Train dynamics and component fatigue assessments are important steps towards successful operations of long heavy haul trains. Longitudinal train dynamics (LTD) simulation is an effective and ...efficient approach in this regard. Draft gear friction has been known to have a strong stochastic feature. However, relevant train dynamics simulations have not been reported in open literature. This paper uses experimental data to extract the stochastic feature of draft gear friction. The stochastic feature is then introduced into LTD simulations. Coupler force and fatigue damage assessments were conducted by simulating a heavy haul train that has 244 vehicles and weighs nearly 30,000 tonnes. The results show that average in-train force variations due to stochastic friction were 55 and 40 kN for the traction and air brake cases respectively; maximum force variations were 207 and 98 kN for the traction and air brake cases respectively. Coupler fatigue calculations are even more sensitive to stochastic draft gear friction; the largest variations can be up to 700 times different due to the strong nonlinearity of fatigue calculation procedures. Stochastic friction is an unavoidable nature in friction draft gears. Simulations using stochastic draft gear friction can deliver results that are more robust and reliable.
•Draft gear testing and inversed friction characteristics.•Development of stochastic friction model for railway draft gears.•Coupler force and fatigue assessment using stochastic friction model.
Railway train energy simulation is an important and popular research topic. Locomotive traction force simulations are a fundamental part of such research. Conventional energy calculation models are ...not able to consider locomotive wheel–rail adhesions, traction adhesion control, and locomotive dynamics. This paper has developed two models to fill this research gap. The first model uses a 2D locomotive model with 27 degrees of freedom and a simplified wheel–rail contact model. The second model uses a 3D locomotive model with 54 degrees of freedom and a fully detailed wheel–rail contact model. Both models were integrated into a longitudinal train dynamics model with the consideration of locomotive adhesion control. Energy consumption simulations using a conventional model (1D model) and the two new models (2D and 3D models) were conducted and compared. The results show that, due to the consideration of wheel–rail adhesion model and traction control in the 3D model, it reports less energy consumption than the 1D model. The maximum difference in energy consumption rate between the 3D model and the 1D model was 12.5%. Due to the consideration of multiple wheel–rail contact points in the 3D model, it reports higher energy consumption than the 2D model. An 8.6% maximum difference in energy consumption rate between the 3D model and the 1D model was reported during curve negotiation.
The wear and rolling contact fatigue (RCF) testing approaches for wheels and rails have been reviewed and evaluated in this study. The study points out the advantages and limitations of the existing ...approaches. The broad analysis revealed that scaled laboratory-based wear testing is widely applied. However, it is necessary to predetermine the input parameters and observing parameters for scaled wear testing for three reasons: first, to emulate the real-world scenarios as closely as possible; second, to postprocess the results received from the scaled testing and transfer them into real practice at full scale; third, to present the results in a legible/appropriate format. Therefore, most of the important parameters required for wear testing have been discussed with fundamental and systematic explanations provided. Additionally, the transition of the parameters from the real-world into the test domain is explained. This study also elaborates on the challenges of the RCF and wear testing processes and concludes by providing major considerations toward successful testing.
The production–inventory system is a problem of multivariable input and multivariant output in mathematics. Selecting the best system control parameters is a crucial managerial decision to achieve ...and dynamically maintain an optimal performance in terms of balancing the order rate and stock level under dynamic influence of many factors affecting the system operations. The dynamic performance of the popular APIOBPCS model and the newly modified 2APIOBPCS model for optimal control of production–inventory systems is examined in the study. This examination is based on the leveled ground with a new simulation scheme that incorporates a designated multi-objective particle swarm optimization (MOPSO) algorithm into the simulation, which enables the optimal set of system control parameters to be selected for achieving the situational best possible performance of the production–inventory system under study. The dynamic performance is measured by the variance ratio between the order rate and the sales rate related to the bullwhip effect, and the integral of absolute error related to the inventory responsiveness in response to a random customer demand. Our simulation indicates that the 2APIOBPCS model performed better than or at least no worse than, and more robust than the APIOBPCS model under different conditions.
The design of mechatronic systems for rail vehicles requires the implementation of modern software tools. Nowadays, it is common to use co-simulation for the creation of mechatronic models. This ...approach is usually based on the combination of two types of software - multi-body simulation packages for mechanical models and tools for simulation of electric, control systems, etc. The existing commercial codes (SIMPACK, VI-RAIL, VAMPIRE, UM) provide different approaches for co-simulation; however, they have a lot in common. The one thing that makes them very similar is the use of Simulink for co-simulation. In this paper, we propose a description of the client interface in Simulink for co-simulation with Gensys. The evolution of the proposed approach has been performed by means of a simulation of a simplified traction control system for a hauling locomotive running on straight track conditions.
Given the constant demand for heavier, longer, faster, and more efficient rail freight vehicles, onboard fault detection systems appear as a good approach for enhanced railway asset exploitation. ...Real-time condition monitoring reduces inefficient preventive and reactive maintenance actions, decreases waste from replacing parts that still have a useful life, and improves availability and safety by real-time rolling stock diagnosis. There have been considerable advances in wayside monitoring applications, but these cannot achieve real-time continuous monitoring. With the price reduction and miniaturization trends of electronic devices, the cost of deploying wireless sensor networks onboard freight trains continues to become more feasible and accessible. On the other hand, the lack of onboard electric power availability on freight wagons appears as the major limitation for the implementation of these technologies. This paper reviews recent onboard condition monitoring sensors, systems, methods and techniques, aiming to define the present state of the art and its potential application for freight wagons without onboard electric power.
The safety and stability of freight train operations are closely related to the wheel–rail contact dynamic forces. To evaluate and monitor the wheel–rail dynamic forces based on the accelerations on ...the wagon components, a two-dimensional inverse wagon model has been developed. To verify the inverse modelling, a detailed VAMPIRE wagon model has been used for the simulations on two cases of track rail top surface and cross-level irregularities. The simulated accelerations on wagon components are then the inputs into the inverse wagon model. Reasonable agreement has been achieved in the comparison between the predicted and simulated primary and secondary suspension forces and wheel–rail contact forces. The inverse wagon model is finally simplified into a one-dimensional vertical model for potential online applications. The predicted and simulated wheel–rail contact dynamic forces are also compared due to the random track geometry irregularities.
A rail vehicle-track interaction dynamics model has been applied to determine the track vertical dynamic forces due to rail shortwavelength dip defects such as squat, dip joints and welds, etc., ...which are required in both rail vehicle acceptance procedure and track maintenance. The model is validated using the field measurement data of rail squat defects and accelerations on a vehicle axlebox. The simulated track dynamic forces — the P
2
forces due to rail dipped joints have been compared with those calculated by using a well-known formula. The results are compared and the formula’s limitations have been discussed. The dependence of the track vertical dynamic forces on the rail dip defect size and vehicle speed has also been investigated.
Longitudinal train dynamics: an overview Wu, Qing; Spiryagin, Maksym; Cole, Colin
Vehicle system dynamics,
12/1/2016, 2016-12-00, 20161201, Letnik:
54, Številka:
12
Journal Article
Recenzirano
This paper discusses the evolution of longitudinal train dynamics (LTD) simulations, which covers numerical solvers, vehicle connection systems, air brake systems, wagon dumper systems and ...locomotives, resistance forces and gravitational components, vehicle in-train instabilities, and computing schemes. A number of potential research topics are suggested, such as modelling of friction, polymer, and transition characteristics for vehicle connection simulations, studies of wagon dumping operations, proper modelling of vehicle in-train instabilities, and computing schemes for LTD simulations. Evidence shows that LTD simulations have evolved with computing capabilities. Currently, advanced component models that directly describe the working principles of the operation of air brake systems, vehicle connection systems, and traction systems are available. Parallel computing is a good solution to combine and simulate all these advanced models. Parallel computing can also be used to conduct three-dimensional long train dynamics simulations.
The feasibility of monitoring the dipped rail joint defects has been theoretically investigated by simulating a locomotive-mounted acceleration system negotiating several types of dipped rail ...defects. Initially, a comprehensive locomotive-track model was developed using the multi-body dynamics approach. In this model, the locomotive car-body, bogie frames, wheelsets and driving motors are considered as rigid bodies; track modelling was also taken into account. A quantitative relationship between the characteristics (peak–peak values) of the axle box accelerations and the rail defects was determined through simulations. Therefore, the proposed approach, which combines defect analysis and comparisons with theoretical results, will enhance the ability for long-term monitoring and assessment of track systems and provides more informed preventative track maintenance strategies.
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