In order to study the response of materials under a torsional force, the torsion test is
performed by mounting the specimen onto a torsion testing machine as shown in figures 2-4, and then
applying the twisting moment till failure. The torque and degree of rotation are measured and plotted
as shown in figure 5. It can be seen that higher torsional force is required at the higher degrees of
rotation. Normally, the test specimens used are of a cylindrical rod type since the stress distribution
across the section of the rod is the simplest geometry, which is easy for the calculation of the stresses.
Both ends of the cylindrical specimen are tightened to hexagonal sockets in which one is fitted to a
torque shaft and another is fitted to an input shaft. The twisting moment is applied by turning the
input handwheel as illustrated in figure 3 to produce torque until the specimen fails.