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Date submitted2022-05-25
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Date accepted2023-02-02
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Date published2023-08-28
Evaluation of the shear strength of rocks by cracks based on the results of testing samples with spherical indentors
Experimental data on the relationship of the residual shear strength of rocks in closed cracks with the functional characteristics of intact rocks – the tensile and compressive components of adhesion, the roughness of the crack surfaces, and the level of normal stresses are presented. A unified integrated approach determines the shear strength of intact and destroyed rocks, the residual shear strength of closed rough cracks has been developed. The approach provides for the selection of stress intervals corresponding to different types of fracture, for each of which a strength criterion is proposed, expressed in terms of functional characteristics of intact rock. An express method for estimating the residual shear strength of rocks by cracks with a rough surface has been developed, in which an improved method of loading samples with spherical indentors is used as a basic test method. The express method implements the transition from the data of mechanical tests of samples with spherical indentors to the shear strength indicators for cracks in the rock mass, taking into account the level of normal stresses and the roughness of the crack surfaces measured in field conditions. In this case the roughness scale developed by Barton is used. The express method is informative and available in the fieldwork.
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Date submitted2017-09-11
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Date accepted2017-10-30
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Date published2018-02-22
Provision of adhesion strength of gas-thermal coatings on piston rings of quarry transport engines
- Authors:
- Yu. Olt
- V. V. Maksarov
- V. A. Krasnyi
The main trend in the development of modern diesel engine manufacturign is the creation of high-powered, reliable and economical internal combustion engines (ICE), which are widely used in various industries, including mining machinery. The application of the methods of gas-thermal and gas-plasma coating for obtaining wear-resistant layers on piston rings for large internal combustion engines of quarry transport – diesel locomotives and dump trucks- is considered. It is shown that the abrasive-jet machining of base coat is widely used as a preparatory operation before coating process, and the roughness of the working surface of the rings after abrasive-jet machining has a significant impact on the adhesion strength of the coating with the base material. The selection of the surface roughness and the conditions of abrasive-jet machining for increasing the coating adhesion strength to the base coat significantly determines both the thickness of the coating and the reliability of the part itself. The aim of the paper is to investigate the dependence of the adhesion strength of a gas-thermal wear-resistant coating of piston rings of large engines of quarry transport, including dump trucks and diesel locomotives, from the roughness of the working surface after abrasive-jet machining, which in turn depends on its modes (distance to the nozzle exit section, the number of passes, the working air pressure, the shot change rate). The working surface adhesion strength of piston rings with diameter of 210 mm coated with molybdenum and steel wire composition was investigated by the twisting angle at which the coating peeled. It is shown that the roughness providing a twist angle greater than 35° should be more than 22 μm, which does not cause coating peeling off. Modes of abrasive-jet machining providing the specified values of roughness: working air pressure is 0.4 MPa, distance to the nozzle exit section is 110 mm, the number of passes is 2, and the shot changes after processing 40 mandrels.
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Date submitted2015-08-18
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Date accepted2015-10-09
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Date published2016-04-22
Analysis of charge space distribution influence on electric adhesion forces
- Authors:
- N. S. Pshchelko
Modeling ideas of physical and chemical processes when using an anodic bonding for materials connection are developed. The kinetics of a charge accumulation in an electrode region in a dielectric is considered. The thickness of a charge layer, electric fields strength and value of the ponderomotive pressure providing connection of materials are calculated. It is shown that the necessary ponderomotive pressure resulting in a dielectric-to-conductor seal is normally about ten megapascal and the time required is about ten minutes. The appearance of great pulling electric fields at anodic bonding process with a conductor surface to dielectric turns out to be possible due to the interlayer polarization developing in dielectric under the action of electric voltage. This results in a negative charge accumulation in a layer of small thickness beside anode. Thus applied electric voltage is distributed not through the whole thickness of a dielectric, but in fact is applied to a narrow area of the three-dimensional charge be-side anode. Arising strong electric fields force the connected materials to unite. The physical and mathematical models for force characteristics of non-uniform electric field are developed. Dependences of parameters of anodic bonding junction on time are considered. The expressions allowing to choose well-founded time of formation of anodic bonding junction are obtained, intensity of electrostatic fields and forces in dynamics is calculated. Research of a charge intermittence influence on electrostatic field strength has shown a considerable differences on small distances to the charged surface between carried out and traditional ways of calculation.
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Date submitted2014-12-29
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Date accepted2015-02-15
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Date published2015-12-25
A study of distillates physical and chemical properties and residues after thermodestructive and catalytic processes and their application in the mining industry
- Authors:
- N. K. Kondrasheva
- O. V. Zyrianova
When transporting overburden rocks in a cold season, the lower layer of materials freezes to working surfaces of transport equipment, and at long transportations – congeals under its own weight. As a result, up to 50 % of rock remains in the vehicle, while the unloaded part represents indiscreete frozen mass. It considerably complicates the process of unloading transport and leads to increased labor and financial expenses. A rational and effective remedy for these problems is transport equipment and bulk material processing with chemical agents of oil and petrochemical origin – mixtures of distillate and bottom frations obtained as a result of thermodestructive processes during petroleum feedstock manufacturing. The article presents data on the quality of distillates and residual products of oil recycling, which are used as initial components for producing preventive drugs, which are used to prevent sticking and freezing of overburden rocks during transportation and storage in the cold time of year, as well as drugs used for pit roads treatment in surface mining operations. Optimal component compositions of new petrochemicals are developed, and the physical and chemical properties of the received test samples have been studied.
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Date submitted2009-09-08
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Date accepted2009-11-18
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Date published2010-06-25
Anodic bonding method for adhesion enhancement of conducting films to dielectric substrates
- Authors:
- A. G. Syrkov
- N. S. Pshchelko
The appearance of great pulling electric fields at anodic bonding process with a conductor surface to ionic dielectric turns out to be possible due to the interlayer polarization developing in dielectric under the action of electric voltage. This results in a negative charge accumulation in a layer of small thickness beside anode. Thus applied electric voltage is distributed not through the whole thickness of a dielectric, but in fact is applied to a narrow area of the three-dimensional charge beside anode. Arising strong electric fields force the connected materials to unite. In the present work it is shown that use of the discussed technology allows to increase considerably adhesion of conducting films to dielectric substrates both in the process of their deposition and after it.