Thesis (Ph. D.)--University of Wisconsin--Madison, 1969. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliography.

Thesis (doctoral)--Universität, Regensburg, 2006. / Includes bibliographical references (p. [235]-257).

The most important areas of interest concerning air cored linear machines (ACLM), their design, development and application to guided ground transportation are presented. A description of the origins of high speed guided ground transportation (HSGGT) is given which covers tracked air cushion vehicle and linear induction motor development, as well as the electromagnetic and electrodynamic systems of levitation. ACLM began as the favoured propulsion option for the electrodynamic system, and the machine characteristics of the linear synchronous motor (LSM) are discussed with optimization techniques given for choice of wavelength. Stress factors for rectangular coils with tight corner radii can be calculated using a circular coil equivalent. The linear commutator motor (LCM) provides a means of achieving high local track power density without degrading overall machine performance. Several forms are examined and the trade off and comparison with LSM made. The system comparison of the electrodynamic and electromagnetic systems (EDS and EMS) of magnetic levitation indicates that specifying Just lift to drag ratio and specific energy Intensity is an insufficient base. Comparison is made of the German EMS and EDS designs, together with a comparison of other groups' EDS vehicles. The German EDS design is found to be heavily penalised by excessive low speed suspension weight. Several variations of a new type of ACLM using on board flux pumping are proposed. The advantages are that a passive track structure is possible, and a cryogenically cooled winding can be used as a cost effective alternative to a superconducting coll. Application of ACLM to propulsion of advanced duorail vehicles is set out together with the possibility of speed extension with reduced track wear and Initial capital coat, as well as reduced manning and maintenance cost. An Advanced Passenger Train with LSM would appear to be a feasible option for future transport needs, and extension to a low speed urban vehicle using for example liquid nitrogen cooled pool boiling coils would similarly present a low cost system. An indexed bibliography containing over 400 HSGGT references is included, with a bias to EDS and ACLM.

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Ground vibration from trains is an increasingly important environmental problem. This study investigates the various excitation mechanisms of ground vibration. An existing semi-analytical model, TGV, which considers both the quasi-static excitation due to moving axle loads and the dynamic excitation due to vertical rail irregularities, has been validated by an extensive measurement campaign. This involved the determination of soil properties at two sites with soft clay soil. These were found to exhibit an inversion of the wave speed profile. Good agreement was found between measurements and predictions of vibration due to train pass-bys. The relative importance of the dynamic and quasi-static excitation mechanisms has been investigated for a range of conditions including changes to track and vehicle parameters. The dynamic excitation mechanism is found to dominate the results above about 10 Hz and at all frequencies for distances beyond 10 m from the track. In order to study other excitation mechanisms a new hybrid model has been developed. This combines a wheel/track interaction model working in the time-spatial domain and an axisymmetric layered ground model working in the wave number-frequency domain. In the time domain model a ‘circular’ track is introduced to allow longer responses to be calculated. The model is then validated by comparison with the existing TGV model. A reasonable agreement is found. The hybrid model has then been used to investigate the relative importance of quasi-static loads, dynamic loads and some other excitation mechanisms for trains running on the ground. The sleeper-passing effect is investigated for both constant and variable sleeper spacing but it is found to give much lower responses than those due to roughness. Variable ballast stiffness is also investigated and found not to be significant. Impact forces caused by the passage of wheels over dipped welds and stepped joints are found to generate ground responses that are considerably larger than roughness excitation in the region close to these track defects. However the response decays more rapidly with distance than that due to roughness.

The aim of this research is to develop a fuller understanding of the mechanical behaviour of the sleeper/ballast interface, related in particular, to the forces applied by high speed tilting trains on low radius curves. The research has used literature review, field measurements, and laboratory experiments on a single sleeper bay of track. Theoretical calculations are also presented. Field measurements are carried out using geophones to record time/deflection for sleepers during passage of Pendolino trains on the West Coast Main Line. Calculations are presented to quantify normal and extreme magnitudes of vertical, horizontal and moment (VHM) loads on individual sleepers. Results from laboratory experiments, on the pre-failure behaviour of the sleeper to ballast base contact area, show that lateral load/deflection behaviour is load path dependent and relations are determined for improved computer modelling of the sleeper/ballast interface. Further test results are used to establish the failure envelopes for combined VHM loading of the sleeper/ballast base contact area. Tests show that the sleeper/ballast base resistance at failure occurs at a load ratio (H/V) of about 0.45 (24°) at 2 mm of displacement tending to 0.57 (30°) at greater displacements. In addition, measurements from pressure plates within the testing apparatus are used to describe the development of confining stress within the ballast during 100 cycles of vertical load. The development of confining stress is assessed with reference to a finite element model of the laboratory apparatus and it is shown that the earth pressure ratio moves towards the active condition for peak load and the passive condition at minimum load per cycle. The contribution to lateral resistance of the crib ballast and varying sizes of shoulder ballast is also established and it is found that the shoulder and crib resistance can best be characterised by taking the mean resistance over a range of deflection from 2 mm to 20 mm. Calculations are presented, supported by the experimental data, to quantify the resistance from different sizes of shoulder ballast and a chart is presented which can be used as the basis for shoulder specification in practice.

For application in damping treatments, elastomeric materials should have a high damping loss factor, but this is inevitably linked to a strong temperature-dependence of the dynamic properties. A methodology is developed that allows a material to be formulated for a particular damping application where temperature-dependence has to be taken into account. The methodology is applied to the case of a tuned absorber system used for damping the vibration of a railway track. This is required to be effective over a temperature range -20°C to 40°C. To investigate the effect of the temperature on the performance of a rail damper, a simple Timoshenko beam model of the track vibration is used, to which are added single-frequency and dual-frequency tuned absorbers. The results show that a high noise reduction can be achieved for the optimum stiffness, provided that the loss factor is between about 0.25 and 0.4. In order to study the generic effects of high damping versus constant stiffness, the time-temperature superposition principle is used to convert frequency-dependence to temperature-dependence for a notional material with constant loss factor. This is used in the prediction of decay rates and thereby noise reduction. In addition, a weighted noise reduction is studied by using measured rail temperature distributions. This temperatureweighted noise reduction allows a single number measure of performance to be obtained which can be used to assess various elastomeric materials in order to determine the optimum material for a given situation. Two types of viscoelastic material, butyl and EPDM rubbers with various amount of fillers and plasticisers are investigated. The properties of both rubbers have been measured over the range of temperatures for frequencies 300-3000 Hz. For this a test rig had to be modified. For butyl, the best combination of filler and plasticiser gives temperature weighted noise reductions up to 5.9 dB(A). Butyl rubber is suitable for use in the rail absorber giving high noise reductions between 0°C and 40°C. The best EPDM compound gives a temperature-weighted noise reduction up to 6.2 dB(A). Comparing these two rubbers, EPDM is more suitable for low temperatures below 10°C and butyl is more suitable for higher temperatures above 10°C.

A model of the development of rail-head acoustic roughness on tangent track has been formulated. The model consists of a two-dimensional time domain wheel-rail interaction force calculation, with the normal force used as the input to a two-dimensional rolling contact and wear model. The possibility of multiple wear mechanisms arising from stress concentrations is considered by using a wear coefficient that can vary with the conditions at each point in the contact. The contact model is based on a variational technique, taking account of non-Hertzian and transient effects. A novel feature of the rolling contact model is the introduction of a velocity-dependent friction coefficient. In rolling contact this leads to a high frequency stick-slip oscillation in the slip zone at the trailing edge. Roughness development depends on the dynamics of the track. Roughness growth has often been linked to the pinned-pinned frequency and other resonances of the coupled track and vehicle system. Here the effect of different vehicle and track parameters on track dynamics, wear and roughness development has been examined. Rail dampers are studied as they change the dynamic response of the track. Results are presented in the form of roughness growth rate functions both for individual vehicle types and for mixed traffic. The model parameters match those at a site used for measurements of roughness development taken by Deutsche Bahn AG as part of the EU project Silence. The study shows that it is important to include non-Hertzian effects when studying roughness with wavelengths shorter than 100 mm. With a non-Hertzian contact model, no mechanism has been found for consistently increasing roughness levels. The model predicts that roughness wavelengths shorter than the contact length will wear away. Rail dampers are shown to reduce the pinned-pinned frequency and smooth the peaks and troughs in the track receptance. Rail dampers also reduce the dynamic wheel-rail interaction forces, especially around the pinned-pinned resonance, and shift the force spectrum to lower frequencies or longer wavelengths. However, rail dampers are not predicted to affect roughness growth rates significantly.

Passengers of land transport are exposed to horizontal and rotational oscillations at frequencies less than 1 Hz which may cause vibration discomfort and motion sickness. Previous knowledge of human responses to motion is insufficient for predicting the discomfort caused by low frequencies. The objective of this thesis is to improve understanding of subjective responses to lateral and roll oscillation (presented in isolation and in combination) at frequencies less than 1 Hz in order to establish a predictive model of comfort. The first of five experiments tested the predictions of a conceptual model of motion sickness. Illness ratings were obtained over a 30-minute exposure to 0.2 Hz fully roll-compensated lateral oscillation where the point of full roll-compensation was either at the seat surface (i.e. ‘seat compensation’) or at head height (i.e. ‘head compensation’). Median illness ratings were greater during ‘head compensation’, showing some support for the motion sickness model, but differences were not statistically significant. Age, stature and body weight had no effect on illness ratings, but Asians were more than three-times as likely to experience ‘mild nausea’ than Europeans. It is concluded that differences in the position of full roll-compensation in transport vehicles are less important for motion sickness than inherent differences in passenger populations. The next four experiments used the method of magnitude estimation to determine the vibration discomfort caused by lateral oscillation, roll oscillation, and fully roll-compensated lateral oscillation with a variety of seating configurations. In the second experiment, lateral acceleration between 0.2 and 1.0 Hz caused less discomfort when sitting with a backrest than when sitting without a backrest on both a rigid seat and on a cushioned train seat; contrary to the predictions of current standards. In the third experiment, 0.25 to 0.4 Hz lateral acceleration in the plane of the seat caused similar discomfort regardless of whether the acceleration was due to lateral oscillation or roll oscillation through the gravitational vector, but above 0.4 Hz, discomfort from the roll was far greater. At frequencies less than 0.5 Hz, fully compensating the lateral acceleration with roll improved comfort compared to uncompensated lateral acceleration, but at greater frequencies, roll-compensation worsened comfort and caused discomfort similar to pure roll oscillation at 1 Hz. The fourth and fifth experiments examined differences in discomfort caused by the rigidity of the seat pan and the height of the backrest. In the fourth experiment, discomfort was greater on a soft foam seat than on a rigid seat during lateral oscillation below 0.63 Hz, during roll oscillation below 0.5 Hz and during fully roll-compensated lateral oscillation between 0.315 and 0.5 Hz. In the fifth experiment, discomfort was greater without a backrest than with a short backrest for lateral oscillation between 0.315 and 0.5 Hz. Contrary to current standards, discomfort was also greater without a backrest than with a high backrest for lateral oscillation below 1 Hz and for roll oscillation below 0.5 Hz. In addition, sitting with a backrest was beneficial for comfort with fully roll-compensated lateral oscillation between 0.4 and 0.63 Hz. The results of the five experiments were collated to provide recommendations for the improvement of current vibration standards. On the basis of experiment 1, a new multiplying factor for the prediction of vomiting incidence in an unadapted group of male Asian adults is offered. On the basis of the four discomfort experiments, modifications to current frequency weightings for lateral acceleration and roll acceleration are offered so as to extend the prediction to frequencies less than 0.5 Hz. Guidance for the prediction of discomfort with fully roll-compensated lateral oscillation is also provided. The thesis is concluded with recommendations for future research.