Gauge Widening Research Articles

Use of Finite Element and Finite Segment Methods in Modeling Rail Flexibility: A Comparative Study

Safety requirements and optimal performance of railroad vehicle systems require the use of multibody system (MBS) dynamics formulations that allow for modeling flexible bodies. This investigation will present three methods suited for the study of flexible track models while conclusions about their implementations and features are made. The first method is based on the floating frame of reference (FFR) formulation which allows for the use of a detailed finite element mesh with the component mode synthesis technique in order to obtain a reduced order model. In the second method, the flexible body is modeled as a finite number of rigid elements that are connected by springs and dampers. This method, called finite segment method (FSM) or rigid finite element method, requires the use of rigid MBS formulations only. In the third method, the FFR formulation is used to obtain a model that is equivalent to the FSM model by assuming that the rail segments are very stiff, thereby allowing the exclusion of the high frequency modes associated with the rail deformations. This FFR/FS model demonstrates that some rail movement scenarios such as gauge widening can be captured using the finite element FFR formulation. The three procedures FFR, FSM, and FFR/FS will be compared in order to establish differences among them and analyze the specific application of the FSM to modeling track flexibility. Convergence of the methods is analyzed. The three methods proposed in this investigation for modeling the movement of three-dimensional tracks are used with a three-dimensional elastic wheel/rail contact formulation that predicts contact points online and allows for updating the creepages to account for the rail deformations. Several conclusions will be drawn in view of the results obtained in this investigation.

Modeling railroad track structures using the finite segment method

In the finite segment method, the dynamics of a deformable body is described using a set of rigid bodies that are connected by elastic force elements. This approach can be used, as demonstrated in this investigation, in the simulation of some rail movements. In order to ensure that the rail geometry is not distorted as the result of the finite segment displacements, a new track model that consistently integrates the absolute nodal coordinate formulation (ANCF) geometry and the finite segment method is developed. ANCF finite elements define the track geometry in the reference configuration as well as the change in the geometry due to the movement of the finite segments of the track. Using ANCF geometry and the finite segment kinematics, the location of the wheel/rail contact point is predicted online and used to update the creepage expressions due to the finite segment displacements and rotations. The location of the wheel/rail contact point and the updated creepage expressions are used to evaluate the creep forces. A three-dimensional elastic contact formulation (ECF-A) which allows for wheel/rail separation is used in this investigation. The rail displacement due to the applied loads is modeled by a set of rigid finite segments that are connected by a set of spring-damper elements. Each rail finite segment is assumed to have six rigid body degrees of freedom. The equations of motion of the finite segments are integrated with the railroad vehicle system equations of motion in a sparse matrix formulation. The resulting dynamic equations are solved using a predictor–corrector numerical integration method that has a variable order and variable step size. The finite segments may be used to model specific phenomena that occur in railroad vehicle applications, including rail rotations and gauge widening. The procedure used in this investigation to implement the finite segment method in a general purpose multibody system (MBS) computer program is described. Two simple models are presented in order to demonstrate the implementation of the finite segment method in MBS algorithms. The limitations of using the finite segments approach for modeling the track structure and rail flexibility are also discussed.

Track gauge optimisation of railway switches using a genetic algorithm

A methodology for the optimisation of a prescribed track gauge variation (gauge widening) in the switch panel of a railway turnout (switch and crossing, S&C) is presented. The aim is to reduce rail profile degradation. A holistic approach is applied, where both routes and travel directions (moves) of traffic in the switch panel are considered simultaneously. The problem is formulated as a multi-objective minimisation problem which is solved using a genetic-type optimisation algorithm which provides a set of Pareto optimal solutions. The dynamic vehicle–turnout interaction is evaluated using a multi-body simulation tool and the energy dissipation in the wheel–rail contacts is used for the assessment of gauge parameters. Two different vehicle models are used, one freight car and one passenger train set, and a stochastic spread in wheel profile and wheel–rail friction coefficient is accounted for. It is found that gauge configurations with a large gauge-widening amplitude for the stock rail on the field side are optimal for both the through and diverging routes, while the results for the gauge side show a larger route dependence. The optimal gauge configurations are observed to be similar for both vehicle types.

Improvement of curving performance by expansion of gauge widening and additional measures

Lateral forces between wheels and rails must be reduced in order that rolling stock runs safely and smoothly on curved tracks. The excessive lateral force will cause not only derailment of rolling stock but also destruction of tracks, rail corrugation, track irregularity, squeal noise and wear. It is important to reduce lateral force of wheels in curves, so new wheel-tread profiles and steerable bogie structures have been developed up to now, however, they cannot solve various problems in curving perfectly. In this article, the authors propose three methods for improvement of running performance on curves by using existing types of wheels and rails, and analyse the effects of three methods by numerical simulation. According to analytical results, the authors conclude that ‘expansion of gauge widening’, and ‘larger rail inclination angle of inner rail installation’ or ‘asymmetrically inclined grinding of inner rail head’ can get sufficient rolling radius difference, and are effective for improvement of running performance on curved tracks.

Geometry and stiffness optimization for switches and crossings, and simulation of material degradation

A methodology for simulating wear, rolling contact fatigue, and plastic deformation for a mixed traffic situation in switches and crossings (S&C) has been developed. The methodology includes simulation of dynamic vehicle—track interaction considering stochastic variations in input data, simulation of wheel—rail contacts accounting for non-linear material properties and plasticity, and simulation of wear and plastic deformation in the rail during the life of the S&C component. To find means of improving the switch panel design, the geometry of a designed track gauge variation in the switch panel has been represented in a parametric way. For traffic in the facing and trailing moves of the through route, an optimum solution was identified and then validated by evaluating a wide set of simulation cases (using different wheel profiles). The optimum design includes a 12 mm maximum gauge widening. Several crossing geometries were investigated to find an optimal geometric design for the crossing nose and wing rails. The MaKüDe design showed the best performance for moderately worn wheel profiles in both running directions (facing and trailing moves). In connection with reduced support stiffness (e.g. elastic rail pads), this crossing design is predicted to lead to a significant reduction of impact loads and consequently provide a high potential of life-cycle cost reduction.

Study on Running Safety with Gauge Widening

Gauge widening has been set in order that rolling stock runs safely and smoothly on curved tracks. Recently gauge widening has been reduced due to the change of vehicle structures and track maintenance. The reduction of gauge widening may lead the decrease of steering ability of wheelsets and running safety of vehicles. The purpose of this study is to grasp curving performance and running safety when gauge widening was varied. Stand tests were carried out by a bogie test stand, and the authors concluded that the curving performance can be increased according to gauge widening, but the effect is limited in perfect rolling region, and not so effective for normal setting range.

359473 STUDY ON RUNNING SAFETY WITH GAUGE WIDENING(Bogie,Technical Session)

Gauge widening has been set in order that rolling stock runs safely and smoothly on curved tracks. Recently gauge widening has been reduced due to the change of vehicle structures and track maintenance. The reduction of gauge widening may lead the decrease of steering ability of wheelsets and running safety of vehicles. The purpose of this study is to grasp curving performance and running safety when gauge widening was varied. Stand tests were carried out by a bogie test stand, and the authors concluded that the curving performance can be increased according to gauge widening, but the effect is limited in perfect rolling region, and not so effective for normal setting range.

スラック拡大による鉄道車両の走行性向上効果に関する検討 : 都市鉄道向け車輪踏面における直進安定性と曲線通過性能の改善(機械力学,計測,自動制御)

スラック拡大による鉄道車両の走行性向上効果に関する検討 : 都市鉄道向け車輪踏面における直進安定性と曲線通過性能の改善(機械力学,計測,自動制御)

Simulation of dynamic gauge widening and rail roll: effects on derailment and rolling contact fatigue

This paper compares the different effects of rail rotations versus rail lateral translations on wheel/rail (W/R) contact geometry and vehicle dynamic performance. This study, conducted by the Transportation Technology Center, Inc. (TTCI), shows that: rail rotation has significant effects on the W/R contact geometry, especially on contact positions and contact areas, while rail translation effects on wheel contact positions and contact areas are negligible; a W/R contact model with assumptions of rigid track or elastic track with only lateral and vertical rail translations cannot reflect the W/R contact geometry variations caused by rail rotations; the contact geometry variations caused by rail rotations strongly depend on the specific wheel and rail profiles under evaluation; proper rail rotation flexibilities within the safety limits could improve wheelset steering performance and decrease W/R contact stress and wear.

A302 Effect of Gauge Widening on Curve Negotiation of Two-Axle Bogie Vehicles Considering Steering Mechanism and Wheel Tread Profile

According to the decrease of the three-axle bogie for locomotives in Japan, the need for diminution of the gauge widening in curved track has been pointed out by rail maintenance division. Meanwhile, bolsterless bogies which can have more steering ability are employed in many rail vehicles, and wheels with profiled tread have been used widely. For vehicles which have such bogies and wheels, it is expected that the gauge widening still keeps its effect on the curve negotiation even now. In this paper, the curving performance under the presence of gauge widening is investigated in detail considering the recent trend. The wheel lateral forces during curve negotiation obtained by numerical simulation are compared among vehicle types classified with truck mechanisms and wheel tread shapes. As a result, it is shown that the effectiveness of gauge widening exists for bolsterless truck and steering truck, but the availability to the trucks with profiled wheel is little because the change of wheel shape, from conical tread to profiled one, gives much effect on the performance. Then, a modification of shape in profiled tread is examined to get further availability of gauge widening.

An Analysis of Curve Negotiation for Two-Axle Bogie Vehicle Considering the Effect of Gauge Widening. 2nd Report. In case of Profiled Wheel Tread.

The previous report made clear that the gauge widening was still effective for the curving performance of rail vehicles with bolsterless trucks or forced steering ones. Here, the examination was carried out using wheels with conical tread. However, wheels with profiled tread have been employed widely in recent years, because they can secure not only the running stability but also the curving performance. In this paper, the curving performance under the presence of gauge widening is investigated in detail for the trucks with profiled-tread wheels. The wheel lateral forces obtained by the numerical simulation on the curve negotiation are compared among vehicle types classified with truck mechanisms and wheel tread shapes. As a result, it is shown that the availability of gauge widening to the trucks with profiled wheels is little because the change of wheel shape, from conical tread to profiled one, gives much effect on the performance. Then, the modification of tread shape is examined to get further availability of gauge widening. It is shown that the effectiveness of wheel shape modification can be obtained also in a vehicle assumed to negotiate very tight curves at lowspeeds.

基調講演OS0]鉄道車両の曲線通過とスラック,操舵性台車

基調講演OS0]鉄道車両の曲線通過とスラック,操舵性台車

2210 スラックが二軸ボギー車の曲線通過に及ぼす運動学的影響 : 第4報,踏面形状変更の効果(OS0 交通・物流機械のダイナミクス,振動,騒音,制御)

2210 スラックが二軸ボギー車の曲線通過に及ぼす運動学的影響 : 第4報,踏面形状変更の効果(OS0 交通・物流機械のダイナミクス,振動,騒音,制御)

511 スラックが2軸ボギー車の曲線通過に及ぼす運動学的影響 : 第3報,接触モデルの改善(O.S.5-2 衝突・接触問題)(オーガナイズドセッション5 : 機械の動的問題)

511 スラックが2軸ボギー車の曲線通過に及ぼす運動学的影響 : 第3報,接触モデルの改善(O.S.5-2 衝突・接触問題)(オーガナイズドセッション5 : 機械の動的問題)

An Analysis of Curve Negotiation for Two-Axle Bogie Vehicle Considering the Effect of Gauge Widening.

According to the decrease of the three-axle bogie for locomotives, the need for diminution of the gauge widening in curved track has been pointed out by rail maintenance division. Meanwhile, bolsterless bogies which have no side bearer are employed in many railway vehicles recently, and it is expected that various steering bogies will be employed in the near future. For vehicles which have these bogies, the gauge widening keeps its effect on curve negotiation even now. In this study, the dynamical analysis is carried out about the relationship between the gauge widening and the track load, considering the bogie mechanism. Numerical simulation is used for the analysis, and the effectiveness of gauge widening is summarized from dynamical viewpoint of two-axle bogie vehicles. Further, wear indices are introduced, and the wear tendency of flange and tread is estimated quantitatively.

Strength and stability of railway tracks—II Deterministic, finite element stability analysis

A previous paper [F. Arbabi, A.N. Sherbourne and H.A. El-Ghazaly, Comput. Struct. 38, 681–693 (1991)] presented a simple probabilistic finite element analysis of the interaction between load and deflection in the context of the standard beam on elastic foundation model in which both the vertical load and subgrade response can be expressed statistically. In this study an analytical formulation and computer program is developed for stress and stability analysis of track under static, deterministic loads. The formulation is also based on the finite element method. A bifurcation by bulking analysis allows the determination of all instability modes, including lateral (gauge widening) and torsional buckling (rail overturning), from a zero displacement reference position. A program allows complete flexibility in terms of rail profile and unit weight, input loads involving vertical, lateral and longitudinal components and four types of foundation restraint affecting vertical and lateral displacements and rail extension and rotation. While no attempt is made to derive specific values or relationships between these components of load or foundation moduli, the analysis extends the conventional beam on elastic foundation model, which has heretofore found considerable application in track related problems.

Automated Gauge Inspection

Several incidents had occurred on the Louisville & Nashville (L&N) Railroad where a dynamic gauge-widening tendency was believed to exist. To investigate this possibility, rail proximity sensors were mounted on a locomotive truck to measure track gauge under dynamic load. In association with the electronic system for gauge measurement, a paint spray system was installed which sprayed the track with a clearly visible line whenever gauge exceeds a predetermined threshold value. Using this equipment, track was inspected automatically at high speed and priority defects were automatically marked for immediate repair. The gauge measuring system consisted of a pair of capacitive sensors which respond to the gaps between the sensors and their corresponding rail heads. Continuous gauge data was recorded on a two-channel oscillograph. One channel was used to record track gauge and the other was used to denote location information via coded signals manually introduced by the system operator. Verification of system performance was carried out by measuring dynamic gauge-widening effects on a carefully instrumented curve and by performing comparative unloaded measurements over many miles of track. Gauge widening under dynamic loading was observed, and the existence of this effect was verified.