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Metal shaping processes are clear examples of engineering applications where a hard material is worn by a softer one - i.e. the tool and workpiece respectively. The soft impressor technique, introduced by Brookes and Green (1973), has proved valuable in measuring the relevant mechanical properties of tool materials - e.g. the measurement of the flow stress of diamond single crystals at temperatures up to 1500°C (Brookes, 1992). In this work, the technique has been extended further in order to form a basis for the comparison and evaluation of ultra-hard materials. Three main aspects of the performance of these tool materials have been covered: the effect of temperature on flow stress; cumulative deformation under point loading conditions; wear due to repeated traversals (fatigue). In the first part, the technique has been extended to determine the flow stress of polycrystalline diamond and cubic boron nitride as a function of temperature and a mathematical model has been proposed to estimate the flow stress in isotropic polycrystalline materials. This model was first analysed by Love (1928) and was used as the basis on which to identify the threshold pressure above which dislocation movement is initiated in diamond single crystals (Brookes et al (1990)). The applicability of this model for polycrystals was verified by correlating the yield strength of polycrystalline copper, measured in tension, with the determination of minimum contact mean pressure to plastically deform the same material. According to the model, the first evidence of plastic deformation should be observed at the contact periphery and this has been verified in this work. Consequently, using this approach, the effect of temperature on the flow stress of polycrystalline diamond (Syndax) and polycrystalline cubic boron nitride (Amborite) has been established and it is shown that there are three distinct regimes. In regime I, the deformation is brittle and fracture occurs above a given mean pressure; in regime II dislocations are mobile and the flow stress decreases sharply as the temperature rises; and in regime III the flow stress is independent of the temperature. In the earlier work, the brittle-ductile transition temperature (BOT) has been identified as that temperature where regime I ends and II begins. Above the BDT, time dependent plastic flow has been observed, in all of these materials, leading to a measurable increase in the size of the impression. However, this particular type of cumulative deformation, described as impression creep, is shown to be different to conventional creep as measured under uniaxial stress conditions. Finally, the room temperature friction and deformation of various polycrystalline diamond based specimens, Le. aggregates with a binder phase of cobalt (Syndite) or silicon carbide (Syndax), a polycrystalline coating produced by a chemical vapour deposition processes (CVDite) and cubic boron nitride (Amborite) were studied when softer metallic and ceramic sliders were used. As a result of increasing the number of traversals, significant wear of the CVDite diamond coating by softer metallic sliders (aluminium and mild steel) was observed. This could be attributed to the high level of residual stresses in the diamond layer which is thought to be due to the difference in the thermal expansion coefficients of the coatings and their substrates. Burton et al (1995) reported a strain of 0.3% on the surface of the diamond coating and hence the tensile stress on the upper side of the coating will be equivalent to about 3.0 GPa. This value is comparable to the theoretical cleavage strength of diamond. It is suggested an additional tensile stress, due to the sliding friction, could have caused cleavage of individual diamond crystals. The resultant wear debris then becoming embedded in the metallic slider. These embedded diamond particles in the tip of the slider could be responsible for the increased friction and wear.

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A study has been made of the respective performance of cubic boron nitride (CBN) and polycrystalline diamond (PCD) cutting tool materials and compared to various coated and uncoated tungsten carbide grades when cutting titanium alloy workpieces. Two important experimental techniques were employed during the course of this work, firstly a quasi-static contact method was employed to establish the workpiece/tool interfacial temperature above which strongly adherent layers may be formed. This technique revealed that the critical temperatures which marked adhesion and welding, were 740, 820 and 800 °C for coated and uncoated carbides, and 760 and 900 °C for PCD and CBN tools respectively. Furthermore, the technique has been used to study the integrity of the bulk tool material, and/or individual coatings on their substrates, when welded junctions formed between the tool and workpiece are separated. With regard to the latter it was observed that in all cases fracture was initiated in the bulk of the harder tool material rather than in the workpiece or at the welded junction interface. Secondly, a quick-stop technique was used to study chip formation and tool wear when cutting with carbides, CBN and PCD tools under nominally the same conditions. The predominant wear mechanisms for each of the tool materials was found to be based on a diffusion/dissolution process. The wear process is discussed in detail for each of the tool materials and reasons advanced for observed differences in performance when removing material from a titanium alloy workpiece. The wear resistance and quality of the machined surface was found to be superior when cutting with the ultra-hard materials than with the carbide grades and in particular the PCD tool was found to produce exceptionally good surface finish. In the case of coated carbide tool grades rapid removal of the coated layers occurred leaving the substrate vulnerable to reaction with the workpiece material and this is considered to explain the seeming absence of beneficial effects when cutting with these grades.

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This thesis is concerned with the design, control and performance evaluation of a novel design for mechanical drives. This drive operates in a pulsed manner where energy is extracted from the input, stored and then released to the output. A spring acts as the energy store and brakes and clutches control the extraction and release of energy. By controlling the storage and release of this energy the device's output velocity can be controlled independently of the input velocity and since theoretically there is no energy loss the device operates in an analogous fashion to a variable ratio gearbox. Two design variations are presented. A step-up mechanism that is unidirectional and capable of output velocities greater than the input, and a step-up/stepdown device that has bi-directional output velocity capabilities with no theoretical constraint on the value of output velocity. A prototype drive for each design is evaluated and detailed mathematical models are presented and compared to the prototypes. In addition a detailed design methodology is put forward for step-up/stepdowndevices.

Thc devolopment of scene changing machinery in Great Britain is perhaps one of the few disciplines in the field of mechanical engineering which have virtually never relied upon new discoveries in technology for their advancement. Instead it has always lagged behind, perhaps modifying, certainly adapting, existing techniques. This study aims to examine the evolution of stage machinery during the nineteenth century, when many techniques had already been in existence and traditions firmly established since the previous century. The degree of development in the course of the nineteenth century was in many ways a reflection of the type of drama presented. As time went by, the public's taste for spectacle and visual presentation intensified and fostered an increase in the complexity of scene changing equipment. This in turn meant that many of the theatres built in the eighteenth century, especially in the provinces, were sadly inadequate for housing the vast quantities of equipment which machinists needed to install above and below the stage. As a result architects, began improving and enlarging existing theatres as well as building new ones, with increased stage width and depth, increased flying space above and increased depth below the stage.There was indeed an enormous rise in demand for scenic effects shortly after the beginning of the nineteenth century. This rapid growth caused the smaller existing Georgian playhouses, like the Theatre Royal, Ipswich, either to be modified in an attempt to cater for new trends, or to close. This dilemma alone must be acknowledged as a significant contributory factor in the decline of the Georgian playhouse and helps to explain the comparatively small number of such theatres surviving to the present day.The techniques of the stage machinist in the first half of the nineteenth century relied almost totally on technology and basic engineering principles which had existed for many years. Certainly the comparison often made between the backstage of a theatre of this period and a sailing ship is a very apt one, since both relied on manually hauled ropes, sheaves and the principles of mechanical advantage. However, these techniques had also been utilised for other, non-theatrical purposes. For instance, housed in the central tower of Beverley Minster is a large treadwheel, which was, and is still, used to raise equipment from ground level into the roof space [sec photo.1]. This is based upon the principles of mechanical advantage, in much the same way as many pieces of scene-changing equipment.Thus, because the theatrical profession was slow to adopt now apparatus and constantly replacing old machinery with brand new near-replicas, its evolution was comparatively slow. The job of a stage machinist was quite often a family concern, as the techniques, traditions, secrets and tricks of the trade were passed from father to son. The Sloman family and the Grieve family were particularly well known in London for their knowledge and expertise in this hold. Change was to a greater or lessor extent resisted and in any case many saw little need for change, especially those who were steeped in the traditions of the machinist and his machinery. It was, in fact, this basic resistance which caused a disruption in the evolutionary development of stage machinery. Many theatre architects were happy to furnish a traditional stage machinist with a blank drawing denoting "The Stage", requiring him to fill in the details as he saw fit, whilst the innovators devised all manner of new equipment, that which worked and sometimes that which emphatically did not. There was therefore a bifurcation, with the 'traditional school' refining the 'English wood stage' to a higher degree of sophistication, whilst the 'modern school' developed and attempted to apply the engineering technology associated with other disciplines. In essence, the latter attempted to replace muscle power with hydraulic or electrical power.This thesis documents the development of stage machinery from its comparatively primitive state at the beginning of the nineteenth century, through years of growth and expansion, and finally into the last decade of the century, when theatrical productions were in truth exercises in spectacle.

This thesis considers the classification of physical states in a simplified gearbox using acoustical data and simple time domain signal shape characterisation techniques allied to a basic feedforward multi-layer perceptron neural network. A novel extension to the signal coding scheme (TES), involving the application of energy based shape descriptors, was developed. This sought specifically to improve the techniques suitability to the identification of mechanical states and was evaluated against the more traditional minima based TES descriptors. The application of learning based identification techniques offers potential advantages over more traditional programmed techniques both in terms of greater noise immunity and in the reduced requirement for highly skilled operators. The practical advantages accrued by using these networks are studied together with some of the problems associated in their use within safety critical monitoring systems.Practical trials were used as a means of developing the TES conversion mechanism and were used to evaluate the requirements of the neural networks being used to classify the data. These assessed the effects upon performance of the acquisition and digital signal processing phases as well as the subsequent training requirements of networks used for accurate condition classification. Both random data selection and more operator intensive performance based selection processes were evaluated for training. Some rudimentary studies were performed on the internal architectural configuration of the neural networks in order to quantify its influence on the classification process, specifically its effect upon fault resolution enhancement.The techniques have proved to be successful in separating several unique physical states without the necessity for complex state definitions to be identified in advance. Both the computational demands and the practical constraints arising from the use of these techniques fall within the bounds of a realisable system.

Poly(ethylene terephthalate), PET, which is commonly used as a packaging material, is not degradable in nature. As an issue of sustainable development it must be recycled and converted into other products. During this process, extrusion is an important unit operation. In extrusion process, if the operating conditions are not controlled, PET can go under degradation, which results in the loss of some mechanical properties. In order to overcome the degradation of recycled PET (RPET), this study aims the control of the extrusion process. Dynamic models of the system for control purposes are obtained by experimental studies. In the experimental studies, screw speed, feed rate and barrel temperatures are taken as process variables in the ranges of 50 &ndash / 500 rpm, 3.85 &ndash / 8.16 g/min and 270 &ndash / 310 oC respectively. Singular value decomposition (SVD) technique is used for the best pairing between the manipulated &ndash / controlled variables, where screw speed is taken as the manipulated variable and molecular weight of the product is taken as the controlled variable. PID and model predictive controller (MPC) are designed utilizing the dynamic models in the feedback inferential control algorithm. In the simulation studies, the performance of the designed inferential control system, where molecular weight (Mv) of the product is estimated from the measured intrinsic viscosity ([&amp / #951 / ]) of the product, is investigated. The controller utilizing PID and MPC control algorithms are found to be robust and satisfactory in tracking the given set points and eliminating the effects of the disturbances.

GPS/INS (Global Positioning System / Inertial Navigation System) brings possibility of relaxing the demand for aerial triangulation in stereo model construction and rectification. In this thesis a differential rectification algorithm is programmed with Matlab software for aerial frame camera images. This program is tested using exterior orientation parameters obtained by GPS/INS and images are ortho-rectified. Ground Control Points (GCP) are measured in the orthorectified images and compared with other rectification methods according to RMSE and mean error. Besides, direct georeferencing accuracy is investigated by using GPS/INS data. Therefore, stereo models and ortho-images are constructed by using exterior orientation parameters obtained with both aerial triangulation and GPS/INS integration. GCPs are measured in both stereo models and ortho-images, compared with respect to their RMSE and mean error. In order to determine Digital Elevation Model (DEM) effect in ortho-rectification, different DEM data are used and the results are compared.