# Young's modulus

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## Young's modulus

[for Thomas YoungYoung, Thomas,
1773–1829, English physicist, physician, and Egyptologist. He established (1799) a medical practice in London and was elected (1811) to the staff of St. George's Hospital there.
], number representing (in pounds per square inch or dynes per square centimeter) the ratio of stress to strain for a wire or bar of a given substance. According to Hooke's law the strain is proportional to stress, and therefore the ratio of the two is a constant that is commonly used to indicate the elasticityelasticity,
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
of the substance. Young's modulus is the elastic modulus for tension, or tensile stress, and is the force per unit cross section of the material divided by the fractional increase in length resulting from the stretching of a standard rod or wire of the material. See strength of materialsstrength of materials,
measurement in engineering of the capacity of metal, wood, concrete, and other materials to withstand stress and strain. Stress is the internal force exerted by one part of an elastic body upon the adjoining part, and strain is the deformation or change in
.
The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.

## Young’s Modulus

the modulus of elasticity that characterizes the ability of a material to resist extension. Young’s modulus E = σ/∊, where σ is the normal stress that occurs in tension and ∊ is the relative elongation that results from the stress. The modulus was introduced by T. Young in 1807.

## Young's modulus

[′yəŋz ‚mäj·ə·ləs]
(mechanics)
The ratio of a simple tension stress applied to a material to the resulting strain parallel to the tension. Also known as modulus of elasticity
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.

## Young's modulus

A constant designated E, the ratio of stress to corresponding strain when the material behaves elastically. Young's modulus is represented by the slope E = ΔS/Δ&epsiv; of the initial straight segment of the stress-strain diagram. More correctly, E is a measure of stiffness, having the same units as stress: pounds per square inch or pascals. When stress and strain are not directly proportional, E may be represented as the slope of the tangent or the slope of the secant connecting two points on the stress-strain curve. The modulus is then designated as tangent modulus or secant modulus at stated values of stress. The modulus of elasticity applying specifically to tension is called Young's modulus. See Elasticity, Stress and strain

McGraw-Hill Concise Encyclopedia of Engineering. © 2002 by The McGraw-Hill Companies, Inc.

## Young’s modulus

In an elastic material which has been subject to strain below its elastic limit, the ratio of the tensile stress to the corresponding tensile strain.
McGraw-Hill Dictionary of Architecture and Construction. Copyright © 2003 by McGraw-Hill Companies, Inc.
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