WordNet

turn in the opposite direction; "twist ones head"
twist suddenly so as to sprain; "wrench ones ankle"; "The wrestler twisted his shoulder"; "the hikers sprained their ankles when they fell"; "I turned my ankle and couldnt walk for several days" (同)sprain, wrench, turn, wrick, rick
form into twists; "Twist the strips of dough"
turning or twisting around (in place); "with a quick twist of his head he surveyed the room" (同)turn
social dancing in which couples vigorously twist their hips and arms in time to the music; was popular in the 1960s; "they liked to dance the twist"
a jerky pulling movement (同)wrench
form into a spiral shape; "The cord is all twisted" (同)twine, distort
practice sophistry; change the meaning of or be vague about in order to mislead or deceive; "Dont twist my words" (同)twist around, pervert, convolute, sophisticate
do the twist
a twisting force (同)torque

PrepTutorEJDIC

〈糸・なわなど〉‘を'『よる』,より合わせる(糸・なわなどに)…‘を'よる《+名+into(in)+名》 / …‘を'よって(より合わせて)作る,なう;(…から)…‘を'よって作る《+名+from(out of)+名》 / (…に)…‘を'『巻きつける』,からませる《+名+around(《英》round)+名》 / …‘を'ねじる,よじる,しぼる / 〈足首・関節など〉‘を'くじく,ねんざする / 〈顔など〉‘を'ゆがめる,しかめる;…‘を'ゆがめて(…に)する《+名+into+名》 / 〈言葉・文章など〉‘の'意味を曲げる,‘を'曲解する / …‘を'回す,‘の'向きを変える / よじれる,ねじれる,ゆがむ / 身をよじる,体をくねらせる / 縫うように進む,曲がりくねる / 〈C〉『より合わせること』;より,ねじれ,ゆがみ / 〈C〉より合わせて(よって)作ったもの(より糸,なわ,ねじりパンなど) / 〈C〉(意味などを)ねじ曲げること,曲解,こじつけ / 〈C〉(道・流れなどの)曲がり,くねり / 〈C〉(性質・態度などの)癖,かたより,ゆがみ / 〈C〉(事件などの)意外な急変 / 〈C〉〈U〉(野球で)カーブ,曲球 / 《the ~》ツイスト(1960年代に流行した体をひねって踊る強烈な踊り)
ねじること,ねじり,ねじる力,ねじれ

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出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2013/01/30 00:34:15」(JST)

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[Wiki en表示]

Torsion of a square section bar.

In solid mechanics, torsion is the twisting of an object due to an applied torque, therefore is expressed in N·m or 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:

where:

is the maximum shear stress at the outer surface
J_T is the torsion constant for the section. It is identical to the second moment of area J_zz for concentric circular tube, or round solid shafts only. For other shapes J must be determined by other means. For solid shafts the membrane analogy is useful, and for thin walled tubes of arbitrary shape the shear flow approximation is fairly good^[1], if the section is not re-entrant. For thick walled tubes of arbitrary shape there is no simple solution, and finite element analysis (FEA) may be the best method.
r is the distance between the rotational axis and the furthest point in the section (at the outer surface).
ℓ 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 or more commonly the modulus of rigidity and is usually given in gigapascals (GPa), lbf/in² (psi), or lbf/ft².
The product J_T G is called the torsional rigidity w_T.

Properties

The shear stress at a point within a shaft is:

Note that the highest shear stress is at the point where the radius is maximum, the surface of the shaft. High stresses at the surface may be compounded by stress concentrations such as rough spots. Thus, shafts for use in high torsion are polished to a fine surface finish to reduce the maximum stress in the shaft and increase its service life.

The angle of twist can be found by using:

Sample calculation

The rotor of a modern steam turbine.

Calculation of the steam turbine shaft radius for a turboset:

Assumptions:

Power carried by the shaft is 1000 MW; this is typical for a large nuclear power plant.
Yield stress of the steel used to make the shaft (τ_yield) is: 250 x 10⁶ N/m².
Electricity has a frequency of 50 Hz; this is the typical frequency in Europe. In North America the frequency is 60 Hz.

The angular frequency can be calculated with the following formula:

The torque carried by the shaft is related to the power by the following equation:

The angular frequency is therefore 314.16 rad/s and the torque 3.1831 x 10⁶ N·m.

The maximal torque is:

After substitution of the polar moment of inertia the following expression is obtained:

The diameter is 40 cm. If one adds a factor of safety of 5 and re-calculates the radius with the maximal stress equal to the yield stress/5 the result is a diameter of 69 cm, the approximate size of a turboset shaft in a nuclear power plant.

Failure mode

The shear stress in the shaft may be resolved into principal stresses via Mohr's circle. If the shaft is loaded only in torsion then one of the principal stresses will be in tension and the other in compression. These stresses are oriented at a 45-degree helical angle around the shaft. If the shaft is made of brittle material then the shaft will fail by a crack initiating at the surface and propagating through to the core of the shaft fracturing in a 45-degree angle helical shape. This is often demonstrated by twisting a piece of blackboard chalk between one's fingers.

References

^ Case and Chilver "Strength of Materials and Structures

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English Journal

Guided torsional wave generation of a linear in-plane shear piezoelectric array in metallic pipes.

Zhou W1, Yuan FG2, Shi T3.
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Cylindrical guided waves based techniques are effective and promising tools for damage detection in long pipes. The essential operations are generation and reception of guided waves in the structures utilizing transducers. A novel in-plane shear (d36 type) PMNT wafer is proposed to generate and rece
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On the scattering of elastic waves from a non-axisymmetric defect in a coated pipe.

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Viscoelastic coatings are often used to protect pipelines in the oil and gas industry. However, over time defects and areas of corrosion often form in these pipelines and so it is desirable to monitor the structural integrity of these coated pipes using techniques similar to those used on uncoated p
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Rate of shear of an ultrasonic oscillating rod viscosity probe.

Rabani A1, Pinfield VJ2, Challis RE3.
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Ultrasonic oscillating rod probes have recently been used by researchers to measure viscosity and/or density in fluids. However, in order to use such probes to characterise the rheological properties of fluids, it is necessary to define the shear rate produced by the probe. This paper proposes an an
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