GCSE ENGINEERING - Y11 MOCK
ENGINEERING MATERIALS
What is the difference between proactive/reactive maintenance
Proactive maintenance is carrying out actions to prevent a product failing, while reactive maintenance is repairing a broken product
List and explain different types of proactive maintenance
Lubrication - using a liquid to help reduce wear and friction between moving parts
Avoiding corrosion - Corrosion can consume the affected material and reduce mechanical properties
Compensating for wear - adjusting the position of parts to allow for wear
List the advantages and disadvantages of fossil fuels
Advantages include that fossil fuels are produced as they are needed and can respond to sudden demands in energy and power stations are already operational so there is less of a need for new investment
Disadvantages include that by products of burning can release greenhouse gases which contribute to global warming and prices may increase as they are becoming more scarce
List the advantages and disadvantages of nuclear energy
Advantages include the ability to produce energy consistently every day and respond to change in demand
Disadvantages include that incorrect operation can lead to radioactive materials released into the environment and causing damage to human health. Radioactive waste is also very difficult to dispose of
State 3 types of steel, their properties and uses
Low carbon steel - tough and stronger than non ferrous metals. Cannot be hardened. Used for nails/screws/car bodies
High carbon steel - Strong, hard, difficult to form, can be hardened. Used to make tools like hammers/chisels/saw blades
Stainless steel - Strong, hard, corrosion resistant, but difficult to machine. Used for kitchen utensils
MANUFACTURING PROCESSES
Explain the process of sintering
Mould of the product is made and filled w/metal powder
High pressure is applied using an industrial press. Powder is heated below melting point causing particles of the metal powder to fuse together
State two advantages of sintering
Energy efficient - metals are not heated above melting point.
Metal powders can be mixed, products can be made with lower densities by using air gaps in the structure
How do saws work?
Saws use movement to cut away material.
They contain lots of teeth that make grooves in the material
Teeth are angled out so the groove is wider than the blade, so the blade is less likely to get stuck
Name the different types of saws and what they cut
Hacksaw/junior hacksaw - polymers, metals
Coping saw - timbers, polymers
Tenon/rip saw - structural timber
Jigsaw - most types of material and thicknesses
What is sand casting used for, when is it used and why
Sand casting is used to make metal parts from a mould made from bonded sand
It’s commonly used to make small quantities of parts, as moulds are not reusable so it would take a lot of time to create them, and there is a risk of variation in the moulds.
Explain the process of sand casting
Wooden pattern split into half and placed inside the drag/moulding box
Sand is poured over the pattern in the box, then rammed around the pattern and levelled off
The box is then turned over and the other half of the moulding box is placed on top. The second half of the pattern is then fitted onto the first half of the pattern
Pins are fixed, then sand is poured and rammed around the pattern
Pins along with the top half of the mould are removed, then the pattern is removed
Box is put back into position and channels are cut to the cavity for metal to be poured through
Describe what galvanising is and what it’s used for
Industrial process where steel is dipped in a bath of molten zinc to form a coating
It’s often used to make dustbins, buckets, nuts/bolts/screws
List an advantage and disadvantage of galvanising
Advantage - improves corrosion resistance and durability of the steel
Disadvantage - Coated parts are not visually attractive
How would you fold a sheet of metal into a box shape?
Cut the metal sheet into a net for a box. The net should include tabs.
The metal net sheet can be folded along the edges by gripping it in a bending bar and hitting it with a mallet
SYSTEMS
What is the difference between static and dynamic loads
Static/dead loads are constant forces
Dynamic/live loads are forces that vary over time and are not constant
Explain how static/dynamic loads affect a bridge
Static loads - Components that rest on the bridge such as poles, buildings
Dynamic loads - Wind blowing against the bridge, the weight of cars
Define buckling
The sudden deformation of a structural component under load
Describe what a monocoque structure is and state examples where it’s used
A structure that uses an external shell to support the load required
Used in aircraft bodies/car chassis
List advantages/disadvantages of monocoque structures
Advantages - fewer potential weak points, relatively lightweight and stiff
Disadvantages - Subject to buckling under too much compressive stress
What are semi-monocoque structures and state the advantage
Semi monocoque structures have underlying frame structures as well as an external skin to support the load required. This is ideal to help structures withstand higher compressive stresses.
Used in modern jet airliners for this reason
What do inputs/processes/outputs do?
Input - Take a signal from the real world and convert it into a signal the process block can understand (light/sound to current/voltage)
Process - Change the signal (increase/decrease size)
Output - Convert the new signal into a real world signal (motion/heat)
Describe what a flow chart is and state what the symbols are for
A flow chart is a diagram that shows the order in which events are carried out in a system
Oval - terminator
Parallelogram - input/output
Rectangle - process
Diamond - decision
What are some things to remember when drawing schematics?
Label every component with it’s type and identifying number
Show the value of components
Describe what linkages are and what they do
Linkages are systems consisting of rods connected with pivots
Their purpose is to change the size of a force/direction of motion/size of motion
State 3 types of linkages and what they do
Reverse motion linkage - reverses the direction of movement
Parallel motion linkage - the input and output rods move in the same direction
Bell crank linkage - changes horizontal movement to vertical movement
State the definition and equation of mechanical advantage
Mechanical advantage is the ability of a mechanism to move a large load with small effort force
Mechanical advantage (MA) = Load (FB) / Effort (Fa)
What is a gear train?
Two or more spur gears meshed together to transmit rotary motion and torque (a rotational force)
What is a chain and sprocket mechanism?
Mechanism that transmits rotary motion using a chain with toothed wheels (sprockets)
What is a cam and follower mechanism?
A mechanism that convers rotary motion into reciprocating motion.
Follower moves up and down as the cam rotates
How are camshafts used in internal combustion engines?
The camshaft is the cylindrical rod that runs the length of the bank of cylinders in the engine
as it rotates, the cams open and close the valves
What is Ohm’s Law?
V = IR
What is the function of a resistor?
Reduces the flow of electrical current in a circuit. Can be used to protect components such as lamps
What is a microcontroller?
A small programmable computer on an integrated circuit for control applications
Explain differences and merits of hydraulic/pneumatic systems
Hydraulic systems are systems that use fluids to control power while pneumatic systems use compressible gas like air
Pneumatic systems are more expensive than hydraulic systems due to the energy required to compress air
Hydraulic systems can produce more force than pneumatic systems, allowing them to be used in heavy lifting or digging applications
Pneumatic systems operate faster than hydraulic systems as air flows quicker than liquids through the system
Pneumatic systems are much cleaner and a risk of hydraulic systems is that liquids are vulnerable to leaking
TESTING AND INVESTIGATION
What is the difference between destructive/non destructive testing? Give an example of each
In destructive testing, the product is tested to the point where it is damaged or destroyed such as crash testing in cars
In non destructive testing, the product is not damaged, this could be ultrasonic testing of the axles on a train
Discuss the advantages/disadvantages of both types of testing
In destructive testing, advantages include that you can find the exact point of failure and find weaknesses that aren’t obvious in normal use of the product
In destructive testing, disadvantages include that the tested object cannot be used again which impacts cost
In non destructive testing, advantages include that you can use it as different stages of the production process and it can save time and costs
In non destructive testing, it is difficult to find the point of failure
Explain basic aerodynamics - lift/drag/thrust
Lift is the force that pushes something upwards. To fly, lift must be greater than weight
The aerofoil of an aircraft wing is shaped as such that air flows faster over the top of the wing, so there is more pressure underneath the wing, pushing it upwards
Thrust is the pushing force that causes something to move forwards. To move, thrust must be greater than drag
Thrust is provided by jet engines or internal combustion engines
Drag is the force that opposes the forward motion of an object in the air, or aerodynamic friction
Drag can be reduced by using rounder and more narrow shapes, as seen in the shape of wings and fast racing vehicles such as dragsters
What is the equation for stress?
Stress = force / cross sectional area
What is the equation for % of waste?
%waste = (waste area / original area) x 100