No description available.

No description available.

No description available.

No description available.

No description available.

A detailed study has been made of titanium carbide (TiC) coatings chemically vapour deposited on powder metallurgy (PM) BT42 grade high speed steel (HSS) indexable cutting tool inserts, in collaboration with Edgar Allen Tools, Sheffield. Initially, the characteristics of a TiC coating deposited under the standard conditions employed by Edgar Allen Tools were determined, both before and after the obligatory HSS substrate heat treatment. This was done using various techniques including x-ray diffraction, scanning electron microscopy, micro-hardness testing, profilometry, optical microscopy and scratch-adhesion testing. Although the characteristics of the TiC coating were found not to be significantly affected by the HSS substrate heat treatment, some of them were different to those presented in the literature for TiC coatings chemically vapour deposited on cemented carbide substrates. A comprehensive survey of the literature revealed that the process parameters employed during the chemical vapour deposition (CVD) of TiC coatings, particularly the CHy/TiCly mole ratio and deposition temperature, have a significant effect on coating characteristics. Consequently, it was decided to investigate the effect of these parameters on the characteristics of the TIC coatings chemically vapour deposited on the PM HSS inserts and, further, their effect on the tool lives exhibited by the coated inserts. The latter were determined from a series of turning tests on 817M40 workpiece material, carried out under conditions of builtup- edge (bue) formation, at cutting speeds in the range 37.5 - 60 m min 1. Both process parameters were found to have a marked effect on the characteristics of the TiC coatings and on the tool lives exhibited by the coated inserts. The reasons for this are discussbd. The TiC coated inserts which displayed the most favourable combination of coating characteristics and tool life were used in two further series of turning tests carried out to investigate tool wear, bue size, tool forces, apparent coefficient of friction and workpiece surface finish. Uncoated inserts were also tested. The application of the TiC coating was found to have led to a marked improvement in the cutting properties of the PM HSS inserts. Its role during cutting was studied from metallographic sections through worn inserts and the reasons for its effect on cutting properties are discussed.

General: The thesis concerns the prediction and control of vibrations in planar, kinematically determinate linkage mechanisms operating in a continuous manner, typically driven by a crankshaft. An array of simplified models of linkage components is used to assess the likely significance of the many factors concerned, assuming the components to be of realistic proportions. It is concluded that the effects of joint clearance and (in some cases) driving system flexibility, rather than link flexibility per-se, are likely to be the crucial factors. Attention is therefore focused on the former factors in the chapters that follow. Clearance Effects: The literature on the two-dimensional dynamic effects of clearance("ludodynamic" effects) in revolute joints is critically reviewed, with the conclusion that existing theoretical models need to be simplified to be of use for preliminary design synthesis, and that more discriminating experimental work is needed before any of the theories can be applied with confidence. A new theory is developed with a view to meeting the former need, the results being presented in the form of a design chart. An account is then given of the design, development and use of a novel experimental apparatus for studying a number of relevant aspects of the ludodynamic behaviour of a revolute joint. The new theory is supported in some respects for'larger clearances (250 um on 50mm diameter) but for smaller clearances (65 & 20 pm) the air 'squeeze film' is found to play an increasingly dominant role. Drive Flexibility Effects: The effects of driving system flexibility are approximately governed by an inhomogeneous Hill's equation. A numerical method is used to find the harmonic composition of the steady state solutions of this equation. A rule for predicting resonant and unstable speeds is hypothesized: it is shown to give excellent results, but the response at off-resonant speeds also has a large high-frequency element in some cases. Synthesis: A convenient method for modifying undesirable dynamic performance in a linkage mechanism is the attachment of auxiliary masses or springs. A method is developed for the efficient optimisation of counterweights by a weighted root mean square criterion, subject to bounds on the physical parameters. A known method for synthesis of auxiliary springs by the use of precision points in the objective function is extended, and methods for optimising the spacing of the precision points are introduced.

Worm gearing is very widely used, especially in heavy industry, but due to the complexity of worm gear geometry, worm gear research has lagged behind that for spur and helical gears. In the last decade, however, the potential for significant improvement in worm gearing has dramatically increased: computers have given greater freedom to analyse worm gearing; CNC machines make it possible to aim for optimised worm gear geometries with very high accuracy and the development of synthetic lubricants has substantially improved lubrication conditions. In the UK, over the last few years, research effort in the field of worm gearing has increased considerably. As a part of this recent activity in the UK, the author has been involved mainly in developing the analytical mechanics and metrology of worm gears. A method for the generalised 3D non-elastic worm gear mesh analysis and associated software have been developed and worm wheel metrology software has been implemented on a CNC measuring machine in the UK National Gear Metrology Laboratory, to allow, for the first time, analytical measurement of worm wheel tooth flanks. Combination of the mesh analysis software and CNC measurement of worm wheels has assisted in the design and manufacture of worm gears with modified tooth profiles. Two methods of 3D non-elastic worm gear analysis have been developed for conjugate action and non-conjugate action respectively. The conjugate analysis determines the lines of contact, sliding and rolling velocities, limitations of the working area (the envelope of contact lines on a worm surface and singularities on a wheel surface), principal relative curvatures and the orientations of contact lines. It is based on the B-matrix method [Zhang and Hu, 1989]. The non-conjugate analysis predicts entry and exit gaps, contact ratio, wear marking on the worm flank, instantaneous contact topology on all the engaged tooth flanks, total contact area, contact pattern and transmission error. This is based on numerical simulation of the actual worm gear running process under no-load. Although the non-elastic analysis models have been designed for any type of worm gearing, and have been used to study Cavex (ZC) wormgears and the meshing of a ZA Abstract worm with a helical gear, most of the work has been on involute (ZI) worm gearing, since this is, by far, the most commonly produced type in the UK. This thesis presents the work as follows: 1) The development of the B-Matrix kinematic method for conjugate analysis. The B-Matrix method, presented in chapter 2, elegantly simplifies the derivation and calculation procedures, since the geometric parameters and the motional parameters can be arranged in separate matrices. As a result, the models can be applied to different geometries and coordinate systems with no need for further difficult derivations. The method leads to an easier way of integrating the theory of various types of worm gearing into compact generalised models. It is much more convenient and reliable to let the computer formulate and solve matrix equations numerically, treating each matrix as a simple variable, than to develop analytically the corresponding long tedious non-linear equations. 2) The development of mathematical equations to allow CNC measuring machines to measure cylindrical worm wheels with respect to their mating worms. The measurements are 3-dimensional and absolute, in the sense that the results are the deviations from the theoretical geometries rather than comparative measurements relative to a (necessarily imperfect) master worm wheel. The measurement theory has been implemented on a particular CNC measuring machine. This is presented in chapters 3 and 5. 3) The development of the non-conjugate analysis. The fundamental basis of the non-conjugate analysis presented in this thesis is to rotate the worm wheel to bring its tooth flank into contact with the worm flank at each given angle of worm rotation, so that the no-load transmission error and gap contours can be determined. This method is suitable for both cylindrical and globoidal worm gears, since the rotation angles of worm and wheel are used to simulate the running process directly. Abstract The method also allows the wheel tooth flank to be obtained either by conjugate analysis of the hobbing process, or by analytical measurements or other methods (for example, when a theoretically-generated involute helical gear is used to mesh with a worm). This work is presented in chapter 4. 4) implementation of the non-elastic analysis theory. The non-elastic analysis software has been written for personal computers. In addition, dimensional calculations specified by BS 721 and commonly used hob design methods have been added to the non-elastic analysis software to increase user-friendliness. The software has been used to investigate the effects on the worm gear contact and performance of machining errors and profile deviations or modifications. The structure of this analysis software allows for the inclusion of new modules for other types of worm gearing without in any way disturbing the integrity of the program's existing abilities. The non-elastic analysis software is user-friendly with a "Windows" graphical user interface. Software reliability and error tolerance have been of particular concern during program development. This work is presented in chapter 5. 5) The software has been thoroughly validated against other published results and/or actual production. The software has been used extensively for both research and commercial purposes, and the user interface developed further in response to user feedback. Examples of these applications are given in chapter 7.

No description available.

The work includes summaries of the mechanics of wear in sliding systems under light loading, and severe wear mechanisms under metal cutting conditions. Applications of different wear mechanisms to cutting tool wear, and the problems associated with defining cutting tool life and failure criteria are discussed. Applications of dimensional analysis to the metal cutting problem are presented and include sections on: tool temperature, tool life/cutting speed relationships, tool life/temperature and temperature/time relationships, Colding's three dimensional tool life equation and.an analysis of the Taylor constant. The development of empirical cutting tool life equations is reviewed and includes Taylor type relationships, equations based on the concept of the chip equivalent and Colding's tool life equation. The effectsof cutting conditions, tool geometry, tool material and workpiecematerial on cutting tool life are considered. The fundamentals of sawing are outlined and the variations of modern power hacksaw and bandsaw machines discussed. This section includes a description of modern saw blades and saw blade nomenclature. A comprehensive review of previous work carried out on both the power hacksaw and bandsaw operations shows the present state ofknowledge in this field. The experimental work based on an adaptation of Colding's three dimensional tool life equation forms the first thorough investigation of bandsaw blade wear and its effects on cutting rates and economics. Relationships between the wear rate of the band and relevant parameters such as band speed, machine load and geometry of the workpiece are shown. Wear rate and cutting rate have been expressed in terms of a cutting constant, which defines the penetration of the teeth and its decay with use. A computer based simulation of the bandsaw operation has been developed and used to investigate the influence of relevant engineering parameters on productivity and cutting economics. The data obtained from the simulation model has been used to determine cutting rates and costs of bandsaw operations using constant feed rate and constant thrust load principles. The data is based on tests carried out on workpiece material classified as difficult to cut and trends obtained are believed to be typical of those that would beobtained when cutting the more common materials. For the firsttime, direct comparisons are made between carbon blades and high speed steel bi-metal blades under various bandsaw conditions, and the bandsaw and power hacksaw operations are directly compared. The investigation results in the following conclusions. The bandsaw operation may be a low cost, high cutting rate operation when high speed steel bi-metal blades are used under optimised operating conditions. High speed steel bi-metal blades should be preferredto carbon. A bandsaw machine operating with constant feed rate is superior to one operating with a constant thrust load system. A reduction in the total cost per cut can usually be obtained by optimising feed rates at the expense of blade life. The bandsaw operation can be as economical as the power hacksaw operation whilst achieving a higher cutting rate.