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Topic 4: raw materials to final product - Coggle Diagram
Topic 4: raw materials to final product
4.1 properties of materials
physical properties
weight
gravitational force exerted on a body
to calculate it you need the mass(kg) and gravitational forces(m^2)
measured in newtons(kgm^2)
volume
amount of three dimensional space a body takes up
density
mass per unit volume of a material
important in terms of weight and size
relation to design
pre-packaged food>sold by weight and volume
packing foams/material
mass
amount of matter that a body contains
measured in kg
mass is constant
electrical resistivity
measure of material's ability to conduct or resist electricity.
important when selecting materials as conductors or insulators
relation to design
electrical plugs
thermal conductivity
measures how fast heat is conducted through a slab of material with a given temperature across the slab
important for objects that will be heated or must conduct or be insulated against heat gain or loss
thermal expansion
measure of the degree of increase in dimensions when an object is heated
important when two materials are joined, as they may experience large temperature changes while staying joined
different materials expand at different rates
relation to design
oven doors, glass pot lids with metal rims
hardness
resistance a material offers to penetration or scratching
relation to design
ceramic floor tiles that are extremely hard and resistant to scratching.
mechanical properties
tensile strength
ability of a material to with stand pulling (apart) forces
important when selecting material resistant to stretching
relation to design
ropes(climbing)
cables( in elevators)
fishing lines
compressive strength
ability of a material to with stand 'squashing' forces
relation to design
ceramic floor tiles, concrete and bricks
stiffness
resistance of elastic body to deflection by an applied force
important for maintaining shape
relation to design
aircraft wing, diving boards, bicycle frames
toughness
brittle
breaks into numerous sharp shards (low toughness)
ability of material to resist the propagation of cracks
important where abrasion and cutting may take place
relation to design
automobile bumpers
ductility
ability of material to be drawn or extruded into a wire or other extended shape
important when metals are extruded
relation to design
production of extended extrusions
aesthetic characteristics
aesthetic appeal is when a product is attractive to look at or pleasing to experience, through our senses
taste
sour, sweet, spicy
smell
ability to perceive odours eg sweet, acrid or fragrant
sound
related to pitches
texture
how something feels or looks, can be rough or smooth
appearance
the design of appearance in a product must be aesthetically pleasing to attract a customer
colour
can be warm or cool, can have psychological affects (greens are calming)
shape
geometric or organic
smart materials
materials that react to changes in their environment
designers integrate these materials to the products they design so that the finished product reacts in a pre-determined way to a given stimulus
4.4
4.2
4.2b timber
two main groups of natural wood
soft wood
from evergreen tree (eg pine, cedar and cypress)
hardwood
from a (broad leaved tree (eg oak, elm, maple)
moisture of natural timber
absorbed: contained in cell walls of timber
free: contained in cell cavities + inter cellular spaces
equilibrium moisture content (EMC)> when moisture content of wood is the same as local environment
seasoning
drying of timber that reduces the moisture content of wood
makes it more useable
disadvantage to seasoning
if dried unevenly can cause twisting or bending
characteristics
tensile strength
resistance to damp envorionments
longevity
aesthetic: natural colour range, grain
man made timber
made by mixing wood (chip/particles/dust) with adhesives to create flat sheet materials
form products eg> chipboard, hardboard, fireboard + MDF
plywood> made by lamination(peeling slices of wood off a tree trunk and gluing them together, grain is running 90° to the other)
wood finishes and protection> done to prevent rotting
paint/ varnish/ lacquers so the surface of the wood repels water and chemicals kill the organisms and insects that would damage the wood
wood flooring
softwood> most common, floor boards made from planks (material is cheap and readily available)
4.2c glass
4.2d plastics
4.2e textiles
4.2f composites
4.2a metals & metallic alloys
grain size
metals are crystalline structures compromised of individual grains
reheating solid metal or alloy allows the grains to change their structure
grain size in metals can affect their properties
modifying physical properties
alloying
alloys: mixtures that contain at least one metal
can be a metal and a non metal or two or more metals
increases strength and hardness, allows malleability and ductility compared to pure metals
work hardening
process of toughening the metal through plastic deformation
metal becomes brittle
tempering
heat treatment process
usually carried out after hardening> increases toughness and ductility, decreases hardness and brittleness
super alloys
alloy that has mechanical strength, resistance to thermal creep deformation, good surface stability and resists corrosion
used at high temperatures, close to their melting point
used in aerospace(rockets), aviation(turbines), chemical processing industry
criteria
creep
tendency of metal to slowly deform permanently due to exposure of stress
oxidation resistance
oxidation>interaction between oxygen and different substances (eg when they rust)
ability of material to resist direct and indirect attack of oxygen + degradation
recovery and disposal
metals + metallic alloys are easily recyclable, can be indefinitely recycled
reduces emissions and the affect on the environment
categories of metals
non- ferrous alloys
start to oxidize when exposed to atmosphere
corrosion can be reduced by covering metal with paint or plastic, so that air cannot reach the surface
aluminium, copper, brass, silver, lead
ferrous alloys (containing iron)
start to rust when exposed to atmosphere
mild steel, stainless steel, cast iron
4.6
4.5
4.3