In this work. an attempt has been made to develop a programming package for ride analysis of off-road vehicles based upon a finite-element formulation of vehicle suspension systems. Mathematical modelling of generalised suspension systems has been carried out with several non-linear aspects being investigated and implemented in the programming package. such as large deflection. non-linear characteristics of springs and dampers. bump stops and wheel separation. Different types of soi 1 have been considered together with an appropriate modelling of vehicle tracks. Several methods for time integration of dynamic equations have been investigated so as to deal wi th numerical instabi 1 i ty problems expected for off-road suspension systems which often have 'stiff' differential equations of motion. Three ride analysis criteria have also been considered in the programming package. Several case studies have been analysed using the developed programming package. They consist of two simple case studies with known analytical solutions. an existing wheeled off-road vehicle with published analog computer resul t s , and an off-road tracked vehicle wi th known experimental results. The package has been validated and proved to be an acceptable tool for the ride analysis of off-road vehicles. within the approximating assumptions considered. Several measures for future development have also been suggested.

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.

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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.

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Modern road vehicle suspension and steering systems may generally be classed as multi-loop spatial mechanisms, designed with links constrained and interconnected in such a manner as to attempt a preferred and prescribed motion of the steered wheels with regard to the inputs to the system. The mechanism incorporates elastic and damping elements and is terminated to the ground surface via the tyres. The complete system may be modelled as a multi-body system with spatial kinematics. This work demonstrates an analysis and simulation of the mechanics of a double wishbone/rack and pinion suspension and steering system modelled as a multi-body system. A 3-dimensional Newton-Euler based approach employing vector and matrix notation is used in deriving the coupled set of non-linear equations of motion, and these together with the kinematic equations of constraint are cast in state space form, and numerical solutions sought using a digital computer. The kinematic equations are derived from the velocity loop equations for the model, and deal with the so-called redundant degrees-of-freedom arising in models of this type in a completely general manner. The tyre, shock absorber, main spring, and steering gear are modelled from empirical data. A feature of the work is that the complete set of equations need not be excessively manipulated manually, and that use of a set of specially written computer program routines allows a numerical formulation of the equations in the machine, enabling the main program to be written from inspection of the 'raw' equations. Large displacements and therefore changes of geometry are considered, with the provision for partial numerical linearization of the geometric aspects if required. The kinematic behaviour of the model is also described. A supporting experimental programme of work with a vehicle on a rolling drum rig has been conducted in parallel to the simulation work. And results indicate good correlation between theory and experiment at low frequencies of vibration.

The nature of sound in cars is discussed in the light of previous experimental and theoretical work, and the major contributions to interior noise are identified. The acoustic field inside a vibrating structure is analysed theoretically in terms of the acoustic cavity modes and the structural modes, and it is shown that'reduction of structural-acoustic coupling could reduce the response for a wide variety of force inputs. Finite element analyses of prismatic acoustic cavities and two-dimensinal ring structures are described and these are combined in a simple theoretical model of ring-mode excitation of sound. By stiffening selected structural elements, the structural-acoustic coupling, and hence the acoustic response, are reduced.

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