What is torsional strength?

Hint: Torsion is defined as the twisting of an object due to torque applied to it. We should be clear with the concept of torsion for defining its strength. Torsional strength is different from that of torque. Torque is the force that is capable of producing an acceleration whereas torsion describes the twist formed in a body due to torque.

Complete answer:
As we know, the twisting or wrenching of a body by the exertion of forces tending to turn one end or part about a longitudinal axis while the other is held fast or turned in the opposite direction is known as torsion.
Let us see what torsional strength is. The measure of the ability or amount of twisting or rotating force of a material to withstand the effect of the twisting force. It is the ultimate strength of a material subjected to torsional force and is the maximum torsional stress that a material sustains before rupture. It is the torsional stress that a body can withstand before its failure.
The torsional strength is defined as
$Torsional\;strength= \dfrac{rotational\;force}{cross-sectional\;area}$

Additional Information: Torsional shear can be considered as a shear that is formed by the torsion exerted. Torsion takes place when two equal forces of similar values are applied in two different directions, this causes torque. Torsional shear tends to cause deformation of a material.

Note: Torsion can be expressed in either pascals (Pa) or an S.I. unit Newtons per square meter, or pound per square inch whereas torque is expressed in newtons-meters. It should be noted that the words torsion and torque cannot be used interchangeably and these are two different physical quantities.