Contents vii 2.7.6 Application of Power Spectral Densities to Vehicle Dynamics ...166 2.7.7 Response of a Single-Degree-of-Freedom System to Random Inputs 2.7.8 Response of Multiple-Degrees-of-Freedom Systems to Random Inputs 170 2.8 Summary 174 2.9 References... 174 Chapter 3 Tire Dynamics 177 3.1 6.3.3 Ratio of Radius of Turn 6.4 Dynamic Characteristics of Handling ..
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.
This study divided into three portions to provide performance requirements; overview and development of various engine mounts; and the optimization of engine mount systems. The first part provides an insight about the ideal engine mount system that should isolate vibration caused by engine disturbance force in various speed range and prevent engine bounce from shock excitation. This implies that the dynamic stiffness and damping of the engine mount should be frequency and amplitude dependent. Therefore, the development of engine mounting systems has mostly concentrated on improvement of frequency and amplitude dependent properties. The second part starts discussion on the conventional elastomeric mounts that offer a trade-off between static deflection and vibration isolation. The next level, passive hydraulic mounts can provide a better performance than elastomeric mounts especially in the low frequency range. Subsequently, semi-active and active techniques are used to improve performance of hydraulic mounts by making them more tunable. The active engine mounting system can be very stiff at low frequency and be tuned to be very soft at the higher frequency range to isolate the vibration. The final part is about the optimization of engine mounting systems. An overview of the current work on this optimization shows some limitations. Further study is needed to consider the nonlinearities and variations in properties of different types of mounting systems.
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