Exploring the acoustic activity in brittle materials in terms of the position of the acoustic sources and the power of the acoustic signals - Part II: Applications

The present study is the continuation of a previously published one (Part I), in which the D- (three-dimensional distance between the sources of any two successive acoustic events) and P-functions (the rate of the energy of the acoustic signals) were introduced for the analysis of the acoustic activity developed in marble specimens under uniaxial tension. The concepts introduced in Part I and the analysis procedure analytically described there, are here employed to analyze the acoustic emissions data gathered from additional experimental protocols in order to support and validate the conclusions drawn in Part I. In this direction, the acoustic activity generated in marble and concrete (either plain or reinforced with short polyolefin fibers) specimens under uniaxial compression or three-point bending, respectively, is studied in the direction of detecting characteristics of the temporal evolution of the D- and P-functions that could provide early hints warning about upcoming fracture. The evolution of the D- and P-functions is considered in juxtaposition to that of the F-function, which is in fact a convenient and flexible mean for the quantification of the average frequency of generation of the acoustic events. The conclusions drawn here are in excellent agreement with the respective ones drawn in Part I, suggesting that the D- and P-functions can indeed be a valuable tool in hands of engineers working in the field of Structural Health Monitoring of structures made of brittle building materials.