Lockheed Aircraft Corporation

William H Lewis, Jr

The strain energy that is released when a structural member fails is emitted, among other ways as a broad frequency acoustic emission which is detected by a piezoelectric crystal sized for a preselected natural frequency. This piezoelectric crystal converts the acoustic energy into an electronic signal which is filtered to permit passage of only predetermined frequencies. The filtered signals are then passed through a device which matches the line impedance. A differential amplifier provides signal amplification, and rejects noise, in the received signals which are then passed through a level detector, preset to only allow passage of predetermined signals which in turn trigger a latch for a light emitting diode indicating that a structural failure has occurred. A built-in tester allows for a periodic check to be made to insure system operation. An amplified signal is oscillated causing the piezoelectric crystals to respond as if they detected an acoustic response from a structural failure which triggers the light emitting diode if the system is functioning properly.

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Atlanta, GA, United States of America

William H Lewis, Jr