1.1 Materials and Application

Stock Form

the set of standard sizes in which materials are available different stock forms for different types of materials.

mechanical properties

How a material reacts to an external force

physical properties

the make up and structure of the material

compressive strength

mechanical: the ability to withstand being crushed or shortened by pushing forces

tensile strength

mechanical: the ability to resist stretching or pulling forces

Bending strength

mechanical: The ability to resist forces that may bend the material.

shear strength

mechanical: the ability to resist sliding forces on a parallel plane

Torsional strength

mechanical: The ability to withstand twisting forces from applied torque or torsion.

hardness

mechanical: the ability to resist abrasive wear such as scratching

toughness

mechanical: the ability to absorb impact force without fracture

plasticity

mechanical: the ability to be permanently deformed and retain the deformed shape

ductility

mechanical: the ability to be drawn out under tension, reducing the cross sectional area without cracking

malleability

mechanical: the ability to withstand deformation by compression without cracking. increases with a rise in temperature

elasticity

mechanical: the ability to be deformed and then return to the original shape when the force is removed.

electrical conductor

Physical: allows the flow of electrical current through the material. A good conductor gives very little resistance to the flow of charge.

electrical insulator

Physical: does not allow the flow of electricity through the material

thermal conductor

Physical: allows the transfer of heat energy through the material, material with high conductivity allows the transfer of heat to occur quickly

thermal insulator

Physical: prevents the transfer of heat through the material

thermal expansion

Physical: the increase in material volume in response to heat input

opaque

Physical: prevents light travelling through

translucent

Physical: allows light through but diffuses the light so that the objects appear blurred

transparent

Physical: allows light to pass through easily so you can see clearly through the material.

density

Physical: the mass of a material in a standard volume of space

fusibility

Physical: the ability of the material to be fused or converted from a solid to a liquid or molten state, usually by heat. (essential for metals being cast)

magnetism

Physical: the natural force between objects that causes the material to attract iron or steels

corrosion/degradation resistance

Physical: the ability to withstand environmental attack or decay

classification of materials

materials are split into groups depending on their properties and sources.

ferrous metal

contains iron, they are magnetic and will rust

non ferrous metal

does not contain iron, are not magnetic and do not rust

alloy

a metal made from two or more metals - or two or more elements where one is a metal. these can be classified as ferrous and non ferrous alloys

list ferrous metals

low carbon steel, medium carbon steel, cast iron

list non ferrous metals

aluminium, copper, zinc, silver, gold, titanium, tin

list ferrous alloys

stainless steel, die steel (tool steel)

list non ferrous alloys

bronze, brass, duralumin, pewter

hardwood

a wood from broad-leafed (deciduous) trees, slow growing and lose their leaves in autumn

softwood

a wood from coniferous (cone bearing) trees. fast growing and tend to be evergreen

manufactured board

a man-made, wood-based composite material, they are available in much larger sizes than solid wood

list hardwoods

oak, ash, mahogany, teak, birch, beech

list softwoods

pine, spruce, Douglas fir, redwood, cedar, larch

list manufactured boards

plywood, marine plywood, aeroply, flexible plywood, chipboard, MDF

thermoplastic

a material that can be repeatedly reheated and reshaped - long linear molecules held together by van der Walls forces

thermosetting polymer

a material which when heated undergoes a chemical change whereby the molecules form rigid cross-links. Cannot be reheated or reshaped, even at very high temperatures.

elastomer

materials which at room temperature can be deformed under pressure, and then upon release of the pressure will return to their original shape. Weak bonds allow them to be stretched easily

papers and boards

compliant materials, meaning they can be scored, folded and cut with basic tooling to form items such as nets for packaging

composites

a materials made of two or more different materials, resulting in a material with enhanced properties - van be fibre based, particle based and sheet based

smart materials

a material whose physical properties change in response to an input or change in the environment, such as electricity, pressure, temperature or light

modern materials

a material developed through the invention of new or improved processes

material disposal

consideration needed when designing a product since it can influence a consumers choice if a product is recyclable

workshop tests

tests that can easily be carried out in a workshop using basic tools and equipment

tensile testing (workshop)

clamp material samples of same length and thickness and apply weights to the end - can show how much load a material can take

toughness testing (workshop)

material is clamped into a vice then hit with the same force, brittle materials will break while tough materials will absorb the impact

hardness testing (workshop)

abrasive wear - use a file to see which material has the least scratches

resistance to surface indentation - use a dot punch and hammer see which has the least indentation

corrosion testing (workshop)

place materials of same size outside in an area exposed to the weather for a certain length of time, observe changes

malleability and ductility testing (workshop)

secure material in a vice and bend it 90 degrees, outside cracks are lack of ductility, inside are lack of malleability

conductivity testing (workshop)

electrical - multimeter, measures the resistance

thermal - thermometer, place at the end of a material place a bunsen burner under the other end, time how look it takes to heat up

industrial tests

tests carried out in a lab at a materials testing facility with specific machinery, using standardized test pieces of a material

tensile testing (industrial)

standard test piece in tensometer, material is held by two clamps one moves, stretching the material and the distance travelled is plotted

toughness testing (industrial)

Izod impact test, a notched test piece is held vertically in a vice, a pendulum is released from a specific point and strikes the test piece - the energy absorbed is calculated

hardness testing (industrial)

rockwell - preload is applied to the material, which breaks the surface. an additional load is added for a specific length of time, the load is released and the hardness is calculated from the indents.

brinell - hardened steel ball is forced onto the materials surface, the indents diameter is measured smaller = harder

vickers pyramid - very hard materials, diamond square based pyramid indents surface which is measured under a microscope

ductility and malleability testing (industrial)

bend test shows how much cracking a material gets during one continuous bend, test piece is in a bending machine and bent until it either breaks or to a set angle. The material is inspected for cracking

non destructive testing (NDT)

Is carried out on products rather than material samples. The product is not destroyed during testing. NDT is used to find defects in the material that wouldn't be detected otherwise

ultrasonic testing (NDT)

sound waves are reflected of the material and form a display unit that shows if there are any cracks - can be portable and used on all material

X-ray testing (NDT)

X-ray beam passes through the material and displays it to see tiny details

electrical conductivity testing (NDT)

four point probe method determines the conductivity, measurements are taken and ohms law is used to calculate

thermal conductivity testing (NDT)

uses a heat flow meter, measures the heat flow between a piece of material.