AS - materials and components Flashcards
Ductility means
The ability to be drawn into wires
Plasticity means
The ability to return shapes to their original shape
Hardness means
The ability to withstand scratching
Brittleness means
The tendency to fracture under stress
Malleability means
The ability of a metal to be deformed by compression without being torn or cracked
Ferrous is when
A metal contains iron
Mild steel properties include
Ductile, tough, malleable, high tensile strength, easily worked, rusts
Rust is
Oxidation
More carbon added to steel makes it
Harder
Ferrous metals include
Cast iron/steel (mild+Carbon)
Aluminium a properties include
Lightweight, corrosion resistant, good conductor, malleable, has an oxide layer
What ore is aluminium obtained from
Bauxite ore
What are some uses of aluminium
Drinks cans, aeroplanes
Properties of copper include
Ductility, malleable, great conductor, corrosion resistant
Uses of copper include
Wiring and circuitry
What happens when you work copper? How can you reduce this effect?
It hardens, soften it by annealing
Properties of zinc include
Easily worked, corrosion resistant
What happens when zinc is worked? And what is zinc used for?
It becomes increasingly brittle, it’s used for galvanising
Examples of non-ferrous metals are
Aluminium, copper, zinc
Examples of alloys are
Stainless steel, duralumin, brass
What is stainless steel composed of
Chromium, nickel, steel
What is duralumin composed of
Aluminium copper manganese
Brass is composed of
Copper and zinc
Properties of stainless steel include
Corrosion resistant, hard, aesthetically pleasing
Examples of stainless steel are
Cutlery/kitchen utensils
Properties of duralumin include
Lightweight, strong, ductile, malleable, excellent to work with
Examples of duralumin include
Aircraft industry
What happens to duralumin over time
It hardens
Properties of brass include
Corrosion resistant, works very well, good thermal+electrical conductivity
Examples of brass in use include
Plug sockets, central heating
Examples of thermoplastic polymers include
Acrylic, PET, H/LDPE,PVC,PP,ABS, PS
Positives of acrylic are
Comes in colours Stiff Hard Durable Good insulator
Negatives of acrylic
Brittle
Scratches easily
Splinters easily
Examples of acrylic
Lighting
Cd cases
Car lights
PET positives are
Chemical resistant
High impact resistance
Tensile strength
PET negatives are
Can discolour
If used for food packaging the food has to be treated to prevent problems in taste
Example of PET in use
Fizzy drinks bottles
Positives of HDPE
Good electrical insulator
Chemical+impact resistance
Flexible
Negatives of HDPE
Colour fades
Breaks under stress
Positives of LDPE
Good electrical insulator
Chemical resistant
Flexible
What is the difference between LDPE and HDPE
LDPE is not impact resistant where as HDPE is impact resistant
Positives of PVC
Good chemical resistance Weather resistant Stiff Tough Hard Lightweight
Negatives of PVC
Brittles over time caused by UV rays from the sun
Positives of PP
Light
Hard
Impact resistant
Chemical resistant
Uses of PVC
Wiring insulation, pipes, flooring
Pp is used for
Syringes and carpets
Negatives of PP
UV rays from the sun cause degradation
Oxidation in manufacture
What are the two types of polystyrene
Compressed and expanded
Positives of compressed polystyrene
Good chemical resistance Weather resistant Light Hard Stiff Brittle Low impact strength
Uses of compressed PS
Cd cases
Water containers
Fridge linings
Positives/negatives of expanded PS
+buoyant lightweight good insulator
-easily ignites
Breaks easily (crumbles)
Uses of PS
Packaging
Insulation
Displays
ABS +/-
+chemical resistant hard tough
-degraded by uv light
Uses of abs
Mobile phones
Safety helmets
Difference between thermosetting plastics and thermoplastics is
Thermosetting plastics can only be melted and shaped once however thermoplastics can repeatedly be melted down and reshaped/reformed
Examples of thermosetting plastics include
Epoxy resins
Polyester resins
Urea formaldehyde
Epoxy resins +/-
+Corrosion resistant
Electrical resistant
Good bonding qualities
- can cause allergic reactions
Uses of epoxy resins
Adhesives
Paints
Electronics
Uses of urea formaldehyde
Electrical fittings
Domestic appliance components
Uses of polyester resins
Glass reinforced boats/cars
Garden furniture
Polyester resins +-
+good electrical insulator
Heat resistant
-brittle so cracks easily
Urea formaldehyde +-
\+strong Hard Brittle Heat resistant -can emit toxic vapours during manufacture
Types of softwoods include
Pine
Pine +-
+straight/attractive grain
Easily worked
-knots can be seen as unattractive and they’re hard to work
Uses of pine
Construction
Floorboards
Furniture
What defines a softwood
Fast growing Cheap Easy to walk Conifer trees Not necessarily soft Needles leaves
Examples of hardwoods
Oak
Mahogany
Beech
Features of hardwoods
Broad leaved
Deciduous trees
Slowly grow
More expensive
Uses of oak
Construction
Garden furniture
High quality furniture
Uses of mahogany
Furniture
Veneers
Floorboards
Uses if beech
School desks
Furniture
Examples of man made boards
Mdf
Blackboard
Chipboard
Plywood
+- of oak
\+strong Hard Tough Aesthetically pleasing Durable Works well - expensive Heavy Prone to splitting Physically hard
+/- of mahogany
\+easy to work Durable Finishes well -grain can be variable Prone to warping Physical hardness varies Out of style
+- of beech
\+physically hard Tough Polishes well - prone to warping Not suitable for outdoor applications Hard to work
Mdf is glued …
Sawdust
Chipboard is glued…
Wood chips
Blackboard is glued…
Softwood strips
Plywood is glued…
Sheets of veneer
What are the three types of cams
Eccentric
Pear
Snail
What’re the three types of follower
Flat
Knife
Roller
What is a flat follower like
Most friction
Cannot follow hollow contours
What is a roller follower like
Least friction
Cannot be used to follow hollow contours
Most expensive
What is a knife follower like
Most accurate conversion of movement
Can be used to follow hollow contours
Draw all the types of cams
Off centred up and down simple motion for eccentric
Central but dwell period for pear
Used for one direction of motion e.g. Sewing machine for snail
Describe a rivet
Permanent joint in metal
What do bearings do
Reduce friction and allow shafts to spin more efficiently
Define pitch
Distance travelled for one full revolution
Name four smart materials
Shape memory alloys Smart paint Reactive glass Photochromic paint Quantum tunnelling composites
Describe a rack and pinion gear
Changes rotary motion to linear motion
Describe a worm and wheel gear
Transmit force and motion through 90degrees
Describe a bevel and mitre gear
Can have shafts at 90degrees where different sized gears can change speed
Describe a spur gear
Speeds can be increased or decreased as well as the rotation direction being changed
What is the key feature of a countersunk screw
It allows a flush finish as it has a flat top
What are locked nuts used for
Situations where vibrations are expected
How does photochromic paint work
Contains pigments that change colour according to light conditions
How do quantum tunnelling composites work
In a relaxed state QTCs are perfect electrical insulators but when stretched/twisted/compressed it becomes an excellent conductor
If there is a greater stress on a QTC what is improved
Conductivity
Describe and say How does a shape memory alloy work
It is a material that can be deformed by an outside stimulus then, when this stimulus is removed, it’ll return to it’s original state this stimulus is typically ELECTRICITY
What other stimuli apart from electricity can stimulate shape memory alloys
Light
Pressure
Name the 5 modern materials/products
Thermo-ceramics Tinted/photochromic glass Liquid crystal displays (LCDs) Solar panels Electroluminescent lighting
Describe thermo-ceramics
Advanced ceramic materials that’re extremely hard and stable at high temperatures but are brittle and very expensive
How are ceramics and metallic powders produced
Sintering
What is the sintering process
Powdered metals are heated then placed in a die, subjected to high pressure until the particles bond together
What’re thermo ceramics used for
Jet engines and turbines
What does photochromic glass do and what makes it react as it does?
It darkens when exposed to UV light then turns back to clear glass if reduced or removed
Silver halide particles in the glass are impregnated in the glass
What are uses of photochromic glass
Glasses
Polaroid pictures
What is the key downside of photochromic glass
It’s irreversible
What’re LCDs
Organic, carbon based compounds that can exhibit both liquid and solid crystal capabilities
What is the key benefit of LCDs
They do not require much energy to power
How do solar panels work
They use photovoltaic cells to harness light and convert it to electricity
What does the silicon layer in solar panels do to make the light convert to electricity
When sun hits the silicon it becomes electron rich whilst the other side becomes electron deficient causing a voltage to flow which is then harnessed and used as electricity
What’re are the important benefits and disadvantages to using solar power
Abundantly available and renewable
Expensive to set up
Don’t produce much energy
Reliant on the sunlight
What does electroluminescent lighting do and how
Converts electrical energy to light by applying a voltage across electrodes
An organic phosphor is between two conductors and they’re rapidly charged then emit light
What’re the +/- of electroluminescent lighting
Extremely low power consumption
The organic phosphor materials used have a limited lifespan
What’re 4 types of composites
Man made boards
Glass reinforced plastic
Carbon fibre
Laminates
How are GRPs made
Thermosetting plastic resin reinforced using very fine glass
What does adding glass to resin in a GRP do to it and why should we do this
The glass improves the tensile strength massively of the resin which has an already strong compressive strength but weak tensile without the glass
What’re the +/- of GRPs
Good strength:weight ratio and very corrosion resistant
Brittle and can shatter easily
When used in boats it can be prone to osmosis
What is carbon fibre ideally used for?
High performance structural applications
Sports equipment
Racing cars
What is the manufacturing process of carbon fibre/GRPs
1) an expensive, high quality mould is prepared
2) a release agent is sprayed onto the mould otherwise the final product will not be able to be removed from the mould
3) a gel coat is applied to the mould; this is a thin layer of resin that will form the outer skin of the final product
4) layers of resin, catalyst and glass matting are placed into the mould
5) once the layering is complete the work is left to CURE over night then it can be eased out of the mould
How are laminates produced
By binding together two or more layers of material
What’re the key features of laminates
Very stable, don’t warp, easy to work, comes in any size, cheap
Worse aesthetics then wood, not good surface finish and thin so can’t be jointed like wood (can look cheap)
