Abstract
The structural health monitoring (SHM) of critical structures is a complex task that involves the use of different sensors that are also aimed at the identification of the location of the impact point using ultrasonic sensors. For the evaluation of the impact position, reference is often made to the well-known triangulation method. This method requires the estimation of the differential time of arrival (DToA) and the group velocity of the Lamb waves propagating into a plate-like structure: the uncertainty of these two parameters is taken into consideration as main cause of localization error. The work proposes a simple laboratory procedure based on a set-up with a pair of sensors that are symmetrically placed with respect to the impact point, to estimate the uncertainty of the DToA and the propagation velocity estimates. According to a theoretical analysis of the error for the impact position, the experimental uncertainties of DToA and the propagation velocity are used to estimate the overall limit of the SHM system for the impact positioning. Because the error for the DToA estimate depends also on the adopted signal processing, three common methods are selected and compared: the threshold, the correlation method, and a likelihood algorithm. Finally, the analysis of the positioning error using multisensory configuration is reported as useful for the design of the SHM system.
Highlights
The possibility for identifying damage on a structure by sensory systems allows for the determination of its integrity, reducing downtime and maintenance costs
We have investigated the limits of accuracy on the detection of the position of impacts with the use of an aluminum plate, using the method of triangulation with Lamb waves, and we analyzed the results obtained with impacts performed along the axes of symmetry and on asymmetric positions with respect to a pair of piezoelectric sensors
In order to implement the triangulation method, we evaluated the differential time of arrival (DToA) with three methods, and estimated the propagation velocity of the Lamb waves propagating in the plate-like structure
Summary
The possibility for identifying damage on a structure by sensory systems allows for the determination of its integrity, reducing downtime and maintenance costs. Monitoring (SHM) is important because it permits real-time detection of the condition of a structure, of safety-critical components typical of the application of compounds in the space, automotive, and aeronautics sectors [1,2,3,4,5,6,7]. These design goals are envisaged in multisensory—connected items by the new paradigms introduced by Industry 4.0 [8]. The ability of a monitoring system to locate the position of the emission source allows it to actively focus the search for damage on a restricted area
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