<p>Finite element analysis (FEA) employs a science-based approach in which the complete machining process can be simulated and optimized before resorting to costly and time-consuming experimental trials. In this work, cutting coefficient of AISI 1045 steel will be estimated using finite element modelling using Arbitrary Lagrangian Eulerian formulation (ALE). The estimated values are then experimentally validated. A parametric study is carried out after in order to investigate how some cutting parameters can affect the cutting coefficients. The process parameters to be varied include feed rate, cutting speed, and cutting edge radius.</p> / Master of Applied Science (MASc)

The FP interferometer was found to be feasible for detecting changes in machining forces. The fiber optic sensor was able to detect increases in strain corresponding to force increases detected by a dynamometer. The FP interferometer system must progress in several ways. A better data acquisition and data analysis system must be developed. A robust sensor must be made to withstand the harsh environment of machining. Also a method for eliminating the affects of thermal strain must be created. Finally, the placement of the FP sensor must also be determined. The FP has the potential to effectively monitor machining forces without affecting the rigidity of a turning operation setup. / Master of Science

Este trabalho tem como objetivo analisar as vibrações no processo de torneamento interno utilizando um porta ferramentas com a relação comprimento/diâmetro alta. Ferramentas com alto comprimento em balanço são susceptíveis a ocorrência de vibrações regenerativas durante a usinagem, alterando a estabilidade dinâmica do processo e gerando um acabamento superficial indesejado. Testes realizados para a obtenção de dados foram feitos utilizando equipamentos de medição como microfone e plataforma para medição das forças. A proposta foi de analisar a influência de parâmetros de usinagem como rotação e profundidade de corte na estabilidade dinâmica do processo de torneamento interno da liga de alumínio 6351-T6. Para isso utilizou-se os dados gerados na elaboração de uma carta de estabilidade do processo. Simultaneamente efetuou-se as simulações no software Matlab utilizando um modelo pré-estabelecido e comparando com os resultados experimentais obtidos. Para a análise dos dados coletados pelo microfone utilizou-se uma placa de aquisição de sinais, um microcomputador e um software para análise, o ITA-Toolbox. Baixas velocidades de corte propiciam maiores profundidades de corte limite devido ao efeito de amortecimento. Os resultados mostraram que este fenômeno começa a ser significativo quando a relação entre a frequência de vibração e a frequência de rotação é de aproximadamente 30 e aumenta consideravelmente para uma relação de 60. Os resultados também mostraram que para profundidades de corte abaixo do raio de ponta da ferramenta tem-se cortes instáveis porém de acordo com os modelos existentes na literatura, para um valor suficientemente abaixo da profundidade de corte o processo é sempre estável. / This work aims to analyze the vibrations in the boring process using a tool holder with high overhang. Tools with high overhang are susceptible to the occurrence of regenerative vibrations during machining, altering the dynamic stability of the process and generating an undesired surface finish. Tests performed to obtain data were made using measuring equipment such as microphone and platform for measuring forces. The proposal was to analyze the influence of machining parameters such as cutting speed and depth of cut in the dynamic stability of the aluminium alloy 6351-T6 boring process. For this purpose, the data generated in the process stability chart was used. Simulations were performed in the Matlab software using a previous model and compared with the experimental results. For the analysis of the data collected were used a microphone, a signal acquisition board, a microcomputer and a software for analysis, the ITA-Toolbox .In the end, the results showed that the depth of cut and the cutting speed have great influence on the vibration and on the stability of the boring process. Low cutting speeds provide greater cut depth of cut due to the damping effect. The results showed that this phenomenon begins to be significant when the relation between the frequency of vibration and the frequency of rotation is of approximately 30 and increases considerably to a ratio of 60. The results also showed that for depths of cut below the tool nose radius has unstable cuts but according to the models in the literature, for a value sufficiently below the depth of cut the process is always stable.

The lubricants that are applied during metal cutting acts on the interface between the tool and the nascent surfaces generated by the cutting process. Dispersions of oil in water made using suitable emulsifier(s) are used as metal cutting lubricants. The efficiency of the emulsion in rendering a low friction layer on the freshly cut surface will depend on the composition of the emulsion and on the speed, load and temperature characteristics in the tribological system. A unique tribometer which can perform friction testing on freshly cut surfaces has been designed and built for the experimental investigation. In this experimental facility experiments are conducted by performing cutting operation inside a pool of the lubricant and friction force is measured in-situ. Experiments at different loads and speeds were performed. The surfaces were subsequently subjected to spectroscopic analysis using X-ray Photoelectron spectroscopy and Fourier Transform Infrared Spectroscopy (FTIR). Lubricity of the base oils on nascent and preformed (oxidized) surfaces are compared by performing friction tests on surfaces which are cut and friction tested without exposing them to the environment, and on surfaces which were cut and exposed to the environment. While the freshly cut surfaces were seen to be sensitive to the structure of the base oil, the oxidized surfaces did not differentiate between the oil structures. Amongst the three base oils tested, aromatic oil was found to exhibit the least friction. This is attributed to tendency of the aromatic chains to react with the surface and form a film, due to the formation of radical anion-metal cation complexes. Results from spectroscopic investigations are presented to substantiate these arguments. The thesis then explores the differences in the tribological behavior promoted by an emulsion between, when it acts on a cut surface and is slid just once, and when it acts on a cut surface slid repeatedly. Due to repeated sliding, friction was found to decrease with sliding time (distance), and the transition from a freshly formed surface to a repeatedly slid one was found to follow a smooth transition. The improvement in lubricity is attributed to the formation of carboxylate type structures (C=O) which get generated due to the tribological action under repeated sliding conditions in the presence of water. Under repeated sliding conditions, the friction as a function of emulsifier concentration is found to exhibit a minimum at a value which is much below the critical micellar concentration of the emulsifier (CMC). However, the variation under continuous cutting followed a different pattern, with the friction undergoing a sharp decrease close to the CMC. The effect of speed on the tribological performance was investigated and friction was found to increase dramatically beyond a critical speed which is marked as the onset of starvation. The characteristic time required for a film to develop on a newly created surface, together with the contact pressure conditions dictated by the load and speed dictates starvation. The films formed at speeds corresponding to starvation conditions was found to have a significantly different chemical structure from that corresponding to a speed less than the starvation speed.. The effect of temperature was found to affect the lubricity adversely. At elevated temperature, the nature of the film was found to change to that to starved condition, even at a speed which does not register starvation when operating at a lower temperature. The effect of solubility of the emulsifier on the friction characteristics were explored by using emulsifiers of varying hydrophilic-lypophilic values (HLB). Lower HLB emulsifiers were found to exhibit lesser friction, than those corresponding to high HLB value. The variation in lubricity is examined in the light of the morphology of the micellar structures which evolve using these emulsifiers. The main conclusions of the thesis are: 1 Evaluation of lubricity of metal cutting fluids warrants a testing strategy which tests their lubricity on freshly cut surfaces. 2 The formation of carboxylate structures aids lubricity while using an emulsion; emulsions which can result in the formation of such structures exhibit better lubricity under cutting conditions. 3 Tribofilms which show characteristic peaks related to chemisorbed oxygen is found to exhibit good lubricity under the test conditions. 4 Emulsifiers which form lamellar micellar structures which aid easy shear give better lubricity in cutting than those which yield spherical micelles.

<p>Tantalum, niobium, stainless steels, and nickel are corrosion-resistant metals that have become critical in many industrial sectors. Due to the demanding environments and temperatures in which they operate, few materials can serve as substitutes. The advantages of these materials are offset by the difficulties in their machining. Belonging to a group of metals and alloys often referred to as ‘gummy’, their poor machinability or gumminess is manifest as thick chip formation, large cutting forces, and poor finish on cut surface. Hence, machining costs can be prohibitive, and applications limited. The gumminess has been attributed broadly to their high strain-hardening capacity.</p> <p>To examine why these metals are difficult to machine, we used direct <i>in situ</i> observations of the cutting process with a high-speed imaging system, complemented by force measurements. The observations showed that chip formation occurred by repeated large-amplitude folding of the material – sinuous flow – with vortex-like components and extensive redundant deformation. The folding was particularly severe in Ta and Nb. Although Ta and Nb displayed a higher rate of fold nucleation than the Ni and stainless steel, the flow dynamics underlying chip formation across the metals was the same – sinuous flow nucleated by a plastic (buckling-type) flow instability on the workpiece surface just ahead of the advancing tool. The large strains and energy dissipation associated with sinuous flow is the reason for the poor machinability of these metals. </p> <p>Prior work with Cu and Al has shown that sinuous flow can be disrupted and replaced by an energetically more favorable (segmented) flow mode, characterized by quasi-periodic fracture, when suitable chemical media are applied to the initial workpiece surface – a mechanochemical effect. The segmented flow is beneficial for machining processes since it involves much smaller forces and plastic strains. It has been hypothesized that the chemical media influence the flow through their adsorption onto the workpiece surface, thereby altering the surface energy and/or surface stress, and effecting a local embrittlement (ductile-to-brittle transition). </p> <p>We demonstrate similar media (mechanochemical) effects and segmented flow development in cutting of the corrosion-resistant metals, with significant benefits for their machining. These benefits include > 35 percent reduction in the cutting force/energy, and an order of magnitude improvement in cut surface quality (finish, tears and residual strain). Importantly, the experiments with the corrosion-resistant metals provide strong evidence that it is indeed adsorption – not corrosion, as in case of hydrogen embrittlement – that underpins the mechanochemical effect. The experiments used chemical agents well-known for their strong adsorption to metal surfaces, namely green corrosion inhibitors (e.g., plant extracts, propolis) and other natural organic molecules (e.g., dyes, antibacterial drugs, cow’s milk). Lastly, the suitability and application of the mechanochemical effect at industrial cutting speeds is explored in turning experiments with these corrosion-resistant metals. Collectively, our observations, measurements, and analysis show that the gumminess of metals in cutting is due to sinuous flow; the gumminess can be eliminated by use of chemical media; and adsorption is the key to engendering the mechanochemical effect. Implications of the results for industrial processes ranging from machining to particle comminution, and for sustainable manufacturing are discussed.</p> <br>

Cutting tools in a manufacturing system play a significant role in metal cutting process. Cutting tools arc consumable. Tool wear affects the outcomes of machining processes such as machined· surface quality and it is normally used as an indicating parameter for tool life. It is crucial to calculate and record the wear size of different cutting tools. The tool wear is classified into many different categories according to its existing location and wear patterns. Flank wear and crater wear are the two most common types of tool wear which are used to assess the tool's life. The measurements of flank and crater wear in cutting tools have been extensively studied. There are still many challenges when these research results are applied practically. Manufacturing industry demands· accurate and rapid methods for the tool wear measurement. There are two primary objectives in this research. The first is to develop a new tool wear measurement technology by using the active contour model based image processing method for the flank wear measurement. A MATLAB program is developed to verify the suggested image processing algorithm. Many cutting experiments were conducted with different tools on a CNC machine tool. The experimental results show that the developed technology is feasible and can be used to measure the tool wear area. It needs to be noted that this method. can only extract the wear area. This method is not able to estimate the depth of the crater wear. The second objective is to develop a method for crater wear measurement by use of developed stereo vision system. This system consists of a single camera with necessary lighting devices and fixtures. A MATLAB based software is developed to estimate and represent the volume of tool wear. The proposed algorithm and feasibility of the system for the crater wear (3D tool wear) is discussed. Its effectiveness is verified in this research.

Finite element(FE) method has been used to model cutting process since 1970s. However, it requires special techniques to cope with the difficulties in simulating extremely large strain when compare to static or small deformation problems. With the advancement of FE techniques, researchers can now have a deeper insight of the mechanism of material flow and chip formation of metal cutting process. Even the stagnation effect of the workpiece material in front of the cutting edge radius can be captured by using FE techniques such as Remeshing and Arbitrary Lagrangian Eulerian(ALE) formulation. However most of this models are limited to plane strain assumption which means they are 2-dimensional. Although 3D models are existing in the literatures, most of them employ Remeshing technique which is very computationally intensive and has many critics regarding its accuracy due to its frequent remeshing and mapping process. The rest of the 3D models employ Lagrangian formulation. The 3D models by Lagrangian formulation have the same limitations and drawbacks as in 2D models, as it requires failure criteria and in most of the cases predefined partition surfaces are also required. ALE technique on the other hand resolves all the drawbacks of the other formulations, it not only inherits the advantages of the other techniques but also has its own unique advantages such as it can simulate a longer time span up to couple seconds more economically by fixing the number of elements used. Although it's commonly accepted that ALE formulation is superior to other formulations of techniques in modeling metal cutting process, its usage is only limited to 2D models. Limited 3D ALE metal cutting models is available in the literature. Thus the main objective of this research is to explore the possibility of building a 3D metal cutting model with ALE formulation. The reliability and limitations will also be studied. Furthermore, Couple Eulerian-Lagrangian(CEL) formulation is a recent developed formulation that has a lot of potential in modeling metal cutting process in 3D. It will be compared with ALE models to study its potential and limitations in modeling metal cutting process. A new frictional model will also be proposed, which suggests that the frictional phenomenon in metal cutting is a consolidated effect of both friction between material interface and shear yield of the workpiece material. This idea provide a brand new perspective of viewing the friction phenomenon of metal cutting compared to those existed models. / Thesis / Master of Science (MSc)

The Swedish truck industry is looking for new material solutions to achieve lighter engines with increased strength to meet customer demands and to fulfil the new regulations for more environmentally friendly trucks. This could be achieved by increasing the peak pressure in the cylinders. Consequently, a more efficient combustion is obtained and the exhaust lowered. This, however, exposes the engine to higher loads and material physical properties must therefore be enhanced. One material that could meet these demands is Compacted Graphite Iron (CGI). Its mechanical and physical properties make it ideal as cylinder block material, though there are drawbacks concerning its machinability as compared to other materials that are commonly used for the same purpose. Knowledge about machining of the material and its machinability is consequently inadequate. The main goal of this thesis is to identify and investigate the effect of the major factors and their individual contributions on CGI machining process behaviour. When the relationship between the fundamental features; machinability, material microstructure, and material physical properties, are revealed, the CGI material can be optimized, both regarding the manufacturing process and design requirements. The basic understanding of this is developed mainly through experimental analysis as, e.g., machining experiments and material characterization. The machining model presented in this thesis demonstrates the influence of material and process parameters on CGI machinability. It highlights machinability from both design and production planning perspectives. Another important objective of the thesis is an inverse thermo−mechanical FE model for intermittent machining of CGI. Here, experimental results obtained from a developed simulated milling method are used as input data, both to calibrate and validate the model. With these models, a deeper understanding is obtained regarding the way to achieve a stable process, which is the basis for future optimization procedures. The models can therefore be used as a foundation for the optimization of CGI component manufacturing. / <p>QC 20111121</p> / MERA - OPTIMA CGI / FFI - OPTIMA phase two

Inconel 718 is a high nickel content superalloy possessing high strength at elevated temperatures and resistance to oxidation and corrosion. The non-traditional manufacturing process of wire-electrical discharge machining (EDM) possesses many advantages over traditional machining during the manufacture of Inconel 718 parts. However, certain detrimental effects are also present. The top layer of the machined surface is melted and resolidified to form what is known as the recast layer. This layer demonstrates microstructural differences from the bulk workpiece, resulting in altered material properties. An experimental investigation was conducted to determine the main machining parameters which contribute to recast layer formation in wire-EDM of Inconel 718. It was found that average recast layer thickness increased with energy per spark, peak discharge current, current pulse duration, and open-voltage time and decreased with sparking frequency and table feed rate. Over the range of parameters tested, the recast layer was observed to be between 5 and 10 μm in average thickness, although highly variable in nature. Surface roughness of the cut parts showed an increase with energy per spark. Electron Probe Microanalysis (EPMA) revealed the recast layer to be alloyed with elements from the wire electrode. X-ray diffraction testing showed the residual tensile stresses evident near the cut surface to decrease with energy per spark. Additionally, nano-indentation hardness testing indicated that the recast layer is reduced in hardness and elastic modulus compared to the bulk material. Vibratory tumbling was found to be a moderately effective post-processing tool for recast layer removal when using pre-formed ceramic abrasive media or fine grained aluminum oxide.

A preparação das arestas de corte é um processo que tem chamado a atenção na indústria de fabricação e recondicionamento de ferramentas em função dos benefícios que tem trazido especialmente na vida útil da ferramenta. Este processo dá um grande diferencial competitivo àqueles que detém o conhecimento de como aplicá-lo e por isso é mantido como um segredo industrial. No que se refere a brocas helicoidais a escassez de informações é ainda maior, em função da alta complexidade da ferramenta e do processo. O presente trabalho traz os resultados da influência da preparação das arestas de corte (alteração da microgeometria) de brocas helicoidais no processo de furação do aço SAE 4144M temperado e revenido com 38 HRC. O processo manual de escovamento foi utilizado para preparar as ferramentas com arestas arredondadas e o processo manual de limagem para as ferramentas com arestas chanfradas. Foram medidas várias características das peças usinadas tais como: diâmetro, circularidade, desvio de posição, rugosidade dos furos obtidos, dureza, microdureza dos corpos-de-prova, força de avanço e torque do processo de furação, avaliação do tipo e forma dos cavacos gerados no processo. Os resultados mostraram que o processo de preparação de arestas aumenta a resistência da ferramenta ao desgaste e consequentemente aumenta sensivelmente sua vida, especialmente as de arestas arredondadas. Além disso, exerce influência na integridade superficial do furo obtido (circularidade e rugosidade) e na microdureza da região próxima à parede do furo obtido. Não houve diferença significativa no torque entre as geometrias analisadas, porém a força de avanço foi menor para a ferramenta apenas afiada sem preparação de aresta. / The cutting edge preparation is a process which has drawn attention from the tool’s manufacturing and refurbishing industry due to specialization to its benefits specially to tool useful life. This process results in a major competitive advantage to those who have the knowledge of its application and, for this reason, it is kept as a trade secret. As far as the twist drills are concerned, the scarcity of information is even greater, due to the high complexity of the tool and process itself. This dissertation presents the results of the influence of the preparation of the twist drills cutting edges microgeometry alteration in steel drilling process SAE 4144M quenched and tempered steel with 38 HRC. The manual brushing process was used to prepare tools with rounded edges and manual filing process was used to prepare tools with chamfered edges. Several features from the machined parts were measured, such as diameter, roundness, position deviation, roughness of the obtained holes, hardness and microhardness of specimens, feed force and torque of the drilling process, assessment of type and shape of the chips from the process. The results showed that the edges preparation process increases the wear resistance of the tool and thereby increases its useful life significantly, especially for tools with rounded edges. In addition, it influences the surface integrity of the obtained hole (circularity and roughness) and the hardness of the region near the wall of the obtained hole. There was no significant difference in torque between the analyzed geometries, however the thrust force was lower for the sharpened tool without any edge preparation.