Acoustic emission as a tool for fracture monitoring

Crack initiation is a complex and multiscale process which is intimately associated with energy redistribution and release due to the formation of fracture surfaces, transient effects that are associated with irrecoverable amounts of energy in this process and changes of the stored energy in the material after a crack increment has occurred. In this incremental view of crack initiation the portion of the energy that gets emitted by a crack source in the form of transient elastic waves with frequencies dependent on the crack source but practically in the ultrasonic range is known as Acoustic Emission. The focus of this talk is to present an integrated analysis of Acoustic Emission as it relates to this symposium. Extensive experimental results from inside the Scanning Electron Microscope all the way to the scale of structural components are presented alongside a thorough numerical approach in which wave generation due to crack initiation is explicitly modeled using 3D finite element calculations, in addition to quantifying the energy dissipation associated with the first crack increment. Experimental and computational results are finally used to talk about the realistic potential of this method for actual applications in the effort to link diagnostics and prognostics.