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Longman Dictionary of Contemporary English
torsion
noun
EXAMPLES FROM CORPUS
▪ A helix is any line in which the curvature and torsion measured anywhere and everywhere are in a constant proportion.
▪ As with tensile and bend testing, torsion testing may be done under various stress or displacement programs.
▪ Curvature and torsion are not easy to measure directly but their being proportional has a straight forward measurable consequence.
▪ End effects and errors due to misalignment are very important in torsion testing.
▪ In the latter case the specimen is of near perfect geometry for a torsion test.
▪ Or a partial torsion of the gut ...?
▪ Precisely similar effects occur in the large strain torsion of a rubber.
▪ Rear Suspension - Two transverse torsion bars are located within a hollow tube and operated by trailing arms.
The Collaborative International Dictionary
Torsion

Torsion \Tor"sion\, n. [F., fr. LL. torsio, fr. L. torquere, tortum, to twist. See Torture.]

  1. The act of turning or twisting, or the state of being twisted; the twisting or wrenching of a body by the exertion of a lateral force tending to turn one end or part of it about a longitudinal axis, while the other is held fast or turned in the opposite direction.

  2. (Mech.) That force with which a thread, wire, or rod of any material, returns, or tends to return, to a state of rest after it has been twisted; torsibility.

    Angle of torsion (of a curve) (Geom.), the indefinitely small angle between two consecutive osculating planes of a curve of double curvature.

    Moment of torsion (Mech.) the moment of a pair of equal and opposite couples which tend to twist a body.

    Torsion balance (Physics.), an instrument for estimating very minute forces, as electric or magnetic attractions and repulsions, by the torsion of a very slender wire or fiber having at its lower extremity a horizontal bar or needle, upon which the forces act.

    Torsion scale, a scale for weighing in which the fulcra of the levers or beams are strained wires or strips acting by torsion.

Douglas Harper's Etymology Dictionary
torsion

early 15c., "wringing pain in the bowels," from Old French torsion "colic" (early 14c.), from Late Latin torsionem (nominative torsio) "a wringing or gripping," from Latin tortionem (nominative tortio) "torture, torment," noun of action from past participle stem of torquere "to twist, distort, torture" (see torque (n.)). Meaning "act or effect of twisting as by opposing forces" is first recorded 1540s.

Wiktionary
torsion

n. 1 The act of turning or twisting, or the state of being twisted; the twisting or wrenching of a body by the exertion of a lateral force tending to turn one end or part of it about a longitudinal axis, while the other is held fast or turned in the opposite direction. 2 (context mechanics English) That force with which a thread, wire, or rod of any material, returns, or tends to return, to a state of rest after it has been twisted; torsibility.

WordNet
torsion
  1. n. a tortuous and twisted shape or position; "they built a tree house in the tortuosities of its boughs"; "the acrobat performed incredible contortions" [syn: tortuosity, tortuousness, contortion, crookedness]

  2. a twisting force [syn: torque]

Wikipedia
Torsion

Torsion may refer to:

  • In geometry:
    • Torsion of a curve
    • Torsion tensor in differential geometry
    • The closely related concepts of Reidemeister torsion (also called R-torsion, Franz torsion, de Rham torsion) and analytic torsion (also called Ray-Singer torsion)
    • Whitehead torsion
    • Dihedral angle
  • In algebra:
    • Torsion (algebra)
    • Tor functor
    • Torsion-free module
  • In medicine:
    • Of bones, "torsion fracture" is another term for spiral fracture.
    • Of organs, torsion refers to twisting, in particular twisting that interrupts the blood supply to that organ, e.g. splenic torsion, ovarian torsion, or testicular torsion.
    • Torsion of the digestive tract in some domestic animals:
      • A type of horse colic
      • One complication of bloat (gastric torsion)
  • In physics and engineering:
    • Torsion (mechanics)
    • Torsion coefficient
    • Torsion pendulum
    • Torsion spring or -bar
  • In science and pseudoscience
    • Torsion balance, a delicate measuring instrument used in scientific research
    • Torsion field (pseudoscience), a field alleged to make faster-than-light communication and paranormal phenomena possible, a theory by Russian scientists
    • The field used in Einstein–Cartan theory and other alternatives to general relativity that involve torsion of spacetime
  • In biology:
    • Torsion (gastropod), a developmental feature of all gastropods
  • In warfare:
    • Torsion siege engine, a kind of catapult
Torsion (algebra)

In abstract algebra, the term torsion refers to elements of finite order in groups and to elements of modules annihilated by regular elements of a ring.

Torsion (mechanics)

In the field of solid mechanics, torsion is the twisting of an object due to an applied torque. Torsion is expressed in newton per squared meter (Pa) or pound per squared inch (psi) while torque is expressed in newton metres (N·m) or foot-pound force (ft·lbf). In sections perpendicular to the torque axis, the resultant shear stress in this section is perpendicular to the radius.

For shafts of uniform cross-section the torsion is:


$$T = \frac{J_T}{r} \tau= \frac{J_T}{\ell} G \theta$$

where:

  • T is the applied torque or moment of torsion in Nm.
  • τ is the maximum shear stress at the outer surface
  • J is the torsion constant for the section. It is almost equal to the second moment of area J = I for twisting about axis z. For more accuracy, finite element analysis (FEA) is the best method. Other calculation methods include membrane analogy and shear flow approximation.
  • r is the distance between the rotational axis and the farthest point in the section (at the outer surface).
  • is the length of the object the torque is being applied to or over.
  • θ is the angle of twist in radians.
  • G is the shear modulus, also called the modulus of rigidity, and is usually given in gigapascals (GPa), lbf/in (psi), or lbf/ft.
  • The product J G is called the torsional rigidity w.
Torsion (gastropod)

Torsion is an anatomical event which takes place during the very early part of the life of snails and slugs of all kinds. In other words, torsion is a gastropod synapomorphy which occurs in all gastropods during larval development. Torsion is the rotation of the visceral mass, mantle, and shell 180˚ with respect to the head and foot of the gastropod. This brings the mantle cavity and anus to an anterior position above the head.

In some groups of gastropods ( Opisthobranchia) there is a degree of secondary detorsion or rotation towards the original position; this may be only partial detorsion or full detorsion.

The torsion or twisting of the visceral mass of larval gastropods is not the same thing as the spiral coiling of the shell, which is present in many shelled gastropods.

Usage examples of "torsion".

The torsion or rotation of leaves and leaflets, which occurs in so many cases, apparently always serves to bring their upper surfaces into close approximation with one another, or with other parts of the plant, for their mutual protection.

Caddy mentions a youth of eighteen who had congenital torsion of the penis with out hypospadias or epispadias.

From the particulars above given, and remembering in the case of twining plants and of tendrils, how difficult it is not to mistake their bending to all points of the compass for true torsion, we are led to believe that the stems of this Ceratophyllum circumnutate, probably in the shape of narrow ellipses, each completed in about 26 h.

Gay describes a child with epispadias whose penis had undergone such torsion on its axis that its inferior surface looked upward to the left, and the child passed urine toward the left shoulder.

The curve, or distortion, of the spine increases more rapidly as the body becomes heavier, the spine often assuming the shape of the letter S, and, from compression by torsion of the vertebrae and distortion of the ribs, the vital organs are encroached upon, causing serious functional derangement of the heart, lungs, liver, and stomach, producing, as its inevitable consequence a list of maladies fearful to contemplate.

The torsion or rotation of leaves and leaflets, which occurs in so many cases, apparently always serves to bring their upper surfaces into close approximation with one another, or with other parts of the plant, for their mutual protection.

Although we can see how the slight periodical movements of leaves in a vertical plane could be easily converted into the greater yet simple nyctitropic movements, we do not at present know by what graduated steps the more complex movements, effected by the torsion of the pulvini, have been acquired.

And she stood by the window, not quite facing me, shapely and fair, all that elegant velocity bottled behind her, concealed torsion bars and disc brakes, the poise of fine machinery, and her body then, softly turning, seemed to melt into the rippling glass.

Poll, Maggie and a horse-leech from the starboard watch have been administering enemas to the many, many cases of gross surfeit that have now replaced the frostbites, torsions and debility of the recent past, the very recent past.

A parikha, one of the creatures the colonists of Santa Cruz erroneously call birds, has built its nest in the upper angle of the bogie wheel torsion arm.