Abstract
The capabilities of ceramic PZT transducers, allowing for elastic wave excitation in a broad frequency spectrum, made them particularly suitable for the Structural Health Monitoring field. In this paper, the approach to detecting impact damage in composite structures based on harmonic excitation of PZT sensor in the so-called pitch–catch PZT network setup is studied. In particular, the repeatability of damage indication for similar configuration of two independent PZT networks is analyzed, and the possibility of damage indication for different localization of sensing paths between pairs of PZT sensors with respect to damage locations is investigated. The approach allowed for differentiation between paths sensitive to the transmission mode of elastic wave interaction and sensitive reflection mode. In addition, a new universal Bayesian approach to SHM data classification is provided in the paper. The defined Bayesian classifier is based on asymptotic properties of Maximum Likelihood estimators and Principal Component Analysis for orthogonal data transformation. Properties of the defined algorithm are compared to the standard nearest-neighbor classifier based on the acquired experimental data. It was shown in the paper that the proposed approach is characterized by lower false-positive indications in comparison with the nearest-neighbor algorithm.
Highlights
In the case of one single Damage Index DI and normal family of probability densities chosen for its distribution as in example given by Equation (7), Maximum Likelihood (ML) estimators of the mean and the variance obtained for a training set T j = { DI1, . . . , DINj } are [69]: μ =
Single layered PZT transducers produced by STEMINC
An approach to Structural Health Monitoring (SHM) based on sinusoidal excitation of PZT transducers and voltage transfer ratio-based Damage Indices has been proposed
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. It is applied to BVID damage detection of composites structures caused by low-energy impacts Another novelty of this work lies in the definition of a new Bayesian approach to SHM data classification. The amplitude of the received signal depends on wave reflection coefficient on damage for a given excitation frequency [55], the distance of damage from the PZT sensor as well as attenuation properties of the monitored structure. This may, in some cases, restrict the range of sensor efficiency, in particular when excitation voltage applied to PZT transducer is relatively small [11]. This property was demonstrated for particular type of damage in [52] and will be discussed in this paper
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