Issue 40

A. Kyriazopoulos, Frattura ed Integrità Strutturale, 40 (2017) 52-60; DOI: 10.3221/IGF-ESIS.40.05 56 where,  is the standard deviation of the magnitude distribution in one group of events,  is the mean value of the magnitude distribution in the same group of events, and  1 as well as  2 are constants, for which usually a value equal to 1 is adopted [1]. In order to highlight the variability of the b I -value, during the three experiments, the b-value analysis of ΑΕ is, in general, applied to a certain number of events, as follows: from event 1 to n, then from event 2 to n+1, and so on. The determina- tion of the value of n has been considered by Shiotani et al. [32] and Colombo et al. [22], since it constitutes a parameter that can influence the results. A value exceeding n=50 is assumed to be a satisfactory one. In the present study, n=70 has been selected. Each value of b I was calculated from a group of the events 1 to 70, consequently from 2 to 71, and so on. Each calculated b I value is associated to the time of the 70th event of each group and to that of the corresponding value of normalized (L/L f ) load. The variability of the b I -value during the three experiments with respect to the normalized (L/L f ) load is shown in Fig. 4. In the same figure the corresponding variation of PSC signals is also presented. Figure 4: Variation of b I -values and PSC signals vs. normalized load (L/L f ) for the three conducted experiments. CB01 0 10 20 30 0 0.2 0.4 0.6 0.8 1 L/Lf PSC (pA) 0.0 0.5 1.0 1.5 2.0 2.5 3.0 Ib‐value CB02 0 10 20 30 0 0.2 0.4 0.6 0.8 1 L/Lf PSC (pA) 0.0 0.5 1.0 1.5 2.0 2.5 Ib ‐ value CB03 0 10 20 30 0 0.2 0.4 0.6 0.8 1 L/Lf PSC (pA) 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 Ib ‐ value