Chapter 12 - Wave Propagation SHM with PWAS Transducers

Abstract

This chapter deals with the use of PWAS transducers to detect structural damage using wave propagation techniques. This application of PWAS technology builds on the wealth of knowledge accumulated in the conventional nondestructive inspection (NDI), nondestructive testing (NDT), and nondestructive evaluation (NDE) fields. The main difference between the PWAS approach and the conventional NDE approach is that the PWAS approach uses permanently attached unobtrusive, minimally intrusive PWAS transducers, whereas the conventional NDE approach uses relatively large and expensive conventional ultrasonic transducers. For this reason, the PWAS approach leads to embedded ultrasonic NDE which will facilitate on-demand interrogation of the structure to determine its current state of health and predict the remaining life. The chapter reviews the guided-wave NDE results and then presents 1-D and 2-D modeling and experiments of embedded NDE using PWAS transducers which are used as both transmitters and receivers of ultrasonic guided waves. Pitch-catch, pulse-echo, acoustic emission, and impact detection techniques are presented. Subsequently, the chapter presents some practical applications of PWAS wave propagation SHM for damage detection in various structures. The time-reversal approach to damage detection is also presented both theoretically and experimentally.