PROCESSING MATERIALS

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PROCESSING MATERIALS
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Conditioning Processes

• Magnetic Conditioning
• Magnetizing force lines up the steel molecules in
  one direction
• Thermal Conditioning
• Hardening Heating steel red hot and cooling
  quickly
• Tempering Heating the steel again not quite as
  hot, and cooling it quickly --- it becomes less
  brittle
• Annealing Heating steel ret hot and allowing it
  to cool very slowly --- steel becomes softer
• Mechanical Conditioning
• Hammering a piece of metal --- crystal structure
  gets longer and thinner
• Chemical Conditioning
• Heating a mixture of plaster and water --- the
  plaster hardens
• Examples on page 230

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Use of Computers

• Microwave Oven
• Rolling Mill --- Reheating Furnaces
• Computer-numerical-controlled (CNC) machines and
  robots
• Using a wire-cut machine to cut the profile of a
  die
• A robot can be taught to move through the
  movements needed to do a job --- use of teach
  pendant (remote controller)

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Properties of Materials

• Materials are chosen for their characteristics or
  properties
• Examples copper, glass, nylon, steel etc
• Mechanical Properties
• Drawing wire Making wire from a thick rod
• Ductility A material can be bent, twisted or
  pressed to shape
• Ductile materials are either elastic or plastic
• Elasticity A material comes back to its original
  shape after deformation
• Plasticity A material remains deformed after
  deformation
• Brittleness A material does not deform without
  breaking --- window glass
• Strength A materials ability to keep its own
  shape when a force is applied
• Tension A force that pulls on a piece of
  material
• Compression A force that pushes on or squeezes a
  material
• Torsion Twisting of a material --- twisting
  force itself is called torque

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Properties of Materials

• Mechanical Properties
• Shear force Acts on a material like a pair of
  scissor
• Toughness Ability of material to absorb energy
  without breaking
• Hardness Ability to resist being scratched or
  dented --- diamond is the hardest material known
• The teeth of circular saw blades are often made
  of tungsten carbide
• Electrical Magnetic Properties
• Conductors and insulators
• Silver is the best conductor of electricity
• People make a trade-off by choosing copper
  instead of silver
• Magnetic materials those that can be attracted
  to magnets
• An electromagnet can be made by wrapping wire
  around a piece of iron

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Properties of Materials

• Thermal Properties
• Materials ability to conduct heat
• Copper and aluminum are the two best conductors
  of heat
• Insulation --- a layer of material that does not
  conduct heat
• Optical Properties
• Scientific tools like telescopes use glass that
  transmits light well enough
• Plastic is used in contact lenses and eyeglasses
• Very pure glass is used in glass fibers in
  communication
• Some metals are used as reflectors for headlights
  and flashlights

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Disposal of Resources

• We live in a throw-away society
• Burning --- polluting the air
• Landfills --- polluting the groundwater
• Toxic materials like Lead and Mercury and
  radioactive wastes should be disposed properly
• Materials that do not decompose should be
  recycled
• Material decomposition time --- page 238