Plasticity (in Physics) fundamentals

Last updated on December 14th, 2023 at 03:29 pm

Plasticity is the ability of a solid material to undergo permanent deformation, a non-reversible change of shape in response to applied forces. This means that once the force is removed, the material will not return to its original shape.

Plasticity is a key property of many metals, polymers, and other materials, and it is essential for many engineering and manufacturing processes. Plasticity is also known as plastic deformation. Related posts: Elasticity

Plasticity

When a material is subjected to a high magnitude of external force, its interatomic particles leave their old lattice points and become distant from each other. This results in a permanent deformation of the material. This is termed plasticity.

At the microscopic level, plastic deformation occurs through dislocation, a process where crystal lattice defects move and allow for lasting changes in the material’s structure.

Temperature, pressure, and strain rates are crucial factors influencing plasticity. Controlling these variables empowers scientists and engineers to predict and control how materials will deform under different conditions, leading to informed material design.

Example: A common example of plasticity is a solid piece of metal being bent or pounded into a new shape. The metal exhibits plasticity as stable changes occur within the material itself.

Distinguishing Plasticity from Elasticity

Elasticity is the property of a body to recover its original configuration (shape and size) when the deforming forces are removed. On the other hand, plasticity is the property of a body to lose its property of elasticity and acquire a permanent deformation on the removal of deforming force.

Elasticity vs. Plasticity

Elasticity and plasticity are distinct phenomena. Elastic materials, when stretched or compressed, spring back to their original form when the deforming forces are removed. In contrast, plasticity involves enduring changes, with materials retaining their deformed shape even after the removal of the deforming force. This distinction is fundamental in understanding how materials respond to different types and magnitudes of stress.

Examples

To illustrate the difference, consider a rubber band and a piece of clay. Pulling a rubber band causes temporary deformation, but it returns to its original shape once released—this is elasticity. On the other hand, shaping clay involves permanent changes, exemplifying plasticity.

Elastic plasticity

Elastic plasticity is a type of plasticity that combines both elastic and plastic deformation properties of a material. Elasticity refers to the ability of a material to return to its original shape after the applied stress is removed, while plasticity is the ability of a material to undergo a non-reversible change of shape in response to an applied force. Elastic plasticity occurs when a material initially deforms elastically, but once it reaches its yield point, it exhibits plastic deformation. This type of plasticity is observed in many materials, particularly metals, and is a key aspect of their deformation behavior. Understanding elastic plasticity is crucial for designing and optimizing materials for various applications, ensuring their performance and longevity.

Plasticity – Applications

Applications: Plasticity has various applications in areas such as metal forming, machining, additive manufacturing, and material design for high-temperature components (such as turbine blades). It also plays a significant role in geological processes like rock folding and rock flow under the earth at very high pressures and rising temperatures.