Fundamental Study on Development of Smart Marine Structures

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A fundamental study was performed aiming at the realization of a smart marine strucure, in which smart functions such as self-diagnosis or self-repairing are incorporated in structural material itself, in view of enhancing the structural reliability of ocean equipments and structures under severe environmantal conditions.1) The methodology and the construction of sensors for damage detection were examined. Tensile test od singl optical fiber embedded in a resin, tensile and flexure tests of GFRP specimans were carried out, and it was shown that the damage of mebedded optical fibers were detected by OTDR (Optical Time Domain Reflectometer) and the applicability of optical fiber was confirmed as a distributed detector of critical strain. Fiber-optic velocity sensor was developed based on Laser-Doppler effect and deformation of tensile specimen under cyclic load, vibration of cantilever beam specimen were measured with the developed sensor in comparison with strain gages. The applicabilit … More y of fiber-optic strain sensors to marine structures was also discussed.2) The possibility of active vibration control of flexible structure by applying piezoelectric actuators was examined. A cantiever beam specimen was manufactured and tested, in which a Bimorf piezoelectric element was incorporated as an actuator inducing flexural deformation as well as laser deflectometer and strain gages as sensors. A system identification of this active/adaptive atructure was carried out and thr active vibration control performance was evaluated.3) Piezoelectric polymer films (polyvinylidene fluoride : PVDF) and the developed fiber-optic Laser Doppler Vibrometer (LDV) were applied to the vibration control of a flexible composite beam. Theoretical consideration confimed that the control system is always stable. In the experimental study, an analog control circuit was developed and applied to velocity feedback control of multi-modes vibration. The effectiveness of the control system was evaluated by simulation and experiments. Less