Flange Contact Research Articles

Determining the influence of wheelset arrangement in the model 18-100 bogies on the level of steering efforts in the wheel-rail flange contacts

The object of this study is the process of directing the bogies of model 18-100 freight cars along a rail track, in particular, along curved sections of the track. The task to be solved was to determine the influence of wheelset arrangement on the level of steering forces in the flange contacts. A calculation diagram and a mathematical model of fitting the bogie into the curved section of the track have been built. The bogie loading scheme by external forces, including lateral rocking forces acting on the car in a curve, has been refined. In this case, the method of pseudo-statics of the mechanical system, which is a system of nonlinear algebraic equations, was applied. The calculation module Given-Find in the Mathcad software package (USA) was used to solve the mathematical model. It was established that the misalignment of wheelsets in the frames of model 18-100 bogies was of an accumulative nature. At the maximum operating angles of misalignment of wheelsets, the lateral steering forces in the flange contacts increase by 40–60 % compared to the rated setting. These angles can be up to 0.015 rad (0.85 degrees). The field of practical application of the results is railroad transportation, in particular, the system of maintenance and repair of freight cars on bogies of the 18-100 model. At the same time, the condition for the practical application of the research results is the expediency of introducing into the maintenance system the technological operation of controlling the deviation of wheelset arrangement in the bogie relative to the rated one. The current study will contribute to the construction of a measuring system for monitoring the deviation of wheelset arrangement in the bogie relative to the rated one. This proves the expediency of introducing into the trolley maintenance system the technological operation of controlling the deviation of wheelsets and designing a device for monitoring this parameter

Investigation of curve minimum radius in heavy-haul railway to improve wheel wear evolution and wheel-rail contact geometry

To determine the minimum and reasonable radius of horizontal curve for reducing wheel wear in heavy-haul railway design, a HXD locomotive with the wheel arrangement of C0-C0 is taken as the research object. Both the corresponding locomotive dynamic model and wheel wear model are established. Based on the measured wear data in a specific line, the simulation model is verified with the prediction error of wheel wear depth below 0.5 mm in general. The wheel wear evolution rules in 400∼1000m radius curves are studied and compared. The results indicate that, the wheel wear is large and sensitive to curve radius within 400∼600 m. The larger radius curve will be helpful to reduce wheel flange contact and wheel wear. For curve radius increasing from 600m to 1000m, the wheel average wear reduces slowly. Especially for curve radius below around 740 m, the wheel flange wear will be predominant. For radius above 740m, the wheel tread wear becomes the main wear form and the wheel flange wear can be reduced significantly. The increase of curve radius will also improve the wheel-rail equivalent conicity. If the minimum curve radius is set as 800m, the equivalent conicity difference between new wheelset and 1st ∼ 3rd worn wheelset can be kept below 21%, 52% and 9% respectively. In this case, the equivalent conicity is closest to the initial state and reaches a steady state, which will not change significantly with the radius further increasing. Viewed from the aspects of reducing wheel wear, avoiding wheel flange contact and keeping conicity stable simultaneously, the minimum radius of horizontal curve should be limited to 800 m. The research results validate the minimum curve radius suggested in Code for Design of Heavy-haul Railway in China, and provide a scientific explanation for the determination of this value.

An Optimization Method of Assembly Process for Bolt Flange Connection Structure with Manufacturing Characteristics

Threaded connections are a common method in precision assembly. As threaded connections in precision assembly are rigid, the morphology of contact surfaces and their stress states significantly influence the alignment accuracy and stability of the connection structure. Establishing a quantified intelligent decision-making approach from connection performance requirements to connection assembly is of crucial significance for enhancing product performance. In this paper, a precision measuring machine is used to acquire point cloud data of the circular contact surfaces of two flanges. Subsequently, a NURBS surface modeling method is employed to construct a three-dimensional representation of the flange contact surface with manufacturing characteristics. The attitude vectors of the connection structures on both sides of the flange contact surface are established. A multi-objective optimization method is employed to adjust the installation angles, optimizing the combined state of contact status and connection attitude to achieve the optimal configuration. The contact area is divided based on bolt positions and quantities, and an optimized pretension force for bolts within each area is determined using a simplified contact model for that region. ABAQUS simulation software is used to numerically solve the bolt flange connection structure before and after optimization under long-term temperature cycles. Through simulation, the positional accuracy of the bolt flange connection structure related to assembly is improved by 52.7% compared to the pre-optimized state, and the long-term positional accuracy is enhanced by 23.5%.

Effect of different roller end-flange constructions on the fatigue life of the cylindrical roller bearings: A novel flange deformation formula

This paper performs the fatigue life analysis of the radial Cylindrical Roller Bearings (CRBs) with consideration of various roller end-flange shapes such as toroidal-toroidal, spherical-toroidal, and spherical-conical. A novel formula for each flange contact deformation in cylindrical roller bearing with different roller end-flange geometry including toroidal geometry is developed. Inner ring misalignment angle and radial deflection results obtained from the present study are verified with numerical and experimental results from the literature. The results approach to that of literature when the flange is changed from toroidal geometry to conical geometry. Using formulas developed in the present study, the effect of various roller end-flange geometries on the bearing life is investigated for different external loadings. It is observed that the bearing life increases when the roller end and flange are changed to toroidal geometry.

Bifurcation and stability analysis of a high-speed rail vehicle with active yaw dampers

Active yaw dampers (AYDs) show promise in addressing the carbody and bogie hunting issues of high-speed rail vehicles. However, the bifurcation behaviour under active control and the control law for hunting instability still require investigation. This study presents a comprehensive description of the linear control law, which can be simplified to various schemes, including skyhook damping, groundhook stiffness, modal, and blended schemes. The bifurcation behaviour under active control was analysed using a simplified lateral-dynamics-intended seven DOFs vehicle model and verified using a 3D full DOFs model in SIMPACK. Besides the well-known Hopf bifurcation, results also revealed a branching point (BP) and two new stable asymmetric equilibria. Although the asymmetric equilibria born through BP are stable, BP bifurcation should still be avoided for wheel flange contact and derailment concerns. Possible control laws are explored for two hunting scenarios: carbody hunting and bogie hunting. For carbody hunting cases, the control force can be either a linear function of bogie yaw displacement or a linear weighting function of bogie lateral and carbody roll velocity. The dominant frequency of the actuated force falls below 2 Hz, with a peak of 1.6 kN, and the allowable time delay is 70 ms. For bogie hunting cases, the control force can be a linear function of either bogie yaw displacement or velocity. In other words, both the groundhook stiffness and damping strategy are applicable. However, the actuated force contains several relatively high-frequency components (6∼13 Hz), which poses challenges to the control system and actuators, and the allowable time delay is relatively small.

Influence of Wheel-Rail Contact Algorithms on Running Safety Assessment of Trains under Earthquakes

Accurate running safety assessment of trains under earthquakes is crucial to ensuring the safety of line operation. Extreme contact behaviors such as wheel flange contact and wheel jump during earthquakes will directly affect the running safety of trains. To accurately simulate a wheel-rail extreme contact state, the calculation of the normal compression amount, the normal contact stiffness, and a number of contact points are crucial in wheel-rail space contact modeling. Hence, in order to clarify the applicable algorithms during earthquakes, this paper first introduces different algorithms in three aspects mentioned above. Taking a single CRH2 motor vehicle passing through a ballastless track structure under EI-Centro wave excitation as an example, a comparative analysis of wheel-rail contact dynamics and running safety was conducted. The results showed that adopting the normal compression algorithm based on vertical penetration and the consideration of only single-point contact will result in the maximum calculation error of wheel-rail contact force to reach 339.50% and 35.00%, respectively. This significantly affects the accuracy of train safety assessment, while using the empirical formula for wheel-rail normal contact stiffness has relatively less impact. To ensure the accuracy of running safety assessment of trains during an earthquake, it is recommended to adopt the normal compression algorithm based on normal penetration and consider the multi-point contact in wheel-rail contact modelling.

Theoretical and experimental studies on vibration characteristics of bolted joint multi-plate structures

The bolted joint multi-plate structures are widely used in practical engineering, but their theoretical dynamic model is hard to find in literature. The main purpose of this paper is to establish a general dynamic model of bolted joint multi-plate structures with flanges, and to investigate its vibration characteristics from both theoretical and experimental aspects. Both the flange effect and contact pressure distribution in the bolted joint affected region (BJAR) are considered. Artificial spring sets with variable stiffness are adopted to simulate the non-uniform distributed contact pressure in BJAR. The governing equations are derived based on the Kirchhoff plate theory and Euler-Bernoulli beam theory. The Chebyshev polynomials are used as admissible displacement functions. Then, the free vibration and forced vibration under base excitation are solved by means of the Rayleigh-Ritz method and Newmark-beta method, respectively. The experimental studies, including modal test and vibration response test, are conducted on a bolted joint two-plate specimen to verify the accuracy of the theoretical model. Results show that the present model is capable of realizing reliable vibration prediction and can be conveniently extended to the structure with an arbitrary number of plates and bolts. For the bolted structures, considering the pressure distribution in the connection interfaces can significantly improve the accuracy of theoretical results.

NFLUENCE OF DEVIATIONS IN THE POSITION OF WHEEL PAIRS IN A FREIGHT-CAR ON THE GUIDING FORCES

The article puts forward a hypothesis according to which the violation of the nominal setting of wheel pairs in railway rolling stock carts is the main reason for the increase in guiding forces in the wheel flange contacts of the wheels of freight cars with the rails. Increased loads in wheel flange contacts are the cause of a number of other negative phenomena: increased intensity of wear (undercutting) of wheel flange, increased wear of the side surfaces of rail heads, decrease in the coefficient of stability of wagons from derailment, etc. To test this hypothesis, a study was conducted to obtain dependencies, first of all, these are the characteristics of the influence of geometric deviations of the position of the wheel pairs in the cart on the level of guiding forces in the contacts of the wheels with the rails and the wear of the wheel flanges. The relevance of this study is confirmed by data on the catastrophic wear of rails and solid-rolled wheels of wagons. An analysis of statistical data oblique setting of wheel pairs in carts in plan due to running-in of side frames was made, which shows that in 80% of wagons these angles can be up to 0,015 rad (0,85 degrees). The formula for the critical derailment ratio of the frame force to the vertical load on the wheel has been clarified, in contrast to Nadal's formula, which additionally takes into account the deflection forces in the contact of the overlapping wheel.

Fast and Stable Iterative Algorithm for Searching Wheel–Rail Contact Point Based on Geometry Constraint Equations

Abstract This paper proposes a fast and stable iterative algorithm for wheel–rail contact geometry based on constraint equations, which can be implemented in dynamic wear simulations that real-time profile updating is needed. Further, critical factors that determine convergence and iteration stability are analyzed. A B-spline is adopted for wheel–rail profile modeling because it does not contribute to changes in the global shape of curves. It is found that the smoothness of the first and second derivative curves significantly affects the numerical stability of the Jacobian matrix, which determines the increments in iterations. Moreover, a damped Newton's iteration formula with a scaling factor of 0.5 is proposed considering the convergence rate and out-of-bound issues for the updated step. The influence of the initial iteration parameters on the convergence is studied using Newton fractals. The range within ±3 mm, centered on the target contact point, is found to be an unconditionally stable domain. The proposed method could achieve convergence within 10 and 30 steps under thread and flange contact conditions, respectively.

Investigation of the possible applications for microtextured rolling bearings

The application of microdimple-textured surfaces for rolling bearings is not very common but can be beneficial for various usage scenarios. In contrast to the applications for plain bearings or cylinder running surfaces, however, surface patterns for rolling bearings only offer advantages under certain conditions. For example, for use with start-stop cycles, in mixed lubrication conditions, or under sliding conditions in a bearing as well as on a roller—bearing flange contact, friction can be reduced with the targeted use of microtextures. The geometry of the microtextures must be chosen so that individual dimples fit in the contact area between the ball or roll and the bearing surface in order to act as a reservoir for the lubricant. First applications for microtextured angular contact ball bearings under oscillating movement conditions proved friction reducing effects under reciprocating motion. In this case the microtextures served as lubricant reservoirs. The idea is transferred to the sliding contact for tapered roller bearings; it is investigated whether the measured reductions in friction are due to the microtextures serving as lubricant reservoirs or whether there is even a positive hydrodynamic effect caused by the microtextures. By means of a calculation approach as well as some exemplary test rig measurements, the behavior for microtextured tapered roller bearings is investigated.

Double grazing bifurcations of the non-smooth railway wheelset systems

There are numerous non-smooth factors in railway vehicle systems, such as flange impact, dry friction, creep force, and so on. Such non-smooth factors heavily affect the dynamical behavior of the railway systems. In this paper, we investigate and mathematically analyze the double grazing bifurcations of the railway wheelset systems with flange contact. Two types of models of flange impact are considered, one is a rigid impact model and the other is a soft impact model. First, we derive Poincaré maps near the grazing trajectory by the Poincaré-section discontinuity mapping (PDM) approach for the two impact models. Then, we analyze and compare the near grazing dynamics of the two models. It is shown that in the rigid impact model the stable periodic motion of the railway wheelset system translates into a chaotic motion after the grazing bifurcation, while in the soft impact model a pitchfork bifurcation occurs and the system tends to the chaotic state through a period doubling bifurcation. Our results also extend the applicability of the PDM of one constraint surface to that of two constraint surfaces for autonomous systems.

Simulation of the electric field of a polymer bushing in the Ansys Maxwell software environment

The article analyses the software tools for modelling the maps of the electric field strength of insulators. The need to address this issue is dictated by the fact that the uneven electric field on the insulators increases the probability of partial discharges that destroy the insulating layer, so it is very important to optimize the electric field strength on the insulator. The design features of bushings and features of partial discharges in them are considered. The distribution of electric field strength in a polymer pass-through operating in an AC network without contaminants is considered. The results of modelling the electric field of insulators in the software environment Ansys Maxwell, which is based on the simulation of the finite element method, are presented. Points in the construction of a 35 kV bushing polymer insulator have been identified, where the highest level of electric field strength is concentrated. A method of influencing the area under study in the area of the flange connection to the ground plate is proposed. This defines the use of a conductive cover placed between the flange and the place of connection to the polymeric insulating layer, which significantly improves the overall electric field strength distribution on the surface of the bushing polymer insulator and makes it competitive compared to the most commonly used porcelain bushings, by increasing the electrical strength of the structure. According to the results of research, a means of optimizing the electric field of the pass-through polymer insulator is proposed, which allows to increase its electric resistance and reduce the electric field strength in the area of flange contact with the mounting surface, which in turn prevents premature partial discharges in the insulating bodies.

Assessing the fast non-Hertzian methods for wheel-rail rolling contact integrated in the vehicle dynamics simulation

An accurate and high-efficiency contact model is essential for vehicle-track dynamic simulation and wear prediction. The paper attempts to assess the influence of different contact models on the offline and online simulation, as well as wear depth distribution. Taking CONTACT as the reference model, the computational accuracies of contact model combinations (i.e. Hertz + FASTSIM, Kik–Piotrowski (KP) + FASTSIM, modified Kik–Piotrowski (MKP) + FASTSIM and MKP + FaStrip) are evaluated. Typical wheel-rail contact cases and two dynamic simulation cases (track irregularity and curve track) have been studied. Results show that MKP + FaStrip achieves the best computational accuracy in calculating the typical wheel-rail contact situation, besides, the yaw angle has a significant influence on the contact patch shape and pressure distribution, especially when the wheel flange contacts with a rail corner. With regard to the vehicle passing the track with the lateral irregularity, both KP + FASTSIM and MKP + FaStrip models can achieve relatively good agreement on dynamic results and wear prediction with CONTACT. In terms of the curve track, MKP + FaStrip has better accuracy on dynamic results and wear due to a larger yaw angle.

Towards the understanding of wheel-rail flange squeal: In-situ experiment and genuine 3D profile-enhanced transient modelling

Wheel-rail squeal noise during train turning has been a tricky problem influencing passengers and nearby residents. The tonal curve squeal that mainly occurs at the inner rail has been extensively studied, while the broadband flange squeal that takes place at the outer rail that can be equally annoying is seldom mentioned and hardly investigated. This paper presents a study aiming at understanding the mechanism of wheel-rail flange squeal from phenomenon to the underlying source. The study systematically demonstrates the connection between the observed wheel-rail flange squeal noise and contact force, with measurements taken from a series of well-controlled in-situ experiments on an operating metro line, and numerical simulations. An integrated transient model consisting of three submodels on train dynamics, rail dynamics, and wheel-rail contact incorporating genuine 3D surface irregularities is developed specifically for flange squeal analysis. The developed model can reproduce the characteristics of flange squeal and correlates wheel-rail contact force with the flange squeal noise with satisfactory performance. Features of flange squeal under four-speed levels corresponding to in-situ experiments are reappeared from global dynamics to local contact status. An explanation of the generation mechanism of flange squeal is proposed by measurement observation and confirmed through the proposed model with multiple influencing key factors, including train speed, contact position, shape of contact patch, contact creepages, and wheel and rail irregularities. The present study is expected to establish a footstone for the mechanism comprehension of flange squeal and inspire further research in this area.

Effect Mechanism and Performance Evaluation of Flange Contact Thermal Resistance in an Aero-Engine

According to the discontinuous structural characteristics of a gas turbine, by considering the contact thermal resistance of the rough surface, a contact thermal resistance measurement experiment was conducted in this study. The main objectives of this work were to investigate the influence mechanism and change law of the contact thermal resistance characteristics on flange installation. Furthermore, this study conducted a theoretical analysis of contact thermal resistance and the calculation of a typical flange mounting edge based on actual operating conditions. The research results show that the contact thermal resistance of a typical flange mounting edge increases with an increase in flange clearance under different tightening torques, which is essentially proportional to the flange clearance. As the flange clearance increases, the unit contact thermal conductivity firstly decreases rapidly. Then, as the flange clearance reaches 0.4 mm, the decreasing rate of unit contact thermal conductivity tends to flatten. In addition, the contact thermal resistance of the typical flange mounting edge decreases with the increase in the tightening torque under different flange clearances. Furthermore, the contact area ratio is not related to the material, and the contact thermal resistance under actual working conditions can be calculated using the unit contact area.

Comparison of numerical and computational aspects between two constraint-based contact methods in the description of wheel/rail contacts

The numerical and computation aspects of the Knife-edge Equivalent Contact (KEC) constraint and lookup table (LUT) methods are compared in this paper. The LUT method implementation uses a penetration-based elastic contact model for the flange and a constraint-based formulation at the wheel tread. For the KEC method, where an infinitely narrow rail contacts an equivalent wheel, regularization of the tread-flange transition is adopted to simultaneously account for tread and flange contacts using constraints. A comparison between the two methods is carried out using well-known numerical integrators to show the applicability and limitations of both methods.Two fixed-step-size integrators, the explicit Runge–Kutta (RK4) and the predictor–corrector Adam–Bashforth–Moulton (ABM) methods, and two variable-step-size Matlab built-in function integrators, the explicit ode45 and implicit ode15s, were applied to get the numerical solutions to the dynamic problems and study the relative numerical performance of the two contact description methods. To complete the railway vehicle model, both contact methods were implemented for the multibody model of a benchmark railway vehicle (the Manchester wagon 1). Numerical results were obtained for different railway tracks with and without irregularities. Profiles of the S1002 wheel and LB-140-Area rail, which demonstrate the two-point contact phenomenon, were considered. Both methods were implemented in Matlab and validated against commercial simulation software. The kinematic results for both approaches show good agreement, but the KEC method was up to 20% more efficient than the LUT method regardless of integrator used.

Research on the dynamic processes of vehicles and an arbitrary configuration rail track, influencing the side wear of the rail head and wheel flange contact surfaces at different values of friction coefficient between them

The paper studies the influence of the friction coefficient value between the rail heads and wheel flanges on the side wear between their surfaces, depending on the dynamic processes between the vehicles and the rail track of an arbitrary configuration. Research is aimed at reducing the rate of the side parts mutual wear of the rail heads and the wheel flanges of the vehicle running gears. It has been determined that a decrease in the friction coefficient in the range from 0.25 to 0.05 leads to a decrease in the indicators of side surfaces wear of the wheel flanges and rail heads by 3.5-4.5 times and an increase in the stability margin coefficient against wheel derailment of the moving vehicle running gear by 1.3-1.5 times. It has been revealed that the dynamic qualities of moving vehicles when using a continuous welded track and elongated rails, compared with the presence of butt joints on the track, decrease by 15-56%, and the stability and traffic safety indicators improve by 19-26%. The research results are provided for use in the underground, open-cut and rail transport to increase the operational life and traffic safety in transport.

Influence of suspension parameter for derailment analysis of a full railway vehicle model cruising on a curved track

The main intention of this research work is to study the derailment response of high speed railway vehicle (HSRV) cruising on a curved track. In previous research work, lower degree of freedom (DOF) has been considered for the derailment analysis which may not give more accurate results. Hence, a 31 DOF bondgraph model of HSRV has been developed which consist of carbody, two truck frames and two selfsame wheelsets for each truck frame. Vertical, lateral, roll, yaw and pitch motion are considered for carbody and bogie and except pitch motion all the other motion are considered for wheelsets. Non-linearities in terms of heuristic nonlinear creep model and flange contact has been employed to simulate the derailment response at high speed. The effect of vehicle speed running on a curved track was investigated for derailment quotient. The main aim of present research work to evaluate derailment quotient at the speed range of 150 kmph to 600 kmph for hard and soft suspension parameter. Derailment quotient has been calculated for both linear and nonlinear creep models and it is seen that DQ for linear model has a lower value compare to non linear creep. The major advantages of the proposed model are that, the presented model can actively predict the derailment of a railway vehicle, and also precisely determine the nonlinear critical hunting speeds.

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.

Investigating the friction, wear and damage behaviour of plain bearing bushes of the variable stator vane system

Determining the friction, wear and damage behaviour of aero engine components under realistic operation conditions is important to improve the long-term reliability and efficiency. A special test rig for single plain bearing bushes of the variable stator vane (VSV) system was designed to investigate these components under engine-like conditions. It is found that four main wear and failure phenomena occur during the testing of VSV bushes. These include heavy abrasive wear on the inner contact area, wear on the flange contact area, plastic deformation and material failure as well as heavy wear and debris on the spindle. Results from polyimide-based plain bearing bushes show that the operational torque and wear rate remain almost constant, as long as no failure of the bush occurs.