Mod 1: Engineering fundamentals

• Metals vs non metals
• Semiconductor is an element that is polymorphic in nature and can be a conductor
• Insulators do not conduct electricity well
• Simple engineering mechanics:

  • Lever: force acting over a distance to minimise it, ex, crowbar
  • inclined planes: they’re more useful and better to make an object move up
  • Inclined plane: mg sin(theta), vertically: mg
  • Screws: An inclined plane wrapped around a shaft
  • Wheel and Axle: Allows turns and transportation
  • Pulley: transfers linear to rotational to linear motion
  • Gears: Provide transfer of rotational energy, and can also be used in ratios to move faster/slower.
  • Chain drives: Similar to pulleys and gears
• Elements: cannot be broken down into simpler materials

  Solutions: where one substance dissolves into another, solute and solvents

  Compounds: the result of two or more elements, can be broken down into elements

  Mixture: two or more pure substances, elements or compounds mixed,
• Materials can be classified According to their properties Elements, solution, compounds or mixture - chemical
• Ionic bond: when an atom shares an electron with another atom due to valency

  
• Covalent bond: sharing electrons

  
• Metallic bond, since the electron shells are far away, metal atoms are positive ions, positive ions repel other positive ions, thus metal is a conductor.

  
• Crystal structure: important structures in engineering applications, include body centred cubes, face centred cubes, and hexagonal close packed

  
• Polymorphism, exists in two or more crystalline structure, ex, ice being ice in <0°, however, water at >0°
• Ferrous metals: have iron as the main constituent

  Non Ferrous metals: don't have iron as the main constituent
• Mild steel: most common form of steel
• Stainless steel: has ferrous alloys and at least 10% chromium
• Ferrous metals can be divided into pure iron and steels
• Non ferrous metals include: copper, brass, aluminium, aluminium bronze, bronze
• Basic forming processes to handle metals include: casting, rolling, extruding, joining metals, metallurgical methods, soldering, mechanical joining, cutting, fabricating
• Properties of materials include:

  Mechanical

  Physical

  Chemical

  Electrical

  Magnetic

  Thermal
• Mechanical properties include:

  Lustrous: shiny

  Sheerness: how sharp

  Hardness: the ability of a material to resist scratching, abrasion, indentations

  Elasticity: to return to it's original shape and dimensions

  Stiffness: resist elastic transformations

  Plasticity: ability of material to go under some degree of permanent deformation

  Malleability: ability to be hammered and rolled into thin sheets

  Ductility: to be drawn into a thin wire

  Fatigue: tendency of material to break under repeated cyclic loading

  Notch toughness: measure of amount of energy to cause failure
• Physical properties:

  Porosity:

  Moisture content:

  Density:
• Thermal properties include heat resistance and thermal conductivity
• Electrical properties include electrical conductivity
• Chemical properties include the behaviour of a material under all chemical reactions
• Orbital valency goes as:

  First shell: 2

  Second shell: 8

  Third shell: 8

  Fourth shell: 18
• Polymers:

  • Formed by linking monomers together
  • They are made of long plastic chains
  • Good electrical insulators
  • strong. However, low temperatures stability
  • produced from crude oil, so long-term issues might arise
• Addition polymerization: when two or more different monomers are added together

  
• Condensation polymerization: some monomers condensed to form a byproduct.

  
• Thermoplastics have covalent bonds and secondary, weaker bonds which cause viscosity when heat is applied. Thermosets have covalent bonds both ways and cannot be resoftined. Thus, they are more rigid have less elasticity
• Ceramics: both thermal and electrical insulators
• Types of ceramics include clay body ceramics, glass, gorilla glass
• Composites, materials made from different materials to improve properties. These also include Fibre reinforced polymers
• Ionic bonds affect non metals and metals. Covalent bonds affect non metal and non metals, but also non metals and metals. Metallic bonds affect metals
• Ionic bonds is when electrons are given to another atoms, due to valency. Electrons during covalent bonds are shared simultaneously between atoms. Electrons flow in an electron sea in metallic bonds since all atoms are positive ion.
• When electrons are given in an ionic bond, the metal becomes a positive ion as it has less electrons to neutralize it, meanwhile, the non metal become a negative ion, meaning that it has more electrons to neutralize it. This leads to an attraction in the positive and negative ions, leading to a bond.
• A lattice refers to a regular repeating pattern throughout the material. These patterns lead to lattice units, where BCC, FCC, and HCP crystalisation structures can be formed.
• Van der Waals bonding: a weak bonding that arises from positive and negative ions when joining two bodies' surfaces. This is likely the reason why static friction is higher than kinetic friction.
• Spot welding


  When an electric current creates a pressure on the metal, melting it in spots
• Butt welding

  When an electric current applies pressure on a metal, melting it and creating a joint between two tubes
• Seam welding

  When a metal is pushed through two wheels which have an electric current passing through them, melting the metal, joining them
• Oxy-acetylene welding

  When the metal is melted through oxy-acetylene flames and filler metal is added