5 Types of Corrosion
- Crevice- Galvanic- Pitting- Stress- Exfoliation
5 Corrosion Control Methods
- Sealants- Access for maintenance and inspection- Impressed current cathodic protection- Sacrificial anodes- Selection of appropriate metals - ones that develop protective oxide layer
5 Protective Coatings for Corrosion
- Grease and oil with inhibitors- Plasticised bitumen or resins- Rubber latex- Ceramic coatings (baked enamels)- Paints
2 Roles of Fibre in Fibre Reinforced Composites
- Supports or resists most of applied load- provides stiffness
4 Examples of Fibre Reinforced Composites
- Reinforced concrete- Prestressed concrete- Fibre reinforced polymers (FRP)- Fibre reinforced metals
3 Examples of Fibre Reinforced Polymers
- Graphite-epoxy- Graphite-kevlar-epoxy- Kevlar-epoxy
Example of Cermet
Tungsten-Carbide-Cobalt
Graphite-epoxy Usage
Used widely in aircraft and motor racing industry
Laminated Thermoset Plastic
Polymer impregnated into paper under pressure initiating polymerisation. Used for insulation and decorative surfaces
Five Alloys of Plain Carbon Steel
Low Carbon SteelMild SteelMedium Carbon SteelHigh Carbon SteelUltra-High Carbon Steel
Three Features Grey Cast Iron
- Graphite present as flakes- Stress concentrations occur at sharp ends- Graphite voids allow easy machining and damping properties
5 Crack Detection Tests
Dye Penetrant Inspection (DPI), Magnetic Particle Testing, Eddy Current Testing, Ultrasonic Testing, Radiography
Dye Penetrant Inspection (DPI)
Part is dipped in dye then washed away, developer is added leaving visible dye filled cracks - only for surface cracks
Magnetic Particle Testing
Fine magnetic particles are applied to surface. Part is magnetised to reveal surface and shallow defects because of stray EMF
Eddy Current Testing
Detects variation in an induced electromagnetic field
3 Advantages of Non-Ferrous Alloys
- Greater ductility- Lower density- Higher thermal and electrical conductivity
4 Properties of Aluminium Alloys
- Youngs modulus of 70 GPa compared to 210GPa for Steel- High electrical conductivity- Good corrosion resistance due to oxide layer- Low mass - used on high voltage power lines
2 Properties of Zinc Alloys
Low melting point and high corrosion resistance
3 Roles of Matrix in Fibre Reinforced Composites
- Adheres to fibre to transmit forces to fibres- Protects strands from damage- Prevents crack propagation
2 Types of Prestressed Concrete
Pre and Post Tensioned Concrete
3 Parts of the Composition of Concrete
- Aggregate - comprises 2/3 of the volume and must be angular- Sand - fills voids between aggregate minimising porosity, increasing cement life- Cement and water forms glue between sand and aggregate
Five Properties of Metals
- Lustrous- Solid at Room Temp- Malleable- Ductile- Good Conductors
3 Common Metal Structures
- Body Centered Cubic- Face Centered Cubic- Close Packed Hexagonal
Four Cast Irons
- Grey Cast Iron- Nodular/Spheroidal (SG) Graphite Cast Iron- White Cast Iron- Malleable Cast Iron
3 Conditions for Corrosion
- Presence of electrolyte like water- Presence of anode and cathode- An electrical contact between anode and cathode
2 Examples of Particle Reinforced Composites
- Cermet- Concrete
Tungsten-Carbide-Cobalt
Used for cutting tools - tungsten carbide particle cuts then fractures off the cobalt matrix to expose fresh sharp tungsten carbide
3 Examples of Laminates
- Plywood- Laminated Timber Beams- Laminated Thermoset Plastic
Four Properties of Non-Metals
- Dull- Brittle- Non-conductors- Cant Form Alloys
4 Properties of Ceramics
- Hard and brittle- High compressive low tensile strength- Low conductivity- Chemically inert
Three Steps of Grain Growth
1. Solidification into structure begins at nucleation points2. Grain dendrites grow (tree like)3. Grain boundaries form
Two Alloy Groups of Iron (C)
Steel - <2%Cast Iron - 2-4%
Eight Components of Alloy Steel
- Nickel- Chromium- Manganese and Silicon- Molybdenum- Tungsten- Vandium- Stainless Steels- High Speed Tool Steels
Silicon in Steel (%)
>1.5% used to aid formation of graphite
Four Annealing Processes
- Full Annealing- Process Annealing- Normalising- Spheroidising Annealing
5 Advantages of Aluminium Alloys
- Tensile strength up to 400MPa- Corrosion resistance- Weldability- Casting ability- Oxide non-toxic for food stuffs
3 Properties of Titanium Alloys
High specific strength, melting point and excellent corrosion resistance
Why Does Alloying Strengthen Materials
Disruptions in uniform atomic structure block slip planes
3 Points about Glass
- Glass is an amorphous solid - no regular crystalline structures - makes it transparent- Glass cannot be shaped by force - slip of atoms cannot occur- Very weak in tension - window will break on impact
4 Points about Cement
- Formed by complex reaction when aluminium oxide, soda and lime react at high temperatures- Strong in compression, weak in tension- Exhibits low toughness- Similar properties to stone with the advantage of casting
Points about Concrete
- Sand fills the gaps between the aggregate- Cement acts as the binder/matrix that hold the sand and aggregate together- The sand and aggregate bulk out the cerment, reducing the price and increasing strength
2 Points about Laminated Glass
- Used for shatter-resistance- Layers of glass are passed through roller that compress a polymer sheet between them