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Dissertations / Theses on the topic 'Mechanics'
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Lai, Jiun-Yu. "Mechanics, mechanisms, and modeling of the chemical mechanical polishing process." Thesis, Massachusetts Institute of Technology, 2001. http://hdl.handle.net/1721.1/8860.
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Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2001.<br>Includes bibliographical references.<br>The ever-increasing demand for high-performance microelectronic devices has motivated the semiconductor industry to design and manufacture Ultra-Large-Scale Integrated (ULSI) circuits with smaller feature size, higher resolution, denser packing, and multi-layer interconnects. The ULSI technology places stringent demands on global planarity of the Interlevel Dielectric (ILD) layers. Compared with other planarization techniques, the Chemical Mechanical Polishing (CMP) process produces excellent local and global planarization at low cost. It is thus widely adopted for planarizing inter-level dielectric (silicon dioxide) layers. Moreover, CMP is a critical process for fabricating the Cu damascene patterns, low-k dielectrics, and shallow isolated trenches. The wide range of materials to be polished concurrently or sequentially, however, increases the complexity of CMP and necessitates an understanding of the process fundamentals for optimal process design. This thesis establishes a theoretical framework to relate the process parameters to the different wafer/pad contact modes to study the behavior of wafer-scale polishing. Several models of polishing - microcutting, brittle fracture, surface melting and burnishing - are reviewed. Blanket wafers coated with a wide range of materials are polished to verify the models. Plastic deformation is identified as the dominant mechanism of material removal in fine abrasive polishing.<br>(cont.) Additionally, contact mechanics models, which relate the pressure distribution to the pattern geometry and pad elastic properties, explain the die-scale variation of material removal rate (MRR) on pattern geometry. The pad displacement into low features of submicron lines is less than 0.1 nm. Hence the applied load is only carried by the high features, and the pressure on high features increases with the area fraction of interconnects. Experiments study the effects of pattern geometry on the rates of pattern planarization, oxide overpolishing and Cu dishing. It was observed that Cu dishing of submicron features is less than 20 nm and contributes less to surface non-uniformity than does oxide overpolishing. Finally, a novel in situ detection technique, based on the change of the reflectance of the patterned surface at different polishing stages, is developed to detect the process endpoint and minimize overpolishing. Models that employ light scattering theory and statistical treatment correlate the sampled reflectance with the surface topography and Cu area fraction for detecting the process regime and endpoint. The experimental results agree well with the endpoint detection schemes predicted by the models.<br>by Jiun-Yu Lai.<br>Ph.D.
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Marcucci, Lorenzo. "A mechanical model of muscle mechanics." Phd thesis, Ecole Polytechnique X, 2009. http://pastel.archives-ouvertes.fr/pastel-00004880.
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de, Vries Edgar. "Mechanics and mechanisms of ultrasonic metal welding." The Ohio State University, 2004. http://rave.ohiolink.edu/etdc/view?acc_num=osu1078415529.
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Randow, Charles L. "Mechanisms and mechanics of non-structural adhesion." Thesis, This resource online, 1996. http://scholar.lib.vt.edu/theses/available/etd-11072008-063457/.
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De, Vries Edgar. "Mechanics and mechanisms of ultrasonic metal welding." Columbus, Ohio : Ohio State University, 2004. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1078415529.
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Thesis (Ph. D.)--Ohio State University, 2004.<br>Title from first page of PDF file. Document formatted into pages; contains xix, 253 p.; also includes graphics (some col.). Includes abstract and vita. Advisor: Karl Graff, Dept. of Industrial, Welding and Systems Engineering. Includes bibliographical references (p. 223-230).
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Matek, Christian C. A. "Statistical mechanics of nucleic acids under mechanical stress." Thesis, University of Oxford, 2014. http://ora.ox.ac.uk/objects/uuid:ce44cf50-2001-4f54-8e57-d1757f709fd6.
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In this thesis, the response of DNA and RNA to linear and torsional mechanical stress is studied using coarse-grained models. Inspired by single-molecule assays developed over the last two decades, the end-to-end extension, buckling and torque response behaviour of the stressed molecules is probed under conditions similar to experimentally used setups. Direct comparison with experimental data yields excellent agreement for many conditions. Results from coarse-grained simulations are also compared to the predictions of continuum models of linear polymer elasticity. A state diagram for supercoiled DNA as a function of twist and tension is determined. A novel confomational state of mechanically stressed DNA is proposed, consisting of a plectonemic structure with a denaturation bubble localized in its end-loop. The interconversion between this novel state and other, known structural motifs of supercoiled DNA is studied in detail. In particular, the influence of sequence properties on the novel state is investigated. Several possible implications for supercoiled DNA structures in vivo are discussed. Furthermore, the dynamical consequences of coupled denaturation and writhing are studied, and used to explain observations from recent single molecule experiments of DNA strand dynamics. Finally, the denaturation behaviour, topology and dynamics of short DNA minicircles is studies using coarse-grained simulations. Long-range interactions in the denaturation behaviour of the system are observed. These are induced by the topology of the system, and are consistent with results from recent molecular imaging studies. The results from coarse-grained simulations are related to modelling of the same system in all-atom simulations and a local denaturation model of DNA, yielding insight into the applicability of these different modelling approaches to study different processes in nucleic acids.
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Srivastava, Ankit. "Mechanics and Mechanisms of Creep and Ductile Fracture." Thesis, University of North Texas, 2013. https://digital.library.unt.edu/ark:/67531/metadc283799/.
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The main aim of this dissertation is to relate measurable and hopefully controllable features of a material's microstructure to its observed failure modes to provide a basis for designing better materials. The understanding of creep in materials used at high temperatures is of prime engineering importance. Single crystal Ni-based superalloys used in turbine aerofoils of jet engines are exposed to long dwell times at very high temperatures. In contrast to current theories, creep tests on Ni-based superalloy specimens have shown size dependent creep response termed as the thickness debit effect. To investigate the mechanism of the thickness debit effect, isothermal creep tests were performed on uncoated Ni-based single crystal superalloy sheet specimens with two thicknesses and under two test conditions: a low temperature high stress condition and a high temperature low stress condition. At the high temperature, surface oxidation induced microstructural changes near the free surface forming a layered microstructure. Finite element calculations showed that this layered microstructure gave rise to local changes in the stress state. The specimens also contained nonuniform distribution of initial voids formed during the solidification and homogenization processes. The experiments showed that porosity evolution could play a significant role in the thickness debit effect. This motivated a basic mechanics study of porosity evolution in single crystals subjected to creep for a range of stress states. The study was performed using three-dimensional finite deformation finite element analysis of unit cells containing a single initially spherical void in a single crystal matrix. The materials are characterized by a rate-dependent crystal plasticity constitutive relation accounting for both primary and secondary creep. The effect of initial void spacing and creep exponent was also explored. Based on the experimental observations and results of finite element calculations a quantitative mechanistic model is proposed that can account for both bulk and surface damage effects and assess their relative roles in the observed thickness debit effect. Another set of calculations aim at relating the crack growth resistance and fracture surface morphology to material microstructure for ductile structural metals. The process that governs the ductile fracture of structural materials at room temperature is one of nucleation, growth and coalescence of micron scale voids, and involves large plastic deformations. Experimental studies have shown that fracture surfaces in a wide variety of materials and under a wide variety of loading conditions have remarkable scaling properties. For thirty years, the hope to relate the statistical characterization of fracture surfaces to a measure of a material's crack growth resistance has remained unfulfilled. Only recently has the capability been developed to calculate sufficient amounts of three dimensional ductile crack growth in heterogeneous microstructures to obtain a statistical characterization of the predicted fracture surfaces. This development has enabled the exploration of the relation of both fracture toughness and fracture surface statistics to material properties and microstructure when the fracture mechanism is one of void nucleation, growth and coalescence. The relation of both toughness and the statistical properties of fracture surfaces in calculations of heterogeneous microstructures to various microstructural features is discussed and a remarkable correlation between fracture surface roughness and fracture toughness is shown for the first time.
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Porro, Cristina Shino. "Quantum mechanical/molecular mechanics studies of Cytochrome P450BM3." Thesis, University of Manchester, 2011. https://www.research.manchester.ac.uk/portal/en/theses/quantum-mechanical--molecular-mechanics-studies-of-cytochrome-p450bm3(ad4255e7-b779-47a2-a2c5-8dbf6b603ca5).html.
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Cytochrome P450 (P450) enzymes are found in all kingdoms of life, catalysing a wide range of biosynthetic and metabolic processes. They are, in fact, of particular interest in a variety of applications such as the design of agents for the inhibition of a particular P450 to combat pathogens or the engineering of enzymes to produce a particular activity. Bacterial P450BM3 is of particular interest as it is a self-sufficient multi-domain protein with high reaction rates and a primary structure and function similar to mammalian isoforms. It is an attractive enzyme to study due to its potential for engineering catalysts with fast reaction rates which selectively produce molecules of high value.In order to study this enzyme in detail and characterise intermediate species and reactions, the first step was to design a general hybrid quantum mechanical /molecular mechanics (QM/MM) computational method for their investigation. Two QM/MM approaches were developed and tested against existing experimental and theoretical data and were then applied to subsequent investigations.The dissociation of water from the water-bound resting state was scrutinised to determine the nature of the spin conversion that occurs during this transformation. A displacement of merely 0.5 Å from the starting state was found to trigger spin crossing, with no requirement for the presence of a substrate or large conformational changes in the enzyme.A detailed investigation of the sulfoxidation reaction was undertaken to establish the nature of the oxidant species. Both reactions involving Compound 0 (Cpd0) and Compound I (CpdI) confirmed a concerted pathway proceeding via a single-state reactivity mechanism. As the reaction involving Cpd0 was found to be unrealistically high, the reaction proceeds preferentially via the quartet state of CpdI. This QM/MM study revealed that the preferred spin-state and the transition state structure for sulfoxidation are influenced by the protein environment. P450cam and P450BM3 were found to have CpdI species with different Fe-S distances and spin density distributions, and the latter having a larger reaction barrier for sulfoxidation.A novel P450 species, the doubly-reduced pentacoordinated system, was characterised using gas-phase and QM/MM methods. It was discovered to have a heme radical coupled to two unpaired electrons on the iron centre, making it the only P450 species to have similar characteristics to CpdI. Calculated spectroscopic parameters may assist experimentalists in the identification of the elusive CpdI.
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Guillou, Lionel. "Cell Mechanics : Mechanical Properties and Membrane Rupture Criteria." Thesis, Université Paris-Saclay (ComUE), 2016. http://www.theses.fr/2016SACLX041/document.
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L’athérosclérose est une maladie artérielle chronique qui est une des causes majeures d’accidents vasculaires cérébraux et de crises cardiaques. Cette thèse a pour objectif de mieux comprendre certains facteurs spécifiques impliqués dans le dévelopement de cette maladie en abordant cette problématique sous l’angle de la mécanique.Deux types de cellules qui jouent un rôle important dans le dévelopement et la progression de l’athérosclérose sont les cellules endothéliales adhérentes et les leucocytes non-adhérents (les globules blancs). Nous avons développé deux systèmes capables de mesurer les propriétés mécaniques de ces deux grands types cellulaires. Le premier, appelé “indentation de profil”, utilise des micropipettes et des microindenteurs pour indenter la cellule, tandis que le second utilise la microfluidique pour soumettre les cellules à une contrainte d’élongation.De plus, nous nous sommes demandé si la mécanique pouvait nous aider à comprendre quand les déformations des cellules, ou les contraintes exercées sur elles, pouvaient les endommager.En effet, lorsque les plaques d’athérosclérose obstruent une partie trop grande du flux sanguin, le traitement le plus courant consiste à rouvrir le vaisseau avec un ballon et à le maintenir ouvert au moyen d’une endoprothèse artérielle, qui est un petit dispositif maillé et tubulaire. Cette procédure exerce des contraintes de compression considérables sur l’endothélium et l’endommage. Nous avons donc cherché à trouver un critère physique prédictif de la rupture de la membrane des cellules endothéliales en compression, puis avons comparé cela aux contraintes exercées sur l’endothélium durant la pose d’une endoprothèse artérielle, afin de voir si les dommages faits à l’endothélium pouvaient potentiellement être évités.De façon similaire, nous avons cherché à obtenir un critère physique prédictif de la rupture de la membrane des leucocytes. Nous avons ensuite comparé les déformations maximales possibles des leucocytes selon que ces déformations soient passives (comme lors du passage dans la microvasculature) ou actives (comme lors de la traversée de l’endothélium par les leucocytes)<br>Atherosclerosis is a chronic disease of the arteries that is a major cause of heart attacks and strokes. This thesis aims to provide novel insight into this disease by looking at specific factors involved in its development from a mechanical standpoint.Two important cell types involved in the development and progression of atherosclerosis are adherent endothelial cells and non-adherent leukocytes (white blood cells). We developed two devices that are able to measure the mechanical properties of both of these cell types. The first one, termed “profile microindentation”, uses micropipettes and microindenters to indent the cell, while the second one uses microfluidics to submit cells to an extensional stress.Further, we wondered if mechanics could help us understand when deformations undergone by cells, or stresses exerted on them, could become harmful.As a matter of fact, when atherosclerotic plaques occlude too much of the blood flow, the most common treatment consists of reopening the vessel with a balloon and keeping it open with a tubular wired mesh called a stent. This procedure exerts considerable compressive stress on the endothelium and is known to be associated with extensive endothelial damage. Hence, we seek to find a physical criterion that is predictive of endothelial cell membrane rupture under compression and to compare this to the stress exerted on the endothelium during the stenting procedure, to see if endothelial damage could potentially be avoided.Similarly, we seek to obtain a physical criterion that is predictive of leukocyte membrane rupture. We then compare and contrast the maximum possible deformations of leukocytes depending on whether those deformations are passive (such as when going through the microvasculature) or active (such as when leukocytes traverse the endothelial barrier)
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Pérez, Palau Daniel. "Dynamical transport mechanisms in celestial mechanics and astrodynamics problems." Doctoral thesis, Universitat de Barcelona, 2015. http://hdl.handle.net/10803/362369.
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L’objectiu d’aquesta tesi és afegir una petita fulla a l’arbre del coneixement. En particular a la branca del sistemes dinàmics. La teoria de sistemes dinàmics és la branca de les matemàtiques que estudia l’evolució del que ens envolta. Un dels objectius de la teoria dels sistemes dinàmics és estudiar com evoluciona amb el temps un cert procés evolutiu, és a dir, donades unes condicions inicials per a un cert estat, quin serà l’estat del sistema “t” unitats de temps. En alguns problemes és possible trobar estructures que ens separen diferents tipus de moviment. Per exemple, un moviment fitat d’un de no fitat. Aleshores, aquestes estructures determinen com evolucionà el sistema sota estudi. En aquest cas parlem de mecanismes dinàmics de transport. És a dir, quines són les possibles maneres que té un cert estat d’arribar a un altre. La teoria de sistemes dinàmics treu models i problemes gran varietat d’àmbits científics. En aquesta tesi ens centrarem en problemes de mecànica celeste i astrodinàmica.
L’estructura de la present tesi és com segueix:
− El Capítol 1 està dedicat a introduir alguns dels conceptes que es fan servir en els capítols posteriors, així com qüestions de notació i la definició dels sistemes dinàmics que s’empraran.
− En el Capítol 2 s’introdueix l’eina principal de la tesi, el Jet Transport. Per fer-la servir cal implementar una àlgebra de polinomis. El capítol explica com fer aquesta implementació. Les primeres seccions es dediquen a explicar com fer un ús eficient de la memòria i a introduir les operacions bàsiques amb polinomis (el producte per un escalar, la suma, el producte, la divisió de dos polinomis). També s’explica com realitzar altres operacions elementals com l’exponencial, el logaritme, el sinus i el cosinus així com la derivació i la integració de polinomis. A les darreres seccions s’explica com implementar operacions més complexes com la propagació de fluxos (incloent el càlcul d’aplicacions de Poincaré i altres tècniques per a millorar els resultats obtinguts), el càlcul de la inversa funcional d’un polinomi i la transformació de densitats mitjançant una aplicació.
− El Capítol 3 està dedicat a parlar sobre indicadors dinàmics. Primer es repassen els exponents de Lyapunov a temps finit i les estructures lagrangianes coherents. Fruit d’aquestes reflexions es desenvolupen algorismes per tal de disminuir el temps de còmput. Tot seguit, es donen quatre indicadors de la dinàmica alternatius basats en el Jet Transport: la màxima mida de la caixa inicial, la màxima relació d’expansió, la màxima relació de contracció i la màxima relació d’expansió a l’espai normal. El capítol segueix desenvolupant un algorisme d’extracció d’estructures per tal d’extreure i resumir la informació donada pels indicadors dinàmics. Finalment, es fan servir els indicadors dinàmics introduïts per tal de determinar zones d’estabilitat efectiva en el problema restringit de tres cossos.
− En el Capítol 4 s’estudia la col·lisió de satèl·lits artificials. Primerament s’estudien les diferents per torbacions que afecten al moviment de satèl·lits al voltant de la terra. Es considera un problema de dos cossos amb pertorbacions degudes al potencial terrestre, a la força de fregament atmosfèric i a la gravetat de la Lluna i el Sol. S’estudien els efectes d’aquestes pertorbacions i també com realitzar l’implementació mitjançant el Jet Transport. El capítol acaba amb algunes simulacions de Monte Carlo per extreure informació d’una col·lisió semblant a la produïda entre els satèl·lits Iridium-33 i el Kosmos-2251 l’any 2009.
− L’annex A explica breument les funcions desenvolupades per a aquesta tesi i s’introdueixen unes petites notes sobre paral·lelització de codis en C mitjançant open MP.
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Miao, Yuyang. "Mechanics of textile composites : from geometry to mechanical properties /." Search for this dissertation online, 2005. http://wwwlib.umi.com/cr/ksu/main.
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Blackstone, Britani Nicole. "Biomaterial, Mechanical and Molecular Strategies to Control Skin Mechanics." The Ohio State University, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=osu1406123409.
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Tiernan, Declan Martin. "Collocation studies in fracture mechanics and quantum mechanics." Thesis, Queen's University Belfast, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.318739.
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Amiouny, Samir V. "Combinatorial mechanics." Diss., Georgia Institute of Technology, 1993. http://hdl.handle.net/1853/25576.
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Cohen, A. E. "Nanoscale mechanics." Thesis, University of Cambridge, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.597814.
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The mechanical properties of very small systems are often strikingly different from the properties of everyday objects. As one considers ever-smaller objects, thermal fluctuations, and then quantum fluctuations start to be important. In this thesis I explain some unusual nanoscale mechanical effects, and predict some new effects. The bulk of the thesis is devoted to calculating the forces between bodies that are closely spaced, but not touching. These van der Waals forces have been studied in detail for bodies in thermal equilibrium. Most of the world is not in thermal equilibrium, and van der Waals forces in this regime are very different from their equilibrium cousins. In contrast to equilibrium forces, nonequilibrium forces are much stronger and may show chemical specificity. There is a <i>friction</i> associated with the van der Waals force between bodies in relative motion. When the bodies are at different temperatures, this friction may be negative. Intermolecular forces with one molecule excited are far stronger than ground-state forces and may be attractive or repulsive. Any optical effect in matter modifies the forces between the constituent molecules. The second part of this thesis is on solitonic kinks in fibrillar materials (e.g. polymers, actin bundles, microtubules, carbon nanotubes). All of these materials support stable kinks, and these kinks play an important role in determining the mechanical properties; often more important than the detailed chemical makeup of the materials.
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Tate, Eric Jordon. "Quantum Mechanics." Digital Commons at Loyola Marymount University and Loyola Law School, 2018. http://www.kaltura.com/tiny/8izg0.
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Liu, Guoning. "Application of fracture mechanics in electrical/mechanical failures of dielectrics /." View abstract or full-text, 2006. http://library.ust.hk/cgi/db/thesis.pl?MECH%202006%20LIU.
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Jonsson, Anders. "Integral equation methods for fracture mechanics and micro-mechanical problems." Doctoral thesis, KTH, Solid Mechanics, 2002. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3336.
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Bouck, David Cannon Bloom Kerry S. "Mitotic mechanics and mechanisms of the budding yeast Saccharomyces cerevisiae." Chapel Hill, N.C. : University of North Carolina at Chapel Hill, 2007. http://dc.lib.unc.edu/u?/etd,831.
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Thesis (Ph. D.)--University of North Carolina at Chapel Hill, 2007.<br>Title from electronic title page (viewed Dec. 18, 2007). "... in partial fulfillment of the requirements for the degree of Doctor of Philosophy in the Department of Biology." Discipline: Biology; Department/School: Biology.
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Levert, Joseph Albert. "Interface mechanics of chemical mechanical polishing for integrated circuit planarization." Diss., Georgia Institute of Technology, 1997. http://hdl.handle.net/1853/15914.
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Svantesson, Cecilia. "Respiratory mechanics during mechanical ventilation in health and in disease." Lund : Dept. of Clinical Psychology, Lund University, 1997. http://catalog.hathitrust.org/api/volumes/oclc/38987113.html.
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Tan, Kar Tean. "The mechanics and mechanisms of environmental attack on structural adhesive joints." Thesis, Imperial College London, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.420992.
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Ghadbeigi, Hassan. "Metal cutting mechanics : investigation and simulation of deformation and damage mechanisms." Thesis, University of Sheffield, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.531224.
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Szklarzewski, Veronica. "A mechanism for testing the torsional mechanics of origami-inspired hinges." Thesis, Massachusetts Institute of Technology, 2015. http://hdl.handle.net/1721.1/98760.
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Thesis: S.B., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2015.<br>Cataloged from PDF version of thesis.<br>Includes bibliographical references (page 29).<br>Folding 2-dimensional sheets into static and dynamic 3-dimensional structures has the potential to improve rate, cost, and flexibility in manufacturing. In order to explore origami-inspired design, a better understanding of the mechanics of the fold is needed. This is to create better mathematical models and design for particular stiffness and fatigue specifications. The purpose of this study is to create a desktop machine that enables the measurement of the torsional stiffness of folded hinges over a wide angular range and a large number of cycles. This machine was then used to test 100 and 140 lb papers with 4 and 14 scores for the crease. Each paper was tested for 10 cycles and stiffness calculated. It was shown that 40 lb papers have higher reaction forces than the 100 lb papers. Stiffness measurements were inconclusive due to possible bending in addition to the hinging. For the 200 cycle around a 2 g decrease can be seen from I cycle to 200 cycles.<br>by Veronica Szklarzewski.<br>S.B.
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Yue, Peng. "A micro mechanical study of critical state soil mechanics using DEM." Thesis, University of Nottingham, 2016. http://eprints.nottingham.ac.uk/38060/.
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One of the greatest breakthroughs in soil mechanics was the development of Critical State Soil Mechanics (CSSM) in the 1950s and 1960s and the derivation of a continuum elasto-plastic constitutive model, namely Cam clay, which was the foundation for other continuum models for clays, and much later for sands. However, as yet there has been no micro mechanical analysis which explains the existence of such continuum models; such a micro perspective must take into account the discontinuous nature of soil. Without such insight, the engineer cannot understand which micro parameters affect soil behaviour. This work uses the discrete element method (DEM) to model a silica sand as a sample of discrete particles, with properties which have been calibrated against experimental data in previous work, to build up a micro mechanical picture of the behaviour of sand under different loading conditions. The simplest of loading conditions is the one dimensional or oedometer test and has been modelled to check whether this agrees with previously published research. The simulated sample has then been subjected to isotropic compression to establish a normal compression line in log voids ratio – log stress space, and which turns out to be parallel to the one-dimensional normal compression line, in agreement with CSSM. The evolution of the isotropic normal compression line is due to local shear stresses within the sample, and the origin of the existence of both lines lies in the evolution of a fractal distribution of particles with a fractal dimension of 2.5. The effect of boundary particles has then been minimised by choosing an appropriate aspect ratio and a smaller number of particles in the sample to give a computational time which is acceptable for subsequent shearing to critical states. Isotropically normally compressed samples have been unloaded to different stress levels and sheared to critical states. A unique critical state line (CSL) exists at high stress levels, which is parallel to the normal compression lines, in agreement with CSSM. At low stress levels, the CSL is not linear and is non-unique; that is to say it is a function of preconsolidation pressure because the fractal distribution of sizes has not fully evolved. Samples sheared on the dense side of critical dilate and have a peak strength whilst loose samples exhibit ductile contraction, in agreement with CSSM. At a critical state, the work shows that crushing continues in the formation of ‘fines’, small particles with smaller than 0.1mm dimensions, which plays no part in the mechanical behaviour, which is reflected in the average mechanical co-ordination number and which means that plastic hardening can be assumed to have ceased at a critical state. For the isotropically overconsolidated samples sheared to critical states, a number of different definitions of yield have been used to establish a yield surface in stress space. The work shows that a previously published yield surface for sand (Yu, 1998; McDowell, 2002) gives a good representation of the behaviour, and it has therefore been shown that the sample of discrete particles has been shown to give rise to observed continuum behaviour. The work is, to the author’s knowledge, the first that has shown a DEM soil to show many of the desirable features of sand, in that the sample qualitatively gives normal compression lines and a CSL of the correct slope, which obeys CSSM and which gives a Cam Clay type yield surface in stress space. The work means that the established model can be used in the study of other micro mechanics problems such as particle shape and time effects and the application of DEM to boundary value problems directly.
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Zhang, Qiuting. "Mechanics and Functionality of Extreme Mechanical Instabilities through Buckling Driven Delamination." Diss., Temple University Libraries, 2019. http://cdm16002.contentdm.oclc.org/cdm/ref/collection/p245801coll10/id/587760.
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Mechanical Engineering<br>Ph.D.<br>Mechanical instabilities such as wrinkling and buckling-driven delamination in thin film-substrate systems have historically been considered as one of structural failure mechanisms, which should be avoided. The past decade has witnesssed rapid growth in harnessing such surface instabilities for a wide range of tunable surface related properties and functionalities, especially in soft materials on small scales. Compared to extensively studied wrinkling on soft substrates and localized buckling driven delamination on stiff substrates, the fundamental mechanics underpinning ordered buckle-delamination on soft substrate over large area and its guidance for potential implications in engineering innovation remain largely to be explored. This thesis aims to partially bridging such a knowledge gap. In this thesis, I exploit how to generate the controllable and globally periodic delaminated buckling patterns in thin films on highly prestrained elastomeric substrates, and then explore the fundamental mechanics of this spontaneous extreme buckling driven periodic delamination, as well as its implications in design of extremely stretchable electronics and interfacial mechanical properties measurement. Compared to wrinkling, one of the benefits of extremely buckling driven delamination is the extraordinarily high aspect ratio of buckles. The large surface roughness and high local curvature could potentially enable extreme surface topographies related properties, such as adhesion, wetting, friction, and optics, as well as augment the extreme stretchability in stretchable optical and electronic devices. In the aim of harnessing this extreme buckling driven delamination, I first explore the formation and evolution of extraordinarily high-aspect-ratio delaminated buckles of thin films on 400% pre-strained elastomers, as well as uncovered the underlying deformation mechanism through combining quantitative theoretical analysis and experimental and numerical approaches. A theoretical framework is developed to describe the formation and evolution process of periodic delaminated buckles, which includes three deformation stages, i.e. onset of localized blisters (Stage I), growth and propagation of delamination (Stage II), and post-buckling after delamination arrest (Stage III). I show that under extreme large compressive strain, the profile of periodic blisters changes from sinusoidal shape to jig-saw-like shape with relative high aspect ratio, which have potential applications for design of extremely stretchable electronics. Equipped with the fundamental mechanics of buckle-delamination in thin films, I then exploit harnessing the spontaneous buckling driven periodic delamination to achieve high stretchability in both metal and silicon films. Experimentally I observe periodic buckle-delaminated patterns over large area, accompanied by highly ordered transversely cracking patterns, which can be theoretically predicted by simple crack fragments model. I hypothesize that when the width of ribbons is set to be equal or smaller than the theoretically predicted crack fragment width, there would be no cracking fragmentation. This criteria for designing crack-free micro-ribbons is further validated by related experiments. Guided by the validated criteria, I successfully design crack-free and spontaneous delaminated ribbons on highly prestrained elastomer substrates, which provides a high stretchability of about 120% and 400% in Si and Au ribbons, respectively. I further extend the buckling instability-based metrology to systematically measure the mechanical properties of 2D organic conjugated polymer nano-films, which have tremendous promising applications in organic integrated circuits, solar cells, and stretchable devices. I develop a new fabrication strategy to generate buckle-delaminated free-standing organic conjugated polymeric (P3BT/C60) nanosheets. Through both experiments and theoretical analysis, I show that the free-standing buckle-delaminated organic P3BT/C60 nanosheets have significant advantages over the traditional spin-coated wrinkled nanosheets, including the enhanced mechanical properties, a higher level of stretchability with lower electrical resistance, and a wider range of controllable wettability modulation.<br>Temple University--Theses
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Ameli, Jacopo. "Visualizing Game Mechanics." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2019.
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Visualizzare le meccaniche di gioco è un modo importante per consentire di definire, rivedere e migliorare lo sviluppo di videogiochi, specialmente in situazioni dove è necessaria una migliore comunicazione tra molti programmatori e designer. Sono stati sviluppati diversi approcci manuali ed automatici negli ultimi anni, ma alcuni sono troppo astratti e distaccati dal contesto di gioco, altri troppo vicini al codice vero e proprio, altri ancora non hanno alcun collegamento ad esso. In questa dissertazione proponiamo l’architettura di un sistema modulare che potrebbe automaticamente costruire e visualizzare una rappresentazione grafica leggibile in grado di stimolare analisi delle meccaniche di gioco e ragionamenti causali sulle dipendenze tra le variabili del codice. Presentiamo inoltre un’implementazione iniziale dello strumento di visualizzazione, capace di importare un grafo da un file utente e partizionarlo secondo parametri personalizzabili. Infine, riporteremo i risultati della valutazione delle capacità e dell’utilità dello strumento come supporto allo sviluppo creativo.
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Denzer, Ralf. "Computational configurational mechanics." [S.l.] : [s.n.], 2006. http://deposit.ddb.de/cgi-bin/dokserv?idn=978669797.
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WASAY, MUHAMMED. "Supersymmetric Quantum Mechanics." Thesis, Uppsala University, Theoretical Physics, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-126725.
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<p>This Master thesis considers certain aspects of Supersymmetric Quantum Mechanics in the context of Path integral approach. First we state all the basic mathematical structure involved, and carry out some basic Gaussian integrals for both commutative and non-commutative variables. Later in the thesis these simple results obtained are generalized to study the Supersymmetric sigma models on flat and curved space. And we will recover the beautiful relationship between the supersymmetric sigma model and the geometry of the target manifold in the form of topological invariants of the manifold, for the models on curved space.</p>
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Smith, Daniel Patrick. "Transient bed mechanics." Thesis, University of Cambridge, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.620448.
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Wylie, Jonathan James. "Geological fluid mechanics." Thesis, University of Cambridge, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.627211.
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McDowell, Glenn Richard. "Clastic soil mechanics." Thesis, University of Cambridge, 1996. https://www.repository.cam.ac.uk/handle/1810/272016.
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Kleinig, Andrew Royce. "Cell disruption mechanics /." Title page, summary and table of contents only, 1997. http://web4.library.adelaide.edu.au/theses/09PH/09phk64.pdf.
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Sakatani, Yuho. "Relativistic viscoelastic fluid mechanics and the entropic formulation of continuum mechanics." 京都大学 (Kyoto University), 2012. http://hdl.handle.net/2433/157762.
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Sears, Aaron Thomas. "Carbon Nanotube Mechanics: Continuum Model Development from Molecular Mechanics Virtual Experiments." Diss., Virginia Tech, 2006. http://hdl.handle.net/10919/29959.
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Carbon Nanotubes (CNTs) hold great promise as an important engineering material for future applications. To fully exploit CNTs to their full potential, it is important to characterize their material response and ascertain their material properties. We have used molecular mechanics (MM) simulations to conduct virtual experiments on single-wall and multi-wall carbon nanotubes (SWNTs and MWNTs respectively) similar to those performed in the mechanics of materials laboratory on a continuum structure. The output (energy and deformation rather than the load and deflection) is used to understand the material response and formulate macroscopic constitutive relations.
From results of MM simulations of axial and torsional deformations on SWNTs, Young's modulus, the shear modulus and the wall thickness of an equivalent continuum tube made of a linear elastic isotropic material were found. These values were used to compare the response of the continuum tube, modeled as an Euler-Bernoulli beam, in bending and buckling with those obtained from the MM simulations.
MM simulations have been carried out to find energetically favorable double-walled carbon nanotube (DWNT) configurations, and analyze their responses to extensional, torsional, radial expansion/contraction, bending, and buckling deformations. Loads were applied either to one wall or simultaneously to both walls of an open-ended DWNT. These results were compared against SWNT results. It was found that for simple tension and torsional deformations, results for a DWNT can be derived from those for its constituent SWNTs within 3% error. Radial deformations of a SWNT were achieved by considering a DWNT with the SWNT as one of its walls and moving radially through the same distance all atoms of the other wall of the DWNT thereby causing a pseudo-pressure through changes in the cumulative van der Waals forces which deform the desired wall. Results of radial expansion/contraction of a SWNT were used to deduce an expression for the van der Waals forces, and find through-the-thickness elastic moduli (Young's modulus in the radial direction, Er, and Poisson's ratio ?r?) of the SWNT. We have found four out of the five elastic constants of a SWNT taken to be transversely isotropic about a radial line.
MWNTs were studied using the same testing procedures as those used SWNTs. Based on the results from those simulations a continuum model is proposed for a MWNT whose response to mechanical deformations is the same as that of the MWNT. The continuum structure is comprised of concentric cylindrical tubes interconnected by truss elements. Young's modulus, Poisson's ratio, the thickness of each concentric tube, and the stiffness of the truss elements are given. The proposed continuum model is validated by studying its bending and buckling deformations and comparing these results to those from MM simulations.
The major contributions to the field on nanotubes and the scientific literature is a simple and robust continuum model for nanotubes. This model can be used to study both SWNTs and MWNTs in either global or local responses by applying different analytic techniques. This model was developed using a consistent engineering methodology that mimicked traditional engineering testing, assumptions and constraints.<br>Ph. D.
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Vonderheide, Christopher M. "Laser velocimetric flow mapping and characterization of oil mist nozzles used for blade excitation in high cycle fatigue testing." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2005. http://library.nps.navy.mil/uhtbin/hyperion/05Sep%5FVonderheide.pdf.
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Thesis (M.S. in Mechanical Engineering)--Naval Postgraduate School, September 2005.<br>Thesis Advisor(s): Dr. Raymond Shreeve, Dr. Garth Hobson. Includes bibliographical references (p. 61). Also available online.
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Fountoukidis, Evangelos. "Thermo-mechanical response of monolithic and NiTi shape memory alloy fiber reinforced Sn-3.8Ag-0.7Cu solder." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2005. http://library.nps.navy.mil/uhtbin/hyperion/05Sep%5FFountoukidis.pdf.
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Hosoglu, Selcuk. "Cellular automata an approach to wave propagation and fracture mechanics problems." Thesis, Monterey, Calif. : Naval Postgraduate School, 2006. http://bosun.nps.edu/uhtbin/hyperion.exe/06Dec%5FHosoglu.pdf.
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Thesis (M.S. in Mechanical Engineering)--Naval Postgraduate School, December 2006.<br>Thesis Advisor(s): Young W. Kwon. "December 2006." Includes bibliographical references (p. 63-64). Also available in print.
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Betancourt, Arturo. "Computational study of the heat transfer and fluid structure of a shell and tube heat exchanger." Thesis, Florida Atlantic University, 2016. http://pqdtopen.proquest.com/#viewpdf?dispub=10172609.
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<p> A common technique to improve the performance of shell and tube heat exchangers (STHE) is by redirecting the flow in the shell side with a series of baffles. A key aspect in this technique is to understand the interaction of the fluid dynamics and heat transfer. Computational fluid dynamics simulations and experiments were performed to analysis the 3-dimensional flow and heat transfer on the shell side of an STHE with and without baffles. Although, it was found that there was a small difference in the average exit temperature between the two cases, the heat transfer coefficient was locally enhanced in the baffled case due to flow structures. The flow in the unbaffled case was highly streamed, while for the baffled case the flow was a highly complex flow with vortex structures formed by the tip of the baffles, the tubes, and the interaction of flow with the shell wall.</p>
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Barry, Matthew M. "Analytical and experimental studies of thermoelectric devices and materials." Thesis, University of Pittsburgh, 2016. http://pqdtopen.proquest.com/#viewpdf?dispub=10183683.
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<p> Interest in thermoelectric devices (TEDs) for waste-heat recovery applications has recently increased due to a growing global environmental consciousness and the potential economic benefits of increasing cycle efficiency. Unlike conventional waste-heat recovery systems like the organic Rankine cycle, TEDs are steady-state, scalable apparatus that directly convert a temperature difference into electricity using the Seebeck effect. The benefits of TEDS, namely steady-state operation and scalability, are often outweighed by their low performance in terms of thermal conversion efficiency and power output. To address the issue of poor device performance, this dissertation takes a multi-faceted approach focusing on device modeling, analysis and design and material processing.</p><p> First, a complete one-dimensional thermal resistance network is developed to analytically model a TED, including heat exchangers, support structures and thermal and electrical contact resistances. The purpose of analytical modeling is twofold: to introduce an optimization algorithm of the thermoelectric material geometry based upon the realized temperature difference to maximize thermal conversion efficiency and power output; and to identify areas within the conventional TED that can be restructured to allow for a greater temperature difference across the junction and hence increased performance. Additionally, this model incorporates a component on the numerical resolution of radiation view factors within a TED cavity to properly model radiation heat transfer. Results indicate that geometric optimization increases performance upwards of 30% and the hot-side ceramic diminishes realized temperature difference. The resulting analytical model is validated with published numerical and comparable analytical models, and serves as a basis for experimental studies.</p><p> Second, an integrated thermoelectric device is presented. The integrated TED is a restructured TED that eliminates the hot-side ceramic and directly incorporates the hot-side heat exchanger into the hot-side interconnector, reducing the thermal resistance between source and hot-side junction. A single-state and multi-stage pin-fin integrated TED are developed and tested experimentally, and the performance characteristics are shown for a wide range of operating fluid temperatures and flow rates. Due to the eliminated to thermal restriction, the integrated TED shows unique performance characteristics in comparison to conventional TED, indicating increased performance.</p><p> Finally, a grain-boundary engineering approach to material processing of bulk bismuth telluride (Bi<sub>2</sub>Te<sub>3</sub>) is presented. Using uniaxial compaction and sintering techniques, the preferred crystallographic orientation (PCO) and coherency of grains, respectively, are controlled. The effect of sintering temperature on thermoelectric properties, specifically Seebeck coefficient, thermal conductivity and electrical resistivity, are determined for samples which exhibited the highest PCO. It is shown the performance of bulk Bi<sub>2</sub>Te<sub>3</sub> produced by the presented method is comparable to that of nano-structured materials, with a maximum figure of merit of 0.40 attained at 383 K.</p>
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Vaidya, Anirudha. "Load-Displacement Relations for an Edge-Cracked Beam with a Hysteretic Bilinear Cohesive Zone Model." The Ohio State University, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=osu1408958644.
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Qian, Jing. "Discrete gradient method in solid mechanics." Diss., University of Iowa, 2009. https://ir.uiowa.edu/etd/261.
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The discrete gradient method is proposed as a novel numerical tool to perform solid mechanics analysis directly on point-cloud models without converting the models into a finite element mesh. This method does not introduce continuous approximation of the primary unknown field variables; instead, it computes the gradients of the field variables at a node using discrete differentials involving a set of neighboring nodes. The discrete gradients are substituted into Galerkin weak from to derive the algebraic governing equations for further analysis. Therefore, the formulation renders a completely discrete computation that can conduct mechanical analysis on point-cloud representations of patient-specific organs without resorting to finite element method.
Since the method is prone to rank-deficient instability, a stabilized scheme is developed by employing penalty that involves a minor modification to the method. The difference between nodal strain and subcell strain is penalized to prevent the appearance of zero average strain.
This dissertation delineates the theoretical underpins of the method and provides a detailed description of its implementation in two and three-dimensional elasticity problem. Several benchmark numerical tests are presented to demonstrate the accuracy, convergence, and capability of dealing with compressibility and incompressibility constraint without severe locking. An efficient method is also developed to automatically extract point-cloud models from medical images. Two and three-dimensional examples of biomedical applications are presented too.
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Meliá, Fortuño Concepción. "Quantum Mechanics/Molecular Mechanics modeling of biological relevant reactions catalyzed by enzymes." Doctoral thesis, Universitat Jaume I, 2017. http://hdl.handle.net/10803/455140.
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A theoretical study of the hydrolysis of a β-lactam antibiotic was carried out in gas phase at different levels of theory. Later, the reaction was studied in solution, describing the sub-set of atoms of the QM region with semiempirical and density functional theory methods while classical force fields were used to describe the explicit solvent water molecules. QM/MM Molecular Dynamics simulations were used to generate the potential of mean force for the reaction in solution. The mechanism of hydrolysis of two antibiotics were explored in the active site of a mononuclear β lactamase. QM/MM methods have been applied to the study of an enzyme belonging to the family of copper monooxygenases. In particular the mechanism of hydroxylation by peptidylglycine α-hydroxylating monooxygenase was the subject of the study. Due to the electronic complexity of the system, ab initio MD simulations were required in order to get a proper description of the reaction.<br>Se realizó un estudio teórico de la hidrólisis de un antibiótico β-lactámico en vacio a diferentes niveles de cálculo. A continuación la reacción se estudió en disolución acuosa utilizando métodos semiempíricos y métodos basados en la teoría del funcional de la densidad para describir el subconjunto de átomos de la región QM, las moléculas de agua se describieron de forma discreta con campos de fuerza clásicos. Se utilizaron simulaciones de dinámica molecular con potenciales híbridos QM/MM para generar el potencial de fuerza media para la reacción en disolución. Se exploró el mecanismo de hidrólisis de dos antibióticos en el centro activo de una enzima β lactamasa. Y se estudió una enzima de la familia de las monooxigenasas de cobre. El objeto de estudio fue el mecanismo de hidroxilación por la peptidilglicina α-monooxigenasa hidroxilante. Fue necesario simulaciones de MD ab initio con el fin de obtener una descripción adecuada de la reacción.
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Scotte, Anton, and Emil Zeidlitz. "Investigating the Numerical Applicability of Analogies between Quantum Mechanics and Fluid Mechanics." Thesis, KTH, Skolan för teknikvetenskap (SCI), 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-276578.
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Lin, Gaojian. "Instability driven reconfigurable soft materials: mechanics and functionality." Diss., Temple University Libraries, 2018. http://cdm16002.contentdm.oclc.org/cdm/ref/collection/p245801coll10/id/508542.
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Mechanical Engineering<br>Ph.D.<br>Mechanical instability, a deformation mode involving abrupt switching between two distinct equilibrium structural configurations, has historically been viewed as a failure mechanism in engineering and materials science. Since the pioneering work in harnessing spontaneous buckling for surface micro-patterning in 1998, tremendous research interest has focused to utilize, rather than avoid, buckling instability in soft materials at small scale for achieving unique properties and multifunctionality. The benefit of small-scale bucking instability in soft materials and structures lies in the reversible dynamic tunability of the buckled structural or surface configuration in response to different external stimuli, which enables the coupling of structural or surface reconfiguration with dynamically tunable properties, such as mechanical, optical, wetting, and electrical properties. In this dissertation, I explore the fundamental mechanics and functionality of surface-based buckling and hierarchical wrinkling on substrates in multifunctional opto-electronic devices and smart windows. I will first explore the benefits of classical plate buckling in soft materials. The challenge lies in the intrinsic indeterminate characteristics of buckling in terms of its buckling orientation, which could lead to geometric frustration and random global structures. To address this challenge, I introduce cuts-based geometrical imperfection to guide the deterministic buckling in arrays of parallel active polymeric plates on rigid substrates. After introducing patterned cuts, the originally random phase-shifted buckling transits to a prescribed buckling with controllable phases. The design principle for cut-directed deterministic buckling in plates is revealed through both mechanics model and finite element simulation. By harnessing cut-directed buckling for controllable contacts and interactions in buckled parallel plates, I demonstrate the array of parallel plates as a multifunctional platform for selectively steering the electronic and optical pathways on demand, as well as the potential application in design of mechanical logic gates. I then explore the hierarchical wrinkling of thin films on soft substrates via sequential wrinkling for design of a potential multifunctional smart window with combined structural color and water droplet transport control. The self-similar hierarchical wrinkles with both nanoscale and microscale features are generated on a pre-strained poly(dimethylsiloxane) (PDMS) elastomer through sequential strain release and multi-step oxygen plasma treatment. I exploit the criteria for generating self-similar hierarchical wrinkles through both simplified theoretical model and experiments. I show that the hierarchically wrinkled elastomer displays both opaqueness and iridescent structural color. I further show its ability in control of water droplet transport on demand through mechanical stretching and release. I further extend the study of self-similar hierarchical wrinkling to the dynamic wetting behavior of multiscale self-similar hierarchical wrinkled surfaces on PDMS substrates through combined plasma and ultraviolet ozone (UVO) treatment. The generated surface structure shows an independently controlled dual-scale roughness with level-1 small-wavelength wrinkles resting on level-2 large-wavelength wrinkles, as well as accompanying orthogonal cracks. By tuning the geometry of hierarchical wrinkles, I explore the small degree of wetting anisotropy in hierarchical wrinkled surfaces, defined as the contact angle difference between the parallel and perpendicular directions to the wrinkle grooves through both experimental characterization (confocal fluorescence imaging) and theoretical analyses. I find that the measured larger apparent contact angle than the theoretically predicted Wenzel contact angle is attributed to the three-phase contact line pinning effect of both wrinkles and cracks, which generates energetic barriers during the contact line motion. I reveal that the observed small degree of wetting anisotropy in the hierarchical wrinkled surfaces arises from the competition between orthogonal wrinkles and cracks in the contact line pinning.<br>Temple University--Theses
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Jones-Smith, Katherine A. "Non-Hermitian Quantum Mechanics." Cleveland, Ohio : Case Western Reserve University, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=case1270231293.
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Thesis (Doctor of Philosophy)--Case Western Reserve University, 2010<br>Department of Physics Title from PDF (viewed on 2010-05-25) Includes abstract Includes bibliographical references and appendices Available online via the OhioLINK ETD Center
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Chen, Jing. "Mechanics of optimal rowing." Thesis, KTH, Mekanik, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-38289.
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The forward dynamic approach is different from the inverse dynamic one, and could set up the relation between the angles and controls. The author tries to analyze the optimal rowing movement patterns between the catch and finish configurations in drive phase. The relation between the angles and controls is collected as a set of dynamic equilibrium equations. These equations utilize a finite element time discretization, and are solved simultaneously for the time T (Kaphle and Eriksson, 2008). Finally, the moving trajectory is obtained, and also the change of the angles and controls could be found.
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Hutchinson, Robert Gorm. "Mechanics of lattice materials." Thesis, University of Cambridge, 2005. https://www.repository.cam.ac.uk/handle/1810/251949.
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Baxter, John. "Mechanics of granular heaps." Thesis, University of Surrey, 1998. http://epubs.surrey.ac.uk/843468/.
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The formation and evolution of heaps of granular material has in recent years received ever-increasing research attention. As with other aspects of the granular physics field, much of this attention has focused on the use of numerical simulations, including the discrete element modelling technique. Before advancements in computing technology made numerical methods a viable option, assemblies of granular materials were typically rather poorly characterised by a limited range of bulk properties, such as the angle of repose of a heap. Such properties were found to be rather insensitive to the characteristics of the individual particles and as such were of limited practical use as the basis for process design. Consequently, problems in granular materials storage, handling and flow were typically tackled using semi-empirical approaches relying on long experience of similar process situations. The availability of computing resources has resulted in the spawning of a widely diverse range of numerical simulation approaches for the solution of bulk solids handling problems. However, this development in itself has given rise to further problems. The poor characterisation of assemblies by bulk properties has made experimental confirmation of numerical simulation techniques difficult, and this is perhaps partly responsible for the injudicious use of inappropriate numerical techniques within the research community. By a systematic study of the mechanics of granular heaps using the discrete element technique, this dissertation establishes that the choice of mathematical model and model parameters at the heart of any numerical method is of crucial importance for the realistic simulation of granular assemblies. The angle of repose is established as being rather insensitive to most single particle properties. The dissertation establishes the usefulness of the granular dynamics simulation method by demonstrating how internal 'microstructural' properties of granular heaps can be computed, and examines how simulation can complement relatively new non-invasive techniques for measuring such properties experimentally. Simulation and experiment are also used as the basis for a tentative mathematical model for the kinetics of segregation and stratification processes in poured heaps.
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Kellermann, David Conrad Mechanical & Manufacturing Engineering Faculty of Engineering UNSW. "Strongly orthotropic continuum mechanics." Publisher:University of New South Wales. Mechanical & Manufacturing Engineering, 2008. http://handle.unsw.edu.au/1959.4/41454.
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The principal contribution of this dissertation is a theory of Strongly Orthotropic Continuum Mechanics that is derived entirely from an assertion of geometric strain indeterminacy. Implementable into the finite element method, it can resolve widespread kinematic misrepresentations and offer unique and purportedly exact strain-induced energies by removing the assumptions of strain tensor symmetry. This continuum theory births the proposal of a new class of physical tensors described as the Intrinsic Field Tensors capable of generalising the response of most classical mechanical metrics, a number of specialised formulations and the solutions shown to be kinematically intermediate. A series of numerical examples demonstrate Euclidean objectivity, material frame-indifference, patch test satisfaction, and agreement between the subsequent Material Principal Co-rotation and P??I??C decomposition methods that produce the intermediary stress/strain fields. The encompassing theory has wide applicability owing to its fundamental divergence from conventional mechanics, it offers non-trivial outcomes when applied to even very simple problems and its use of not the Eulerian, Lagrangian but the Intrinsic Frame generates previously unreported results in strongly orthotropic continua.