Torsion

Torsion, twisting strain produced when a torque is applied to an object. For example, torsion is the strain experienced by a length of wire when a twisting force is applied to one end while the other end is fixed. Torsion can be measured by observing how much an object twists due to a given torque. For example, when a cylindrical object one unit long is twisted at one end, and the other end is held fixed, the amount the ends of the cylinder rotate relative to each other is a measure of the torsion. Engineering materials employed in rotating machine parts, such as engine crankshafts and ship-propeller shafts, must resist the torsional stresses induced by the twisting loads. See also Torsion Balance.