A Forced Vibration Method for the Measurement of Dynamic-Mechanical Properties of Materials.

Signals generated by a digital transfer-function analyser drive torque motors which impart sinusoidally varying stress to flexural and torsional test systems. The resulting deformation is measured by angular transducers, and is displayed by the function-analyser as displacement amplitude and phase shift with respect to the applied stress signal. The system is analyzed and a method for calculating the complex modulus and loss tangent of the speciment is developed. Typical results for polycarbonate and glass-reinforced polycarbonate are discussed, and some advantages of the method are indicated. Author