High-Speed Railway Turnout Research Articles

Numerical investigation on effect of the relative motion of stock/switch rails on the load transfer distribution along the switch panel in high-speed railway turnout

ABSTRACTIn railway turnout, the stock rail and switch rail are separated to enable the vehicle changing among the tracks, and they are provided with different rail resilience level on the baseplate. Therefore, there will be vertical relative motion between stock/switch rails under the wheel loads, and the relative motion will affect consequentially the wheel–rail contact conditions. A method is developed to investigate the effect of the relative motion of stock/switch rails on the load transfer distribution along the switch panel in high-speed railway turnout. First, the rigid wheel–rail contact points of stock/switch rails are calculated based on the trace line method, and then the contact status is determined by the presented equations, finally, the distribution of wheel–rail contact forces of stock/switch rails is obtained based on the continuity of interface displacements and forces which using an approximate surface deformation method. Some parametric studies have been performed, such as the lateral displacement of wheel set, the vertical contact forces, the wheel profiles and the vertical stiffness of rail pad. The results of the parametric study are presented and discussed.

Parameters studies for rail wear in high-speed railway turnouts by unreplicated saturated factorial design

Rail wear is one of the main reasons for reducing the service life of high-speed railway turnouts in China. The rail wear characteristics of high-speed railway turnouts are influenced by a large number of input parameters of the complex train-turnout system. To reproduce the actual operation conditions of railway turnouts, random distributions of these inputs need to be considered in rail wear simulation. For a given nominal layout of the high-speed railway turnout, 19 input parameters for rail wear simulation in high-speed railway turnouts are investigated based on orthogonal design of experiment. Three dynamic responses (wheel−rail friction work, normal contact force and size of contact patch) are defined as observed values and the significant factors (direction of passage, axle load, running speed, friction coefficient, and wheel and rail profiles) are determined by two unreplicated saturated factorial design methods, including the half-normal probability plot method and Dong93 method. As part of the associated rail wear simulation, the influence of the wear models and the local elastic deformation on the rail wear was separately investigated. The calculation results for the wear models are quite different, especially for large creep mode. The local elastic deformation has a large effect on the sliding speed and rail wear and needs to be considered in the rail wear simulation.

Optimization of Rail Profiles to Improve Vehicle Running Stability in Switch Panel of High-Speed Railway Turnouts

A method for optimizing rail profiles to improve vehicle running stability in switch panel of high-speed railway turnouts is proposed in this paper. The stock rail profiles are optimized to decrease the rolling radii difference (RRD). Such characteristics are defined through given rail profiles, and the target rolling radii difference is defined as a function of lateral displacements of wheel set. The improved sequential quadratic programming (SQP) method is used to generate a sequence of improving profiles leading to the optimum one. The wheel-rail contact geometry and train-turnout dynamic interaction of the optimized profiles and those of nominal profiles are calculated for comparison. Without lateral displacement of wheel set, the maximum RRD in relation to a nominal profile will be kept within 0.5 mm–1 mm, while that in relation to an optimized profile will be kept within 0.3 mm–0.5 mm. For the facing and trailing move of vehicle passing the switch panel in the through route, the lateral wheel-rail contact force is decreased by 34.0% and 29.9%, respectively, the lateral acceleration of car body is decreased by 41.9% and 40.7%, respectively, and the optimized profile will not greatly influence the vertical wheel-rail contact force. The proposed method works efficiently and the results prove to be quite reasonable.

Stiffness Characteristics of High-Speed Railway Turnout and the Effect on the Dynamic Train-Turnout Interaction

Track stiffness in railway turnouts is variable due to differences in structural composition along the longitudinal direction, which will lead to severe dynamic interaction between train and turnout. In this paper, a transient analysis model is presented to investigate the stiffness characteristics of high-speed railway turnouts based on the finite element method and is applied to optimise the stiffness of railway turnouts. Furthermore, the effect of the stiffness variations on the dynamic train-turnout interaction is analysed. The calculation results show that the track stiffness characteristics are similar in the main and diverging line of railway turnout, except for the check rail sections. Due to the existence of shared baseplates and spacer blocks between different rails, the stiffness variations in the crossing panel are most severe in high-speed railway turnouts. The stiffness differences (calculated as the ratio of the maximum and minimum stiffness) of the longitudinal and lateral direction for Chinese number 18 ballasted turnout are 216% and 229%, respectively. The graded stiffness of the tie pads has been redesigned to optimise the stiffness of railway turnout based on the transient analysis model and the stiffness differences of the turnout are decreased. Altogether, the dynamic train-turnout interaction is enhanced remarkably by considering the turnout’s stiffness characteristics.

Wheel/Rail Contact Geometry of Different Wheel Tread Profile in High-Speed Railway Turnout

Train/turnout dynamic interaction is exacerbated by high speed of passenger train and heavy load of freight train, and wheel/rail relation is one of the key factors that determine the running characteristics of the train. Focusing on three types of wheel treads with different profiles (TB tapered tread, LM worn tread, LMA worn tread), longitudinal distribution of the contact geometric parameters along the switch rail and nose rail of 350km/h No.18 turnout are calculated, such as tread equivalent conicity, coefficient of contact angle difference, roll angle factor, gravitational stiffness of wheelset, gravitational angle stiffness of wheelset, etc. Results show that: (1) LMA worn tread produces the smallest irregularity; (2) wheel/rail vertical impact at the frog will become bigger; (3) Top profile of switch rail and nose rail should be designed according to the wheel tread type so as to mitigate the wheel/rail dynamic interaction and increase the safety and stability of a train.

Influence of Conversion Deviation on Dynamic Performance of High-Speed Railway Turnout

Railway turnout, an integrated mechatronics equipment of track technology, is one of key equipments that control the running speed of high-speed railway. During the conversion of turnout, the friction, inclusion of foreign matter and deficient displacement of conversion caused by its own structural characteristics may lead to severe wheel/rail impact. In order to study the influence of conversion deviation on safety and comfort of a train during passing the turnout, train/turnout dynamic model was applied. Taking No.18 turnout on a Passenger Dedicated Line (PDL) with 350km/h as a case study, when the train passed it, the influences of its deficient displacement and inclusion of foreign matter on the following dynamic responses were studied, i.e. wheel load distribution, wheel flange force, dynamic stress of rail, wheel unloading rate, derailment coefficient, as well as the lateral displacements of switch rail and nose rail, etc. Result shows that: (1) the deficient displacement and the inclusion of foreign matter will severely influence the normal operation of the turnout, so the safety and comfort during the train passing through turnout may be affected; (2) During the conversion of turnout, its deficient displacement should be controlled properly, and the foreign matter should be removed during routine maintenance, moreover, a reliable detection system should be set.