Outline the function of the wheel and axle
- Wheels and axles allow motors to turn and mowers to be pushed
Outline the function of pulley systems
- The pulley allows the user to apply a force at a different location or in a different direction
Outline the function of gears
- Allow rotational motion to be transferred from one shaft to another
What is polymorphic material
- When a material exists in multiple crystal structures
What is amorphous material
- Materials that when in their solid state have to crystal structure
What is crystalline material
- A material that possesses a crystal structure
Explain reasons for the use of mild steel
mild steel is used most commonly as it is easily formed, machined and welded and is quite ductile- with 0.3% carbon
Explain reasons for the use of non-ferrous metals
- Non-ferrous metals such as copper can be used to make alloys such as brass with 40% zinc and bronze with 40% tin
Compare ferrous metals and non-ferrous metals
- Ferrous metals have high tensile strength but are at an increased risk of corrosion due to the high iron content- Non ferrous metals have low tensile strength and minimal corrosion risk
Identify thermosetting polymers
- PA, ABS, PC, PMMA, PLC
Identify thermos softening polymers
- PET, HDPE, PVC, LDPE, PP, PS
Identify types of ceramics
- Clay body- Glass- Refractory
Identify forming and shaping methods for ceramics
Potters wheel, Slip Casting, Glass sheets (rolling), Hot isostatic pressing
Outline properties and uses of timber
- excellent specific strength and reasonable performance in bending. Adversely affected by the weather and is prone to attack by pests , such as termites. Useful and renewable (under the right circumstances).- Hardwood can be used for feature pieces but not renewable
Outline properties and uses of concrete
- Cement + sand + aggregates = concrete- Is hard but brittle solid. A stronger and more efficient way to make large structures or paths than cement alone. Concrete is usually reinforced with steel (rebar) to improve its resistance to bending
Identify common alloy materials
- Aluminium, copper, iron
Explain the concept of potential difference
- The difference in electrical potential energy between two points in an electrical field
Explain the concept of current
- The flow rate of charge
Explain the concept of simple circuits and its components
- A simple circuit must be composed of a source of voltage, a conductive path and a resistor
Explain the operation of an induction motor
- In an induction motor a cage of electromagnets that switch on and off in sequence to replicate the motion of a moving magnet. As the induction motor moves its magnetic field around the stator, this induces a magnetic field in the conducting rotor at the centre. This rotor current creates a magnetic field that interacts with the stator's magnetic field. This creates torque causing the rotor to turn.
Distinguish between AC and DC current transmission
- AC without any alteration has a current that alternates direction as it moves. DC current has a single direction current as it moves
Explain the operation of electric motors
- Motors convert electrical energy into mechanical energy
Explain how motors convert electrical energy into mechanical energy
- As the motor moves its magnetic field around the stator, this induces a magnetic field in the conducting rotor at the centre. This rotor current creates a magnetic field that interacts with the stator's magnetic field. This creates torque causing the rotor to turn.
Explain the operation of a generator
- Generators convert mechanical energy into electric energy
Distinguish between extension/load, stress and strain
- Stress is an internal reaction that occurs in response to an externally applied load- Can be tensile or compressive stress- Strain is the proportional change in length when under axial load
Identify health and safety issues relevant to biomedical engineering
- Through the link to the health industry they have the risk of exposure to disease and radiation and must undergo training that ensures that they are aware of how to handle and dispose of chemical and hazardous waste.
Describe the forming process for materials used in biomedical engineering
- Forging titanium femoral stem will provide better fatigue and impact resistance due to the consistent grain direction ensuring no points will crack off and become lose in the human body
Distinguish between parallel and series circuits
- Parallel circuits are those where the current splits between multiple pathways.- Series circuits have only one pathway for the electrons
Criteria for AND gate to be on
- A and B = on
Criteria for NAND gate to be on
- Anything but and (both) = 1
Criteria for OR gate to be on
- Either or both = on
Criteria for NOR gate to be on
- None on = 1
Criteria for NOT gate/inverter to be on
Output is always opposite
Criteria for XOR/exclusive OR gate to be on
- Only one on = 1
Evaluate the importance of stress/strain diagrams in understanding properties of materials
- In the one graph engineers are able to asses a wide range of properties the material has like elastic limit, upper/lower yield stress, ultimate tensile strength and breaking point
Describe the concept of shear force
- Shear force is the force an object experiences when being sheared apart
Describe the concept of bending moment
- At any given point along a beam the bending moment is equal to the total moment developed at that point by the external force system- In equilibrium
Describe the concept of neutral axis and outer fibre stress
- When a beam is bent down the upper side experiences tension, the lower experiences compression and the point in the moment where they meet is the neutral axis where it is experiencing neither compression or tension
Describe the impact of uniformly distributed loads on a simple beam
- Reduces the chance for bending or cracking
Examine how failure due to cracking can be repaired or eliminated
- Drill a hole at the head of the crack to prevent further development of the crack
Outline x-ray and gamma testing of concrete
- Used to detect cavities or defects- Gamma penetrates better than x-rays
Explain special properties produced by composite materials
- Higher specific strength
Compare simple reinforced, pre-tensioned and post-tensioned structures
- Pre-tensioned involves placing tension in rod/cables before concrete is poured- Post-tensioned involves pouring the concrete into the mould first and when set, the steel tendons are inserted in the conduits- Simple reinforced concrete involves placing steel rebar embedded into the concrete while being poured
Evaluate significance of galvanic corrosion/dissimilar metals in civil structures and their prevention methods
- A local form of corrosion restricted to certain components of an article- sacrificial annodes
Evaluate significance of stress cells in civil structures and their prevention methods
- When there is a difference in the levels of stress in a metal, the high-stress region becomes the anode and it rusts.
Differentiate between oxidation and reduction
- Oxidation is gain- Reduction is loss- OILRIG
Differentiate between anode and cathode
- Anode = Aluminium and Zinc- Cathode = gold and platinum- Use sacrificial anode on metal prone to corrosion
Describe the environmental impact of energy requirements for transport systems
- Electricity travels well through wires as opposed to the transportation of fossil fuels being directly used like diesel or petrol moving the pollution away from heavily populated areas- Ultimately moving the problem away
Outline the development and technological change of trains and its impact on society
- RAIL (horse drawn) STEAM DIESEL ELECTRIC- As the technology changed and trains became more efficient through using more effective methods of power and more convenient paths for travel, they became a more desirable method of transport as they are a reliable method of transport that leaves a smaller carbon footprint per person
Explain annealing and the subsequent changes in properties
- FIRE, heat to 100% austenite, cooled slowly in a furnace- Large unstressed equiaxed grains of ferrite and perlite- Soft and ductile- ALOHA NEAL- Process annealing is done at a lower temperature with unstressed ferrite but stressed pearlite
Explain normalising and the subsequent changes in properties
- AIR, Heat to 100% austenite then cool in air- Small uniform grains- Harder stronger and less ductile than annealing
Explain hardening and tempering and the subsequent changes in properties
- WATER, Heat to 100% austenite then quench in oil or salt bath resulting in martensite- Acicular grain structure, stressed and brittle- THEN TEMPER Heat up between 200-600 and cool- Very hard, strong and not too brittle
Explain solid solution/precipitation hardening and the subsequent changes in properties
- Heat to 100% austenite then quench
Hypereutectoid
- Pearlite surrounded by a network of Cementite- Greater than 0.83% carbon
Hypoeutectoid
- Ferrite and pearlite- Less than 0.83% carbon
Eutectoid
- Any steel with 0.83% carbon
Above critical eutectoid temperature
austenite
Explain the method and application of forging
- Heated to plastic deformation and shaped by an impact force into the required shape- Wrenches and crankshafts
Explain the method and application of rolling
- Metal is forced through large rollers under pressure- When the rollers are heated different results- I beams, rails
Explain the method and application of extrusion
- Forces the metal through a die- Rods and tubing
Explain the method and application of casting
- Molten metal is poured into a mould then allowed to cool
Explain the method and application of power forming
- Metal in powder form is blended with dry lubricants, pressed into a mould, need enough pressure to compact particles together. Then sintered in a controlled atmosphere furnace at temp to allow atoms diffuse- Produces homogenous structure
Explain the method and application of oxy-acetylene welding
- Bottle and torch as brazing to provide heat while a rod builds up the joint- Flux isn't needed due to low temp
Explain the method and application of arc welding
- Uses high voltage 'arcs' produced by completing a conductive circuit from the power source to the electrode/filler metal- Need skill
Explain the method and application of stick/smaw welding
- Rods act as the electrode and provide filler metal coated in flux (looks like corndog)- Used on sight
Explain the method and application of mig welding
- Filler metal is a continuous wire, instead of flux there is a protective layer of argon, due to this it can only be done in enclosed spaces- easiest
Explain the method and application of TIG welding
- for stainless steel and aluminium- tungsten electrode conducts the arc and the filler metal is supplied from separate rods- no flux is needed weld is protected by inert gas
Benefits of flux
- Creates a protective shield that prevents impurities- 'shell' is chipped off and weld is cleaned
Where is case hardening used and why?
- Hammers, good hardness and tensile strength, exterior is brittle- Soaked in carbon rich atmosphere
Where is Flame hardening used and why?
- Gears- Hard surface area- Used on the exterior of metals from a flame holder and then quenched
Where is Induction hardening used and why?
- Camshafts in engines- Easily machined- Applies heat with induction coil to desired range for heat treatment
What is Hot forging
- Forging done above recrystallisation temp
What is Cold forging
- Forging done below recrystallisation temp
What is Drawing
- Draw out metal while reducing cross sectional area
What is Upsetting
- Reducing length while increasing cross sectional area
What is Hot rolling
- Rolling done above recrystallisation temp for less stress on machinery- More expensive and leaves black oxide coating
What is Cold rolling
- Rolling done below recrystallisation temp- More dimensionally accurate results- Harder stronger at expense of ductility and malleability
What is Sand casting
- Casting done with a binder packed around shape- Molten metal poured in- Only used once
Benefits of Continuous casting
- Fast production- Long metal strips than can be cut to size
Benefits Shell moulding
- Good for symmetrical objects- Better than sand casting worse than die
Benefits of Die casting
- Create a permanent mould that is reused
What is Investment casting
- Pattern out of wax, covered in ceramic, melted and molten replaced, cast is broken in the process
Outline and describe parts of the plane
- Fuselage houses flight crew, passengers and freight. Pressurised and allows people to survive at high altitudes- Wing provides a large majority of the lift to support aircraft's weight, different shapes are used depending on the purpose of the aircraft- Ailerons are an outboard trailing edge of the wing. Used to control roll- Flaps are inboard trailing edge sections used to generate additional lift during low speed manoeuvring and landing- Horizontal stabiliser (tailplane) provides a downwards force to keep the aircraft level and stable- Elevators are trailing edge sections of the horizontal stabiliser used for pitch control- Elevons covers the function on both the elevator and ailerons, used on high performance delta wing aircraft- Fin (vert stabiliser) provide yaw stability and control, acts together with the rudder- Rudder is the trailing edge of the fin- Undercarriage provides a means of manoeuvring on the ground
Describe the function of aileron, elevator and rudder
- Aileron = roll- Elevator = pitch- Rudder = yaw
Define weight, lift, thrust and drag
- Weight is the gravitational force on the aircraft mass (weight down)- Lift is a force generated by the airflow over the wing and tailplane (Bernoulli's principle) (arrow up)- Thrust is a forward force caused by the power plant (arrow forward)- Drag is the force resisting the movement of the aircraft through the air(arrow away) split into induced [developed as a result of lift production] and parasitic drag [aircraft shape through air]