A device based on an adaptation of the Christopherson tube is investigated for the lubrication and other effects of employing a polymer melt as the lubricant during the wire drawing process. The device is heated to convert the polymer feed into a viscous melt and the pressure required is generated by a hydrodynamic action produced by the motion of the wire. On the basis of experimental evidence, it is apparent that deformation commences before the wire reaches the die, in the Christopherson tube itself, with the die effectively acting only as a seal. Under these conditions, the die geometry becomes of. secondary importance and the deformation actually takes place as if an effective die of continuously changing die angle is being used. To take this aspect of the process into account, a mathematically described effective die shape is used in the present analysis. The plastic strain hardening properties and the strain rate sensitivity of the wire material are also incorporated into the analysis. The study utilises an empirical expression relating shear stress and rate of shear together with an experimentally derived pressure coefficient of viscosity, in determining the coat thickness possible on the wire. The theory contains the effect of a limiting value to the shear stress, which exhibits itself as slip in the polymer. An alternative theory is also presented which assumes that shear stress is zero at the polymer/tube interface. This much simplified analysis allows the length of the deformation zone to be determined. An extensive series of experimental studies have shown that the coat thickness reduces both as speed increases and as the wire material strength increases. Predictions of coat thickness from the analysis tend to be lower than those obtained experimentally. At low drawing speeds a coat defect was observed which gave the coated wire a "bamboo" shape. It is probable that this defect is caused by the slip-stick nature of the polymer melt in the Christopherson tube. The assumed die shape and predicted pressure distributions are verified by experiment.

Planing and moulding operations carried out within the woodworking industry make extensive use of rotary machining. Cutter-marks are produced on the timber surface which are generally accepted as unavoidable. More noticeable surface defects may be produced by such factors as cutter-head imbalance, and until recently most research has concentrated on removing these defects. When a high quality finish is required, a further machining operation, such as sanding, is often required to remove cutter-marks. What is required, is a modified machining process which combines a surface closer to the ideal fixed knife finish, whilst retaining the flexibility, practicality and cost effectiveness of rotary machining.

The principal objectives served by the research were the development of productivity measurement systems at firm level to evaluate the comparative productivities of products or product groups and individual manufacturing plants operating batch production.

British industrial productivity (in terms of value added per employee) and industrial performance have reportedly been declining in recent years. This decline has been blamed on, among other factors, poor production management. This has generated considerable interest in the function and led to several studies of production management and the production manager's job. After an extensive review of these studies, it was felt that they were mainly descriptive in nature and generalistic in their analysis. Some of these studies were regional in character and biased in certain other respects, and could not therefore represent the true national picture of the production manager's job.

No description available.

No description available.

No description available.

The Hydroson system is a novel cleaning system which has recently been adopted to solve cleaning problems in many industries, particularly in metal finishing. Although effective the fundamental principles and mode of action of the process are not fully understood. In this work, the Hydros on system was quantitatively evalued and compared with other methods of cleaning. Further, the mechanism of cleaning was studied and was shown to be due to the scouring action produced by the impingement of the high pressure jets on the contaminated surface. The rate of cleaning was comparable with ultrasonic cleaning at a frequency of 13 KHz and intensity of 520 Wm[-2]. The effect of Hydroson agitation was studied on the electrodeposition process using an alkali zinc electrolyte with and without addition agents. Hydroson agitation reduced the diffusion layer thickness at the cathode to a similar value compared with ultrasonic agitation, and gave many beneficial effects on the properties of both the electrolyte and the deposit. It reduced cathodic and anodic polarization, increased the cathodic current efficiency and maximum current density, thus allowing good quality deposits to be obtained even at higher current densities. The deposit from the zincate bath without addition agents was less porous, had a finer crystallite structure and was harder than those formed from solutions with no agitation, with magnetic stirring to give a flow rate of 20 cm s[-1], or with ultrasonic agitation. In the zincate bath with addition agents, Hydroson and ultrasonic agitation increased the hardness, but reduced the brightness of the deposit. Hydroson agitation was also shown to increase the rate of electrolytic recovery of zinc metal from dilute zincate solutions by 3-4 fold compared with magnetic stirring. The flow velocity of solution across a surface in the centre of the Hydroson tank was determined by a theoretical and experimental approach and was found to be approximately 1.2 ms[-1].

The main achievement of this research is the development of a genetic algorithm model as a solution approach to the single model assembly line balancing problem (SMALBP), considered a difficult combinatorial optimisation problem. This is accomplished by developing a genetic algorithm with a new fitness function and genetic operators. The novel fitness function is based on a new front-loading concept capable of yielding substantially improved and sometimes optimum solutions for the SMALBP. The new genetic operators include a modified selection technique, moving crossover point technique, rank positional weight based repair method and dynamic mutation technique. The moving crossover point technique addressed the issue of propagating best attributes from parents to offspring and also supports the forward loading process. The new selection technique was developed by modifying the original rank-based selection scheme. This eliminates the high selective pressure associate with the original rank-based technique. Furthermore, the modified selection technique allows the algorithm to run long enough, if required, without premature convergence and this feature is very useful for balancing more complex real world problems. The repair technique included in this model repairs a higher proportion of distorted chromosomes after crossover than previous methods. Moreover, a third innovative feature, a moving adjacent mutation technique, strengthens the forward loading procedure and accelerates convergence. The performance of the front-loading fitness function currently outperforms the published fitness functions and fifty-four published test cases generated from sixteen precedence networks are used to assess the overall performance of the model. Encompassing the new genetic algorithm concepts, forty-four test problems (81%) achieved the best solutions obtained by published techniques and twenty-four problems (44%) produced better results than the benchmark Hoffmann precedence procedure, the closest non-genetic algorithm method. The superiority of the genetic model over other heuristics is identified in this research and future developments of this genetic algorithm application for assembly line balancing problems is evident.

Brazing may be described as more of an art than a science , there is little comprehension of the basic mechanisms governing brazing in air or vacuum. Consequently the behaviour of the Gold 18% Nickel brazing alloy in vacuum was studied using the novel techniques of hot-stage scanning electron microscopy with simultaneous bulk and surface analysis. The work demonstrates that careful control of experimental conditions allows both Auger electron and X-Ray spectroscopies (AES and EDXA) to be carried out at high spatial and energy resolutions , with good signal to noise in a realistic analyical time. Combining post-brazing examination of samples heated in a UHV oven , with real-time studies of braze powder/substrate combinations on a heating stage in an Auger microprobe , revealed several important mechanisms. Vacuum brazing is a two-stage process; oxide penetration followed by wetting and spreading via a suboxide route. AES analysis showed that oxide penetration is achieved by reduction as a result of low oxygen partial pressures and high carbon activities , in the system as a whole , or locally (for example under or around a molten braze droplet) , leaving an oxide-free surface , or a discontinuous , penetrable oxide. After penetration has occurred wetting and spreading continues along the metal/metal-oxide interface. Flow may be impeded by residual oxide resisting the advancing liquid which is trying to disbond it. Alternatively , interdiffusion of the braze metal and substrate allows pick-up of elements which raise the melting temperature of the braze alloy and causes solidification. EDX analysis and digital element mapping during interdiffusion and solidification illustrates that the periphery of the braze pools are most affected , and that further elevating the temperature initially caused remelting , but eventually resulted in second phase formation in accord with the Au/Ni/Fe equilibrium diagram.