13th International Conference on Fracture June 16–21, 2013, Beijing, China -3- with the oscilloscope (oscilloscope sample rate is 1 GHz). The appearance of the new surfaces produces the impulses with a sharp front with typical rise time about 5 ns (Fig. 3). 0 20 40 60 80 100 120 20 40 60 80 100 Time, ns mV Figure 3. Typical fractoluminescence event. Figure 4 shows the signal from the oscilloscope. One can note that fragmentation process lasts 2-3 decades longer than loading time (20 μs). Pulse rate does not decrease monotonically; instead of this one can note avalanches or bursts of pulses similar to the avalanches on the sand pile which is common illustration of SOC. Figure 4. Signal from the oscilloscope (upper, polarity of pulses is reversed) and pulse rate (lower). Time scale is the same for both graphs. 1. Data analysis The first step of data processing is signal filtration. Because the fractoluminescence pulses have a time, ms events per µs
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