Dynamic Performance of a Bulkhead Flat Car

The dynamic performance of a flat car is studied herein. The performance indices include roll angles, lateral accelerations, center plate loads, side bearing loads, wheel loads and spring deflections. These variables are maximum when the car is running at its critical speed, corresponding to either the rock and roll, or the bounce mode. The Association of American Railroads' (AAR) Flexible Carbody Model was used. The input for vertical track irregularities used in the simulation was generated from published spectra for U.S. Federal Railroad Administration (FRA) Class 4 track. After studying the car's performance with various column loads and spring suspensions, it was found that the most commonly used column load of 4,000 lbs. (17.8 kN) should be used. The spring suspension used in the original car design should also be adopted, in order to avoid spring. bottoming.     

Dynamic Performance of a Bulkhead Flat Car

The dynamic performance of a flat car is studied herein. The performance indices include roll angles, lateral accelerations, center plate loads, side bearing loads, wheel loads and spring deflections. These variables are maximum when the car is running at its critical speed, corresponding to either the rock and roll, or the bounce mode. The Association of American Railroads' (AAR) Flexible Carbody Model was used. The input for vertical track irregularities used in the simulation was generated from published spectra for U.S. Federal Railroad Administration (FRA) Class 4 track. After studying the car's performance with various column loads and spring suspensions, it was found that the most commonly used column load of 4,000 lbs. (17.8 kN) should be used. The spring suspension used in the original car design should also be adopted, in order to avoid spring bottoming.     

The Influence of Tire Factors on the Stability of Trucks and Tractor Trailers

SUMMARY

The mechanical properties of tires and trucks are contrasted with comparable properties of the motor car to explain why the motor truck and the tractor-trailer can exhibit fixed-control instability at moderate levels of lateral acceleration. The (1) rearward bias in the distribution of roll stiffness, (2) large ratio of e.g. height to track, and (3) low torsional stiffness of the parallel-rail frame (as typically employed in heavy commercial vehicles) are found to be the major factors implicated in this phenomenon. Experimental and analytical evidence is provided to show how tire inflation pressure and mixes of (a) tire-carcass construction and (b) tread design also influence stability at moderate levels of lateral acceleration. Conclusions relating to the safety of commercial vehicle operations are drawn.     

An Evaluation of Passive Automotive Suspension Systems with Variable Stiffness and Damping Parameters

SUMMARY

Passenger discomfort, suspension working space and dynamic tyre loading parameters are calculated for different combinations of spring stiffness and damping coefficient representing the suspension system in a quarter car model subject to realistic random disturbance inputs from roads of widely differing quality. Sprung and unsprung masses and the tyre vertical stiffness and damping coefficient employed derive from a current production car. Designs which are best for the specific conditions represented are identified and their performance properties in other (off-design) conditions are considered, and conventional design is explained as the inevitable consequence of the need to compromise if fixed suspension parameters are used. Performance improvements possible if variable parameters can be employed are evaluated as a function of the ranges of variability provided, and a stratagem for controlling parameters is proposed.     

Steady-State Curving Performance of Railway Freight Truck with Damper-Coupled Wheelsets

SUMMARY

The focus of this paper is on the steady-state curving behaviour of a freight car system with Damper Coupled Wheelset (DCW), where the wheels of conventional shape within an axle are coupled through a damper element. A freight truck model with two DCW and pseudo-car body on curved track is developed to study the influence of wheelset coupler parameter on the curving response and performance. The response is primarily evaluated in terms of wheelset tracking error and yaw misalignment in response to track curvature and cant deficiency. The curving performance is evaluated in terms of slip and flange boundaries. The results in general, indicate that when the value of coupler parameter is reduced, the wheelset response to track curvature increases, and results in flanging and wheel slip on a less tighter curve than those corresponding to conventional rigid axled wheelsets.     

Black-box modelling of nonlinear railway vehicle dynamics for track geometry assessment using neural networks

ABSTRACT

The use of vehicle dynamics simulation for the track geometry assessment gives rise to new demands. In order to analyse the responses of the vehicles to the measured track geometry defects, the integration of the simulation process in the measurement chain of the track geometry recording car is envisaged. Fast and reliable simulation results are required. This work studies the use of black-box modelling approaches as an alternative to multi-body simulation. The performances of different linear and nonlinear black-box models for the simulation of the vertical and lateral bogie accelerations are compared. While linear transfer function models give good results for the simulation of the vertical responses, their use is not suitable for the highly nonlinear lateral vehicle dynamics. The lateral accelerations are best represented by recurrent neural networks. For the training and validation on high-speed lines using measured vehicle responses, the performance of the black-box simulation outperforms the multi-body simulation. Due to the larger variability of track design and track quality conditions on conventional lines, the model performance degrades and depends significantly on the analysed vehicle type and the track characteristics.     

Dynamic vehicle–track interaction in switches and crossings and the influence of rail pad stiffness – field measurements and validation of a simulation model

A model for simulation of dynamic interaction between a railway vehicle and a turnout (switch and crossing, S&C) is validated versus field measurements. In particular, the implementation and accuracy of viscously damped track models with different complexities are assessed. The validation data come from full-scale field measurements of dynamic track stiffness and wheel–rail contact forces in a demonstrator turnout that was installed as part of the INNOTRACK project with funding from the European Union Sixth Framework Programme. Vertical track stiffness at nominal wheel loads, in the frequency range up to 20?Hz, was measured using a rolling stiffness measurement vehicle (RSMV). Vertical and lateral wheel–rail contact forces were measured by an instrumented wheel set mounted in a freight car featuring Y25 bogies. The measurements were performed for traffic in both the through and diverging routes, and in the facing and trailing moves. The full set of test runs was repeated with different types of rail pad to investigate the influence of rail pad stiffness on track stiffness and contact forces. It is concluded that impact loads on the crossing can be reduced by using more resilient rail pads. To allow for vehicle dynamics simulations at low computational cost, the track models are discretised space-variant mass–spring–damper models that are moving with each wheel set of the vehicle model. Acceptable agreement between simulated and measured vertical contact forces at the crossing can be obtained when the standard GENSYS track model is extended with one ballast/subgrade mass under each rail. This model can be tuned to capture the large phase delay in dynamic track stiffness at low frequencies, as measured by the RSMV, while remaining sufficiently resilient at higher frequencies.     

Ride Vibration Measurements of Agricultural Tractor and Trailer Combinations

SUMMARY

Tractor ride vibration levels have been measured when operating with and without a two wheel (2W) unbalanced and a four wheel (4W) balanced trailer. Measurements were made in the vertical, pitch, longitudinal and roll directions with the trailers unladen and laden over four typical farm surfaces

The results showed that tractor ride vibration levels were usually increased in all directions-particularly the longitudinal direction- when operating with the laden trailers. But for the unladen trailers, they were increased only in the longitudinal direction. Predominant tractor frequencies tended to be lower with the trailers attached, and coupling between the tractor longitudinal, vertical, roll and pitch co-ordinates was generally increased

Comparisons of the results with the trends predicted by a simplified theoretical model of a tractor and 2W trailer, suggested that the model should be extended to include, (a) the roll direction, (b) more realistic ground inputs, and (c) a 4W trailer     

Development and Evaluation of Vehicle Simulation Models for a 4WS Application

SUMMARY

In the scope of the European Prometheus project a passenger car with active rear wheel steering was developed by TNO in cooperation with PSA. During development and engineering of the rear wheel steering system simulation tools have been used to reduce development costs. This paper describes the evaluation of different simulation models, from simple to complex, with results of full vehicle driving tests. The optimal balance for model complexity and accuracy was achieved with a 2-dimensional model with an added roll degree of freedom. The results show that validation using time responses can give ambiguous and inaccurate results, and that frequency response functions are much more usable in validation.     

Roll Plane Analysis of Articulated Tank Vehicles During Steady Turning

SUMMARY

The rollover immunity levels of articulated tank vehicles with partial loads are investigated. A static roll plane model of the articulated vehicle employing partially filled cylindrical tank is developed. The vertical and lateral translation of the liquid cargo due to vehicle roll angle and lateral acceleration, encountered during steady turning, are evaluated. The roll moments arising from vertical and lateral translation of the liquid cargo are determined and incorporated in the roll plane model of the vehicle. The adverse influence of the unique interactions of the liquid within the tank vehicle, on the rollover limit of the articulated vehicle is demonstrated. The influence of compartmenting of the tank on the steady turning roll response of the vehicle is analyzed, and an optimal order of unloading the compartmented tank is discussed.     

Dynamic Response of a Six-axle Locomotive to Random Track Inputs

SUMMARY

Spectral analysis techniques are employed to analyze the dynamic response of a six-axle locomotive on tangent track to vertical and lateral random track irregularities. The locomotive is represented by a thirty-nine (39) degrees of freedom model. A linear model is employed by considering small displacements, linear suspension elements and a linear theory for the wheel-rail interaction. Power spectral densities of displacements, velocities and accelerations and the statistical average frequencies of the system are obtained for each degree of freedom. Comparison of the calculated dominating frequencies with existing experimental values shows good agreement. The technique of spectral analysis is an effective tool for model validation, and for the determination of rail vehicle response to track irregularities. The probability functions for the response can be used as a measure for the ride quality of rail vehicles and for the study of fatigue damage of components.

     

Lateral Vibration of Railway Bridge-Vehicle System Caused by Track Irregularities

SUMMARY

The lateral vibration of the bridge-vehicle system caused by track irregularities is investigated in this paper by means of frequency spectral analysis method. A railway cable-stayed bridge is taken as the model to study, on which a theoretical analysis is made to compare with the practical results measured. The method proves to be feasible. Then it is applied to studying the interaction between a long-span railway cable-stayed bridge and a freight car as well as the effect of track irregularities on the dynamic characteristics of the bridge-vehicle system, thus leading to a couple of conclusions of considerable significance.     

Optimization of Vehicles Elasto-Damping Elements Characteristics from the Aspect of Ride Comfort

SUMMARY

Spatial random vibrations of a vehicle that arise during driving represent an important factor in functioning of a dynamic system: Driver - Vehicle - Environment. They carry certain information for driver and also cause fatigue of driver and passenger.

This is the reason why the tendency is towards the minimization of vibratory loads, what in practice can be achieved by optimization of characteristics of elasto - damping elements of a vehicle.

In this paper for optimization of elasto - damping elements of a vehicle we used a complex nonlinear model of a driver and a vehicle during the straight - line motion of the vehicle on a rough road. Optimization was performed by application of the Hooke - Jeeves method and by use of outside penalty functions as well as the objective function that enabled simultaneous optimization of vertical vibrations of the driver's seat, vibrations of the steering wheel, and normal reactions in the contact surface of the tyre and road. The optimization was performed with application of the computer HP 9000/800 SE on the example of a medium passenger car.     

Development of aerodynamics for a solar race car

The dominant factor of a solar car is running resistance, especially aerodynamic drag; and the reduction of the C_D (drag coefficient)× A (frontal projected area) value is a crucial task to maximize the performance of a solar car. This paper will introduce the aerodynamic approach of the '96 Honda solar car which participated in the World Solar Challenge, the world's top solar car race.     

Anti-Roll and Active Roll Suspensions

Full car roll model is used to show an anti-roll control like that in Citroen's Xantia Activa and the proposed active roll with an in-series active suspension. Computed responses to pulse-shaped anti-phase road unevenness as well as to lateral acceleration in comparison with passive suspension are given in the paper. Also stability values for all parameters can be found.     

Simulation of Bending-Torsional-Lateral Vibrations of the Railway Wheelset-Track System in the Medium Frequency Range

SUMMARY

In the present paper, the dynamic interaction between a wheelset of a high-speed-train car and a railway track is considered with the help of a discrete-continuous mechanical model. This model enables us to investigate the bending-torsional-axial vibrations of the wheelset coupled with the vertical and lateral vibrations of the track through the wheel-rail contact forces. The results of numerical simulations performed for the wheelset motion both on straight and curved tracks demonstrate qualitative similarities of the corresponding dynamic responses of the system and essential quantitative differences of the respective amplitude and average values. Particularly severe interaction between the wheelset and the track is observed in the form of periodic resonances caused by parametric excitation from the track.     

Properties of Non-Linear Two-Force Elements Used in Vehicle Dynamic Systems under Stationary Stochastic Excitation. Part 2 - Realistic Complex Elements

SUMMARY

Realistic two-force elements used in vehicle dynamic systems have very often complex output force -inputs relations. Determination of their properties under stationary stochastic excitation must be therefore carried out experimentally for every excitational case. Evaluation of the measurements of one type of a passenger car telescopic hydraulic suspension damper and of one type of a heavy duty truck leaf spring is shown in this part of the paper. Transfers of the discussed elements, representing the frequency responses of the elements to the input deflectional process and defined in the first part of this paper, form the base for the evaluation.     

Lateral Dynamics of Commercial Vehicle Combinations A Literature Survey

SUMMARY

This paper presents a review of theoretical and experimental works relative to the handling performance of commercial vehicle combinations. A commercial vehicle combination (road train) is defined as a tractor unit and an arbitrary number of trailers. The review contains literature corresponding the most widely used types of trains: tractor-semitrailer, truck-trailer and tractor-semitrailer-semitrailer (doubles). The vehicle dynamic performance has been investigated taking into consideration the following features: directional performance, roll dynamics, braking performance and combined braking and directional performance. With the aim of evaluating the present state of research activities in the field of lateral dynamics of articulated commercial vehicles, the author has compiled some 250 references.     

Influence of long-wavelength track irregularities on the motion of a high-speed train

Vertical track irregularities over viaducts in high-speed rail systems could be possibly caused by concrete creep if pre-stressed concrete bridges are used. For bridge spans that are almost uniformly distributed, track irregularity exhibits a near-regular wave profile that excites car bodies as a high-speed train moves over the bridge system. A long-wavelength irregularity induces low-frequency excitation that may be close to the natural frequencies of the train suspension system, thereby causing significant vibration of the car body. This paper investigates the relationship between the levels of car vibration, bridge vibration, track irregularity, and the train speed. First, this study investigates the vibration levels of a high-speed train and bridge system using 3D finite-element (FE) transient dynamic analysis, before and after adjustment of vertical track irregularities by means of installing shimming plates under rail pads. The analysis models are validated by in situ measurements and on-board measurement. Parametric studies of car body vibration and bridge vibration under three different levels of track irregularity at five train speeds and over two bridge span lengths are conducted using the FE model. Finally, a discontinuous shimming pattern is proposed to avoid vehicle suspension resonance.