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Young's modulus

In materials science the Young's modulus or modulus of elasticity (and also elastic modulus) is a measure of the stiffness of a given material. It is defined as the limit for small strains of the rate of change of stress with strain. This can be experimetally determined from the slope of a stress-strain curve created during tensile tests[?] conducted on a sample of the material.

The Young's modulus allows engineers[?] and other scientists to calculate the behavior of a material under load. For instance, it can be used to predict the amount a wire will extend under tension, or to predict the load at which a thin column will buckle[?] under compression. Some calculations also require the use of other material properties, such as the shear modulus[?], density or Poisson's ratio.

For many materials, Young's modulus is a constant over a range of strains. Such materials are called linear, and are said to obey Hooke's law. Examples of linear materials include steel, carbon fiber and glass. Rubber is a non-linear material.

Approximate Young's Moduli of Various Solids

Material Young's modulus (E) in psi
Soft cuticle of pregnant locust 30
Rubber (small strain) 1000
Shell membrane of egg 1100
Human cartilage 3500
Human tendon 80,000
Wallboard 200,000
Unreinforced plastics, polyethene, nylon 200,000
Plywood 1,000,000
Wood (along grain) 1,000,000
Fresh bone 3,000,000
Magnesium Metal 6,000,000
Ordinary glasses 10,000,000
Aluminum Alloys 10,000,000
Brasses and Bronzes 17,000,000
Iron and Steel 30,000,000
Aluminum Oxide (sapphire) 60,000,000
Diamond 170,000,000

See also: Deformation, Stress, Strain

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