1,721,066 research outputs found
Effects 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
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
A non-Hertzian method for solving wheel–rail normal contact problem taking into account the effect of yaw
No full textA novel approach is proposed in this paper to deal with non-Hertzian normal contact in wheel–rail interface, extending the widely used Kik–Piotrowski method. The new approach is able to consider the effect of the yaw angle of the wheelset against the rail on the shape of the contact patch and on pressure distribution. Furthermore, the method considers the variation of profile curvature across the contact patch, enhancing the correspondence to CONTACT for highly non-Hertzian contact conditions. The simulation results show that the proposed method can provide more accurate estimation than the original algorithm compared to Kalker’s CONTACT, and that the influence of yaw on the contact results is significant under certain circumstances
Assessment of Simplified Models of Conformal Wheel-Rail Rolling Contact
No full textNon-conformal contact models may be inadequate for solving conformal contact problems because the assumption of the flatness of the contact patch is violated in the context of conformal contacts. Although the finite element method and boundary element method with proper modifications can be used to solve conformal contact problems, their computational efficiency limits their application. To strike a balance between efficiency and accuracy, simplified conformal contact models are preferred options. Three simplified conformal contact models have been implemented based on the modified version of the Kik-Piotrowski model, INFCON model combined with FASTSIM, and FaStrip. These models are assessed through the comparisons with results from a detailed model in terms of the contact size, shape, normal pressure, tangential stress, resultant forces, and computational efficiency. The comparative analysis of two case studies shows that the non-conformal contact model produces considerable differences from the conformal models. Among the evaluated models, the adapted Kik-Piotrowski combined with FASTSIM is the fastest, while under certain conditions its accuracy is lower than the modified INFCON + FASTSIM/FaStrip models which show overall better agreement with the reference
A fast method for determination of creep forces in non-Hertzian contact of wheel and rail based on a book of tables
Get PDFThe Kalker book of tables for non-Hertzian contact described in a previous work from the authors provides creep forces, but the moment generated in the contact patch is not available. The extended Kalker book of tables for non-Hertzian contact (KBTNH) presented in this paper provides creep forces, as well as the moment. The paper presents the simplified linear theory of rolling contact for a simple double-elliptical contact (SDEC) region used for regularisation of contact patches and, resulting from this theory, the full symmetry relations for creep forces and moment. The parameterisation of variables and structure of the extended book of tables are described. The extended Kalker book of tables of moderate volume has been computed in co-simulation Matlab-CONTACT. The creep forces and moment obtained from KBTNH have been compared to those obtained directly by CONTACT program and FASTSIM algorithm. The comparison shows that KBTNH is in good agreement with CONTACT for a wide range of creepage conditions and shapes of the contact patch, whereas the use of FASTSIM may lead to significant deviations from the reference CONTACT solutions. The presented example of application is a realistic case of a freight wagon curving simulation, where KBTNH has been used to assess the contribution of the moment into the unit frictional work dissipated in contacts of wheels and rails. The high calculation speed and good accuracy of determining creep forces for non-Hertzian wheel–rail contact make the proposed method a suitable tool for multibody system (MBS) simulation programs oriented for rail vehicle dynamics
Application of Non-Hertzian Creep Force Models in Rail Vehicle Dynamics Simulation
No full textIn this paper, two commonly used creep force algorithms in rail vehicle dynamics simulation, namely FASTSIM and Shen-Hedrick-Elkins, are extended to solve non-Hertzian wheel/rail contact problems based on the SDEC regularisation of non-Hertzian contact patches. The extended algorithms for non-Hertzian conditions have been implemented as user routines in Simpack which enables the assessment of the influence of the extended force models on the rail vehicle dynamics through comparison to the traditional Hertzian models in the same environment. To this end, a single wheelset and a complete rail vehicle model are selected as case studies to demonstrate the application of the developed non-Hertzian creep force models in rail vehicle dynamics simulations, and its impact is studied by comparative analysis of the simulation results obtained from using both Hertzian and non-Hertzian models. The results suggest that the Hertzian and non-Hertzian creep force models result in different dynamic behaviours of the system and the level of difference can be significant in a certain context which may cause different conclusions on the assessment of the system, for instance in view of vehicle homologation
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