Vasyliev D.L., Livak O.V., Kravets V.I., Gankevich V.F. To estimation of temperature fluctuations in diamond grains when drilling with diamond bits

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Parent Category: Geo-Technical Mechanics, 2021

Category: Geo-Technical Mechanics, 2021, Issue 157

Geoteh. meh. 2021, 157, 172-179

https://doi.org/10.15407/geotm2021.157.172

 

TO ESTIMATION OF TEMPERATURE FLUCTUATIONS IN DIAMOND GRAINS WHEN DRILLING WITH DIAMOND BITS

¹Vasyliev D.L., ²Livak O.V., ²Kravets V.I., ³Gankevich V.F.

¹Institute of Geotechnical Mechanics named by N. Poljakov of National Academy of Sciences of Ukraine, ²Ukrainian State University of Chemical Technology, ³National Technical University “Dnipro Polytechnic”

UDC 622.026.7.3.

Language: Ukrainian

Abstract. If we consider the interacting pair: the matrix of a diamond crown, reinforced with protruding diamonds and rock, as a kind of system, then in the process of friction of the matrix against the bottom hole, external mechanical energy is converted into the energy of the heat and matter flows. The main concentration of the flows occurs in places where diamonds protrude above the matrix and take on an additional load. The rubbing system tries to smoothing itself by concentrating pressure and temperature on the diamonds. Diamonds, due to their higher hardness than the destructible medium, are pressed into the rock and destroy it. Since the process of cutting rocks is intermittent, the concentration of energy on diamonds occurs periodically, in the form of “flashes”. Each such “flash” is accompanied by a short-term increase in temperature in the contact zone (temperature fluctuation) and the spalling of a microparticle of the rock. 
In this work, from the standpoint of thermoelastic instability, the issue of temperature microflashes in single diamonds during the interaction of rough surfaces of the matrix of the diamond crown and the bottom of the borehole is considered, in order to take this factor into account in the mechanism of wear of the diamond of the drill bit. The value of temperature fluctuations on the surface of cutting diamonds was estimated and the size of the flash zone was determined.
It is shown that temperature flashes of 400 (С < T* < 3650 (С are observed when drilling granite with a diamond crown on the diamond surface in an area of 5.8(10‑5 m, therefore, the presence of such “microflashes” on the diamond surface in a very small area in the process of interaction with the rock can lead to graphitization of the diamond in this place and separation from the surface of the grain. Such a mechanism should play a certain role in the wear and destruction of diamond surface areas during drilling.
The magnitude of temperature fluctuations depends on the physical and mechanical properties of the contacting pair: diamond – rock, operating parameters of the tool and the nature of the placement of diamonds in the crown matrix.
In this regard, the study of the assessment of temperature fluctuations in diamond grains when drilling with diamond bits may be of practical interest.
Keywords: rock, thermal stresses, intensive cooling, macro- and microcrack system.

REFERENCES:

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About the authors:

Vasyliev Dmytro Leonidovych, Doctor of Technical Sciences (D.Sc.), Senior Researcher, Senior Researcher in Department of Elastomeric Component Mechanics in Mining Machines, Institute of Geotechnical Mechanics named by N. Poljakov of National Academy of Science of Ukraine, Dnipro, Ukraine

Livak Oksana Viktorivna, Master of Science, Assistant of the Department of Material Science, Ukrainian State University of Chemical Technology, Dnipro, Ukraine,  This email address is being protected from spambots. You need JavaScript enabled to view it.

Kravets Vasyl Ivanovych, Candidate of Technical Sciences (Ph.D.), Associate Professor in the Department of Material Science, Ukrainian State University of Chemical Technology, Dnipro, Ukraine

Gankevych Valentyn Feodosiiovych, Candidate of Technical Sciences (Ph.D.), Associate Professor in the Department of Mining Machines, National Technical University “Dnipro Polytechnic”, Dniprо, Ukraine,  This email address is being protected from spambots. You need JavaScript enabled to view it.

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