elasticity

elasticity, the ability of a body to resist a distorting influence or stress and to return to its original size and shape when the stress is removed. All solids are elastic for small enough deformations or strains, but if the stress exceeds a certain amount known as the elastic limit, a permanent deformation is produced. Both the resistance to stress and the elastic limit depend on the composition of the solid. Some different kinds of stresses are tension, compression, torsion, and shearing (see strength of materials). For each kind of stress and the corresponding strain there is a modulus, i.e., the ratio of the stress to the strain; the ratio of tensile stress to strain for a given material is called its Young's modulus.

Hooke's law [for Robert Hooke] states that, within the elastic limit, strain is proportional to stress.

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elasticity

Ability of a deformed material body to return to its original shape and size when the forces causing deformation are removed. Most solids show some elastic behaviour, but there is usually a limit—the material's “elastic limit”—to the force from which recovery is possible. Stresses beyond its elastic limit cause the material to yield, or flow, and the result is permanent deformation or breakage. The limit depends on the material's internal structure; for example, steel, though strong, has a low elastic limit and can be extended only about 1% of its length, whereas rubber can be elastically extended up to about 1,000%. Robert Hooke, one of the first to study elasticity, developed a mathematical relation between tension and extension.