PSI - Issue 65

Available online at www.sciencedirect.com Available online at www.sciencedirect.com ScienceDirect Structural Integrity Procedia 00 (2024) 000–000 Available online at www.sciencedirect.com ScienceDirect Structural Integrity Procedia 00 (2024) 000–000

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ScienceDirect

Procedia Structural Integrity 65 (2024) 32–38

The 17th International Conference on MECHANICS, RESOURCE AND DIAGNOSTICS OF MATERIALS AND STRUCTURES (MRDMS 2023) Features of the microdefects formation in geomaterials when exposed to high-power nanosecond electromagnetic pulses Igor Zh. Bunin a, * and Alexey N. Kochanov a a N.V.Melnikov's Institute of Comprehensive Exploitation of Mineral Resources Russian Academy of Sciences, ICEMR RAS, 4, Kryukovsky Tupik, Moscow, 111020, Russia Experimental investigations were conducted to study the development of microdefects in rock samples (coal, granite, sandstone and quartz) under the influence of high-power nanosecond electromagnetic pulses (HPEMP). With the HPEMP effect, the duration of high-voltage nanosecond pulses was 4–10 ns. Pulse amplitude was U ~25–30 kV; strength of the electric field in the 5 mm interelectrode gap, E ~10 7 V×m 1 ; rate of nanosecond pulse repetition was f =100 Hz. The duration of rock samples treatment varied in the range of t treat = 10–300 s. Analytical scanning electron microscopy (SEM–EDX) was used to assess changes in the microstructure of the samples, and computer X-ray microtomography was used in addition for coal samples. The size of the opening of microcracks is determined, their structural features are analyzed. The morphology and substructure of microcracks in coal, sandstone, and granite differed significantly, so that for sandstone and granite, the formation and propagation of microcracks occurred predominantly along grain boundaries. Coal samples seem to be characterized by a mixed fracture mechanism. On the whole, most of the microcracks formed in rocks as a result of the impact of HPEMP had the character of normal rupture cracks. Possible mechanisms of microcracks formation are discussed. We have considered such failure mechanisms of geomaterials as the skin effect (for coal), the formation of microchannels of electrical breakdown (quartz) and the migratory (interlayer) and/or electron-relaxation polarization of others dielectric minerals. © 2024 The Authors, Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of MRDMS 2023 organizers Keywords: Geomaterials; high-power nanosecond electromagnetic pulses; mechanisms of disintegration; microcracks; electron microscopy The 17th International Conference on MECHANICS, RESOURCE AND DIAGNOSTICS OF MATERIALS AND STRUCTURES (MRDMS 2023) Features of the microdefects formation in geomaterials when exposed to high-power nanosecond electromagnetic pulses Igor Zh. Bunin a, * and Alexey N. Kochanov a a N.V.Melnikov's Institute of Comprehensive Exploitation of Mineral Resources Russian Academy of Sciences, ICEMR RAS, 4, Kryukovsky Tupik, Moscow, 111020, Russia Abstract Experimental investigations were conducted to study the development of microdefects in rock samples (coal, granite, sandstone and quartz) under the influence of high-power nanosecond electromagnetic pulses (HPEMP). With the HPEMP effect, the duration of high-voltage nanosecond pulses was 4–10 ns. Pulse amplitude was U ~25–30 kV; strength of the electric field in the 5 mm interelectrode gap, E ~10 7 V×m 1 ; rate of nanosecond pulse repetition was f =100 Hz. The duration of rock samples treatment varied in the range of t treat = 10–300 s. Analytical scanning electron microscopy (SEM–EDX) was used to assess changes in the microstructure of the samples, and computer X-ray microtomography was used in addition for coal samples. The size of the opening of microcracks is determined, their structural features are analyzed. The morphology and substructure of microcracks in coal, sandstone, and granite differed significantly, so that for sandstone and granite, the formation and propagation of microcracks occurred predominantly along grain boundaries. Coal samples seem to be characterized by a mixed fracture mechanism. On the whole, most of the microcracks formed in rocks as a result of the impact of HPEMP had the character of normal rupture cracks. Possible mechanisms of microcracks formation are discussed. We have considered such failure mechanisms of geomaterials as the skin effect (for coal), the formation of microchannels of electrical breakdown (quartz) and the migratory (interlayer) and/or electron-relaxation polarization of others dielectric minerals. © 2024 The Authors, Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of MRDMS 2023 organizers Keywords: Geomaterials; high-power nanosecond electromagnetic pulses; mechanisms of disintegration; microcracks; electron microscopy © 2024 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of MRDMS 2023 organizers Abstract

* Corresponding author. Tel.: +7-495-360-7328 ; fax: +7-495-360-89-60 . E-mail address: bunin_i@mail.ru * Corresponding author. Tel.: +7-495-360-7328 ; fax: +7-495-360-89-60 . E-mail address: bunin_i@mail.ru

2452-3216 © 2024 The Authors, Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of MRDMS 2023 organizers 2452-3216 © 2024 The Authors, Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of MRDMS 2023 organizers

2452-3216 © 2024 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of MRDMS 2023 organizers 10.1016/j.prostr.2024.11.006