Figure 1. Location of the two specimens (A) and block diagram (B) of the dynamic viscoelastometer with a schematic representation of the relationship between stress and strain of a viscoelastic material during a sinusoidal oscillating strain (, angular velocity). The sinusoidal strain is produced by a tension control motor in the driver, and the stress and strain are measured by means of load and displacement detectors and transmitted to a data processor. In a viscoelastic material, the phase difference between stress and strain is somewhere in between (0 < < /2), and the complex modulus G* is resolved into two components: the storage modulus G' and the loss modulus G'', shown vectorially. The tangent of the phase angle () between stress and strain is a measure of the ratio of energy loss to energy stored during cyclic deformation.