The Gough–Joule effect (a.k.a. Gow–Joule effect) is originally the tendency of
elastomer
An elastomer is a polymer with viscoelasticity (i.e. both viscosity and elasticity) and with weak intermolecular forces, generally low Young's modulus and high failure strain compared with other materials. The term, a portmanteau of ''elastic p ...
s to contract when heated if they are under
tension
Tension may refer to:
Science
* Psychological stress
* Tension (physics), a force related to the stretching of an object (the opposite of compression)
* Tension (geology), a stress which stretches rocks in two opposite directions
* Voltage or el ...
. Elastomers that are not under tension do not see this effect. The term is also used more generally to refer to the dependence of the temperature of any solid on the mechanical deformation. This effect can be observed in nylon strings of classical guitars, whereby the string contracts as a result of heating.
If an elastic band is first stretched and then subjected to heating, it will shrink rather than expand. This effect was first observed by
John Gough in 1802, and was investigated further by
James Joule
James Prescott Joule (; 24 December 1818 11 October 1889) was an English physicist, mathematician and brewer, born in Salford, Lancashire. Joule studied the nature of heat, and discovered its relationship to mechanical work (see energy). T ...
in the 1850s, when it then became known as the Gough–Joule effect.
''Examples in Literature:''
* Popular Science magazine, January 1972: "A stretched piece of rubber ''contracts'' when heated. In doing so, it exerts a measurable increase in its pull. This surprising property of rubber was first observed by James Prescott Joule about a hundred years ago and is known as the Joule effect."
* Rubber as an Engineering Material (book), by Khairi Nagdi: "The Joule effect is a phenomenon of practical importance that must be considered by machine designers. The simplest way of demonstrating this effect is to suspend a weight on a rubber band sufficient to elongate it at least 50%. When the stretched rubber band is warmed up by an infrared lamp, it does not elongate because of thermal expansion, as may be expected, but it retracts and lifts the weight."
The effect is important in
O-ring
An O-ring, also known as a packing or a toric joint, is a mechanical gasket in the shape of a torus; it is a loop of elastomer with a round cross-section, designed to be seated in a groove and compressed during assembly between two or more par ...
seal design, where the seals can be mounted in a peripherally compressed state in hot applications to prolong life.
The effect is also relevant to rotary seals which can bind if the seal shrinks due to overheating.
References
External links
O-ring Gland design notes, PSP Inc.*
*
Elastomers
Condensed matter physics
Rubber properties
James Prescott Joule
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