The purpose of this project is to make a detailed technological and economic analysis of the current UK situation regarding the use of scrap rubber in order to identify the most effective processes and products. The scope of the investigation is restricted to the re-use of scrap rubber as a primary raw material for rubber product manufacture. The thesis emphasises the following aspects : (i) the structure of the rubber processing industry and the role of the rubber recycling sectors; (ii) property relationships in rubber compounds incorporating scrap rubber crumb, with particular attention to material mechanics; (iii) the estimation of curing agent distribution in a crumb incorporated rubber vulcanizate; and (iv) the economics of the cryogenic grinding of scrap rubber tyres. The property relationships of vulcanizates incorporating recycled rubber have been studied using several mathematical models : Gent, simple law of mixtures, Mooney-Rivlin models, and a non-Gaussian model based on a simplified form of inversed Langevin function. It was found that; (i) for some compounds the elastic modulus and strength could be described well by the law of mixtures for composites, (ii) the reduction in strength caused by the incorporation of crumb decreased with decreasing particle size but there is little advantage to be gained by reducing the size below 20 pm, (iii) different modes of failure may be operative, i.e. adhesive and cohesive, according to the strength of the matrix rubber. The redistribution of curing agent in our whole tyre crumb-rubber vulcanizates has been studied using the SEM and EDAX techniques. Although qualitative and quantitative evidence for the migration of cure agent from matrix to crumb is given, no evidence was found for an interfacial layer between the two phases which is depleted of cure agent. Little detailed information on the economics of the majority of commercially operated processes is available. Data has been obtained for the cryogenic grinding of scrap rubber, a technology which seems to show potential for commercial exploitation, and a thorough economic analysis performed. The result showed that, under currently depressed crumb prices and low demand, the most feasible of the plants considered is just marginally economically viable. It was found that the most important cost input to the cryogrinding process is the cost of cryogenic material (liquid nitrogen) and that the most important factor which governs the economic viability of the process is the price of the rubber crumb output. Socio-environmental and resource conservation factors indicate the desirability of Government support.

The problems encountered in attempting to determine the rate controlling step in the reduction of magnetite end sinters to iron are revealed by a survey of the pertinent literature. On the basis of previous work supplemented by the investigations reported in this thesis the probable sequence of rate controlling steps has been determined. Exhaustive metallographic and mathematical studies have been carried out on the hydrogen reduction of magnetite and lean magnetite sinter samples reduced in thermal balances. The existence of rate minima at 650°C and 900°C in the reduction of magnetite has been shown by metallographic techniques. Additionally the extent of chemical reaction and mass transport control has been shown by mathematical studies. Similarly the extent of chemical and transport control in sinter reduction has been shown metallographically and mathematically. The effect of thermal treatment in oxidising and inert atmosphere has been shown. The improvement in reaction rates as a result of particular thermal treatments has been displayed.

This thesis studies the operating behaviour of the manual unpaced lines, which are the most important of the flow lines' systems. The lines examined are unbalanced and six types of imbalance are considered, namely, the imbalances of mean service times, coefficients of variation (Covars), buffers'capacities, means and Covars, means and buffers, and Covars and buffers. It is argued that the deep understanding of the behavioural characteristics of such lines, contributes towards the achievement of practical solutions to many of their problems. The lines are simulated under both steady and non-steady states conditions, with positively skewed weibull work times distributions, different values of line length (N), buffer capacity (B), degree of imbalance (DI), and pattern of imbalance, utilizing full factorial designs. The data are subjected to the analysis of variance, multiple regression, multiple comparisons with control, pairwise comparisons, canonical correlation, and utilitv analysis A simple utility approach is also explored briefly. Some of the important conclusions for all the unbalanced lines' investigations are: (1) At least one unbalanced pattern generates superior idle time (I) and/or mean buffer level (ABL), over those of a balanced line. The superiority in I decreases as DI rises, whereas the advantage in ABL reduces as DI is decreased.(2) The DI of the best unbalanced pattern can substantially or moderately be increased and still yields approximately equal I to that of a balanced configuration.(3) If a line is unbalanced in the wrong direction, significantly inferior performance to that of a balanced design will result.(4) The unbalanced patterns' I tends to decrease, when N and DI reduce and B increases, while ABL falls directly with B.(5) The I's transient size increases as N and B become higher and DI increases, while the ABL's transient size rises whenever B reduces.

A detailed investigation is carried out for the novel process of Plasto-hydrodynamically produced wide strip. In this process the conventional die is replaced by a pressure head with a rectangular hole. The internal geometry of the hole is shaped such that a convergent fluid flow is produced. This flow causes the production of hydrodynamic forces within the pressure head, namely hydrodynamic pressure and surface shear stresses. These forces are of sufficient magnitude that plastic deformation is induced within the working material. An in-depth theoretical analysis has been undertaken to establish the relevance of the geometrical parameters of the pressure head for the control of deformation performance. An extensive study of the solution algorithm for this type of plasto-hydrodynamic problem is made and modifications introduced to improve die dynamic response of the model. A new non-Newtonian model of the process has been developed using a power law type constitutive equation for the fluid behaviour. The modifications to the solution algorithm were also included in this new model. The plasto-hydrodynamic models developed during this work were subjected to numerical optimisation. The non-linear pattern search algorithm was utilised for this purpose. Correlations between the optimum geometrical form for the pressure head and process velocity were established. A study was made of the effect of varying the non-Newtonian parameters and the optimum pressure head geometry. A Computational Fluid Dynamic (CFD) analysis was made of the Hydrostatic assumption. This assumption allows major simplifications during the derivation of the models of the process. Its validity is established along with the impact of side leakage on the pressure field. An experimental programme was undertaken to provide data to establish a correlation between the predictions of process performance and an analysis of the output form of the strip produced by the process. The material used for the study was commercially available soft copper strip. The maximum reduction in area produced was 12% approximately.

An understanding of the factors surrounding the achievement of specified quality requirements is imperative and hence a prerequisite for effective management of quality by the construction team. To this end, the research is concerned with identifying, with a high degree of certainty associated with the data, the cause and effect of quality problems directly related-to the site production process and to establish, quantitatively, the relative importance of the factors. Six hypotheses were postulated and their verification was based on balanced and honest conclusions drawn from the data analyses. Five of the six hy 3po thesesa re supported by the data. Therefore, they become explanatory theories for the management of quality in construction. As part of a literature survey, a critical review of the previous works was made and the current state of the art was identified. Based on the knowledge gained from the literature survey, three detailed case studies were made of construction projects in the South East of England, utilising different procurement methods. The case studies, in conjunction with the literature review, were used to develop conceptual models which in turn were used for structuring a detailed questionnaire intended to extend the research throughout England in order to achieve a sufficiently large category proportion'. The responses to the questionnaires were scientifically analysed and statistically validated. The data analysis results in the identification of 30 factors which are expressed as the causes of non-conformance to specified quality requirements. The relative importance of each factor was established. Therefore, a large cloud has been removed and the construction team can now direct their limited resources effectively. The second objective of the research was accomplished with the successful development of a new Quality System entitled "Quality Communication System" (QCS). The implementation of the QCS approach to the management of quality in construction will result in achieving conformance to specified quality requirements at first attempt, lower costs and increased productivity in the construction industry. The research outcome is a significant contribution to the management of quality in the construction process. The outcome is perceived to represent an advance in knowledge associated with construction management.

No description available.

Investigations of machining optical surfaces into brittle materials using an ultra precision machine tool are presented. The newly developed ultra precision NION machine is evaluated to gain a good appreciation of its operating performance. The machining accuracy capability of this machine is established by careful measurement of its motion accuracy, thermal and dimensional stability and loop stiffness. Corroboration of these measurements are provided by assessment of surfaces which were produced in soft 'easily machined' metal materials. It was found that surfaces smooth to -1 nm Ra could be produced on the NION machine and with a form error of less than 100 nm P-V. The main source of figure error, approximately 80 nm, was found to be caused by the synchronous axial error motion of the workhead spindle. Other elements of the machine, including thermal effects, incurred less than 25 nm of additional figure error. Assessment of the diamond turning process for the producing optical surfaces made in a number of important optical materials, which are ostensibly brittle, were undertaken. Turning tests were carried out to establish the relative difficulty for machining optical surfaces in these materials and to define the most important parameters which affect the attained surface quality. Assessment of the produced surfaces was based on their roughness quality, surface morphology and residual stress condition. It was found that diamond tool edge quality degraded with total cut distance. Tool cut distance was found to be a major influence on achievable material removal rate before micro-fractures became present at the surface. Surface quality and residual stress condition were also greatly influenced by the overall tool cut distance. Diamond grinding trials were also carried out using the NION machine tool. These grinding trials were carried out using a mode of grinding which permits complex shape optical surfaces to be produced. Various grinding technologies were employed to establish the optimum methods. Selected grinding trials were carried out to establish the dominate parameters affecting the optical quality. Assessment of the machined surfaces was in regard of their surface roughness, residual stress and severity of sub-surface micro cracking. It was found that grinding wheel specification was a major influence on surface quality and sub-surface damage. The level of residual stress associated with 'ductile' mode grinding was not found to prohibit its application toward the direct manufacture of optical elements. Selection of grinding parameters which ensured the grain depth of cut, GDOC, parameter did not exceed the materials critical depth, dc, allowed glass surfaces to be ground to 1-2 nm Ra. These ground glass surfaces appeared free of any surface fractures. Sub-surface assessments did however reveal small levels of micro-fractures hidden below the surface. Discussion of both machining processes is provided. Available material removal rates for each process is given when cutting a number of important optical materials. Conclusions regarding the production of both Infrared and visible wavelength optics using the NION machine tool are provided. Recommendations for future work to improve both the understanding of the processes and the effectiveness of applying the processes are suggested.

The recent developments in process plant design have made it desirable that a better understanding of transient compressor performance within the process plant be gained. The model outlined in this thesis is capable of representing most types of process plants. Further the number of degress of freedom, plus the dynamic flexibility of a poly- tropic analysis allow any system transient to be simulated, including compressor surge. A computer program has been developed from the model and validated using a small centrifugal compressor. The results showing successful simulation of compressor transient behaviour (including surge) are given. The model was then applied to study the transient behaviour of a natural Gas Transmission station. The model successfully highlighted compressor surge problems under certain operative conditions. This surge phenomenon is present in the trans- mission station and a possible solution to the problem was suggested due to the better understanding of dynamic response of station.

The recent years, the aerospace industry in particular has embraced and actively pursued the development of stronger high performance materials, namely nickel based superalloys and hardwearing steels. This has resulted in a need for a more efficient method of machining, and this need was answered with the advent of High Efficiency Deep Grinding (HEDG). This relatively new process using Cubic Boron Nitride (CBN) electroplated grinding wheels has been investigated through experimental and theoretical means applied to two widely used materials, M50 bearing steel and IN718 nickel based superalloy. It has been shown that this grinding method using a stiff grinding centre such as the Edgetek 5-axis machine is a viable process. Using a number of experimental designs, produced results which were analysed using a variety of methods including visual assessment, sub-surface microscopy and surface analysis using a Scanning Electron Microscope (SEM), residual stress measurement using X-Ray Diffraction (XRD) techniques, Barkhausen Noise Amplitude (BNA) measurements, surface roughness and Vickers micro-hardness appraisal. It has been shown that the fundamentals of the HEDG process have been understood through experimental as well as theoretical means and that through the various thermal models used, grinding temperatures can be predicted to give more control over this dynamic process. The main contributions to knowledge are made up of a number of elements within the grinding environment, the most important being the demonstration of the HEDG effect, explanation of the phenomenon and the ability to model the process. It has also been shown that grinding is a dynamic process and factors such as wheel wear will result in a continuous change in the optimum grinding conditions for a given material and wheel combination. With the significance of these factors recognised, they can be accounted for within an industrial adaptive control scenario with the process engineer confident of a more efficient use of time and materials to produce a higher quality product at lower cost.

No description available.