Mechanical Engineering - Theses
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ItemAssembly line sequencing for product-mix( 1971)This thesis is concerned with the sequencing of various models of a product when these are manufactured on one assembly line using product-mix. A simplified model of the assembly line is postulated. Four heuristic algorithms are developed which aim at minimizing assembly line length while avoiding operator interference. Two of these algorithms are used in a factorial experiment to determine the relationship between assembly line length and five factors. These factors are characteristics of the production requirement and workload balance. From the experimental results, empirical equations are developed which are a useful aid in the design of new assembly lines or the balancing of existing assembly lines. The experimental results are also analyzed to determine a range of sequencing problems for which near optimal sequences can be expected using the two algorithms.
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ItemThe form drag of two-dimensional bluff-plates immersed in turbulent shear flows( 1965)The literature concerning bluff-body flows in two-dimensional, incompressible, sheared and unsheared streams is reviewed. It is found that no theory yet exists which can predict the form drag of a bluff body without some recourse to experimental data, even for the simple case of an isolated bluff-plate in an unsheared stream. In the present state of knowledge, and considering the complexity of turbulent shear flows, a theory for the form drag of bluff-plates immersed in turbulent boundary-layers seems remote. A correlation scheme is proposed to relate the form drag of a bluff-plate which is attached to a smooth-wall with the mean-flow characteristics of the naturally-developed, turbulent boundary-layer in which it is immersed. The investigation is limited to smooth-wall flows of the type described by Coles (1956). It is suggested that, for bluff-plates which are small compared with the boundary-layer thickness, the drag might depend only on the “wall variables”: wall shear-stress, fluid density and viscosity, and the plate height.
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ItemFurther developments of hot wire and laser methods in fluid mechanics( 1974)Some further developments of hot wire and laser methods in fluid mechanics are examined in some detail. Since it is felt that the laser-Doppler method of measuring velocity will eventually supersede the present hot wire methods in many applications, only the response of a hot wire anemometer to temperature fluctuations is considered. This study shows that the constant temperature anemometer is unsuitable for the direct measurement of temperature fluctuations, but that a constant current anemometer operated at very low resistance ratios can be made to work quite well. An appropriate design is developed, calibration methods are outlined for the direct measurement of temperature turbulence and Reynolds heat flux, and it is shown how the possible errors due to end conduction may be eliminated by increasing the length to diameter ratio of the wire filament. In the study of the laser-Doppler velocimeter an optimization procedure is developed, taking into account such factors as particle size, measurement volume size, the width of the Doppler spectrum and the frequency response of the electronic processor. A reference beam system, designed with the aid of this optimization procedure is then used to measure velocity profiles across a vertical line vortex in water. This vortex is produced in a vortex tube with a central outlet.
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ItemThe four bar linkage as a function generator( 1960)Part I: A new concept of the synthesis of the four bar linkage as a function generator is presented. Existing methods of synthesis are examined in the light of this concept, and their advantages discussed. The basis for a new method of synthesis is presented. Part II: A machine which mechanically allows finding the by trial four bar linkage whose polodes are most nearly like the curves which generate the given function exactly has been constructed and calibrated. The apparatus is described and the conditions which indicate a solution are stated. Proof that these conditions are a solution is given. Two simple graphical methods of approximate synthesis have been developed and are used to minimize the trial and error required.
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ItemSome aspects of turbulent boundary layers( 1969)A detailed experimental programme of two dimensional rough wall turbulent boundary layers developing in zero and arbitrary adverse pressure gradients is used to investigate aspects of turbulent boundary layer development and surface roughness. It is shown that two types of roughness can be clearly distinguished on the basis of the flow variables involved. The more common ‘k’ or ‘sand grain’ type follows the well documented ‘Nikuradse-Clauser’ correlation scheme where the effect of roughness on the flow depends on the size or scale of the roughness elements. The second type of roughness, typified by a smooth wall containing a pattern of narrow cavities, is independent of the scale of the roughness and does not follow• the ‘Nikuradse-Clauser’ correlation scheme. It is shown that previous pipe flow experiments have involved this second type of roughness and these results are used to show that the dependent variable is pipe diameter. This roughness has therefore been named ‘d’ type in this thesis. No length scale associated with the boundary layer could be found to replace pipe diameter except for zero pressure gradient layers. However, it is found that the distance below the crests of the roughness from where the logarithmic distribution of velocity is measured will correlate both types of roughness action. It is shown that a zero pressure gradient turbulent boundary layer developing on a ‘d’ type rough wall conforms to Rotta's condition of precise self preserving flow. The results are used to illustrate several theoretical consequences of this type of flow. Wall shear stresses are determined by measuring in detail, the pressures on the faces of the roughness elements and thereby calculating their form drag. Similarity laws for these pressure patterns are developed for the ‘d’ type results and explicit expressions for the functions are proposed for the zero pressure gradient case. Pressure patterns around 'k' type roughness elements cannot be described by the similarity laws developed here. Theories proposed by several authors to describe the velocity profiles in regions above the logarithmic distribution are compared in detail and critically examined. Some new work related to these theories is introduced. The predictions of mean velocity distribution are tested against an extensive range of experimental data including the results of this thesis. It is shown that all the theories have important shortcomings in their present form and a recommendation for a basis for future work is offered. The problem of the transition of a turbulent boundary layer from a rough (‘d' type) to smooth wall in an adverse pressure gradient is investigated experimentally for two boundary layers. It is found that the outer regions of the boundary layer appear to be unaffected by this change in wall condition whereas the inner flow makes a rapid adjustment to it. This result is at variance to the published work on flow in conduits and for zero pressure gradient boundary layers. An explanation of this is offered. Literature surveys introduce the work in each topic.
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ItemThe design of engineering products( 1963)This thesis examines the design of engineering products. Its purpose is to clarify the role of design in engineering, to give a general description of the design process, and to emphasise aspects of the subject which are not widely recognized, or if recognized are not applied. in practice because of the designer's preoccupation with the rush of day-to-day problems. Parts of the thesis inevitably reflect a bias towards the author's experiences as a mechanical design engineer in privately owned industries where the products were manufactured in small or medium-sized batches. This bias is most clearly evident in chapter 3, but also appears in sections of chapters 2 and 4. All in all, a broad perspective has been adopted with the intention that the thesis should cover a wide range and not be confined to the interests of a special branch of engineering. For this reason the word “engineering” in the title has not been qualified in any way. After giving considerable thought to this subject the author came to the conclusion that there was scope for bringing together in one paper the ideas and concepts which are of major importance in engineering design. All too often these are not appreciated by the individual designer, because references to them are widely scattered throughout the literature or because he allows himself to be immersed in the minutiae of his work.
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ItemCavitation in hydraulic machinery: its influence on the design of impellers for centrifugal and axial-flow pumps( 1963)This thesis considers aspects of rotating hydraulic machinery of the centrifugal, mixed-flow, and axial-flow types; wherever the word "pump" is used without any qualifying adjective it is understood that it is a generic term which includes all these types. The objective is to present and discuss the methods available for the design of pump impellers for cavitating or near-cavitating conditions. In order to give an orderly and logical account of this subject the thesis opens with a description of cavitation in hydrodynamics, and this is followed by an examination of its mechanism and of the physical factors which affect it. Model experiments are an important tool in assisting the designer predict performance and one chapter is therefore devoted to a discussion of model laws and scale effects in cavitation. Chapters 4 and 5 deal with the detailed design of impellers for non-cavitating and cavitating flows, while the final chapter evaluates this work and draws some general conclusions.
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ItemCreative design skills of engineering students( 1972)An investigation has been carried out into the creative design skills of engineering students in the University of Melbourne. In order to tap students' creative abilities, open-ended design problems representative of those encountered by the professional engineer in practice were devised. Students' responses to the problems were then observed and analyzed. The results showed that there were many interesting and apparently important aspects of the students' creative problem-solving behaviour which could be identified and measured, but which were not revealed by performance in conventional university examinations. These aspects of problem-solving appear to be important from the point of view of the students' later professional careers, but further work is needed to confirm this.
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ItemInvestigation on the milling process( 1968)Metal cutting is a complex production process involving plastic deformation and tool-chip friction under unusual conditions of strain, strain-rate and stress. Since late last century workers from various parts of the world have attempted to develop analytical models that could reasonably well represent the observed phenomena. A number of analyses have evolved but these are mainly concerned with the simple orthogonal cutting process at constant depth of cut. These analyses, although not in complete agreement with experimental results, are similar, and call give a qualitative account of the observed trends. Included in those analyses area number of fundamental parameters which could prove useful in predicting quantitative results for orthogonal cutting and may possibly be used for other more practical cutting operations. The aim of this work is to extend the thin shear zone theory of cutting to the milling process with particular reference to up milling with zero helix angle cutters. Thus a geometrical analysis of the milling process and an evaluation of the undeformed chip thickness as defined by the theory of cutting is required. Due consideration of the wedge angle, rake angle and clearance angle variations is also required. To obtain the experimental data for a quantitative analysis, equipment has to be developed to measure the basic quantities in metal cutting i.e. the instantaneous cutting force variation and chip deformation. The experimental data collected will be analysed in accordance with the developed theory and it is hoped that the resulting trends will be similar to those known for constant depth orthogonal cutting.
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ItemA study of the drilling process( 1970)The modern two flute twist drill has been in existence for more than fifty years and the drilling process has become one of the most widely used manufacturing operation. There has hardly been any major alteration in the general appearance of the twist drill despite the various studies on the effect of geometry on drill performance such as tool life and cutting forces. Nevertheless a better understanding of the capabilities and limitations of the twist drill has been made possible by these investigations. The twist drill generates holes by the cutting action of the lips and the indenting action of the chisel edge. The geometry of the lips has been generalized to that of a lathe tool and the cutting action of the lips was reported as similar to single edged oblique cutting. A cutting model for drilling has not been developed possibly because of the complex geometry of the lips and the extruding action of the chisel edge, which is difficult to study. As a result many empirical equations for the prediction of forces have been proposed. In this project the geometry of the various size drills will be studied. Analyses of the mechanics of drilling will be attempted in the hope that a cutting model may be constructed based on established principles of orthogonal and oblique cutting. This is desirable since in the design and application of drilling, like in other topics of metal cutting) it is useful to be able to predict the deformation and cutting forces.