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This research work involved the prediction of the fatigue life of an automotive rear suspension twistbeam assembly fitted to a vehicle travelling over a customer correlated durability route. This was achieved by making use of the integrated concepts of scaling and superposition of linear static finite element analysis being driven by experimental load data - the so called 'quasi-static time domain' approach. A study of the free body diagram of the twistbeam resulted in an indeterminate load set of some 24 components, with experimental data indicating that a state of static unbalance existed. Subsequent to developing a matrix-based generalised method ofload cell calibration to confum the foregoing, a modal technique was developed to partition the experimental data into a static load set, causing elastic deformations, and a rigid load set, imparting rigid body accelerations. The semi-independent characteristics of the twistbeam necessitated the coupling of large structural displacements with inertia relief. This required extensive modifications to the current techniques and led to the development and use of a three dimensional functional response matrix in place of the conventional two dimensional one. Recommendations concerning appropriate finite element boundary conditions were also formulated to handle these effects. Finally, the limitations of the uniaxial fatigue model were revealed under the application of a set of tools for analysing the biaxiality and mobility of the maximum absolute principal stress.

The advent of high-performance, traffic-compatible, electric road vehicles (EVs) has brought with it an increasing range of uses and this study is concerned with evaluating the suitability of EVs for a hitherto unresearched application for this emerging technology, namely the island communities of Lewis and Harris. The stimulus for the renewed research and development of EVs has resulted largely from concerns about future energy supply, particularly of oil, and environmental conditions. An assessment of the state-of-the-art of EV technology and of traction battery systems in particular is presented. A strategy for development, commercialisation and diffusion is outlined which recognises the nature of the technology and its likely diffusion process. Market segments, such as island communities, which are suitable for early introduction must be identified. The islands of Scotland were chosen for investigation because of their current patterns of transport. The assessment of potential for EV introduction focuses on the requirements of a personal means of transport in terms of factors such as operating performance, utility, reliability, ability to refuel adequately, safety of operation and disposal, economic advantage and acceptability to motorists. Various relationships are established between the state of EV technology and the potential for introduction in the islands. A practical methodology for assessment which adopts a holistic approach is constructed. This is designed to be generally applicable to other similar EV assessments. The methodology employs a series of purpose-built computer simulation models and data collection techniques in order to model real life situations and systems as closely as possible, facilitating the evaluation of market potential and identification of barriers to EV introduction in the islands.

When an articulated tipper unit is being loaded or is tipping, it is unlikely to be standing on perfectly level ground. Also, the centre of gravity of the load is unlikely to be in the centre of the body. Hence the loads carried by the suspension and tyres on one side of the tipper will be greater than those on the other side. This uneven loading will cause the tyres and suspension on one side of the tipper unit to deform more than those on the other side. It will also cause the chassis to deform; the twisting about its longitudinal axis being the most significant mode of deformation. As a result of these deformations caused by the uneven loading, the position of the centre of gravity will be shifted even further towards the more heavily loaded side. This will cause even more uneven loading and further deformations. Under stable conditions a situation will exist at which the position of the centre of gravity, the deformations and the forces transmitted through the system are compatible. Instability, resulting in roll-over would occur if the overall centre of gravity of the load, body, chassis etc. were to fall outside the area bounded by the contact of the wheel with the ground, before a stable condition was reached. Many factors influence the roll stability. To increase stability, an understanding of the influence of components of the lorry on the stability is required. In order to achieve this, a theoretical model of an articulated tipper was developed which will allow roll-over predictions to be made for a given lorry in likely attitudes. In this model dimensions and stiffness of the lorry components can be altered to assess their influence on roll stability. The previous theoretical roll-over models were based on lumped mass systems, representing various parts of the lorry inter-connected by compliant elements. Certain flexibilities such as the tyres, suspension units, etc. could be obtained from the respective components manufacturers but the tractor and trailer chassis flexibilities are unknown. To overcome this problem the flexibilities were obtained from full scale static tilt tests. This is a very expensive undertaking, providing a limited means in which to assess those elements of trailer design which are important in improving stability, without further recourse to more tilt tests. It was decided that the finite element method should be used to model the tractor and trailer, in order to determine the important deformations. Once the finite element model is created it is relatively straight forward to make changes to the structure. Hence an assessment of component contribution to roll stability can be undertaken relatively inexpensively. Whilst a vehicle operator should always endeavour to discharge the payload with the vehicle standing on level ground, practical situations arise where this is not possible. This may be due to the absence of level ground or poor judgement by the operator, which may result in the vehicle being tipped on a lateral ground slope. As a result of this, the maximum ground slope angle considered for the theoretical model is limited to eight degrees, as this position is at least twice the severity of ground slope on which a vehicle should normally be tipped. For each trailer design, the magnitude of the load, position of the load, ram length and ground slope can be varied in any combination. Four payloads and up to nine payload positions are considered, varying the ground slope from 0 to 8 degrees and varying the ram length from 2 to 8 meters. Also, three further chassis configurations, based on the reference chassis were modelled to investigate the contribution of important component flexibilities on roll stability.

The environmental wind tunnel at Nottingham University has been extended so that realistic mean hourly atmospheric boundary layers can be generated at sufficient scale to allow aerodynamic tests of sharp edged vehicles to be undertaken. A moving model rig owned by British Rail Research was installed perpendicular to the flow near the end of the working section. As part of this project an automatic refiring mechanism was developed allowing some 2000 transits of vehicles incorporating an internal balance and data logger to be made across the working section with a realistic mean hourly atmospheric boundary layer present. The quality of the data from the moving model rig was assessed. Moving model rig tests and static model tests of a 1/50th scale lorry and 1/45th railway container vehicles have been conducted and extreme value forces and moments relevant to the gust time that overturn a vehicle were calculated. These are the first measurements to have been made using a realistic mean hourly ABL and modelling the vehicle's movement. This thesis assesses the usefulness of the normalised extreme force parameter in determining the extreme forces that a full scale moving vehicle experiences. It was found that the normalised extreme force parameter remains invariant with model time scale for the range of times considered. Further for both the moving model rig tests and the static tests the value of unity that this parameter takes for yaw angles above 30 degrees implies quasi steady behaviour without additional body induced unsteadiness. At lower yaw angles, however, some body induced unsteadiness is evident. These conclusions are compared with predictions from existing numerical models and previous experimental tests. The measured lift force from the static tests compared with the moving model rig tests at 90 degrees yaw angle, i. e. with the moving model stationary, shows a large difference. This is not understood and two concerns are expressed: the effect of the slot, through which the supports of the moving model travel, beneath the vehicle, may be altering the pressure in this region; or it could be due to a Reynolds number effect caused by the small underbody height above the ground.

No description available.

No description available.