Unit 4: Raw Material to Final Product

• Physical properties


  Characteristic of materials that can be identified through non-destructive testing, although some deformation is required to test hardness
• Mass


  Relates to the amount of matter contained in a specific material, a constant unlike weight which varies depending on location
• Weight


  Relies on mass and gravitational forces to provide a measurable value, technically measured as a force
• Volume


  The quantity of three-dimensional space enclosed by a closed boundary
• Density


  The mass per unit volume of a material, important for portability in terms of a product's weight and size
• Electrical resistivity


  A measure of a material's ability to conduct electricity, important for selecting conductors or insulators
• Thermal conductivity


  A measure of how fast heat is conducted through a material, important for objects that will be heated or must conduct or insulate against heat
• Thermal expansion (expansivity)


  A measure of the degree of increase in dimensions when an object is heated, important where two dissimilar materials are joined
• Hardness


  The resistance a material offers to penetration or scratching, important where resistance to penetration or scratching is required
• Mechanical properties


  Properties related to a material's ability to withstand various forces and stresses
• Tensile strength


  The ability of a material to withstand pulling forces, important for ropes and cables
• Compressive strength


  The capacity of a material or structure to withstand loads tending to reduce size
• Stiffness


  The resistance of an elastic body to deflection by an applied force, important when maintaining shape is crucial to performance
• Toughness


  The ability of a material to resist the propagation of cracks, good with resisting high impact
• Ductility


  The ability of a material to be drawn or extruded into a wire or other extended shape, important for extrusion
• Malleability


  The ability for materials to be shaped easily, the property of a substance that makes it capable of being extended or shaped by hammering or by pressure from rollers
• Young's modulus


  A measure of the stiffness of an elastic material, defined as the ratio of stress to strain in the elastic region

  
• Stress


  Force per unit area
• Strain


  Ratio of deformation over initial length

  
• Elastic region


  The straight line region where stress and strain are directly proportional, and the material can regain its original shape after removal of load
• Yield point


  The point where the material will not return to its original shape, marking the start of the plastic region
• Plastic region


  The region where the material will not return to its original shape after load removal
• Ultimate stress point or fracture point


  The point where the material has completely failed
• Aesthetic characteristics


  Properties that make a product interesting, appealing, likeable, or unattractive, based on personal preferences
• Taste


  The ability to detect the flavour of substances such as food and poisons
• Smell


  The ability to perceive odors, which can evoke memories and emotions
• Appearance


  How something looks, including factors like colour, masculinity/femininity, style, etc. that appeal to different demographics
• Texture


  The properties and sensations caused by the external surface of objects, received through the sense of touch
• Colour


  The visual perceptual property corresponding to categories of colours, with optical, emotional, and symbolic effects
• Smart materials


  Materials that have one or more properties that can be dramatically altered, influencing their application
• Piezoelectricity


  • A property where electricity is generated when a piezoelectric material is deformed, and the material can change size when an electric current is passed through it
• Design contexts where properties of smart materials are exploited


  • Sensors in different electronic devices
• Smart materials


  Materials that have one or more properties that can be dramatically altered, for example, viscosity, volume, conductivity
• Type of Smart Material


  • Piezoelectricity
  • Shape memory alloy (SMA's)
  • Photochromicity
  • Magneto-rheostatic
  • Electro-rheostatic
  • Thermoelectricity
• Piezoelectricity


  1. Pressure acting upon the material gives off a small electrical discharge

  2. When an electric current is passed through it, it increases in size (up to a 4% change in volume)
• Piezoelectric materials


  • Used as sensors in different environments
  • Used in the airbag sensor on a car as it senses the force of an impact on the car and sends an electric charge to activate the airbag
• Shape memory alloy (SMA's)


  Metals that exhibit pseudo-elasticity and shape memory effect due to rearrangement of the molecules in the material
• Shape memory alloy (SMA's)


  • Pseudo-elasticity occurs without a change in temperature or electrical voltage
  • The load on the SMA causes molecular rearrangement, which reverses when the load is decreased and the material springs back to its original shape
  • They can be used to make products for durable and harder to break, e.g. glasses frames
  • The shape memory effect allows severe deformation of a material, which can then be returned to its original shape by heating it
• Photochromicity


  Material that can have a reversible change of colour when exposed to light
• Photochromic materials


  • Colour-changing sunglass lenses, which can darken as the sun light intensifies
  • A chemical either on the surface of the lens or embedded within the glass reacts to ultraviolet light, which causes it to change form and therefore its light absorption spectra