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Engineering GCSE Mock Revision (Jo T (PART 2 (Young modulus (image,…
Engineering GCSE Mock Revision
Dogs for Breakfast
Soldering components onto a PCB
Hazards
Fumes whilst soldering
Soldering iron very hot (around 450℃)
Solder can "spit"
Precautions
Return soldering iron to its stand when not in use
Wear goggles in case of solder "spitting"
Keep sponge wet when cleaning
Pneumatic and Hydraulic Systems
Hydraulic
Uses a fluid power system that uses a liquid, such as water or oil
Can produce stronger forces
Cheaper
Uses less energy
Pneumatic
Uses a fluid power system that uses a compressible gas, such as air
Faster
Cleaner
Concrete
Composite material
Compression strength
Tensile strength
Durable
Resists weathering, erosion and other natural disasters, and requires very little maintenance
Polystyrene
Good toughness and impact strength
Good for vacuum forming, injection moulding or extrusion
Health and Safety
Tie your hair
Don't run
Wear safety equipment e.g apron
Stay clear of other people's working spaces
No tripping hazards
Don't mess around with tools
Suck dick just like me
Jo T
How wooden and GRP boat hulls are manufactured?
. Usually, this means starting with a female mold. The mold is first sprayed with gelcoat, then fiberglass cloth is applied, and then resin is used to saturate or “wet out” the fiberglass. When the resin cures, you have a hull or a boat part
How GRP is usd in the lay up method using notes and sketches
The mould is first checked for defects, any scratches etc. are filled.The mould is then polished with a wax polish to a very smooth, high quality finish.
The gel coat is the first layer of resin to be applied to the mould.The gel coat is a mixture of polymer resin, hardener and a pigment mixed in the proportions recommended by the resin manufacturer. An exothermic reaction occurs as the hardener reacts with the resin and heat from the reaction causes the resin to cure and harden.
When the gel coat has cured, a layer of fibre reinforcing material such as strand glass fibre is laid inside the mould and a measured amount of polyester resin mixed with a hardener is stippled and rolled into the reinforcing layer. , another layer of fibre reinforcing material is laid in the mould and resin is stippled and rolled into it. As each layer cures, more layers may be applied until the required thickness is achieved.
When the product has fully cured, it may be removed from the mould. The coloured gel coat that was on the inside of the mould is now the exterior covering of the GRP product
Male mould and Female mould
Male moulds
Male molds are usually less expensive than female molds. Generally, parts formed over a male mold will retain the color and texture of the extruded sheet. Because the plastic sheet shrinks as it cools during the molding process, the thermoformed part sticks to the mold surfaces. To release the part, draft is required.
Draft is the angle the mold wall makes with the vertical. Typically, male molds require greater draft angles than female molds.
With male molds, draft is also used so that plastic parts that are designed to fully nest will release from each other without sticking or jamming.
Female mould
Female molds are usually more expensive than male molds, but a female mold can produce highly detailed parts. With female molds, the mold surface usually produces the exterior surface of the finished parts. This supports the creation of sharp corners and molded-in features such as logos, ribbing, and recesses for name plates. Depending on the part, the inside corners of a female mold may be relatively tight.
Galvanising steel
Galvanised steel is steel that has been coated with zinc in order to prevent rusting / corrosion. Sometimes the galvanising process is referred to as hot dip galvanising. The zinc forms a barrier against corrosion in that the steel underneath does not come into contact with water / moisture in the air.
The hot dipping process applies quite a think layer of zinc to the steel by passing the steel through a molten bath of zinc. The temperature of the zinc is usually in the region of 460 degrees centigrade. The zinc forms a bond with the steel by forming an iron-zinc alloy. The zinc also forms a zinc oxide when it comes in contact with the air which also helps prevent corrosion.
PCB Etching
The PCB mask (now on a transparency) is placed underneath the photo-resist board, touching the sensitive surface. Remember the plastic film must be removed. PCB mask and board are then transferred to the UV light Box.
The lid is shut and the box switched on. The photo-resist board, with PCB mask are left underneath the lid for 2 ½ minutes. The photo-resist board is then placed in a tank filled with developer (using plastic tongs)
It is important that the board is only left in the developer for approximately ten seconds.
When the board is taken out of the developer it must be washed in clean water before transferring to the etching tank..
The etchant is held in a ‘bubble etch tank’ and is heated. This solution slowly etches away the unwanted copper, leaving the tracks only. At this stage it is important to keep checking that the PCB is completed (time - 15 to 45 minutes).
PART 2
Buzzer and piezo
A buzzer or beeper is an audio signalling device, which may be mechanical, electromechanical, or piezo . Typical uses of buzzers and beepers include alarm devices, timers.
Young modulus
Young’s modulus equation is E = tensile stress/tensile strain = (FL) / (A * change in L), where F is the applied force, L is the initial length, A is the square area, and E is Young’s modulus in Pascals (Pa). Using a graph, you can determine whether a material shows elasticity.
Hardness testing
Using a centre punch to ‘indent’ the surface of a material, is a basic test. Different materials require a different amount of force to form an indent. This makes it possible to compare the hardness of a selection of materials.
When using a hand file to ‘file’ a material, the force / effort required can be felt physically . Filing a selection of materials to the same degree, allows the hardness of each to be compared.
A more sophisticated method of measuring the hardness of a material, is to drop a ‘plug’ down a tube. When the ‘plug’ hits the material below, the surface will suffer an indent. The indent produced on different materials, can be compared. Consequently, the smaller the indent, the harder the material.
Toughness test
A simple school workshop test is to hit a sample of material with a hammer, whilst it is secured in an engineers vice. If it survives the blow, without bending too far, it can be said to be tough. If it shatters, it can be said to be brittle.
The industrial device below measures toughness. The pendulum is allowed to ‘swing’ from a set starting position. The resulting ‘distortion’ to the sample material can be measured on the scale. This gives an indication of the materials toughness
Oskar
What are the material properties for ceramics and why is it suitable for sanitary ware such a toilets and washbasins?
Properties: Very good insulator for both electricity and heat, excellent resistance to corrosion, low tensile strength, low ductility and brittle. Also have good compression strength.
They are suitable for sanitary ware due to their wide range of properties
Why are polymers increasingly being used to manufacture products in vast numbers?
Polymers are the most widely used type of material in commercial production. They compromise a large number of similar, smaller chemical units that are bonded together.
Most polymers are synthetic, which means that they are man-made using chemical processes
Advantages and disadvantages of renewable energies:
Wind power- electricity is produced at a low cost
Wind power-only produces energy when there is wind, turbines can be very noisy and take up space
Tidal Power- it is consistent, is out of the way of civilians, can be combined with wind
can be difficult to place in position and can be expensive, can interrupt ecosystems
Biomass- sustainable
less efficient and contributes to global warming
Solar power- requires sunlight, solar panels are expensive, a large area is needed for farms
only produces energy during daylight hours
What are interface electronic components called?
They include: transistors, field effect transistors
Ryan
Metals
Ferrous metals are metals that include iron. examples of ferrous metals are, steel, cast iron, mild steel, carbon steel, and wrought iron. these are often used in bikes, slverware, manhole covers, and more.
Non ferrous metals are metals that don't contain iron. examples of non ferrous metals include aluminium, copper, zinc, gold, and silver
Properties of Metals
Metals have different properties. for example carbon steel and lead are quite brittle. On the other hand, some metals are quite hard such as nickel and tungsten.
Tensile strength is a measurement of the force required to pull something such as rope, wire, or a structural beam to the point where it breaks.
The tensile strength of a material is the maximum amount of tensile stress that it can take before failure, for example breaking.
Compression of materials is when a material is 'squeezed' inwards. It could be described as forces with no net sum or torque directed so as to reduce its size in one or more directions.
Measure of the ability of a material to withstand a twisting load. It is the ultimate strength of a material subjected to torsional loading, and is the maximum torsional stress that a material sustains before rupture. Alternate terms are modulus of rupture and shear strength.
Composite Materials
GRP a fibre-reinforced polymer made of a plastic reinforced by fine fibres made of glass. The composite material may be called glass-reinforced plastic. Fibreglass is cheaper and more flexible than carbon fibre. It is stronger than some metals, and can be moulded into complex shapes.
