This work first considers a review of the dominant current methods for fibre Bragg grating wavelength interrogation. These methods include WDM interferometry, tunable filter (both Fabry-Perot and acousto-optic) demultiplexing, CCD/prism technique and a newer hybrid method utilizing Fabry-Perot and interferometric techniques. Two applications using these techniques are described: hull loads monitoring on an all-composite fast patrol boat and bolt pre-load loss monitoring in a composite beam in conjunction with a state-space modelling data analysis technique.
This work explores the role of empirical dynamical models in deducing the level of preload
loss in a bolted connection. Specifically, we examine the functional relationship
between data gleaned from locations on either side of the connection using nonlinear
predictive models. This relationship, as quantified by a measure of prediction
error, changes as a function of bolt loosening, thus allowing both the presence and
magnitude of the axial load to be identified. The models are based on a phase
space portrayal of the system dynamics and require only that the structure’s
response be low dimensional. The technique is demonstrated experimentally on a
composite beam fastened to steel plates with four instrumented bolts. Results are
compared to a similar approach using an auto-regressive (AR) modeling technique.
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