Railway Curves Research Articles

Optimization of Polynomial Transition Curves from the Viewpoint of Jerk Value

Abstract The aim of the presented paper is to show the results of shape optimization of railway polynomial transition curves (TCs) of 5th, 7th, and 9th degrees through the use of the full vehicle model and new criteria of assessement concerning the jerk value. The search for the proper shape of TCs means that in this work, the evaluation of TC properties is based on select quantities and the generation of such a shape through the use of mathematically understood optimization methods. The studies presented have got a character of the numerical tests. For this work, advanced vehicle models describing dynamical track-vehicle and vehicle-passenger interactions as well as optimization methods were exploited. In the software vehicle model of a 2-axle freight car, the track discrete model, non-linear descriptions of wheel-rail contact are applied. This part of the software, the vehicle simulation software, is combined with a library optimization procedure into the final computer program.

Effect of Temperature on Mechanical Properties and Torsional Friction Behaviors of Bogie Center Plate

In order to simulating the torsional friction of the center plate during the railcar body traveling on different railway curves at different environmental temperatures, the torsional friction behavior of monomer casting (MC) nylon composites which was used to make center plate, at temperatures of −25 °C to 50 °C was studied. With increasing temperature, the mechanical properties of nylon composites were weakened, whereas the visco-elastic property was boosted. Under torsional angle of 1.8 deg and 0.96 deg, all the torque–angular displacement (T–θ) curves exhibited the quasi-parallelogramic shape at various temperatures. When the temperature was higher than 25 °C under 0.42 deg, the shape transformed from elliptic to parallelogrammic. This indicated that the torsional regime changed from a partial slip to a gross slip. With increasing temperature, the torsional torque decreased and the wear mass loss increased because of weakened mechanical properties. The wear mechanism changed from slight plastic flow at low temperature to serious adhesive and three-body abrasion wear at high temperature.

Detection of geometric change in railway curves caused by earthquakes, using high-resolution stereo satellite images

Rapid change detection of railway curves is crucial for the damage assessment of unexpected disasters such as earthquakes. Detection of the geometric change in railway curves involves the measurement of the shape change by comparing the pre- and post-seismic railway curves. This paper proposes an approach for change detection in railway curves by the use of a pre-seismic digital topographic map and post-seismic stereo IKONOS images. The proposed approach consists of four main components, they are as follows: (1) The geometric parameters of the pre-seismic railway curves are first estimated based on the digitized points from the digital topographic map by the use of least squares adjustment. (2) The feature points on the post-seismic railway curves are then extracted from the high-resolution stereo satellite imagery, and the ground coordinates of these points are further refined by the use of rational function polynomial coefficients bundle adjustment. (3) Five change detection models—the shift model, the scale and shift model, the affine model, the second-order polynomial model, and the similarity model—are introduced to describe the geometric change between the pre- and post-seismic railway curves. Based on this, an objective function is formulated to minimize the squared distances between the transformed points from the post-seismic points refined from the high-resolution stereo imagery, based on the change detection model and the pre-seismic railway curves. An empirical experiment in change detection in railway curves as a result of the 2008 Wenchuan earthquake in Dujiangyan City, China, was conducted. The experimental results showed the feasibility of the proposed geometric change detection method, they are as follows: (1) The root-mean-square error of the geometric parameter estimation of the pre-seismic railway curve was 0.068 m, which showed that the proposed least squares approach could recover the geometric curve of the pre-event railway with a centimeter-level accuracy by the use of the digital topographic map. (2) The result of the refinement of the ground control points extracted from the pre-seismic high-resolution satellite imagery by the use of the four bias compensation models showed that the second-order polynomial model achieved the highest geo-positioning accuracy of 0.788 and 0.701 m in the x- and y-directions. This result indicated that the second-order polynomial model was the best bias compensation model for improving the accuracy of ground points extracted from the post-event stereo image pairs. (3) A comparison of the five change detection models, in terms of displacement between the pre- and post-seismic railway curves, showed that the affine model obtained the highest accuracy of 0.318 m. This result showed that the geometric change in railway curves due to earthquakes could be detected with a decimeter-level accuracy by the use of the proposed change detection approach, based on a pre-seismic digital topographic map and post-seismic IKONOS stereo images.

Reducing rail side wear on heavy-haul railway curves based on wheel–rail dynamic interaction

This article investigates an optimisation strategy for the design of rail-grinding profiles to be used on heavy-haul railway curves, aiming to reduce the rail side wear on curves. A design methodology of rail asymmetric-grinding profiles is put forward based on the principle of low wheel–rail dynamic interaction. The implementing procedure is illustrated in detail. As a case study, the rail asymmetric-grinding profiles were designed for a curve with 600 m radius on Chinese Shuohuang heavy-haul railway. The characteristics of wheel–rail contact geometry and wheel–rail dynamic interaction were analysed and compared between the original standard rail profiles and the designed rail-grinding profiles. The rails on a test curve were ground according to the designed profiles. Before and after rail grinding, both the wheel–rail dynamics indexes and the rail side wear were measured in the field. The theoretical and experimental results show that the wheel–rail dynamic interaction is clearly improved and the rail side wear is alleviated by 30–40% after rail grinding, which validates the effectiveness of the design methodology of rail asymmetric-grinding profiles on curves.

INVESTIGATION INTO THE CALCULATION OF SUPERELEVATION DEFECTS ON CONVENTIONAL RAIL LINES

Railway curves have influence on train speed on a curve and/or wheel/rail interface. Additional forces that have to be compensated appear in the curves. The purpose of superelevation is to compensate acceleration emerging in the curve thus assuring comfortable passenger transportation and equal wearing of both rails. However, it is very difficult to calculate superelevation when designing and maintaining a railway track, because the estimation of actual train speed on the curves is very complicated. As we know, railway lines can be divided into conventional, high speed and heavy haul ones. As these lines are absolutely different, requirements for the installation and maintenance of the track may also differ. Conventional rail lines are the object of research discussed in this article. The speed of freight and passenger trains is different on conventional rail lines, which is an essential factor in determining superelevation. On the ground of scientific researches, the article analyzes and evaluates the factors influencing wheel/rail interface on the curves. The paper also deals with railway line curves, superelevation and uncompensated lateral acceleration. The article presents the method used in Lithuania for calculating superelevation in the railway curves and analyzes calculation defects. For research purposes, analytical and statistical methods have been used. The obtained results have shown that actual superelevation in the researched curves does not match the calculated one. The calculations and obtained results of superelevation depend on how average train speed in the curves is estimated and used for calculations. As most of the results show that even small variations in the curve have a great influence on track/vehicle behaviour, it is necessary to find more precise methods for calculating superelevation, evaluating actual train speed and considering permissible uncompensated lateral acceleration in the curves.

Construction of High-Speed Tracks

The current situation and conditions of construction of high speed tracks (HST) in the Slovak Republic and the comparison with the situation abroad. The speed of train sets and the track quality for high speed trains. The dynamics of railway running. The speeds of the HST trains are limited by the respective track state. The tilting train set wagons - increasing the new levels of speeds in railway curves. The time comparison of the high speed trains to air and road transport "from city centre to city centre". The required conditions and parameters of construction of high speed tracks up to Vmax 200-240 km.h1 within the track modernizations.

예측소음도와 설문결과를 이용한 철도소음 노출-반응 모델

The suggested method of previous Son's study dichotomized subjective response data to modeling noise exposure-response. The method used maximum liklihood estimation instead of least square estimation and the noise exposure-response curve of the study was logistic regression analysis result. The method was originated to modeling community response rate such as %HA or %A. It can be useful when the subjective response was investigated based on predicted noise level. It is difficult to measure the single source emitting noise such as railway because various traffic noise sources combined in our life. The suggested method was adopted to model in this study and railway noise-exposure response curves were modeled because the noise level of this area was predicted data. The data of this study was used by previous Ko's paper but he dealt the area as combined noise area and divided the data by dominant noise source. But this study used all data of this area because the annoyance response to railway noise was higher than other noise according to the result of correlation analysis. The trend of the %HA and %A prediction model to train noise of this study is almost same as the model based on measured noise of previous Lim's study although the investigated areas and methods were different.

Estimating Geometric Parameters of Highways and Railways Using Least-Squares Adjustment

This paper introduces a least-squares based approach that is developed for the estimation of horizontal geometric parameters of highways and railways. Curve recovery forms an important procedure in the establishment of the spatial database of a Geographic Information System for Transportation (GIS-T), which is especially essential nowadays when different mobile mapping systems such as those using Global Positioning System (GPS) are widely employed for data acquisition. Comparing with the existing methods that estimate the geometric parameters of highway and railway alignments such as straight-lines, circular curves or spiral curves individually, this study discusses how to extract the entire set of parameters of combined alignments simultaneously with an integrated estimation method. Two case studies were used to show the feasibility of the developed technique. The first example investigates the possibility for recovering the geometric parameters of expressway curves whilst the second experiment entails realignment of existing railway curves. The results show that the proposed method has the advantages of high accuracy in the estimation of highway and railway curve parameters, and of less track lining work comparing with the traditional method in railway track realignment.

Comparison of railway track transition curves

There are no design parameters related to speeds exceeding 160 km/h in the effective Hungarian railway design rules. In the relevant international standard (ENV 13803) a similar speed limit is 300 km/h. This paper deals with the comparative of these regulations. Parameters of two transition curves used in Hungary and other used in Austria are determined. The importance of the new design parameters provided by ENV 13803 is assessed. It is demonstrated that the usability of the clothoide transition curves is unnecessarily restricted for the speeds v ≤120 km/h in the Hungarian regulations.

Dynamic analysis of railway transition curves

Transition curves play an important role in riding quality, especially for high-speed railways. Accordingly, various curves have been proposed as transition forms. To evaluate the effects of the forms in transition curves, the basic requirements and forms of transition curves were first discussed, and then simulations were performed with several typical transition curves at various speeds, based on the dynamic model developed in this research. The results indicate that the dynamic effects of transition curves are determined by the curvature variation and the order of the curvature derivative that is equal to zero at the curve endpoints, while the expression mode (such as algebraic or trigonometric expression) does not make much difference. From a dynamic viewpoint, the ideal transition form requires that the second derivative of its curvature is equal to zero at the curve endpoints at least, such as the seventh parabola, ninth parabola, and sinusoid, with which the vibration accelerations of the vehicle vary smoothly and the jerk can be effectively eased. Then the appropriate transition forms are recommended for ordinary and high-speed railways, respectively.

INVESTIGATION OF THE ACCURACY OF THE POLAR METHOD OF SHOOTING RAIL CURVES

Questions of accuracy new polar way of shooting of railway curves are considered.

Temperature in a twin-disc wheel/rail contact simulation

Temperature in a machine element contact is critical in determining wear mechanisms and the conditions at which wear transitions occur. Calculations have shown that the temperature in a wheel/rail contact under severe contact conditions may lead to a transition from severe wear to catastrophic wear. Such high lateral loads and slips can occur in wheel flange contact at railway track curves. The aim of this work was to use a thermal camera to measure the temperatures in a twin-disc simulation of a wheel/rail contact. Disc body and contact temperatures were studied for a number of different contact conditions. Disc emissivity values were determined using an independent calibration test. Measured temperatures were compared with those derived using analytical models which equate frictional heat generated in the contact with heat dissipation due to conduction, convection and radiation. Good correlation was found between the experimental and analytical results. This is despite the fact that its emissivity values were assumed constant throughout the test.

Investigation of dynamic models of independently rotating wheels of wagons

Abstract The article deals with the modelling of independently rotating wheels (IRW) systems for wagons. The research work of the intensity of rolling stock wheels rims and flanges is observed. The main performance objectives of IRW are to reduce winding of wheel‐sets, to enable railway rolling stocks to achieve higher speeds, to decrease wear of rail and wheel rolling surface, to improve the performance on railway curves and to reduce lateral displacement on rails. IRW with profiled tread are examined and the mathematical model of these IRW is created. Finally, the peculiarities of the stability and wearing characteristics of such IRW systems are presented.

INVESTIGATION OF DYNAMIC MODELS OF INDEPENDENTLY ROTATING WHEELS OF WAGONS

The article deals with the modelling of independently rotating wheels (IRW) systems for wagons. The research work of the intensity of rolling stock wheels rims and flanges is observed. The main performance objectives of IRW are to reduce winding of wheel‐sets, to enable railway rolling stocks to achieve higher speeds, to decrease wear of rail and wheel rolling surface, to improve the performance on railway curves and to reduce lateral displacement on rails. IRW with profiled tread are examined and the mathematical model of these IRW is created. Finally, the peculiarities of the stability and wearing characteristics of such IRW systems are presented.

Curving Simulation of Active Steering Vehicle Using a Multibody System Software

On sharp railway curves as those that are rare in mainlines, the wheel lateral force of rail vehicles increases due to the growth of attack angle and causes the heavy wear of both wheel flange and rail. This paper deals with the curving performance of an active steering vehicle that is converted from a self-steering one by replacing the damper in the longitudinal axle supporting mechanism to an actuator. MBS software SIMPACK is employed for the simulation. Simulation results show that the active steering system has a potential to reduce the lateral force even in sharp curves the radius of which is less than 200 m, while the original self-steering vehicle cannot achieve the reduction. It is also indicated that the running stability of the vehicle with proposed active steering mechanism does not lower from the self-steering condition and the control force generated by track irregularity does not become large up to the level that increases the running vibration and wheel lateral force on tangent track.

A NEW TRANSITION CURVE

AbstractAn analysis of the transitional properties of the curve l2 = c2 tan ½ψ, where l is the tangent terminated by the x axis, 2l is the distance along the x axis from origin to tangent, ψ is the slope angle and c is a constant associated with the geometrical dimensions of the curve.The use of the parameter l makes possible the development of very simple exact expressions for both cartesian and polar co-ordinates, for curvature, for shift distance and for position of point of tangency between circular curve and shifted x axis.Special advantages are demonstrated in connexion with road and railway curves which are wholly transitional, and with oval racing tracks.An example is worked out.

Realignment of railway curves without alteration of length of route

Abstract Some years ago the writer was engaged on the recentering of a long section of a very sinuous main railway line subjected to fast and heavy traffic.

1495. Road and railway curves

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The Elements of Analytical Geometry

It is not often that the writer of a mathematical book is privileged to have such a varied experience as the author of this volume. Mr. Craig declares in the preface that he has been called upon to “deal with questions in fields as diverse as Celestial Mechanics, Sport, Geodesy, Hydrography, Meteorology, Ballistics, Census, Agriculture, Food Supply, Statistics, Pensions, Public Health, and Currency Theory”. In all these, he pays a tribute to the value of the mathematical habit of thought, in general, and to the practical utility of analysis applied to geometry, in particular. The course embodied in the book is the immediate outcome of lectures delivered at the Royal School of Engineering, Cairo, and these are based to a large extent on a long experience in the application of analytical geometry to the solution of practical problems. The straight line and circle form the subject matter of this first volume, and the treatment is not only full—trilinear and tangential co-ordinates and vector equations of the circle being included—but also, as might be anticipated, is characterised by numerous practical applications. Amongst these, such interesting topics as railway curves, circular nomograms, and sound-ranging are excellently dealt with. Whilst, however, the book certainly has a practical bias, the theoretical side is not only well covered, but also appears to be mathematically sound. The volume, which has also been translated into Arabic, should be very useful, especially to the engineering student who desires more than a superficial knowledge of analytical geometry.

The Transition Spiral and its Introduction to Railway Curves

The Transition Spiral and its Introduction to Railway Curves