František Chmelík

Abstract:

Plastic deformation and failure of structural integrity in materials are frequently accompanied by acoustic emission (AE). AE is a multi-scale phenomenon, defined as stress waves generated within the material due to (micro)structure changes (usually linked with structural defects dynamics), ranging from earthquakes and landslides to collective dislocation motion on micron scales. Recently, AE measurements performed on bulk as well as miniaturized samples (micropillars) revealed that the motion of dislocations resembles a stick-and-slip process, which may even develop in a series of unpredictable local strain bursts with a scale-free size distribution, e.g. in single crystals. Despite of fundamental differences in the mechanism as well as length and timescales, dislocation avalanches and earthquakes can be, from the point of view of AE, described in a similar way.
The talk will cover an introduction to the AE technique, followed by discussion of several applications, from fundamentals of defect dynamics to a couple of topics in geology and materials engineering.