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To study the dynamic interactions hetween the rai1:vay aehicle and track, a Jinite element model of infinitely long track is deiieloped. The track is represented by a Timoshenko beam on discretz pad-tie-ballast supports. The non-linear factors such as loss of wheel-rail contact, rail lift-nfl from the tie and tie lift-of from ?he ballast are taken into account. A multi-point wheel-rail contact model is also proposed. The dynamicforces on the track and the strains on the rail are directly calculatedjrom the model. The vehicle could trawl on the track forever with an arbitrary time-dependent speed. The steady-stute response of a tiehicle-track system for a perjiect wheel carrying a constant load and traaelling at a constant speed nuer a track with no irregularities is studied using thefinite element model and is presented. The impact loads due to whee1,flats are also studied with this model. The results show a good correlation with the experimental data available in the literature. lnjuences of sysiem parameters on the impact loads due to u whee1,flat are also investigated. T' 1 wesults show that the ax!e load and uehicle speed are the important factors ufecting the whee/-rail impact loads. The impact forces transferredfiom the rail to the tic. are strongly aficcted by the pad stiffness and tie mass.

The concept of an “on-off” damper employing the feedback signals from directly measurable variables is proposed. A control scheme utilizing the directly measurable relative position and relative velocity signals to produce the command signal is configured. The on-off damping mechanism can be achieved through the modulation of orifice area in a conventional hydraulic damper, using a two position on-off valve driven by the command signal. The shock and vibration isolation characteristics of the proposed on-off damper are evaluated through computer simulations. The shock and vibration isolation performance characteristics of the proposed damper are compared to the performance characteristics of a passive and an on-off damper utilizing the feedback from absolute and relative velocity signals.

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Semi-active suspensions can achieve performance close to that of active suspensions with much lower cost and complexity. They use an active damper in parallel with a passive spring. The forces in the damper are generated merely by the modulation of fluid-flow orifices based on a control scheme involving feedback variables. This paper presents an original control strategy employing only directly measurable variables in vehicle applications. The relative displacement and relative velocity across the suspension are the only feedback signals and the damper force can be continuously modulated (as opposed to on-off control). Vibration isolation performance of the new semi-active scheme is compared to semi-active sky-hook suspension, as well as passive and active suspensions.

A study of the liquid behaviour in horizontal cylindrical road containers undergoing a steady turning manoeuvre is presented and discussed. The steady state solutions are derived analytically from the hydrostatic equations. The transient solutions are obtained by numerical integration of the Navier-Stokes, continuity and free-surface equations. The non-dimensional governing equations are solved in primitive variables by using a modified marker-and-cell technique which involves the interpolation-reflection type boundary conditions developed for this investigation. The mathematical model of the liquid motion includes all essential non-linear effects and allows the damped natural frequencies of liquid vibrations to be obtained as well as the magnitudes of the liquid slosh loads. This study also enables the coupled directional dynamics of the ‘vehicle-liquid tank’ system undergoing different road manoeuvres to be investigated by integrating the non-linear fluid slosh model and an appropriate vehicle model simultaneously.

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