TORSION

in mechanics, the of strain in an elastic material jected to a simple twist. The condition 4s most clearly realized in the case straight cylindrical rod which has twisted about its axis. In such a the strain is one of pure distortion, does not involve change of The ratio of the supporting stre the strain is called the rigidity of material. The moment of force to sustain the condition of twist given rod is called a ‘torque’; and the twist is unity, the torque is measure of the torsional rigidity of particular specimen. It ‘can be shown that the torsional rigidity cylindrical wire or bar of a given jal increases as the fourth power diameter. When a coiled spring drawn out, the wire becomes twisted; and when it is pushed becomes le twisted. It is this change twist, calling into play the rigidity of the wire, which constitutes the resistance of the spring to of form.