Elastic and plastic behavior

Elastic deformation

Where a material returns to its original shape once the force applied is removed

• All work done is stored as elastic strain energy

Plastic deformation

Where a material’s shape is changed permanently

• Work done stored as elastic strain energy and heat energy

Work done/elastic strength (potential) energy

Area under line **until limit of proportionality

Equation for elastic strain energy (potential)

• ½ Fx

• ½ kx²

UNTIL limit of proportionality

Diagram + features, elastic deformation

Area under graph = Work done/elastic potential

Diagram for brittle/plastic

• Brittle: extends very little, likely to break apart at low extension

• Plastic: Material experiences large amount of extension as load increased, especially beyond elastic limit

Diagram - material stretched beyond elastic limit

• Unloading will not return to origin

• Stiffness is constant, parallel loading and unloading lines

• Area between loading and unloading = work done to permanently deform