Valeri Markine

Improvement of vehicle–turnout interaction by optimising the shape of crossing nose

Proper rail geometry in the crossing part is essential for reducing damage on the nose rail. To improve the dynamic behaviour of turnout crossings, a numerical optimisation approach to minimise rolling contact fatigue (RCF) damage and wear in the crossing panel by varying the nose rail shape is presented in the paper. The rail geometry is parameterised by defining several control cross-sections along the crossing. The dynamic vehicle–turnout interaction as a function of crossing geometry is analysed using the VI-Rail package. In formulation of the optimisation problem a combined weighted objective function is used consisting of the normal contact pressure and the energy dissipation along the crossing responsible for RCF and wear, respectively. The multi-objective optimisation problem is solved by adapting the multipoint approximation method and a number of compromised solutions have been found for various sets of weight coefficients. Dynamic behaviour of the crossing has been significantly improved after optimisations. Comparing with the reference design, the heights of the nose rail are notably increased in the beginning of the crossing; the nominal thicknesses of the nose rail are also changed. All the optimum designs work well under different track conditions.

Analysis of train/turnout vertical interaction using a fast numerical model and validation of that model

A two-dimensional (2D) finite element model has been developed for simulation and analysis of train/turnout vertical dynamic interactions at a common crossing. The model has been validated through field measurements and simulation results obtained using a three-dimensional (3D) multi-body system (MBS) model. The dynamic behaviour of three turnouts on the Dutch railway network was simulated using the 2D model. The simulation results were compared with measured data collected from the instrumented crossings containing corresponding turnouts. It was observed that the values of the vertical acceleration of the crossing nose obtained from the simulations were in good agreement with the measured values. The 2D model was verified by adapting the more intricate 3D MBS model established in the VI-Rail software. The vertical geometry of the rail used in the 2D model was obtained using the wheel trajectory from the 3D model. It was observed that the dynamic wheel forces in the two models were close to one another. From these results it was concluded that the 2D model is able to simulate train/turnout interactions with a good accuracy and thus it can be used instead of complex time-consuming numerical simulations.

Numerical Analysis of the Dynamic Interaction between Wheel Set and Turnout Crossing Using the Explicit Finite Element Method

ABSTRACT A three-dimensional (3-D) explicit dynamic finite element (FE) model is developed to simulate the impact of the wheel on the crossing nose. The model consists of a wheel set moving over the turnout crossing. Realistic wheel, wing rail and crossing geometries have been used in the model. Using this model the dynamic responses of the system such as the contact forces between the wheel and the crossing, crossing nose displacements and accelerations, stresses in rail material as well as in sleepers and ballast can be obtained. Detailed analysis of the wheel set and crossing interaction using the local contact stress state in the rail is possible as well, which provides a good basis for prediction of the long-term behaviour of the crossing (fatigue analysis). In order to tune and validate the FE model field measurements conducted on several turnouts in the railway network in the Netherlands are used here. The parametric study including variations of the crossing nose geometries performed here demonstrates the capabilities of the developed model. The results of the validation and parametric study are presented and discussed.

Optimisation of the elastic track properties of turnout crossings

Rail pads and under sleeper pads (USPs) are resilient elements inserted between the rail and the sleeper, and between the sleeper and the ballast, respectively. They improve the elastic properties of the track’s superstructure. In this paper, the approach of estimating the performance of a turnout by using the dynamic forces acting on the crossing as indicators of the extent of crossing nose damage is improved by tuning the stiffness and damping of the rail pads and USPs using a numerical optimisation method. In the optimisation problem, the dynamic forces acting on rails, sleepers and the ballast bed, which should be minimised, are considered in the objective function. Constraints are imposed on the displacements of the structural elements of the turnout crossing. The combined multi-objective optimisation problem is solved using the multipoint approximation method. The results of the optimisation show that application of softer rail pads combined with USPs can significantly reduce the dynamic forces acting on the rails, sleepers and ballast. Moreover, the track elasticity should be varied along the crossing.

Optimisation of the dynamic properties of ladder track to minimise the chance of rail corrugation

The ladder track used by the Beijing subway which can be subjected to rail corrugation is considered in this paper. Dynamic models of the vehicle and the ladder track are developed to analyse the track vibration behaviour. Using these models the effect of the most significant ladder track parameters on track vibrations are analysed in the frequency and time domains. Using experimental and numerical results the vibration frequency of the rail that is responsible for rail corrugation is determined. Based on the results of the parametric study, an optimisation of the mechanical properties of the ladder track to reduce or eliminate the track vibrations at the corrugation frequency and ultimately to reduce the chance of rail corrugation is performed using a genetic algorithm-based approach. The results of the optimisation are presented and discussed.

Optimization of the dynamic properties of the ladder track system to control rail vibration using the multipoint approximation method

The combination model of the vehicle and ladder track system that accounts for the wheel–rail interface has been developed to analyze the wheelset and ladder track vibration characteristics in the frequency and time domains. In the wheel–rail interface, the vertical contact is represented by contact stiffness derived from the Hertz theory of normal elastic contact, and lateral contact is idealized by linear contact used Kalker linear rolling contact theory. The considerable noise and vibration frequency of the ladder track is determined by experimental investigation results. Then the effect of the most significant ladder track parameters on the track vibration is analyzed in time domain using the vehicle–track coupling model. Based on the results of the parametric study, an optimization of the mechanical properties of the ladder track to reduce the track vibrations is performed using the multipoint approximation method. The results of the optimization are presented and discussed.

Use of Expanded Olystyrene (EPS) Sub-Base in Railway Track Design

The dynamic behavior such the track structure in high-speed applications has been analyzed using RAIL software (TU Delft). An optimization on material properties of EPS, slab thickness and stiffness of subsoil has been performed. The optimization criteria are minimization of the ‘dead’ weight of a track structure and the costs related to the sub-grade improvement (i.e. the vertical stiffness of the subsoil should be as low as possible) while imposing constraints on the stresses in the EPS and subsoil layers.

Parametric study of wheel transitions at railway crossings

Vehicle–track interaction at railway crossings is complex due to the discontinuity of the crossings. In this study, the effect of the local crossing geometry, the track alignment, and the wheel profiles on the wheel transition behaviour is investigated using the multi-body system software package VI-Rail. The transition behaviour is evaluated based on the location of the transition point along the crossing (and the location of impact), the contact pressure and the energy dissipation during the wheel–rail contact. A detailed parametric study of the crossing geometry has been performed, through which the most effective parameters for defining the crossing geometry are identified. These parameters are the cross-sectional shape of the nose rail, which can be tuned by one variable, and the vertical distance between the top of the wing rail and the nose rail. Additionally, a parametric study on the interaction influence of the crossing geometry, the track alignment and the wheel profile is performed using the design of experiments method with a two-level full factorial design. The longitudinal height profile of the crossing and the wheel profile are the most significant factors.

Analysis of the Dynamic Behaviour of a Railway Track in Transition Zones With Differential Settlement

Transition zones in railway tracks are locations with considerable changes in the vertical stiffness of the rail support. Typically they are located near engineering structures, such as bridges, culverts and tunnels. In such locations, the vertical stiffness of the track support varies, resulting in amplification of the dynamic forces acting on the track, which ultimately leads to deterioration of the vertical track geometry. Also, differential settlement of the track sub-structure on both sides of the transition contributes to the deterioration of the vertical geometry. The deterioration process accelerates with increase of the operational velocities of the passing trains. Finally, all these result in increase of the maintenance efforts on correction of the track geometry in the transition zones.To analyze the dynamic behavior of transition zones due to the differential settlement, a finite element dynamic model (using explicit integration) of a track transition zone is developed. The model is also accounting for the effect of hanging sleepers. The model is verified against the measurement results performed using the Video Gauge System (VGS). With the developed model, the differential settlement of ballast and soil has been introduced and the effects of this settlement on performance of the track are analyzed. The resulting wheel forces and the dynamic responses of the track components are obtained and analyzed. Special attention has been paid on the stresses of ballast, which is one of the most vulnerable track components in the transition zones. Finally, conclusions on the effect of the various internal and external factors on the degradation process of the track in transition zones are drawn. With the developed model, the differential settlement of ballast and soil is induced and hence, the effects of the differential settlements can be analysed. The contact forces of wheel-rail interaction and the dynamic response of track components are obtained and analysed. Special attention has been paid on the stresses of ballast which are one of the most vulnerable components in the track transition zones. Finally, conclusions on the effect of the various internal and external factors on the degradation process of the track in transition zones are drawn.Copyright

Identification of Dynamic Properties of a Railway Track

The paper presents a methodology for assessment of dynamic characteristics of a railway track in application to an Embedded Rail Structure. First, the dynamic responses of a track are obtained using a Hammer Excitation Test (HET) by applying a vertical impulse load to a rail and measuring resulting accelerations of a track. The measured data is then analyzed using the Frequency Response Function (FRF). The hammer test is also simulated by the finite element model (RAIL), which can be used for analysis of the dynamic behavior of a track under various loading. Both HET and RAIL are developed at Delft University of Technology (DUT). To match the simulation and measurement data a numerical optimization technique called a Multipoint Approximation based on Response Surface fitting (MARS) method has been used. The parameters of the model related to the material properties of elastic compound (polyurethane and cork mixture) wherein the rails are embedded have been varied during the identification process. The numerical model with the obtained parameters of compound can then be used for estimation of performance characteristics of the railway track. The compound parameters have been compared with the ones obtained using a single degree of freedom mass-spring system. The results of the identification problems are presented and discussed.