require sizeable, accurate radius bends.
69
What is **deep drawing**?
A method where a metal sheet is clamped over a cavity-shaped die to form hollow components
## Footnote
The punch pushes down, drawing the sheet into the cavity.
70
What is **sintering**?
The process of forming a solid mass of material through heat and pressure without melting
## Footnote
It involves atoms diffusing across particle boundaries and fusing together.
71
What are the two types of **powder coating**?
* Thermosets
* Thermoplastics
## Footnote
Thermoplastics become liquid when heated, while thermosets form chemical bonds and cannot be recycled.
72
What is **sand casting**?
The most common type of expendable mould casting using permanent patterns
## Footnote
Molten metal is poured into a sand mould cavity where it solidifies.
73
What is **plastic injection moulding**?
The process of melting plastic pellets and injecting them into a mould cavity
## Footnote
This produces the final product as the plastic solidifies.
74
What is **case hardening**?
A method of hardening steel by combining low carbon content metal with higher carbon content metal
## Footnote
It increases product strength and is performed after component formation.
75
What is the purpose of **precipitation hardening**?
To increase yield strength and improve corrosion resistance
## Footnote
It involves solution annealing, quenching, and ageing.
76
What is the first step in **precipitation hardening**?
Solution annealing
## Footnote
It transforms inhomogeneities into homogeneities at high temperatures.
77
What occurs during the **quenching** process?
Rapid cooling of the alloy to prevent discharge of dissolved alloys
## Footnote
This results in a metastable, oversaturated solid solution.
78
What is the purpose of **tempering**?
To develop a combination of hardness, strength, and toughness
## Footnote
It relieves brittleness and stresses induced by quenching.
79
What is the primary purpose of **annealing**?
To alter the metal’s mechanical properties, making it softer and more workable
## Footnote
It reduces the risk of material fracture and excessive wear.
80
What is **galvanising**?
The application of a zinc coating to prevent corrosion
## Footnote
It provides barrier protection and galvanic protection.
81
What is **corrosion**?
The natural conversion of a refined metal to a more stable form, leading to material deterioration
## Footnote
It commonly occurs when metals react with substances like oxygen and water.
82
What is **uniform corrosion**?
The most common form of corrosion that occurs evenly over large areas
## Footnote
It affects the material's surface uniformly.
83
What is **pitting corrosion**?
A localized type of corrosion that creates holes or cavities in the material
## Footnote
It can be hard to predict and detect.
84
What is **crevice corrosion**?
Corrosion that occurs in areas where oxygen is restricted, such as under washers
## Footnote
It results from differences in ion concentration.
85
What is **galvanic corrosion**?
Corrosion that occurs when two different metals are in contact in a common electrolyte
## Footnote
The more active metal corrodes faster than the more noble metal.
86
What is **stress corrosion cracking (SCC)**?
Crack growth due to a corrosive environment under tensile stress
## Footnote
It can lead to failure of ductile metals, especially at high temperatures.
87
What does **corrosion prevention** involve?
Measures taken to protect materials from deterioration due to chemical or electrochemical interactions
## Footnote
It begins with analyzing the galvanic effect and surrounding environmental conditions.
88
What is **corrosion prevention**?
Measures taken to prevent corrosion
## Footnote
Designed to protect materials from deterioration due to chemical or electrochemical interactions.
89
Name the **methods of corrosion prevention**.
* Protective coating
* Metal alloy
* Corrosion inhibitors
* Electrochemical control measures
## Footnote
Techniques used to treat materials to prevent corrosion.
90
What causes **deformation** in materials engineering?
Applied forces or change in temperature
## Footnote
Deformation can lead to material failure.
91
What are the **types of deformation**?
* Elastic deformation
* Plastic deformation
* Metal fatigue
* Compressive failure
## Footnote
Different types may result from variations in material, size, and force applied.
92
True or false: **Elastic deformation** is reversible.
TRUE
## Footnote
Materials like elastomers and memory metals exhibit elastic deformation.
93
What is **ductile fracture** characterized by?
Plastic deformation before fracture
## Footnote
Ductile materials stretch before breaking.
94
What is the difference between **ductile fracture** and **brittle fracture**?
* Ductile fracture: plastic deformation occurs
* Brittle fracture: negligible plastic deformation
## Footnote
Ductile fractures provide warning before failure, while brittle fractures do not.
95
What is **necking** in materials?
Localized reduction in cross-sectional area
## Footnote
Observed in ductile materials under tensile stress.
96
What is the **cup-and-cone formation**?
A characteristic of ductile fracture
## Footnote
Involves necking, micro-void formation, and crack propagation.
97
Define **fatigue** in engineering material science.
Weakening of a material due to repeated stress
## Footnote
Fatigue can cause failure below the material's ultimate tensile strength.
98
What are the **stages of fatigue failure**?
* Crack initiation
* Slow, stable crack growth
* Rapid fracture
## Footnote
Fatigue occurs after repeated loading and unloading.
99
What is **creep**?
Time-dependent and permanent deformation under constant load
## Footnote
Typically occurs at elevated temperatures.
100
What are the **three periods** of the creep curve?
* Primary creep
* Secondary creep
* Tertiary creep
## Footnote
Each period has distinct characteristics regarding material deformation.
101
What is the purpose of **destructive testing**?
To determine specific properties of materials
## Footnote
Involves damaging or destroying the test piece.
102
What is the **Brinell test** used for?
To measure hardness of materials
## Footnote
Involves forcing a hardened steel ball into the material's surface.
103
What does the **Charpy impact test** measure?
Amount of energy absorbed during fracture
## Footnote
Involves striking a notched specimen with a pendulum.
104
What is **Young's modulus**?
A measure of a material's ability to withstand changes in length
## Footnote
Describes elastic properties under tension or compression.
105
What is **Hooke's law**?
Displacement is directly proportional to the deforming force
## Footnote
Applies to relatively small deformations.
106
What is the formula for **electrical conductivity**?
s = I / (A * R)
## Footnote
Conductivity is measured in ohm^-1 meters^-1 (siemens).
107
What are the **five forms of loading**?
* Compression
* Tension
* Shear
* Torsion
* Bending
## Footnote
Different forces can change the shape of materials.
108
What is **Young's modulus**?
A numerical constant describing the elastic properties of a solid undergoing tension or compression in one direction
## Footnote
Named after Thomas Young, it measures a material's ability to withstand changes in length under tension or compression.
109
Young's modulus is equal to the **longitudinal stress** divided by the _______.
strain
## Footnote
Stress is defined as the tensile force divided by the cross-sectional area.
110
What is the formula for calculating **stress**?
σ = F/A
## Footnote
Where F is the force applied and A is the cross-sectional area.
111
What does **strain** measure?
The ratio of the change in dimension to the initial dimension
## Footnote
It does not have a unit and can be normal, volumetric, or shear.
112
What are the **three stages** shown in the stress-strain curve for ductile materials?
* Linear elastic region
* Strain hardening region
* Necking region
## Footnote
These stages represent different responses of the material under applied load.
113
What is the **ultimate tensile strength (UTS)**?
The maximum stress a material can sustain before failure
## Footnote
It is observed in the strain hardening region of the stress-strain curve.
114
In a stress-strain curve, the area under the curve from the origin to the proportional limit falls under the **________** range.
elastic
## Footnote
Beyond the proportional limit, the material exhibits plastic behavior.
115
What color represents a **brittle material** in stress-strain curve interpretations?
Green
## Footnote
Brittle materials show little strain for high stress and fracture suddenly.
116
What does a **black** color indicate in stress-strain curve interpretations?
A strong material which is not ductile
## Footnote
Example: steel wires stretch very little and break suddenly.
117
What does an **orange** color indicate in stress-strain curve interpretations?
A ductile material
## Footnote
It shows necking and permanent deformation in the plastic region.
118
What does a **purple** color indicate in stress-strain curve interpretations?
A plastic material
## Footnote
It has a very small elastic region.
119
What is the formula for calculating **strain**?
ε = (l - lo) / lo
## Footnote
Where Io is the initial length and l is the stretched length.
120
The units of **Young’s modulus** in the metric system are _______.
newtons per square metre (N/m^2)
## Footnote
In the English system, the units are pounds per square inch (psi).
121
The value of Young’s modulus for **aluminium** is approximately _______.
1.0 X 10^7 psi
## Footnote
The value for steel is about three times greater.
T-level Mechanical Engineering
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