10 April 2014 Piezo-optical measurements for guided wave and acoustic emission structural health monitoring
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This paper presents the application and validation of optical equipment suitable for high frequency guided wave and acoustic emission detection with fiber Bragg grating (FBG) sensors. Guided wave and acoustic emission (AE) measurements were compared between piezoelectric wafer active sensors (PWAS) and fiber Bragg grating (FBG) sensors embedded onto isotropic plates and beams with an emphasis on testing FBG ultrasonic wave propagation frequency characteristics. The use of an acousto-ultrasonic FBG ring sensor to eliminate FBG directional dependence is also discussed. Since FBG sensors only detect strain longitudinal to the fiber, unlike PWAS they cannot serve as omnidirectional guided wave and AE sensors. To overcome this limitation, the use of an acousto-ultrasonic ring sensor, designed to augment and enhance the performance of FBG sensors, is tested. The ring sensor uses mechanical amplification principles to force in-plane vibration of the ring to occur at a specific resonance frequency. In this study, a ring sensor is bonded onto an isotropic plate; incoming guided wave and AE measurements from an FBG bonded to the ring sensor were compared to measurements from an FBG bonded to the plate. Preliminary results show the use of the ring sensor nearly eliminated the directional dependence of the FBG; concurrently the FBG on the ring sensor sensed incoming guided waves and AE events near its resonance frequency and rejected phenomenon occurring at other frequencies.
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Erik Frankforter, Erik Frankforter, Bin Lin, Bin Lin, Victor Giurgiutiu, Victor Giurgiutiu, } "Piezo-optical measurements for guided wave and acoustic emission structural health monitoring", Proc. SPIE 9062, Smart Sensor Phenomena, Technology, Networks, and Systems Integration 2014, 906207 (10 April 2014); doi: 10.1117/12.2047483; https://doi.org/10.1117/12.2047483

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