title: Simple apparatus for measuring the dynamic shear modulus of cylindrical specimens.
abstract: An apparatus is decribed which has been used to determine the shear modulus of cylindrical specimens vibrating in the torsional mode. The specimens are maintained in self-excited vibration by an eddy-current driver, an eddy-current pickup, and a feed back circuit consisting of a phase-locked-loop and an amplitude control module. The system has a frequency stability of 1 part in 10(6) for high-Q materials (a few thousand) in the audio range. In addition, it can automatically track frequency changes of a few percent with negligible error in phase or frequency.
authors.affiliation: Department of Physics, Wright State University, Dayton, Ohio 45435Department of Geology, Wright State University, Dayton, Ohio 45435.
authors.forename: H M
authors.initials: HM
authors.lastname: Simpson
authors.forename: J
authors.initials: J
authors.lastname: Pearson