Dissertations / Theses on the topic 'Weak force'
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1
Colleoni, Marta. "Gravitational self-force and the weak cosmic censorship." Thesis, University of Southampton, 2016. https://eprints.soton.ac.uk/401825/.
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Hyde, G. "Ab initio studies of weak force mediated molecular enantioselectivity." Thesis, University of Cambridge, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.604912.
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This thesis project investigates two of the mechanisms that have been postulated to explain the origin of the molecular homochirality found in living systems. These mechanisms are i. the Yamagata-Rein Hypothesis, which predicts that the weak neutral currents between electrons and nucleons result in a Parity-Violating Energy Difference (PVED) between a pair of molecular enantiomers; and ii. the Vester-Ulbricht Hypothesis, which predicts that the β-particles produced during weak force mediated nuclear β-decay interact differently with each of a pair of molecular enantiomers. Both hypotheses predict a small enantiomeric excess and theorise that such an excess might have been the prebiotic chiral influence that led to homochirality, which is generally accepted to be a prerequisite for biology. It is found that those PVED computations carried out the coupled-perturbed level of theory are approximately one order of magnitude larger than those previously computed at the entry-level uncoupled-perturbed level of theory. The results computed as part of this thesis project include the first to apply Density-Functional theory to the computation of the PVED. The coupled-perturbed Hartree-Fock and Kohn-Sham computations of the PVED are found to be in good agreement with recent related computational studies. The hypersensitivity of the PVED to small conformational changes, coupled to the difficulties in knowing the aqueous phase structure of even small chiral biomolecules such as α-alanine, means that it is difficult to make any unambiguous conclusions regarding which of a pair of biomolecular enantiomers might have been favoured by the PVED in a probiotic regime. These results do indicate that the largest β-asymmetries are generated in the forward scattering regimes and that the sign of the asymmetries may change suddenly as the energy of the incoming β-particle increases so as to allow the removal of electrons from successive molecular orbitals during the impact ionisation of the molecule.
3
Hammond, Giles Dominic. "Development of a spherical superconducting torsion balance for weak force physics." Thesis, University of Birmingham, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.393048.
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Cerniway, Matthew Allen. "Elliptical Diamond Milling: Kinematics, Force and Tool Wear." NCSU, 2002. http://www.lib.ncsu.edu/theses/available/etd-20020104-082326.
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Machining with diamond tools, whether turning or milling has proven itself as themanufacturing process that produces the highest quality surface finish, with the leastamount of form error in the minimum amount of time. However, due to tool wear and theamount of force generated during conventional machining, diamond tools cannot be usedon carbon containing materials such as steel and brittle materials such as silicates. In anattempt to by-pass the material limitations of diamond machining, a new machiningprocess called vibration assisted machining (VAM) has been developed. VAM involvesoscillating the diamond tool, bringing it into and out of contact with the material in rapidsuccession. VAM can either be 1-dimentional (1D), oscillation in a single direction, or 2-dimensional (2D), a summation of two independent tools motions. Currently, researchefforts are focused on 2D vibration machining, 2D tool motion haven been shown to besuperior to 1D tool motion. Over the past 10 years, 2D VAM with diamond tools hasbeen demonstrated to reduce the amount of machining force and increase tool life whenmachining carbon-containing materials over that of conventional machining processes.However the mechanisms of this improvement have yet to be discovered. This researcheffort is focus on: 1) discovering the fundamental mechanical principals behind theimprovement, force reduction and tool wear, 2) developing a model that predicts thecutting forces and tool contact times, 3) establishes guidelines for the use of vibrationassisted machining and 4) developing an industrial grade 2D VAM servo. The reductionsin tool wear and machining forces are related to the path geometry of the diamond tooland the speed and the depth at which it engages the workpiece. A model has beendeveloped and experimentally verified for 2D VAM which predicts the machining forcesand workpiece / tool contact time if the material properties are known. Along with themodel, a set of charts has been developed for both 1D and 2D VAM that relate the keymachining variables to one another. Lastly, a robust 2D VAM diamond tool servo hasbeen designed.
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Samad-Suhaeb, Mujahid. "Aerodynamics of battle damaged finite aspect ratio wings." Thesis, Loughborough University, 2005. https://dspace.lboro.ac.uk/2134/10736.
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When an aircraft is aerodynamically or structurally damaged in battle, it may not able to complete the mission and the damage may cause its loss. The subject of aircraft battle survivability is one of critical concern to many disciplines, whether military or civil. This thesis considered and focused on Computational Fluid Dynamics [CFD] predictions and experimental investigations into the effects of simulated battle damage on the low-speed aerodynamics of a fmite aspect ratio wing. Results showed that in two-dimensional [2d] and three-dimensional [3D] CFD simulations, Fluent's® models work reasonably well in predicting jets flow structures, pressure distributions, and pressure-coefficient Cp's contours but not for aerodynamic coefficients. The consequences were therefore that CFD prediction was poor on aerodynamic-coefficients increments. The prediction of Cp's achieved good agreement upstream and near the damage hole, but showed poor agreement at downstream of the hole. For the flow structure visualisation, at both weak and strong jet incidences, the solver always predicted pressure-distribution-coefficient lower at upstream and higher at downstream. The results showed relatively good agreement for the case of transitional and strong jet incidences but slightly poor for weak jet incidences. From the experimental results of Finite Wing, the increments for Aspect-ratio, AR6, AR8 and ARIO showed that as damage moves out towards the tip, aerodynamic-coefficients increments i.e. lift-loss and drag-rise decreased, and pitching-moment-coefficient increment indicated a more positive value at all incidence ranges and at all aspect ratios. Increasing the incidence resulted in greater magnitudes of lift-loss and drag-rise for all damage locations and aspect ratios. At the weak jet incidence 4° for AR8 and in all of the three damage locations, the main characteristics of the weak-jet were illustrated clearly. The increments were relatively small. Whilst at 8°, the flow structure was characterised as transitional to stronger-jet. In Finite Wing tests and for all damage locations, there was always a flow structure asymmetry. This was believed to be due to gravity, surface imperfection, and or genuine feature. An 'early strong jet' that indicated in Finite Wing-AR8 at 'transitional' incidence of 8°, also indicated in twodimensional results but at the weak-jet incidence of 4°. For the application of 2d data to AR6, AR8, and ARIO, an assessment of 2d force results led to the analysis that the tests in the AAE's Low Turbulence Tunnel for 2d were under-predicting the damage effects at low incidence, and over-predicting at high incidences. This suggested therefore that Irwin's 2d results could not be used immediately to predict three-dimensional.
6
Knünz, Sebastian. "A trapped-ion phonon laser and the detection of ultra-weak forces." Diss., lmu, 2011. http://nbn-resolving.de/urn:nbn:de:bvb:19-127157.
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Collop, Andrew Charles. "Effects of traffic and temperature on flexible pavement wear." Thesis, University of Cambridge, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.336400.
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Latifzada, Mushtaq Ahmad. "Estimation of flank wear growth on coated inserts." Thesis, Uppsala universitet, Institutionen för fysik och astronomi, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-210994.
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The present work was conducted in Sandvik Coromant to enhance the knowledge and understanding of general flank wear growth and specifically in this case flank wear growth on the cutting edge of the coated (Ti(C, N)/ Al2O3/ TiN) tool inserts. Reliable modeling of tool life is always a concern for machining processes. Numbers of wear models studies predicting the tool life length have been created throughout the metal-cutting history to better predict and thereby control the tool life span, which is a major portion of the total cost of machining. A geometrical contact model defining the geometry of the flank wear growth on the cutting tool inserts was proposed and then compared with four suggested models, which estimates flank wear. The focus of this work is on the initial growth of flank wear process and thereby short cutting-time intervals are measured. Wear tests on cutting tool inserts were performed after orthogonal turning of Ovako 825 B steel and were analysed by optical instrument, 3D optical imaging in Alicona InfiniteFocus and EDS in SEM. Force measurements for cutting speeds, Vc, 150, 200, and 250 m/min and feed rate, fn, 0.15 mm/rev were recorded as well. Results show that initial flank wear land, VB, growth is dominated by sliding distance per cutting length for different cutting speeds. A good correlation between the geometrical contact model and estimation models is indentified. The cutting force measurements compared with the flank wear land show proportionality between two parameters. For the machining data in the present study the flank wear rate per sliding distance, dW/dL, is estimated to 2x103 (μ3/m).
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Bao, Wei-yu. "Tool cutting force modeling and wear estimation of micro-end-milling operations." FIU Digital Commons, 1999. http://digitalcommons.fiu.edu/etd/1386.
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The applications of micro-end-milling operations have increased recently. A Micro-End-Milling Operation Guide and Research Tool (MOGART) package has been developed for the study and monitoring of micro-end-milling operations. It includes an analytical cutting force model, neural network based data mapping and forecasting processes, and genetic algorithms based optimization routines. MOGART uses neural networks to estimate tool machinability and forecast tool wear from the experimental cutting force data, and genetic algorithms with the analytical model to monitor tool wear, breakage, run-out, cutting conditions from the cutting force profiles.
The performance of MOGART has been tested on the experimental data of over 800 experimental cases and very good agreement has been observed between the theoretical and experimental results. The MOGART package has been applied to the micro-end-milling operation study of Engineering Prototype Center of Radio Technology Division of Motorola Inc.
10
Waldura, Markus. "Monomotivik, Sequenz und Sonatenform im Werk Robert Schumanns /." Saarbrücken : Saarbrücker Druckerei und Verlag, 1990. http://catalogue.bnf.fr/ark:/12148/cb35419828q.
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Vyas, Mukesh Kumar. "Nanoscale Investigation of Adhesion, Friction, and Wear in Chemically Heterogeneous Responsive Polymer Brushes." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2008. http://nbn-resolving.de/urn:nbn:de:bsz:14-ds-1226414812035-21826.
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Polymer brushes provide the responsive smart surfaces which can be used for fabrication of various devices. In this thesis work, adhesion, friction, and wear of polystyrene (PS) - poly(2-vinyl pyridine) (P2VP) and polystyrene - poly(acrylic acid) (PAA) binary brushes and corresponding monobrushes were investigated in dried state under controlled environment. Spin-coated films were also investigated for comparison. The aim was to explore possibilities to control/tune adhesion, friction, and wear between inorganic or polymeric surfaces by use of polymer brushes. Atomic force microscopy (AFM) with sharp silicon nitride tip and colloidal probes was employed to investigate the nanoscale adhesion and friction forces between different inorganic and polymeric surfaces. Adhesion and friction on the polymer brushes were comparable to that on the spin-coated films. Adhesion and friction force values were correlated, and were in accordance with the wettability of the brush surfaces for most of the samples. Switching in the adhesion and friction forces was observed for the PS+P2VP and PS+PAA binary brushes on treatment with selective solvents. Maximum switching in adhesion force and friction coefficient was by a factor of 2.7 and 5.4, respectively. Furthermore, switching of friction for mixed brush surface was observed during macroscale friction measurements using nanoindenter. Friction coefficients at macroscale were higher than those at the nanoscale. Moreover, adhesion and friction forces between the surfaces were significantly influenced by the humidity, grafting density of polymer brushes, chemical composition of top of the binary brush surface, and tip scan velocity. Nanowear studies were carried out with AFM using sharp silicon nitride tip while macrowear studies were carried out using nanoindenter. Nanowear on the surfaces was affected by molecular entanglements, adhesion and friction forces as well as shape and status of the tip. It was observed that the typical wear mode for PS brushes (treated with toluene) was ripple formation. In case of P2VP brushes (treated with ethanol) and PAA brushes (treated with pH 10 water), wear occurred via removal of the polymeric material. Wear mechanism observed for the monobrushes was similar to that observed for the spin-coated thick films of the same polymeric material. However, extent of the wear on the brush surfaces significantly differed from that on the spin-coated films. In case of PS+P2VP and PS+PAA binary brush samples, change in the wear mode was observed on treatment with the different selective solvents. On treatment with toluene (PS on the top), both of these binary brushes showed the wear by formation of the ripples. On the other hand, when these binary brushes were treated with selective solvent for P2VP or PAA, wear occurred mainly via removal of the polymeric material. The amount of wear increased with the number of scans for all the polymer brush samples. Moreover, wear on the polymer brush surfaces was also increased on increase in the applied load and decrease in the scan speed. Wear behavior on macroscale was averaged due to contact between surfaces at large number of asperities. Our results show that adhesion, friction, and wear of polymer surfaces can be controlled/tuned by the use of binary polymer brushes.
12
Haff, G. Gregory, Janna R. Jackson, Naoki Kawamori, Jon M. Carlock, Michael J. Hartman, J. Lon Kilgore, Robert T. Morris, Michael W. Ramsey, William A. Sands, and Michael H. Stone. "Force-Time Curve Characteristics and Hormonal Alterations During an Eleven-Week Training Period in Elite Women Weightlifters." Digital Commons @ East Tennessee State University, 2008. https://dc.etsu.edu/etsu-works/4139.
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The purpose of this investigation was to study the effects of an 11-week training period performed by female weightlifters. Two weeks before this investigation, baseline measures for total testosterone, cortisol, and testosterone:cortisol ratio were collected. The 11-week training program consisted of the core exercises (i.e., clean, clean and jerk, and snatch) and other supplemental exercises (i.e., clean pull, snatch pull, squat, and front squat). Hormonal, isometric, and dynamic middle thigh pull force-time curve characteristics were assessed biweekly throughout the duration of the investigation, whereas volume load and training intensity were assessed weekly throughout the investigation. The testosterone:cortisol ratio of the baseline (1.19 ± 0.64) was significantly different from the ratio of weeks 1 (0.67 ± 0.36) and 9 (0.94 ± 0.66). When the week-to-week values were compared, week 1 (0.67 ± 0.36) was significantly different (P < 0.05; ηsup>2= 0.84) from week 3 (1.06 ± 0.54). A very strong correlation (r = −0.83; r 2 = 0.69) was found between the percentage change of the testosterone:cortisol ratio and volume load from weeks 1 to 11. Moderate to very strong correlations were noted between the percentage change in volume load and isometric peak force, peak force during the 30% isometric peak force trial, and peak force during the 100-kg trial during the 11 weeks of training. The primary finding of this study was that alterations in training volume load can result in concomitant changes in the anabolic-to-catabolic balance, as indicated by the testosterone:cortisol ratio, and the ability to generate maximal forces.
13
社本, 英二, Eiji SHAMOTO, 励. 樋野, Rei HINO, 雅之 梅崎, Masayuki UMESAKI, 俊道 森脇, and Toshimichi MORIWAKI. "切削力モデルに基づくエンドミル加工状態の知的認識 (データベースを必要としない手法の開発)." 日本機械学会, 2003. http://hdl.handle.net/2237/9006.
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Myint, Tun. "Strength of 'weak' forces in multilayer environmental governance cases from the Mekong and Rhine River basins /." [Bloomington, Ind.] : Indiana University, 2005. http://wwwlib.umi.com/dissertations/fullcit/3167279.
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Thesis (Ph.D.)--Indiana University, School of Public and Environmental Affairs and School of Law, 2005.Title from PDF t.p. (viewed Dec. 3, 2008). Source: Dissertation Abstracts International, Volume: 66-03, Section: A, page: 1153. Co-Chairs: Elinor Ostrom; Patrick O'Meara.
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Shatla, Mahmoud Nagui. "Prediction of forces, stressses, temperatures and tool wear in metal cutting." The Ohio State University, 1999. http://rave.ohiolink.edu/etdc/view?acc_num=osu1251224746.
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Shatla, Mahmoud Nagui. "Prediction of forces, stresses, temperatures and tool wear in metal cutting /." The Ohio State University, 2000. http://rave.ohiolink.edu/etdc/view?acc_num=osu148819211926358.
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Rizzo, Frank. "Does a Tailored Nine-week Training Intervention Improve Jump Height, Single-leg Stability, and Whole-body Stability Performance in Young Cross-country Skiers?" Thesis, Umeå universitet, Avdelningen för idrottsmedicin, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-181172.
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The purpose of this study was to investigate if a nine-week training intervention composed of different mobility and stability exercises intending to improve jump height, whole-body stability, and single-leg stability of junior cross-country skiers. It was also of interest to see if the test equipment could determine the study participants' potential risk of injury with a built-in injury predictor measurement, Musculoskeletal Health (MSK). A total of 16 cross-country skiers aged 16-20 years, 8 man and 8 women, performed the following tests on a force plate; Jump Scan (i.e., to characterize an individual's dynamic movement strategy), Plank Scan (i.e., to measure the individual's ability to control global static stability across each extremity), and Balance Scan (i.e., the individual's ability to maintain their center of mass over their center of pressure). After the initial scan, participants were assigned to the same nine-week intervention program, with Group 1 performing the program three times each week and Group 2 once each week before performing a post-intervention scan. Using two-way ANOVA showed no significant between-group differences. There was no significant difference when using three-way ANOVA within both intervention groups, except higher CMJ Load scores (p=0.032) and reduction in Plank scores, Plank Left (p=0.024) in male participants. When using logistic regression tests to determine the correlation between jump height (CMJ) outcomes effect on MSK injury risk between groups and within gender, a significant correlation in females was shown (p=0.0280, R=0.46). The present study's results suggest that a 9-week training intervention is not sufficient when training either one or three times per week for improving jump height, whole-body stability, and single-leg stability in junior cross-country skiers.
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Rice, Reginald H. "Atomic force microscopy studies of thermal, mechanical and velocity dependent wear of thin polymer films." Thesis, Kansas State University, 2012. http://hdl.handle.net/2097/14955.
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Master of ScienceDepartment of Physics
Robert Szoszkiewicz
Nanoscale modifications of polymer surfaces by scratching them with sharp tips with curvature radii of tens of nanometers and at variable temperatures are expected to provide wealth of information characterizing wear response of these polymers. Such studies are important in the light of understanding the nanoscale behavior of matter for future applications in advanced polymer coatings. This thesis describes how Atomic Force Microscopy (AFM) and hot-tip AFM (HT-AFM) methods were used to characterize thermal and mechanical properties of a 30 nm thick film of poly(styrene-block-ethylene oxide), PS-b-PEO, and modify its lamellar surface patterns. Additionally, it is revealed how contact AFM and HT-AFM methods can efficiently characterize the wear response of two popular polymer surfaces, poly(methyl methacrylate), PMMA, and polystyrene, PS. The AFM and HT-AFM studies on PS-b-PEO copolymer were aimed at producing spatial alignment of respective PS and PEO parts. Instead, however, surface ripples were obtained. These measurements are explained using mode I crack propagation model and stick-and-slip behavior of an AFM tip. In addition, HT-AFM studies allowed extraction of several thermo-physical properties of a PS-b-PEO film at local volumes containing about 30 attograms of a polymer. These thermo-physical quantities are: PEO melting enthalpy of, 111 ± 88 J g[superscript]-1, PS-b-PEO local specific heat of 3.6 ± 2.7 J g[superscript]-1K[superscript]-1, and molecular free energy of Helmholtz of 10[superscript]-20 J nm[superscript]-2 for the PEO within PS-b-PEO. Utilizing a spiral scan pattern at constant angular speed and at various temperatures at the AFM tip-polymer interfaces, the wear response of PS and PMMA polymers was characterized. Cross-sections along the obtained spiral wear patterns provided plots of polymer corrugation as a function of scanning speed. From these studies it was found that the corrugation of the modified polymer surface decays exponentially with linear velocity of the scanning tip.
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Long, Yu. "Modeling of the effect of tool wear on cutting forces in turning." Connect to this title online, 2008. http://etd.lib.clemson.edu/documents/1211387406/.
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Saunders, Nathan William. "Efficacy of a 6-week Neuromuscular Training Program for Improving Postural Control in Figure Skaters." The Ohio State University, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=osu1305044478.
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Song, Wenge. "Development of predictive force models for classical orthogonal and oblique cutting and turning operations incorporating tool flank wear effects." Thesis, Queensland University of Technology, 2006. https://eprints.qut.edu.au/16239/1/Wenge_Song_Thesis.pdf.
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Classical orthogonal and oblique cutting are the fundamental material removal or machining processes to which other practical machining processes can be related in the study and modelling of the machining processes. In the last century, a large amount of research and development work has been done to study and understand the various machining processes with a view to improving the processes for further economic (cost and productivity) gains. However, many aspects of the cutting processes and cutting performance remains to be fully understood in order to increase the cutting capability and optimize the cutting processes; in particular, there is little study to understand the effects of the inevitable tool wear on the machining processes. This thesis includes an extensive literature review on the mechanics of cutting analysis. Considerable work has been carried out in past decades on the fundamental analysis of 'sharp' tool cutting. Although some work has been reported on the effects of tool flank wear on the cutting performance, there is a general lack of the fundamental study of the effects of the flank wear on the basic cutting or chip formation process. It has been well documented that tool flank wear results in an increase in the cutting forces. However, it was not known if this force increase is a result of the change in the chip formation process, and/or the rubbing or ploughing forces between the tool flank and the workpiece. In work carried out since the early 1980s, the effects of the so-called edge forces have been considered when the tool is not absolutely sharp. Little has been reported to further develop fundamental cutting theories to understand applications to more relevant the practical situation, i.e. to consider the tool wear effects. Based on the findings of the literature review, an experimental investigation is presented in the first part of the thesis to study the effects of tool flank wear on the basic cutting or chip formation process by examining the basic cutting variables and performance in the orthogonal cutting process with tool flank wear. The effects of tool flank wear on the basic cutting variables are discussed by a comprehensive analysis of the experimental data. It has been found that tool flank wear does not affect the basic cutting variables (i.e. shear angle, friction angle and shear stress). It is therefore deduced that the flank wear does not affect the basic chip formation process in the shear zone and in the tool-chip interface. The study also finds that tool flank wear causes an increase in the total cutting forces, as can be expected and such an increase is entirely a result of the rubbing or ploughing forces on the tool wearland. The significance of this finding is that the well-developed machining theories for 'sharp' tools can be used in modelling the machining processes when tool flank wear is present, rather than study the machining process and develop machining theories from scratch. The ploughing forces can be modelled for incorporation into the overall cutting force prediction. The experimental study also allows for the forces on the wearland (or wearland force) and edge forces to be separated from the total measured forces. The wearland force and edge force models are developed in empirical form for force prediction purpose. In addition, a database for the basic cutting variables or quantities is established for use in modelling the cutting forces. The orthogonal cutting force model allowing for the effects of flank wear is developed and verified by the experimental data. A comprehensive analysis of the mechanics of cutting in the oblique cutting process is then carried out. Based on this analysis, predictive cutting force models for oblique cutting allowing for the effects of flank wear are proposed. The wearland force and edge force are re-considered by analysing the oblique cutting process and the geometrical relation. The predictive force models are qualitatively and quantitatively assessed by oblique cutting tests. It shows that the model predictions are in excellent agreement with the experimental data. The modelling approach is then used to develop the cutting force models for a more general machining process, turning operation. By using the concept of an equivalent cutting edge, the tool nose radius is allowed for under both orthogonal and oblique cutting conditions. The wearland forces and edge forces are taken into consideration by the integration of elemental forces on the tool flank and the cutting edge, respectively. The cutting forces in turning operations are successfully predicted by using the basic cutting quantity database established in the orthogonal cutting analysis. The models are verified by turning operation tests. It shows that the model predictions are in excellent agreement with the experimental results both qualitatively and quantitatively. The major findings, research impacts and practical implications of the research are finally highlighted in the conclusion. The modelling approach considering the flank wear effects in the classical orthogonal and oblique cutting and turning operations can be readily extended to other machining operations, such as drilling and milling.
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Song, Wenge. "Development of predictive force models for classical orthogonal and oblique cutting and turning operations incorporating tool flank wear effects." Queensland University of Technology, 2006. http://eprints.qut.edu.au/16239/.
Full textAbstract:
Classical orthogonal and oblique cutting are the fundamental material removal or machining processes to which other practical machining processes can be related in the study and modelling of the machining processes. In the last century, a large amount of research and development work has been done to study and understand the various machining processes with a view to improving the processes for further economic (cost and productivity) gains. However, many aspects of the cutting processes and cutting performance remains to be fully understood in order to increase the cutting capability and optimize the cutting processes; in particular, there is little study to understand the effects of the inevitable tool wear on the machining processes. This thesis includes an extensive literature review on the mechanics of cutting analysis. Considerable work has been carried out in past decades on the fundamental analysis of 'sharp' tool cutting. Although some work has been reported on the effects of tool flank wear on the cutting performance, there is a general lack of the fundamental study of the effects of the flank wear on the basic cutting or chip formation process. It has been well documented that tool flank wear results in an increase in the cutting forces. However, it was not known if this force increase is a result of the change in the chip formation process, and/or the rubbing or ploughing forces between the tool flank and the workpiece. In work carried out since the early 1980s, the effects of the so-called edge forces have been considered when the tool is not absolutely sharp. Little has been reported to further develop fundamental cutting theories to understand applications to more relevant the practical situation, i.e. to consider the tool wear effects. Based on the findings of the literature review, an experimental investigation is presented in the first part of the thesis to study the effects of tool flank wear on the basic cutting or chip formation process by examining the basic cutting variables and performance in the orthogonal cutting process with tool flank wear. The effects of tool flank wear on the basic cutting variables are discussed by a comprehensive analysis of the experimental data. It has been found that tool flank wear does not affect the basic cutting variables (i.e. shear angle, friction angle and shear stress). It is therefore deduced that the flank wear does not affect the basic chip formation process in the shear zone and in the tool-chip interface. The study also finds that tool flank wear causes an increase in the total cutting forces, as can be expected and such an increase is entirely a result of the rubbing or ploughing forces on the tool wearland. The significance of this finding is that the well-developed machining theories for 'sharp' tools can be used in modelling the machining processes when tool flank wear is present, rather than study the machining process and develop machining theories from scratch. The ploughing forces can be modelled for incorporation into the overall cutting force prediction. The experimental study also allows for the forces on the wearland (or wearland force) and edge forces to be separated from the total measured forces. The wearland force and edge force models are developed in empirical form for force prediction purpose. In addition, a database for the basic cutting variables or quantities is established for use in modelling the cutting forces. The orthogonal cutting force model allowing for the effects of flank wear is developed and verified by the experimental data. A comprehensive analysis of the mechanics of cutting in the oblique cutting process is then carried out. Based on this analysis, predictive cutting force models for oblique cutting allowing for the effects of flank wear are proposed. The wearland force and edge force are re-considered by analysing the oblique cutting process and the geometrical relation. The predictive force models are qualitatively and quantitatively assessed by oblique cutting tests. It shows that the model predictions are in excellent agreement with the experimental data. The modelling approach is then used to develop the cutting force models for a more general machining process, turning operation. By using the concept of an equivalent cutting edge, the tool nose radius is allowed for under both orthogonal and oblique cutting conditions. The wearland forces and edge forces are taken into consideration by the integration of elemental forces on the tool flank and the cutting edge, respectively. The cutting forces in turning operations are successfully predicted by using the basic cutting quantity database established in the orthogonal cutting analysis. The models are verified by turning operation tests. It shows that the model predictions are in excellent agreement with the experimental results both qualitatively and quantitatively. The major findings, research impacts and practical implications of the research are finally highlighted in the conclusion. The modelling approach considering the flank wear effects in the classical orthogonal and oblique cutting and turning operations can be readily extended to other machining operations, such as drilling and milling.
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Niu, Zhichao. "Investigation on the multiscale multiphysics based approach to modelling and analysis of precision machining of metal matrix composites (MMCs) and its application perspectives." Thesis, Brunel University, 2018. http://bura.brunel.ac.uk/handle/2438/17549.
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Over the last two decades or so, metal matrix composites (MMCs) have been drawing the attention of the industry due to their potentials in fulfilling demands for high performance industrial materials, products and advanced engineering applications. On the other hand, the high precision machining is becoming one of the most effective methods for enabling these difficult-to-machine composites to be applied particularly in precision engineering. Therefore, in-depth scientific understanding of MMC precision machining is essential and much needed so as to fulfil the gap between fundamental issues in precision machining of MMCs and their industrial scale applications. This thesis focuses on development of a multiscale multiphysics based approach to investigating the machinability of particulate MMCs and the machining process optimisation. In order to investigate the surface generation in relation to the process variables, this PhD study covers the key fundamental issues including chip formation process, dynamic cutting force, cutting temperature partition and tool wear by means of combining modelling, simulation and experimental study. The chip formation mechanisms and the minimum chip thickness in precision machining of SiCp/Al and B4Cp/Al MMCs by using PCD tools are investigated through a holistic approach. Minimum chip thickness (MCT) value is firstly identified based on the modified mathematical model. The certain threshold of the uncut chip thickness, i.e. chips starting to form at this chip thickness point, is then established. The chip formation process including the matrix material breakage, particles fracture, debonding, sliding or removal and their interfacial interactions are further simulated using finite element analysis (FEA). The minimum chip thickness and chip formation simulations are evaluated and validated via well-designed experimental trials on a diamond turning machine. The chips and surface profiles formed under varied process variables in periodic material removals are inspected and measured in order to obtain a better understanding on MMC chip formation mechanisms. The improved dynamic cutting force model is developed based on the micro cutting mechanics involving the size effect, undeformed chip thickness effects and the influence of cutting parameters in the micro scale. Cutting process variables, particle form, size and volume fraction at different scales are taken into account in the modelling. The cutting force multiscale modelling is proposed to have a better understanding on the MMCs cutting mechanics and to predict the cutting force accurately. The cutting forces are modelled and analysed in three cutting regimes: elastic recovery zone, ploughing zone and shearing zone. A novel instantaneous chip thickness algorithm including real chip thickness and real tool trajectory is developed by taking account of the tool runout. Well-designed cutting trials are carried out under varied process variables to evaluate and validate the force model. In order to obtain the actual cutting forces accurately, transfer function technique is employed to compensate the measured cutting forces. The cutting force model is further applied to correlate the cutting tool wear and the prediction of the machined surface generation. Multiphysics coupled thermal-mechanical-tribological model and FE analysis are developed to investigate the cutting stress, cutting temperature, tool wear and their intrinsic relationships in MMCs precision machining process. Heat generation, heat transfer and cutting temperature partition in workpiece, chips and cutting tool are simulated. A modified tool wear rate model is proposed, tool wear characteristics, wear mechanisms and dominate tool wear are further investigated against the real machining process. Cutting tool wear is monitored and assessed offline after machining experiments. The experimental study on the machined surface generation is presented covering cutting force, tool wear, tool life, surface roughness and machining efficiency. Process optimisation is explored by considering the variation of cutting parameters, cutting tool conditions and workpiece materials in order to achieve the desired outcomes and machinability.
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Cheng, Ming-Yi. "An experimental investigation into tool wear in micro-drilling of aluminium, aluminium/copper metal alloys and carbon fibre reinforced composites." Thesis, Brunel University, 2017. http://bura.brunel.ac.uk/handle/2438/14613.
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Limitation of conventional machining equipment has become a growing concern over the past two decades due to the demands for greater machining accuracy in today’s manufacturing. The development of micro-machining has therefore attracted significant attention; it signifies the advancement of national economy as well as the level of accuracy manufacturing industry could achieve. While the connection between tool lifespan, cost of machining and throughput is well established, the factor of tool lifespan appears to have more significance since the miniaturization of tool could lead to further performance concerns such as its lack of strength and durability. On the other hand, raising feed rate and spindle rotation speed are the two common approaches for increasing manufacturing throughput. Such approaches tend to cause an increase in the thrust force subjecting the tool to greater stress, which is the main cause of tool wear and even tool failure. Through literature review and preliminary experiments, it was found that spot-drill is often done prior to micro-drilling since it prepares a pre-drill countersunk hole that helps the alignment of tool for subsequent micro-drilling. Although such pre-drill step does improve the micro-drilling operation, the fundamental issue of tool diameter difference still remains. Often the tool used for pre-drill has a bigger diameter than the one for micro-drilling although a significant difference is always something to be avoided. This is because the difference has to be picked up by the tool used for micro-drilling and is directly linked to the wear caused by increased thrust force. In this research the operation of micro-drilling is investigated via mathematical models. Such operation is further broken down into various steps and stages so more detailed description can be achieved. The findings are then further enhanced by simulation based on the 3D model of micro-drilling. Three materials were selected for this research: Al 6061T, Al/Cu metal alloy panel and Carbon fibre reinforced composites. Such a selection enables the study of individual characteristics of different materials and the variation in respective thrust forces. Finally, Conclusions present the summary of the main findings from micro-drilling process analysis based on research and investigation shown in earlier chapters. By combining actual measurements on micro-drilling and mathematic model this research hopefully would improve the understanding towards micro-drilling processes.
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Samak, Mihir. "Role of Serum Albumin Aggregation in Lubrication and Wear Protection of Shearing Surfaces." Thesis, Université d'Ottawa / University of Ottawa, 2019. http://hdl.handle.net/10393/39403.
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Healthy articular joints exhibit remarkable lubrication due in large part to the complex rheological and tribological behavior of the synovial fluid (SF) that lubricates the joints. Current approaches that seek to elucidate such remarkable lubrication usually focus on the roles of high molecular weight SF components such as lubricin and hyaluronic acid but frequently overlook the role of serum albumin (SA), although it represents 90% of the protein content of SF. In this thesis, we used the Surface Forces Apparatus to investigate in detail the structural and tribological response of SA thin films when sheared between model surfaces and subjected to a large range of shearing parameters. Our data indicate that, under shear, SA films reproduce closely the shear response previously reported for SF, i.e., film thickening and formation of numerous long-lived aggregates accompanied by low friction and efficient surface protection against damage. More specifically, our detailed investigation of shear parameters reveals that (i) strong anchoring of SA to surfaces promotes the formation of large rod-like shaped aggregates that enable rolling friction and keep surfaces far apart, preventing damage, (ii) aggregation mechanism is irreversible, which makes aggregates long-lived (though mobile) in the contact, and (iii) aggregate formation only occur when SA was sheared above a ‘critical’ amplitude Ac and a critical shear velocity Vc.
Collectively, our results provide experimental evidence of the role of globular proteins, such as SA, in lubrication and establish a correlation between shearing parameters, formation and stability of aggregates, low friction and wear protection. Although our findings are based on experiments involving rigid, nonporous surfaces hence can hardly be generalized to compliant and porous cartilage surfaces, they are applicable to other rigid tribosystems such as artificial joints and will certainly advance our understanding of joint implants’ lubrication in SF mediated by protein aggregation, with implications for future design of artificial joints and therapeutic interventions.
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Doran, Marc C. "Nanoindentation as a Characterization Tool for Wear Resistance in Stainless Steels." The Ohio State University, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=osu1462807632.
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Absuelo, Ruby. "Employability of Philippine college and university graduates in the United States." Thesis, Edith Cowan University, Research Online, Perth, Western Australia, 2014. https://ro.ecu.edu.au/theses/868.
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Limited economic opportunity for many Filipinos has created substantial emigration of the country’s educated work force. The economic opportunities in the United States have attracted Philippine immigrants seeking employment opportunities. Thus, the U.S. now has a substantial foreign-born Filipino population. Although the majority of Philippine immigrants to the U.S. possess bachelor’s degrees or advanced degrees (Allard & Bureau of Labor Statistics, 2011; Camarota, 2012; Commission on Filipinos Overseas, 2012), many are underemployed or work in fields relatively unrelated to their education and experience.
This thesis examines Philippine college and university graduates’ social networks, educational attainment, degree field, English language proficiency, immigration status, age, and gender, factors which influence and determine Philippine graduates’ employability in the U.S. labour market. The Triangulation Mixed Methods Design also known as the Concurrent Triangulation Design was employed to effectively measure the complex phenomenon of Philippine graduates’ employability by integrating quantitative and qualitative data sets. The null hypotheses for this thesis were rejected exclusive of age and gender differences. Data revealed employability was enhanced when Philippine graduates networked with Weak Ties during initial employment and continued to be advantageous for being adequately employed (i.e. resulted in lower underemployment). However, lower employability and underemployment negatively affected graduates with a bachelor’s degree (particularly a business-related degree), those who were less proficient in English, and those who were Green Card holders. The factors that were influential in the employability of Philippine graduates coincided with the labour market demands of the American employers sampled in this study. The thesis found that the current status of Philippine graduates has improved substantially with a higher percentage of the respondents obtaining jobs commensurate with their educational qualifications as opposed to their initial employment.
Philippine graduates with medical technology degrees were particularly successful at obtaining jobs commensurate with their educational qualifications despite relatively few holding advanced degree, but on average this group had resided in the U.S. the longest. Graduates with business-related degrees continued to lag behind those in other degree fields and experienced lower employability and higher underemployment. Despite their initial employment disadvantage, these degree holders were less likely to pursue continuing education or receive additional U.S. school/educational credits. The findings of this thesis provide insight into the employability of Philippine graduates. Because of the sampling restrictions, the findings cannot be extrapolated beyond the scope of this research. These results should only be treated as indicative within the context of this research. However, they provide useful insights for policy-makers, stakeholders and academics in the Philippines.
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Boud, Fathi M. "An investigation of the relationship between temperature, forces and tool wear in turning and drilling." Thesis, Aston University, 1998. http://publications.aston.ac.uk/15284/.
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Developing a means of predicting tool life has been and continues to be a focus of much research effort. A common experience in attempting to replicate such efforts is an inability to achieve the levels of agreement between theory and practice of the original researcher or to extrapolate the work to different materials or cutting conditions to those originally used. This thesis sets out to examine why most equations or models when replicated do not give good agreements. One reason which was found is that researchers in wear prediction, their predictions are limited because they generally fail to properly identify the nature of wear mechanisms operative in their study. Also they fail to identify or recognise factors having a significant influence on wear such as bar diameter. Also in this research the similarities and differences between the two processes of single point turning and drilling are examined through a series of tests. A literature survey was undertaken in wear and wear prediction. As a result it was found that there was a paucity in information and research in the work of drilling as compared to the turning operation. This was extended to the lack of standards that exist for the drilling operation. One reason for this scarcity in information on drilling is due to the complexity of the drilling and the tool geometry of the drill. In the comparative drilling and turning tests performed in this work, the same tool material; HSS, and similar work material was used in order to eliminate the differences which may occur due to this factor. Results of the tests were evaluated and compared for the two operations and SEM photographs were taken for the chips produced. Specific test results were obtained for the cutting temperatures and forces of the tool. It was found that cutting temperature is influenced by various factors like tool geometry and cutting speed, and the temperature itself influenced the tool wear and wear mechanisms that act on the tool. It was found and proven that bar diameter influences the temperature, a factor not considered previously.
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Xia, Tian. "INVESTIGATION OF DRILLING PERFORMANCE IN CRYOGENIC DRILLING ON CFRP COMPOSITE LAMINATES." UKnowledge, 2014. http://uknowledge.uky.edu/me_etds/36.
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In recent years, there has been a substantial growth in the application of carbon fiber reinforced plastic (CFRP) composite materials in automobile and aerospace industries due to their superior properties such as lightweight, high strength, excellent corrosion resistance, and minimal fatigue concerns. The present study evaluates the drilling performance of woven carbon fiber reinforced plastics under both dry and cryogenic cooling conditions using uncoated solid carbide drill with a through-hole for coolant application.
The effects of the cooling conditions and the cutting parameters on drilling performance in drilling CFRP were evaluated in terms of generated thrust force, torque, cutting edge radius, outer corner flank wear, hole quality (including surface roughness, diameter error, roundness, delamination, burr formation, sub-surface quality). Both cooling conditions and cutting parameters were found to influence the thrust force and torque at different levels. The thrust force and the torque are higher in cryogenic cooling under all cutting parameters. In most of the cases, cryogenic drilling gives better bore-hole quality with lower surface roughness, more accurate diameter, less burr generation, better sub-surface quality, etc. Also, the tool-wear rates measured in drilling shows that cryogenic drilling produces less tool-wear than dry drilling does.
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Švec, Michal. "Silové zatížení frézovacích nástrojů při obrábění." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2020. http://www.nusl.cz/ntk/nusl-417539.
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This thesis compares the force load of two kinds of cutting tool inserts while milling. The thesis is devided into two main parts – research and experiment. The research part is focused on the theory of the force load measuring, cutting tools and cutting tool inserts and their coating. 14 grooves were made with each cutting insert while the force load was measured. Constant cutting conditions were applied. The experiment was repeated four times for each kind of cutting insert. The aim of the thesis is to determine if both kinds of inserts mill with the same force load. The results reveal that one kind of cutting tool inserts mill with the force load higher up to 85 %.
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Hebditch, Max. "Computational modelling approaches for studying protein-protein and protein-solvent interactions in biopharmaceuticals." Thesis, University of Manchester, 2018. https://www.research.manchester.ac.uk/portal/en/theses/computational-modelling-approaches-for-studying-proteinprotein-and-proteinsolvent-interactions-in-biopharmaceuticals(b965e1ee-0769-476c-970b-6c676468e577).html.
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Antibodies and antibody fragments are the largest class of biotherapeutics in development with many products already available in the clinic. Antibodies are promising due to their naturally high affinity and specificity for biological targets. A key stumbling block to biopharmaceutical development compared to small molecule drugs is the general requirement for a stable liquid formulation, which is often difficult to obtain due to issues with aggregation, phase separation, particle formation, and chemical instabilities. Aberrant solution behaviour limits the production, storage and delivery of the monoclonal antibody. Biopharmaceutical solution behaviour is determined by weak, transient protein-protein and protein-solvent interactions. An attractive interaction potential between proteins in solution can lead to association. Irreversible association occurs when proteins undergo large scale structural changes and aggregate. Reversible association is less severe, but can lead to undesirable solution properties such as high viscosity, phase separation and opalescence, which can lead to difficulties throughout the downstream processing and formulation steps. These problems can become exacerbated during formulation of antibodies when trying to achieve high protein concentrations often required for effective antibody dosage. Firstly, we studied the domains of the Fab fragment using statistical models and continuum electrostatic calculations and found that the CH1 domain is more soluble than the other domains and has properties of intrinsically disordered like proteins which is supported by observations in the literature. We then investigated the immunoglobulin superfamily and found 11 proteins which may have a similarly disordered nature. We present a new web server for predicting protein solubility from primary sequence using an in-house algorithm that weighs the contribution of various sequence properties for predicting solubility. Lastly, we conducted physical characterisation of an antibody and human serum albumin in pharmaceutically relevant buffers and found that the interaction potential can be modelled using spherical models from low to high protein concentration. We hope that the work outlined in this thesis will contribute to the theoretical understanding and modelling of protein solution behaviour.
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Jiao, Feifei. "Investigation on micro-cutting mechanics with application to micro-milling." Thesis, Brunel University, 2015. http://bura.brunel.ac.uk/handle/2438/12066.
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Nowadays technology development places increasing demands on miniature and micro components and products, and micro-milling is one of the most flexible machining processes in manufacturing 3D structures and complex structured surfaces. A thorough and scientific understanding on fundamentals of the micro-milling process is essential for applying it in an industrial scale. Therefore, in-depth scientific understanding of the micro-cutting mechanics is critical, particularly on size effect, minimum chip thickness, chip formation, tool wear and cutting temperature, etc. so as to fulfil the gap between fundamentals and industrial scale applications. Therefore, three key fundamental research topics are determined for this research, and a comprehensive study on those topics is conducted by means of modeling, simulation, experiments. The topics include chip formation process in micro-milling, novel cutting force modeling in multiscale and study on the tool wear and process monitoring. The investigation into chip formation process in micro-milling consists of three stages; the micro-cutting process is firstly simulated by means of FEA with a primary focus on finding the minimum chip thickness for different tool/material pair and explaining the size effect; the simulation results are then validated by conducting micro-cutting experiment on the ultra-precision lathe. Experiments are carried out on aluminium 6082-T6 with both natural diamond and tungsten carbide tool. By knowing the minimum chip thickness for different tool/material pair, the chip formation process is investigated by performing comparative study by using the diamond and tungsten carbide micro-milling tools. As the minimum chip thickness for diamond micro-milling tool is smaller than that for tungsten carbide tool compared to nominal chip thickness, MCT is ignored in diamond micro-milling. Thus the comparative study is conducted by utilizing both tools with perfectly sharpened cutting edge and tools with the rounded cutting edge in micro-milling. The chips are inspected and associated with cutting force variations in the micro-milling process. The findings are further consolidated by comparing with research results by other researchers. The cutting force modeling is developed in three different aspects, e.g. cutting force on the unit length or area and cutting force on the unit volume in order to better understand the micro-cutting mechanics in aspects of size effect, tool wear mechanism and the cutting energy consumption. The mathematical modeling firstly starts with a novel instantaneous chip thickness algorithm, in which the instantaneous chip thickness is computed by taking account of the change of tool geometry brought about by the tool runout; then the collected cutting forces are utilized to calibrate the model coefficients. For accurate measurement on cutting forces, the Kalman Filter technique is employed to compensate the distortion of the measured cutting force. Model calibration is implemented using least-square method. The proposed cutting force model is then applied in micro-milling to represent the conditions of tool wear and the cutting energy consumption. Further study on the surface generation simulation is based on force model and its comparison with the machined surface is also performed. Cutting experiments using the new tungsten carbide tool are carried out and the tool wear is monitored offline at different machining stages. The dominant tool wear types are characterised. Tool wear is investigated by mainly analysing cutting force at different tool wear status. Frequency analysis by Fourier Transform and Wavelet Transform are carried out on the force signals, and features closely related to the tool wear status are identified and extracted. The potential of applying these features to monitoring the tool wear process is then discussed. Experimental studies to machine the structured surface and nano-metric level surface roughness are presented, the machining efficiency, dimensional accuracy and tool-path strategies are optimised so as to achieve the desired outcomes. Moreover, investigation on cutting temperature in micro-cutting is also studied to some extent by means of simulation; the influence of cutting edge radius on cutting temperature is particularly investigated. Investigation on above aspects provides systematic exploration into the micro-milling process and can contribute substantially to future micro-milling applications.
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Abebe, Abay Damte, and Qikang He. "Foam Behavior Analysis Based On A Force Measurement System." Thesis, Högskolan i Halmstad, Akademin för ekonomi, teknik och naturvetenskap, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:hh:diva-37250.
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Abstract In the world where every sector of industrial manufacturing is being converted toautomated systems, surface finishing processes like sanding and polishing seem to lag.This phenomenon is not surprising as these processes are complex to optimize. Therehave been projects going on with the support of European Commission to findsolutions under SYMPLEXITY (Symbiotic Human-Robot Solutions for ComplexSurface Finishing Operations). One of the projects in under this include poliMATIC(Automated Polishing for the European Tooling Industry). Halmstad University isinvolved in doing projects. This project took a portion of this study in aim to understand a foam material’s behavior used for sanding tool at the tip of a robotic arm. This is studied using a forcemeasurement system developed at Halmstad University. The project has two sectionsand starts with one; Understanding the force measurement system and upgrading innecessary ways. Two; studying how the foam material compressive hardness propertyis affected when the material is fit with sandpaper for sanding operation using theforce measurement system. The study finally revealed how the combination of thefoam with sandpaper affects the robustness of the material, and significantlyimproved the output of the system with by reducing the noise level with 40%.
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Cai, Shaobiao. "3D numerical modeling of dry/wet contact mechanics for rough, multilayered elastic-plastic solid surfaces and effects of hydrophilicity/hydrophobicity during separation with applications." Columbus, Ohio : Ohio State University, 2008. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1205118488.
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Hahlin, Mattias. "Evaluation of variations of the frictional force between a bullet and a case in a loaded cartridge." Thesis, Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-68653.
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To ensure that manufactured cartridges is safe to use, a tensile test is performed. The frictional force between the bullet and the case is required according to Normas standard to be between 15 – 75 Kg. Variations of the frictional force, with values outside of the standard had been noted by Norma Precision without understanding the cause. The aim of this report was to investigate and evaluate possible causes of the variations measured by tensile tests, difference between extreme values and to find a solution to what can be done to prevent the variations. Two different cases and three different bullets were used by request from Norma in the scope of this report. Different combinations of the bullets and cases was tested by alternating process parameter, surfaces and loading procedures. The loaded cartridges went through tensile tests to investigate differences. Bullets and cases with extreme values from the measured frictional force were chosen for further investigation in SEM and profilometer. To be able to draw further conclusions four different simulation models was created in Abaqus and different parameters was calculated. The dimensions and shape of the bullet resulted as the cause of changes of the tensile test curves. The smallest frictional force was found to differ from the largest by a change in wear mechanism from mainly abrasive ploughing to cutting and adhesion that caused transfer of material from the bullet to the case. The change in wear mechanism was found to be caused by an increased bullet diameter. The loading procedure was found to cause variations in plastic deformation on the neck of the case and damage the bottom of the bullet. The loading procedure was assumed to have the largest impact on the variations in frictional force. To minimize the variations the central axis of the case was suggested to be in line with the central axis of the bullet.
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Kull, Neto Henrique 1988. "Uma contribuição ao estudo do fresamento de liga de titânio : vida de ferramenta, forças de corte e rugosidade da peça." [s.n.], 2013. http://repositorio.unicamp.br/jspui/handle/REPOSIP/263046.
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Orientador: Anselmo Eduardo DinizDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica
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Resumo: O titânio e suas ligas são considerados materiais de baixa usinabilidade devido a diversas propriedades inerentes ao material. Dentre elas pode-se citar a alta resistência mecânica em altas temperaturas, a baixa condutividade térmica, a alta reatividade química com os materiais de ferramentas e o baixo módulo de elasticidade (que é um fator incentivador de vibrações). Devido à alta tendência à vibração que a usinagem (principalmente o fresamento) de titânio tem para se usinar da maneira mais produtiva possível ligas de titânio, há que se lidar com a vibração da ferramenta e/ou da peça. O presente trabalho busca aprofundar o estudo do fresamento frontal da liga Ti-6Al-4V, tendo como objetivos: encontrar material de haste da ferramenta que diminua a vibração no processo de usinagem, para com isso aumentar a vida da ferramenta de corte, e encontrar condições de usinagem (velocidade de corte e avanço por dente) que proporcionem maior vida da ferramenta. As hastes de aço furada e preenchida com poliuretano proporcionaram aumento da frequência natural do porta-ferramentas. Entretanto, foi verificada uma redução da rigidez do porta-ferramentas, que gerou grande variação dos esforços de corte e maior carregamento radial. Os resultados mostraram que quando se utiliza baixas rotações, portanto baixa frequência de entrada de dentes, a deflexão da ferramenta passa a ser o fator de maior contribuição para o fim de vida da ferramenta e, portanto, as hastes de aço furada e preenchida com poliuretano proporcionaram menores vidas da ferramenta que as hastes comerciais de aço maciça e de metal duro. O principal mecanismo de desgaste verificado em todos os testes foi o attrition, com microlascamento da aresta de corte. Quando se verificou a influência da velocidade de corte, do avanço por dente e do material da haste da fresa (aço ou metal duro) na vida da fresa medida em volume de cavaco removido por aresta, constatou-se que o único parâmetro que influenciou a vida da ferramenta foi à velocidade de corte
Abstract: Titanium and its alloys are known as difficult to machine materials because of their unique combination of properties, such as high strength at elevated temperatures, low thermal conductivity, high chemical reactivity with almost all tool materials and low modulus of elasticity (which favors vibration). Because of the high tendency of vibration in titanium milling, it is necessary to keep vibration under control in order to achieve high productivity. This work focused on the study of tool life, cutting forces and work piece roughness in the end milling of Ti-6Al-4V alloy. The main objectives were to find a tool holder material that provides reduction of vibration in the milling process, increasing tool life, and to find cutting parameters (cutting speed and feed per tooth) that provide longer tool lives. The bored tool holder and the tool holder filled with polyurethane exhibited higher natural frequency. However, it was noticed a decrease in the tool holder stiffness, which caused variation of cutting force and higher axial load. Results showed that at low cutting speeds (with low cutting frequency), tool holder deflection is the main factor affecting tool life and, therefore, the bored and the polyurethane filled tool holders generated shorter tool lives than the commercial tool holders of steel and cemented carbide. Attrition was the main wear mechanism in all tests. The influence of cutting speed, feed per tooth and tool holder material (steel and cemented carbide) on the tool life (measured in terms of volume of chip removed per cutting edge) was analyzed. It could be seen that the only parameter which had any influence on tool life was the cutting speed
Mestrado
Materiais e Processos de Fabricação
Mestre em Engenharia Mecânica
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中本, 剛., Takeshi NAKAMOTO, 英二 社本, Eiji SHAMOTO, 義丈 山崎, Yoshitake YAMAZAKI, 洋一 白形, and Youichi SHIRAKATA. "レーザー焼結によるホウ化チタン砥石の開発 (ホウ化チタン成膜と研削性能の基礎研究)." 日本機械学会, 2006. http://hdl.handle.net/2237/9004.
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Manarelli, Flávio Henrique. "Estudo do desgaste das ferramentas no microfresamento frontal." Ilha Solteira, 2018. http://hdl.handle.net/11449/157492.
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Orientador: Alessandro Roger RodriguesResumo: A microusinagem é um dos processos de fabricação capaz de produzir produtos ou geometrias de precisão e complexidade com detalhes menores que 1 mm. Contudo, para um melhor desempenho do processo de usinagem associado à qualidade do produto, entender a interação peça-ferramenta é fundamental. Esta pesquisa determinou a influência do tipo de corte e do avanço da ferramenta no desgaste da fresa (ferramenta), na energia específica de corte (processo) e na rugosidade (peça), ao empregar a operação de microfresamento de topo no aço COS AR60 de grãos ultrafinos. Os ensaios foram realizados em um centro de usinagem Romi D600 com a adaptação de um cabeçote de alta rotação (60 krpm) sem aplicação de fluido de corte. Microfresas de topo reto (Ø 800 µm) com substrato de metal duro e revestidas com TiAlN foram aplicadas nos testes. A profundidade de usinagem e a velocidade de corte foram mantidas constantes em 160 µm e 60 m/min, respectivamente. Foram variados o avanço por dente (3 e 10 µm/z) e o tipo de corte (simétrico em cheio e em face e assimétrico concordante e discordante). Análise de Variância (ANOVA) com intervalo de confiança de 95% foi aplicada a cada uma das três réplicas. Os resultados indicaram que os níveis de desgaste e a redução do diâmetro da microfresa são influenciados pelo avanço da ferramenta e tipo de corte. As maiores reduções no diâmetro (≈11%) foram devido ao impacto periódico da aresta de corte na peça e não pelo efeito de sulcamento (≈4%). Além disso, para o pe... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: Micro-machining is one of the processes feasible for generating geometries or parts with precision and complexity regarding dimensions smaller than 1 mm. However, the achievement of enhanced machining performance and product quality requires a prior understanding on the tool-workpiece interface. This research detemined the influence of cutting type and cutting feed on wear (tool), specific cutting force (process) and surface roughness (workpiece) when cutting the ultrafine-grained steel COS AR60 under end milling strategy. Machining tests were performed in a CNC machining centre Romi D600 provided with a high-speed spindle (60kpm) without cutting fluid application. TiAlN coated carbide endmill (Ø 800 μm) was used for straight cut with 60 m/min cutting speed, 160 μm depth of cut and feed per tooth of 3 and 10 μm. Analysis of Variance (ANOVA) with confidence interval of 95% was applied to the three runs of each cutting sets. The results have shown that tool wear levels and tool effective diameter are influenced by tool feed and cutting type. Hence, intermittent impact of tool’s cutting edges into the workpiece (≈11%) during cutting revealed to be the major cause of tool wear when compared to cutting mechanism dominated by ploughing (≈4%). Regarding experimental sets with cutting length of 98,018 m there was a predominance of tool edge chipping over abrasion and adhesion when performing face cutting with ploughing at 4.2%. On the other hand, if ploughing increases to 14.3% the m... (Complete abstract click electronic access below)
Mestre
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Živko, Pavlović. "Karakterizacija površinske strukture neštampajućih elemenata CtP termalne štamparske forme za ofset štampu." Phd thesis, Univerzitet u Novom Sadu, Fakultet tehničkih nauka u Novom Sadu, 2012. http://dx.doi.org/10.2298/NS20120519PAVLOVIC.
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Disertacija daje pregled novih i relevantnih istraživanja i stavovau naučnoj zajednici na temu štamparskih formi i uticaja procesaštampe na trošenje neštampajućih elemenata. U disertaciji jeukazano na kontinualno praćenje topografskih promenaneštampajućih elemenata štamparskih formi kako bi se kontrolisaoperiod eksploatacije a time i proces reprodukcije. Takođe dajeprilog novim istraživanjima sa analizom velikog brojaeksperimentalnih uzoraka sa dobijenim izmerenim podacima iodgovarajućim korelacijama i predstavlja napredak u shvatanjumehanizma trošenja neštampajućih površina štamparskih formi injihov uticaj na tribološke promene u odnosu na strukturu osnovealuminijuma i sloja aluminijum oksida.Dissertation gives an overview of the current state, research and theories ofprinting forms and influence of printing process on wearing of non-printingelements within the science community. The dissertation points out the continuousmonitoring of topographic changes of printing form non-printing elements to controlthe exploitation of a period of time and the process of reproduction. This workcontributes to new research with the analysis of large number of experimentalsamples and calculated correlations and represents an advance in thecomprehension of the surface wear mechanism of printing form non-printingelements and their influence on the tribological changes to the structure of thebase layer of aluminium and aluminium oxide.
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Mandard, Romain Baptiste. "Dynamique de contact aube- revêtement abradable : identification expérimentale de la force et des mécanismes d'interaction." Thesis, Ecole centrale de Lille, 2015. http://www.theses.fr/2015ECLI0001.
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Le rendement des compresseurs aéronautiques est amélioré en minimisant le jeu entre les aubes en rotation et le carter qui les entoure, réduisant ainsi les fuites aérodynamiques. Ce jeu réduit occasionne des contacts entre les aubes et le carter ; afin d’assurer leur intégrité mécanique, le carter est revêtu d’un matériau abradable sacrificiel, lequel accommode les incursions d’aube. Les interactions aube – revêtement abradable couplent des phénomènes tribologiques et vibratoires à haute vitesse et à haute température, dont l’étude expérimentale est requise pour le développement de modèles numériques prédictifs. L’objectif de cette thèse est d’identifier expérimentalement la force et les mécanismes d’interaction aube-abradable AlSi-Polyester dans une configuration d’essai représentative du fonctionnement des étages de compresseur basse-pression. Des méthodes couplées expérimentales - analytiques, prenant en compte la dynamique d’aube, ont été développées afin d’accéder à la force d’interaction et à l’incursion aube-abradable. L’influence de la température, de la nuance du matériau abradable et de la raideur d’aube a été étudiée. Les mécanismes d’usure et d’endommagement du revêtement abradable ont été investigués et corrélés aux conditions d’interaction. Ces travaux de thèse ont été réalisés dans le cadre d’une collaboration entre le Laboratoire de Mécanique de Lille, SNECMA Villaroche (groupe SAFRAN) et le centre ONERA de LilleMinimizing the clearance between turbofan blades and the surrounding casing is a key factor to re-ducing leakage flows and consequently improving efficiency. The tight clearance may lead to blade-casing interactions. An abradable coating is deposited on the casing to accommodate blade incursions and thus to protect the blades and the casing from severe damage. Blade/abradable-coating interactions involve tribological and vibratory phenomena at high velocity and temperature. Experimental knowledge of these interactions is paramount to the proper design of abradable materials and the prediction of their lifetimes through numerical simulations. The purpose of this thesis is to identify experimentally the force and the mechanisms occuring during interaction between a vibrating blade and an AlSi-Polyester abradable coating. To this end, experiments were conducted on a dedicated test rig, in conditions representative of low-pressure compressor situation. Specific methods involving dynamical measurements and analytical models have been developed in order to obtain the blade/abradable-coating interacting force as well as the blade tip incursion. The influence of temperature, coating nature and blade stiffness has been studied. The interaction mechanisms and wear of the abradable coating have been investigated and correlated with the interaction conditions. This work was achieved within the framework of cooperation between Laboratoire de Mécanique de Lille (France), SAFRAN-SNECMA (France) and ONERA, the French Aerospace Lab
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Ferreira, Mauro Fernando. "Influência da soldagem de revestimento na vida útil de ponteiras sulcadoras de semeadoras adubadoras." Universidade Federal de Pelotas, 2008. http://repositorio.ufpel.edu.br/handle/ri/1168.
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Previous issue date: 2008-11-28This work had as objective to analyze alternatives to increase the useful life of the ferrules of hoe opener rods of no-till planters, through the addition of covering welding. It was verified the performance of five welding types, being used covered electrodes and tubular wire, over the extremity of the hoe. The tests were executed in franc-sandy soil characterized physically by its texture, plasticity index, density, and water tenor, as well as the resistance to the penetration. The wearing, the horizontal and vertical force were obtained in intervals of 10,5km to the limit of 52,5km. The results indicated that the witness ferrule has lost in the average of the experiment 38,41% of its initial mass when it traveled 52,5km while the other welded ferrules traveled between 61,0km and 108,7km to reach the same mass reductions. It was observed that the vertical and horizontal forces contributed with 11% and 89%, respectively, of the resulting force in the hoe. With the use of the coverings, it was obtained an increase of the area worked in the sowing, for the largest durability of the tools, between 2,0ha and 13,4ha, in relation to the witness. The theoretical field efficiency was larger when it was used the coverings. The tubular wire increased in 5,1% in relation to the ferrule without covering. Starting from the found results we can conclude that it is possible to increase the useful life of the ferrules of furrow opener rods through the addition of welding material and that the conservation of the geometry of the tools, provides the maintenance of the forces that have action on these ones as well as their functional characteristics.
Este trabalho teve como objetivo analisar alternativas para o aumento da vida útil das ponteiras de hastes sulcadoras de semeadoras adubadoras, através da adição de soldagem de revestimento. Verificou-se o desempenho de cinco tipos de soldagem, utilizando-se eletrodos revestidos e arame tubular, sobre a extremidade das ponteiras. Os testes foram executados em solo franco-arenoso caracterizado fisicamente pela sua textura, índice de plasticidade, densidade e teor de água, assim como a resistência à penetração. O desgaste, a força horizontal e vertical foram obtidos em intervalos de 10,5km até o limite de 52,5km. Os resultados indicaram que a ponteira testemunha perdeu na média do experimento 38,41% da sua massa inicial quando percorreu 52,5km enquanto que as demais ponteiras soldadas percorreram entre 61,0km e 108,7km para atingir as mesmas reduções de massa. Observou-se que as forças verticais e horizontais contribuíram com 11% e 89%, respectivamente, da força resultante na ponteira. Com o uso dos revestimentos obteve-se um aumento da área trabalhada na semeadura, pela maior durabilidade das ferramentas, entre 2,0ha e 13,4ha, em relação à testemunha. A eficiência de campo teórica foi maior quando se utilizou os revestimentos sendo que o arame tubular aumentou em 5,1% em relação à ponteira sem revestimento. A partir dos resultados encontrados conclui-se que se pode aumentar a vida útil das ponteiras de hastes sulcadoras através da adição de material soldável e que a conservação da geometria das ferramentas, proporciona a manutenção das forças atuantes sobre estas assim como a suas características funcionais.
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Hassaini, Roumaissa. "Etude de la turbulence d'ondes élastiques et gravito-capillaires : de l'idéal théorique aux conditions réelles ?" Thesis, Université Grenoble Alpes (ComUE), 2018. http://www.theses.fr/2018GREAI064/document.
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La turbulence d'onde faible (TTF) est une théorie statistique appliquée à un ensemble d'ondes aléatoires non cohérentes et dispersives. En supposant un domaine infini et une nonlinéarité infinitésimale, une prédiction sur la cascade d'énergie entre échelles par le biais d'interactions résonantes des échelles d'injection aux échelles dissipatives est alors possible. La théorie semble souvent mise en défaut par la confrontation expérimentale pour les ondes de surface. Une explication potentielle de cette divergence entre expérience et théorie est l'aspect fortement restrictif des hypothèses nécessaires à la validité de la théorie. Nous proposons dans cette thèse d'explorer l'impact du non-respect de certaines de ces hypothèses sur les propriétés statistiques de la turbulence. Des expériences à l'interface de deux liquides non-miscibles ont été entreprises afin d'étudier l'impact de l'augmentation de la dissipation visqueuse et donc de la réduction du temps dissipatif sur la mise en place de la cascade d'énergie. Une expérience à la surface de l'eau avec un confinement progressif de la largeur de la cuve a été effectuée afin d'observer une potentielle coexistence de la turbulence discrète, dans la direction confinée, et continue, dans la direction non confinée. Une analyse expérimentale des ondes gravito-capillaires où la dispersion a été réduite a permis de mettre en lumière une transition d'un régime de TTF vers un régime contenant des structures cohérentes localisées que sont les solitons. Afin de vérifier si une telle transition peut être visible sur un système physique différent, une étude expérimentale et numérique ont été conduites sur les ondes dans une plaque élastique précontrainte. Dans ce milieu l'effet de dispersion des ondes de flexion et en compétition avec le caractère non-dispersif des ondes de tension. Nous nous intéresserons par ailleurs numériquement aux régimes faiblement et fortement non-linéaires des ondes purement non-dispersives dans la membraneWeak wave turbulence (WTT) is a statistical theory applied to a large number of incoherent and dispersive waves. Based on the hypothesis of small non-linearity and infinite domain the theory predicts an energy cascade from the forcing scales to the dissipative scales. The confrontation of WTT to experiment for surface waves raises many inconsistencies. The strong hypotheses on which is developed the WWT may be the explanation of such disparity between experiment and theory. The aim of this Thesis is to investigate the impact of the invalidation of some of these conditions on the statistical properties of turbulence. Experiments of interfacial waves between two non-miscible fluids with different viscosities have been carried out to characterize the effect of the increase of viscous dissipation on the energy cascade. An experiment at the surface of water with an increasing confinement of the width of the vessel has been done in order to possibly observe a co-existence between discrete turbulence and classical turbulence. An experimental study of gravity-capillary waves with a decrease of dispersion led us to the observation of a transition to a solitonic regime. In order to verify whether such a transition can be observed in a different physical system, an experimental and numerical study were conducted on the waves in a prestressed elastic plate. In this medium, the effect of dispersion of bending waves is competing with the non-dispersive aspect of stretching waves. We also studied weakly and strongly non-linear regimes of purely stretching waves in a membrane
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Flodr, Vojtěch. "Testování řezných nástrojů povlakovaných nanokrystalickými kompozity." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2009. http://www.nusl.cz/ntk/nusl-228891.
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The thesis is focused on the characteristic of coating methods and their division, on the morphology of defects and cause of wear in coated cutting tools of sintered carbides. The experimental part is focused on a comparing cutting performance testing of indexable cutting inserts coated with nanocrystaline composite TiAlSiN at the longitudinal turning.
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Åkerman, Jonas. "Extensions in Flux : An Essay on Vagueness and Context Sensitivity." Doctoral thesis, Stockholms universitet, Filosofiska institutionen, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-30080.
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The extensions of vague predicates like ‘is bald’, ‘is tall’, and ‘is a heap’ apparently lack sharp boundaries, and this makes such predicates susceptible to soritical reasoning, i.e. reasoning that leads to some version of the notorious sorites paradox. This essay is concerned with a certain kind of theory of vagueness, according to which the symptoms and puzzles of vagueness should be accounted for in terms of a particular species of context sensitivity exhibited by vague expressions. The basic idea is that the extensions of vague predicates vary with certain contextual factors, and that this fact can explain why they appear to lack sharp boundaries. This kind of view is referred to as contextualism about vagueness. A detailed characterisation of contextualism about vagueness is given in chapter two and three. In chapter two, a generic version of contextualism about vagueness is developed, and some alternative forms of context sensitivity are introduced. In chapter three, the specific contextual factors appealed to by different contextualists are discussed. In chapter four, different contextualist diagnoses of the sorites paradox are considered, and found to be problematic in various ways. It is argued that contrary to what some of its proponents have claimed, contextualism about vagueness is not superior to other comparable theories of vagueness when it comes to explaining the appeal of soritical reasoning. In chapter five, a certain version of the sorites paradox, known as the forced march sorites, is discussed. It is argued that “data” about how speakers would behave in the forced march cannot lend any firm support to contextualism about vagueness. In chapter six, some problems concerning the instability of the contextual factors are considered. One problem is that contextualist diagnoses of the sorites which locate a fallacy of equivocation in the reasoning seem to render non-soritical reasoning fallacious as well. A model for treating this problem is suggested, but on closer consideration, it turns out to be problematic. Moreover, this model is of no help in solving the more general problem that even if classical logic remains valid for vague language on some contextualist views, the instability of the extensions of vague predicates makes it difficult to know when a certain piece of reasoning instantiates a valid argument form. Other difficulties arise with respect to speech reports and belief contents. Chapter seven concludes with a summary and some methodological remarks.
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Antonialli, Armando Italo Sette. "Uma contribuição ao fresamento frontal da liga de titanio Ti-6Al-4V." [s.n.], 2009. http://repositorio.unicamp.br/jspui/handle/REPOSIP/264153.
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Orientador: Anselmo Eduardo DinizDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica
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Resumo: As ligas de titânio apresentam baixa usinabilidade devido à reduzida condutividade térmica, à manutenção de suas propriedades mecânicas em altas temperaturas, à elevada afinidade química com os materiais de ferramentas e ao baixo módulo de elasticidade. Esta última característica promove instabilidade da espessura de corte, o que se traduz em altos níveis de vibração, especialmente em processos de usinagem caracterizados por corte interrompido. Este trabalho trata da otimização do fresamento frontal da liga de titânio Ti-6Al-4V a partir da minimização da vibração da ferramenta através de variações do ângulo de posição da ferramenta e do ângulo de contato entre o inserto e o corpo de prova. Os resultados mostram que a utilização de um ângulo de posição reduzido prolonga a vida da ferramenta por associar a maior parte do carregamento radial a freqüências muito baixas, nas quais a ferramenta se comporta como um corpo rígido. O emprego de um ângulo de contato reduzido, por outro lado, é extremamente danoso à vida da ferramenta, pois a entrada do inserto no corpo de prova se dá em condições adversas. Attrition seguido de microlascamentos da aresta, nas condições em que houve vibração excessiva ou intenso choque na entrada do inserto, e difusão, nas condições dinamicamente mais estáveis, foram os principais mecanismos de desgaste de ferramenta verificados neste trabalho
Abstract: Titanium alloys present poor machinability because of their low thermal conductivity, their ability to keep good mechanical properties at high temperatures, their high chemical affinity to tool materials and their low Young modulus. This last characteristic generates instabilities of cutting thickness, which means high vibration levels, especially in machining processes involving interrupted cutting. This work studies Ti-6Al-4V titanium alloy face milling optimization by tool vibration reduction using different tool entering angles and different radial immersion angles between tool and workpiece. Results show that using low entering angle do extends tool life due to associating most radial load with very low frequencies, in which tool behaves like a rigid body. On the other hand, using low radial immersion angle extremely impairs tool life, as tool insert enters the workpiece on adverse conditions. Attrition followed by cutting edge microchipping, on experiments in which high vibration levels or intense shock on tool insert enter where found, and diffusion, on experiments dynamically more stable, were the main tool wear mechanisms observed in this work
Mestrado
Materiais e Processos de Fabricação
Mestre em Engenharia Mecânica
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Pires, Bruno Jorge. "Estudo das forças, vibrações e desgaste das ferramentas no fresamento da liga de titânio Ti-6A1-4V." [s.n.], 2011. http://repositorio.unicamp.br/jspui/handle/REPOSIP/264148.
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Orientador: Anselmo Eduardo DinizDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica
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Resumo: Ligas de titânio já apresentam um papel de grande importância na indústria aeroespacial, petroquímica e de biomateriais. A combinação de alta resistência mecânica, baixa densidade, resistência à corrosão, biocompatibilidade, boa tolerância tecidual e manutenção de suas características em altas temperaturas, configuram o titânio como um material excepcional para projetistas de diversas áreas. Infelizmente, estas boas qualidades não se refletem na sua usinabilidade. Uma vasta lista de problemas devem ser contornados durante a usinagem de ligas de titânio dentre os quais, altas temperaturas e pressões de corte, baixo módulo de elasticidade (incentivador de vibrações), alta afinidade química com os materiais das ferramentas e problemas com integridade superficial das peças usinadas. Com o objetivo de aprimorar o entendimento da usinagem de ligas de titânio, em especial do processo de fresamento frontal da liga Ti-6Al-4V, o presente trabalho teve como enfoque tecnológico a influência do material do porta-ferramenta (haste de aço e de metal duro) e a geometria do inserto de corte (ângulo de saída neutro e positivo) sobre a vida da ferramenta e forças de usinagem (Força Radial, Tangencial e Axial). Análises de espectrometria de energia dispersiva foram conduzidas a partir de microscopia eletrônica dos insertos desgastados, permitindo a identificação dos elementos químicos presentes e avaliação dos mecanismos de desgaste predominantes. O principal resultado obtido indica que a utilização de ferramentas com haste de metal duro não representou benefícios em termo de vida da ferramenta, apresentando desempenho muito próximo das ferramentas com haste de aço
Abstract: Titanium alloys play a major role in the aerospace, petrochemical and biomaterials industry. The combination of mechanical strength, low density, corrosion resistance, biocompatibility and maintenance of these characteristics at high temperatures, shape titanium as a exceptional material for designers from different areas. Unfortunately, these impressive qualities reflect negatively on its machinability. A substantial list of problems must be overcome during the machining of titanium alloys, among them high temperatures and pressures of cut, low elasticity modulus (which is a motivational factor for vibrations), high chemical affinity with almost all tools materials and problems with surface integrity of machined parts. In order to improve the understanding of titanium alloys machining, in particular front milling of Ti-6Al-4V, the present thesis focused the influence of the tool holder material (steel and carbide) and the cutting insert geometry (neutral and positive rake angle) on the tool life and machining forces (Radial, Axial and Tangencial Forces). Analysis of energy dispersive spectroscopy were also conducted from scanning electron microscopy of wear inserts, allowing the identification of chemical elements and evaluation of wear mechanisms predominate. The main result indicates that the use of carbide tool holders not represent benefits in terms of life tool, with performance very close to the steel tool holders
Mestrado
Materiais e Processos de Fabricação
Mestre em Engenharia Mecânica
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Čejka, Libor. "Produktivní obrábění titanových slitin." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2013. http://www.nusl.cz/ntk/nusl-230589.
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The aim of the thesis is to analyze the production costs and optimize cutting conditions for high-feed face milling of titanium alloy Ti6Al4V. In the experiment were changed cutting conditions, such as cutting speed vc and feed speed vf. During the experiment were checked cutting forces by dynamometr. Furthermore, surface roughness and tool wear is observed.
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Axmanová, Hana. "Moderní řezné nástroje pro zapichování a upichování." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2013. http://www.nusl.cz/ntk/nusl-230619.
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The presented diploma thesis is divided into two parts. The theoretical part deals with modern catting tools for grooving and cutting-off, choice of material of catting inserts, and with types of tool wear and their classification. The second part of the thesis deals with calculation of volumetric wear of catting tool for grooving. There was measured the power load of the new and worn tool in the experimental part and the observed data were evaluated by software. The graphs of power load and volumetric wear of tool were created.
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Le, Mercier Kévin. "Stratégie numérique et expérimentale pour la maîtrise des dégradations des outillages en mise en forme à froid." Thesis, Valenciennes, 2017. http://www.theses.fr/2017VALE0007/document.
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La mise en forme à froid des alliages d’aluminium peut être limitée par les transferts de matière sur la surface des outillages pouvant mener au grippage. L’objectif de ce travail de thèse est de contribuer à une meilleure compréhension de ces mécanismes pour permettre à terme d’optimiser les procédés de formage d’un alliage Al-Mg-Si. Une approche couplée expérimentale et numérique est développée afin d’alimenter une base de données d’indicateurs de dégradations des surfaces. L’approche expérimentale développée au cours de ces travaux repose sur l’utilisation de l’essai de compression-translation. Ce dispositif permet de reproduire une large gamme de conditions de contact rencontrées en mise en forme à froid. Une méthode d’analyse des surfaces reposant sur des mesures par profilométrie optique et des analyses au microscope électronique à balayage est développée afin d’évaluer le volume de matière adhérée sur les outils de chaque configuration d’essai. Le comportement rhéologique de l’alliage Al-Mg-Si est caractérisé à l’aide du simulateur thermomécanique GLEEBLE 3500 sur la gamme de températures de 298 à 423 K et à deux vitesses de déformation de 0,1 et 1 s-1. Un modèle de comportement physique reposant sur l’analyse du taux d’écrouissage et l’utilisation du modèle de la contrainte mécanique seuil est développé puis implémenté dans un logiciel éléments finis. Un modèle numérique de l’essai de caractérisation tribologique est développé. Il s’agit d’une analyse thermomécanique utilisant la formulation arbitrairement lagrangienne-eulérienne. Les données locales telles que la pression de contact et la vitesse de glissement calculées par ce modèle permettent de mieux comprendre les mécanismes de collage observés expérimentalement. Enfin, un programme de traitement des résultats numériques est développé afin de réaliser les modifications géométriques de la surface de l’outil en fonction du dépôt relevé expérimentalement. Un modèle d’usure basé sur le travail des forces de frottement est identifié. Ce dernier est un bon indicateur de la tendance au collage et permet une première approximation de ce mécanismeCold forming of aluminium alloys can be limited by a severe material transfer to the die surfaces, compromising the process viability. The purpose of this research work is to contribute to a broader understanding of the galling mechanisms which would further allow the optimisation of the forming processes of an Al-Mg-Si alloy. A methodology combining experimental and numerical approaches is introduced in order to build up a database of surface degradations indicators. The experimental approach is carried out by means of upsetting-sliding tests which reproduce a wide range of contact conditions experienced at the tool/workpiece interface during cold forming operations. To evaluate the amounts of adhered material on the tools of each test configuration, surface topography acquisitions are performed by optical profilometry and coupled to scanning electron microscope analyses. Axisymmetric compression tests are carried out by means of the GLEEBLE 3500 thermomechanical simulator to determine the deformation behaviour of the Al-Mg-Si alloy at high strains, in the temperature range of 298 to 423 K and strain rates of 0.1 and 1 s¡1. A constitutive model based on both the Mechanical Threshold Stress model and the analysis of the work-hardening rate is proposed and then implemented in a finite element code. A finite element simulation of the upsetting-sliding test, which is a thermomechanical analysis using the arbitrary lagrangian-eulerian formulation, is introduced. The local contact variables such as the contact pressure and the sliding velocity are evaluated through this simulation and allow a better understanding of the galling mechanisms observed experimentally. Finally, a post-processing program, which analyses the results of the finite element simulation and updates the tool shape according to the amount of adhered material determined experimentally, is developed. A wear model based on the friction work is introduced. This model is a good indicator of the galling tendency and allows a first approximation of this mechanism
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Marc, Estelle. "Analyse de la réponse tribologique d'un contact cylindre/plan soumis à des sollicitations de fretting sous chargement complexe : influence d'une solution Lithium-Bore." Thesis, Lyon, 2018. http://www.theses.fr/2018LYSEC001/document.
Full textAbstract:
Ce mémoire présente une analyse de la réponse tribologique d’un contact cylindre/plan soumis à des sollicitations de fretting sous chargement complexe, à savoir une sollicitation normale de force sinusoïdale et une sollicitation tangentielle de déplacement sinusoïdal, toutes deux possiblement sujettes à des fluctuations d'amplitude, de fréquence et de déphasage entre sollicitations. On s'intéresse plus particulièrement à l’usure des guides de grappe en 304L par les crayons en 316L nitrurés, induite par les vibrations de l’écoulement du fluide primaire dans les réacteurs nucléaires.L’étude expérimentale menée dans un environnement non représentatif mais très simple, à savoir un milieu sec et à l'ambiante, montre une usure non négligeable des deux contre-corps ce qui révèle les propriétés fragiles du tube nitruré dans cet environnement. Une très forte dépendance des faciès d’usure avec l’amplitude de glissement est notée. Seule la cinétique d’usure du tube nitruré est influencée par l'évolution de la charge normale. Aussi, une description analytique de l’énergie de frottement est développée, en prenant compte de l’ensemble des paramètres de chargement.En solution aqueuse lithium-bore, choix de milieu un peu plus représentatif mais en restant néanmoins à l'ambiante, seul le plan en acier 304L s’use, le cylindre en acier 316L nitruré n’étant pas sujet à de l'usure détectable. Un couplage avec des phénomènes corrosifs est proposé. En fretting simple, le confinement du contact augmente localement la valeur du pH et l’analyse de l’influence de la fréquence de fretting suggère que seule la couche passive est usée entre chaque glissement. Sous chargement complexe, la fluctuation de la charge normale permet une meilleure accessibilité de la solution dans l’interface frottée, augmentant localement les effets tribocorrosifs. Une loi d’usure multiplicative prenant en compte les différents effets de fluctuation des sollicitations est introduite et sa stabilité est vérifiée.Un modèle de calculs par éléments finis permet de simuler les profils d’usure en fretting simple et aussi en présence de force normale variable. En fretting simple, les résultats de simulation d'essais où seul le plan 304L s'use sont satisfaisants. En revanche, la non-superposition des profils expérimentaux et numériques lorsque la force normale fluctue confirme la présence de phénomènes physiques dans l'interface non encore représentés dans l'outil numériqueThis PhD thesis presents an analysis of the fretting wear of a cylinder/plane contact subject to complex loading conditions, namely a normal sinusoidal force solicitation and a tangential sinusoidal displacement, both possibly subject to fluctuations in amplitude, frequency and phase shift between signals. The purpose of this work is to study the wear of 304L cluster guides by nitrided 316L rods due to flow-induced vibrations of primary fluid in nuclear reactors.Firstly, the experimental study conducted in a dry and ambient temperature - a non-representative but very simple environment - shows significant wear of both counter-bodies, which reveals the fragile properties of the nitrided tube in this environment. A very strong dependence of the fretting scar morphology with the sliding amplitude is noted. Only the wear kinetics of the nitrided tube is influenced by the evolution of the normal load. Also, an analytical description of friction energy is developed, taking into account all loading parameters.In a second hand, in aqueous lithium-boron solution, a slightly more representative choice of medium but still remaining in the ambient, only the 304L steel plane wears out, the 316L nitrided steel cylinder is not subject to detectable wear. A coupling with corrosive phenomena is proposed. In simple fretting, contact confinement locally increases the pH value. Moreover, the analysis of the influence of the fretting frequency suggests that only the passive layer is worn between each slip. Under complex loading, the fluctuation of the normal load allows a better accessibility of the solution in the rubbed interface, increasing locally the tribocorrosive effects. A multiplicative wear law taking into account the various effects of normal force fluctuation is introduced and its stability is checked.Finally a finite element calculation model is used to simulate wear profiles in simple fretting and also in the presence of variable normal force. Only cases where the plan wears out (lithium-boron environment) have been simulated. In simple fretting, test simulation results are satisfactory. On the other hand, the non-superposition of the experimental and numerical profiles when the normal force fluctuates, confirms the presence of physical phenomena in the interface which are not yet represented in the numerical tool