Geir Sagvolden

Ship hull structure monitoring using fibre optic sensors

We discuss the need for ship hull monitoring and the roles such a system may fill during the different stages of a ships lifetime. We have found that fibre optic sensors are well suited for this application and present the fibre Bragg grating technology that has been employed in the composite hull embedded sensor system project (CHESS). Signal processing is the key to real-time structure monitoring, and we comment on the modular signal processing system that is being developed at FFI. Finally we present the CHESS installation on a new Norwegian naval vessel and show some results obtained with this system in systematic sea-keeping tests. The CHESS measurements on the new Norwegian fast patrol boat have been instrumental in the design verification of the vessel.

Wavelength multiplexed fibre Bragg grating system for high-strain health monitoring applications

We have developed and demonstrated a fibre Bragg grating strain gauge system for high strain applications using spatial and wavelength multiplexing. The system takes advantage of a priori knowledge about the strain levels and relative phases between the different sensor signals to accommodate many sensors per fibre in an application where we expect to measure several thousand microstrains. In combination with scanning Fabry-Perot filter interrogation, this principle has been utilized in the design of a system for health monitoring of a naval surface effect ship and the system has been used in long-term load monitoring on the vessel.

Instrumentation of a high-speed surface effect ship for structural response characterization during sea trials

We report on the instrumentation of a high-speed air-cushion catamaran (Surface Effect Ship) with more than 50 fiber optic Bragg grating strain gauges, as well as conventional resistive strain gauges, accelerometers, a Motion Reference Unit and Global Positioning System. A bow mounted wave radar was used to characterize the sea-state in order to estimate the wave loads on the hull. The relatively large number of strain gauges enabled us to determine the global deformation modes of the hull as well as local stress concentrations. This instrumentation was installed on a new Norwegian naval vessel and employed during sea-keeping tests in smooth and rough seas off the Norwegian coast. The measurements enable a detailed characterization of the vessels dynamic response to wave loading and comparison with Finite Element Analysis modeling of the ship. The experimental results provide invaluable information for the subsequent development of a system for health monitoring of the structure. We present the instrumentation layout and selected results.

Fiber optic system for ship hull monitoring

The authors describe a system which will, at about 10 installations in continuous operation after 2002, be the first fiber optic sensor system for ship hull monitoring with a wide user base. The experiences made with these systems in the coming years will provide valuable information on the design, reliability and possible use of such systems, and provide a basis for further development.