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Lookup NU author(s): Emeritus Professor Steve Bull
This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License (CC BY-NC 4.0).
Copyright © 2026. Published by Elsevier B.V. Although coal is often treated as a homogeneous material in macroscopic mechanical testing, it is intrinsically heterogeneous across multiple length scales, and this heterogeneity at the micro- and nanoscale presents significant challenges for measurement techniques. This study reviews the development of indentation techniques and analyzes the principles and application of microindentation and depth-sensing nanoindentation (DSNI) for evaluating the mechanical properties of coal. It emphasizes the integration of DSNI with microscopy and thin-film preparation to improve the accuracy of mechanical measurements in heterogeneous coal systems. An effective method for estimating the elastic modulus of thin films is proposed, with an evaluation of the applicability of the Galanov-Dub and Oliver-Pharr methods. The phenomenon of coal dust formation during indentation is also examined, suggesting that there should be more refined testing standards tailored to coal materials.
Author(s): Gao Z, Borodich FM, Epshtein SA, Kossovich EL, Bull SJ, Galanov BA, Jin X
Publication type: Article
Publication status: Published
Journal: Results in Engineering
Year: 2026
Volume: 30
Print publication date: 01/06/2026
Online publication date: 23/03/2026
Acceptance date: 22/03/2026
Date deposited: 14/04/2026
ISSN (electronic): 2590-1230
Publisher: Elsevier BV
URL: https://doi.org/10.1016/j.rineng.2026.110231
DOI: 10.1016/j.rineng.2026.110231
Data Access Statement: Data will be made available on request.
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