PSI - Issue 33

Irina A. Bannikova et al. / Procedia Structural Integrity 33 (2021) 357–364 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

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The samples had average values for height ~21.6 mm, and diameter ~26.7 mm, density ~ 2700 kg/m 3 . Sample No. 1 - the presence of chips along the perimeter, initially a crack in the rock (L-shaped, at an angle of ~ 70 degrees). Sample No. 2 - the presence of chips around the perimeter, no visible cracks. Sample No. 3 - inclined cylinder, cleavage from the edge of bases one, a crack in volume of the rock along the perimeter. Sample No. 4 had a continuous crack in the volume of the cylinder, along the perimeter there were small chips ~ 0.5 mm. For the mode of "preserving fragments", quartzite cylinders were wrapped in several layers of adhesive tape. 3. Experiment Uniaxial compression tests of cylindrical quartzite specimens were carried out on a Shimadzu AGX-Plus electromechanical universal testing machine and on a Split Hopkinson pressure bar. 3.1. Uniaxial quasi-static compression In the case of quasi-static compression (see Fig. 2), a cylindrical specimen was placed in the center of the platform between the plates-traverses of the Shimadzu AGX-Plus 1 loading machine. Fractoluminescence was registered by two methods. The first used the joint operation of PMT 4 and a Tektronix DPO 7254 Digital Phosphor Oscilloscope FD 5 . In the second, a high-speed video camera Photron FASTCAM SA-Z 2100K 2 was used, which filmed 3 simultaneously the failure of the sample and fractoluminescence. In this case, the synchronization of the camera and loading start was performed manually. In the settings of the Shimadzu AGX-Plus loading machine, the sample parameters (height, diameter, shape) and loading speed (1 mm/s) were set. The loading machine stopped automatically when the sample was completely failed.

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Fig. 2. (a): 1 - a electromechanical universal testing machine Shimadzu AGX-Plus (speed ~1 mm/s), attachment Shimadzu - «TRAPEZIUMX»; 2 – a high speed camera Photron FASTCAM SA- Z 2100K (frequency 6×10 4 frames/s); 3 – PC for camera control; 4 – a PMT; (b): 5 - Tektronix DPO 7254 Digital Phosphor Oscilloscope FD (one channel for photomultiplier tube – 4). Load-Displacement curves are presented on Fig. 3. For sample No. 4: the first part of the signal corresponds to the formation of cracks in the sample, at which the sample has not yet collapsed, the second – additional loading and complete failure as shown in the photo for sample No. 2 (see. Fig. 4, b ). A PMT was used to detect the fractoluminescence of the sample No. 1 in the process of uniaxial quasi-static fracture. See Fig. 5. The failure was accompanied by single signals (A) and multiple impulses (B). This is typical for the main cracks initiation in the sample (along the height of the sample throughout the entire volume) and complete fragmentation.