Wheel Rail Research Articles

Condition-based monitoring of the rail wheel using logical analysis of data and ant colony optimization

PurposeIn this paper, a data mining approach is proposed for monitoring the conditions leading to a rail wheel high impact load. The proposed approach incorporates logical analysis of data (LAD) and ant colony optimization (ACO) algorithms in extracting patterns of high impact loads and normal loads from historical railway records. In addition, the patterns are employed in establishing a classification model used for classifying unseen observations. A case study representing real-world impact load data is presented to illustrate the impact of the proposed approach in improving railway services.Design/methodology/approachApplication of artificial intelligence and machine learning approaches becomes an essential tool in improving the performance of railway transportation systems. By using these approaches, the knowledge extracted from historical data can be employed in railway assets monitoring to maintain the assets in a reliable state and to improve the service provided by the railway network.FindingsResults achieved by the proposed approach provide a prognostic system used for monitoring the conditions surrounding rail wheels. Incorporating this prognostic system in surveilling the rail wheels indeed results in better railway services as trips with no-delay or no-failure can be realized. A comparative study is conducted to evaluate the performance of the proposed approach versus other classification algorithms. In addition to the highly interpretable results obtained by the generated patterns, the comparative study demonstrates that the proposed approach provides classification accuracy higher than other common machine learning classification algorithms.Originality/valueThe methodology followed in this research employs ACO algorithm as an artificial intelligent technique and LDA as a machine learning algorithm in analyzing wheel impact load alarm-collected datasets. This new methodology provided a promising classification model to predict future alarm and a prognostic system to guide the system while avoiding this alarm.

Vibration-based and computer vision-aided nondestructive health condition evaluation of rail track structures

In railway engineering, monitoring the health condition of rail track structures is crucial to prevent abnormal vibration issues of the wheel–rail system. To address the problem of low efficiency of traditional nondestructive testing methods, this work investigates the feasibility of the computer vision-aided health condition monitoring approach for track structures based on vibration signals. The proposed method eliminates the tedious and complicated data pre-processing including signal mapping and noise reduction, which can achieve robust signal description using numerous redundant features. First, the method converts the raw wheel–rail vibration signals directly into two-dimensional grayscale images, followed by image feature extraction using the FAST-Unoriented-SIFT algorithm. Subsequently, Visual Bag-of-Words (VBoW) model is established based on the image features, where the optimal parameter selection analysis is implemented based on fourfold cross-validation by considering both recognition accuracy and stability. Finally, the Euclidean distance between word frequency vectors of testing set and the codebook vectors of training set is compared to recognize the health condition of track structures. For the three health conditions of track structures analyzed in this paper, the overall recognition rate could reach 96.7%. The results demonstrate that the proposed method performs higher recognition accuracy and lower bias with strong time-varying and random vibration signals, which has promising application prospect in early-stage structural defect detection.

Wheel Rail Wear Prediction and Dynamic Performance Analysis of Linear Metro

In order to improve the safety of linear motor metro operation, the wheel rail wear prediction and dynamic performance analysis of linear motor metro are carried out. Firstly, the working principle and evolution process of the linear motor are analyzed, and the traveling wave magnetic field and slip ratio of the linear motor are calculated. Secondly, the friction principle between wheel and rail is analyzed, and the running data of wheel and rail area are collected by MiniProf series profiler. By calculating the wear energy flow density and wear mass flow density of wheel rail contact surface, the relationship between wear coefficient and energy flow density is obtained, and the wheel rail wear area is obtained, so as to complete the prediction of wheel rail wear. Finally, the running resistance of Metro is analyzed, including mechanical resistance and aerodynamic resistance. Combined with the calculation results of Metro kinetic energy and electromagnetic, the position of linear motor is obtained by modal superposition method in the elastic coordinate system, and the dynamic equation of linear motor Metro is constructed to complete the dynamic performance analysis of Metro. The experimental results show that this research method can accurately predict the wear of linear motor metro, and can study the running stability of Metro from the two aspects of horizontal stability and derailment coefficient.

Acoustic Radiation Study of a Box Girder Viaduct Considering the Frequency-Dependent Viscoelasticity of the Rail Pad

In order to investigate the mechanism of the frequency-dependent viscoelasticity of the rail pad on the acoustic radiation characteristics of a box girder viaduct, this study establishes a high-order model of its dynamic parameters to reveal the frequency-varying viscoelasticity of the rail pad, and establishes a vehicle–track–viaduct vertical coupling model. Finally, the acoustic radiation characteristics of a box girder viaduct are analyzed by combining the finite element method and the boundary element theory. The results show that the S-stiffness and D-stiffness of the rail pad increase with the increase in frequency, and the frequency sensitivity of the S-stiffness is greater than that of the D-stiffness. The high-order characterization model of the dynamic parameters of the rail pad has a good fitting effect. The main influence frequency band of the frequency variable viscoelasticity of the rail pad on the wheel–rail force and the equivalent discrete spring force of the sliding layer is 30–90 Hz, resulting in the shift of the dominant frequency to a high frequency by 4 Hz. We consider that the frequency-varying viscoelasticity of the rail pad will cause the dominant frequency of the acoustic pressure level of the field point to shift to a high frequency of 4–6 Hz, which has the greatest influence on the sound pressure level of each field point at the Peak Frequency Point of Insertion Loss (PFPIL), and the influence degree is consistent, resulting in the maximum value of the total sound pressure level of the surface field increasing by 4.1 dB. Without considering the frequency-varying viscoelasticity of the rail pad, the sound pressure level of each field point at 20–53 Hz will be overestimated and the sound pressure level of each field point in the 53–100 Hz frequency band will be underestimated. The panel sound power level contribution coefficient of the box girder is obviously different at different frequency points.

Study on the Factors Affecting the Wheel–Rail Lateral Impact of the Forepart of the Curved Switch Rail

In the switch rail section of a high-speed turnout, the wheel–rail lateral impact of the forepart of the curved switch rail is the most important factor affecting the passing performance. In order to reduce the lateral impact and improve the passing safety, a complete vehicle–track multi-body dynamics model is devised in this paper. The variation of the wheel–rail relationship when the train passes through is analyzed. The lateral force and derailment coefficient are calculated under different parameters, and the wear index is also calculated under some working conditions. The results show that properly reducing the lateral damping of the curved switch rail can effectively reduce the wheel–rail lateral force and derailment coefficient of this section, while keeping the track shape undamaged. The optimization of rail cant design plays an important role in alleviating lateral wheel–rail impact. Decreasing the height reduction of the switch rail is helpful to optimize the lateral force of the forepart of the curved switch rail. The selection of a suitable cutting mode for switch blade and reasonable control of the wheel–rail impact angle as well as passing speed have positive effects on controlling the lateral wheel–rail impact of the forepart of the curved switch rail.

Fragility analysis for vehicle derailment on railway bridges under earthquakes

With the rapid development of high-speed railways around the globe, the safety of vehicles running on bridges during earthquakes has been paid more attention to. In the design of railway bridges, in addition to ensuring the safety of the bridge structure in earthquake, the vehicle safety should also be ensured. Previous studies have focused on the detailed analysis of vehicle derailment on bridges, proposing complex numerical algorithms for wheel–rail contact analysis as well as for parametric analysis, but they are inconvenient for designers. Intensity measure (IM) used in performance-based earthquake engineering is introduced in this study. A method to evaluate the vehicle safety on bridges under earthquakes is proposed with respect to the optimal IM. Then, the vehicle derailment case of the Kumamoto earthquake in Japan verifies the decoupling method of vehicle–bridge interaction model. In the assessment of vehicle derailments, eight IMs are systematically compared: the IMs of bridge deck motion are generally better than those of ground motion; the variation coefficient of spectral intensity of the bridge deck is the smallest at different frequencies. Finally, the derailment fragility cloud map is presented to evaluate the vehicle safety on bridges during earthquakes.

New Tribological Aspects in the Micro-Areas of the Symmetric Rolling-Sliding Contact

The study of wear that occurs during operation in the wheel–rail assembly is a difficult process to analyze. The phenomena that accompany the wear process are extremely complex and involve many factors, which vary greatly over different periods of time and at different times of wheel–rail contact. Estimating the behavior of the system and its wear in operation is difficult to obtain. However, for common engineering applications, for which the determining factors, such as road profile, load, skid, speed and weather conditions, are known, useful results can be obtained by laboratory tests or by numerical simulation. The article aims to model the complex phenomena that take place in the rail wheel system, taking into account the impact that most essential operational factors have. For this, the Finite Element Method (FEM) is used, thus, trying to explain the wear mechanisms of the wheel–rail system. The obtained results are verified in the laboratory. The main observation in the paper refers to the fact that in the areas of maximum stress and deformation, cracks appear at the micro scale. FEM proved to be a method that can predict the appearance of these microcracks, the experimental results validating the numerical experiments. The research offers results that can prove to be of great importance in practice, for the analysis and improvement of railway safety.

Polygonal Wear Mechanism of High-Speed Train Wheels Based on Lateral Friction Self-Excited Vibration

This work details research on the formation mechanism of wheel polygonalization in high-speed trains and its effect factors by numerical modeling in order to prevent the increasingly prevalent problem of wheel polygonal wear. The lateral self-excited vibration model of a wheel was developed using the LuGre friction model and self-excited vibration theory. The properties of wheel self-excited vibration and the crucial condition of Hopf bifurcation were investigated; the process of wheel polygonal wear was simulated and the results were validated using field tracking data. The results demonstrated that periodic self-excited vibration generated by Hopf bifurcation is a required condition for polygonal wheel attrition at a given speed. The wheel’s polygonal wear has the following characteristics: “Constant speed—Self-excited—Fixed frequency—Divisible.” The order of the polygon is determined by the ratio of the wheel lateral self-excited vibration frequency to its rotational frequency. Wheel polygonal wear was caused by the vertical dynamic force of the wheel rail. The findings of the study can serve as a theoretical foundation for the prediction and reduction of wheel polygonal wear.

Dynamic Analysis of Wind–Vehicle–Bridge Systems: An Advanced Hybrid Method

To investigate the dynamics of the wind–vehicle–bridge (WVB) system in the multi-body dynamics framework, which avoids the large computation cost of programming the motion equation of complex vehicle models and improves the calculation efficiency, an advanced hybrid method is proposed to optimize the WVB system coupling vibration analysis model. The dummy body coupling (DBC) method is integrated to build the connection between the MBS and the FE model, which cannot change the mechanical characteristics of the MBS vehicle model and the bridge FE model. The proposed method makes full use of the high efficiency of the established structure modeling, the powerful wheel–rail analysis function, and vehicle modeling in the multi-body dynamics framework. The complex bridge is modeled by a number of elements to reflect the actual dynamic characteristics of structure, which cannot satisfy the requirement of calculation in the multi-body dynamics framework. Thus, to avoid forming the wheel–rail relationship function, the bridge modeling as a finite element model would be transferred into multi-body dynamics coupling model of the WVB system as a flexible body. The verification of the relationship among the sub-systems of the multi-body model of the WVB system is investigated by analysis of the wind–vehicle, wind–bridge, and vehicle–bridge sub-systems. Finally, a dynamic analysis of the WVB system based on the proposed method is carried out for a double-track railway continuous bridge, in which the effects of different vehicle speeds and the incoming wind directions are studied. The simulation of the WVB system by the hybrid method has a high computational efficiency and strong practicability.

Dynamic characteristics of wheel–rail collision vibration for high-speed train under crosswind

ABSTRACT This paper focuses on the dynamic characteristics of wheel–rail collision vibration for high-speed train under crosswind. The wind load model is established by using fast Fourier transform harmonic synthesis method and Davenport coherence function, the lateral displacement of wheelset of high-speed train under crosswind is calculated, the dynamic model of wheel–rail collision vibration system of high-speed train under crosswind is established. The effects of vibration frequency, wheel–rail clearance and lateral damping on the characteristics of wheel–rail lateral clearance impact vibration system of high-speed train are discussed. Numerical simulation results show that the impact velocity of wheelset collision on left and right rails increases with the increase of vibration frequency. When ω > 3.3, the system changes from chaos state to single period stable state through inverse doubling bifurcation; when b < 0.0033, it is in a chaos state, and with the increase of b, the inverse doubling bifurcation occurs until the hunting motion of the wheel–rail system is in a stable state; when , the system is in a stable single period operation state, and with the continuous increase of , it begins to have hop bifurcation, enters a multi-period and chaos state, and finally it is in a stable single period operation state.

Reducing wheel–rail surface damage by incorporating hydraulic damping in the Bogie primary suspension

ABSTRACT Wheel–rail surface damage in curves can be effectively reduced with a lower vehicle Primary Yaw Stiffness (PYS), while lowering PYS is detrimental to ride comfort and vehicle stability. This trade-off can be addressed by integrating hydraulic damping into primary suspension. However, work in this area only concentrated on comparing the effects of specific devices – the full potential of the hydraulic-damping-integrated primary suspension on combating the trade-off considering the whole parameter space is still unknown. Here we address this by making the following two contributions: (1) fully exploring the potential of hydraulic-damping-integrated primary suspension, on minimising the PYS while maintaining ride comfort; (2) systematically investigating the trade-off between the PYS reduction and suspension stroke requirement. Based on a case study using the Mark 4 Coach, this paper found that the optimal hydraulic-damping-integrated suspension can reduce PYS by 97% over the default without worsening comfort. This large reduction can potentially lead to a significant lifetime wheel-rail maintenance cost saving of approximately £42M for the fleet. If a larger suspension stroke is allowed, more cost saving can be achieved. These results provide motivation to conduct detailed engineering design studies to further examine the trade-off between financial benefits and design complexity.

Probabilistic Analysis of Lateral Wheel–Rail Forces

Probabilistic Analysis of Lateral Wheel–Rail Forces

A review of research on design theory and engineering practice of high-speed railway turnout

Abstract This paper systematically reviews the research progress, problems, specific countermeasures, and development trends of dynamic design theory as applied to high-speed railway turnouts. This includes wheel–rail contact solving, high-speed vehicle–turnout dynamic interaction simulation, analysis of long-term turnout performance deterioration, safety assessment of trains passing through the turnout, and the maintenance and management of turnout serviceability. High-speed turnouts still face severe technical challenges with regard to their acclimation to the future development of rail transit technology. Some of these challenges include the suitability of next-generation higher-speed turnouts to a complex environment, lifecycle design, optimization of wheel–rail matching and vehicle–turnout dynamic performance, real-time status capture and performance assessment, health management and damage prediction. It is now necessary to deepen the basic theoretical study of high-speed railway turnouts, and integrate cutting-edge techniques, such as advanced materials and manufacturing, intelligence and automation, big data and cloud computing, in an effort to enhance China’s capabilities for original innovation in high-speed railway turnout technology. By analysing the present situation in a problem-orientated manner, this paper aims to provide a new perspective, as well as some basic data for academic research into technological innovations for railway engineering.

Study of the Running-In Period in the Twin-Disc Wear Test Using Steel From a Class C Forged Railway Wheel

Abstract The railway wheels are one of the most critical components of the train and, any problem that may arise in the wheel, can generate numerous consequences. The ability to manage friction at the wheel–rail interface currently represents one of the greatest challenges and one of the most powerful tools in railway engineering. To define the efficiency of a product for friction control, retentivity tests are performed mainly by the suppliers. However, there is no strict standardization for the tribological test performance, and some critical issues like the influence of running-in period and the necessary superficial conditions of the rolling track to apply the friction control products are neglected. Thus, the objective of this work is to conduct dry twin-disc wear tests with different number of cycles to understand the running-in period and verify the tribosystem behavior. Starting from a rolling track with a polished surface, it was noted that the roughness increased rapidly and stabilized around 1500 cycles. The coefficient of traction (COT) increased at the beginning of the tests reaching the maximum at 750 cycles, reducing the value after that, and stabilizing at a value close to 0.4 with 5000 cycles. Thus, for twin-disc tests using these conditions, it is suggesting the application of friction control products from 5000 cycles because the COT and roughness would be stabilized.

Use of Surface Acoustic Waves for Crack Detection on Railway Track Components—Laboratory Tests

The present work investigates the technical feasibility of a condition monitoring setup aiming at the detection of gauge corner cracks (aka head checks) in pearlitic railway rails, using a wayside (i.e., stationary) setup with surface acoustic waves (SAW) as its detection principle. The experimental SAW setup consists of a pitch-catch setup using piezo transducers equipped with comb adaptors to excite and measure narrowband Rayleigh waves with a center frequency of 1 MHz. SAW experiments were performed on a rail subjected to cyclic loading in a 1:1 wheel–rail test rig yielding the specific rolling contact fatigue, i.e., head checks. Elastodynamic finite integration technique (EFIT) simulations were performed to analyze the surface and bulk wave propagation in the rail and to predict the signals at specific receiver positions. SAW transmission and reflection scenarios at cracks were analyzed numerically via modelled variations of gauge corner crack configurations according to number of cracks (0–3) and depth (0, 0.5 mm and 1 mm). The numerical and the experimental results each show a clear correlation between the appearance and intensity of head check damage and the wave attenuation in transmission mode.

An Algebraic Elimination by Substitution Algorithm for Vehicle–Bridge Interaction Problems

This paper proposes an algorithm to solve vehicle–bridge interaction (VBI) problems. It describes the VBI system in a linear second-order differential-algebraic equation (DAE) manner, incorporating the motions of both the vehicle and the bridge subsystems, together with the contact forces. On account of the conjugation between the VBI system’s motions and contact forces, the key feature of the proposed algorithm is to solve the DAE with the the algebraic method of elimination by substitution, avoiding the singularity of the differential operator. It enables a versatile and consensus solution scheme for different types of contact mechanisms, including the rigid contact model with constraints, the elastic contact model with the compliance method, and the creep tangential contact model, as well as different wheel–rail profiles. Combined with an appropriate numerical integration scheme, it allows an explicit expression of the contact forces, subsequently leading to the partitioned non-iterative analysis of the motions of both the vehicle and the bridge subsystems. In addition, by incorporating the dynamic condensation of wheels’ degrees of freedom into those of upper components in a matrix form, i.e. a reduced system approach, the proposed algorithm can avoid the numerical drift associated with the kinematic constraints on the acceleration level. To demonstrate the accuracy of the proposed approach, this study first examines a benchmark example of a single degree of freedom sprung mass model traversing a simply supported bridge. Further, it considers a more realistic problem of one and eight train vehicles crossing three three-span continuous bridges. The comparisons and the agreements with existing algorithms prove the accuracy and computational efficiency of the proposed analysis scheme.

Dynamic Response of Spatial Train-Track-Bridge Interaction System Due to Unsupported Track Using Virtual Work Principle

An improved spatial vehicle–track–bridge interaction system considering the unsupported track is proposed using the virtual work principle. When the track fails to be supported due to the defects under the track, the corresponding bridge–rail connection coupled matrix should be removed. Using the proposed dynamic model, a novel numerical analysis of the unilateral and bilateral unsupported sleepers in the bridge and the subgrade is carried out. The results indicate that the wheel–rail contact force changes dramatically when the vehicles pass through the unsupported track. The unsupported track has a little effect on the displacement of the bridge, but it increases the acceleration of the bridge. The displacement and acceleration of the track increase significantly with the expansion of the supported defects under the track and the increase of driving speed. For unilateral unsupported sleepers, the dynamic response on the unsupported side is slightly smaller than that of the bilateral unsupported sleeper, while the unsupported side has a limited effect on the other side of the normal support.

The influence of the lateral contact point trajectory and the rotation of the monoblock on the impact loads in railway turnouts

A new wheel–rail interaction model for the prediction of turnout impact forces is presented. Although the model is based on the classical “moving irregularity” approach, it is novel in the sense that it accounts for the lateral shift of the wheel–rail contact position during load transfer between the crossing nose and wing rail. This lateral shift increases the mobility of the track due to the rotational response of the monoblock under off-centred excitation. It is shown that the resulting stepwise variation of the wheel and track mobilities upon impact can profoundly influence the impact force time history. It is furthermore shown that these effects are particularly emphasized during the trailing move when the wheel impacts on the off-centred wing rail and much less during the facing move when the impact is absorbed by the crossing nose which is located in the plane of symmetry of the monoblock cross-section. Apart from the stepwise shift upon load transfer the lateral wheel–rail contact point position varies continuously along the longitudinal coordinate of the turnout. Simulations show that these continuous variations have a negligible influence on the impact force time histories and that a simplified model with constant shift gives satisfactory results. A comparison of the calculated crossing nose and wing rail accelerations shows encouraging agreement with field measurements. It is concluded that omission of the rotation leads to an overestimate of the track vibrations. Especially for the trailing move, this overestimate becomes substantial for frequencies above 100Hz.

600 km/h moving model rig for high-speed train aerodynamics

A maglev train with a speed of 600 km/h or higher can fill the speed gap between civil aircrafts and wheel rail trains to alleviate the contradiction between the existing transportation demand and actual transport capacity. However, the aerodynamic problems arising due to trains running at a higher speed threaten their safety and fuel efficiency. Therefore, we developed a newly moving model rig with a maximum speed of 680 km/h to evaluate aerodynamic performance of trains, thus determining the range of the aerodynamic design parameters. In the present work, a launch system with a mechanical efficiency of 68.1% was developed, and a structure of brake shoes with front and rear overlapping was designed to increase the friction. Additionally, a device to suppress the pressure disturbances generated by the compressed air, as well as a double track with the function of continuously adjusting the line spacing, were adopted. In repetitive experiments, the time histories of pressure curves for the same measuring point are in good agreement. Meanwhile, the moving model test and full-scale experimental result of maglev trains passing each other in open air are compared, with an error less than 4.6%, proving the repeatability and rationality of the proposed moving-model.

Nonlinear effects of a new mesh-type rail pad on the coupled vehicle-slab track dynamics system under extremely cold environment

Nonlinear dynamic behavior of a new mesh-type rail pad on the vehicle-slab track coupled system is investigated considering the influences of frequency and amplitude dependence in extremely cold environment. The frequency dependence of the new mesh-type rail pad is modeled by a fractional derivative viscoelastic element while a frictional component considers the amplitude dependence. Laboratory tests are performed to investigate the frequency and amplitude dependent performance of the rail pad and to determine key model parameters. Temperature factor and Mooney-Rivlin strain energy density are also introduced to simulate the mechanical properties of the rubber material of rail pad in low temperature environments. Further, the proposed nonlinear model for the rail pad is implemented in a coupled vehicle-slab track dynamics model to investigate the complicated nonlinear effects of the rail pad due to the dependence of the temperature, amplitude and frequency. The analysis indicates that the dynamic stiffness and damping of the mesh-type rail pads increase with the frequency increases. The proposed model for the mesh-type rail pad enables a more accurate dynamic simulation of vehicle-slab track system in extremely cold environment than the traditional Kelvin-Voigt model which overestimates the wheel rail force, rail vibration acceleration and other indicators at 3.15 Hz–40 Hz and 250 Hz–500 Hz, while underestimates these indicators at 50 Hz–125 Hz.