On the Prediction of Guided Wave Dispersion Curves in Plates for Health Monitoring Applications

Abstract

In the last years, a significant interest has been pointed out in the capability of ultrasonic guided waves as candidate tool for structural health monitoring (SHM), due to their high damage detection sensitivity and low power consumption. The monitoring of the structural health through the propagation of guided waves is complex: some wave phenomena, namely dispersion and slowness, together with boundary scattered waves, may mask the presence of damages. So, studying the dispersion phenomenon through the dispersion curves may be helpful in understanding the propagation mechanisms. As Lamb waves dispersion equations do not generally have analytical solutions, the development of a predictive finite element (FE) model can be a valuable tool for the improvement of SHM systems, avoiding the high cost of experimental campaigns. Thus, once calibrated with respect to an experimental test case, the developed FE model can be used to simulate and predict guided-wave propagation mechanisms in a given structure. This leads to the possibility of employing such approach to identify and localize potential structural damages, that is the final aim of an SHM system. In this work, the FE method, together with an in-house code, has been used to investigate guided wave dispersion phenomenon in plates for possible SHM applications.

Numerical Investigation on Guided Waves Dispersion and Scattering Phenomena in Stiffened Panels

“…Concerning the mode group velocities, they appear to be less sensitive to the laminae orientation. All these results can be considered accurate since they are in line with those available in literature [ 30 , 31 ] and presented by authors in reference [ 16 ]. Specifically, the modelling technique used herein to simulate GW propagation in aluminum and composite structures has been widely assessed by authors in previous research activities against analytical and experimental data [ 18 , 29 ].…”

“…However, to concentrate most of the wave energy on a specific central frequency, recorded data have been reconstructed by means of a n-cycles sinusoidal tone burst Hanning windowed signal, with a step of . Once the distance between actuator-receivers and the ToF on all paths are known, it is possible to calculate the group velocity ( ) of Lamb waves packets [ 16 ]. Considering that for an isotropic material does not depend on propagation direction, to compute the group velocity only the actuator 1–receiver 3 (R1–R3) path has been considered, whilst for the composite plate all paths have been investigated to highlight both the dispersion and slowness (dependence of the waves velocity on the direction of propagation) phenomena.…”

“…The latter allows determining the time of flight (ToF) of the incident and modes (simultaneously activated), and of the converted modes, as widely explained in Section 4 . Thus, once the distances between actuator/receivers and the ToF of the modes are known, it is possible to calculate the GW group velocities [ 16 ] and plot the dispersion curves.…”

“…Dispersion equations solution can be achieved through several techniques [ 13 , 14 , 15 ]. Among all, a cost-effective approach is represented by the finite element (FE) method, which can significantly contribute to the prediction and the understanding of GW propagation mechanisms thanks to its ability to handle complex geometries and composite layups [ 16 , 17 , 18 , 19 ] while also considering environmental and operational conditions.…”

Damage Detection in Flat Panels by Guided Waves Based Artificial Neural Network Trained through Finite Element Method

“…Once the distances between actuator/receivers and the ToF on all paths are known, it is possible to calculate the velocity of Lamb waves packet (c g ) [35]. Considering that for an isotropic material, c g does not depend on propagation's direction, to compute the group velocity, only the path actuator 1-receiver 2 was considered.…”