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The adhesive effects between abrasive particle and work on tool wear of the polishing process were considered in the study. Adhesive strength of the interfaces may affect wear rates of tool on the different adhesive way. Several sets of experiments were designed to reveal some phenomena about the wear rates of tool and work. There are variations in the adhesive of the interface causing different degree of tool wear for distinct kind of abrasive particle¡Bwork and tool¡¦s material. The experimental study demonstrated that the wear rate of tool was related to the adhesive strength between abrasive particle and work. Any change of the adhesive strength may significantly alter the wear rate of tool. An analytical study was done to examine the role played by the adhesive strength at the interfaces of abrasive particle on the wear rates of tool and work. It was derived from the law of force equilibrium and the principle of minimum potential energy. Tool wear was affected for polishing process by altering adhesive strength. The computer simulations indicated that an enhancement of adhesion between abrasive particle and work would always increase the wear rate at tool while the wear rate of work could be increased or decreased. To prove analytical study was reasonable by experimental study. Finally,the possible causes of observed phenomena and the limitations of the study were discussed.

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Abstract The tool wear characteristics of the hydrodynamic polishing process under various lubricating conditions are examined in this study. Both the experimental and theoretical studies will be done in this paper. In the experimental study, the relationships between tool wear and its possible influential factors will be examined. In the theoretical study, the mathematical model will be established to interpret the qualitative and quantitative relationships between tool wear characteristics and various operating parameters. For the experimental study, a series of experiments will be done to investigate the effect of various factors on the tool wear and machining rate, under non-contact or semi-contact lubricating condition. The factors may include the tool¡¦s angular speed, the applied load, the tool¡¦s surface irregularities, the slurry viscosity, and the properties of tool, workpiece and abrasive particle (such as surface energy). To establish the mathematical model, the principle of dynamics, law of minimum potential energy and elasto-hydrodynamic lubricating theorem of hydrodynamic polishing process are adopted to derive the removal rate model of a particle under differential contact conditions or under various material parameters (such as surface energies or speed constants) from the energy point of view. In addition, the wear rate of tool is to be analyzed. To deal with the random nature of tool¡¦s surface irregularities, the probability theory is applied to calculate the average wear rate of tool, under semi-contact or non-contact condition or under various material parameters. It is shown that both the tool waviness and radius of tool curvature changed and had specific trends in the wear process. Especially, the wear rate of tool under semi-contact lubricating condition was not necessarily large than that under the non-contact one. The experimental data indicated that the effects of tool wear on machining rate highly depended on the lubricating condition of tool. The trend of machining rate versus accumulated machining time under non-contact lubricating condition was very different from that under the semi-contact one. A mathematical model relating the removal capability of an abrasive particle at the tool¡¦s or workpiece¡¦s surface and various operating parameters are proposed. The qualitative properties of removal capability the under different material parameters and various contact conditions are obtained by the computer simulations. The analysis indicates that the relationships between the removal capability and various material parameters (such as surface energies of adhesion or operating conditions) are not monotonic. Under the contact condition, it is shown that the tool¡¦s surface energy of adhesion and the speed constant has a negative effect on the removal capability at tool¡¦s surface. On the other hand, the surface energy of adhesion on work and the speed constants have a positive effect on the removal capability at tool¡¦s surface. For the workpiece, the converse implications are also true. Three types of patterns for removal capability at tool¡¦s surface due to the degree of embedding of a particle were obtained. There are increase or first increase then decrease or decrease directly, respectively. Under non-contact condition, it is shown that the removal capability has a negative relationship with local film thickness. In addition, a mathematical model relating the tool or work piece wear rate and various operating parameters are also proposed. The qualitative properties of tool wear rate under various lubricating conditions are obtained by the simple statistic analysis. The analysis indicates that the relationships between tool and workpiece wear rate and various parameters are also not monotonic. Under non-contact condition, the tool or workpiece wear rate will first increase then decrease due to the tool periphery speed increase. The magnitude of wear rate will decrease or increase due to the material parameters. Under the semi-contact condition, the up-and-down trend is also occurred in the relationship between tool or workpiece wear rate and the tool periphery speed. Accordingly, the relationships between wear rate and tool periphery speed, in a lubricating range covering the non-contact and semi-contact conditions, will reveal a twin-peak pattern. Generally, the workpiece wear rate under the semi-contact condition is not less than the non-contact one. However, the tool wear rate under the semi-contact condition is not necessarily large than the non-contact one. For a specific condition, under the semi-contact condition, the magnitude of the tool wear rate under different speed will increase or decrease by choosing different tool¡¦s surface adhesive energy and speed constant and the relationship between tool wear rate and tool speed will become complex. The wear rate could increase or decrease significantly. In other word, the tool wear rate under the semi-contact condition may be smaller or large than the non-contact one. Hence, a tool with large surface adhesive energy and speed constant should have a lower tool wear rate or higher work wear rate under certain lubricating regime. Finally, the experimental study tests that the proposed model is closely related with the experimental data. The study showed that the qualitative trends of experimental data are consistent with the analytical predictions. Some of the qualitative relationships between tool wear and machining rate could be properly explained from the elasto-hydrodynamic lubrication theorem and the proposed wear theorem for hydrodynamic polishing process.

An investigation has been completed to determine the feasibility of using vibration measurement to develop an online tool wear monitoring system.Conventionaltransducers and FFT signal analysers have been used as the starting point for data collection and analysis. Additional software has been developed in order to obtain additional and enhanced analysis using statistical data such as percentile analysis and 4th statistical moments. The signal analysers have been interfaced with an IBM compatible PC to allow efficient data collection and analysis. • The measurement of surface finish via the use of centre line average has been selected as the primary indicator of tool wear. An experimental programme has been completed which examines the relationship between vibration measurement and surface finish during turning operations. This has provided sufficient general rules and guidelines to enable the method to be extended to other processes. It also provides information from which commonly occurring faults such as looseness of the tool holder, changes in material properties and swarf presence in the toolholder can be identified. Tests have been completed using cast iron, ENS and EN3 steels. An expert system has been developed. It has been demonstrated that sufficient data can be collected during the setting-up stage or commissioning part of a machining process from which, using the expert system, reliable tool wear monitoring can be achieved for all subsequent tests. In addition to predicting'the surface for all stages of tool life, the system can identify common faults such as looseness of the toolholder, the presence of swarf in the toolholder and changes in material properties. This system has been evaluated in relation to the available data, the present expectation of quality assesment required from the machine operation and relative to available commercial monitors. The system offers significant improvements.

Cutting operations are important and commonly used operations in the field of manufacturing. Automated machining is today commonly used in CNC-machines. One common drawback with automated machining is that the tool condition is challenging to predict which leads to a conservative tool replacement times. This leads to a low utilisation of the tool economical lifetime and an unnecessary high number of tool replacements. Methods for indirect continuous monitoring of the tool wear exist but usually require retrofitting of external sensors that can be both costly and also interrupt the machine operation due to the additional wiring. It is therefore of interest to investigate the possibility to use the, often high resolution, sensors already fitted in a CNC-machine to extract valuable data that can indirectly give an estimation of the tool condition. This thesis work has, with attention to the X-, Y- and Z-position sensors, resulted in development of algorithms that show relations between tool wear and data acquired from these sensors. The algorithms operate in the frequency domain to determine changes in the dynamic response over the time of tool degradation.

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A strategy was proposed to suppress the wear effect of tool in a polishing process. So, machining rate of work pieces in polishing process would keep constant. With this strategy applied to HDP, stable machining rate will bring more advantaged for precision engineering. This study mainly discussed by two parts. First, the planning of the rock-and-roll motion and a wear analysis for tools is talked about. Second is discussing about experiment further. In first part, in order to increase tool¡¦s lifetime, expanding tool wear region by rock-and-roll motion is adopted. Meanwhile, simulate the wear behavior to develop a method of removing tool¡¦s materials in expectant form. In second part, there are two targets to compare with first part, one is the effect of planning of tool¡¦s materials removing and the other is the improvement of suppressive wear effect for polishing tool and stabilizing removal rate of work pieces in rock-and-roll motion. The result of experiments shown that planning of tool¡¦s materials removing is working, the radius of curvature and roughness of tool is nearly stable, and there are some effects in removal rate on work pieces. The result of experiment of rock-and-roll motion verified that the wear theorem for tools and prove improvement of wear is working. So, the goal of suppression of wear effect for polishing tool by expanding tool wear region by rock-and-roll motion is feasible.

The first part of this study involve an evaluation of the performance of TiN and AlZ03 single layer coated cemented carbide tools when threading inclusion modified, 708M40T (En 19T) 817M40T (En 24T) and Jethete steels at high cutting conditions by monitoring tool wear, failure modes, post threading workpiece properties, micro and macro-surface alterations and subsurface microhardness variation of threaded surfaces. Test results show that flank wear was the dominant failure mode, increasing rapidly when machining at the top speed of 225 m min,l due to the high temperature generated which accelerates thermally related wear mechanisms. Tool life, surface finish, hardness variation and component forces during threading were influenced by the geometry of the cutting edge, shape of wear/length of wear along tool nose/cutting edge after threading. Formation of flake-like oxide debris on the worn inserts was found to increase with nickel content in the workpiece material. The Al20) coated carbide inserts with K05 - K20 substrate gave longer tool life, lower cutting forces, better surface finish! damages as well as minimum hardness variation after threading compared with the TiN coated VSX grade with P20-P30 substrates. This can be related to their superior hardness, density, transverse rupture strength as well as the unalloyed WC fine grained substrate (1/lm) in addition to the high hot hardness, excellent chemical stability and low thermal conductivity of the AlZ03 coating at elevated temperatures. A formula for tool rejection was also developed during this study based on the average flank wear (VBb) and growth in thread root (GTR) in order to establish a scientific basis for assessing wear of threading tools. The second part of this study involve single point turning of a nickel base, G263, alloy using rhomboid-shaped PVD coated (TiN/TiCN/TiN, TiAIN and TiZrN) carbide tools at high speed cutting conditions. The worn tool edges revealed adhesion of a compact fin-shaped structure of hardened burrs with saw-tooth edges. The compact structure also formed on the cut surface of the workpiece material. The use of coolant during machining tend to work harden the root of the burr thereby restricting tool entry at the cutting zone leading to the generation of excessive feed force which subjects the tool edge to premature fracture and consequently lower tool life. The serrated/saw-tooth like edges of the burr encourages abrasion wear on the tool flank face and the formation of shallow cavities/lateral cracks where fragments of hardened workpiece material are deposited causing deterioration of the machined surfaces. Tool life was generally influenced by the cutting conditions employed as well as the insert geometry. Increasing cutting conditions (speed, feed and depth of cut) led to chipping of the cutting edge and/or flaking of coating layers as well as notching and fracture of the cutting edge. These failure modes jointly contributed to lowering tool life during machining. The TiN/TiCN/TiN coated KC732 (Tool A) inserts with positive sharp edges gave overall performance at the optimum cutting conditions established under finishing operation. This is followed by the TiN/TiCN/TiN coated KC732 (Tool B), TiAlN coated KC313 (Tool C) and lastly the TiZrN coated KC313 (Tool D) inserts' with razor sharp edges. Under roughing operation, the ranking order of tool performance is the TiZrN coated KC313 (Tool D), TiN/TiCN/TiN coated KC732 (Tool A), TiAlN coated KC313 (Tool C) and lastly the TiN/TiCN/TiN coated KC732 {Tool B). The difference in tool geometry and coating materials contributed to the relative order of tool performance.

Titanium alloys support a wide range of practical applications due to their excellent mechanical properties. These include high strength-to-weight ratio, high mechanical strength at elevated temperatures and remarkable oxidation resistance. Machinability investigations so far have been intentionally focused on Ti-6Al-4V, which is commonly used in the aerospace research and development. However, a new classes of titanium alloys are also being developed for these applications. Ti-5Al-5Mo-5V-3C, also known as Ti5553, is included in this new category of titanium grade alloys. It corresponds to a near beta titanium alloy and generally it is employed on the production of high strength parts. Its high tensile strength combined with low weight (compared to Ti64) makes Ti5553 a suitable choice for landing gear parts and advanced structural components. However, due to the previously mentioned mechanical properties of Ti5553, machining processes can be difficult. During the cutting tests, the cutting zone experiences high cutting temperatures, and combined with a low rate of heat transfer, it generates stress and premature tool failure. By using several distinct experimental approaches, this work presents a comparison between different machining conditions (combinations of tools and coolants) to diagnose wear processes and identify better cutting parameters. The main objective of this research is to establish an understanding of how these parameters affect tribological aspects when machining Ti5553. The results of machining studies demonstrate different wear behaviour for CBN and PCD tools under various cutting environments (different coolant modes). These operating conditions can considerably affect the cutting forces leading to an increased tool life and improved surface integrity by decreasing, the residual stress and roughness, as well as work of hardening the workpiece during machining operations. / Thesis / Master of Applied Science (MASc)