Definition - What does Plasticity mean?

Plasticity is the propensity of a material to undergo enduring deformation under load when compressed. It is the quality or state of being plastic; especially the capacity for being molded or altered.

The plasticity of a material is directly proportional to the ductility and malleability of the material. Ideal plasticity is a property of materials to undergo irreversible deformation without any increase in stresses or loads.

Plasticity may cause fracture or rupture of material. Plasticity also causes plastic deformation, which occurs in many metal-forming processes, including:

  • Rolling/pressing
  • Forging
  • Wire drawing

Corrosionpedia explains Plasticity

Certain solids have the ability to flow or to change shape permanently when subjected to stresses between those that produce temporary deformation, or elastic behavior. This property of solids is called plasticity. In physics and materials science, plasticity is the deformation of a material undergoing non-reversible changes of shape in response to applied forces.

For example, a solid part of metal being bent or pounded into a new shape exhibits plasticity as stable changes occur within the material itself.

Plasticity in metals is typically a result of dislocations. In brittle materials like rock or concrete, plasticity is caused predominantly by slippage at microcracks. Plastic materials with hardening require increasingly elevated stresses to result in further plastic deformation.

Plasticity in a crystal of pure metal is primarily caused by two modes of deformation in the crystal lattice: slipping and twinning. Most metals show more plasticity when warm than when cold. This property is of significance in forming/shaping and extruding operations on metals. Most metals are rendered plastic by heating, and hence are shaped hot. The presence of dislocations increases the likelihood of planes slipping.

Inelastic deformations of rocks and concrete are primarily the result of the formation of microcracks and sliding motions comparative to these cracks. At elevated temperatures and pressures, plastic behavior can also be affected by the motion of dislocations in individual grains in the microstructure.

The causes of plasticity in soils can be quite complex and are strongly dependent on:

  • Microstructure
  • Chemical composition
  • Water content

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