Abstract
The need for effective and reliable damage detection and localization systems is growing in several engineering fields, in particular in water impact problems characterized by impulsive loading conditions, high amplitude vibrations and large local deformations. In this paper, we further develop the approach presented in previous works to detect damage of water-impacting structures. Specifically, we provide a set of experimental tests on a flexible plastic cylinder impacting the water after a 50 cm free fall. The cylindrical specimen is artificially damaged in a known position. Strain measurements are performed through a set of nine fiber Bragg gratings distributed along the circumference of a cylinder section. We show that strain sensors can be used as reference sensors, for structure displacements reconstruction, and control sensors, for damage detection purposes, and the computation of the difference between measured and expected deformation may allow damage detection. Moreover, we investigate how exchanging control and reference sensors in the same sensor arrangement affect damage detection and localization.
Highlights
Fluid structure interaction (FSI) in free surface fluids is an important field of study in naval, civil and mechanical engineering and a large scientific literature is available on this topic [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18]
The proposed reconstruction method, which represents an enhancement of previous works on local strain measurements, has been tested to evaluate both its effectiveness in strain and displacement fields reconstruction and its suitability for damage detection and localization
This application is based on the local strain data from fiber Bragg grating (FBG) sensors, which can be used for reconstruction purposes or damage detection
Summary
Fluid structure interaction (FSI) in free surface fluids is an important field of study in naval, civil and mechanical engineering and a large scientific literature is available on this topic [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18]. One relevant problem in this field is represented by so-called hull slamming, occurring when solid bodies impact the free surface of a fluid, usually water: large forces emerge for short time durations inducing vibrations and, possibly, structural damage, from local buckling and deformations to structural breaks [1,2,3]. The development of monitoring systems able to measure impulsive forces or consequent damages is of paramount importance for many engineering structures (e.g., ships, vessel, hydraulic structures) and still far from being industrialized [19]. Several numerical and experimental studies have been carried out in this field, the evolution of such impulsive loading is not completely understood and the monitoring of the possible damage is a complex task, largely unexplored, so far. The results obtained demonstrate the potential of the methodology for identifying local damages, including those related to localized, repeated slamming events, such as in the bow bulb, or structural failures that may happen during a cruise (e.g., due to collisions and/or cargo misplacement in the presence of bad weather/sea conditions) and may become worse because of hull slamming
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