INFLUENCE OF CROSSING WEAR ON ROLLING CONTACT FATIGUE DAMAGE OF FROG RAIL

The damage of the frog rail significantly affects the wear of the crossing rail and restricts the passing speed of the train. A geometric 3D modeling of the vehicle passing through the crossing center is particularly concerned with the cumulative wheel-rail contact of the traffic volume. The frog rail wear is simulated to obtain the dynamic change of the impact force of the wheel on the frog rail as the rail wears. By summarizing the existing experimental results of other scholars, it is clear that the important factors, that cause the damage of the frog rail, are vehicle load, friction coefficient, slip roll ratio and shear stress.  This paper combines the theoretical analysis of mechanics and 3D simulation to obtain the position change of the wheel-rail contact point with the wear of the frog rail, and finally compares it with the actual measurement results. It can more accurately predict the area where the maximum damage occurs after a certain amount of traffic for a certain fixed model, the change of wheel-rail contact point at frog rail is simulated with the wear of each component. Through theoretical analysis, the main factors determining frog rail damage were determined. Then evaluate the possible damage area of the frog track and control the prediction range to 5-10 cm, which reduces the detection time and cost. The worst state of distraction will be detected in time to facilitate replacement or polishing. Through further research in this area, the service life of the frog rail can be predicted

EVALUATION OF RAILWAY BALLAST LAYER CONSOLIDATION AFTER MAINTENANCE WORKS

The results of the study of the ballast layer consolidation after the work of ballast-tamping machines of different types are given in the article. The existing methods of determining the degree of consolidation of the ballast layer are analysed. The seismic method was improved by means of a complex dynamic and kinematic interpretation of the impulse response. For the dynamic interpretation with the use of statistical analysis, the features are selected so that they correspond to the degree of consolidation of the ballast layer. On the basis of researches, a device and software were developed that allow an automated evaluation of the ballast layer consolidation based on the kinematic and dynamic analysis of the measured impulse response. The measurements of the degree of the ballast layer consolidation after an operation of ballast-consolidation machines in different sequences allowed establishing the efficiency of the consolidation and the feasibility of the machines’ application

COMMON CROSSING CONDITION MONITORING WITH ON BOARD INERTIAL MEASUREMENTS

A railway turnout is an element of the railway infrastructure that influences the reliability of a railway traffic operation the most. The growing necessity for the reliability and availability in the railway transportation promotes a wide use of condition monitoring systems. These systems are typically based on the measurement of the dynamic response during operation. The inertial dynamic response measurement with on-board systems is the simplest and reliable way of monitoring the railway infrastructure. However, the new possibilities of condition monitoring are faced with new challenges of the measured information utilization. The paper deals with the condition monitoring of the most critical part of turnouts - the common crossing. The application of an on-board inertial measurement system ESAH-F for a crossing condition monitoring is presented and explained. The inertial measurements are characterized with the low correlation of maximal vertical accelerations to the lifetime. The data mining approach is used to recover the latent relations in the measurement’s information. An additional time domain and spectral feature sets are extracted from axle-box acceleration signals. The popular spectral kurtosis features are used additionally to the wavelet ones. The feature monotonicity ranking is carried out to select the most suited features for the condition indicator. The most significant features are fused in a one condition indicator with a principal component analysis. The proposed condition indicator delivers an almost two-time higher correlation to the lifetime as the maximal vertical accelerations. The regression analysis of the indicator to the lifetime with an exponential fit proves its good applicability for the crossing residual useful life prognosis

EXPERIMENTAL INVESTIGATION OF THE INFLUENCE OF TRAIN VELOCITY AND TRAVEL DIRECTION ON THE DYNAMIC BEHAVIOR OF STIFF COMMON CROSSINGS

Common crossing rails are subjected to a rapid deterioration of the rolling surface due to a dynamic loading of trains. The present study is devoted to an experimental study of the displacement and rail strain measurements in the common crossing. The experimental measurements were carried out for two stiff common crossings under the dynamic loading of high-speed train for the velocity range of 54-254 km/h. The results showed 2.5 times increase of the maximal displacements within the velocity range. The absence of the difference in the displacements between the trailing and the facing travel direction is explained with the relative displacement measurements between the rail and the sleeper and the different dynamic impact loading for the wing rail. The proposed model-based analysis of the absolute measurement of rail strain enables us to estimate the dynamic factor under the impact loading. The wing rail for trailing direction is almost twice as highly loaded as the frog rail for the facing direction. The maximal dynamic factor for the trailing direction shows almost no change for the velocities of more than 200 km/h

Common crossing fault prediction with track based inertial measurements: statistical vs. mechanical approach

Abstract The analysis of track based inertial measurements for common crossing fault detection and prediction is presented in the paper. The measurement of spatial acceleration in common crossing spike and impact position during overall lifecycle are studied regarding to rolling surface fatigue degradation. Two approaches for retrieving the relation of inertial parameters to common crossing lifetime are proposed. The first one is based on the statistical learning method - t-SNE algorithm that helps to find out similarities in measured dataset. The second one is a mechanical approach that handles the data with a fatigue and contact models. Both approaches allow the significant improvement of the common crossing fault detection as well as its early prediction

Extending service life of rails in the case of a rail head defect

Tračnice su tijekom svoje uporabe izložene procesima trošenja, korozije i kontaktnog zamora uslijed savijanja. Kao posljedica tih procesa, na tračnicama dolazi do raznih oštećenja i neispravnosti. Nastavak uporabljivosti tračnica ovisi o veličini, položaju i smjeru oštećenja. U ovom su radu izračunane maksimalno dopuštene vrijednosti veličine pukotine metodom konačnih elemenata. Smjer ravnine pukotine analiziran je u odnosu na ravninu kontaktne površine kotač-tračnica. Utemeljena je ovisnost faktora veličine naprezanja o površini pukotine. To omogućuje daljnju upotrebu oštećenih tračnica i siguran nastavak rada na željezničkim prugama sa slabijom aktivnošću.Rails are subjected to the processes of wear, corrosion and contact and bending fatigue during their lifecycle. As a result of these processes, various types of damage and defects are formed in rails. The residual life of rails depends on the size, position, and orientation of defects. Maximum permissible crack-size values are calculated in this paper using the finite element method. The crack plane orientation relative to the contact surface plane is analysed. The dependence of the stress intensity factor on the crack area is established. This allows continued use of defective rails and safe operation on low-activity railways

INVESTIGATION OF HEAT-AFFECTED ZONES OF THERMITE RAIL WELDINGS

The paper investigates the heat-affected zone (HAZ) of several rail joints executed by thermite rail welding (TW). The examined rail profile was 54E1 (UIC54). The rail steel categories were different: R260 and R400HT. The welding portions of the TWs fitted R350HT and R260 rail categories with normal welding gaps. The rail pieces were brand new, i.e., without any usage in the railway track. The authors executed Vickers-hardness tests (HV10) and material texture tests on the running surface of the rail head, as well as on slices cut from the rail head. The cutting was performed by the water jet method, five longitudinal direction slices with vertical cutting lines. The considered specimen lengths were 2×70 mm (i.e., 70 mm from the mid-point of the rail joint), however, the depths were 20 mm from the running surface. Therefore, the measuring spaces were 5 mm lengthwise and 2 mm in depth. The variation of the hardness values was determined considering the microstructures of the base steel material and the TW. For comparison, previously measured Elektrothermit SoW-5 and earlier own research were taken into consideration

INDICATORS FOR COMMON CROSSING STRUCTURAL HEALTH MONITORING WITH TRACK-SIDE INERTIAL MEASUREMENTS

This paper focuses on the experimental study of an alteration in the railway crossing dynamic response due to the rolling surface degradation during a crossing’s lifecycle. The maximal acceleration measured with the track-side measurement system as well as the impact position monitoring show no significant statistical relation to the rolling surface degradation. The additional spectral features are extracted from the acceleration measurements with a wavelet transform to improve the information usage. The reliable prediction of the railway crossing remaining useful life (RUL) demands the trustworthy indicators of structural health that systematically change during the lifecycle. The popular simple machine learning methods like principal component analysis and partial least square regression are used to retrieve two indicators from the experimental information. The feature ranking and selection are used to remove the redundant information and increase the relation of indicators to the lifetime

Оцінка несучої здатності металевої гофрованої конструкції типу Multiplate MP 150 при взаємодії із ґрунтом засипки

We estimated the stressed state of a railroad structure with a large cross section spanning more than 6 m, which is made from metallic corrugated sheets of the type Multiplate MP 150. The stressed-strained state of the corrugated structure was estimated depending on the residual deformation of vertical diameter of the pipe, the modulus of elasticity of backfill soil, and the degree of compaction. The study conducted has demonstrated that maximum stresses occur on the horizontal sides of a metallic pipe, and maximum deformations – in the pipe vault.It was established that an increase in the degree of compaction of backfill soil leads to a decrease in the stresses in a metallic pipe by almost half. The stresses grow much faster with an increase in irregularity on the railroad track. Numerical calculations have shown that the equivalent stresses exceed the permissible magnitude of 235 MPa when the degree of compaction of backfill soil is below 90 % and an operational irregularity on the track develops beyond the permissible magnitude.Operational observations have shown that the pipe is most vulnerable, in terms of resistance against the formation of a plastic hinge, in the initial period of operation when the backfill soil has not yet reached the standard compaction. At the initial stage of operation of a metallic corrugated pipe it is necessary to improve the level of technological control in order to timely detect railroad track’s irregularities that exceed the standards, and to eliminate them.Under normal operational conditions, a metallic corrugated structure has a rather large reserve of carrying capacity, which amounts to 80 %. However, these structures, despite their high initial strength margin, are very sensitive to an increase in external dynamic loads due to the occurrence of irregularity on the railroad track.Проведена оценка напряженного состояния железнодорожной конструкции типа Multiplate MP 150 с учетом степени уплотнения грунтовой засыпки. Установлено, что в начальный период эксплуатации металлическая гофрированная конструкция является неустойчивой против образования пластического шарнира, когда грунтовая засыпка еще не достигла нормативного степени уплотнения. С целью недопущения развития остаточных деформаций металлической гофрированной трубы необходим технический надзор за трубой в течение года эксплуатацииПроведено оцінку напруженого стану залізничної конструкції типу Multiplate MP 150 із врахуванням ступеню ущільнення грунтової засипки. Встановлено, що у початковий період експлуатації металева гофрована конструкція є нестійкою проти утворення пластичного шарніра, коли грунтова засипка ще не досягла нормативного ступеню ущільнення. З метою недопущення розвитку залишкових деформацій металевої гофрованої труби необхідний технічний нагляд за трубою протягом року експлуатаці

Розробка перспективної системи діагностики хрестовин стрілочних переводів методом вимірювання поперечного профілю

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.Разработана система инновационной диагностики крестовин стрелочных переводов. Проведены экспериментально-теоретические исследования продольного профиля крестовин стрелочных переводов железнодорожного пути, установленных на железобетонных брусьях. Установлены характерные траектории движения центра масс колеса по крестовине в зависимости от износа усовиков и сердечника крестовины. Разработана математическая модель прогнозирования износа профиля крестовин в зависимости от пропущенного тоннажаРозроблено систему інноваційної діагностики хрестовин стрілочних переводів. Проведено експериментально-теоретичні дослідження поздовжнього профілю хрестовин стрілочних переводів залізничної колії, укладених на залізобетонних брусах. Установлено характерні траєкторії руху центра мас колеса по хрестовині залежно від зносу вусовиків та осердя хрестовини. Розроблено математичну модель прогнозування зносу профілю хрестовин залежно від пропущеного тоннаж