Browsing by Author "Malich, Mykola G."

Now showing 1 - 3 of 3
  • Thumbnail Image
    Item
    Improving a Technique to Calculate Strength of Cylindrical Rock Samples in Terms of Uniaxial Compression
    (Dnipro University of Technology, Dnipro, Ukraine, 2023) Vasyliev, Leonid; Malich, Mykola G.; Vasyliev, Dmytro; Katan, Volodymyr; Rizo, Zahar
    ENG: Purpose is to improve analytical technique to calculate strength of cylindrical rock samples taking into consideration standard horizontal stresses. Methods. Mathematical modeling of cylindrical rock sample breakage under the truncated-wedge destruction was performed taking into consideration the standard horizontal stresses using four experimental characteristics (i.e. k being shear strength; fс and μ being contact and internal friction coefficients; and Е being elasticity modulus) as well as comparing the design strength with experimental data obtained in the process of uniaxial compression. Findings. The technique makes it possible to identify both maximum strength and residual strength of cylindrical rock samples using four indicators of properties which can be simply defined by experiment. Comparison of the analytical strength limits and experimental data, obtained in terms of uniaxial compression, supports the idea of high efficiency of the proposed technique. Originality. For the first time, analytical modeling of cylindrical rock sample breakage has been performed in terms of the truncated-wedge destruction taking into consideration the standard horizontal stresses as well as contact and internal friction parameters. Practical implications. The technique advantage is to apply promptly the calculation results in the context of industrial enterprises since their environment helps apply simple procedures to define indices of physiсomechanical characteristics of rocks for determination of stability of underground structures and reduction of energy consumption while disintegrating in open pits and mining and processing complexes.
  • Thumbnail Image
    Item
    Modeling the Process of Disintegration of Solid materials by Asymmetric Loading in Crushing Machines in Order to Find Ways to Reduce Energy Costs
    (UNIVERSITAS Publishing, Petroșani, Romania, 2021) Vasiliev, L. M.; Vasiliev, D. L.; Malich, Mykola G.
    ENG: Subject of study. the processes of cracking and destruction of rocks under the action of the working bodies of machines for disintegration. Methodology. A complex method of generalizing the laws of the theory of elasticity and plasticity was used; theoretical and experimental confirmation of the regularities of the distribution of contact normal and tangential stresses, equations of the limiting state of materials based on the Coulomb strength criterion; slip line theory; comparison of theoretical results with experimental diagrams "normal stresslongitudinal deformation" of samples; facts and phenomena of destruction of rocks; generalization of the theoretical regularities arising from the power contact of the tool with the rock in crushers. Purpose. Reducing energy consumption and increasing the efficiency of rock disintegration by controlling its stress-strain state in crushers on the basis of mathematical modeling and using the established regularities of stresses and deformations in rocks when interacting with a working tool. Output. In the contact area, with an increase in the tangential load, the zone of uniform compression of the material decreases, the depth of the most stressed point approaches the contact surface. There is a significant zone of shear deformations, which are the decisive factor in crack initiation. The development of the crack in depth and complete destruction occurs along the shear lines. Such conditions of rock loading are observed in jaw crushers with complex jaw movement, in cone crushers, in roller crushers with different roll rotation speeds and correspond to the model of the most effective sliding compression. The creation of asymmetric loading conditions using the forces of contact friction, frictional and strength characteristics of the destroyed material can reduce the energy consumption of disintegration.
  • Thumbnail Image
    Item
    Spall Fracture Forms of High Rock Samples under Uniaxial Compression
    (IOP Publishing Ltd, 2023) Vasyliev, Leonid; Bulich, Yurii; Vasyliev, Dmytro; Malich, Mykola G.; Rizo, Zakhar; Polishchuk, Alla; Kress, Denis; Kuttiubaev, Aidar
    ENG: Prof. L.I. Baron identified five forms of destruction during uniaxial compression of samples of regular geometry of rocks including truncated wedge, wedge, diagonal, longitudinal, and explosive forms. All of them are commonly characterized by the destruction of samples in their central parts showing two or more cracks, while the trajectories of crack development align with the corner points of the samples. Recently, was unexpectedly discovered a spall fracture in the form of a single crack emerged from the side wall of the specimen and propagating into it under uniaxial compression. Based on the discovery, the method for creating stress-strain diagrams for high rock samples was developed using four rock properties such as rock shear resistance limit, contact friction ratio, internal friction ratio, and modulus of elasticity. The stress-strain diagram of the spall fracture of high samples is described by a descending curve, which is typical for the diagrams of fracture created by two adjacent cracks of regular geometry samples. The maximum stresses required for the destruction of high rock samples are lower than those for the destruction of regular geometry samples of rocks with similar physical and mechanical properties.