When a torque is applied to the output shaft whilethe input shaft is fixed, torsion is generated according to the torque value. The torsion can be shown in the hysteresis curves. The value of b/a isreferred to as"torsional rigidity". The torsion angle at the mid points of the hysteresis curve width within ±3% of the rated torque is referred to as"lost motion". The torsion angle when the torque indicated by the hysteresis curve is equal to zero is referred to as"backlash”.