PSI - Issue 3

D. Triantis et al. / Procedia Structural Integrity 3 (2017) 346–353 D. Triantis, E.D. Pasiou, I. Stavrakas, I. Dakanali and S.K. Kourkoulis / Structural Integrity Procedia 00 (2017) 000–000 7

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Fig. 6 (continued). The correlation of the released energy determined according to the data of the AE and PSC techniques.

4. Conclusions The present experimental protocol proved that upcoming failure of cement-mortar specimens under three-point bending is detected in a satisfactory manner by both sensing techniques used. More specifically the PSC increases reaching a maximum value and then it decreases abruptly a short while before fracture while at the same time the Ib value decreases attaining values between 0.8 and 1.0, indicating a very good qualitatively correlation of the techniques. From a quantitative point of view, the correlation of both AE and PSC techniques becomes clearer by taking into account the released energy. It was proven that the values of the specific quantity, calculated on the basis of the two techniques, when plotted against each other, obey a power law with an exponent equal to about ~0.9 for all specimens tested, without any exception at all. These results are in very good agreement with recently published ones (Pasiou & Triantis 2017) where cement mortar specimens as well as other brittle materials were subjected to uniaxial compres sion. The exponent of the power law for that kind of experiments was found equal to about 0.7. Concerning the role of the loading rate applied, it was concluded that it does not affect the qualitative or quantitative correlation of the results of the two techniques. Along the same lines the total electric charge released appears rather insensitive to the variations of the loading rate. On the other hand the maximum values of the PSC attained strongly depend on the loading rate according to a perfect linear relation. Another feature depending on the loading rate is the