2,656 research outputs found
Reply to comments on ‘The Kalker book of tables for non-Hertzian contact of wheel and rail’ by E. A. H. Vollebregt
No full textThe influence of the non-Hertzian wheel-rail contact to the dynamics of a rail vehicle in multibody simulation
No full textEffects of conformal wheel/rail contact modelling on the dynamic responses of a wheelset
No full textThis paper investigates the effects of conformal wheel/rail contact modelling on the dynamic responses of a wheelset through a series of specially designed benchmark exercises. Five contact models were used: DynaRail, basic and advanced approaches in Simpack, and two approaches in CONTACT, implemented online in multibody simulation. Despite the difference in the representation of wheel/rail contact, the models produced comparable results regarding the overall system behaviour under low conformal contact conditions. Significant variations were observed in contact-related output channels. These findings suggest that while overall forces for conformal contacts can be approximated reasonably well using a proper planar contact model, more substantial differences are obtained in local outcomes. These discrepancies, particularly in the stress distribution, have critical implications for the simulation of wear and damage phenomena
Dynamic analysis of locomotive-roller rig coupled system
No full textThis paper presents a mathematical model of a locomotive-roller rig coupled system. The complete model consists of the mechanical unit of the locomotive and roller rig, which is modelled as a multibody system in SIMPACK, and of a model of the locomotive and roller traction system control unit, which is defined in Simulink. These two units are connected by means of co-simulation. The present paper focusses on the modelling of the mechanical unit and roller rig control system, and on the comparison of simulated and experimental results. The influence of the top inclination of the roller (representing rail inclination) on the running stability of the tested locomotive on the roller rig has been investigated with the developed model. The simulation results show that the developed model is able to reproduce the dynamic behaviour of the roller rig system, therefore, it will be helpful for explaining the experimental results, optimizing the test plans and the operation of the test rig. Furthermore, the model will be used for developing the control strategy for the traction system in the next phase of the project
The Kalker book of tables for non-Hertzian contact of wheel and rail
No full textA new regularisation of non-elliptical contact patches has been introduced, which enables building the look-up table called by us the Kalker book of tables for non-Hertzian contact (KBTNH), which is a fast creep force generator that can be used by multibody dynamics system simulation programs. The non-elliptical contact patch is regularised by a simple double-elliptical contact region (SDEC). The SDEC region is especially suitable for regularisation of contact patches obtained with approximate non-Hertzian methods for solving the normal contact problem of wheel and rail. The new regularisation is suitable for wheels and rails with any profiles, including worn profiles. The paper describes the new procedure of regularisation of the non-elliptical contact patch, the structure of the Kalker book of tables, and parameterisation of the independent variables of the tables and creep forces. A moderate volume Kalker book of tables for SDEC region suitable for simulation of modern running gears has been computed in co-simulation of Matlab and program CONTACT. To access the creep forces of the Kalker book of tables, the linear interpolation has been applied. The creep forces obtained from KBTNH have been compared to those obtained by program CONTACT and FASTSIM algorithm. FASTSIM has been applied on both the contact ellipse and the SDEC contact patch. The comparison shows that KBTNH is in good agreement with CONTACT for a wide range of creepage condition and shapes of the contact patch, whereas the use of FASTSIM on the elliptical patch and SDEC may lead to significant deviations from the reference CONTACT solutions. The computational cost of calling creep forces from KBTNH has been estimated by comparing CPU time of FASTSIM and KBTNH. The KBTNH is 7.8–51 times faster than FASTSIM working on 36–256 discretisation elements, respectively. In the example of application, the KBTNH has been applied for curving simulations and results compared with those obtained with the creep force generator employing the elliptical regularisation. The results significantly differ, especially in predicted creepages, because the elliptical regularisation neglects generation of the longitudinal creep force by spin creepage
Mechatronic system simulation of a full scale roller rig for a single wheelset
No full textA complete numerical model of a full scale roller rig mechatronic system is proposed in this paper. It is composed of a multi-body system model of the roller rig, interfaced with a model of the motor driving the roller and of the control unit substructures. Based on the mechatronic system model a method to derive the control signals for the control unit to perform the test is proposed. The simulation results show that this approach enables the actual behaviour of the wheelset in the line to be closely reproduced. However, non-negligible differences are observed in the running behaviour of the wheelset tested on the roller, compared with the same wheelset in the line. The reasons are discussed in the paper and are ascribed mainly to differences in the longitudinal creepage, in the related creep forces and in the gravitational terms involved with the lateral motion of the wheelset. Based on the results presented, a preliminary discussion of the best strategies for roller rig testing is provided
Effects of Non-Hertzian Contact Models on Derailment Simulation
No full textThe derailment of trains is a complex phenomenon that requires an elaborate contact model in simulation to better understand its mechanism. The CONTACT program is a well-known reference for wheel-rail contact modeling due to its high accuracy. However, its low computational efficiency restricts its applications especially in the context of a multi-body simulation. Therefore, a high computational efficient, simplified and approximate non-Hertzian contact is preferred in derailment simulation. The aim of this research is to verify the efficiency of a recently developed non-Hertzian wheel-rail contact model in derailment simulation, which is a combination of the Kik-Piotrowski model and the KBTNH that is a fast creep force solver for non-Hertzian contacts. To assess the performance of the non-Hertzian model in derailment simulation, the derailment coefficient for steady-state and quasi-steady conditions, the wheel/rail contact forces during flange contact, and the dynamics behaviors of the wheelset prior to the derailment are compared with the state of the art contact methods representing different levels of modeling complexity, accuracy and efficiency, namely the classical approach (Hertz theory+FASTSIM algorithm) and the 'exact' solver CONTACT
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