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The torsional resonatorIn this experiment the tissue sample is made a part of a vibrating system. This procedure is based on the same working principle of the viscometer. The experimental set-up consists of a rod of circular cross-section excited at its torsional eigenfrequencies (from 1 to 10 kHz) by an electromagnetic transducer (which represents the actuator as well as the sensor). Only the free end of the rod is laid against the soft tissue. A detailed description of this system is given in [1t].
The damping characteristics of the vibrating system and the resonance frequency are inferred from the control variables of a phase stabilization loop. Due to the contact with the soft tissue, changes occur in the dynamic properties of the torsional oscillator: the Q-Factor is reduced and the resonance frequency is shifted. Based on an analytical model ([1t], [10p], [6p]) the mechanical impedance of the material in contact is determined from these data. The dependency of the complex shear modulus on contact force, vibration amplitude, frequency, and number of loading cycles can be studied with this experiment.
This procedure was applied for biological tissues and for technical materials [6p], [outside link]. [Top] | |||||||||||||||||||||||||
