Browsing by Author "Pentsak, Andrii Ya."
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Item Development of a Promising System for Diagnosing the Frogs of Railroad Switches Using the Transverse Profile Measurement Method(PC "Technology Center", Ukrainian State University of Railway Transport, Kharkov, 2018) Kovalchuk, Vitalii V.; Sysyn, Mykola P.; Hnativ, Yuriy M.; Bal, Olena M.; Parneta, Bohdan Z.; Pentsak, Andrii Ya.EN: We have developed a system for diagnosing the frogs of railroad switches, based on the application of modern microcontrollers of the type ESP with high technical characteristics and the simultaneous use of the information technology IoT (Internet of Things). The proposed system has advantages over mechanical systems in terms of the accuracy of data, their operational processing and submission to user in order to analyze technical condition of frogs at railroad switches. The results of measuring the transverse profile of frogs at railroad switches make it possible to take scientifically-substantiated decisions regarding the need for recovery repair of frogs by the method of surfacing and for control over gradual decrease in their carrying capacity, for establishing their actual technical condition and residual resource. We carried out experimental-theoretical research into longitudinal profile of frogs at railroad switches laid on the reinforced concrete bars. It was established as a result that after passing 50–65 million tons of cargo (that corresponds to the medium degree of wear) the trajectory takes the shape of a bump. We observe sharp hollows on the reinforced concrete base in the zone where a wheel rolls from a rail wing onto the core, characterized by significant total inclination. Subsequently, when the passed cargo increases, the number of sinusoidal irregularities grows. At wear close to maximal (80–95 million tons passed), the percentage of unfavorable trajectories (sinusoidal and hollows) grows; at low wear, they make up 49.8 %, at a wear of 5−6 mm and larger – 88.3 %. Sometimes there is a transformation of the sinusoidal irregularities into the wave-shaped ones. We have established characteristic motion trajectories of the center of mass of the wheel over the frog depending on the wear of rail wings and the core of a frog and the passed cargo. A mathematical model was constructed for predicting the wear of frog profile depending on the total weight of passed cargo.Item Evaluation of the Stressed-Strained State of Crossings of the 1/11 Type Turnouts by the Finite Element Method(ПП "Технологічний центр", Український державний університет залізничного транспорту, 2017) Kovalchuk, Vitalii V.; Bolzhelarskyi, Yaroslav V.; Parneta, Bohdan Z.; Pentsak, Andrii Ya.; Petrenko, Oleksii V.; Mudryy, Ihor B.EN: We carried out evaluation of the stressed-strained state of cross-ings of turnouts by the finite element method in the Ansys program-ming complex. It was established that under conditions of three-axial compression, at large stresses of vertical compression, the cracks of multi-cycle metal fatigue of the crossing develop. It was found that the development of defects by the code DS 14.1-14.2 on the rolling surface of the cast part of a wing rail and the crossing’s core occurs due to high contact stresses near the edge of the working face of a wing rail and the crossing’s core. They occur in this region in the form of cyclically repeated and sign-alternating normal and tangential stresses from cyclically recurring power im-pacts from the wheels of rolling stock of railroad transport. It was established that for the normal stresses, values that are maximal by absolute magnitude correspond to the moment when a wheel passes the estiamted cross section of the crossing. For the tangential stresses, on the contrary, at the moment when the wheel is over the estimated cross section, their magnitude is close to zero. The obtained results of the stressed-strained state of crossings are necessary for the optimal design of transverse and longitudinal profiles of the crossing. This will make it possible to extend operation life cycle of the crossings of turnouts and save state budget resources for their current maintenance and repair.Item Stability of the Railway Subgrade under Condition of Its Elements Damage and Severe Environment(Dnipro National University of Railway Transport named after Academician V. Lazaryan, 2019) Kovalchuk, Vitalii V.; Sysyn, Mykola P.; Nabochenko, Olga S.; Pentsak, Andrii Ya.; Voznyak, Oleg M.; Kinter, Stepan O.EN: Abstract. Investigation of damages of the subgrade slope in combination with its overwetting and rolling stock loading, which significantly affects safety traffic of the railway transport, has been carried out. The complex method of slope stability estimation of the subgrade is developed, which includes calculation of loads and vibration action of rolling stock on the main site of the subgrade, as well as the dynamic model of vibrations propagation in the body of the subgrade embankment and the model of plastic deformations accumulation. Dynamic and nonlinear plastic models are based on a finite-element model of the cross section of the subgrade. The plastic model takes into account the characteristics of soil strength of the subgrade, depending on the area of the vibration load impact. The developed method allows to carry out the estimation of external and internal factors impact on occurrence of subgrade destruction, which is of practical value for safety state estimation of the railway transport.Item The Study of Strength of Corrugated Metal Structures of Railroad Tracks(НПП ЧП «Технологический Центр», Харків, 2017) Kovalchuk, Vitalii V.; Marcul, Ruslan V.; Bal, Olena M.; Milyanych, Andriy R.; Pentsak, Andrii Ya.; Parneta, Bohdan Z.; Gajda, OleksiyEN: The analysis of the main defects of metal corrugated culverts of the railway, which arise as a result of operation, was conducted, and the problems of providing their durability and strength were highlighted. The problems of adaptation of foreign regulations for designing metal corrugated structures at Ukrainian railways and motor roads were analyzed, the results of experimental and theoretical calculations of bearing capacity of metal corrugated structures were presented. The MCS strength at boundary loading with the railway rolling stock was analyzed by the indicator of influence of corrugation (corrugation dimensions) and the characteristics of soils on their stressed-strained state. Calculation of equivalent forces was performed by the procedure of calculation of railway strength and stability using the finite-element method. The numerical calculation of the stressed-strained state of the MCS was obtained using the licensed software FEMAP with MSC NASTRAN. An analysis of multi-choice calculations of the strength of MCS, made of corrugated structure Multiplate MR150 with thickness of a corrugated sheet of 6 mm, with dimensions of corrugation waves of 150×50 mm, showed that its bearing capacity is provided at degrees of compaction of soil backfill from 0.9 to 1.0. Based on the obtained data, it was found that the direct cause of occurrence of residual deformation of metal corrugated pipe may be an increase in stresses in metal sheets of the pipe up to the values that exceed permissible stresses and as a result of local initiation of a plastic hinge. The condition of initiation of a plastic hinge, which takes place in the MCS arch, holds only if there is adverse simultaneous influence of two factors (causes): letting inequalities develop beyond permissible values without taking measures for its elimination and a decrease in the degree of compaction of backfill soil below 90 % (the second cause). In the absence of one of the causes, a plastic hinge might not emerge. In the joint effect of both causes, the first cause, the impact share of which is 42 %, prevails, whereas the share of the second cause is 22 %. The obtained results of the MCS bearing capacity are needed for optimal MCS designing, establishing causes of defect emergence, timely making relevant engineering decisions in order to increase the MCS bearing capacity and reasonable use of funds for the construction or reconstruction of existing transport facilities with the use of metal corrugated pipes. The results of the study may be used by engineers of Bridge testing stations of Ukrrailway and Ukravtodor and by designing organisations involved in designing metal corrugated structures of large diameters.Item Study of the Stress-Strain State in Defective Railway Reinforced-Concrete Pipes Restored with Corrugated Metal Structures(НПП ЧП «Технологический Центр», Харків, 2017) Kovalchuk, Vitalii V.; Marcul, Ruslan V.; Pentsak, Andrii Ya.; Parneta, Bohdan Z.; Gayda, O.; Braichenko, S.EN: Vertical and horizontal pressure forces on the reinforced-concrete pipes strengthened with a corrugated metal pipe under the influence of static and dynamic loads from the railway rolling stock were calculated. It was established that the value of both vertical and horizontal pressures on a reinforced-concrete pipe arising from the action of rolling stock decreases with an increase in the filling height because of energy dissipation in the depth of soil. For the filling height above the pipe 1 m, the value of vertical pressure from the load C14 was 7.568 kPa and horizontal pressure was 2.523 kPa. The respective figures for vertical and horizontal pressures were 5.957 kPa and 1.986 kPa for the filling height 2 m and 4.912 kPa and 1.637 kPa for the filling height 3 m. According to the results obtained for static and dynamic pressure forces, the stress-strain state of the pipe in interaction with the soil filling was calculated by the finite element method. The results of calculation of the stress-strain state of the composite pipe showed that the maximum stresses occurring in the vault of the repaired pipe did not exceed maximum permissible values. The magnitude of the stresses in the pipe vault was 0.024 MPa and strains measured 9.3·10–4 mm.Item Studying the Railroad Track Geometry Deterioration as a Result of an Uneven Subsidence of the Ballast Layer(НВП ПП «Технологічний Центр», Харьків, 2019) Nabochenko, Olga S.; Sysyn, Mykola P.; Kovalchuk, Vitalii V.; Kovalchuk, Yuri; Pentsak, Andrii Ya.; Braichenko, S.EN: A method for calculating impairment of the track geometry under influence of dynamic loads in the course of passing the track unevenness by the rolling stock was developed. The method takes into consideration interrelated short-term processes of dynamic interaction and long-term processes of subsidence of the ballast layer in a mutual influence on each other. Mathematical model of dynamic interaction of the track in the form of a planar three-layer continual beam system with a two-mass discrete system corresponding to the rolling stock is the basis of the first part of the method. This model makes it possible to simulate dynamic loads from individual sleepers to the ballast when the rolling stock passes geometric unevennesses and the track elasticity unevennesses.The second part of the method is based on the phenomenological mathematical model of accumulation of residual deformations formed using the results of laboratory studies of subsidence of individual sleepers in the ballast layer. Peculiarity of this model consists in taking into consideration not only uniform accumulation of residual subsidence from the passed tonnage but also presence of a plastic component of subsidence which depends on the maximum stresses in the history of ballast loading by each sleeper. A new theoretical mechanism of development of the track unevenness was proposed. It takes into consideration not only residual subsidences of the ballast layer but also appearance of gaps under sleepers resulting in a local change of the track elasticity. This mechanism enables taking into consideration the ambiguous influence of subsidences with occurrence of gaps under the sleepers. Subsidence causes an increase in dynamic loads on the track and the ballast layer on the one hand and onset of the gap causes a decrease in the track rigidity and corresponding reduction of dynamic loads on the other hand. Practical application of the developed method was demonstrated on an example of quantitative estimation of long-term uneven subsidences of the ballast layer when changing the sleeper diagram.Item Theoretical Study into Efficiency of the Improved Longitudinal Profile of Frogs at Railroad Switches(PC "Technology Center", Ukrainian State University of Railway Transport, Kharkov, 2018) Kovalchuk, Vitalii V.; Sysyn, Mykola P.; Sobolevska, Yuliia H.; Nabochenko, Olga S.; Parneta, Bohdan Z.; Pentsak, Andrii Ya.EN: We have developed a comprehensive method to prolong the time of operation of frogs at railroad switches, based on the consideration of a longitudinal profile of the frog, the magnitude of dynamic forces and normal stresses. We have improved a longitudinal profile of the frog, brand 1/11, project 1740, by the method of surfacing under field operation conditions. The slopes of a trajectory after the passage of an average statistical wheel over the proposed profile amount to 3.7 ‰ instead of 10 ‰ for a standard profile of the frog. It was established that increasing a load on the frog to 60 % at the expense of a deflection under the frog beam leads to the accelerated disarrangement of the frog, as a result of fatigue defects at the rolling surface, while the cost of frog operation in this case increases by five times. We modeled a dynamic interaction between the rolling stock and a standard, as well as the proposed, longitudinal profiles of frogs. Calculation of dynamic processes of the nonlinear interaction between the rolling stock and a standard profile of the frog and the profile restored by surfacing, showed that the magnitude of forces for the proposed frog at the motion speed of 150 km/h is 50 % lower compared with a standard longitudinal profile. At linear simulation of dynamic additions of forces, the magnitude of forces decreases for the proposed profile to 30 %. We employed a graphical method to calculate the magnitudes of axial inertia moments and the moments of resistance in the characteristic cross sections of the frog. The estimation of the stressed-strained state of the frog was performed using equations of five moments for a continuous beam on elastic point supports. It was established that stresses at the static calculation of the frog are low and are much less than the maximum permissible magnitude of stresses for a given grade of steel. Therefore, we can argue that the frog works under a load at the expense of existing reserve of strength.