ASA 130th Meeting - St. Louis, MO - 1995 Nov 27 .. Dec 01

3aEA5. Acoustic material characterization by laser interferometry.

R. Lance Willis

T. Shane Stone

Yves H. Berthelot

School of Mech. Eng., Georgia Inst. of Technol., Atlanta, GA 30332-0405

An interferometric system consisting of five independent probes cabable of measuring in-plane or out-of-plane surface motion of a vibrating sample at five different points simultaneously has been designed, constructed, and tested. A description of the design, measurement capabilities, and performance specifications will be given. The system utilizes optical fibers and compact probe design(30mmx15mmx9mm) to enable close spacing measurement points. Signal demodulation is performed by phase-locked loops allowing real-time measurements. The system is designed to test voided polymer samples excited by a shaker in the 100 Hz to 5 kHz range. It is calibrated for steady state and transient excitation of the sample. Results include measurements of the damping constant of the sample in the time domain for various frequencies of excitation. [Work supported by the Office of Naval Research, Code 334.]