PSI - Issue 39

Viktor Morozov et al. / Procedia Structural Integrity 39 (2022) 432–440 Author name / Structural Integrity Procedia 00 (2019) 000–000

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80 mm with various heights. The exploding wire was a 6x20 mm paper strip coated with aluminium foil. The wire was placed between the bottom grain of the sample and basement, above preliminary crack (or cut). This granted mechanical pulse duration ~20 µs. An example of a mechanical pulse profile registered by piezo-probe is presented in Fig. 6. To summarize, we achieved in our experiments generation of mechanical pulses in a range from 1 µs up to 20 µs for cylinder and lamel samples made of PMMA and from 2.5 µs up to 5 µs for cylinder samples made of fluoroplastic. a b

Fig. 4. Characteristic current and mechanical pulse waveforms registered with high-voltage setup for PMMA (a) and fluoroplastic (b) cylinder samples.

Fig. 5. Low-voltage setup for experiments with cylinder lameles: high-voltage source (1) is identical with low-voltage experiments on cylinders, sample (2), PMMA base (3), exploding wire (4), container for sample (5), container for photodiodes (6), artificial pre-crack (7), propagating crack (8), lasers (9,10), photodiodes (11, 12), Rogovskii coli (current registration device) (13) and ooscilloscope (14). Laser beams marked with red lines. Time difference between laser beams cut off is base estimate average crack propagation velocity. 3. Discussion of results In our experiments, we performed registration of mechanical loading pulses profiles and determined this way minimal fracturing amplitude of mechanical pulses by the duration of these pulses. Registered amplitudes of mechanical stresses were 1067 MPa for experiments with cylinders on low-voltage setup, 80..120 MPa for experiments with lameles, and 1650 MPa for experiments with cylinders on high-voltage setup. We utilized two approaches during our study on PMMA lamel samples. In the first approach, we initiated a crack in the sample with EEW and controlled its further propagation. In the second approach, pre-crack of specified length