![]() Taking into account the similarities between seismicity and AE activity, as already mentioned, the application of NESM in fracture mechanics concerning stressed rocks is valid. NESM has been applied in a variety of fields here, the authors focus mainly on NESM applications of seismology, plate tectonics and fracture mechanics. Non-extensive statistical mechanics (NESM) introduced by Tsallis, based on the principle of entropy have been proven a reliable statistical framework for analysing intricate dynamical systems such as the fracture mechanisms responsible for the generation of earthquakes and AEs. In this direction, assuming that the fracture phenomena which instigate the creation of both earthquakes and AEs, although at different scales, are non-linear procedures of intricate dynamical systems during their non-equilibrium stationary states-one may even consider them as phase transitions-are governed by multi-fractality, self-similar structure, exhibiting large scale correlations and memory effects the use of advance statistical tools is advocated, instead of the classical statistical physics. Taking into account that the AEs are considered to be a form of microseismicity, it is reasonable to assume that tools used for the analysis of earthquakes could also be used to analyse the AE activity after proper modifications. The AE technique has been employed successfully in monitoring the overall accumulated damage and remaining service life in situ (e.g., industrial equipment, full-scale structures, ancient monuments) and laboratory scale (e.g., mechanically loaded specimens). Several AE parameters and indices have been considered as potential pre-failure indicators for the estimation of the upcoming catastrophic fractures. ![]() The study of AE can provide information regarding the fracture mechanisms as well as the crack generation and development processes taking place inside the mechanically stressed materials. Considering isotropic, linear materials, these waves propagate inside the material in a spherical manner towards its surface, where they are detected by properly attached piezoelectric sensors. Amongst them is the acoustic emission (AE) technique, which is based on the detection of the transient elastic waves that are produced due to the nucleation and propagation of cracks. In the quest to understand the latent mechanisms of fracture and crack development in stressed materials, many non-destructive monitoring techniques have been used. Results seem to support the idea of using the entropic index q as a potential pre-failure indicator for the impending catastrophic fracture of the mechanically loaded specimens. The entropic index q shows a systematic behaviour strongly related to the various stages of the implemented loading protocols for all the examined specimens. For each examined specimen, the corresponding Tsallis entropic q-indices and the parameters β q and τ q were calculated. The NESM analysis showed that the cumulative distribution functions of the AE interevent times (i.e., the time interval between successive AE hits) follow a q-exponential function. In the current work, acoustic emission (AE) data recorded when marble and cement mortar specimens were subjected to three distinct loading protocols until fracture, are discussed in the context of NESM. NESM has been shown to provide the necessary theoretical and analytical implementation for studying complex systems such as the fracture mechanisms and crack evolution processes that occur in mechanically loaded specimens of brittle materials. ![]() Non-extensive statistical mechanics (NESM), introduced by Tsallis based on the principle of non-additive entropy, is a generalisation of the Boltzmann–Gibbs statistics. ![]()
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