Wheelset Axle Research Articles

Influences of tram characteristics on wheel polygonal wear evolution

Out-of-round railway wheels continuously excite the vehicle-track system resulting in fluctuating contact forces, creepages and contact patch dimensions. Accompanied wear may influence the evolution of railway wheel polygonization significantly. Especially in curves with a small radius of curvature, which are typical for tramway networks, considerable wear originates due to high lateral creepages. Long-time wear development studies with dominant polygonal orders reveal that some wavelengths of the wheel enlarge rapidly, whereas others are nearly unaffected or even suppressed. Therefore, fundamental research on significant influences on wheel polygonal wear evolution is required. A representative generic system model of a two-axle tram bogie is set up, and a suitable wear model is implemented to study the polygonal wear evolution at trams. It has been found that structural modes can dominate wheel polygonal wear evolution. In particular, the compliance and interaction of the wheelset axle and the resilient wheel may be essential. Evolution tendency curves are presented, and influences on the wheel polygonization are discussed. Wheel–rail contact conditions and related creepage–creep force characteristics appear to be decisive for the evolution directions and evolution speeds.

The random dynamic performances of EMUs with polygonal damages

Polygonalization is a typical non-uniform wear phenomenon that affects the performance and comfort of the vehicle/track system. Therefore, the vehicle system performance could be strictly troubled by polygonal damage close to the wheel circumference at the wheel/rail contact. A 3D vehicle/track an EMU type train consisting of 8 coupled vehicles model has been established. The coupled model car body and bogie frame are considered rigid and integrated with the flexible wheelset, rail, and slab track to investigate the elastic deformation caused by the impact load induced by the wheel polygonalization. The flexible track can be incorporated into the multi-body vehicle model using the movable reference frame formulation. Uncertainty parameters are presented, such as passenger weight, wind force, coefficient friction, and suspension variation. The proposed research is validated based on the existing research work and shows excellent agreement. The simulation result deliberated the vertical wheel-rail force, wheelset acceleration, rail acceleration, rail displacement, and slab track acceleration. The results of this study show that as the wheel polygonal damage amplitude increase, the value of wheel/rail normal forces and the dynamic vibrational response of the wheelset axle increase. Additionally, polygonal wear-induced impact stresses may cause the wheelset axle to resonate. When wheel polygonal damage amplitude and uncertainty parameters are corporate into the system dynamics, the maximum magnitude of the wheelset, rail, and slab track acceleration increases. Besides, the train failure degree is comparable to the polygonised wheel harmonic order, defect parameters, and amplitude of out-of-roundness.

Mathematical substantiation of mine locomotive braking efficiency under pulsiting braking torque

Purpose. Determination of braking torque parameters that provide high braking performance of a mine locomotive by mathematical modeling of the braking of a mine locomotive by a disc brake that creates a pulsating braking torque. The methods. Forced vibrations of the elements of the wheel-motor unit (WMU) of a mine locomotive in the process of braking with a disc brake are studied by the methods of differential calculus and mathematical modeling. Integration of the system of differential equations is performed by the Runge-Kutt method. Findings. A comparative analysis of a mine locomotive braking by a disc brake, which creates a constant and pulsating sinusoidal braking torque with a different number of sinusoid periods per revolution of the wheel pair, is carried out. It has been proved that the pulsating sinusoidal braking moment generated on the axle of the wheel pair equal to the sum of the constant component and the amplitude of the oscillations of the variable component multiplied by the sine of the product of the number of sinusoid periods per revolution of the wheel pair by its angular coordinate provides higher braking characteristics than the constant braking moment. It is shown that pulsating braking torque reduces the braking time and braking distance of the mine locomotive. The values of the amplitude of oscillations, which depend on the average value of the braking torque, and the number of periods of the sinusoid per one revolution of the wheelset, at which the greatest effect is achieved, are determined. The originality. For the first time, a mathematical model has been developed for braking a mine locomotive by a disc brake, which creates a pulsating braking torque on the axle of the wheel pair, depending on its angular coordinate, taking into account the nonlinear dependence of the adhesion coefficient on relative slip, on the basis of which the efficiency of a disc brake with a multi-sector disc is shown in comparison with a disc brake with a homogeneous disk under various conditions of the rail track. Practical implementation. The research results make it possible to determine the parameters of a disc brake with a multi-sector disc located on the wheelset axle and on the engine shaft, which provide the highest braking efficiency.

A minimal model to study self-excited vibrations of a tram wheelset in curves with small radius of curvature

A wheelset of a rail vehicle may experience stability issues in curves with a small radius of curvature, which are typical for tramway networks. Accompanied self-excited vibrations of the wheelset might be a potential mechanism of adverse wheel polygonization, although a possible relationship between the two phenomena is not addressed here. A basic 2-DOF model, representing a wheelset with non-driven, independently rotating resilient wheels, has been derived from the analysis of simulation results with a more detailed system model to understand the reasons for a possibly unstable motion in a uniform curve. It has been found that a dominating motion in the regime with a negative gradient of the lateral creep force–creepage characteristics is necessary for possible self-excitation but is not sufficient for the considered parameter range. The combination and interaction of the lateral oscillations of the resilient wheel and laterally elastic wheelset axle is essential for amplification. Resulting stable limit cycles can be observed, and influences on corresponding amplitudes are discussed. The lateral flexibility of the wheelset axle appears as an important influence.

An analysis regarding train derailments caused by cracked wheelsets

The wheelset is a critical component of a bogie's rolling equipment, and safety requirements necessitate both static and fatigue analysis of wheelset axles. This paper proposes a comparative analysis of derailments and accidents caused by cracked wheelsets, a topic that is extensively debated among wheelset manufacturers and railway administrations. The central issue under discussion is whether the cause of wheelset axle cracking is attributed to failure in complying with wagon or locomotive loading requirements, leading to increased static stress, or to material fatigue. The answer to this debate may be found through technical expertise that involves analyzing the cross-section of the cracking, stress levels, and the impact of dynamic conditions.

Adaptive scale decomposition and weighted multikernel correntropy for wheelset axle box bearing diagnosis under impact interference

In this paper, a novel diagnosis method based on adaptive scale decomposition and weighted multikernel correntropy (ASD-WMKC) is developed to diagnose the faults of wheelset axle box bearing under strong wheel-rail impact interference and background noise. The ASD method is utilized to extract the complete fault characteristic signal of axle box bearing, in which the CHIMDO method is applied to restrict the overshoot and undershoot problems, an optimal shape approximation extension method is developed to suppress the end effects, and an adaptive decomposition scale construction method is proposed to overcome the mode mixing and splitting problems of decomposition. The WMKC is applied to enhance the weak fault characteristic signal and suppress the impact interferences, in which the multikernel correntropy combined with a 2D Gaussian kernel is utilized to overcome the defects of weak adaptability and poor anti-interference ability of correntropy, respectively. Simulation and application studies show that the proposed ASD-WMKC method outperforms the comparative methods and can extract the fault characteristic signal of axle box bearing with the highest completeness and SNR under strong wheel-rail impact interference and background noise.

Research on the Recognition Method of the Axle End Mark of a Train Wheelset Based on Machine Vision

Whether the wheelset of a high-speed train has defects such as cracks is very important to the safety of high-speed trains. Hence, the wheelset must be regularly inspected for flaws. For flaw detection of a wheelset, it is necessary to record the axle end information of the wheelset to correlate with the flaw detection results. To quickly and accurately identify the axle end mark of the wheelset, an automatic identification method based on machine vision is proposed. Our method identifies seven types of marks on the axle end, including the smelting number, steel grade number, unit number, sequence number, year and month, axle type mark, and the azimuth mark. Using the established automatic identification method of axle end marks, based on Retinex theory, an improved dual-core Laplacian combined with Gaussian filtering operation is proposed to solve the problem of the low contrast of the wheelset axle end image. An improved image tilt correction algorithm based on the combination of Hough circle detection and bilinear interpolation is proposed, which solves the angle tilt problem of the target character area of the axis end image. To handle the various types of axis end markers and the small amount of data, a retraining method to improve recognition accuracy is proposed. This method first uses Chi_Sim as the basic font for training and then retrains based on the trained font. Finally, Tesseract-OCR is used to improve the accuracy of the recognition results. Experiments are carried out by developing an automatic recognition program for axle end marks. The results show that the proposed method can effectively identify and classify seven-character types, and the recognition accuracy reaches 96.88% while the recognition time of each image is 5.88 s.

Axle Box Resonance Excitation Model Based on Wheelset Polygon and Its Resonance Characteristic Analysis in High‐Speed Train

AbstractBy grasping the vibration characteristics of the wheelset, the service state of the wheel can be reversely deduced. In this paper, the dynamic model of a rigid–flexible coupling vehicle system, considering wheelset flexibility and axle box flexibility, is established, and a novel resonance excitation loading method for axle box is proposed. Through this method, the vertical force of the wheel‐rail and the resonance response of the axle box vibration under different rigid–flexible combinations of wheelset axle box are obtained. The resonance response characteristics of the axle box of the wheelset and the main factors affecting the resonance characteristics are analyzed. Results show that the bending mode of the wheelset considerably affects the vibration characteristics of the axle box. The mass, the moment of inertia around the x‐axis, and the position of the center of gravity of the axle box also greatly affect the resonance characteristics of the wheel‐to‐axle box.

Study on the influence of wheel polygon on the vibration characteristics of bogie system

As one of the important core components of train running parts, the wheel rail related force will directly affect the vehicle running performance and passenger comfort. Take a high-speed train as the research object, the vehicle track coupling dynamic model is established. The influence of wheel polygon on the vibration characteristics of bogie system is analyzed through simulation. The results show that when the wheel polygon wear occurs, the effective value of lateral acceleration of polygonal wheel set axle box is about 18.9 % higher than that of normal wheel set axle box; at the same speed, with the increase of the wave depth of the wheel polygon, the effective values of the transverse and vertical acceleration of the axle box gradually increase; the effective value of axle box vertical vibration acceleration caused by wheel polygon with different amplitude increases first, then decreases and then increases with the change of vehicle speed. The effective value of axle box transverse and vertical acceleration caused by wheel polygon increases with the increase of wave depth or polygon order; the analysis shows that the polygonal wear of the wheel has a great impact on the vibration characteristics of the axle box and can cause the high-frequency vibration of the axle box.

Analiza wytrzymałościowa wózka kolei podwieszanej

The main topic of this article is the strength analysis of selected bogie components – the wheelset axle and the frame. Axle calculations were based on the analytical method and were conducted with different types of materials. The finite element method was used for verification of bogie frame construction and loads applied on the frame were calculated according to the PN-EN 13749 norm. The bogie is a part of suspended electric multiple unit which was main matter of authors’ master thesis: „The concept of suspended railway engine wagon”, conducted on Mechanical Engineering Faculty of Gdansk University of Technology.

КЛАССИФИКАЦИЯ МАГНИТНЫХ УСИЛИТЕЛЕЙ СЦЕПЛЕНИЯ И ПОИСК НОВЫХ РЕШЕНИЙ ТЯГОВОГО ПРИВОДА

The paper is devoted to search for new decisions for locomotive traction drive with a magnetic adhesion booster (MAB). In result of the analysis the authors have established that an optimal design for MABs that should increase axle load (magnetic boosters) and for MABs that should control an adhesion coefficient will differ. They have proposed a new classification that considers separation on magnetic boosters and devices for inertialess control of the adhesion coefficient and that covers new designs patented by the authors. It is established that a design of the MAB with inductor wiring located around a wheelset axle to the greatest extent complies requirements that are imposed to assemblies of locomotive underframe. The authors have suggested new designs for a traction drive with an arc-type-stator inductor electric motor that provides a possibility to place wiring of the MAB on a wheelset axle at a diameter of a wheel equal to 1050 mm, at rigid and elastic mounting of an electric traction motor and the MAB on a wheelset axle. The decisions proposed are protected by two patents, seven patents for utility models. Moreover, the authors have submitted an application for one patent.

Металлографическая экспертиза как обратная связь между качеством и производством продукции

Despite the increasing automation of the process of designing and manufacturing metal products, their failure remains a common phenomenon. The metallographic examination is appointed, which can only be carried out at a proper level by the specialized accredited organizations to identify the causes of such incidents. A metallographic examination is a tool that acts as feedback between the output quality of products and the entire chain of numerous operations during production. The purpose of this work is, using a practical example, to demonstrate the possibility and special significance of the conclusions of the metallographic examination for the development of the product manufacturing technology. Using the high-speed plasma spraying method, the authors applied the NiCrBSi coating to the surface of the locomotive wheel pair axle to increase its wear resistance. The life bench tests of the axle revealed the main fatigue crack, the tests were stopped, and the axle was artificially broken completely. The analysis of metal quality, including chemical composition, mechanical properties (strength, ductility, and impact hardness), microstructure, metal purity according to the non-metallic inclusions, and parameters of a surface layer hardened by rolling, showed its full compliance with the regulatory documentation. The thickness and hardness parameters of the NiCrBSi coating also corresponded to the declared ones. According to the fractographic analysis, the fatigue fracture was initiated at multiple points, which was a characteristic sign of a common objective reason for the insufficient strength of a product not associated with some random factor. The metallographic examination identified that the main reason for the failure of a wheelset axle is the coating's insufficient fatigue strength. The numerous fatigue microcracks that originated in the coating grew into the base metal and led to the fatigue macrocracks formation at different height levels. The merging of these cracks led to widespread fatigue fracture surface formation.

Energy Based Approach to Evaluate Self-Excited Vibrations of Wheelsets Caused by Adhesion Characteristics

Throughout the homologation process, especially in Germany, the torsional load acting on the wheelset due to drive train oscillations must be evaluated. The maximum values of these dynamic torsional moments are strongly influenced by the adhesion conditions in the wheel/rail contact and the slip velocity range between wheel and rail due to drive control dynamics. The adhesion conditions are hard to measure and to reproduce. Hence, it is time-consuming to prove that the measured dynamic moments cover the possible maximal values. The proposed energy method allows a proper prediction of maximum dynamic moments, assuming critical adhesion conditions and an appropriate drive train model. The criticality of the adhesion conditions is shown by measurements. The method is applied to different types of drive train. The predicted maximum values of the dynamic moments are compared with measurement results. During the drive control design phase, the energy method helps to determine a setting range of the slip velocity compatible with the wheelset axle strength. In the homologation process the method could replace measurements.

A Study of Improving Running Safety of a Railway Wagon with an Independently Rotating Wheel’s Flange

The main objective of this work is to study the possibilities of improving the running safety of a railway wagon with independently rotating wheels by changing their design symmetrically mounted on an axle. The article provides a discussion of the advantages and disadvantages of using the independently rotating wheels in a bogie of railway wagons. Their increasing tendency of derailment is described. The influence of a perspective constructive scheme (PKS) of railway wagon wheels in comparison with a traditional constructive scheme (TKS) on running safety due to the climbing of a wheel flange onto a rail is studied. This work introduces a conceptual proposition of a technical solution to railway wheel design as well as containing the results of both analytical calculations as well as the results of multibody simulations. A PKS wheel design for a railway wheel is designed that allows independent rotation of its tread surface and of a guiding surface (i.e., of a flange) to each other, which both are arranged symmetrically on a wheelset axle. It brings features of the distribution of friction forces generating in a flange contact when the wheel with a TKS and with PKS move on a rail. It is possible to conclude with the help of the obtained results that the use of wheels with the PKS is advisable for the reduction of the running resistance as well as for increasing the running safety of railway wagons.

Study on Wheel Polygonal Wear of Metro Trains Caused by Frictional Self-Excited Oscillation

This article aims to study the special phenomenon of wheel wear occurring on trains operating on a metro line in which the wheel polygonal wear rate of the right wheel is higher than that of the left wheel. Based on the perspective that frictional self-excited oscillation causes wheel polygonal wear, a flexible wheelset–rails system was built and, using complex feature value analysis, the unstable vibrations of this system were investigated. Moreover, the factors influencing wheel polygonal wear were studied. The simulation results show that when a subway train runs on a tightly curved track at 50 km/h, saturated creep forces upon two wheels of the leading wheelset are created. These forces can lead to unstable vibrations at frequencies of about 51, 60, and 69 Hz that are capable of inducing ninth-order wheel polygonal wear. Based on modal analysis and transient analysis, it is found that the unstable vibration intensity of the inner wheel–rail system is greater than that of the outer wheel–rail system, which leads to more uneven wear on the inner wheel. The length difference between the right and left curved tracks is the main reason for the different polygonal wear rates between the right and left wheels. The addition of damping material to the surface in the middle part of the wheelset axle has a small effect on the inhibition of wheel corrugation caused by the unstable vibrations. Fastener failure can lead to a stronger tendency toward wheel polygonal wear.

DETERMINATION AND ANALYSIS OF TECHNICAL PARAMETERS OF THE BENCH FOR RAILWAY WHEELS COMPLEX TESTS

Purpose. The purpose of the work is to determine and analyze the technical parameters of the bench for railway wheels complex tests, providing for the combination of fatigue and contact strength tests, their simultaneous performing on same test-bench. Methodology. Determination of the technical parameters of the test-bench was carried out based on comparing the characteristics of fatigue and contact strength tests of railway wheels. Requirements for fatigue tests and related equipment are determined based on an analysis of the current regulations and patent review. A model of the contact strength test-bench with the introduction of necessary changes in terms of ensuring the cyclicity of the working effort application was adopted as the basic model for the development of a complex test-bench. The criterion for the possibility of complex tests, involving the simultaneous testing of railway wheels for fatigue and contact strength, was the dependence of the test-bench roller diameter on the parameters of the tested wheel, the wheelset axle load, which includes the tested wheel and the wheel material endurance limit. Findings. The analysis of the obtained dependence showed that the roller diameter as a function of the load in the contact zone of the “wheel – roller” pair has second order discontinuity in the section where this load changes from the minimum to the maximum value. Analytical dependence is also presented and analyzed in graphical form. The generalization of the results obtained made it possible to conclude that it is impossible to carry out complex tests of railway wheels, which provide for the combination of fatigue strength tests with contact strength tests, subject to their simultaneous holding at the same test-bench. Originality. For the proposed scheme of the bench for complex tests of railway wheels, for the first time, we obtained the dependence linking the parameters of the test wheel, the parameters of the bench, the wheel pair axle load and the wheel material endurance limit. Practical value. The results obtained can be used as a basis for the development of new test-benches for railway wheels.

Dynamic interaction of a freight car body and a three-piece bogie during axle load increase

The article presents the results of theoretical studies of interaction process of a freight car body with a three-piece bogie, which are aimed at solving the relevant problem of increasing the permissible speeds at railways with 1520 mm track gauge under conditions of linear load increase on the wheel set axle. The purpose of the research was to propose such an approach to the study of interaction processes between rolling stock and track, taking into account the interaction model of neighbouring carriages in trains, which will allow more correctly take into account the dynamics of rolling stock and increase traffic safety. The oscillation frequencies of the body, bogie and wheel set are analysed in order to establish a possible resonance phenomenon. The article examines the longitudinal and transverse forces of pseudo-sliding (creeping) arising between the climbing wheel of the front bogie and the rails. The conducted studies can contribute to the replacement of 18-100 bogies with modernised three-piece bogies while maintaining the main most metal-consuming elements of the 18-100 model implementing some modernisation units. The results obtained will make it possible to revise the permissible vehicle speeds with an increased axle load.

Analytic Method for Vibration Analysis of Track Structure Induced by High-Speed Train

Nowadays, the increase in heavy freight rail transport and high-speed train (HST) operations has encouraged scientists to investigate the dynamic response of rail structures under moving load using analytically and numerically computational methods. In this study, to analyse vibration of rail structure, the rail has been modelled as continuous Euler-Bernoulli elastic beam system. The effects of some basic parameters such as track foundation elasticity modulus, rail stiffness, wheel set axle load and rail critical velocity which affect rail vibrations, on vibrations were examined in detail by considering different track foundation properties. The vibration wave amplitude increases as the train speed approaches the rail infrastructure critical speed.

Sensitivity study of vibration responses on vehicle body to typical damages of ballastless track structures

A method is proposed to investigate the sensitivity of the vibration responses on vehicle body to typical damages of ballastless track structures based on a coupled rigid vehicle body and flexible track model. Firstly, a coupled rigid vehicle body and flexible track model is established by combining SIMPACK and ANSYS software, and the reasonableness of the model is verified by coupling analysis. And then, the sensitivity of the vibration signals from different parts of the vehicle body to the typical damages of the ballastless track is investigated by simulating several typical damages on the flexible track model, and the feasibility of inversion of track damage based on the responses on vehicle body is investigated. The results show that a reasonable coupled vehicle-track model can be established by combining the finite element and multi-body dynamics method. The changes in the vibration responses of the vehicle body can reflect the typical track damages such as the loosening of rail fasteners, the debonding of CA mortar layer and cracks in track plate. The wheel-set axle box is the optimal location for installing vertical vibration sensors.

Wheel–rail impact loads and axle bending stress simulated for generic distributions and shapes of discrete wheel tread damage

Wheel–rail impact loads generated by discrete wheel tread irregularities may result in high dynamic bending stresses in the wheelset axle, leading to a decrease in component life and an elevated risk for fatigue failure. In this paper, a versatile and cost-efficient method to simulate the vertical dynamic interaction between a wheelset and railway track, accounting for generic distributions and shapes of wheel tread damage, is presented. The wheelset (comprising two wheels, axle and any attached equipment for braking and power transmission) and track with two discretely supported rails are described by three-dimensional finite element (FE) models. The coupling between the two wheel‒rail contacts (one on each wheel) via the wheelset axle and via the sleepers is considered. The simulation of dynamic vehicle–track interaction is carried out in the time domain using a convolution integral approach, while the non-linear wheel–rail normal contact is solved using Kalker's variational method. Wheelset designs that are non-symmetric with respect to the centre of the axle, track support conditions that are non-symmetric with respect to the centre of the track, as well as non-symmetric distributions of tread damage on the two wheels (or irregularities on the two rails) can be studied. Time-variant stresses are computed for the locations in the wheelset axle which are prone to fatigue. Based on Green's functions for stress established using the wheelset FE model, this is achieved in a post-processing step. An extensive parametric study has been performed where wheel–rail impact loads and axle stresses have been computed for different distributions and sizes of tread damage as well as for different train speeds.