Acoustic Emission

Abstract

Acoustic emission (AE) is one of the most promising methods for structural health monitoring (SHM) of materials and structures. Because of its passive and non-invasive nature, it can be used during the operation of a structure and supply information that cannot be collected in real time through other techniques. It is based on the recording and study of the elastic waves that are excited by irreversible processes, such as crack nucleation and propagation. These signals are sensed by transducers and are transformed into electric waveforms that offer information on the location and the type of the source. This chapter intends to present the basic principles, the equipment, and the recent trends and applications in aeronautics, highlighting the role of AE in modern non-destructive testing and SHM. The literature in the field is vast; therefore, although the included references provide an idea of the basics and the contemporary interest and level of research and practice, they are just a fraction of the total possible list of worthy studies published in the recent years.

A Review on Acoustic Emission Testing for Structural Health Monitoring of Polymer-Based Composites

“…Each type of failure has unique characteristics such as frequency, amplitude, rise time, and duration due to the distinct process that occurs at failure. That includes the crack tip’s motion, the crack surface area generated, and the crack propagation speed [ 17 ], as will be explained later.…”

“…Hence, upon unloading (end of LC4) and loading (LC5), the emission is exerted at a load lower than the maximum load exerted from previous cycles; the effect is known as the Felicity ratio (Equation (5)). The emission arising at previously reached loads is due to the cracks and their corresponding stress concentration areas that exhibit a local increase in stress with lower loads [ 17 ]. …”

“…Pulse generators have also been identified as a source of EMI. Although it is challenging to eliminate EMI, it is typically associated with waveforms distinguishable from actual AE sources [ 17 ].…”

“… ( a ) Illustration of the crack orientation difference ( b ) signals originating from different crack orientations, reproduced with permission from [ 17 ]. …”

Study of Fatigue Damage Detection by Current Information of Measurement System

“…( 23)). The probabilistic approach of construction of fatigue damage index is analysed in [37] and presented in the next section.…”