Structural testing and assessment, process monitoring, and material characterization are three broad application areas of acoustic emission (AE) techniques. Quantitative and qualitative characteristics of AE waves have been studied widely in the literature. This book reviews major research developments in the application of AE in numerous engineering fields. It brings together important contributions from renowned international researchers to provide an excellent survey of new perspectives and paradigms of AE. In particular, this book presents applications of AE in cracking and damage assessment in metal beams, asphalt pavements, and composite materials as well as studying noise mitigation in wind turbines and cylindrical shells.

This book discusses the applications of fracture mechanics in the design and maintenance of asphalt concrete overlays. It provides useful information to help readers understand the effects of different material and loading type parameters on the fracture properties of asphalt concretes. It also reviews relevant numerical and experimental studies, and describes in detail design parameters such as aggregate type, air void, loading mode, and additives, based on the authors experience and that of other researchers.

This paper investigates the effect of loading level and loading rate on the damage development and strength of asphalt mixtures. Indirect tensile creep tests with different loading levels and strength tests with three loading rates were performed at three low temperatures for ten mixtures. An acoustic emission (AE) system with eight recording channels was used to monitor the development of micro cracking in the specimens for both tests for one mixture. The experimental results show that test temperature has a significant effect on the behavior of the material. Data analysis from the creep test indicates that the creep loading level significantly affects the response of the tested material. The AE rate analysis shows that no actual damage develops when a creep load is less than 20 % of the strength and significant micro damage accumulates when the applied creep load is more than 30 % of the strength value. The loading rate was found to have a significant effect on the measured tensile strength even at a relatively low temperature, and the measured tensile strength increases with the increase of the loading rate for all the test temperatures considered in this study. However, this effect was found to be diluted with the decrease of the test temperature. The AE analysis indicates that a damage zone develops in both the creep and strength tests. The damage zone decreases with temperature decrease and increases with the increase of the loading level applied during the creep test. The damage zone obtained from the strength test was approximately equal to that from the creep testing with a loading level about 25-50 % of the strength value.

Acoustic emission (AE) techniques have successfully been used for assuring the structural integrity of large rocket motorcases since 1963, and their uses have expanded to ever larger structures, especially as structural health monitoring (SHM) of large structures has become the most urgent task for engineering communities around the world. The needs for advanced AE monitoring methods are felt keenly by those dealing with aging infrastructures. Many publications have appeared covering various aspects of AE techniques, but documentation of actual applications of AE techniques has been mostly limited to reports of successful results without technical details that allow objective evaluation of the results. There are some exceptions in the literature. In this Special Issue of the Acoustics section of Applied Sciences, we seek contributions covering these exceptions cited here. Here, we seek contributions describing case histories of AE applications to large structures that have achieved the goals of SHM by providing adequate technical information supporting the success stories. Types of structures can include aerospace and geological structures, bridges, buildings, factories, maritime facilities, off-shore structures, etc. Experiences with AE monitoring methods designed and proven for large stru