Fig. 2.3.

Rheometer schematic for small amplitude oscillatory shear. A motor oscillates a rotating shaft and plate at varying frequencies at a fixed strain amplitude. An idealized velocity profile within the sample is shown. In response to the applied strain, the material will exert a torque on the rheometer. If the sample is viscoelastic, the torque will be dependent on the applied frequency, as will the phase angle between the torque and the strain. The torque and phase angle are the only measurements needed to calculate the storage and loss modulus of the sample