Principles of Engineering

 

Categories of Materials
•Organics
  • are or were living organisms
  • Composed of mostly carbon and Hydrogen
  • Renewable, sustainable
  • Genetically alterable
•Metals

Metals

  • Metals are pure elements which comprise about three-fourths of the periodic table
  • Few are used in their pure form because of:
  • Hardness; too hard or too soft
  • Cost; scarcity of element
  • Engineers need certain characteristics that can only be accomplished by a blending of basic elements
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Examples:
 aluminum - copper - gold - zinc - iron - lead - nickel
silver - thorium - chromium - tin - beryllium

Alloys
  • Consist of materials composed of  two or more elements, at least one being a metal
  • Steel- iron, carbon and impurity elements such as boron copper or silicon
     

    Examples:
     Brass - copper, zinc

    Stainless Steel - nickel,iron
    Monel - nickel,copper

    Types of Metallics:

Ferrous Metallics - iron and alloys which contain at least 50% iron (e.g. wrought iron, cast iron, steel, stainless steel)

Nonferrous Metallics - Metallic elements other than iron (e.g. copper, lead, tin, zinc, titanium, beryllium, nickel)

Powdered (Sintered) Metals (ferrous or non-ferrous)

Sometimes called sintered metal.  A process of producing small (powdered) particles which are compacted in a die and then “sintered” (applying heat  below the melting point of the main component)

Examples:
trigger on gun, gears, bearings, carbide tool inserts

 
•Polymers

Polymers

  • Human-made polymers
  • Plastics are workable or moldable
  • Thermosetting plastics are formable once (e.g. epoxy, phonelic (Bakelite), polyurethane)
  • Thermoplastics  can be heated repeatedly and formed into new shapes (e.g. polyethylene, nylon, Plexiglas)
Elastomer

  • amorphous (shapeless) structure consisting of long coiled-up chains of entangled polymers
  • can be stretched at room temperature to at least twice its original length and return to its original shape after the force has been removed
  • Process to strengthen an elastomer: vulcanization
  • a chemical process used to form strong bonds between adjacent polymers to produce a tough, strong, hard rubber (automobile tires)
Ceramics

Ceramics

  • Crystalline compounds combining metallic and non metallic elements
  • The absence of free electrons make ceramics poor electrical conductors. 
  • Because of the strength of the bonding, ceramics have high melting temperatures
cCategories:
  • nClay - brick, floor and wall tiles, drainage tile, roof tile, sewer pipe, chimney flue, china, and porcelain
  • nRefractory - all-silica insulating tiles on the U.S. space shuttle
  • nElectrical and Magnetic - resistors and heating elements for furnaces
  • nGlass
  • nCermets - crucibles, jet engine nozzles
Composites

Composites

  • Laminar or Layer Composites - alternate layers of materials bonded together.  (e.g. plywood, safety glass, Formica, bimetallic strips)
  • Particulate Composites - discrete particles of one material surrounded by a matrix of another material.  (e.g. concrete, asphalt, powdered metals and ceramics)
  • Fiber-Reinforced Composites - composed of continuous or discontinuous fibers embedded in a matrix of another material.  (e.g. Kevlar, rayon, steel reinforced tires, fiberglass, graphite-epoxy)