1.1 Materials and their applications Flashcards
What is compressive strength?
The ability to withstand being crushed or shortened by pushing forces
What is tensile strength?
The ability to resist stretching or pulling forces
What is bending strength?
The ability to resist forces that bend the material
What is shear strength?
The ability to resist sliding forces on a parallel plane
What is torsional strength?
The ability to withstand twisting forces from applied torque or tension
What is hardness?
The ability to resist abrasive wear such as scratching, indents or cutting
What is toughness?
The ability to absorb impact force without fracture
What is plasticity?
The ability to be permanently deformed (shaped) and retain the deformed shape
What is ductility?
The ability to be drawn out under tension, reducing the cross-sectional area without cracking (ability to stretch without breaking)
What is malleability?
The ability to withstand deformation by compression without cracking, increases with a rise in temperature
What is elasticity?
The ability to be deformed and then return to the original shape when the force is removed
What is a thermal conductor?
Allows the transfer of heat through the material
What is a thermal insulator?
Prevents the transfer of heat through the material
What is an electrical insulator?
Does not allow the flow of electricity through the material
Define opaque
Prevents light from travelling through
Define translucent
Allows light through but diffuses the light so that objects appear blurred
Define transparent
Allows the light to pass through easily
Define density
The mass of the material in a standard volume of space
Define fusibility
The ability of the material to be fused or converted from solid to liquid (essential metal casting)
Define magnetism
The natural force between objects that causes the material to attract iron or steels
What is corrosion/degradation resistance?
The ability of the material to withstand environmental attack and decay
What is a ferrous metal? Give an example
A metal containing iron, they are magnetic and will rust. An example is low carbon steel
What is a non-ferrous metal? Give an example
A metal that does not contain iron. An example is an aluminium
What is an alloy? Give an example
A metal made of two or metals or elements (one must be metal). An example is of a ferrous alloy is stainless steel and an example of a non-ferrous alloy is bronze
What is a hardwood? Give an example
A wood made from a broad-leafed (deciduous) trees. Slow growing trees that lose their leaves in autumn. An example is oak.
What is a softwood? Give an example
A wood made from a coniferous tree. These trees are fast growing. An example is pine
What is a manufactured board? Give an example
A man-made wood-based composite material available in much larger sizes than solid wood. An example is plywood and MDF.
What is a thermoplastic polymer? Give an example
A material which can be repeatedly reheated and reshaped allowing it to be recycled after its initial use. They have long linear chain molecules. An example is polypropylene.
What is a thermosetting polymer? Give an example
A material which when heated, forms rigid cross-links. Thermosetting polymers cannot be reheated and reshaped. An example is epoxy resin.
What is an elastomer? Give an example
A material that can be deformed under room temperature at room temperature. They have weak bonds which allow them to be stretched easily. E.g Rubber and neoprene. Used in tyres, wetsuits etc
What are paper and boards? Give examples of both
Compliant materials that can be scored, folded and cut with basic tools. Examples are tracing paper and corrugated card
What are composites? Give examples
Materials comprised of two or more material, resulting in a material with the enhanced properties. They can be fibre based, particle-based and sheet based. Examples are glass fibre reinforced plastic and concrete
What are smart materials? Give examples
A material whose physical properties change in response to an input or change in the environment such as electricity, pressure. temperature or light. An example is a shape memory alloy.
What are modern materials? Give examples
A material developed through the invention of new or improved processes. An example is kevlar
What is tensile testing?
Clamping material samples of the same length and thickness into a vice and applying a load such as weights to unclamped end. The amount of deflection can be observed, the less deflection under load the more tensile strength material has.
What is toughness testing?
Materials samples are clamped into a vice and then hit with the same force using a hammer. Tough materials will absorb impact but brittle materials may bend or even shatter.
What is hardness testing? (Abrasion and indentation testing)
Abrasive wear: Can be tested by running a file over the surface of a material. The material with the fewest scratches is the hardest.
Resistance to surface indentation: Put a dot punch on the material and then hit with a hammer. The smaller the indent the harder the hammer.
What is malleability and ductility testing?
Secure test piece to vice and try to bend the material 90 degrees. Cracks or surface damaged on the outside indicate a lack of ductility and cracks on inside show a lack of malleability.
What is corrosion testing?
Place material outside in a area exposed to weather effects left for a certain length of time. Materials can be visually inspected for surface corrosion.
What is conductivity testing? (electrical and thermal)
Electrical testing can be testing using a multimeter. The higher the resistance, the lower the conductivity.
Thermal conducitity can be tested using a thermometer. Heat the material at one end with the bunsen burner and roecord the time it takes to reach the set termperture on the other end.
What is ultrasonic testing?
Used to detect cracks in materials
What is x-ray testing?
Used to detect voids or hairline cracks and inspect integrated circuits and printed circuit boards.
What is thermal conductivity testing?
Using a heat flow meter, a material is placed between two temperature controlled plates, the temperature is increased at a controlled rate and heat flow through the material is measured by heat flow sensors that record and measure the rate of thermal conductivity.
What is electrical conductivity?
A four-point probe is used. Four small-diameter wires are stretched, parallel to each other across a conducive polymer block. Leads are attached to inner wires and two to the out wired. The outer leads are connected to a precise current and the two inner leads measure the voltage drop. Ohms law used to calculate resistance.
Industrial tensile testing
A standard test piece is placed into a tensometer machine and held in clamps at each end. One clamp is fixed and the other moves on a worm drive hear mechanism, as the worm drive at a constant rate, the test piece is put under tension. As the rest piece is stretched, the load and distance travelled are plotted, so the elastic limit, yield point and maximum point can be found.
Industrial toughness testing
The Izod impact test. The test piece is held vertically in the vice of a test machine. A pendulum is released from a set position and swings to strike the test piece. The energy absorbed is shown but the distance the pendulum swings after breaking ht material. the firth is swung the less energy the sample absorbed.
What is the Rockwell test?
A diamond indenter breaks through the surface of the material with a preload to be used as the zero position. An additional predetermined load is then applied to the rest material for a certain amount of time. The load is taken off and the distance between the preload and applied load is measured.
What is the Brinell test?
A steel ball is forced into a pre-set load. The diameter of the indent is measured.
What is the Vickers pyramid test
A diamond square based pyramid is used to indent on the surface of the material. Diamond is used because it will not deform under load. A microscope is used to measure the size of the indent.
Industrial ductility and malleability testing
A bend test is used to determine how well a material can withstand cracking during one continuous bend.
A test piece is placed into a bending machine and a mandrel loads the test pieces at the centre and bends it to a predetermined angle or until it fractures.
Why is aluminium suitable for a drinks can?
- It is malleable so it can be drawn into shape
- Lightweight which makes it easier to life and transport
- A food safe material
- Non ferrous
- Very easy to recycle as it has a low melting point
Why is teak suitable for an outdoor garden bench?
- Contains natural oils resistant to moisture
- Natural oils resist acids and alkalis, so won’t degrade due to bird droppings or cleaning detergents
- Aesthetically pleasing - dark brown/red colour and straight grain
- Hard so will resist scratches from items like buttons on jeans
Why is PET suitable for a drinks bottle?
- Thermoplastic so it can be recycled
- Tough
- Available in transparent form
- Impermeable to Co2 so its good for carbonated drinks
Why is MF suitable for a kitchen worktop?
- Thermosetting so will not be affected by hot pans placed on the surface
- Chemical resistant so the table top can be cleaned with detergent.
- Hard so won’t be scratched by scouring pad
- Can be pigmented
Why is Neoprene is suitable for a wetsuit?
- Elastomer so the wetsuit will stretch to fit tightly
- Good degradation resistance so won’t be damaged by salt water
- Can be pigmented
Why is corrugated card suitable for takeaway food containers?
- Compliant and easy to cut using a die cutter
- Food safe
- Insulator due to air pockets within the corrugations
- Lightweight
- Recyclable
- Biodegrable
Why GRP suitable for a boat hull?
- Manufactured using the lay up method which means complex shapes can be created
- Pigmented
- Chemical resistance
- Tough
Why is thermochromatic film suitable for thermometres?
- Changes colour in response to temperature
- Easier to read than numbers
- Non-toxic (safer than mercury)
- Incorporated into a film strip making it flexible (to go on forehead)
