plasticity

Ability of certain solids to flow or to change shape permanently when subjected to stresses between those that produce temporary deformation, or elastic behaviour, and those that cause failure of the material, or rupture (see fracture). Plasticity allows a solid under the action of outside forces to become permanently deformed without rupturing; elasticity enables a solid to return to its original shape after the load is removed. Plastic deformation occurs in many metal-forming processes (rolling, pressing, forging, wire drawing) and in geologic processes (rock folding and rock flow within the Earth under extremely high pressures and at elevated temperatures).