Journals →  Gornyi Zhurnal →  2021 →  #5 →  Back

PHYSICS OF ROCKS AND PROCESSES
ArticleName Development of micro- and nanoindentation methods for assessing the mechanical properties of coals and their propensity to destruction
DOI 10.17580/gzh.2021.05.03
ArticleAuthor Kossovich E. L.
ArticleAuthorData

National University of Science and Technology "MISIS", Moscow, Russia:

E. L. Kossovich, Senior Researcher, Scientific and Educational Testing Laboratory of Physical Chemistry of Coals, Ph.D., e.kossovich@misis.ru

Abstract

The destruction of coals in the processes of mining, storage, transportation and processing is associated, among other, with their mechanical properties. As a rule, the mechanical properties of coals are evaluated by the resul ts of measurements of such characteristics as tensile and compressive strength, stiffness (elastic modulus) and Poisson’s ratio, etc. For this, experiments are carried out on specially prepared samples in tensile testing machines and mechanical presses. Such integral indicators characterize the mechanical behavior of coals at the macro scale and do not allow assessing the influence of structural features on the initiation of defects leading to destruction. In this regard, the characteristics of the mechanical properties of coals, obtained in areas comparable to the levels of microcracks initiation, are of interest. Micro- and nanoindentation techniques are quite simple to implement for obtaining the reliable information on various mechanical properties of materials at the appropriate scale levels. This paper is dedicated to an overview of the current state of research on the use of these methods to assess the mechanical properties of coals and their individual macerals, as well as their ability to crush with the formation of dust particles. The use of micro- and nanoindentation techniques made it possible to establish the differences in the mechanical properties of individual macerals of coals, as well as to characterize the heterogeneity of the distribution of various indicators characterizing mechanical properties within the individual macerals. Based on experimental data on nanoindentation and Raman spectroscopy, it was shown that the change in the mechanical properties (values of the modulus of elasticity and hardness) of vitrinite in the series of coal metamorphism is associated with an increase in the proportion of graphitized components in organic matter. Nanoindentation methods, combined with an analytical mathematical apparatus, made it possible to obtain data on the ability of coals to crush under mechanical effects with the formation of particles with sizes comparable to those of hazardous aerosol dust (class PM 2.5). The method of cyclic nanoindentation with an increasing maximum load was proposed as a method for determining the degree of coal tendency to fracture with the formation of dust. Its application made it possible to reveal the characteristics of irreversible changes occurring in the structure of coals during destruction. They are expressed in a change in their mechanical properties (stiffness and fracturing ability) with an increase in the applied load. The use of the cyclic nanoindentation method is a promising method for the qualitative and quantitative analysis of the degree of coal propensity to crushing with the formation of dust.
This work was carried out with the financial support of the Russian Science Foundation (Grant No. 18-77-10052).

keywords Сoal, dust, mechanical properties, crushing, nanoindentation, microindentation, cyclic loading
References

1. GOST 21206–75. Coalsand anthracite. Determination method for microhardness and microbrittleness (with amendments No. 1, 2). Moscow : IPK "Izdatelstvo standartov", 2000. 7 p.
2. GOST R 59262–2020. Brown coals, hard coals and anthracite. Method for determination of microhardness and microbrittleness. Moscow : Standartinform, 2020. 12 p.
3. Bulychev S. I., Alekhin V. P., Shorshorov M. K., Ternovskiy A. P., Shnyrev G. D. Determination of Young modulus by the hardness indentation diagram. Zavodskaya Laboratoriya. 1975. Vol. 41, No. 9. pp. 1137–1140.
4. Oliver W. C., Pharr G. M. Measurement of hardness and elastic modulus by instrumented indentation: Advances in understanding and refinements to methodology. Journal of Materials Research. 2004. Vol. 19, No. 1. pp. 3–20.
5. Kožušníková A. Determination of Microhardness and Elastic Modulus of Coal Components by Using Indentation Method. GeoLines. 2009. Vol. 22. pp. 40–43.
6. Godyń K., Kožušníková A. Microhardness of Coal from Near-Fault Zones in Coal Seams Threatened with Gas-Geodynamic Phenomena, Upper Silesian Coal Basin, Poland. Energies. 2019. Vol. 12, Iss. 9. DOI: 10.3390/en12091756
7. Kossovich E. L., Dobryakova N. N., Epshtein S. A., Belov D. S. Mechanical properties of coal microcomponents under continuous indentation. Journal of Mining Science. 2016. Vol. 52, Iss. 5. pp. 906–912. DOI: 10.1134/S1062739116041382
8. Epshtein S. A., Borodich F. M., Bull S. J. Evaluation of elastic modulus and hardness of highly inhomogeneous materials by nanoindentation. Applied Physics A: Materials Science and Processing. 2015. Vol. 119, Iss. 1. pp. 325–335. DOI: 10.1007/s00339-014-8971-5
9. Borodich F. M., Bull S. J., Epshtein S. A. Nanoindentation in Studying Mechanical Properties of Heterogeneous Materials. Journal of Mining Science. 2015. Vol. 51, Iss. 3. pp. 1062–7391. DOI: 10.1134/S1062739115030072
10. Vranjes S., Misch D., Schöberl T., Kiener D., Gross D., Sachsenhofer R. F. Nanoindentation study of macerals in coals from the Ukrainian Donets Basin. Advances in Geosciences. 2018. Vol. 45. pp. 73–83.
11. Yihuai Zhang, Lebedev M., Al-Yaseri A., Hongyan Yu, Xiaomeng Xu, Iglauer S. Characterization of nanoscale rockmechanical properties and microstructures of a Chinese sub-bituminous coal. Journal of Natural Gas Science and Engineering. 2018. Vol. 52. pp. 106–116.
12. Yihuai Zhang, Lebedev M., Al-Yaseri A., Hongyan Yu, Xiaomeng Xu et al. Nanoscale rock mechanical property changes in heterogeneous coal after water adsorption. Fuel. 2018. Vol. 218. pp. 23–32.
13. Chenliang Hou, Bo Jiang, Hewu Liu, Yu Song, Shaochun Xu. The differences of nanoscale mechanical properties among coal maceral groups. Journal of Natural Gas Science and Engineering. 2020. Vol. 80. DOI: 10.1016/j. jngse.2020.103394
14. Ulyanova E. V., Molchanov A. N., Prokhorov I. Y., Grinyov V. G. Fine structure of Raman spectra in coals of different rank. International Journal of Coal Geology. 2014. Vol. 121. pp. 37–43.
15. Wendong Zhou, Hetang Wang, Deming Wang, Yunhe Du, Kang Zhang, Yongchao Qiao. An experimental investigation on the influence of coal brittleness on dust generation. Powder Technology. 2020. Vol. 364. pp. 457–466.
16. Argatov I. I., Borodich F. M., Epshtein S. A., Kossovich E. L. Contact stiffness depth-sensing indentation: Understanding of material properties of thin films attached to substrates. Mechanics of Materials. 2017. Vol. 114. pp. 172–179. DOI: 10.1016/j.mechmat.2017.08.009
17. Galanov B. A., Grigoriev O. N. Analytic indentation model of brittle solids. Electron microscopy and strength of materials. 2006. Vol. 13. pp. 4–47.
18. Kossovich E. L., Borodich F. M., Epshtein S. A., Galanov B. A. Indentation of bituminous coals: Fracture, crushing and dust formation. Mechanics of Materials. 2020. Vol. 150. DOI: 10.1016/j.mechmat.2020.103570
19. Kossovich E. L., Epshtein S. A., Borodich F. M., Dobryakova N. N., Prosina V. A. Connections between micro/nano scale heterogeneity of mechanical properties of coals and their propensity to outbursts and crushing. GIAB. 2019. Vol. 2019, No. 5. pp. 156–172. DOI: 10.25018/0236-1493-2019-05-0-156-172
20. Hardiman M., Vaughan T. J., McCarthy C. T. A review of key developments and pertinent issues in nanoindentation testing of fibre reinforced plastic microstructures. Composite Structures. 2017. Vol. 180. pp. 782–798.
21. Grigoriev O. N., Galanov B. A., Kotenko V. A., Ivanov S. M., Kovalchuk V. V., Lazhevsky V. A. Contact strength and fracture toughness of brittle materials. Metallofizika i noveyshie tekhnologii. 2005. Vol. 27, No. 8. pp. 1095–1112.
22. Smerdova O., Pecora M., Gigliotti M., Castagnet S. Cyclic indentation test to characterise viscoelastic behaviour of polymers. Nanomechanical Testing in Materials Research and Development VI : Proceedings of Engineering Conferences International ECI Digital Archives. New York : Engineering Conference International, 2017.
23. Němeček J. Creep effects in nanoindentation of hydrated phases of cement pastes. Materials Characterization. 2009. Vol. 60, Iss. 9. pp. 1028–1034.
24. Mars W. V., Fatemi A. Factors that Affect the Fatigue Life of Rubber: A Literature Survey. Rubber Chemistry and Technology. 2004. Vol. 77, Iss. 3. pp. 391–412.
25. Cole D. P., Henry T. C., Gardea F., Haynes R. A. Interphase mechanical behavior of carbon fiber reinforced polymer exposed to cyclic loading. Composites Science and Technology. 2017. Vol. 151. pp. 202–210.

26. Faisal N. H., Prathuru A. K., Goel S., Ahmed R., Droubi M. G. et al. Cyclic Nanoindentation and Nano-Impact Fatigue Mechanisms of Functionally Graded TiN/TiNi Film. Shape Memory and Superelasticity. 2017. Vol. 3, Iss. 2. pp. 149–167.
27. Sergejev F., Kimmari E., Viljus M. Residual Stresses in TiC-based Cermets Measured by Indentation. Procedia Engineering. 2011. Vol. 10. pp. 2873–2881.
28. Bagal A., Zhang X. A., Shahrin R., Dandley E. C., Junjie Zhao et al. Large-Area Nanolattice Film with Enhanced Modulus, Hardness, and Energy Dissipation. Scientific Reports. 2017. Vol. 7, No. 1. 9145. DOI: 10.1038/s41598-017-09521-6
29. Hirsch P. B. X-ray scattering from coals. Proceedings of the Royal Society of London. Series A: Mathematical and Physical Sciences. 1954. Vol. 226, Iss. 1165. pp. 143–169.
30. Kossovich E. L., Epshtein S. A., Golubeva M. D., Krasilova V. A. On using cyclic nanoindentation technique to assess coals propensity to fine dust formation. GIAB. No. 5. pp. 112–121.

Language of full-text russian
Full content Buy
Back