13th International Conference on Fracture June 16–21, 2013, Beijing, China -1- Dynamics of Fragmentation of Fused Quartz Rods Sergey Uvarov*, Marina Davydova, Oleg Naimark Laboratory of PFC, ICMM UB RAS, Perm 614013, Russia *Corresponding author: usv@icmm.ru Abstract The dynamic fragmentation was studied in the impact experiments with quartz cylindrical rods using a gas gun. Impact leads to the formation of fracture surfaces, which produce an intensive light emission (mechanoluminescence ). Mechanoluminescence was registered by two Photo Multiplayer Tubes (PMT) connected with the oscilloscope. Mechanoluminescence was in form of impulses with typical rise time 2-5 ns and fall time 5-50ns. It was found that the impulse frequency was not decreases monotonically but there was some kind of bursts or avalanches and fragmentation process time is 3-4 orders longer than acoustic time (time needed for compression wave to travel along the specimen). We found that the distribution of intervals between luminescence impulses is a power law distribution. Keywords Fractoluminescence, scaling, power law, fragmentation 1. Introduction Per Bak et al. in their paper “Self-Organized Criticality: An Explanation of 1/f Noise” mentioned: “The common feature for these systems is that the power-law temporal or spatial correlations extend over several decades where naively one might suspect that the physics would vary dramatically. Dynamical systems with extended spatial degrees of freedom naturally evolve into self-organized critical structures of states which are barely stable. We suggest that this self-organized criticality is the common underlying mechanism behind the phenomena described above. The combination of dynamical minimal stability and spatial scaling leads to a power law for temporal fluctuations. The noise propagates through the scaling clusters by means of a "domino" effect upsetting the minimally stable states. Long-wavelength perturbations cause a cascade of energy dissipation on all length scales” [2]. To confirm the fact that the fragmentation exhibits SOC, we need to establish the existence of a power law for temporal and spatial quantities. The evidence of the spatial scaling for the fragmentation of brittle materials under different loading conditions was given in paper [1] . For measurement of temporal scale we developed an experimental device to determine the time interval between the impulses of the light reflected from the newly created fracture surfaces. In our investigation (fragmentation of quartz rods under dynamic loading), SOC means that there exist: •power law distribution of fragment size; •power law distribution of time interval between the impulses of the light reflected from newly created surfaces. 2. Experiment The fragmentation statistics was studied in recovery dynamic experiments with fused quartz cylindrical rods which have 10 mm diameter and 120 mm length.
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