Engineering Unit 1

strength

the ability of a material to withstand a force that is applied to it

tensile strength

the ability to resist a pulling force

compressive strength

the ability to resist a squeezing force eg. ceramics

torsional strength

the ability to resist a twisting force

yield strength

the amount of stress needed to start permanently deforming a material

ultimate tensile strength

the amount of stress at which the material fails

stress =

force/cross-sectional area

ductility

the amount that a material can be deformed eg. nylon

strain =

change in length/original length

malleability

the ability of a material to be deformed without rupturing eg. modelling clay

hardness

the ability of a material to resist wear and abrasion eg. stainless steel

toughness

the ability of a material to withstand an impact without breaking

brittleness

the inability of a material to withstand an impact without breaking

stiffness

the ability of a material to resist bending

the stronger the material and the more it resists deforming, the stiffer it is

young’’s modulus

the ratio of stress to strain of a material, showing how stiff it is

young’s modulus =

stress/strain

ore

rocks or minerals dug from quarries or mines then refined and processed to turn the metal into a usable form

alloy

a mixture of two or more metals

what is the main alloying element of ferrous metals

iron

what type of metal does not contain iron?

non-ferrous

what non-metal makes up a small part of ferrous metals and what is the name of this alloy?

carbon

carbon steel

why isn’t pure iron used in engineering?

it is too soft

increasing the amount of carbon in a ferrous alloy…

increases the hardness and strength of the material

2 pros and 2 cons of cast iron:

pro: good compressive strength, low cost

con: relatively brittle, poor corrosion resistance

2 pros and 2 cons of low- carbon steel:

pro: relatively low cost, tough

con: cannot be hardened, lower strength than other steels

2 pros and 2 cons of high-carbon steel:

pro: strong and hard, can be hardened

con: difficult to form, not as tough as low-carbon steel

2 pros and 2 cons of stainless steel:

pro: good corrosion resistance, strong and hard

con: difficult to machine, relatively expensive

3 examples for non-ferrous alloys:

aluminium, copper, brass

properties of aluminium alloys:

corrosion resistant, lower density, relatively expensive

properties of copper alloys:

good electrical conductor, ductile, good corrosion resistant,

properties of lead alloys:

soft, malleable, ductile, corrosion resistant, high density

properties of zinc alloys:

low melting point

cold working

repeatedly bending or hammering a metal

work hardening

an increase in the strength and hardness of a metal due to cold working

annealing

a heat treatment that makes a metal softer and easier to work

hardening

a heat treatment that increases the hardness and strength of a metal due to a change in the arrangement of the atoms in it

quenching

the rapid cooling of a hot metal by immersing it in a liquid, often oil or brine

tempering

a heat treatment to remove some of the brittleness in a hardened steel, at the cost of some hardness

normalising

a heat treatment that results in metal that is tough with some ductility

corrosion

a reaction between the surface of a material and its environment that consumes some of the material

how would you stop the surface of steel coming into contact with water?

painting, applying a plastic coat, applying a layer of another metal that doesnt react with water, using a sacrificial metal

carburising

the addition of carbon to the surface of a low-carbon steel to improve hardness and strength

polymer

a type of material made from a large number of similar, smaller chemical units that are bonded together

thermoplastic

a type of polymer that can be reshaped when heated

thermosetting polymer

a rype of polymer with cross-links between the polymer chains, cannot be reshaped when heated

what non renewable material are synthetic polymers typically made from?

crude oil

TRUE OR FALSE: Thermoplastics can be recycled

TRUE

which thermoplastic is used to make drink bottles?

polyethylene terephthalate

what thermoplastic is most commonly used to make plumbing pipes?

polyvinyl chloride

what thermoplastic is used to make carrier bags?

low density polythene

what thermoplastic is used to make medical equipment

polypropylene

TRUE OR FALSE: Acrylic is a thermosetting polymer

FALSE

what are some common uses of epoxy?

printed circuit boards, cast electrical insulators

which thermosetting polymer is used to make foam insulation panels and hoses?

polyurethane

what type of polymer are tyres made from

thermosetting vulcanised rubber

composite

a type of material made by combining two or more different types of material, remaining physically distinct

reinforcement

the particles or fibre within a composite matrix that serve to increase its strength

what is the difference between a polymer and a composite?

polymers are chemically bonded whereas composites are simply mixtures

give 2 examples of composite materials

medium density fibreboard (MDF) and plywood

can composites usually be recycled?

no

timber

wood, a type of material obtained from trees

ceramic

a type of material that is typically an oxide, nitride or carbide of a metal

give 2 examples of structural timber

cedar, spruce

what is softwood

wood produced from coniferous trees

what are ceramics used for

building materials such as concrete, lenses, tools for cutting and grinding

can ceramics be recycled?

not usually however glass is an exception

form (of a material)

the shape and dimensions the material can be purchased in

advantages of selecting the right form

minimises the manufacturing needed thus reducing the cost of production