Elastic wave, which is formed due to sudden rearrangement of stresses in a material, is called acoustic emission (AE). It is widely used in nondestructive testing (NDT) of materials and structures especially in health monitoring of structures for damage detection. When a body is subjected to an external force (in the form of changing pressure, load, or temperature), any micro fracture inside the body releases energy in the form of AE wave, which is received by sensor and later on is converted to electrical signal for inspection. In early stage, major importance was given on studying the AE characteristics during the deformation and fracture on various materials (by J. Kaiser in Germany in 1950 and B. H. Schofield in the USA in 1954). Nowadays, lots of research are conducting on formulating the theories behind AE formation, propagation, and inspection in various fields as an important health monitoring tool for NDT. In this chapter, I would like to elaborate a “feature outlook of AE” based on past, present, and future perspectives; “AE monitoring” procedure based on theoretical and experimental perspectives; and smart applications in structural health monitoring based on industrial and biostructural perspectives with related figures and tables.
Part of the book: Structural Health Monitoring from Sensing to Processing