Core 4 (Revised by spec) Flashcards
4.1
4.1
What are the physical properties of materials?
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Properties that can be determined without damage or destruction of the material.
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mass, weight, volume,
density, electrical resistivity, thermal
conductivity, thermal expansion and hardness
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Electrical resistivity (σ) - This refers to the ease with which electrons move through a material.
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Thermal conductivity (W.m^-1.K^-1) - A measure of the efficiency with which thermal energy will travel through a material.
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Thermal expansion (m.m^-1.K^-1) - describes how the size of an object changes with a change in temperature.
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Hardness - The resistance of a material to scratching or abrasion. A composite of:
- Yield Strength
Stress where material deforms permanently, beginning plastic deformation.
- Work Hardening
Material strengthening through plastic deformation, increasing resistance to further deformation.
- True Tensile Strength
Maximum stress material withstands considering actual area reduction during tension.
- Modulus of Elasticity
Measures material’s stiffness, ratio of stress to strain in elasticity.
What are the mechanical properties of materials?
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Properties that relate to the way in which the material responds to the application of a force.
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tensile and compressive
strength, stiffness, toughness, ductility, elasticity,
plasticity, Young’s modulus, stress and strain
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Tensile and compressive strength measure resistance to plastic deformation under stretching or compressive loads. Ultimate tensile stress is the material’s maximum tensile strength measured during testing.
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Stiffness is the resistance of an elastic body to deflection by an applied force.
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Toughness is the ability of a material to resist the propagation of cracks.
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Ductility is a material’s ability to undergo significant plastic deformation before fracture, typically measured by elongation or reduction in area.
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Elasticity - A measure of a material’s ability to stretch under load and then return to its original dimensions after removal of that load.
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Plasticity - Elasticity of a material is associated with elongation behaviour that exceeds the elastic region.
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Young’s modulus is a measure of stiffness or rigidity of a material. Describes how much a material will stretch or compress with force.
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Stress - A measure of the force being applied per unit area. (Stress = force / area)
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Strain - A measure of change in length occurring when under stress, divided by the unit length.
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*Stress and strain have true values which involve the instantaneous csa or length but more difficult to measure.
What are the aesthetic characteristics of materials?
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Personal Taste
Individual preferences influencing material selection, based on style, color, or feel, often subjective and culturally influenced.
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Smell
Materials may have distinct odours that evoke emotions or associations, impacting perception and appeal, especially in interiors.
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Appearance
Visual qualities such as color, shine, transparency, or pattern; crucial in selecting materials for design and visual harmony.
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Texture
The tactile feel of a material’s surface, influencing comfort, grip, and overall sensory experience, crucial in product design.
What are the smart materials? Their properties? and the 5 smart materials learnt?
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Respond to external stimuli or and exhibit specific, reversible changes in their properties.
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They must have: responsiveness, reversibility, adaptability
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Piezoelectricity
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Material that responds to an application of an applied stress by producing a small electrical discharge and vice versa.
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Shape memory alloys
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Capable of changing shape and size in a predetermined manner by undergoing a solid-state phase change.
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Photochromic
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Undergo a reversible photochemical reaction that results in darkening proportional to the level of exposure to UV light.
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Magnet/Electro-rheostatic
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Fluids that can undergo changes in their viscosity, becoming semi-solid when exposed to an electric or magnetic field
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Low toxicity
Non-abrasive
Non-corrosive
Long storage life
Long working life
High boiling point
Low freezing point
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Thermoelectricity
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Exhibit the feature that when exposed to temperature differential, an electric potential is created and vice versa.
Design contexts where physical properties, mechanical properties and/or aesthetic characteristics are important.
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Physical Properties
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Insulation Materials
Physical properties like thermal conductivity are crucial in designing buildings or clothing for energy efficiency and comfort, ensuring proper temperature regulation.
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Optical Lenses
The refractive index and transparency of materials are important in designing corrective eyewear or camera lenses for clarity and focus.
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Packaging Design
Physical properties like weight, density, and moisture resistance are key to packaging materials, ensuring product protection and longevity.
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Mechanical Properties
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Automobile Frames
Mechanical properties like tensile strength and impact resistance are essential for car frames to ensure safety, durability, and performance in crash tests.
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Bridge Construction
Compressive strength, elasticity, and fatigue resistance are critical for designing bridges to support heavy loads and withstand environmental stresses over time.
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Sports Equipment
Materials for sports gear, like tennis rackets or football helmets, require high tensile strength and impact resistance to ensure safety and performance.
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Aesthetic Characteristics
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Furniture Design
Appearance, texture, and personal taste influence furniture choices, impacting comfort, visual appeal, and user satisfaction in home or office environments.
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Interior Design
Materials with appealing aesthetics, like color, texture, and smell, contribute to creating harmonious, inviting, and comfortable living or working spaces.
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Fashion Design
Aesthetic qualities such as color, texture, and the feel of fabrics are essential in creating visually attractive and comfortable clothing items.
Design contexts where properties of smart materials are used.
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Piezoelectricity
Medical Sensors
Piezoelectric materials are used in medical sensors, converting mechanical stress from body movement into electrical signals for diagnostic purposes, such as in ultrasound devices or pressure sensors.
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Shape Memory
Aerospace Components
Shape memory alloys are used in aerospace for actuators that return to a pre-determined shape when heated, helping deploy wing flaps or antennas automatically in flight.
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Photochromicity
Eyewear
Photochromic lenses in eyeglasses automatically adjust to light intensity, darkening in bright sunlight and clearing indoors, offering convenience and eye protection.
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Magneto-rheostatic
Automotive Suspension Systems
Magneto-rheological fluids are used in automotive suspension systems, adjusting stiffness in real-time by applying a magnetic field, improving ride comfort and handling.
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Electro-rheostatic
Clothing
Electro-rheological materials are utilized in adaptive clothing, changing stiffness in response to an electric field, offering dynamic support or flexibility in sportswear or medical garments.
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Thermoelectricity
Wearable Cooling/Heating Devices
Thermoelectric materials are used in wearable devices, converting temperature differences into electrical power to provide cooling or heating, enhancing comfort for users in varying environments.
Using stress/strain graphs and material selection
charts to identify appropriate materials
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Stress/Strain Graphs
Stress/strain graphs reveal how a material deforms under load. By analyzing yield strength, tensile strength, and ductility, you can select materials based on performance criteria like strength, flexibility, or resilience for specific applications, ensuring reliability and safety under expected stress conditions.
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Material Selection Charts
Material selection charts compare properties like strength, cost, density, and thermal conductivity across materials. By plotting required specifications against available materials, you can quickly identify the most suitable option based on mechanical, thermal, and economic factors, optimizing material performance and efficiency for your design needs.
4.2a
4.2a
What is an ore? What are the processes surrounding them?
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Most metals are naturally found as ores, which means they contain impurities of other elements such as oxide, carbonate, or sulphide.
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Ores can be smelted over intense heat to separate them into the impurities that make them up thanks to unique melting points.
Explain grain and grain size in metals.
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When most solids form, they generally do so by arranging themselves in a regular pattern of atoms, a regular 3D arrangement known as collections of crystal structures. All metals solidify as collections of crystals (aka grains).
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The crystal structure of a metal reflects its properties.
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As a metal solidifies, these crystals form and grow. Eventually, different crystals will collide and intersect at different angles/patterns.
This region of mismatch is known as the crystal or grain boundary.
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Hence, grain size refers to the average size of the individual grains that make up the microstructure.
What are the 3 ways of modifying the mechanical properties of metals you need to know?
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Alloying
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elements other than those of the base metal are intentionally incorporated into the crystal lattice of the base metal. This results in the presence of more than one crystal structure.
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Used to to gain more desirable characteristics in a metal such as improved strength, corrosion resistance, hardness, or other properties.
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Work hardening (cold working)
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strengthens a metal by deforming it through processes such as rolling, hammering, or bending, typically at room temperature.
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introduces dislocations in the metal’s crystal structure, which makes further deformation more difficult, thereby increasing the metal’s strength and hardness.
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Tempering
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ferrous alloys such as stainless steel undergo a hardening heat treatment, in which an item is raised to an elevated temperature and cooled rapidly by plunging it into a suitable quenching medium.
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Hardness and strength are significantly increased, however, there is an accompanying decrease in ductility and impact toughness.
What are superalloys? What criteria must they meet?
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Feature excellent high-temperature creep resistance, resistance to thermal shock and high-temperature oxidation resistance.
These alloys are well known for their ability to operate at high temperatures while maintaining strength.
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Creep resistance: creep is the tendency of a solid material to undergo slow deformation while subject to persistent mechanical stresses.
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Thermal shock resistance: ability to withstand sudden and extreme changes in temperature without cracking or failing.
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High-temperature oxidation resistance: ability to resist oxidation at elevated temperatures when exposed to oxygen.
What are the applications of superalloys?
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Iron-nickel based superalloys
- Cryogenics
- Jet engine components
- Petrochemical processing
machinery
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Cobalt-based superalloys
- Turbine blades
- Orthodontic wires
- Biomedical implants
- Food processing equipment
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Nickel-based superalloys
- Air scrubbers
- Marine applications
- Gas turbine components
Discuss the recovery and disposal of metals and metallic alloys.
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The recovery and disposal of metals and metallic alloys are critical for sustainability.
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Recovery involves the reuse of scrap metals, often through recycling processes like melting and refining, which helps conserve raw materials and reduces energy consumption.
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Metals like aluminium, steel, and copper are commonly recycled, with aluminium recycling saving up to 95% of energy compared to producing new metal.
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Disposal of metals must be handled carefully due to their environmental impact.
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Metals are durable but can be harmful if improperly discarded. For example, electronic waste (e-waste) contains hazardous metals like lead or mercury, which must be processed to avoid contamination.
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Proper recycling programs, safe disposal methods, and advancements in recovery technologies are essential to minimizing environmental harm and maximizing resource efficiency.
