20 research outputs found
Wheelset skid in railway bogies
No full textSkid of wheelsets leads to uncontrolled severe dynamics of bogies including derailment potential and damage to the running surfaces of the wheel and railhead. Simulation of wheelset skid would enhance the understanding of the skid mechanism and improve the level of safety. To effectively simulate bogie skid, the wheelsets should be modelled incorporating pitch degree of freedom. Such a model, based on a fixed inertial frame reference system, has been recently developed by the first author and is used in this paper to examine the skid of a simplified bogie containing two wheelsets and a bogie frame connected through spring-damper system. The current model accepts braking/ traction torque as a primary input and calculates the longitudinal speed profile, acceleration and distance travelled as a natural process. The calculated results have been validated using VAMPIRE where possible. The ability of the current model in predicting lateral dynamics whilst subjected to longitudinal skid is demonstrated through numerical examples – a feature that could not readily be predicted by most commercial wagon dynamics packages
An inertial reference frame method for the simulation of the effect of longitudinal force to the dynamics of railway wheelsets
No full textIn the current practice of wagon dynamics simulation, traction and braking forces are seldom considered although such forces modify the wheel-rail contact parameters and hence the wheelset dynamics. On the other hand, whilst the traction and braking forces are considered in the simulation of train and locomotive systems, their lateral dynamics is predominantly disregarded. Therefore, there exists a gap in the knowledge of the effect of the application of the longitudinal forces to the lateral dynamics of wagons; this paper aims at bridging this gap. An inertial reference frame method available in the literature has been extended for the purpose. This paper reports the formulation and presents numerical examples of a single wheelset contained within a bogie frame subjected to longitudinal forces of varying severity. The results have been validated where possible
Experimental evaluation of the effect of braking torque on bogie dynamics
No full textThis paper reports a full-scale laboratory test carried out for the evaluation of the effect of braking torque on bogie dynamics. Precision instruments have been used as the limited length of the track restricted the operating speed to less than 4m/s. It is shown that by judiciously controlling the brake pressure and its application time, the skid of the braked wheelset could be achieved. The instrumented bogie is shown to possess excellent potential for being used as an onboard system for monitoring the dynamics of cash trains during brake application without the need for a wayside magnetic encoder system
Investigation of the dynamics of railway bogies subjected to traction/braking torque
No full text"The limitations of current simulation packages in addressing the true longitudinal behaviour of railway bogie dynamics during braking/traction has prompted the development of a Rail Bogie Dynamics (RBD) program in this thesis. The RBD program offers novel features for the calculation of the speed profile as a function of the brake torque as well as explicitly determining wheelset angular velocity. With such capability, the speed profile is no longer treated as an input calculated as a priori as required by most of the current simulation systems. The RBD program has been developed using a formulation that includes the wheelset pitch degree of freedom explicitly with a coordinate reference system that is fixed in space and time. The formulation has made the simulation of the bogie dynamics during braking/traction possible in a natural way using the brake/traction torque as the input and the resulting speed profile as the output without any need for working out the speed profile as a priori. Consequently, severe dynamics during braking such as the wheelset skid and the onset of wheel climb derailment can be modelled and critical parameters investigated using the RBD program. The RBD program has been validated, where possible, through a series of simulations using a commercial software package (VAMPIRE). For cases which cannot be simulated by VAMPIRE such as the wheelset skid, a novel experimental program has been designed and commissioned in the Heavy Testing Laboratory of the Central Queensland University as reported in this thesis. One of the possible applications of the RBD program in examining the effect of asymmetric brake shoe force in bogies equipped with one-side push brake shoe arrangement is illustrated in this thesis. It is believed that the model and RBD program will have significant benefit in understanding the true longitudinal behaviour of wagons in suburban passenger trains that operate under braking/ traction torques for most of their travel. Similar studies will also be useful to freight train wagon dynamics during entry and exit of speed restriction zones and tight curves." -- abstract
Simulation of bogie dynamics under heavy braking
No full textThe importance of including the events of braking / traction to the simulation of wagon dynamics is increasingly recognised due to damages caused to running surfaces by these events. To realistically include these events, explicit definition of wheelset pitch degree of freedom in the formulation of the system equation is necessary. This paper presents such a formulation and demonstrates its effectiveness in predicting wheel skid due to heavy braking when the braking force exceeds the adhesion available at the wheel-rail interface. A model of single wheelset bogie and a bogie model containing two wheelsets within a rigid bogie frame are used as illustrative examples. It is shown that the bogie dynamics is affected differently due to sudden heavy braking either at the leading wheelset alone or at both wheelsets simultaneously
Curving Performance Analysis of a Freight Train Transporting 50-Meter-long Rail Using Multibody Dynamics Simulation
No full textLong rails are normally used in highspeed railways to minimize the number of rail joints and the dynamic impact force that follows. However, transporting long rails using a freight train requires multiple wagons for each rail section, presenting potential safety and loading gauge issues, especially when going through curves. Thus, a safety assessment needs to be done prior to actual transport. Computational simulation can be used for preliminary assessment. Finite element analysis can be used to incorporate the flexibility of the rails into the analysis but requires significant manpower and computer power to perform. In this study, an alternative method to model rail flexibility using a multibody approach is presented. The rails are sectioned into multiple rigid bodies along their length and interconnected using rotational joints. The stiffness coefficient of the joints is defined as a function of the actual rail’s physical properties. This modelling technique results in a simplified multibody model that retains the original rail elastic properties. Simulations of the constructed rail model hauled using a freight train were done and the results were compared to on-track test measurements of the same configuration. The comparison generally showed good agreement, showing this modelling technique’s ability and accuracy to simulate the case
Curving Performance Analysis of a Freight Train Transporting 50-Meter-long Rail Using Multibody Dynamics Simulation
No full textLong rails are normally used in highspeed railways to minimize the number of rail joints and the dynamic impact force that follows. However, transporting long rails using a freight train requires multiple wagons for each rail section, presenting potential safety and loading gauge issues, especially when going through curves. Thus, a safety assessment needs to be done prior to actual transport. Computational simulation can be used for preliminary assessment. Finite element analysis can be used to incorporate the flexibility of the rails into the analysis but requires significant manpower and computer power to perform. In this study, an alternative method to model rail flexibility using a multibody approach is presented. The rails are sectioned into multiple rigid bodies along their length and interconnected using rotational joints. The stiffness coefficient of the joints is defined as a function of the actual rail’s physical properties. This modelling technique results in a simplified multibody model that retains the original rail elastic properties. Simulations of the constructed rail model hauled using a freight train were done and the results were compared to on-track test measurements of the same configuration. The comparison generally showed good agreement, showing this modelling technique’s ability and accuracy to simulate the case
RAMS of Railway Infrastructure A Review
No full textRAMS is crucial for assuring the correct functioning of railway transportation, which is a critical mode of transit for both passengers and products. The paper provides a comprehensive overview of the components and theory of RAMS and highlights commonly used methods in each discipline. The benefits and sustainability of RAMS and complementary disciplines such as Life Cycle Cost (LCC) are also discussed. The integration of RAMS and LCC can provide railway companies and passengers with numerous benefits. The RAMS methodology consists of four essential components: availability, maintainability, safety management, and reliability. While implementing RAMS, businesses must consider potential obstacles such as limited data and resources. To foster an environment conducive to RAMS implementation, businesses need government and industry support. Future research must be conducted on optimizing assets across the entire railway system, and RAMS and LCC requirements must be digitized within the asset system
Effect of asymmetric brake shoe force application on wagon curving performance
No full textThis paper reports the effect of asymmetric brake force on wheelsets to the curving performance of freight wagons fitted with three-piece bogies. For the purpose of study a wagon model containing eleven rigid body elements was set up. The non-linear characteristics caused by friction and clearances betweed critical rigid elements are considered in the modelling. The effects of yaw torque (positive and negative) induced by asymmetric brake forces, the wheel profiles, and the friction coefficients on the curving performance of the wagons are examined. The results show that the negative yaw torque potentially deteriorates the curving performance as measured by the increase in the angle of attack and lateral force as well as lateral to vertical force (L/V) ratio
