Multi-site damage localization in anisotropic plate-like structures using an active guided wave structural health monitoring system

Abstract

A new approach for structural health monitoring using guided waves in plate-like structures has been developed. In contrast to previous approaches, which mainly focused on isotropic or quasi-isotropic plates, the proposed algorithm does not assume any simplifications regarding anisotropic wave propagation. Thus, it can be used to improve the probability of detection.In this paper the mathematical background for damage localization in anisotropic plates will be introduced. This is an extension of the widely known ellipse method. The formalism is based on a distributed sensor network, where each piezoelectric sensor acts in turn as an actuator. The automatic extraction of the onset time of the first waveform in the differential signal in combination with a statistical post-processing via a two-dimensional probability density function and the application of the expectation-maximization algorithm allows a completely automatic localization procedure. Thus, multiple damages can be identified at the same time.The present study uses ultrasonic signals provided by the spectral element method. This simulation approach shows good agreement with experimental measurements. A local linear neural network is used to model the nonlinear dispersion curves. The benefit of using a neural network approach is to increase the angular resolution that results from the sparse sensor network. Furthermore, it can be used to shorten the computational time for the damage localization procedure.

A data-driven temperature compensation approach for Structural Health Monitoring using Lamb waves

“…Considering the widely used pitch-catch technique, one of the transducers is used as an actuator to excite the structure and the others are used as sensors to measure Lamb wave signals. The damage detection is performed by subtracting the signals captured from the structure in a healthy state (without damage) from those captured in a current unknown state (Ihn and Chang, 2008;Lu et al, 2006;Michaels, 2008;Moll et al, 2010). The difference of signals is used to locate and size the damage in the structure.…”

Multidimensional guided wave dispersion recovery for locating defects in composite materials

“…A single ultrasonic excitation creates multiple wave excitations (i.e., modes) with distinct, frequency-dependent (i.e., dispersive) velocities [30,31,32]. As a result, many guided wave methods for locating defects in large regions of a structure [33,34,35,36,37] rely on precise knowledge of these complex velocity characteristics [38,37,39,40] or employ approximations of guided wave behavior [33,34] at the cost of accuracy or robustness. For example, the wave envelope (without phase information) is often assumed to have a constant, non-dispersive velocity throughout the structure.…”

Evaluation of effective elastic properties of layered composite fiber-reinforced plastic plates by piezoelectrically induced guided waves and laser Doppler vibrometry

“…As an indispensable part, elastic guided wave (GW) based NDT and SHM inspection of composites assumes mathematical and computer modeling of wave processes in investigated structures. The simulation is necessary to predict wave velocities and radiation diagrams [1,2], to locate defects on the basis of signals' time of flight (ToF) [3] or hybrid time-reversal technique [4], to tune optimal frequencies and allocation of piezoelectric active sensors [5], among many other applications. Adequate modeling of these phenomena requires a prior knowledge of effective elastic material constants.…”