Plastic Deformation

Definition - What does Plastic Deformation mean?

Plastic deformation is a process in which permanent deformation is caused by a sufficient load. It produces a permanent change in the shape or size of a solid body without fracture, resulting from the application of sustained stress beyond the elastic limit.

Plastic deformation can be applied in the creation of a variety of items constructed with metal or plastic, and can be conducted under controlled circumstances, or may occur unintentionally.

Plastic deformation is also known as plasticity.

Corrosionpedia explains Plastic Deformation

Plastic deformation is a technique in which enough stress is placed on metal or plastic to result in the object changing its size or shape in a way that is not reversible.

Plastic deformation is seen in most materials, including:

  • Metals
  • Plastics
  • Soils
  • Rocks
  • Concrete

The mechanisms that cause plastic deformation can differ widely. At the crystal scale, plasticity in metals is usually a consequence of dislocations. In brittle materials like rock, concrete and bone, plasticity is caused predominantly by slippage at microcracks. Plastic materials with hardening demand increasingly higher stresses to result in additional plastic deformation.

Heat and pressure are frequently used to shape objects into the desired form. Speed of stress causes rapid material changes, and unable to conform to the pressure, the materials may break. Therefore, plastic deformation used in the manufacture of goods involves cautiously controlling heat and pressure, allowing the structure of the material to adapt to the new conditions and incrementally bending until the preferred shape is obtained.

In plastic deformation an object first goes through elastic deformation, which is reversible, so the object may regain its original shape. Soft thermoplastics have a large plastic deformation range, as do ductile metals like copper, silver and gold. Steel does, too, but not cast iron. Hard thermosetting plastics like rubber, crystals and ceramics have minimal plastic deformation ranges.

Under tensile stress, plastic deformation is characterized by a strain-hardening region and a necking region and finally, fracture, which is also called rupture.

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