Smart marine structures: an approach to the monitoring of ship structures with fiber-optic sensors

Abstract

Prevention of serious damage of marine structures might be achieved by monitoring the loading conditions and by inspecting the structural integrity. The concept of smart structures with a fiber-optic sensor network can be applied to marine applications. There are plenty of marine structures in huge dimensions, for example, the overall length of a very large crude carrier exceeds 200 m.A fiber-optic laser-Doppler velocimeter was developed as a displacement sensor with long gage length. The optical fiber sensor has potential advantages as a structure monitoring sensor: (i) unlimited gage length, (ii) applicability to dynamic measurement and (iii) less affected by temperature. Free vibration behavior of the coupon specimen could be monitored with excellent dynamic resolution. Flexural deformation of the specimen under cyclic bending load was also monitored, and linearity and sensitivity of the developed sensor system was confirmed.An optical time-domain reflectometer (OTDR) was applied to the damage detection of composite materials in which optical fibers were embedded. Onset and location of fiber breaks could be detected by using the OTDR technique, which was applied to tensile tests of resin, and tensile and flexure tests of cross-plied GFRP. The failure strain of the optical fiber had rather wide scatter when it was embedded in the composite, and the average values also depended on the condition of embedment. Location of the failure points could be measured with sufficient accuracy.

Enhanced optical coherence vibration tomography for subnanoscale-displacement-resolution calibration of piezoelectric actuators

“…The SOCVT measures the absolute displacement of PZT surface without the requirement for both phase shift modulation and the integration of velocity along the time axis, which are required for a laser Doppler vibrometer to obtain displacement information [22]. The displacement resolution of the system remains in ultrafine condition for both nanoscale and microscale displacement measurements.…”

The plastic optical fiber cantilever beam as a force sensor

“…The proper designing can replace stain gauge load cell to certain extent in some applications. [1][2][3][4][5][6][7][8][9][10][11][12]. These internal WLAN antennas include the slot antenna [2], the traditional metal-plate or printed PIFA (planar inverted-F antenna) with a direct feed [3][4][5][6], the monopole antenna [7][8][9][10][11], the coupled-fed PIFA [12], and so on.…”

“…Such structures are capable of providing vital information concerning the integrity of engineering structures through the use of embedded or surface bond sensors. Amongst the various methods available, optical fiber sensing systems have attracted considerable attention [1][2][3].…”

Two-dimensional optical coherence tomography for real-time structural dynamical characterization

“…The detection range can be extended beyond the half-wavelength limit by using phase shift modulation (or phase unwrapping) techniques, at the cost of increased instrument complexity and decreased measurement accuracy (related to the inherent phase shift error) [14]. On the other hand, laser Doppler vibrometer directly measures the velocity of a sample although the displacement information is an analog integration of the velocity signal along the time axis [22,23]. However, such analog integrators always require a high pass filtering of the velocity signal.…”