Damage Evolution in Quasi-Brittle Materials: Experimental Analysis by AE and Numerical Simulation

Abstract

This work investigates the extension of a total-collapse prediction method to include local failures in quasi-brittle materials as they undergo damage processes. The analysis is experimentally conducted with acoustic emission data from a basalt specimen under a prescribed displacement loading test. The proposed failure index is compared with the well-established b-value to evaluate its usefulness; the simulation results are also used to further investigations. In particular, the simulations show that the parameter calculation can be carried out by indirectly estimating the elastic energy released within the system throughout the damage process, which cannot be measured directly. It is concluded that the proposed method is valid, consistently outperforming the b-value as a failure precursor throughout the experimental studies.

Analysis of Damage Process in a Pre-Notched Rock Specimen: The Synergy between Experimental Results and Simulations Using a Peridynamic Model

“…The moving average carried out in a window of 175 values is indicated in red in the same figure, and a red diamond indicates the maximum value of the DPH index. This value, as discussed in [26], can be considered a complementary precursor to collapse when an acoustic emission test is carried out. Note that, in the experimental case, the reaction load of the support (indicated by label 3 in Figure 5a) times the prescribed displacement is considered a measure of elastic energy, and from this value the derivative is calculated.…”

“…Note that, in the experimental case, the reaction load of the support (indicated by label 3 in Figure 5a) times the prescribed displacement is considered a measure of elastic energy, and from this value the derivative is calculated. (vi) Considering the methodology adopted by [26] and that which was previously described for determining a measure of elastic energy in an experimental test, it is possible to see an abrupt increase in the DPH index at t n ≈ 0.55. This is further evidence that the support cannot fix the specimen correctly before t n ≈ 0.55.…”

“…In the original work of [25], this index was computed with numerical results, making the study of elastic energy evolution available. In [26], this idea was generalized by considering the fact that the product of the support-prescribed displacement and the corresponding reaction is proportional to the elastic energy stored in the system during the test. The performance of the cited index applied to a real problem is shown.…”

“…(d) b-value evolution obtained using sensor 1, sensor 2, and ∆E k . (e) DPH index evolution, obtained using the methodology of[26]. (f) DPH index evolution, computed using the elastic energy in the simulation.…”