Procedure

1. Measure the overall length and the diameter of the test specimen at about three locations, and calculate the average diameter.
2. Draw a longitudinal line along the test section of the specimen using chalk. This serves as a visual aid to observe the degree of twist during loading.
3. Select the appropriate driving dogs to suit the size of the specimen and clamp the specimen securely in the machine using the sliding spindle.
4. Select the appropriate torque range using the capacity change lever.
5. Set the maximum load pointer to zero.
6. Set the protector to zero for convenience and secure it using the knurled screw.
7. Apply the load by rotating the hand wheel in either direction.
8. Increase the load in suitable increments, noting the applied torque and the corresponding angle of twist.
9. Plot a graph between the applied torque and the corresponding angle of twist, and calculate the Modulus of Rigidity ($G$) using the following relation:

$$\frac{T}{J}=\frac{G\theta}{L}$$

where:

• $T$ = Applied torque
• $J$ = Polar moment of inertia of the shaft,

$$J=\frac{\pi d^4}{32}$$

• $G$ = Modulus of Rigidity (Shear Modulus) of the material
• $\theta$ = Relative angle of twist (radians)
• $L$ = Gauge length (the length of the shaft over which the angle of twist is measured)

Virtual Procedure

1. Start the experiment by clicking the Play button.
2. Observe the torque applied to the specimen by the rotating wheel.
3. As the simulation progresses, observe the corresponding values of torque and angle of twist.
4. Observe the graph plotted between the torque and angle of twist values.
5. Use the Pause, Play, and Restart controls to view the values of different parameters at various stages of the simulation.

Note: The graph provides various interactive features such as zooming and panning. Hover the mouse pointer over the icons above the graph to view the function of each feature.