2. Personnel and Public Transport - Construction and Processing materials over time Flashcards
The desired materials for engine blocks should be?
- Able to be cast
- Able to be machined
- Resistant to high temperatures
- Resistant to impact loads
- Thermally conductive
- Able to retain its shape under many different circumstances
- Able to dampen the vibrations from the pistons
- Lightweight
What materials could be used for Engine Blocks
Grey cast iron
- Great vibration dampening
- Heavy
- Usually cast in one piece, then machined if this is the case. Called a monoblock if done so.
Aluminium alloys
- Lightweight
- Alloys create a variety of possible mechanical properties
- Some of the alloys used can be from Nickel, Chromium or Magnesium
- Usually Pressure or Gravity casted.
- Occasionally requires the use of cast iron inserts to withstand the loads.
The desired materials for pistons should be
- Able to be machined
- Resistant to impact loads
- Resistant to high temperatures
- Thermally conductive
- Able to retain its shape under varying circumstances
- Lightweight
What materials could be used for pistons
Aluminium
- Lightweight and easily machinable
- Spray coatings may be applied to reduce wear on the cylinder walls
The desired materials for crankshafts should be
(those things that spin to move the pistons up ands down)
- High tensile strength
- High fatigue strength
- Shape stability
- Machinability
Some materials used for crankshafts
Cast iron
- Easy to cast into its intricate shape
- Good wear resistance
- Could be replaced with ductile Carbon steels
- Was used a while ago
- Alloyed steel
- Usually forged and then heat treated to appropriate qualities
- A common alloy is Vanadium
- Lightweight o Better shape stability
- Impact dampening
The desired materials for body panels
- Good strength to weight ratio
- Good surface finish
- Formability
- Toughness/Scratch resistance
- Corrosion resistance
- Weldability and Ease of manufacture
- Recyclability
Materials used for body panels
- Aluminium (Pre-1916)
- Steel and steel alloys
- High formability
- Alloys reduced weight while maintaining tensile strength. o
- Stainless steels also reduce corrosion resistance.
- Alternatives such as Aluminium alloys and thermoplastics allow for recyclability and corrosion resistance
Materials used for wheels
Today cast aluminium, fabricated steel or magnesium alloys are used
Mostly cast aluminium alloys due to their formability, fatigue strength and impact resistance
Material characteristics for tyres
Originally, tyres had no tread pattern. It was introduced in 1916, and vastly improved road-holding abilitiies
Good tyres have high
- Friction/Traction
- Wear resistance
- Shock absorption/Vibration dampening
- Abillity to not fail under petrochemical attacks.
Materials for tyres
Rubber
- Universal material for tires
- New construction methods in 1948 (radial ply) helped improve passenger comfort and reduced wear.
Part 1 How materials in transport have changed over time
- All uses of timber have been replaced by iron, steel, and aluminium over time.
- Iron has been largely replaced by steel except in engine blocks which are still commonly cast iron.
- Aluminium and aluminium alloys have started to replace steel in areas where weight is an issue due to its better strength-to-weight ratio.
- Alloy steels with manganese etc have been developed for specialised uses over plain carbon steels
Part 2 How materials have changed in transport over time
- Stainless steel is now popular for cables and pins due to its high corrosion resistance.
- Carbon fibre is an excellent alternative to aluminium or alloy steel frames due to its high strength-to-weight ratio However when it fails it is sudden and catastrophic.
- Rubber has been replaced with synthetic rubber.
- Polymers have found use where insulation is needed, or when high strength is not important eg cable coverings, dashboards, handles etc
