A 152.4 mm (6 in) diameter resonant column device was modified to enable the direct measurement of torsional acceleration transfer functions of samples subjected to random excitation in the small-strain regime. Samples were tested over a wide range of confining pressures. By measuring the rotational acceleration of the end platens, the need to estimate the applied torque using a torque-current calibration factor for data reduction was eliminated, and issues such as back-emf, base fixity and eddy currents were bypassed. Preliminary calibration results illustrate that the first four peak frequencies and amplitudes can be readily employed for a calibration of modulus and damping characteristics over a wide frequency band, utilizing the continuous nature of the system rather than only the fundamental frequency of the specimen configuration.
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