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.