Personal and Public Transport Flashcards
effects of engineering innovation in transport on society
As transportation increased in capacity and efficiency, the barriers to trade and communications between villages and nations were reduced. Reliable means of transportation brought vast changes to the performance of commerce, trade, social and cultural perceptions and practices, and to war.
construction and processing materials used over time
bicycle:
frames - aluminium, titanium or carbon fibre.
properties - stiffness, formability, fatigue strength, corrosion resistance, strength/weight ratio, weldability or other appropriate joining method
wheels - cold drawn stainless steel, stainless steel, aluminium spokes.
properties - corrosion resistance or fatigue strength
car:
engine block - flake graphite grey iron, cast aluminium
properties - castability, lightweight, machinability, impact resistance, dimensional stability, thermal conductivity, vibration dampening, high temperature strength
windscreens - laminated glass
properties - rigidity, transparency, optical clarity, thermal stability, impact resistance, scratch resistance, chemical resistance
environmental effects of transport systems
Types of pollutant?
problems associated?
ways to reduce emissions?
motor vehicles emit toxic and carcinogenic compounds such as benzene, formaldehyde and 1,3-butadiene. significant source of ozone-forming pollutants including: hydrocarbons, carbon monoxide, oxides of nitrogen.
toxic and carcinogenic air pollutants from MV are of concern because they pose a threat to humans even at very low levels. damage lung tissue and aggravates respiratory diseases. children and the elderly are vulnerable to smog. Smog inhibits plant growth and can cause widespread damage to crops and forests. air pollution contributes to global warming.
- environmental impact is reduced by: development of cleansing technologies for exhaust gases e.g. catalytic converters.,
- control systems for more efficient fuel consumption e.g. fuel injector systems, engine preheating.
- development of new fuel blends and alternative fuels which have the potential to produce less air pollution
- monitoring and warning systems
- development of electric and hybrid vehicle technologies
- lightweight components
- components that can be easily recycled
- changing car usage patterns e.g. carpooling, cycling,
environmental implications from the use of materials in transport
vehicle production - from extraction of materials to assembly of finished car
- review of painting and coating practices
- elimination of heavy metals and other damaging substances
- design of vehicles for recyclability and maximum use of recycled materials
testing of materials - hardness
hardness refers to the resistance of a material to scratching or abrasion, resistance to indentation, penetration or cutting.
methods: brinell rockwell vickers knoop
testing of materials - impact
charpy: specimen is held horizontally at each end like a beam
izod: specimen is clamped vertically at one end in a cantilever fashion
heat treatment of ferrous metals - annealing
types?
temperature?
carbon content?
what does it achieve?
process annealing: heating of steel with less than 0.3%C to a temperature between 550 and 650°C. to relieve any stress from distorted grains caused by cold working or deformation
full annealing: heating either hypo-eutectoid steels or eutectoid steels into the austenite region at a temperature 40°C above upper critical temperature. then cooled very slowly , usually in a furnace. softer coarser grained steel then previous.
heat treatment of ferrous metals - normalising
what region?
cooling method?
properties?
heating up steel in austenite region. when structure is in austenite it is cooled in still air. takes less time than full annealing and produces finer grained structure and hence a stronger steel.
heat treatment of ferrous metals - hardening and tempering
hardening: if a steel is heated until austenite in structure and quenched rapidly, the transformation from FCC austenite to BCC ferrite is not given enough time to occur fully and the steel is trapped between BCT martensite. Making the structure hard but brittle. martensite will form with a carbon composition greater than 0.03%.
air hardening: if steel has nickel and chromium added in small amounts, then it will have air hardening properties. this means that if it is heated to red hot and cooled in still air, martensite will form. usually molybdenum is also added to reduce brittleness.
tempering: it is possible to sacrifice some hardness to gain toughness through tempering. involves taking a hardened steel and heating it to a temperature between 200 and 600°C. a low tempering temperature will produce high hardness and moderate toughness while a high temp will do the opposite . tempered steels are considerably harder than annealed or normalised steels.
heat treatment of ferrous metals - changes in macrostructure and microstructure
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heat treatment of ferrous metals - changes in properties
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heat treatment of ferrous metals - forging
involve the compression of material held at an elevated temperature between flat or shaped surfaces known as dies. Rapid blows result in the maximum forces to the material occurring as the forging hammer hits the surface. Deformation happens on the surface layers.
Slow compression of the material by a forging press results in deeper penetration of the deformation zone.
The forging process is often defined by whether forging is performed between open or closed dies
heat treatment of ferrous metals - rolling
types?
advantages and disadvantages of both?
properties?
rolling can be done above the recrystallisation temperature (hot rolling) or below the recrystallisation temperature (cold rolling).
hot rolling - used extensively in the production of sheets, strips, bars and rods. when passed through the rollers the metal’s crystal structure is deformed. Since it is above the recrystallisation temperature however, it recrystallises into an unstressed form.
advantages - less stress on the machinery when compared to cold rolling, an unstressed finished product, break up of cast dendritic structure, recrystallisation reduces final austenite grain size, dendrites and inclusions are reoriented, improving ductility in the rolling direction
disadvantages - that the final products are not as dimensionally accurate, it will have a black oxide layer over the finished product.
cold rolling - same procedure as hot rolling but the rollers and machinery are more heavily built, as larger forces are required. The finished grain structure will have distorted grain structure that will produce a harder and stronger final product. These properties come at the expense of ductility and malleability.
Advantages - a harder final product that is more dimensionally accurate, a more presentable product because of the lack of oxides
Disadvantages - greater cost because of heavier machinery
heat treatment of ferrous metals - casting
advantages?
types?
properties?
advantages of casting - large or small products possible, applicable to small or large product runs, complex and hollow shapes with smooth section changes possible, castings made for short-run production allow chemistry batches to be made to order.
die casting, sand casting, and permanent moulding (gravity die casting)
heat treatment of ferrous metals - extrusion
definition?
types?
adv and disadv?
process where a material is placed in a container and subsequently forced to pass through an opeing at one end under plastic flow.
indirect - die is pushing through the metal. (die moves)
direct - ram is pushing metal through die. (die stays still and ram pushes through die).
lubrication must be applied between the container and billet surfaces to reduce frictional forces.
Advantages - billet to final shape, complexity of shapes including tubes, good surface quality and dimensional accuracy.
Disadvantages - expensive equipment, dedicated tooling requirements
