Published work concerning the influence of tooth geometry on hacksaw blade performance has been reviewed. By testing standard and modified hacksaw blades the author has shown that, contrary to previous belief, pitch is not a parameter which affects blade performance. Furthermore experimental evidence is presented to show that gullet size and shape significantly affect blade performance. The author proposes that restriction of chip flow by the gullet causes very inefficient metal removal. This is supported by examination of hacksaw chips, and a theoretical model has been developed to show how rapidly cutting forces increase when the chip is restricted from flowing. Two testing procedures have been developed to examine chip formation in the gullet. The first procedure employs video equipment to show chip formation and cutting forces simultaneously on one VDU, during cutting with single hacksaw teeth. This test is of limited use due to the slow cutting speeds employed. The second procedure, also using single teeth but cutting at realistic speeds, was capable of testing any tooth/gullet geometry cutting any material. The test results confirmed that restriction of chip flow by the gullet produces inefficient cutting. It has been shown that a particular tooth/gullet geometry can only cut efficiently over a limited range of feeds and workpiece lengths. The author has developed a method for accurately predicting sawing rates from the single tooth data gathered. The information gathered from the single tooth tests has enabled the author to isolate the most important aspects of tooth geometry affecting blade performance, and as a result, a new tooth design has been developed which performs better than the standard tooth.

This thesis is the summary of the research work that has been carried out by the author on the development of methods of optimum gear design and shaft design for gear boxes, and the integration of the methods into one software package together with parametric layout drawing. The objective of the optimum gear design is to minimise the gear centre distance with a fixed aspect ratio of pinion, when power capacity requirement is given. Although power capacity is dependant upon many factors, the optimum gear design method has used module, numbers of teeth, and helix angle as the significant variables. The power capacity rating is calculated by AGMA standards and the optimum design method is based on a study of the numerical behaviour of the AGMA power capacity rating and transformation of the gear design constraints into direct limiting boundaries on design variables. Numerical example tests show that the method is efficient and effective in finding the global minimum centre distance design. The shaft component design method is based on established theories for reaction calculation, bearing life rating, shaft stress calculation and shaft failure criterion. However, the layout of the gear box is defined by a unique system using vectors connecting shaft and gear centres. The gear design and shaft design methods are implemented in an integrated software package and a well defined data organisation provides the basis for data sharing. The definition of layout by centre vectors also serves as the reference frame around which to draw the layout by parametric programs. The design results of the software package are obtained by parametric programs from a data file based on the same data organisation. Parametric programs for individual shaft, bearing, and gears are written to draw the components and main dimensions such as centre distances, component axial positions, gear sizes and bearing sizes are shown on the layout. The contribution to knowledge by this investigation is mainly in the gear design area, viz., the study of the numerical behaviour of AGMA standards in relation to gear geometry and the development of the efficient and effective algorithm for the optimum gear design. The descriptive layout definition by centre vectors is also a novel feature.

This work is concerned with track spring components manufactured by Pandrol from a SiMn alloy in the quenched and tempered condition. For many years low to medium carbon based spring steel has been manufactured via an oil quench temper route producing components with suitable mechanical and microstructural properties. The current problem facing the spring manufacturer with the traditional heat treatment route involve a number of technical issues including a sensitivity to temper embrittlement and susceptibility to stress corrosion cracking. In addition, economic factors and component handling problems led Pandrol to seek solutions via the manufacturing process and materials selection. A programme of research was therefore proposed to identify a possible replacement alloy system and production route which could exclude the costly tempering operation and instil a degree of production control. The initial program of work involved the examination of several alloy systems based loosely around three separate microstructures, i.e. a fully pearlitic, bainitic and martensitic microstructure. In turn, each alloy was examined and assessed with respect to their suitability for the industrial application given their mechanical properties. From the initial research, a selected number of promising alloy systems were examined further, namely a chromium molybdenum alloy, salt bath quenched to produce a bainitic microstructure, a water quenched low carbon chromium and low carbon boron martensitic type alloy. The low carbon boron alloy was considered the most promising, with similar mechanical properties in both the plain bar and clip form compared to the existing Pandrol alloy. However, concern was raised over the amount of plastic deformation (permanent set) suffered by a clip component whilst in service. In response to this, the use of cold work was examined to further strengthen the microstructure with notable success. On identifying several possible alternative alloy systems to replace the existing oil quenched and tempered variant, the second stage of this research work concentrated on understanding the degree and type of microstructural strengthening involved on each particular alloy system. The effect of plastic deformation in each alloy type was also thoroughly investigated via transmission electron microscopy / true stress strain analysis and an attempt was made to relate microstructural changes to obtained mechanical properties. In addition the work hardening characteristics of the tempered microstructure were investigated, and compared to the straight through hardened variants. Qualitative Transmission Electron Microscopy studies confirmed that dislocation density/mobility played a crucial role in determining the work hardening rate. This project has studied the phenomena of work hardening in body centred cubic materials in the through hardened and untempered condition. A series of novel alloys have been developed with strengths equal to or above an oil quenched and tempered counterpart. However, these new alloys do not require a temper treatment thereby removing the risk of temper embrittlement. A clearer understanding of the work hardening characteristics has been developed through an assessment of the work hardening coefficient of these material variants.

No description available.

Development of manipulators that interact closely with humans has been a focus of research in fields such as robot-assisted surgery The recent introduction of powered surgical-assistant devices into the operating theatre has meant that modified industrial robot manipulators have been required to interact with both patient and surgeon Some of these robots require the surgeon to grasp the end-effector and apply a force while the joint actuators provide resistance to motion In the operating theatre, the use of high-powered mechanisms to perform these tasks could compromise the safety of the patient, surgeon and operating room staff. In this investigation, a two degrees-of-freedom (2-DoF) manipulator is designed for the purpose of following a pre-defined path under the direct control of the surgeon.

Advanced ceramic materials are assuming increasing industrial importance because of their special properties. However, the extreme hardness and brittleness of these materials make their machining efficiency low. The difficulty arises from shaping ceramics whilst conserving their surface integrity, strength and high quality surface finish. Manufacturing processes such as grinding with diamond bonded wheels present one solution. The use of a diamond grinding wheel on the surface of ceramics, creates a complex system of elastic/plastic deformation, and subsequent cracking. For ceramic materials such as silicon nitride, two types of damage can occur; firstly surface damage in the form of machining marks which cause stress concentrations and surface cracks and secondly sub-surface cracking. These problems caused a major delay in the utilisation of these materials in the aeronautics industry. This research was aimed at providing a better understanding of the grinding process and parameters involved in machining ceramic component. An extensive preliminary study was carried out to understand the behaviour of advanced ceramic material during grinding. The effect of very high infeed and grinding wheel parameters were studied as an initial investigation. A system for on line detection of grinding wheel surface condition during grinding was developed during this research. Acoustic emission AE technique to monitor the wheel condition was also investigated during the experimental work. The grinding machine used is a commercially available machine with a stiffness coefficient of 18.5 N/μm. The machine was modified to accommodate a higher feed rate. The purpose of using this machine was to investigate how a commercial machine would grind hard material such as advanced ceramics and what the effect would be on the process of crack initiation and propagation during grinding. The effect of different grinding wheel and machine tool parameters on crack initiation and propagation was investigated and represent the main concern of this research. Experimental design using modified L27 orthogonal array was used. The response of the surface roughness, fracture strength, AE spectral amplitude, grinding forces, grinding energy, crack size, sub-surface cracks distance from the ground surface, depth of surface damage due to different grinding wheel and machine parameters used in the fractional factorial array were all investigated. Three basic types of cracks that were found to occur after the passage of an abrasive grain on the surface of ceramics materials were identified. These are radial, median and lateral cracks. Only radial cracks and machine marks are visible on the surface, median and lateral cracks (parallel to the surface) are formed below the affected zone and thus not visible. The load of an individual grain and its shape on the grinding wheel surface were found to have an influence on the crack initiation and propagation. Higher damage depth on the ground surface was measured when the grain size increased or was extremely sharp. Median cracks were found to be at a deeper location from the ground surface (2-15 μm) compared with lateral cracks. The dimensions and depth of median cracks beneath a ground surface was found to increase when the levels of grinding wheel grit size, wheel bond hardness, depth of cut and table feed were increased. However, locations of lateral cracks were found not to be affected when theseparameters increased and found to occur at 2-4 μm below the surface. The median cracks were located close to the ground surface at low table feed rates compared with deeper location when the table feed rate increased. A correlation between AE, SEM and 3D data and the ground surface condition was carried out. The condition of the ground surface whether smooth or rough was identified and linked with AE signals. The link between these observations show that an increase in percentage of surface fracture is accompanied by low-amplitude long­ duration events which can be assumed as the characteristic of brittle mode grinding. This observation was confirmed by the SEM and the 3D observations. Higher AE spectral amplitude was found to be associated with smooth ground surfaces. However, sub­ surface median cracks were found for this condition. This correlation was the first reported attempt to link different experimental measurements and parameters. Different artificial cracks were initiated on ceramic specimen surfaces in both longitudinal and transverse directions using v-shaped discs. This method of initiating cracks is more realistic than that produced by a single diamond scratch. The very random nature of diamond grit shape, size and location on the surface of the wheel would alter the characteristics of a crack initiated in a real grinding process. This technique used for creating an artificial crack is the first reported attempt hitherto. The groove generation mechanism observed using SEM was almost brittle when the depth of scratch increased. At larger groove depths, a deeper locations of sub-surface median cracks were found. Grinding processes were then carried out on these cracks to investigate their propagation. The AE spectral amplitude was found to be higher for specimens ground with artificial cracks compared with specimens ground without artificial cracks. The sub-surface cracks initiated due to grinding specimens with artificial cracks were found to be at deeper locations than to those for ceramic specimens ground without artificial cracks. The effect of remaining damage depths on the ground surface on the fracture strength were also studied. Increasing the diamond grinding wheel grit sizes, wheel bond hardness and table feed were found to be the most influential factors that increase the propagation distance of the artificial cracks during grinding. A computer model based on finite element analysis package was used to study the behaviour of the ceramics in grinding. This package was used to establish a theoretical model which was validated using experimental results. Normal and tangential grinding forces from experimental work were used as input to the FE model. These forces were chosen to indicate different wheel and machine parameters. The model simulates the process of grinding by applying these forces on the surface of the ceramic specimen to study the crack initiation, propagation and their distance from the ground surface. A complete simulation for the grinding process was made including removal of material during the process.

Published work concerning the performance of coated and uncoated carbide tipped circular saw blades has been searched and reviewed. The search has shown that little similar experiments on the carbide tipped circular saw blades have been conducted. Furthermore the evidence shows that no work has been published on the application of coatings to the carbide tipped circular saw blades. Finite element analysis has been widely applied to the cutting process, but the application of finite element methods to the carbide tipped circular saw blade is still a new area of research. In this investigation the performance and life of the carbide tool both uncoated and coated were quantified by rigorous measurement. The proposed carbide properties ( composition, cobalt distribution, specific gravity, micro-structure and red hardness of carbide) have been experimentally tested. The failure modes for the carbide circular saw blades and carbide tipped saw segments have been established. In this work a novel experimental approach was used, in which TiN and TiAlN coatings were applied to the carbide tipped circular saw. A feature of this approach is that a lower coating temperature is used and yet still retains the good bonding strength between the substrate and the coating. The parameters obtained in this investigation were used as a basis in the development of a finite element model. This model was used to optimise tooth geometry and predict the failure mode with respect to temperatures and stresses. Investigation has shown that TiN and TiAlN coatings have largely enhanced the tool life in the case of cutting proposed workpiece materials. The crater wear, flank wear and large chipping have been arrested or reduced. Computer model and transverse rupture strength figure have been established. The results shows that the model used for qualitative analysis of a problem is possible and the examples conducted in the case of cutting mild steel is completely consistent with the failure modes obtained in the cutting tests.

Porous air bearings enjoy some important advantages over conventional air bearing types such as increased load carrying capacity, higher stiffness and improved damping. However, these types of bearings have yet to find widespread acceptance due to problems with obtaining materials with consistent permeability, instability issues relating to the volume of gas trapped at the bearing surface in the pores, and manufacturing the bearing without altering the permeability. Using a series of fine grades of alumina powder to minimise surface pore volume it has been demonstrated that it is possible to consistently and reproducibly manufacture porous bearings by injection moulding and slip casting. The relationship between powder size, processing conditions, porosity, mechanical properties and fluid flow characteristics were experimentally determined. The temperature of processing and the green density were found to be the controlling parameters in the resulting fluid flow properties for a given powder size, Test bearings were produced from the range of processing conditions investigated. It was found that the fine powder size bearings were stable over the entire range of test conditions irrespective of their initial manufacturing route. The most important consideration for the bearing performance was the quality of manufacture. The bearings were found to be sensitive to the flatness of their working surface and quality of fit in their test holder. The bearings were compared with published theories for load capacity and stiffness. A reasonable agreement was found with load carrying capacity once a correction for surface roughness was incorporated. Stiffness predictions provided a useful tool for the analysis and prediction of properties such as optimum values of permeability for a given geometry, if certain allowances are made.

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.