Browsing by Author "Yakovliev, Serhii O."

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    Development of Dynamic Integral Evaluation Method of Technical State of One-Section Electric Locomotive Body
    (НВП ПП «Технологічний Центр», м. Харків; Українська державна академія залізничного транспорту, м. Харків, 2020) Bannikov, Dmytro O.; Yakovliev, Serhii O.
    ENG: At present, one of the main problems arising from the long-term operation of one-section electric locomotives is the need to maintain their good technical condition. In this case, the determining aspect is often rapid identification of existing defects and damage to the main bearing structural elements of machine bodies, as well as preventing their development into more serious structural deviations. The aim of the study is to develop a specialized method that allows identifying defects of the main bearing structural elements of the bodies of one-section electric locomotives at the early stages of emergence and development. This method of dynamic integral evaluation is based on the analysis of partial dynamic spectrum of the electric locomotive. Based on the magnitude of the spectrum deviation relative to the theoretical one obtained from finite element modeling, it is possible to determine the approximate nature and location of damage, especially latent. The frequency spectrum of the main bearing structural elements of the bodies of one-section electric locomotives obtained in the course of the studies is rather dense and lies in the frequency range up to 20 Hz. The presence of damage reduces its value, and for the most common types of defects, this reduction is 25–30 %. The effectiveness of the practical application of the dynamic integral evaluation method is illustrated by the example of the DS3-008 machine. The method revealed hidden damage to one of the elements of the bearing frame of the front surface of the cab, which was not revealed during the standard maintenance procedure of the machine. The use of the method of dynamic integral evaluation of the technical condition of electric locomotives is quite versatile and can also be recommended for other units of railway rolling stock. In practice, the introduction of this approach will effectively prevent the development of emergencies.
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    Rational Compounds of Low-Strength Concrete with Improved Coefficient of Efficiency of Cement Use
    (Trans Tech Publications LTD, Switzerland, 2019) Netesa, Andrii M.; Netesa, Nikolay I.; Radkevych, Anatolii V.; Yakovliev, Serhii O.
    ENG: Abstract. The purpose of the research findings, given in article, is aimed to determine the rational compounds of concrete with an average cubic compressive strength less than 20 MPa with minimum required expenditures of cement. To reach the goal, mathematical planning of the experiment was used with variability of cement consumption from 90 to 190 kg / m3 in the compositions of the concrete mixture, and for the fine-grained filler from tails of processed ores, the consumption was like at 100 to 400 kg / m3. The result of processing experiments has shown us the dependences of the change in strength and coefficient of efficiency of the use of cement of the factors involved. Optimized values increase most intensively with minimum cement consumption and a change in the consumption of fine filler within the limits of the study. The highest coefficient of efficiency of use of cement is expressed by the ratio of the achieved strength per unit mass of used cement in the concrete mix and it was obtained at a cement consumption of 90 kg / m3 and a filler of 400 kg / m3. Using the obtained dependences of optimized values on the factors under study, the composition of concrete may be predicted with a strength up to 20 MPa with the required amount of filler.
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    Relationship Between Rolling and Slip Resistance in Rolling Bearings
    (Дніпропетровський національний університет залізничного транспорту імені академіка В. Лазаряна, Дніпропетровськ, 2016) Bondarenko, Lеоnid M.; Babyak, Mykola O.; Yakovliev, Serhii O.; Istin, S. О.; Moskalev G. Yu.
    ENG: Purpose. About one of the causes of slip rolling is known from the second half of the 19th century, it was believed that the slip resistance appears at the place of contact due to different speeds on the arc of contact. Only in the mid-20th century it was proved that this resistance is negligible in rolling resistance. However (for some unknown reason) it is ignored the fact that in practice in rolling bearings may rotate both the inner ring with a stationary outer one, and vice versa almost in equal relations. It is not taken into account the fact that the ball or roller in the rolling bearings runs the different distance along the roller path of the outer and inner bearing cages in one revolution. This fact is not taken into account in determining the calculated values for the friction coefficient of a rolling bearing reduced to the shaft. Therefore, the aim of this work is to determine the influence of path length on the track riding the outer and inner race of the bearing on the determination of the calculated value of the coefficient of friction of rolling bearings is given to the shaft. Methodology. The solution technique is based on the theory of plane motion of a rigid body, the theory of Hertzian contact deformation and the analytical dependencies for determination of coefficient of rolling friction. Findings. The obtained dependences on determination of rolling resistance of the balls or rollers along the bearing tracks of inner and outer bearing cages as well as path difference metering of the rolling on them allows to analytically obtain the rolling resistance and slipping for any size of bearings and different devices of bearing units. It is also possible at the design stage of rolling nodes to handle not only the design but also the content of the node. Originality. Using the analytical dependences for determination of the rolling resistance of bodies at point and line contacts, and also account for the difference in the path of the rolling ball or roller on the outer and inner cages of the bearing one can more accurately find the rolling resistance in the bearings. Practical value. The obtained dependences allow designing the bearing units with minimal energy consumption.