1.1 - Materials And Their Applications Flashcards
Stock form def
+ what Allows for
The set of standard sizes in which materials are available
Allows for standardisation if designers are designing products to be manufactured in another part of the world
What are the advantages of stock forms?
- Uniformity of material sizes across countries
- The material can be transported more easily (e.g., whole tree trunk)
- Standard stock sizes are less expensive than specialist sizes (processed in large quantities)
- Less waiting time than for a specialist size (material will be repeatedly manufactured in the same sizes).
What are the 2 principal categories of material properties?
(Names)
Mechanical & Physical
What is the definition of a mechanical property?
Mechanical:
M properties are associated with how a material reacts to an external force.
What is the definition of a physical property?
Physical:
P properties are associated with the actual make-up or structure of the material.
Mechanical properties of materials
Names + definitions
(for separate flashcards go to deck called 1.1 definitions).
- Compressive strength:
The ability to withstand being crushed or shortened by pushing forces. - Tensile strength:
The ability to resist stretching or pulling forces. - Bending strength:
The ability to resist forces that may bend the material. - Shear strength:
The ability to resist sliding forces on a parallel plane. - Torsional strength:
The ability to withstand twisting forces from applied torque or torsion. - Hardness:
The ability to resist abrasive wear such as scratching, surface indentation or cutting. - Toughness:
The ability to absorb impact force without fracture. - Plasticity:
The ability to be permanently deformed (shaped) and retain the deformed shape. - Ductility:
The ability to be drawn out under tension, reducing the cross-sectional area without cracking, for example stretching a material into a wire. - Malleability:
The ability to withstand deformation by compression without cracking. Malleability increases with a rise in temperature. - Elasticity:
The ability to be deformed and then return to the original shape when the force is removed.
Physical properties of materials
Name + definition
(for separate flashcards go to deck called 1.1 definitions).
Electrical properties:
* Electrical conductor:
Allows the flow of electrical current through the material. A good conductor gives very little resistance to the flow of charge.
- Electrical insulator:
Does not allow the flow of electricity through the material.
Thermal properties:
* Thermal conductor: Allows the transfer of heat energy through the material. A material with high thermal conductivity allows the transfer of heat to occur quickly across the material.
- Thermal insulator:
Prevents the transfer of heat through the material. - Thermal expansion:
The increase in material volume in response to a heat input.
Optical properties:
* Opaque: Prevents light from travelling through
- Translucent:
Allows light through but diffuses the light so that objects appear blurred. - Transparent: Allows light to pass through easily which means you can see clearly through the material.
Others:
* Density:
The mass of the material in a standard volume of space.
*Fusibility:
The ability of the material to be fused or converted from a solid to a liquid or molten state, usually by heat. Good fusibility is an essential property for a metal being cast.
*Magnetism:
The natural force between objects that causes the material to attract iron or steels.
*Corrosion / degradation resistance:
The ability of the material to withstand environmental attack and decay.
Classifications of materials
(Name them)
(7)
Metals
Woods
Polymers
Papers and boards
Composites
Smart materials
Modern materials
What can metals be classified as?
(Names & definitions)
Ferrous:
A metal containing mostly iron and carbon. Magnetic and will rust,
Non- ferrous:
A metal that does not contain iron. Non-ferrous metals are not magnetic and do not rust.
Alloy:
A metal made of two or more metals, or combining two or more elements, one of which must be a metal.
Alloys can also be sub classified as ferrous alloys or non- ferrous alloys.
Give examples of the following metals:
- Ferrous
- Non-ferrous
- Alloy
Ferrous:
Low carbon steel, medium carbon steel, cast iron.
Non- ferrous:
Aluminium, copper, zinc, silver, gold, titanium, tin.
Alloy:
Ferrous:
Stainless steel, die steel (tool steel).
Non-Ferrous:
Bronze, brass, duralumin, pewter.
Woods
Names & definitions
Hardwood:
A wood from broad-leafed (deciduous trees).
These trees are generally slow growing and lose their leaves in the autumn.
Softwood:
A wood from a coniferous (cone bearing) tree.
These trees are generally fast growing and tend to be evergreen.
Manufactured board:
A man-made wood-based composite material.
Available in much larger sizes than solid wood.
Give examples of the following woods:
- Hardwood
- Softwood
- Manufactured board
Hardwood:
Oak, ash, mahogany, teak, birch, beech.
Softwood:
Pine, spruce, Douglas fir, redwood, cedar, larch.
Manufactured board:
Plywood, marine plywood, aeroply, flexible plywood, chipboard, MDF.
Polymers
Names and definitions
Thermoplastic:
A material which can be repeatedly reheated and reshaped, allowing it to be recycled after its initial use.
They have long linear chain molecules held by van der Walls forces.
Thermosetting polymer:
A material which when heated undergoes a chemical change whereby the molecules form rigid cross links.
They cannot be reheated and reshaped, even at very high temperatures.
Elastomer:
A material which at room temperature can be deformed under pressure and then upon release of the pressure, will return to its original shape.
They have weak bonds which allow them to stretch easily. They can be stretched repeatedly and upon immediate release of the stretch, will return with force to the original length.
Give examples of the following polymers:
Thermoplastic:
LDPE, HDPE, PP, HIPS, ABS, PMMA, PET, nylon, PVC.
Thermosetting polymer:
UF, MF, polyester resin, epoxy resin.
Elastomer:
Natural rubber, polybutadiene, neoprene, silicone.
Papers and boards
Names and definitions
Papers and boards can be described as compliant materials, meaning that they can be scored, folded and cut with basic tooling to form items such as nets for packaging.
Give examples of papers and boards
- Layout paper
- Cartridge paper
- Tracing paper
- Bleed proof paper
- Treated paper
- Watercolour paper
- Corrugated card
- Bleached card
- Mount board
- Duplex card
- Foil backed card
- Laminated card
- Metal effect card
- Moulded paper pulp
Composites
Names and definitions
A material comprised of 2 or more different materials, resulting in a material with enhanced properties.
Composites can be:
* Fibre based
* Particle based
* Sheet based
Give examples of the following composite materials
- Fibre based
- Particle based
- Sheet based
- Fibre based:
CFRP, GRP, fibre concrete. - Particle based:
Tungsten carbide, concrete. - Sheet based:
Aluminium composite board, engineered wood e.g., glulam.
Smart materials
Names and definitions
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
Names and definitions
A material developed through the invention of new or improved processes, e.g., as a result of man-made materials or human intervention.
(Modern materials are not ‘smart materials’ because they do not react to external change).
Methods for investigating and testing materials:
Give the 2 main categories of tests (names)
- Simple workshop tests (comparative)
- Scientific measured tests (Industrial).
Definition
Tensile testing
1 - Clamping material samples of the same length and thickness into a vice
2 - Applying a load such as weights to the unclamped end.
Shows:
How much the material deflects under the load and / or how much load each material can bear with the least deflection.
Results:
The less deflection under load, the more tensile strength the material has.
Definition
Toughness testing
1 - Material samples are clamped into a vice.
2- Each sample is then hit with the same force, using a hammer.
Shows:
How much impact force the material can absorb.
Results:
Tough materials will absorb the impact, whereas brittle materials may bend or shatter.
Definition
Hardness testing
2 aspects:
* Abrasive wear
* Resistance to surface indentation.
Abrasive wear:
Run a file over the surface of the material, using the same force for each material sample.
* Material with the fewest scratches is the hardest.
Resistance to surface indentation:
Use a dot punch and a hammer; material sample is fully supported underneath and the dot punch is placed onto the material surface. Dot punch is then hit once with a hammer, using the same force for each material sample.
* The smaller the indent, the harder the material.
Definition
Malleability and ductility testing
Same test is used using 1 test piece.
1- Secure the test piece in a vice.
2- Try to bend the test piece to 90 degrees.
Results:
Lack of ductility = cracks or surface damage on the OUTSIDE of the bend.
Lack of malleability = Cracks or surface damage on the INSIDE of the bend.
Definition
Corrosion testing
Used to determine rate of corrasion for material when exposed to environmental effects (i.e., rain / sun)
1- All test pieces should be same size.
2- Materials simply placed outside in an area exposed to weather effects
3- Left for certain length of time
4- Materials can then be visually inspected for surface corrosion.
Further testing e.g., hardness could be carried out.
Definition
Conductivity testing
2 types:
* Electrical conductivity
* Thermal conductivity.
Electrical conductivity:
Tested using a multi-meter.
1- Collect material samples of the same dimensions
2- On the top surface, mark a set distance between the two ends of the material sample.
(The distance is the spacing for each probe of the multi-meter).
3- Place the probes on the distance marks
4- Measure the resistance on the multi-meter.
Results:
The higher the resistance, the lower the conductivity.
Industrial tests definition
Usually carried out in a lab at a materials testing facility with specific testing machinery, using standardised test pieces of a material.
Tensile testing: Industrial
Definition
1 - A standard test piece is placed into a tensometer machine and held in clamps at each end.
2- One clamp is fixed and the other moves on a worm drive fear mechanism.
3- As the worm drive travels at a constant rate, the test piece is put under tension.
4- As the test piece is stretched, the load and distance travelled is plotted, giving information on elastic limit, yield point, maximum load and final breaking point after ‘necking’.
Toughness testing
Definition
(Industrial)
- Izod impact test
1- A notched test piece is held vertically in the vice of the test machine.
2- A pendulum is released from a set position and swings to strike the test piece.
3- The energy absorbed by the test piece is calculated from the height the pendulum swings to after it hits the test piece.
Results:
The material that absorbs the most impact is the toughest.
This is shown by the distance the pendulum swings after breaking the material.
The further it swings, the less energy the sample absorbs and the more brittle the material.
Harness testing
Definition
(Industrial)
3 tests:
* Rockwell
* Brinell
* Vickers pyramid.
Ductility and malleability industrial testing
A bend test
(How well a material can withstand cracking during 1 continuous bend)
1- The test piece is paced into a bending machine and held, supported at the ends.
2- A mandrel or plunger loads the test piece at the centre and bends it to a predetermined angle, or until the test piece fractures.
3- The material is then inspected for cracks or defects.
Results:
Ductility levels = Cracks on the outer bend.
Malleability levels = Cracks on the inside of the bend.
(A ductile material will have a lot of plastic deformation prior to failure).
Non destructive testing
Definition + names of types
Carried out on products such as large castings where there is a liklihood of an internal defect of imperfection which would not be detected by other methods.
Types:
* Ultrasonic
* X ray
Ultrasonic testing
Definition
Industrial (type of non-destructive testing)
1- A transducer generates sound waves which are pulsed into the material.
2- The intensity of the reflected sound waves signal is recorded on a display unit.
3- The sound waves travel through the material and if there are any defects such as cracks in the sound waves’ path, the sound energy will be partially reflected and shown on the display unit.
Advantages:
- Performed on all types of materials
- Portable
- Has a high accuracy of flaw detection
X ray testing
Definition
Industrial (type of non-destructive testing).
1- An x-ray bream passes through the material and an image is projected onto a display screen.
2- X-rays and micro-focus x-rays allow the observation of tiny details within the material.
3- The magnified images enable minute flaws such as voids or hairline cracks to be reliably detected.
Electrical conductivity (industrial)
Definition
4-point probe method:
1- Four small-diameter wires are stretched, parallel to each other across a non-conductive polymer block, held in place and connected to copper terminal blocks.
2- Two leads are attached to the inner wires and two to the outer wires.
3- The outer leads are connected to a precise current and the two inner leads measure the voltage drop.
4- Ohm’s law (V=IR) can then be used to calculate the resistance of the material sample.
Thermal conductivity (industrial)
Definition
1- Using a heat flow meter, a square-shaped material test piece is placed between 2 temperature controlled plates.
2- The temperature is increased at a controlled rate and the heat flow through the material is measured by heat flow sensors placed on the surface of the material.
3- As the material is heated to a specific temperature, the sensors measure and record the rate of thermal conductivity.
