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UBC Theses and Dissertations

Wave propagation in elastic bars coupled by viscoelstic element Kapoor, Arun Kumar


The split Hopkinson pressure bar has been used to study the acoustic isolation that can be achieved by inserting a compliant element into the sound path in an elastic system, and to study the dynamic response of the material comprising the compliant element. The specimens were inserted between two steel transducer bars. The incident stress pulse, of about 100 microsecond duration, was produced by striking the free end of one of the transducer bars by a round-headed striker bar. The incident pulse in the first bar and the transmitted pulse in the second bar were sensed by strain gages and displayed on an oscilloscope. The comparison of computed Fourier transforms (within the acoustic frequency range) of both the incident and transmitted pulses showed that in general a greater reduction in transmission of vibration across a specimen is achieved: i) by increasing the length of the specimen; ii) by using a material with a higher attenuation constant or higher viscous damping; iii) by increasing the impedance mismatch between the specimen and the steel transducer bars. Also, it was found that isolation is greater at high frequencies than at low frequencies.

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