### Browsing by Author "Tidbury, G. H."

Now showing 1 - 7 of 7

###### Results Per Page

###### Sort Options

Item Open Access The behaviour of polyurethane foam beams reinforced with thin walled steel sections for use in bus structures(1980-08) Gaafar, Labib A.; Tidbury, G. H.Show more The thesis is directed to the theoretical determination of the behaviour of rigid skin polyurethane foam beams reinforced with thin walled steel sections. The aim is to enable the designer to predict the behaviour of bus body structure during accident situations in order to build safe buses. A literature search has revealed that very little work has been done in this particular field of research. Thus a preliminary test programme was made to investigate the beam behaviour in bending particularly at high deflection. The test results shown in Chapter 1 gave promising results for continuing the research. Chapter 2 is directed to elastic analysis of composite beams. One of the advanced methods to predict the elastic stiffness of sandwich beams is the interfacial shear method. This assumes an interfacial shear between the core and the faces of sandwich beams. So, by considering a similar assumption, i.e. an interfacial shear between the matrix and the reinforcement, an analysis was made to predict the stiffness of composite beams. Although this method highly overestimated the stiffness, it represents a good basis for the inelastic bending analysis which is more important for the present study. Chapter • 3 shows the inelastic bending analysis of composite beams. This analysis is based on TIMOSHENKO and JAMES curvature area method. The experimental verification of the theory is shown in Chapter 4. The theory shows good agreement with the experimental results. The shape of the reinforcement was optimised for uniaxial bending. This optimum composite section showed a weight saving when it was compared with equivalent energy absorbing rectangular steel tube. Impact tests were made using a pendulum designed specially to test cantilever beams at different speed and impact energies. The test results are presented in Chapter 5. These results showed that the composite beams behaviour is similar for both static and dynamic loading. To compare the composite beam with the constituent beams, the large deflection behaviour of thin walled channel section beams made of thin sheet steel has been investigated. The experiments consisted of cantilever bending tests with the beam loaded through the shear centre and through the centroid. When loaded through the shear centre the beam buckling took place in the compression flange at the root of the cantilever. When loaded through the centroid however, it was noted that the compression flange buckled at a fixed distance from the fixed end. The general theory of thin walled beams developed by Vlasov was applied to the problem and indicated that the maximum compression stress at the free edge of the flange would be a maximum at some distance from the fixed end. The value of the maximum compression stress obtained by the general linear theory was small and its position did not coincide with the experimental position. The Vlasov analysis has been modified to include the increase in the twisting moment due to the lateral deformation- of the beam along its length. Good agreement between the modified theory and experiment both for the position of the maximum compressive stress and for the twist of the cantilever at three points along its length. Because of the very low torsional stiffness of thin walled channel sections, the small deflection theory is only applicable for small bending loads applied through the centroid and the modified theory should be used for practical loading cases.Show more Item Open Access Bending Collapse Of Rectangular Section Tubes In Relation To The Bus Roll Over Problem(Cranfield University, 1979-02) Kecman, Dušan; Tidbury, G. H.Show more The thesis is concerned with the theoretical determination of the overall and local effects on the collapse behaviour of bus structures in a roll over situation. The aim is to enable an early selection of structural components, so that the finished body can absorb enough energy and preserve sufficient strength to meet the roll over safety requirements. Chapter 1 gives an introduction into the bus roll over problem, discusses the present safety legislation and reveals that there is very little information on the performance of buses in real accidents and that no collapse analysis of the complete structure or bending collapse of its details had been undertaken. The investigation into 21 bus roll over accidents, summarised in Chapter 2, showed that structural safety relies on both the overall collapse modes and hinge properties. Theoretical determination of the overall collapse mechanism and maximum strength of a typical British coach is carried out in Chapter 3 using the CRASHD collapse program. Some peculiarities of the finite element modelling are demonstrated and the analysis indicates that the collapse mechanism can be controlled by careful selection of various structural components. Chapter 4 emphasises the importance of a better understanding of the hinge behaviour in vehicle structures. Bending collapse of rectangular section tubes is investigated in Chapter 5 for hinge rotation angles up to 30-50 degrees. The analysis starts with determination of the maximum strength of sections which may buckle within elastic range. Repeatability of local collapse mechanisms enabled the definition of the appropriate theoretical model. Kinematic theorem of the limit analysis is then applied to derive the formula for the hinge moment-rotation curve. Particular attention is paid to the selection of the appropriate material properties. The agreement with experimental evidence (Chapter 6) was very good for the complete range of tubes tested. This range includes practically all the standard sections that are used in the general structural design. The theory is used in Chapter 7 to optimise sections from the safety point of view and, in combination with the CRASHD program, to predict the collapse behaviour of beams, bus rings and complete structure entirely on the theoretical basis. Static and dynamic tests of bus rings gave good agreement with theory. The practical aspects of the work have been emphasised throughout the thesis. Detailed explanation of all the major decisions has increased the volume of the text, but the author believes that this will prove useful for practicing engineers. People interested in essentials only are referred to Chapter 8 where all the most important conclusions are given.Show more Item Open Access The design and stress analysis of an integral land rover structure(College of Aeronautics, 1968-11) Tidbury, G. H.Show more This report gives in detail the calculation of the distribution of forces in an integral structure by the matrix force method. The design of a full scale structure to test the theoretical results is described in an Appendix but test results will be given in a separate report. The method of analysis is suitable for a small, first generation digital computer and would now be superceded by 'automatic' programs on large computers.Show more Item Open Access A proposed integral land rover structure(College of Aeronautics, 1966-03) Tidbury, G. H.Show more This note summarises the methods available for the analysis of vehicle structures and points out the advantages of each method. Reasons are given for the choice of the matrix force method in the analysis of a proposed integral Land Rover structure. Some results of the analysis are given and the design of the structure described.Show more Item Open Access The reduction of structural acoustic coupling in car bodies(Cranfield University, 1982-04) Richards, T. L.; Jha, Sunil; Tidbury, G. H.Show more 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.Show more Item Open Access Stress analysis of vehicle structures(College of Aeronautics, 1964-07) Tidbury, G. H.Show more A historical review is made of the methods adopted in vehicle design. This is divided into two sections, vehicles with chassis frames and integral structures. Complete solutions have been obtained for all types of chassis frames by Erz and the results of this work are given. The simple frame structural analysis has been extended for buses, with semi-integral and integral construction. Private car structural analysis has been very approximate using pencil and paper method4 various approaches have been tried with little success. The advent of the digital computer has made the analysis of such complex structures possible and the two basic methods of ‘displacements’ and 'force’ are described. The matrix force method due to Argyris is treated in detail with a complete analysis of a simplified box van structure under idealised loading. This method has been chosen for economy in computer space and its application to a more complex structure, an integral Land Rover, is indicated. With the advent of very large computers it is probable that displacement methods will, take precedence as less work in 'choosing' the idealisation and redundant systems is involved.Show more Item Open Access The stress distribution in the joints of vehicles chassis frames subject to torsion(Cranfield University, 1978-02) Alvi, M. S. I.; Tidbury, G. H.Show more The problem of warping inhibition in the joints, of commercial vehicle chassis frames is very important for the estimation. of stress distribution in the joints and the overall torsional stiffness of frames. The joints being the weakest parts in the entire frame require that the stress levels should be estimated when designing a frame for required torsional stiffness. Plate theory has been applied to-analyse stress distributions in the joints of a ladder frame-in torsion. The frame consists of channel section cross members-welded to the web: of the side members. The degree of cross member warping inhibition in the welded joints has also been estimated analytically by using the concept of the strip beam theory. - The analytical values of stresses have been compared with-photoelastic measurements on photoelastic models of isolated joints and a complete ladder frame.Show more