The system for predicting tyre performance on sand, measuring sand strength with a cone penetrometer and using non-dimensional empirical curves developed by the Waterways Experiment Station (WES) of the U. S. Army was investigated. A series of tyre tests on dry Cresswell sand were carried out and the results were in complete disagreement with the WES system, in both its original and revised forms. It was therefore decided to try to discover the basic soil mechanics of such a system and modify it accordingly. Critical State Soil Mechanics describes two types of soil behaviour, dilating and weakening or compacting and strengthening. It was found that the first of these processes occurred in most situations likely to be found naturally, compaction occurring only in the loosest states obtainable under laboratory conditions. Under dilating conditions sand strength is described by the density, γ (Gamma). and the angle of internal friction, Ø. The angle of friction, for a single sand, was found to vary over a very wide range, depending on the state of compaction and the confining pressure. Density does not vary greatly. The cone penetrometer gradient, G, was found to be related to Ø at a low confining pressure, and the relationship was well described by the theory of Durgunoglu and Mitchell (1975). This lead to the idea that tractive performance would be dependent on Ø, which would be lower the higher the tyre contact pressure. A series of tyre tests on a single tyre on two sands showed clearly that performance depended on both tyre pressure and tyre load. The WES numeric only contains pressure. It was therefore decided to include both parameters by expressing performance by several curves depending on the tyre deflection. Deflection. being expressed as a ratio of tyre diameter rather than tyre section height. The new system was shown to describe all of the WES data better and more logically than their system. The reason why the system cannot describe performance in Yuma and Mortar sands with the same single curve as for Leighton Buzzard and Cresswell remains a mystery.

This thesis documents a study into the effects of various parameters on the performance of Framed Child Seats (FCS) for automobiles. The work investigated the effect of three different sets of parameters: FCS design parameters, vehicle design parameters and occupant biomechanical parameters. The work was conducted at Middlesex University using a combination of experimental crash testing and computerised crash simulations. The experimental crash tests were conducted using the Road Safety Engineering Laboratory, Middlesex University impact test rig and the computerised simulations were conducted using MADYM03D software. The performance of the FCS configuration was assessed in terms of the potential injury to a child occupant in a 50 km/h frontal impact to ECE R44 test specification. All the FCS design parameters examined were shown to have a potential effect on the performance of the FCS. In particular FCS footprint area was shown in the experimental tests to have a significant affect on the performance. A large flat footprint was observed to reduce chest acceleration by 33%, although this was at the expense of a large increase in forward head excursion. Various vehicle design parameters were shown, by MADYM03D simulation, to have a considerable affect on FCS performance. A standardised semi-rigid or rigid anchorage system is recommended to overcome such problems in real vehicles. The biomechanical work was largely based around the potential for injury to the occupant's neck. An improved MADYM03D representation of the dummy neck was developed for this work and several factors were examined. Chin-chest contact, head mass and neck fulcrum for bending were all shown to have a potential affect on the likelihood of injury. Limitations of both experimental crash testing and computerised simulations were identified during this work and are discussed in this thesis.

No description available.

The thesis describes modelling methods that are being developed to support the design and evaluation of intelligent railway braking control systems. A particular feature is that the models include higher order vehicle and train dynamics, the effects of which are expected to become important as the performance of braking systems improve. The thesis describes mathematical techniques for modelling braking systems starting with braking of a single wheelset on its own, then a single braked wheelset in a bogie, followed by a single braked wheelset in a complete vehicle and finally four wheelsets braked in a complete vehicle. The mathematical model for the braking system combines the non-linear creep laws governing the braking forces generated between wheel and rail with the suspension dynamics of a typical high speed railway vehicle.

No description available.

Considerable effort has been put into the development of display technologies such as liquid crystal displays, vacuum fluorescent displays, CRTs and so on. In the aviation field in particular, much ergonomics effort has been expended on specific aspects of the display technology such as the contrast ratios, effects of glare, font and so on. However, very little is known about the ergonomics aspects of new display technology applications in cars. In a series of experiments reported in this thesis three electronic display designs for a car instrument panel comprising speedometer, tachometer and minor gauges were tested by potential users.

This work investigated the design of classical and optimal control strategies to actively control the flexible modes of a high speed railway vehicle body. It explored the novel idea of adding a third actuator at the centre of the vehicle body to suppress the flexible body modes (i.e. first symmetrical and first asymmetrical) in addition to the actuators located across the front and rear secondary suspensions. The aim is to minimise the level of vibration and improve the ride quality (comfort). Both the two and three actuators are considered in the classical and optimal control strategies investigated.

The purpose of this work was to examine vehicle fuel consumption in urban areas and provide a means by which consumption in various situations could be expressed. A review of previous work has been made, including details of the models used for overall consumption in urban areas. The models used are examined and compared with a simple model based on journey distance, journey time, and number of stops. The value of kinetic energy change as a predictive variable is also examined. An explanation of commercial vehicle consumption is provided, but there are difficulties in generalising this to include the whole vehicle fleet. Minimum estimates of consumption related to gross vehicle weight and functions of journey speed are therefore given for overall consumption and for urban conditions. The effect on fuel consumption of changing the area traffic signal control regime from TRANSYT to SCOOT is examined. The method used is to compare complete journeys of several kilometres rather than short lengths of road near each signal. Significant improvements are found for those routes which are mainly inside the control areas. Consumption at roundabouts, in queues, at simple curves and at part stops are considered in detail. The roundabout data and queueing data were collected on street, and the test track results for part stops and simple curves are compared with limited on street data. Predictive equations are given for the consumption of a 2. 2 litre car.

In an effort to increase the available capacity of a lead-acid battery, the effects of pulsed discharge currents as opposed to the effects of continuous discharge currents on the battery were investigated, for a wide range of frequency, mark/space ratio and peak current of the discharge waveform. It was found that for certain conditions of pulsed discharge, the use of pulsed currents can provide a considerable increase in available capacity when compared to that obtained from using conventional continuous currents. In order to increase the efficiency and reduce the time of the lead-acid battery charge, the effects of using pulsed charging currents with ·and without depolarisation discharge pulses interspersed throughout the charging period as opposed to using conventional continuous current charging was investigated. For the tests performed, it was found that pulsed current charging without depolarisation pulses offers no advantages over conventional continuous current charging for three-stage and single-stage charging techniques. The use of pulsed currents with depolarisation pulses was found to be less effective than using conventional continuous current or straight pulsed current charging. A model for the cell terminal voltage and state-of-charge of the battery is derived from the results of an extensive series of tests performed by the author. In this writing for the first time a model accurately accounts for the dependence of recuperation, regeneration and wide variations in the discharge rate on the temperature of the electrolyte and the effects of these factors on the terminal voltage and state-of-charge. Additionally, for the first time a comprehensive model for use with pulsed discharge currents is derived. The models were tested under dynamic conditions of battery operation and were found to be able to predict battery state to a high degree of accuracy, and were also found to be more accurate than existing models.

No description available.