Structural Health Monitoring of Large Structures Using Acoustic Emission-Case Histories

Acoustic emission (AE) techniques have successfully been used for assuring the structural integrity of large rocket motorcases since 1963 [...

A General Bayesian Framework for Ellipse-based and Hyperbola-based Damage Localisation in Anisotropic Composite Plates

This paper focuses on Bayesian Lamb wave-based damage localization in structural health monitoring of anisotropic composite materials. A Bayesian framework is applied to take account for uncertainties from experimental time-of-flight measurements and angular dependent group velocity within the composite material. An original parametric analytical expression of the direction dependence of group velocity is proposed and validated numerically and experimentally for anisotropic composite and sandwich plates. This expression is incorporated into time-of-arrival (ToA: ellipse-based) and time-difference-of-arrival (TDoA: hyperbola-based) Bayesian damage localization algorithms. This way, the damage location as well as the group velocity profile are estimated jointly and a priori information taken into consideration. The proposed algorithm is general as it allows to take into account for uncertainties within a Bayesian framework, and to model effects of anisotropy on group velocity. Numerical and experimental results obtained with different damage sizes or locations and for different degrees of anisotropy validate the ability of the proposed algorithm to estimate both the damage location and the group velocity profile as well as the associated confidence intervals. Results highlight the need to consider for anisotropy in order to increase localization accuracy, and to use Bayesian analysis to quantify uncertainties in damage localization.Projet CORALI

Impact detection in anisotropic materials using a time reversal approach

This article presents an in situ imaging method able to detect in real-time the impact source location in reverberant complex composite structures using only one passive sensor. This technique is based on the time reversal acoustic method applied to a number of waveforms stored in a database containing the impulse response (Green's function) of the structure. The proposed method allows achieving the optimal focalization of the acoustic emission source in the time and spatial domain as it overcomes the drawbacks of other ultrasonic techniques. This is mainly due to the dispersive nature of guided Lamb waves as well as the presence of multiple scattering and mode conversion that can degrade the quality of the focusing, causing poor localization. Conversely, using the benefits of a diffuse wave field, the imaging of the source location can be obtained through a virtual time reversal procedure, which does not require any iterative algorithms and a priori knowledge of the mechanical properties and the anisotropic group speed. The efficiency of this method is experimentally demonstrated on a stiffened composite panel. The results showed that the impact source location can be retrieved with a high level of accuracy in any position of the structure (maximum error was less than 3%)

Near-field beamforming performance analysis for acoustic emission source localization

This paper attempts to study the localization performance of a near-field acoustic emission (AE) beamforming by varying parameters such as array types, localization velocity, the maximum diameter of the array and the sensor spacing. To investigate how those parameters affect localization performance, an improved finite element method is established to obtain AE signals which take real propagation characteristics and have high signal to noise ratio. And AE signals of the finite element simulation under different parameters are obtained based on the presented method. Then AE beamforming is used to localize AE sources, and the influences of these parameters on the AE beamforming localization performing are analyzed. The results indicate that the parameters have impact on the localization accuracy clearly. This work can provide a reference for the selection of parameters when the beamforming is used to localize AE sources