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Söderberg, Jansson Marcus, and Oskar Lundkvist. "Property Optimization of PM-gearing." Thesis, KTH, Maskinkonstruktion (Inst.), 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-209549.
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The purpose of this bachelor thesis is to design and optimize a powder metal gear through FEM-analyzes. The moment of inertia and weight of the gear shall be reduced at the same time as the demands on tension and bending stiffness are met. The gear that is used as reference and will be optimized is the standard gear in the FZG-rig at the department of Machine Design at KTH. The work is initiated with a literary study. After that a CAD-model of the gear and its pinion is created in Solid Edge. Then the reference gear is analyzed in the FEM-program Ansys and control calculations are made according to standards and handbooks. Thereafter different geometry and density variations are made and tested. The tests are then compared to the reference gear. By varying the density of the gear and varying the geometry of the waist of the gear several different optimization proposals could be made. By cutting material off the waist of the gear the weight can be reduced by 6 % with an increase in bending stress of 1 %. If a bigger increase in bending stress is allowed more material can be removed. If the bending stress increase is allowed to be 5 % a decrease in weight and moment of inertia of 14 % is obtained. With an increase in deformation of 5 % a decrease of 11 % in weight and moment of inertia was obtained. The different tested geometries behave relatively equal up to a 3 % decrease in weight with respect to deformation but begins to vary considerably if the weight is further decreased. Removal of material should be symmetric around every gear tooth to avoid transmission failure which also leads to increased noise. The results show that it is better to remove material under each gear tooth rather than under the root. It is also advantageous to remove material close to the flange. Further work is required to analyze and optimize the gears even more. Fatigue tests as well as different load cases should be analyzed.<br>Syftet med kanditatexamensarbetet är att ta fram och egenskapsoptimera ett pulvermetallurgiskt kugghjul med hjälp av FEM-analyser. Tröghetsmomentet och vikten på kugghjulet ska minimeras samtidigt som kraven på spänningar och böjstyvhet uppfylls. Det kugghjul som används som referens och ska optimeras är standardkugghjulet i FZG-riggen på institutionen för maskinkonstruktion på KTH. Arbetet inleds med att en litteraturstudie görs. Sedan tas en CAD-modell för kugghjulet och dess tillhörande drev fram i Solid Edge. Därefter analyseras referenskugghjulet i FEM-programmet Ansys och kontrollberäkningar görs enligt standarder och handböcker. Därefter konstrueras och analyseras olika geometrier och densitetsvariationer och jämförs med referenskugghjulet. Genom att variera densiteten på kugghjulet och variera geometrin på kugghjulets liv kunde flertalet optimeringsförslag tas fram. Genom att göra en utskärning i livet kan vikten minskas med 6 % utan att böjspänningen påverkas mer än 1 %. Om en större ökning i böjspänning tillåts kan ytterligare material avlägsnas. Om böjspänningsökningen tillåts vara ca 5 % kan en viktminskning och tröghetsmomentsminskning på ca 14 % åstadkommas. Vid en deformationsökning på 5 % erhölls en viktminskning och tröghetsmomentsminskning på ca 11 %. De olika geometrier som testas beter sig relativt lika upp till 3 % viktminskning med avseende på deformation och börjar därefter variera kraftigt. Borttagning av material måste ske symmetriskt kring varje kuggtand för att transmissionsfel och därmed ökat buller ska undvikas. Det visar sig att ta bort material under kuggen är bättre än att ta bort material under kuggroten. Det gynnsamt att göra geometriska förändringar närmast flänsen på kugghjulet. Vidare arbete krävs för att analysera och optimera kugghjulen ytterligare. Utmattningstester och fler lastfall bör analyseras.
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Ding, Huali. "Dynamic wear models for gear systems." Columbus, Ohio : Ohio State University, 2007. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1194025602.
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Daros, Pinto Matheus. "Muscle gearing during eccentric contractions in vivo." Thesis, Edith Cowan University, Research Online, Perth, Western Australia, 2024. https://ro.ecu.edu.au/theses/2876.
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Daily and sports activities often involve eccentric contractions when the load acting on a muscle is greater than its force production, in which case the muscles actively lengthen to absorb or dissipate mechanical energy. In pennate muscles, fascicles change both length and angle as the muscle lengthens. The fascicle rotation reduces the amount of fascicle lengthening for a given muscle length change and allows (i) fibres and fascicles to work more optimally within their length−tension and force−velocity relations, and (ii) the muscle to operate over a broader range of lengths than when rotation is absent. The effect of fascicle rotation on muscle and fascicle length changes can be characterised by a muscle gear ratio: Δ muscle length/Δ fascicle length. Muscles that operate in high gear are potentially at lower risk of strain-related damage and injury. However, despite the functional importance of fibre rotation and gearing during eccentric contractions, most of our understanding of how fascicles and muscles behave comes from studies of animal or human muscles during concentric or isometric contractions. Relatively little is known about how muscles behave, and the factors affecting their optimal function, under eccentric conditions in vivo.
This thesis consists of four studies. The first study (Chapter 2) is a comprehensive review of the literature defining muscle gearing and its functional importance and reviewing the factors influencing muscle gear changes under varying contractile conditions. Fundamental factors identified, primarily from isolated muscle experiments and mathematical modelling, include initial pennation angle, fascicle vectorial forces, extracellular matrix properties, and fluid and associated intra- and extra-muscular pressures. The findings revealed that muscle gear typically decreases with contractile force in isolated muscle preparations but either decreased or remained unchanged in vivo. These differences may be related to the presence of in-series elastic tissues (e.g., tendons) and the influence of lateral pressures exerted within synergistic muscle groups, which may affect shape changes in muscles operating in vivo. The lack of information on muscle gearing during eccentric contractions in vivo prompted the subsequent experiments conducted in this thesis.
Study 2 (Chapter 3) presents a hybrid structure in which inconsistencies in nomenclature, mathematical computation methodologies, and the anatomical inputs used to calculate muscle gear are reviewed. Then, muscle and fascicle behaviour data collected from medial gastrocnemius during passive and maximal eccentric contractions were examined to reveal significant effects of the anatomical inputs and muscle gear calculation methods. Differences in muscle gear were present when contrasting the use of the muscle segment vs. the whole muscle length changes in the calculation, with differences being particularly evident during active versus passive muscle lengthening.
Data collected in the third study (Chapter 4) showed that muscle gear increased with eccentric contraction intensity and decreased with muscle length, i.e., fascicle behaviour and muscle gear were muscle length- and torque-dependent. Additionally, the data showed that initial pennation angle, rather than the magnitude of fascicle rotation, was the primary factor explaining length- and torque-dependent gear changes under the current experimental conditions.
The final study (Chapter 5) revealed that muscle and fascicle behaviours during submaximal eccentric contractions were unchanged after the performance of maximal concentric (i.e., non-damaging) plantar flexor contractions that promoted significant functional fatigue, i.e., loss in concentric force and plantar flexor activation. This suggests that changes in muscle shape during the submaximal eccentric contractions were relatively unaffected, which may help the muscle retain function in the face of fatigue.
The findings of the present research improve our understanding of muscle and fascicle mechanics in vivo during eccentric contractions in humans, providing evidence that contractile force influences architectural behaviour and muscle gearing of the human medial gastrocnemius in a way that differs from isolated muscle preparations, and that concentric‑induced muscle fatigue has little influence on the muscle mechanics during submaximal eccentric contractions. Further questions are also raised, which should be examined in future studies.
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Petry-Johnson, Travis T. "Experimental investigation of spur gear efficiency." Connect to resource, 2007. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1209585550.
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Hu, Jun. "The kinematic analysis and metrology of cylindrical worm gearing." Thesis, University of Newcastle Upon Tyne, 1997. http://hdl.handle.net/10443/807.
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Worm gearing is very widely used, especially in heavy industry, but due to the complexity of worm gear geometry, worm gear research has lagged behind that for spur and helical gears. In the last decade, however, the potential for significant improvement in worm gearing has dramatically increased: computers have given greater freedom to analyse worm gearing; CNC machines make it possible to aim for optimised worm gear geometries with very high accuracy and the development of synthetic lubricants has substantially improved lubrication conditions. In the UK, over the last few years, research effort in the field of worm gearing has increased considerably. As a part of this recent activity in the UK, the author has been involved mainly in developing the analytical mechanics and metrology of worm gears. A method for the generalised 3D non-elastic worm gear mesh analysis and associated software have been developed and worm wheel metrology software has been implemented on a CNC measuring machine in the UK National Gear Metrology Laboratory, to allow, for the first time, analytical measurement of worm wheel tooth flanks. Combination of the mesh analysis software and CNC measurement of worm wheels has assisted in the design and manufacture of worm gears with modified tooth profiles. Two methods of 3D non-elastic worm gear analysis have been developed for conjugate action and non-conjugate action respectively. The conjugate analysis determines the lines of contact, sliding and rolling velocities, limitations of the working area (the envelope of contact lines on a worm surface and singularities on a wheel surface), principal relative curvatures and the orientations of contact lines. It is based on the B-matrix method [Zhang and Hu, 1989]. The non-conjugate analysis predicts entry and exit gaps, contact ratio, wear marking on the worm flank, instantaneous contact topology on all the engaged tooth flanks, total contact area, contact pattern and transmission error. This is based on numerical simulation of the actual worm gear running process under no-load. Although the non-elastic analysis models have been designed for any type of worm gearing, and have been used to study Cavex (ZC) wormgears and the meshing of a ZA Abstract worm with a helical gear, most of the work has been on involute (ZI) worm gearing, since this is, by far, the most commonly produced type in the UK. This thesis presents the work as follows: 1) The development of the B-Matrix kinematic method for conjugate analysis. The B-Matrix method, presented in chapter 2, elegantly simplifies the derivation and calculation procedures, since the geometric parameters and the motional parameters can be arranged in separate matrices. As a result, the models can be applied to different geometries and coordinate systems with no need for further difficult derivations. The method leads to an easier way of integrating the theory of various types of worm gearing into compact generalised models. It is much more convenient and reliable to let the computer formulate and solve matrix equations numerically, treating each matrix as a simple variable, than to develop analytically the corresponding long tedious non-linear equations. 2) The development of mathematical equations to allow CNC measuring machines to measure cylindrical worm wheels with respect to their mating worms. The measurements are 3-dimensional and absolute, in the sense that the results are the deviations from the theoretical geometries rather than comparative measurements relative to a (necessarily imperfect) master worm wheel. The measurement theory has been implemented on a particular CNC measuring machine. This is presented in chapters 3 and 5. 3) The development of the non-conjugate analysis. The fundamental basis of the non-conjugate analysis presented in this thesis is to rotate the worm wheel to bring its tooth flank into contact with the worm flank at each given angle of worm rotation, so that the no-load transmission error and gap contours can be determined. This method is suitable for both cylindrical and globoidal worm gears, since the rotation angles of worm and wheel are used to simulate the running process directly. Abstract The method also allows the wheel tooth flank to be obtained either by conjugate analysis of the hobbing process, or by analytical measurements or other methods (for example, when a theoretically-generated involute helical gear is used to mesh with a worm). This work is presented in chapter 4. 4) implementation of the non-elastic analysis theory. The non-elastic analysis software has been written for personal computers. In addition, dimensional calculations specified by BS 721 and commonly used hob design methods have been added to the non-elastic analysis software to increase user-friendliness. The software has been used to investigate the effects on the worm gear contact and performance of machining errors and profile deviations or modifications. The structure of this analysis software allows for the inclusion of new modules for other types of worm gearing without in any way disturbing the integrity of the program's existing abilities. The non-elastic analysis software is user-friendly with a "Windows" graphical user interface. Software reliability and error tolerance have been of particular concern during program development. This work is presented in chapter 5. 5) The software has been thoroughly validated against other published results and/or actual production. The software has been used extensively for both research and commercial purposes, and the user interface developed further in response to user feedback. Examples of these applications are given in chapter 7.
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Bajer, Andrzej. "Parallel finite element simulator of planetary gear trains." Access restricted to users with UT Austin EID Full text (PDF) from UMI/Dissertation Abstracts International, 2001. http://wwwlib.umi.com/cr/utexas/fullcit?p3032969.
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Kendrick, Allen E. "Defect characterization in cast steel ball mill ring gears." Thesis, McGill University, 1987. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=66196.
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Elyurek, Mehmet. "Establishing a vibration threshold value, which ensures a negligible false alarm rate for each gear in CH-53 aircraft using the operational data." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2003. http://library.nps.navy.mil/uhtbin/hyperion-image/03Dec%5FElyurek.pdf.
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Thesis (M.S. in Operations Research)--Naval Postgraduate School, December 2003.<br>Thesis advisor(s): Samuel E. Buttrey, Robert Koyak. Includes bibliographical references (p. 77-78). Also available online.
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Yildirim, Nihat. "Theoretical and experimental research in high contact ratio spur gearing." Thesis, University of Huddersfield, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.307840.
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Dearn, Karl David. "An investigation into tribological and performance related aspects polymeric gearing." Thesis, University of Birmingham, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.532276.
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The benefits of using polymer and polymer composite gears are numerous and it is these in part that is fuelling the resurgent commercial interest in them for metal replacement applications, thought to be in the region of £160M per annum. This interest is further driven by the increasingly important need for considerate energy consumption and the drive for greater product efficiency. As the science and technology associated with polymeric gearing develops, so too do the complexities and demands of the application. Although traditionally employed in low load and speed applications and motion control, such advancements are pushing the limits of high performance polymer applications to unprecedented levels where hitherto high temperature and corrosive environments would have excluded them. Thus, the complex kinematics of gearing and the extreme environments in which polymer gears operate make such applications ideal candidates for material manufacturers to demonstrate the superiority of their proprietary polymers. Despite this resurgent interest, polymer gears have received only a fraction of the attention received by their metal counterparts. As a result, those choosing to specify polymers in demanding applications are faced with a lack of reliable design and testing data, with current standards and guidelines based on metallic dogma. Given the fundamental differences between the two materials, this has been proved to be inadequate. This thesis aimed to address a variety of performance aspects of polymeric gears, particularly focusing on temperature and tribological related effects. At its foundation was the previous research conducted by the Power Transmission Laboratory, at the University of Birmingham. Five research areas were covered, they were: - The analysis and estimation of bulk temperatures in polymer spur gears - Contact analysis of polymeric gears - Acoustic emissions and transmission error analysis: - External lubrication analysis with respect to measured efficiencies and surface damage: -A design and rating algorithm for polymeric gears: The research utilised empirical, numerical and analytical techniques to improve the understanding of the behaviour of polymeric gears, such that their performance and reliability could be improved. In addition to this, recommendations were given for future research directions.
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Killeen, Michael. "Experimental and mathematical investigation into aspects of spatial involute gearing." Thesis, View thesis, 2005. http://handle.uws.edu.au:8081/1959.7/20408.
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This thesis is a small part of a much larger work, the aim of which is to continue the transition from gear theory to gear practice. The thesis deals with some aspects of the testing and theoretical development of equiangular and plain polyangular gears respectively. Initial prototypes of the equiangular spatial involute gearing, a small subset of a general spatial involute gear set, developed in previous works are to be tested for both function and form. The tests, based on the principles of the single flank gear tester, investigate constancy of transmission ratio and use both electronic and mechanical means. The former of these highlights the shortcomings of some aspects of the experimental set up. Algebraic expressions are also developed for plain polyangular gearing, a more general form of spatial involute gearing. These equations demonstrate the links to the underlying kinematic principles and are, consequently, more robust. This is verified by their application to both the equiangular and plain polyangular cases. The expressions were checked by comparing their results to graphical and numerical models developed concurrently with the algebraic expressions. Initial investigations are also undertaken into turning the mathematical theory into gear machining theory.
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Killeen, Michael. "Experimental and mathematical investigation into aspects of spatial involute gearing." View thesis, 2005. http://library.uws.edu.au/adt-NUWS/public/adt-NUWS20051102.111626/index.html.
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Gustavsson, Mårdestam Peter, and Adam Lundin. "Efficiency Analysis of a Planetary Gearbox." Thesis, Linköpings universitet, Maskinkonstruktion, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-65578.
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This Bachelor of Science thesis consists of an efficiency evaluation and creation of atheoretical model for an Atlas Copcos epicyclic gearbox. The thesis starts with atheoretical chapter containing the fundamentals of epicyclic gearing and the build of thespecific gearbox investigated. The following chapter contains former testing and theoryof power losses in a gearbox. After the theory is explained the next chapter containstesting, compromises and assumptions during testing and also results from the testing.The next chapter explains the Matlab calculation program based on the theory andmeasurements. Finally the model is validated against reference a reference model andagainst real gearbox measurements followed by some closing conclusions. The finalmodel calculates the efficiency rather well and has a linear difference. The difference isstatic since some losses have been left out, it can be fixed with an empirical correctionfactor which corrects the values and predicts an acceptable efficiency. The correctionfactor for the surface roughness also decreases the difference.
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Lin, Juhn-Shyue. "Experimental analysis of dynamic force transmissibility through bearings." Connect to resource, 1989. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1207597697.
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Jian, Linni, and 蹇林旎. "Design, analysis and application of coaxial magnetic gears." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2010. http://hub.hku.hk/bib/B44897558.
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Hochmann, David. "Friction force excitations in spur and helical involute parallel axis gearing /." The Ohio State University, 1997. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487948158628115.
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Houghton, Brian K. "Gearing up and getting there : improving local response to chemical terrorism /." Santa Monica, CA : Pardee RAND Graduate School, 2004. http://bibpurl.oclc.org/web/14262.
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Hurrell, Michael J. "Shroud Effects on Load-independent Power Loss of High-speed Rotorcraft Gearing." Cleveland State University / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=csu1588885945866605.
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Chase, David Roger. "Development of an efficiency test methodology for high-speed gearboxes." Connect to resource, 2005. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1209661381.
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Cook, Nathan Lindquist. "Investigation of vibration control of hypotrochoidally driven machninery." Thesis, Georgia Institute of Technology, 2002. http://hdl.handle.net/1853/17391.
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Palmer, David. "The effects of profile relief on narrow face width parallel axis gears." Thesis, University of Huddersfield, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.342563.
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The well established practice of applying tip and/or root relief to the teeth of low contact ratio spur gears is reviewed. Results are presented for the experimental validation of a systematic design method for profile relief that depends critically on how far the relief extends along the path of contact. This method has proved to be effective in controlling gear vibration and noise. A good correlation between static transmission error, dynamic transmission error and sound pressure level was found. This allows design rules to be formulated which can be applied to achieve the minimum vibration and noise levels at a given operating load. A computer program was also developed that allows the introduction of measured gear tooth profiles from an involute tester, to predict the static transmission error curves and thus give an indication of gear quality as regards vibration and noise levels for any given simulated operating load or load range. The computer program was extended to take into consideration the more complex geometry of helical gears using the 'Thin Slice' theory. This allows the prediction of the effects of lead crowning, misalignment, pitch errors and various profile reliefs including relief coined "cross relief", where the relief is applied parallel to the base helix angle. An optimisation routine was included in the computer program that systematically varies the extent of profile relief and amount of lead crowning to minimise transmission error. Since the amount of required profile relief is concomitant with extent of relief and amount of lead crowning (load remaining constant), the program iterates to find the correct amount of profile relief to avoid undesirable comer/tip contact. This new approach has facilitated the generalisation of the effects of profile relief on transmission error for a whole range of typical axial and transverse contact ratios for narrow face width helical gears, previous analyses concentrating on specific designs. Results are also presented for the experimental validation of predicted static transmission error in helical gears. A good correlation between static transmission error, dynamic transmission error and sound pressure level was found as in the spur gear analysis.
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Yang, Feng. "Numerical analysis and three dimensional modelling of worm gearing with localised tooth contact." Thesis, University of Exeter, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.302638.
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Song, Guangming. "An application of computer aided design and computer aided draughting techniques to gearing." Thesis, City, University of London, 1988. http://openaccess.city.ac.uk/19505/.
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The thesis describes the development of a computer-aided design and computer-aided draughting package of industrial gearboxes for transmitting power between shafts having parallel major axes. The package mainly consists of the following functions: (a) Determination of gear tooth numbers from the properties of continued and conjugate fractions (b) Generation of gear teeth by a rack-type cutter (c) Calculation of gear tooth profile and production of gear tooth grid for finite element stress analysis (d) Detailed strength analysis and design of a spur or helical, external or internal, standard or modified, single- or double- reduction gear set based on the ISO gear standards (e) Shaft design and analysis (f) Bearing selection and analysis (g) Production of the working drawings of the main gearbox components. This package works on the IBM PC and its compatible machines, operates in an interactive mode, combines the experience of the designer with the power of the computer, and produces substantial savings in time and cost over conventional design methods. Design examples illustrating this package are given. In addition, the maximum tooth root bending stresses have been studied by using finite element techniques and the results have been compared with those using the ISO gear standards.
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Wang, Jiande. "Numerical and Experimental Analysis of Spur Gears in Mesh." Thesis, Curtin University, 2003. http://hdl.handle.net/20.500.11937/879.
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The investigation of numerical methods for modelling the mechanism properties of involute spur gears in mesh, over the mesh cycle, forms the major part of this thesis. Gearing is perhaps one of the most critical components in power transmission systems and the transmission error of gears in mesh is considered to be one of the main causes of gear noise and vibration. Numerous papers have been published on gear transmission error measurement and many investigations have been devoted to gear vibration analysis. There still, however, remains to be developed a general Finite Element Model capable of predicting the effect of variations in rigid body gear tooth position, in which the critical stage is the prediction of gear behaviour with profile modifications (including tip-relief).In this thesis, FEA results have been obtained by using various techniques including: (a) adaptive re-mesh with contacts using quad (2D) and brick (3D) elements and (b) the element birth and death option. Tooth profile modifications can affect the behaviour of the gear meshing including the T.E., ratio of local deformation and load-sharing ratio results, etc, providing an alternative method for gear design. In the high order end, the elastic strains of the gear-shaft system have also been investigated. The results in this thesis have shown the potential for using strain-vibration relationships to monitor or control the transmission system. The investigations have also included some analysis with non-metallic gears, an application area that is rapidly growing. The results achieved here are at a fundamental stage, and further research would necessitate applying a coupled field analysis (structural and thermal).
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Milkovic, Petar. "Analysis and Design of a Flexible Tooth Gear." [Milwaukee, Wis.] : e-Publications@Marquette, 2009. http://epublications.marquette.edu/dissertations_mu/20.
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Thesis (Ph. D.)--Marquette University, 2009.<br>Access available to Marquette University only. Available for download on June 17, 2010. Robert J. Stango, Nicholas J. Nigro, Stephen Heinrich, Vikram Cariapa, Shuguang Huang, Advisors.
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Курочкін, Валерій Борисович, Валерий Борисович Курочкин, Valerii Borysovych Kurochkin, К. В. Гудимова та А. Н. Демченко. "Определение модулей зубчатых передач двухступенчатого цилиндрического соосного редуктора". Thesis, Издательство СумГУ, 2012. http://essuir.sumdu.edu.ua/handle/123456789/25844.
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Vijayakar, Sandeep M. "Finite element methods for quasi-prismatic bodies with application to gears /." The Ohio State University, 1987. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487335992904337.
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Haji, Bungsu Hajah Jabaidah. "Investigating threshold concepts in the learning of agriculture : gearing towards quality and relevant curriculum innovation." Thesis, University of Newcastle upon Tyne, 2014. http://hdl.handle.net/10443/2761.
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Agricultural education in Brunei Darussalam is torn between apparently conflicting patterns. There seems to be an economic agenda where policy makers attempt to make educational outcomes match national priorities. Worldwide, agriculture is being confronted by a globalised economy and market reforms. However, agriculture as a subject in schools is also confronting the issues of quality education. Quality education is the number one goal of Brunei’s national education system; but how do we address quality in learning, in a prescribed curriculum? In pursuit of that quality, this study explores what concepts in agriculture learning lead to higher levels of understanding, is there progression, and how do students arrive at their understanding? This multicase study draws on data from secondary education students studying agriculture during 2009 – 2010. It uses the threshold concepts framework as an analytical tool for understanding students’ learning and for exploring their personal experiences (and insights into their phenomenological reflections) based on interview data (n=7) and questionnaires (N=19), corroborated/triangulated by teachers’ data (questionnaires n=14, interviews n=2) and other documents to inform future curriculum innovation. The methodological approach is phenomenological, interpretive, descriptive and qualitative, using four stages of Interpretative Phenomenological Analysis (IPA) supplemented with some quantitative analysis. The threshold concept constituents that were discovered are very diverse, ranging from skills, science, business, research and management; but planting is the key. Eleven super-ordinate themes illuminated two stages of threshold understanding: planting and plant science at the crop production level; and research, business and management at the commercial level. The findings showed the importance of phenomenological experiences: feelings associated with sweat, yields and money generation, emanated from a sense of agency and affective labour, paving the way to power of purpose towards self and socio-economy. Understanding the importance and merits of their learning activities made students reflected their meaning and positive feelings about themselves and self-worth. This motivated them to achieve further learning goals. iii Agricultural learning transformation seems to come through a combination of knowledge-based understanding in plants, and how they grow, alongside the experience of planting and growing crops successfully. Importantly, it is not just the knowledge about planting that the students get from the experience, but it is the feelings (emotion) that seemed to emerge from their words of sweating under the sun that helps to consolidate that knowledge into something which becomes part of their identity. This study’s findings about lower level agriculture learning seem to leverage on experiences to create bigger learning outcomes prior to mastery in the discipline. Transformative learning occurred when learners studied through situated contextual experiential activities, providing affective embodiment and thinking like agriculturists. Thus agricultural understanding and transformation was triggered by experiential threshold concepts whose foundations arise from integration of personal, emotional affective feelings and everyday experiences with ideas from discipline. Emotional feelings (associated with phenomenal experiences) provide an added dimension to the ‘basic threshold concept’ work by Davies and Mangan (2008:39), ‘where newly met concepts some of which transform understanding of everyday experience through integration of personal experience with ideas from discipline’. These results reveal a new perspective on threshold concepts work, particularly relevant to disciplines involving process skills and experiences, especially for agriculture. The findings serve as key indicators to progression and quality learning outcomes. They also offer useful implications for a quality curriculum in agriculture which fosters personal identity transformation, so more students become future agriculturists and thereby will help the economy. Of foremost importance is to include, in the curriculum, the key threshold concepts capable of transforming understanding and how to teach these concepts through meaningful/engaging experiences (via practicality and doing project-evidence/outcome-based learning), and provision of connections and relationships. The key to quality in the agriculture curriculum is therefore, how to translate and teach these concepts into meaningful affective learning experiences.
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DeCaires, Brian J. "Variation analysis of involute spline tooth contact /." Diss., CLICK HERE for online access, 2006. http://contentdm.lib.byu.edu/ETD/image/etd1176.pdf.
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Irwin, Gary M. "Interactive 3-D computer-aided design of external spur gears cut by a hob." Thesis, Virginia Polytechnic Institute and State University, 1986. http://hdl.handle.net/10919/90943.
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An interactive program is presented which enhances the design of external spur gears cut by a hob. The program code calculates the geometry of an involute spur gear with trochoidal fillets and then uses the Graphical Kernel System (GKS), CADAM, and MOVIE.BYU to represent and display the gear. GKS, an international standard, is used to represent the gear in two dimensions; while the CAD/CAM system CADAM and the software package MOVIE.BYU accurately create wireframe geometric design models in three dimensions. Examples of the input parameters needed and each of the software packages in use are shown and explained.<br>M.S.
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Bahrami, Kouhshahi Mojtaba. "Design and Performance Evaluation of Linear and Axial-Flux Magnetic Gears." PDXScholar, 2019. https://pdxscholar.library.pdx.edu/open_access_etds/4983.
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The conversion from low speed to high speed and vice versa in various forms, including rotary and linear motion, is a requirement for a wide range of applications. For example, wind power generation requires a conversion of low speed rotation of turbine blades to high speed generator rotation, and ocean wave power generation is achievable by conversion of low speed linear motion to either high speed rotation or high speed linear motion. Mechanical gearboxes, hydraulic and pneumatic actuators are commonly used to achieve these conversions. However, these systems suffer from reliability issues, high maintenance requirements, noise, and lack of overload protection.
As an alternative, electromagnetic actuators overcome most of the issues related to the mechanical, hydraulic and pneumatic mechanisms. However, magnetic shear stress is constraint by current density and magnetic saturation. Recently, magnetic gearboxes have been proposed, which rely only on magnetic loading. They provide speed and force conversion like their mechanical counterparts, but without thermal constraints (current density limits). Unlike mechanical gears, magnetic gear contact-less operation enables it to operate without lubrication and with low noise, and higher efficiency. Its reliance on magnetic loading also provides overload protection.
This dissertation focuses on investigating two new types of magnetic gears; first a magnetically-geared lead screw is proposed, which converts a low speed linear motion to a high speed rotary motion. The proposed actuator is a combination of two previously proposed actuators, the linear magnetic gear and the magnetic lead screw. Unlike these two topologies, the translator part of the proposed magnetically geared lead screw is made entirely of low-cost ferromagnetic steel. Therefore, the translator stroke length can be long without requiring more magnet material.
In the second part of this dissertation, an axial flux magnetic gear is proposed that has an integrated outer stator. This axial flux magnetically-geared motor is unique in that the stator shares the high-speed rotor with the magnetic gear, so there is no need for a separate rotor. The high speed and low speed rotors use a flux-focusing typology. The stator is mounted outside the axial flux magnetic gear. This makes the design mechanically less complex. It also enables the stator to be cooled more easily.
In the last part of this dissertation, analytical-based models are proposed for a linear permanent magnet coupling and magnetic lead screw. These models help to find the upper bound of the similar devices, which require a scaling analysis. Numerical methods like finite element analysis are accurate and effective enough for modeling various electromechanical and electromagnetic devices. However, these simulations are usually computationally expensive; they require a considerable amount of memory and time, especially when considering 3D finite element simulation. The proposed analytical models offer exact field solution while significantly reducing the computational time.
Detailed analysis of two magnetic gears is given under their corresponding chapters. Preliminary experimental results are also provided. The analytical-based model is presented and verified by FEA results. A summary of research contributions and future works is outlined.
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Hamadi, Hassan. "The measurement of financial performance and its effect on the relationship between gearing and over-investment." Thesis, University of Surrey, 2005. http://epubs.surrey.ac.uk/857/.
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Jain, Sharad. "Skidding and fault detection in the bearings of wind-turbine gearboxes." Thesis, University of Cambridge, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.608104.
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Sherwood, Norman Keith. "Open gear lubrication." Thesis, Queensland University of Technology, 1999.
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Benn, Colin. "The application of an elastohydrodynamic lubrication (EHL) model to open gates." Thesis, Queensland University of Technology, 1994.
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Liu, Gang. "Nonlinear dynamics of multi-mesh gear systems." Columbus, Ohio : Ohio State University, 2007. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1196222009.
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Schön, Peter Paul. "Unconditionally convergent time domain adaptive and time-frequency techniques for epicyclic gearbox vibration." Pretoria : [s.n.], 2005. http://upetd.up.ac.za/thesis/available/etd-08282007-142010.
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Al-fozan, Adel. "3-D simulation and optimization of forging of a complex bevel gear using the finite element method." Ohio : Ohio University, 1998. http://www.ohiolink.edu/etd/view.cgi?ohiou1177006776.
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Wang, Jiande. "Numerical and Experimental Analysis of Spur Gears in Mesh." Curtin University of Technology, Department of Mechanical Engineering, 2003. http://espace.library.curtin.edu.au:80/R/?func=dbin-jump-full&object_id=14464.
Full textAbstract:
The investigation of numerical methods for modelling the mechanism properties ofinvolute spur gears in mesh, over the mesh cycle, forms the major part of this thesis.Gearing is perhaps one of the most critical components in power transmission systemsand the transmission error of gears in mesh is considered to be one of the main causes ofgear noise and vibration. Numerous papers have been published on gear transmissionerror measurement and many investigations have been devoted to gear vibration analysis.There still, however, remains to be developed a general Finite Element Model capable ofpredicting the effect of variations in rigid body gear tooth position, in which the criticalstage is the prediction of gear behaviour with profile modifications (including tip-relief).In this thesis, FEA results have been obtained by using various techniques including: (a)adaptive re-mesh with contacts using quad (2D) and brick (3D) elements and (b) theelement birth and death option. Tooth profile modifications can affect the behaviour ofthe gear meshing including the T.E., ratio of local deformation and load-sharing ratioresults, etc, providing an alternative method for gear design. In the high order end, theelastic strains of the gear-shaft system have also been investigated. The results in thisthesis have shown the potential for using strain-vibration relationships to monitor orcontrol the transmission system.The investigations have also included some analysis with non-metallic gears, anapplication area that is rapidly growing. The results achieved here are at a fundamentalstage, and further research would necessitate applying a coupled field analysis (structuraland thermal).
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Switzer, Earl, Michael Whelan, and Farncisco Lagunas. "AIR TRAFFIC CONTROL COMMUNICATIONS TEST FACILITY AND AVIONICS SYSTEM TEST (ACTFAST): GEARING UP FOR NEXT GENERATION AVIONICS SYSTEMS TESTING." International Foundation for Telemetering, 2000. http://hdl.handle.net/10150/608285.
Full textAbstract:
International Telemetering Conference Proceedings / October 23-26, 2000 / Town & Country Hotel and Conference Center, San Diego, California<br>Growth in civil aviation is overwhelming worldwide airspace and air traffic services. The International Civil Aviation Organization (ICAO), Federal Aviation Administration (FAA) and Department of Defense (DoD) are proposing or implementing numerous changes to address this growth. The changes are broadly contained in what the civil aviation community calls Communication, Navigation, and Surveillance/Air Traffic Management (CNS/ATM) and the DoD calls Global Air Traffic Management (GATM). A major component of both civil and DoD proposed changes are data link systems digitally transmitting information between aircraft, air traffic control centers, and aircraft operations centers. The real-time interactive nature of these data-link systems and the integration of the aircraft avionics into a worldwide network are forcing aircraft test agencies to acquire access to this capability. Aircraft flighttesting must address both the specific aircraft avionics test requirements and the system-of-systems aspects of data-link applications. This paper describes the factors driving changes in the worldwide CNS/ATM system and identifies specific proposed or implemented changes. Various flight-test requirements, both civil and military, of the proposed changes are enumerated. Particular attention is paid to the DoDs GATM certification requirements. Finally, we present the Air Traffic Control Communications Test Facility and Avionics System Test (ACTFAST) program and explain its capabilities. Rationale for ACTFAST component parts is included along with a brief outline of how the capabilities represented by each component part are used during flight test to acquire the necessary information to meet civil and DoD aircraft certification requirements.
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Forrester, B. David, and David Forrester@dsto defence gov au. "Advanced vibration analysis techniques for fault detection and diagnosis in geared transmission systems." Swinburne University of Technology, 1996. http://adt.lib.swin.edu.au./public/adt-VSWT20050715.092623.
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The primary objective of the research reported in this thesis was the improvement of safety in helicopters by identifying and, where necessary, developing vibration analysis techniques for the detection and diagnosis of safety critical faults in helicopter transmission systems. A review and, where necessary, expansion of past research is made into (a) the mechanisms involved in the production of vibrations in mechanical systems, (b) the failure modes experienced in geared transmission systems, (c) which failure modes are critical to the safety of helicopters, (d) how the safety critical failure modes affect the vibration signature, and
e) the vibration analysis techniques currently used to detect safety critical failures. The effectiveness of the currently available vibration analysis techniques is investigated
using in-flight vibration data from Royal Australian Navy helicopters and seeded fault
data from a purpose built spur gear test rig.
Detailed analysis of techniques for synchronous signal averaging of gear vibration data is
undertaken, which includes the development of new methods of modelling and quantifying the effects of synchronous averaging on non-synchronous vibration. A study of digital resampling techniques is also made, including the development of two new methods which provide greater accuracy and/or efficiency (in computation) over previous methods. A new approach to fault diagnosis is proposed based on time-frequency signal analysis techniques. It is shown that these methods can provide significant improvement in diagnostic capabilities over existing vibration analysis techniques. Some limitations of general time-frequency analysis techniques are identified and a new technique is developed which overcomes these limitations. It is shown that the new technique provides a significant improvement in the concentration of energy about the instantaneous frequency of the individual components in the vibration signal, which allows the tracking of small short term amplitude and frequency modulations with a high
degree of accuracy. The new technique has the capability of 'zooming' in on features which may span only a small frequency range, providing an enhanced visual representation of the underlying structure of the signal.
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Feng, Ming-Fa. "A finite element study of bending stress variation in meshed spur gear pairs." Thesis, Virginia Polytechnic Institute and State University, 1987. http://hdl.handle.net/10919/87645.
Full textAbstract:
A study of the bending stresses in a pair of meshed spur gears using the finite element method is presented. The models analyzed were in the shape of a circular gear with five teeth or a five-tooth rack. A unit torque (1 lbf-ft) was applied as the form of nodal forces on the nodes around the bore hole of the driver pinion. The nodes around the bore hole of the driven gear (or the nodes along the back of the driven rack) were fixed. In order to transmit the power from the driver pinion to the driven gear (or rack), the points in contact were made coincident.
Seven model groups with same diametral pitch (1.0), addendum (1.0 in.), dedendum (1.3 in.), pressure angle (20°) and hob tip radius (0.35 in.) but with varying numbers of teeth on the pinion and gear were analyzed to compute the tensile stress variation in the root fillet during the duration of contact. A model for predicting the tensile stress variation at the root fillet during the duration of contact has been created.
The results were compared with AGMA and other results with agreement for the peak within 3%.<br>M.S.
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Andersen, Brian S. "An Investigation of a Positive Engagement, Continuously Variable Transmission." Diss., CLICK HERE for online access, 2007. http://contentdm.lib.byu.edu/ETD/image/etd1878.pdf.
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Kumar, Naren. "Investigation of drive-train dynamics of mechanical transmissions incorporating cycloidal drives." Thesis, Queensland University of Technology, 2015. https://eprints.qut.edu.au/84752/8/Naren%20Kumar%20Thesis.pdf.
Full textAbstract:
Cycloidal drives are compact, high-ratio gear transmission systems used in a wide range of mechanical applications from conveyor drives to articulated robots. This research hypothesises that these drives can be successfully applied in dynamic loading situations and thereby focuses on the understanding of differences between static and dynamic loading conditions where load varies with time. New methods of studying the behaviour of these drives under static and dynamic loading circumstances were developed, leading to novel understanding and knowledge. A new model was developed to facilitate research and development on Cycloidal drives with potential benefits for manufacturing, robotics and mechanical-process-industries worldwide.
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Kahimise, Robert N. "Black economic empowerment : looking at ROE, ROA, P/E and gearing of companies listed on JSE from Impumelelo edition (2000.2001) : comparative financial analysis." Thesis, Stellenbosch : Stellenbosch University, 2003. http://hdl.handle.net/10019.1/53313.
Full textAbstract:
Thesis (MBA)--Stellenbosch University, 2003.<br>ENGLISH ABSTRACT: This empirical study was aimed at analysing the financial performance of black economic
empowered companies, as selected per Impumelelo publication - 2000/1 edition. The Unit of
Analysis of this study is therefore the phenomenon commonly described as Black Economic
Empowerment, and in particular the financial performance of these business entities with
specific interest in the following ratios; ROE, ROA, PIE and DIE.
The fundamental problems analysed in this study are: Whether these Companies can
financially perform consistently, with specific reference to ROE (Management effectiveness)
and ROA (Company's efficiency); Whether these Companies utilised their capital efficiently -
Financial leverage; Whether is worth investing in any commercial bank or in black economic
empowerment Companies; Market perception of these Companies; Whether these
Companies are really highly geared; through a comparative study between Impumelelo
sample and similar white-owned companies, to assess the better performer on Management
effectiveness and Company efficiency. The purpose of this study was further to draw
appropriate empowerment strategies from the U.S.A, Malaysia and Brazil; contextualised
them into the South African situation.
The outcomes of these analysis revealed that black economic empowerment companies are
indeed highly geared than their white-counterparts, and due to this inherent risk
inconsistency in performance has been identified. Within the selected performance
categories only half of the sample is classified as good performers, eight percent as excellent
performers while profitability is maintained by seventy six percent of the companies. Over the
period reviewed more then ninety percent of these companies' consistently signalled wrong
perceptions to the market. On the comparative study, the Impumelelo sample
overwhelmingly outperformed the white-owned sample on ROE and ROA per sector.
Impumelelo sample revealed volatility in the returns comparing to low stable returns by the
white-owned sample.<br>AFRIKAANSE OPSOMMING: Die doel van hierdie empiriese studie was om die finansiële prestasie van swart ekonomiesbemagtigde
maatskappye, soos geselekteer deur Impumelelo - 2000/1 uitgawe, te analiseer.
Die onderwerp van hierdie studie is dus die verskynsel gewoonlik beskryf as Swart
Ekonomiese Bemagtiging, en in die besonder die finansiële prestasies van hierdie entiteite,
veral die volgende verhoudings (ratio's): Wins op Belegging, Wins op Bates, Prys/verdienste
en Skuld/ekwiteit.
Die fundamentele probleme wat hierdie studie analiseer is: Kan hierdie maatskappye
konsekwent finansieel presteer veral wat betref Bekwaamheid van Bestuur en Bekwaamheid
van die Maatskappy? Kan hierdie maatskappye hulle kapitaal effektief gebruik? (Finansiële
hefboming.) Is dit beter om in 'n handelsbank te belê of in swart ekonomies-bemagtigde
maatskappye? Wat is die mark persepsie van hierdie maatskappye? Maak hierdie
maatskappye werklik op grootskaal gebruik van hefboming? Hoe vergelyk hierdie
Impumelelo steekproef met soortgelyke maatskappye in wit besit, veral wat betref die
bedrewenheid van die bestuur en die effektiwiteit van die maatskappy? 'n Verdere doelwit
van hierdie studie is om toepaslike bemagtigings strategië van die VSA, Malaysië en Brasilië
te bestudeer in samehang met die Suid-Afrikaanse situasie.
Die uitslag van hierdie studie is dat swart ekonomies-bemagtigde maatskappye inderdaad
meer van hefboming gebruik maak as hulle wit eweknieë, en as 'n gevolg van hierdie
inherente risiko is hulle prestasies soms inkonsekwent. In die selekteerde prestasie
kategorië kon net die helfde van die steekproef geklassifiseer word as goeie presteerders en
agt persent as uitstaande presteerders. Ses-en-sewentig van die maatskappye toon 'n wins.
Gedurende die periode onder bespreking het meer as neëntig persent van hierdie
maatskappye aanhoudend verkeerde seine na die mark uitgestuur. In die vergelykende
studie het die Impumelelo steekproef oorweldigend die steekproef in wit besit verbygesteek
veral wat effektiwiteit betref per sektor. Die Impumelelo steekproef se wins is onbestendig in
vergelyking met die lae, stabiele wins van die steekproef in wit besit.
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Jackson, Robert Lee III. "An investigation of the wear and lubrication of a thrust washer system in an automatic transmission planetary gearset." Thesis, Georgia Institute of Technology, 2000. http://hdl.handle.net/1853/16853.
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Talbot, David C. "An Experimental and Theoretical Investigation of the Efficiency of Planetary Gear Sets." The Ohio State University, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=osu1330630066.
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Hwang, Jenq-Fong. "Advanced computer-aided design method on the stress analysis of internal spur gears." Connect to this title online, 1986. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1102453550.
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Prasannavenkatesan, Rajesh. "Microstructure-sensitive fatigue modeling of heat treated and shot peened martensitic gear steels." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/31713.
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Thesis (Ph.D)--Mechanical Engineering, Georgia Institute of Technology, 2010.<br>Committee Chair: David L. McDowell; Committee Member: G. B. Olson; Committee Member: K. A. Gall; Committee Member: Min Zhou; Committee Member: R. W. Neu. Part of the SMARTech Electronic Thesis and Dissertation Collection.
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Ramachandran, Selvaraj. "Hypoid gear optimization." PDXScholar, 1992. https://pdxscholar.library.pdx.edu/open_access_etds/4419.
Full textAbstract:
A hypoid gear optimization procedure using the method of feasible directions has been developed. The objective is to reduce the gear set weight with bending strength, contact strength and facewidth-diametral pitch ratio as constraints. The objective function weight, is calculated from the geometric approximation of the volume of the gear and pinion. The design variables selected are number of gear teeth, diametral pitch, and facewidth. The input parameters for starting the initial design phase are power to be transmitted, speed, gear ratio, type of application, mounting condition, type of loading, and the material to be used. In the initial design phase, design parameters are selected or calculated using the standard available procedures. These selected values of design parameters are passed on to the optimization routine as starting points.