Issue 43

M. Davydova et alii, Frattura ed Integrità Strutturale, 43 (2018) 106-112; DOI: 10.3221/IGF-ESIS.43.08 108 photomultiplier tubes (PMT) with the rise time of 0.8 ns, which were located at the opposite lateral surfaces of the sample. To improve reliability of experiments, two PMT were used. From the PMT signal was transmitted to the Tektronix digital oscilloscope DP07254 with a band width of 3.5 GHz and sampling rate less than 10 GHz. Thus, the modified setup had the advantage of getting both the deformation curves and the statistic characteristics of the fragmentation process, based on the data on the two types of distribution: size distribution of the spatial parameter (fragment size) and size distribution of the temporal parameter (the interval between fractoluminiscence impulses). Figure 2: Sample with porosity of 30%: a) CT image of the sample cross section; b) fragment size distribution function for 5 specimens; c) typical time interval distribution function. D YNAMIC FRAGMENTATION RESULTS ig. 1(b) shows typical stress-strain curves for ceramic samples with different porosity before sintering. It should be noted that for the samples with porosity less than 45%, the stress-strain    ( ) curves have one stress maximum, whereas for the samples with porosity of 45% and 60% the    ( ) curves show two maxima. The experimental data were used to construct the cumulative fragment size distribution, i.e., the relationships between the number of fragments, N , the size (mass) of which is larger than a prescribed value, and the size, r (mass m ), of the fragment. The fragment mass was measured by weighing fragments on the electronic balance HR-202i. Fig. 2(b) and Fig. 3(b) present the log-log plots of the cumulative fragment size distribution for the samples, in which the initial porosity of the powder component was 20%, (Fig. 2(b)), and 60%, (Fig. 3(b)). The above distributions are well described (R 2 >0.96) by the power law function: F a) b)