13th International Conference on Fracture June 16–21, 2013, Beijing, China -3- also a dominant tensile cracking mode [8]. 2.2. Three-point bending test The results of the three-point bending test performed on a beam having dimensions 100x100x840 mm (Fig. 2a) are herein reported. From the mechanical point of view, the overall behavior is characterized by a normal softening post-peak phase, as shown in Fig. 2b. The fracture energy, evaluated according to the RILEM recommendations [15], is equal to 0.124 N/mm. The corresponding total dissipated energy is equal to 0.62 J. The evolution of the applied load, and of recorded AE with time is shown in Fig.3. The AE average frequencies range between 180 kHz and 150 kHz (Fig. 4a). A shift in frequencies from higher to lower values (Fig. 4a) and a significant decrease in RA values (Fig. 4b) after the peak load are observed (Fig. 4b). The evolution of the damage from the initial notch towards a Mode I crack is proved both by the RA and the AF decrease. (a) (b) Figure 2. Three-point bending test: (a) experimental setup; (b) load vs. deflection curve.
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