Mechanical Properties of Thin Films of Coals by Nanoindentation

Kossovich, E. L.; Эпштейн, С. А.; Dobryakova, N. N.; Minin, M. G.; Gavrilova, Darya

doi:10.1007/978-3-319-77788-7_6

Cited by 7 publications

(4 citation statements)

References 8 publications

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“…More advanced micro and nanoindentation procedures and results of their applications to coals are presented in [33][34][35]. However, there are still many questions related to nanoindntation testing of coals.…”

Section: The Microhardness Value Is Calculated Asmentioning

confidence: 99%

“…In addition, thin coal films are transparent, therefore may be used for experiments with microscopes operating in transmitted light. Using the above described procedure employing thin films of coals, mechanical properties of lignites were studied at nanoscale[34]. These studies revealed changes in vitrinite mechanical properties with coal type and rank, while values of mechanical properties of inertinites did not vary practically for all lignite and bituminous (hard) coals.…”

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confidence: 99%

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Mechanical, structural and scaling properties of coals: depth-sensing indentation studies

et al. 2019

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This paper discusses special features of mechanical behaviour of coals discovered using depth-sensing indentation (DSI) techniques along with other traditional methods of material testing. Many of the special features are caused by the presence of multiscale complex heterogeneous internal structure within the samples and brittleness of some coal components. Experimental methodology for studying mechanical properties of coals and other natural extreme materials like bones are discussed.It is argued that values of microhardness of bituminous coals correlate strongly with the maximum load, therefore the use of this parameter in application to coals may ⋆ Research was supported by the Russian Science Foundation (grant #16-17-10217) be meaningless. For analysis of the force-displacement curves obtained by DSI, both Oliver-Pharr and Galanov-Dub approaches are employed. It is argued that during nanoindentation, the integrity of the internal structure of a coal sample within a small area of high stress field near the tip of indenter may be destroyed. Hence, the standard approaches to mechanical testing of coals should be re-examined.

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Section: The Microhardness Value Is Calculated Asmentioning

confidence: 99%

mentioning

confidence: 99%

Mechanical, structural and scaling properties of coals: depth-sensing indentation studies

et al. 2019

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“…Traditional microscopy methods only allow for the evaluation of structural changes on sample surfaces (Epshtein et al 2019a, b;Zhang et al 2019). The same limitation applies to the study of coal mechanical properties by Nano indentation methods (Kossovich et al 2016(Kossovich et al , 2018. The study of crack formation in the entire volume of a sample is possible using passive and active acoustic measurements in the ultrasonic frequency range.…”

Section: Introductionmentioning

confidence: 99%

Experimental study of coal fracture dynamics under the influence of cyclic freezing–thawing using shear elastic waves

Nikolenko

Эпштейн

Шкуратник

et al. 2020

Int J Coal Sci Technol

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Cyclic freezing-thawing can lead to fracture development in coal, affecting its mechanical and consumer properties. To study crack formations in coal, an ultrasonic sounding method using shear polarized waves was proposed. Samples of three coal types (anthracite, lignite and hard coal) were tested. The research results show that, in contrast to the shear wave velocity, the shear wave amplitude is extremely sensitive to the formation of new cracks at the early stages of cyclic freezing-thawing. Tests also show an inverse correlation between coal compressive strength and its tendency to form cracks under temperature impacts; shear wave attenuation increases more sharply in high-rank coals after the first freezing cycle. Spectral analysis of the received signals also confirmed significant crack formation in anthracite after the first freeze-thaw cycle. The initial anisotropy was determined, and its decrease with an increase in the number of freezethaw cycles was shown. The data obtained forms an experimental basis for the development of new approaches to preserve coal consumer properties during storage and transportation under severe natural and climatic conditions.

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“…Thus, for the correct description of the deformation process of rocks and coals in particular, it is necessary to use the Mohr -Coulomb model. Significant number of works have been devoted to the identification of mechanical properties for coal rocks [5][6][7][8]. By its nature and process of formation, coal is an extremely complex material that has many peculiarities such as anisotropy, rheology, the presence of internal stresses, inhomogeneous properties, fracturing and many others.…”

Section: Introductionmentioning

confidence: 99%

Studying of Elastoplastic Properties of Coal Specimens Using Indentation Technique

Vatul’yan¹,

Lyapin²,

Kossovich³

2018

MMI

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A numerical study on elsatoplastic properties in problem of coals specimen nanoindentation by Berkovich pyramid is presented. The stress-strain state of specimen during indentation is calculated using finite element method including complex elastoplastic behaviour on the basis of Drucker-Prager model. The effective axisymmetrical indenter of cone shape is introduced and used for the simulation. The influence of basic geometrical and material parameters of the solid model on the indentation curve is studied. In addition, some new form of indentation curve approximation is proposed. For all the results calculated, the sets of approximation parameters are given. Using modern nanoindentation equipment the number of real experiments were performed and comparison with the mathematical model is presented.

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Mechanical Properties of Thin Films of Coals by Nanoindentation

Cited by 7 publications

References 8 publications

Mechanical, structural and scaling properties of coals: depth-sensing indentation studies

Mechanical, structural and scaling properties of coals: depth-sensing indentation studies

Experimental study of coal fracture dynamics under the influence of cyclic freezing–thawing using shear elastic waves

Studying of Elastoplastic Properties of Coal Specimens Using Indentation Technique

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