Materials

• Hooke's Law

  The force applied is directly proportional to the extension, unless the limit of proportionality is exceeded
• what is plastic deformation

  A permanent change in shape that remains once the load is removed.
• springs acting in parallel

  force is split.

  k= k1 + k2 + ......
• springs in series

  1/K = 1/K1 + 1/K2 + .....
• stress-strain curve for metals, ceramics and rubber

  metals - medium height, medium curve

  ceramics - steep height, short curve

  rubber - low height, long gentle curve and doesn't obey hookes law
• whats special about rubber bands

  they return to original extension.

  area under unloading curve is stored epe, between the two curves is converted to thermal energy
• Ultimate tensile strength

  The maximum stress that a material can withstand before it breaks
• elastic limit

  Maximum stress that a material will withstand without permanent deformation.
• brittle

  undergoes little to no plastic deformation before fracture
• ductile

  can be drawn into wires
• malleable

  easy to shape or bend