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Author

J. K. Hedrick

Bio: J. K. Hedrick is an academic researcher from Massachusetts Institute of Technology. The author has contributed to research in topics: Suspension (vehicle) & Ride quality. The author has an hindex of 6, co-authored 10 publications receiving 537 citations.

Papers
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Journal ArticleDOI
TL;DR: In this paper, a comparison of alternative Creep Force Models for rail vehicle dynamic analysis is presented, and the results show that the alternative models are less accurate than the original models in terms of acceleration and acceleration.
Abstract: (1983). A Comparison of Alternative Creep Force Models for Rail Vehicle Dynamic Analysis. Vehicle System Dynamics: Vol. 12, No. 1-3, pp. 79-83.

459 citations

Journal ArticleDOI
TL;DR: In this article, the state-of-the-art of active suspensions for railway vehicles is reviewed, both vertical and lateral, and the primary focus is on ride quality control.
Abstract: SUMMARY This paper reviews the state-of-the-art of active suspensions for use on railway vehicles. The primary focus of the paper is on ride quality control, both vertical and lateral, and on lateral stability control. The section on theoretical considerations summarizes the results of a one-degree of freedom optimization and then investigates analytically the use of active suspensions for lateral ride and stability augmentation. It is shown that separate control structures using different measurements and actuator actions are very effective in controlling both ride quality and stability. A section on a survey ofcurrent activities reviews published research on active railway suspension work around the world. Finally a concluding section indicates future trends in active suspension applications.

44 citations

Journal ArticleDOI
TL;DR: In this article, a forced steering rail vehicle employs linkages between the carbody and wheelsets to force a more radial wheelset alignment, and the curve negotiation capability of forced steering trucks is significantly improved over conventional and self-steered radial trucks.
Abstract: SUMMARY A forced steering rail vehicle employs linkages between.the carbody and wheelsets to force a more radial wheelset alignment. It is shown that the curve negotiation capability of forced steering trucks is significantly improved over conventional and self steering radial trucks. Parametric curves are presented showing angle-of-attack and lateral flange force as a function of steering gain parameters and truck bending stiffness. It is also shown that the forced steering concept can produce kinematic instability and severely reduced critical speeds for low conicities and creep coefficients. Analytic expressions are derived that illustrate how these kinematic instabilities can be avoided.

33 citations

Journal ArticleDOI
TL;DR: In this paper, a seven degree-of-freedom vehicle model incorporating a fully interconnected active suspension is developed, and the model is used to analyze the effect of coupling and absolute damping on sprung mass isolation, as well as tire normal load distribution.
Abstract: SUMMARY A seven degree-of-freedom vehicle model, incorporating a fully interconnected active suspension is developed. The model is used to analyze the effect of coupling and of absolute damping on sprung mass isolation, as well as tire normal load distribution. A parametric study shows that when absolute damping is used, decoupling the heave and pitch body modes both improves body isolation, and reduces fore-aft tire load transfer. However, absolute body roll damping, while improving body isolation, increases the effect of road disturbances on lateral load transfer distribution.

30 citations

Journal ArticleDOI
TL;DR: In this article, the effect of wheel and/or rail lubrication in reducing wheel/rail wear rates was evaluated by steady-state curving calculations of a freight car model with conventional and radial trucks.
Abstract: SUMMARY The effect of wheel and/or rail lubrication in reducing wheel/rail wear rates is evaluated by steady-state curving calculations of a freight car model with conventional and radial trucks. Numerical results indicate that for curves with radii less than 400m, rail lubrication is necesary and the wheel/rail wear rates may be reduced to 1/2.5 of that without lubrication.

7 citations


Cited by
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Journal ArticleDOI
TL;DR: In this article, a three-dimensional vehicle-track coupled dynamics model is developed in which a typical railway passenger vehicle is modelled as a 35-degree-of-freedom multi-body system.
Abstract: This paper presents a framework to investigate the dynamics of overall vehicle-track systems with emphasis on theoretical modelling, numerical simulation and experimental validation. A three-dimensional vehicle-track coupled dynamics model is developed in which a typical railway passenger vehicle is modelled as a 35-degree-of-freedom multi-body system. A traditional ballasted track is modelled as two parallel continuous beams supported by a discrete-elastic foundation of three layers with sleepers and ballasts included. The non-ballasted slab track is modelled as two parallel continuous beams supported by a series of elastic rectangle plates on a viscoelastic foundation. The vehicle subsystem and the track subsystem are coupled through a wheel-rail spatial coupling model that considers rail vibrations in vertical, lateral and torsional directions. Random track irregularities expressed by track spectra are considered as system excitations by means of a time-frequency transformation technique. A fast explicit integration method is applied to solve the large nonlinear equations of motion of the system in the time domain. A computer program named TTISIM is developed to predict the vertical and lateral dynamic responses of the vehicle-track coupled system. The theoretical model is validated by full-scale field experiments, including the speed-up test on the Beijing-Qinhuangdao line and the high-speed running test on the Qinhuangdao-Shenyang line. Differences in the dynamic responses analysed by the vehicle-track coupled dynamics and by the classical vehicle dynamics are ascertained in the case of vehicles passing through curved tracks.

620 citations

Journal ArticleDOI
TL;DR: A review of dynamic modelling of railway track and of the interaction of vehicle and track at frequencies which are sufficiently high for the track's dynamic behaviour to be significant is presented in this paper.
Abstract: A review is presented of dynamic modelling of railway track and of the interaction of vehicle and track at frequencies which are sufficiently high for the track's dynamic behaviour to be significant. Since noise is one of the most important consequences of wheel/rail interaction at high frequencies, the maximum frequency of interest is about 5kHz: the limit of human hearing. The topic is reviewed both historically and in particular with reference to the application of modelling to the solution of practical problems. Good models of the rail, the sleeper and the wheelset are now available for the whole frequency range of interest. However, it is at present impossible to predict either the dynamic behaviour of the railpad and ballast or their long term behaviour. This is regarded as the most promising area for future research.

615 citations

Journal ArticleDOI
Oldrich Polach1
01 Mar 2005-Wear
TL;DR: In this article, the authors present a method to simulate various real wheel-rail contact conditions using one parameter set, which can be identified from measurements or the recommended parameters for modelling of typical wheel rail contact conditions in engineering applications.

425 citations

Journal ArticleDOI
29 May 2013
TL;DR: In this paper, the authors present a framework to systematically investigate the high-speed train-track-bridge dynamic interactions, aiming to provide a method for analysing and assessing the running safety and the ride comfort of trains passing through bridges.
Abstract: This paper presents a framework to systematically investigate the high-speed train–track–bridge dynamic interactions, aiming to provide a method for analysing and assessing the running safety and the ride comfort of trains passing through bridges, which are critically important for the design of new high-speed railway bridges. Train–track–bridge interactive mechanism is illustrated. A fundamental model is established for analysing the train–track–bridge dynamic interactions, in which the vehicle subsystem is coupled with the track subsystem through a spatially interacted wheel–rail model; and the track subsystem is coupled with the bridge subsystem by a track–bridge dynamic interaction model. Modelling of each subsystem and each interactive relationship between subsystems are presented. An explicit–implicit integration scheme is adopted to numerically solve the equations of motion of the large non-linear dynamic system in the time domain. Computer simulation software named the train–track–bridge interacti...

289 citations

Journal ArticleDOI
20 Dec 2006-Wear
TL;DR: In this article, a wheel wear prediction model is developed to predict the wheel profile evolution due to the wear process, which can be used to effectively evaluate maintenance intervals, to optimise wheel and rail profiles with respect to wear and to optimize the railway vehicle's suspensions with new and worn wheel profiles.

281 citations