M.Ing. (Electrical & Electronic Engineering) / In recent years, there has been a renewed interest in the synchronous reluctance machine, because it holds so many promises according to the mathematics. In the past very little research has been done in this field, due to the problems of controlling the machine and the necessary technology had not yet- been developed. When the machine is running synchronously, it can be very accurately controlled and is therefore suited for applications in the paper or textile industry. In this dissertation the possibility of accurately controlling the machine without the use of a position/speed sensor on the rotor will be investigated.

Many modifications have been made in the past to the conventional drill points and references to the better performance of curved lip drills when cutting cast iron can be found. Similar drill points do not seem to be as successful with steel. The objective of this research was set to analyse drill design and to study the effect on drill performance of changing the drill conventional flute form when cutting steel. Changing the conventional flute form has an immediate effect on the shape of the drill lip - it is no longer a straight cutting edge.

For a gear designer, the meshing gear tooth root bending stresses, and contact stresses are of major importance. To be able to obtain accurate values of these stresses, it is essential to determine the actual load distribution along the contact lines of the meshing gear tooth pairs. this load distribution. The objective of this work is to predict In the current gear design standards such as AGMA 2001¹, B5436², DIN3990³ and 150-0156336⁴the contact line load distribution is estimated by using a two-dimensional "thin slice" model of the meshing gear teeth. Clearly, this cannot account accurately for maldistribution of loading across the tooth face width, which is essentially a three-dimensional phenomenon. As a result, the effects of tooth lead, profile and pitch deviations are inadequately modelled. In this work, the elastic compliance of wide-faced helical gears of standard tooth form, zero addendum modification, and between 10 and 100 teeth, was determined using a 3-D finite element elastic model of the whole gear. These results were incorporated into a micro-computer program which calculates the load distribution across the meshing tooth pair faces. The effects of a number of parameters such as U, Z, b, and β* on the load distribution and contact stresses of an error-free gear were also investigated using the micro-computer program and the results were compared with other published data and those obtained from the standards²,³,⁴ Vedmar⁵ and Simon⁴³. The load peaks near the start and end of contact, attributed by some⁶,⁷ to the resistance of the unloaded portion of the tooth beyond the shorter contact lines in those regions, is very clearly demonstrated by Vedmar⁵, others⁶,⁷ and this work, but certainly not by the standards (this effect is usually referred to as the "buttressing" effect). The thin slice model largely over estimates the tooth mesh stiffness cγ since the convective effects of loading are completely ignored. The effects of lead deviations such as helix angle error and face crowning (barrelling), profile deviations such as profile angle error, profile crowning and tip relief, and pitch deviations such as adjacent base pitch error, were also studied. Their effect on the load distribution factors KH(3' KHO! and the overall load distribution factor KH, were obtained from the compared with the results from the standards2,3,4. micro-computer program and As expected, the standards considerably overestimate these factors due to their overestimation of mesh stiffness. Nevertheless, the pattern of variation in the load distribution factors was similar. The theoretical predictions were compared with experimental results measured on wide-faced test gears (specifications given in Table 5.1) with known (measured) mounting and tooth form errors. Measurement of tooth root strains to determine the load distribution along the simultaneous contact lines showed that the experimental and theoretical results agreed on the average to within 3.5% (end of tooth results not included). Also the total applied load upon comparison with theory agreed to within 6%. Experimental absolute values of transmission error "ft" were not available, however, the pattern of variation of 11ft" during meshing showed excellent consistency with the theoretical results (variations were very small anyway and within the error band). A separate test however, which gave the approximate absolute transmission error (tooth misalignments and form errors not included) agreed to within 1 % with theory.

This thesis is concerned with the dynamic behaviour of oil lubricated journal bearings and particularly with the small vibrations about the equilibrium position known as 'oil whirl'. The importance of shaft flexibility and oil film cavitation to this phenomena are investigated. Several authors have shown that by the use of linear techniques it is possible to derive a stability borderline which can be used for design purposes to ascertain whether or not a bearing is stable. These linear techniques are used to examine journal bearings with flexible shafts operating under a range of cavitation boundary conditions. It is demonstrated that these boundary conditions, particularly the behaviour of a lubricant during a vibration, play a crucial role in determining the predicted stability of the bearing. The effect of shaft flexibility is to make the bearing less stable, but the extent of this change is also governed by the oil film behaviour. Nonlinear analytical techniques are used to carry out an investigation into the behaviour of a journal bearing operating with a rigid shaft close to the stability borderline for a particular set of cavitation boundary conditions. It is found that two types of behaviour are possible: (i) supercritical, in which small stable whirl orbits are possible at speeds just above the threshold speed (the speed above which the bearing is unstable according to linear theory). (ii) subcritical, in which small unstable orbits exist at speeds just below the threshold speed. The parameter space is split into two regions, one subcritical and the other supercritical. Several methods are used in the investigation; it is shown that the methods give identical results, but only if they are applied correctly. These results are subsequently confirmed by a numerical integration of the equations of motion. The thesis concludes with an investigation of the application of nonlinear techniques to a variety of cavitation boundary conditions

In recent years, sewing technology has witnessed dramatic increases in machines speeds, new types of materials, new sewing threads and evaluation methods – but the principal type of sewing machine remains the lockstitch type and this is likely to remain the most common and versatile for the foreseeable future, particularly for sewing woven fabrics. Sewing machine speed increases lead to a loss of control of the sewing process due largely to an increase of the dynamic forces and consequently to problems such as seam pucker. In this research computer-based instrumentation and high-speed digital image and signal acquisition systems were developed to study the dynamic effects of the sewing machine, fabric and thread on seam pucker. Needle thread tension, needle bar pressure/tension, presser-foot pressure and displacement signals were acquired simultaneously by 4 strain-gage/piezo-quartz sensors mounted on a Pfaff-563 machine and results were related to pucker measured by a CCO colour-video camera system integrated with the sewing machine. A series of experiments conducted on various types of fabrics provided illustrative examples of the characteristics of each signal acquired (distinctive shape, amplitudes-peaks valleys locations, duration etc), and also enabled their characteristics to be compared and the interactions among the signals to be studied. For example it was found that the increases in magnitude of the dynamic forces in relation to sewing machine speed increases from 200rpm to 5500rpm were lower than expected (needle thread tension 2.6 fold, presser-foot 1.2 fold and needle penetration force 3.2 fold). A comparison of the needle thread tension for standard woven fabrics and micro-fibre fabrics showed a significant difference in the signal shape, location and amplitudes. The instrumentation developed is located at the Institute of Textiles and Clothing of the Hong Kong Polytechnic University in Hong Kong.

M.Ing. (Engineering Management) / Please refer to full text to view abstract

M.Ing. / Until very recently reactive maintenance was still used in the mining industry. Equipment failures occurred without warning and resulted in catastrophic breakdowns and large production losses and maintenance cost. As a result, the mining industry turned to preventative maintenance that focused on changing parts before they fail. Although preventative maintenance was an improvement over reactive maintenance practices, equipment reliability did not necessarily improve. Next came predictive diagnostics, which monitored the health of components within assemblies, and thereby predicting the life expectancy of assemblies through vibration analysis, infrared thermography, lubrication and oil analysis and ultrasonic detection. However, the level of success could not be achieved. Many hours and a lot of money are spent in developing and implementing a maintenance management system, but without the correct approach, efficient maintenance might not be achieved. The overall objective of this dissertation is to introduce a logical approach to managing the maintenance of mining equipment over the economical life of the equipment. This concept can be defined as Life Cycle Management. The research included in this dissertation is partially aimed at developing the Life Cycle Management program for P&H MinePro Services A division of Joy Global (South Africa) (Pty) Ltd. The dissertation also includes case studies on the P&H Mining Equipment (Blast Hole Drills) and their alliance partners (LeTourneau Front-end Loaders). The dissertation focuses on the cradle to grave approach of maintenance for mining machinery, referred to as the Life Cycle Management of Mining Machinery.

M.Ing. / South Africa is presently experiencing a power shortage problem. This has led to numerous investigations into generating needed capacity and finding ways of saving power where possible, in order to sustain an acceptable extra capacity of at least ten percent. This dissertation investigates the possibility of saving power consumed by the electrical boiler feed pumps through engineering management strategies. The technical system drive unit is considered as a case study and consists of the following electrical and mechanical components: • Boiler feed pump. • Boiler feed pump transformer. • Variable speed drive. The methods identified to improve the Variable Speed Drive (VSD) system reliability and obtain total efficiency are: • Technical evaluation of the system. • Engineering management tools including reliability and availability. • A strategic focus on reliability improvement. Technical evaluation of the system includes evaluating the condition of the existing system and possibly replacing it with the latest technology should the system prove inefficient. Engineering management tools such as Total Quality Management (TQM) and Total Productive Maintenance (TPM) ensure that the plant is in a high state of readiness at all times. Strategic management issues in the broader context that influence reliability and availability management have been identified to improve productivity contributing to total organizational overall efficiency. One of the main research conclusions of the dissertation is that not only inherent reliability of a technical system is important but also the achievable reliability in the broader strategic organizational context. The research strategy was exploratory and included an integrated case study on electrical boiler feed pump drives.

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