Materials

• Breaking point


  The point where the UTS has been exceeded.
• Brittle


  Property of a material that does not show plastic deformation and deforms very little under high stress.
• Compressive deformation


  A change in the shape of an object due to compressive forces.
• Compressive forces

  Equal and opposite forces acting on an object to reduce its length or volume.
• Ductile


  Property of a material that has a large plastic region in a stress strain graph, so can be drawn into wires
• Elastic deformation


  A reversible change in the shape of an object due to a compressive or tensile force - removal of force will return the object to its original size and shape.
• Elastic limit


  The value of stress or force beyond which elastic deformation becomes plastic deformation.
• Elastic potential energy


  The energy stored in an object because of its deformation.
• Extension


  The increase in the length of an object when a tensile force is exerted on it.
• Force constant


  Measure of stiffness of a spring
• Hooke's Law


  Force applied is directly proportional to the extension
• Hysteresis loop

  A loading curve obtained when the material in question deforms in different ways when being loaded and unloaded.
• Limit of proportionality


  The value of stress beyond which stress is no longer directly proportional to strain.
• Loading curve


  A force extension graph or stress strain graph.
• Plastic deformation


  Permanent change to the shape of an object due to a compressive or tensile force.
• Polymeric


  Description of a material comprising of long chain molecules, such as rubber, which may show large strains
• Stiffness


  The ability of an object to resist deformation.
• Strong


  A material with a large value for the ultimate tensile strength.
• Tensile deformation


  A change in the shape of an object due to tensile forces.
• Tensile forces


  Equal and opposite forces acting on an object to stretch it.
• Tensile strain


  Extension per unit length.
• Tensile stress


  Force applied per unit cross-sectional area.
• Ultimate tensile strength


  The maximum stress that a material can withstand before it breaks.
• Yield points


  A point on the stress-strain graph beyond which the deformation is no longer entirely elastic.
• Young modulus


  Ratio of tensile stress to strain