Acoustic source localization in anisotropic plates without knowing their material properties: an experimental investigation

Abstract

An integral aspect of modern infrastructural engineering is to constantly monitor the health of a structure either actively or passively in order to ensure its safe performance throughout the design life. For passive structural health monitoring, it is important to estimate the location of an acoustic source that may be caused by events such as impact of a foreign object with the structure, failure of a structural element, formation of cracks, etc. Such an acoustic source generates acoustic waves that propagate through the medium. These waves can be captured by ultrasonic sensors mounted on the structure at some pre-selected locations and, subsequently, analyzed to predict the location of the acoustic source. Over the years, several researchers have proposed techniques for acoustic source localization in both isotropic and anisotropic structures. While acoustic source localization in isotropic structures is relatively simple, introduction of anisotropy adds a layer of difficulty to the problem due to the fact that waves do not propagate with the same speed in all directions. This study presents acoustic source localization techniques for anisotropic plates based on the analysis of the wave front shapes typically observed in anisotropic plates and presents experimental verification of the techniques. Three different geometric shapes are considered as the assumed wave front shapes: a rhombus, an ellipse and a parametric curve. A slightly modified version of the rhombus-based technique from the original approach is proposed. The experimental study is performed on two plates with different degrees of anisotropy.

State-of-the-Art Review on the Acoustic Emission Source Localization Techniques

“…Experiments were performed on a carbon-epoxy plate, having an acoustic source. Sen et al [111] slightly modified the rhombus-based technique, taking three distinct wavefront shapes: a rhombus, an ellipse, and a parametric curve. They stopped believing that the wave propagates in a straight path.…”

A fast approach for acoustic source localization on a thin spherical shell

“…Then, Yin et al 27 modified this concept using ''Z''-shaped sensor clusters for increasing the prediction accuracy. Another ASL technique in highly anisotropic plates using ‘‘L’’-shaped sensor clusters was proposed by Park et al 28 and Sen et al 29,30 using wavefront shapes. Yin et al 31,32 extended applications of “L”-shaped sensor clusters to two- and three-dimensional heterogeneous structures.…”

Rapid localization of acoustic source using sensor clusters in 3D homogeneous and heterogeneous structures

“…This technique was then modified further by Yin et al 21 using ''Z'' shaped sensor clusters for improved reliability. Park et al 22 and Sen et al 23,24 used ''L'' shaped sensor clusters to develop another ASL technique by monitoring the propagating wave fronts in highly anisotropic plates. The experiment and the simulation in heterogeneous 2D structures show that the technique using ''L'' shaped sensor clusters can also locate the acoustic source in heterogeneous structures considering the wave refractions at the interfaces between different media.…”