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Smart Structures and Systems
  Volume 15, Number 1, January 2015, pages 41-55

Laser based impedance measurement for pipe corrosion and bolt-loosening detection
Jinyeol Yang, Peipei Liu, Suyoung Yang, Hyeonseok Lee and Hoon Sohn

    This study proposes a laser based impedance measurement system and impedance based pipe corrosion and bolt-loosening monitoring techniques under temperature variations. For impedance measurement, the laser based impedance measurement system is optimized and adopted in this paper. First, a modulated laser beam is radiated to a photodiode, converting the laser beam into an electric signal. Then, the electric signal is applied to a MFC transducer attached on a target structure for ultrasonic excitation. The corresponding impedance signals are measured, re-converted into a laser beam, and radiated back to the other photodiode located in a data interrogator. The transmitted impedance signals are treated with an outlier analysis using generalized extreme value (GEV) statistics to reliably signal off structural damage. Validation of the proposed technique is carried out to detect corrosion and bolt-loosening in lab-scale carbon steel elbow pipes under varying temperatures. It has been demonstrated that the proposed technique has a potential to be used for structural health monitoring (SHM) of pipe structures.
Key Words
    structural health monitoring; impedance; laser; wireless data transmission; outlier analysis; macro-fiber composite; temperature compensation; carbon steel elbow pipe; corrosion; bolt-loosening
Jinyeol Yang, Peipei Liu, Suyoung Yang, Hyeonseok Lee and Hoon Sohn: Department of Civil Engineering, Korea Advanced Institute for Science and Technology, 291 Daehak-ro, Yuseong-gu, Daejeon 305-701, Republic of Korea

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