Dissertations / Theses on the topic 'Shearing'

The frictional behavior of soil-construction material interfaces is of significant importance in geotechnical engineering applications such as retaining structures, pile foundations, geosynthetic liners, and trenchless technologies. Since most failures initiate and develop on the interfaces, special attention is required to predict the capacity of these weak planes in the particular application. Pipe-jacking and microtunneling technologies are being more widely used over the past decade and there is significant interest to predict the jacking forces and jacking distances achievable in order to achieve more efficient design and construction. This study focuses on the evaluation of the frictional characteristics and factors affecting the shear strength of pipe-soil interfaces. Eight different pipes made from fiber reinforced polymer (FRP), polycrete, steel, concrete, and vitrified clay were tested in the experimental program. For this purpose, a new apparatus was designed to conduct conventional interface direct shear testing on pipes of different curvature. This device allows coupons cut from actual conduits and pipes to be tested in the laboratory under controlled conditions. The apparatus includes a double-wall shear box, the inner wall of which is interchangeable to allow for testing against surfaces of different curvatures. By considering a narrow width section, the circular interface of pipes was approximated with a surface along the axial direction and the boundary is defined by the inner box. Roughness tests were performed using a stylus profilometer to quantify the surface characteristics of the individual pipes and relate these to the interface shear behavior. The surface topography showed different degrees of variability for the different pipes. To extend the range of roughness values tested and force the failure to occur in the particulate media adjacent to the interface, two artificial pipe surfaces were created using rough sandpapers. Interface shear tests were performed using the new apparatus with air-pluviated dense specimens of Ottawa 20/30 sand. Additional tests were performed using Atlanta blasting sand to evaluate the effect of particle angularity. The effect of normal stress and relative density were also examined. The interface strength was shown to increase with surface roughness and finally reach a constant value above a certain critical roughness value, which corresponded to the internal strength of the soil itself. This represented the failure location moving from the interface into the soil adjacent to the interface. Both the strength and the shearing mechanism were thus affected by the surface topography. It was also shown that the interface shear strength was affected by particle angularity, relative density and normal stress.

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2018.
This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student-submitted PDF version of thesis. Pages 100 and 101 blank.
Includes bibliographical references.
Microbial biofouling occurs when a biofilm adheres to materials involved in liquid transport causing economic loss through corrosion and drag losses on ship hulls, and in oil and food distribution. Microorganisms interacting with surfaces under these open channel flows contend with high shear rates and active transport to the surface. The metallic surfaces they interact with carry charge at various potentials that are little addressed in literature. We demonstrate for the first time that mass transport limiting current, chronoamperometry, and cyclic voltammetry in a rotating disk electrode are ideal for studying adhesion of microbes to metallic surfaces under shear. We study the adhesion of Escherichia coli, Bacillus subtilis, and 1 μm silica microspheres over a range of shear stresses. Our results agree with literature on red blood cells in rotating disk electrodes and deposition rates of B. subtilis and E. coli from optical systems, and show that we can quantify changes in active electrode area by bacteria adhesion and protein secretion.
Our methodology measures changes in area instead of mass simultaneously providing measurements of the protein binding step that initiates biofilm formation. Unlike fluorescence microscopy, these methods are in vivo and apply to a larger range of problems than on-chip flow devices. We also use the rotating disk system to present the first study of how electroactive biofilms adapt to shear stress over time. These biofilms are unique in that they do not rely on electron acceptor diffusion as they are "wired" to the electron acceptor, leading to thicker biofilms. Furthermore, it is possible to use the current produced by the biofilms as a proxy for metabolic respiration. We measure current, open circuit potential, electron diffusion current, electrochemical impedance, and formal potential throughout the course of seven days of Geobacter sulfurreducens forming a biofilm on a graphite disk exposed to three different shear stresses (1, 0.1, 0.01 Pa) and fixed mass flux. We image the resulting biofilm to measure biofilm thickness, porosity, and surface roughness. We find that high shear rates lead to faster start-up times and higher current, and by proxy higher metabolic rates, at the cost of long term sustainability of this current. We also find that there was no statistical difference in thickness or surface roughness between biofilms of different stresses. Similar to previous work, we propose that the lack of stability is due to the absence of waste removal. Our results are the first to show that the rotating disk system can be used investigate biofilm's development, metabolism, and structure from initiation to decay in vivo under fluid shear stress and electrical stress conditions that occur in our engineered environments. Future work using this system can include increased sampling frequency to understand start-up behavior and analysis of how mixed cultures modify adhesion, start-up respiration rates, and waste removal.
by Akhenaton-Andrew Dhafir Jones, III.
Ph. D.

Parabolic flows are slowly chaotic flows for which nearby trajectories diverge polynomially in time. Examples of smooth parabolic flows are unipotent flows on semisimple Lie groups and nilflows on nilmanifolds, which are both well-understood. Beyond the homogeneous set-up, however, very little is known for generic smooth parabolic flows and a general theory about their ergodic properties is missing. In this thesis, we study three classes of smooth, non-homogeneous parabolic flows and we show how a common geometric shearing mechanism can be exploited to prove mixing. We first establish a quantitative mixing result in the setting of locally Hamiltonian flows on compact surfaces. More precisely, given a compact surface with a smooth area form, we consider an open and dense set of locally Hamiltonian flows which admit at least one saddle loop homologous to zero and we prove that the restriction to any minimal component of typical such flows is mixing. We provide an estimate of the speed of the decay of correlations for a class of smooth observables. We then focus on perturbations of homogeneous flows. We study time-changes of quasi-abelian filiform nilflows, which are nilflows on a class of higher dimensional nilmanifolds. We prove that, within a dense set of time-changes of any uniquely ergodic quasi-abelian filiform nilflow, mixing occurs for any time-change which is not cohomologous to a constant, and we exhibit a dense set of explicit mixing examples. Finally, we construct a new class of perturbations of unipotent flows in compact quotients of SL(3,R) which are not time-changes and we prove that, if they preserve a measure equivalent to Haar, then they are ergodic and, in fact, mixing.

Tese (doutorado) - Universidade Federal de Santa Catarina, Centro Tecnológico. Programa de Pós-Graduação em Engenharia Mecânica.
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A evolução das câmeras CCD e sistemas de processamento de imagens viabilizaram o desenvolvimento da holografia digital. O filme fotográfico pôde ser substituído por sensores CCD de elevada resolução, capazes de registrar os complexos padrões de interferência. A reconstrução do holograma é efetuada inteiramente de forma digital, sendo possível registrar com precisão pequenos campos de deslocamentos e deformações. Na holografia clássica, assim como na holografia digital e na holografia digital complexa um fator limitante que inviabiliza medições em campo é a elevada sensibilidade às perturbações externas do arranjo holográfico. É fundamental que o arranjo seja isolado de perturbações externas, o que torna a prática destas medições restrita a um ambiente de laboratório. A nova configuração proposta neste trabalho utiliza um interferômetro "shearing" para produzir uma onda de referência implícita. A informação de intensidade e a informação de fase são utilizadas para a reconstrução da frente de onda. O holograma resultante deste processo está sendo denominado "holograma digital complexo". Este trabalho apresenta em detalhes o princípio da nova configuração. Diferentes algoritmos foram criados e testados para o cálculo do "holograma digital complexo". Experimentos monitorados foram realizados e demonstram a viabilidade da técnica para futuras aplicações para a medição de deslocamentos.

In manufacturing industry cutting of sheet metals is an everyday occurrence. With this in mind hand tool design is limited by empirical conventions for tool clearance, in the range of 4.5% to 8%. Conventional cutting force calculations and tool clearance calculations exist in reference material and can easily be calculated. These conventions are based on shear theory for force and experimental data for tool clearance. By applying these conventions to an FEM model for common engineering alloys of thicknesses between .020" and .080", and analyzing it the resulting stress fields and tool displacements trends in the increase of tool displacement required for the same stress state for all tool clearances. Cohesive zone placement based on first analysis leads to describing the failure of the material cutting process. Traction separation laws describing cohesive elements can accurately describe the cutting of sheet metals. For the 6061-T6 aluminum, 1020 steel, 4340 steel, and 302 stainless the optimum tool clearance discovered through the cohesive zone FEM model is shown to be 3.8% to 8.3%. This information can be used for extrapolating the optimum clearances for other thicknesses of the materials, and the model can be expanded to encompass a larger material set.

Simultaneous measurements of the velocity profile and turbulence were made at 4 heights within 2 m of the sea bed in the Eastern Irish Sea. A photographic unit was also deployed to observe sediment motion. The design, construction and performance of the instruments are described and the results from 36 trials, for a variety of bedforms and water depths of 8 to 50 m, are discussed. The velocity profile was recorded by means of Aanderaa rotors and the velocity fluctuations with e.m. heads. Their measurements, according to flume calibrations, were accurate to ±l%. Angular corrections were necessary to compensate for the loss in response when the turbulence rig was poorly orientated with respect to the mean flow direction. The minimum in situ velocity was 20 cm s-l, at which speed inertial 'pumping' of the rotors by turbulent fluctuations was estimated to produce overreading by - 1 cm s-l. At speeds above 30 cm s-l this effect was negligible. The resolution of the e.m. heads was at least 5.0 mm s-l, as determined by the noise level, and d.c. drift less than 1.0 mm s-l over periods of up to 17 hours. Data were recorded on 9 track tape aboard ship for later analysis onshore. The measurements were made in a bottom boundary layer which could be decribed as accelerating, non-rotational, hydrodynamically rough, neutrally stratified and comprised a layer of constant Reynolds stress. The stress, as determined from the log-profiles, either uncorrected or corrected for acceleration, was observed to be significantly greater (- 26%) than that determined by eddy correlation techniques. This could not be attributed to uncertainties introduced by misalignment of the e .m. heads, or inadequate correction for cospectral losses. Doubt was cast on the validity of von Karmann's constant (KO) = 0.4, with a more appropriate value apparently being closer to 0.35. KO and u*2/-U7""WTexhibited no dependence on bedform or sediment type, except in one case, where high ratios corresponded to high zo's. Evidence of a tidal hysteresis of stress was observed at one station only. Apparent Zo minima at peak tidal velocities were, for the most part, attributed to the non-removal of accelerating effects when applying the log-law. Initially high values of zo' when present, were supposed to be due to streamlining of bedforms with ;ncrnasing velocity. Zo and C100 varied from 0.02 - 0.25 and (2 - 3) x 10-3 respectively for mud, unrippled sand and various sand combinations. For gravel and rippled sand values they were 0.10 - 0.20 and (3 - 8) x 10-3. A comparison of events comprising 90% of the stress with movement of bed material, observed by the photographic unit, failed to reveal a Correlation. During periods of sediment motion events in which u' > 0 were dominant. For events comprising 90% of the stress, those in which u' < 0 and u' > 0 occurred in groups of 5 - 20. In addition, a number of coherent events, occuring between 5 - 12 times per minute independently of velocity, were observed between 100.0 and 172.5 cm above the bed.

Landslides cause significant damage worldwide and therefore epitomize the most important problems in geotechnical engineering. Hence, perceiving the mechanics involved in the deformation process of landslides is necessary for risk assessment. In addition to the resistance offered by basal shear surfaces, internal shearing also influences the stability and kinematics of compound landslides. For compound landslides, internal shearing is essential to develop feasible sliding mechanisms. The internal distortion is caused by the formation of shear bands that develop within the sliding mass. The strain localization is generally attributed to slope changes along the basal sliding surface (or topography) that constrain the strain field of the landslide. The development of these internal shear bands also controls the energy dissipation, and its distribution determines the final degradation of the material. This work focuses on the study of internal failure mechanisms that develop in compound landslides. A theoretical model of a compound landslide is numerically analyzed using the Material Point Method (MPM), a state-of-the-art numerical technique appropriate to model large deformation problems. The internal failure pattern is identified for different basal sliding geometries. Based on that, a generalized method is proposed to estimate the internal failure mechanism of bi-planar compound geometries. The material degradation and energy dissipation are evaluated in terms of the accumulated deviatoric strain and the reaction forces exerted by the landslide on a vertical wall. Moreover, preliminary studies are conducted to analyze the use of barriers as a mitigation strategy to counter landslide damage, and their efficiencies are investigated.
Master of Science
Landslides consist of movement of rock and debris down a slope. They cause substantial damage each year and therefore represent an important class of problems in geotechnical engineering. Understanding the deformation process and internal shearing pattern occurring in landslides is an important aspect for assessing the risk that a landslide poses. The internal shear is caused due to the formation of shear bands that develop within the mass flowing down the slope and originate at the points of slope change on an incline. These shear bands also affect the amount of energy dissipated and the degradation of flow material. In this work, the internal failure mechanism in landslides is analyzed and effects on landslide kinematics are studied. Material Point Method (MPM) is used to simulate slope instabilities which is an advanced numerical technique appropriate for modeling large deformation problems such as landslides. Several theoretical models of compound landslides are presented considering variation in geometry (roundedness), friction, and slope angle. A generalized failure mechanism of a landslide is proposed based on its geometry and physical parameters. Finally, accumulated strains and reaction forces impacted by moving mass on a wall are calculated for different landslide geometries, and subsequently correlated to energy dissipation material degradation. These results also serve as a precursor to studying the role of barriers in mitigating landslide damage.

Electronic Speckle Pattern Shearing Interferometry (ESPSI) or shearography has successfully been used in NDT for slope (δw/δx and/or δw/δy) measurement while strain measurement (δu/δx, δv/δy, δu/δy and δv/δx) is still under investigation This method is well accepted in industrial applications especially in the aerospace industry. Demand of this method is increasing due to complexity of the test materials and objects. ESPSI has successfully performed in NOT only for qualitative measurement whilst quantitative measurement is the current aim of many manufacturers. Industrial use of such equipment is being completed without considering the errors arising from numerous sources, including wavefront divergence. The majority of commercial systems are operated with diverging object illumination wavefronts without considering the curvature of the object illumination wavefront or the object geometry, when calculating the interferometer fringe function and quantifying data. This thesis reports the novel approach in quantified maximum phase change difference analysis for derivative out-of-plane (OOP) and in-plane (IP) cases that propagate from the divergent illumination wavefront compared to collimated illumination.

The operation of a grating lateral shear heterodyne interferometer as a wavefront sensor for atmospherically perturbed wavefronts is analyzed. A novel wavefront sensor design is given and its feasibility is proven by laboratory experiments. The applications in mind are closed-loop active optical systems for compensating atmospheric perturbations and open-loop atmospheric wavefront measuring device. The optical properties of the turbulent atmosphere are summed up and the resulting wavefront sensor requirements are given. Among them are the property of sell-referencing, high white light efficiency, independence of scintillation effects, and high spatial and temporal sampling rates. Then the general heterodyne grating shearing interferometer is introduced. A description of the phase measurement by the heterodyne process in the frequency domain has been derived. The heterodyne process is interpreted as convolutions of the signal with a pair of filter functions, which isolate a particular harmonic term of the signal and provide its phase. The representation of the convolutions in the frequency domain provides an elegant way to analyse the systematic errors of the heterodyning with general, non-sinusoidal signals. Also the random phase errors of the heterodyne process have been determined using Gaussian error propagation. An algorithm is derived to carry out the wavefront reconstructions from the measured differences on a square array of discrete data points. It is based on a modal expansion in complex exponentials, leading to a simple filtering operation in the spatial frequency domain. The algorithm provides unbiased reconstructions over the finite data set. It has minimal error propagation in a least squares sense. It is computationally efficient in that the number of operations required for a reconstruction is approximately proportional to the number of wavefront points, if a Fast-Fourier-Transform algorithm is used. Finally, a compact wavefront sensor design is described fulfilling the requirements posed by the turbulent atmosphere. It determines wavefronts at 24 by 24 points at a sampling rate of 60 Hz. A rms-wavefront error of better than λ/20 can be achieved with astronomical light sources of sixth stellar magnitude. Laboratory experiments proved the feasibility of the design.

A lot of fluids are more complex than water: polymers, paints, gels, ketchup etc., because of big particles and their complicated microstructures, for instance, molecule entanglement. Due to this structure complexity, some material can display that it is still in yielded state when the imposed stress is released. This is referred to as thixotropy. This dissertation establishes mathematical analysis on a thixotropic yield stress fluid using a viscoelastic model under the limit that the ratio of retardation time versus relaxation time approaches zero. The differential equation model (the PEC model) describing the evolution of the conformation tensor is analyzed. We model the flow when simple shearing is imposed by prescribing a total stress. One part of this dissertation focuses on oscillatory shear stresses. In shear flow, different fluid states corresponding to yielded and unyielded phases occur. We use asymptotic analysis to study transition between these phases when slow oscillatory shearing is set up. Simulations will be used to illustrate and supplement the analysis. Another part of the dissertation focuses on planar Poiseuille flow. Since the flow is spatially inhomogeneous in this situation, shear bands are observed. The flow is driven by a homogeneous pressure gradient, leading to a variation of stress in the cross-stream direction. In this setting, the flow would yield in different time scales during the evolution. Formulas linking the yield locations, transition width, and yield time are obtained. When we introduce Korteweg stress in the transition, the yield location is shifted. An equal area rule is identified to fit the shifted locations.
Ph. D.

Residual shear strength is a fundamental property of cohesive soils and is the governing parameter in many slope stability problems, particularly the reactivation of landslides. Traditionally, residual strengths are determined in the laboratory at slow drained rates of shearing using either shear boxes with reversals or ring shear apparatus. Many catastrophic landslides have been triggered by seismic loading inducing fast rates of shear. Interest has therefore developed in laboratory shear testing at faster rates and over greater displacements to establish fast residual shear strengths. This thesis presents results from testing using the Imperial College-Norwegian Geotechnical Institute Ring Shear Apparatus modified to conduct shearing at velocities up to 1 m/min. The variation of residual strengths as shear rate increases is investigated in association with soil grading and plasticity and also with the morphology of the shear zone. A novel set of undulating interfaces are used to investigate the influence of shear zone waviness. The research concludes that as shear rate is increased three types of fast residual shear strength variation may occur: (i) little variation from the slow residual shear strength, (ii) a continuous increase above the slow residual shear strength or (iii) an initial increase followed by a decrease to levels significantly below the slow residual shear strength. Increases in fast strength are attributed to particle disorientation and viscous effects. Falls in fast residual shear strength are attributed to the generation of positive pore water pressure in the shear zone, as a result of a pumping effect induced by wavy or inclined shear zones. Computational modelling of this pumping effect is undertaken using consolidation theory. Fast peak strengths and slow peak strengths after fast shearing are also investigated. Finally, the influence on slow residual shear strength of shear zones with undulations parallel to the shear direction are studied both mathematically, and using the Bromhead Ring Shear Apparatus.

Les excellentes propriétés électroniques du germanium limitées par la faible qualité isolante de son oxyde rendent le développement de nouveaux matériaux diélectriques nécessaires. En outre, la sensibilité du germanium requiert la création d'une couche passivante de surface pour le protéger. Bien que de nombreuses études soient réalisées pour le développement de nouveaux diélectriques inorganiques, ce projet de recherche en rupture concerne la conception, la réalisation et le développement de film mince diélectrique organique passivant sur le germanium pour des applications en nanoélectronique. Le travail réalisé porte principalement sur la synthèse de nouvelles molécules " push-pull " (systèmes conjugués linéaires portant de part et d'autres un groupe donneur et un groupe accepteur) et sur la fonctionnalisation du germanium. Plusieurs nouveaux systèmes donneur-accepteur ainsi que des systèmes conjugués linéaires contenant une fonction d'ancrage ont été synthétisés selon de nouvelles voies. En particulier, une série de dérivés azobenzène contenant différents accepteurs (groupes fluorés, pyridinium, nitro) et donneurs (amines, alcoxyl) ainsi que des fonctions d'ancrage variées (thiol, acide carboxylique, sel de diazonium, triazene) a été obtenue. En parallèle, la préparation et la fonctionnalisation de surfaces de germanium ont été étudiées. Un nouveau procédé permettant d'enlever l'oxyde natif de la surface et d'obtenir des surfaces halogénées de faible rugosité a été développé. Les substrats de germanium ont été fonctionnalisés par des thiols mais également par des sels de diazonium. Ce nouveau processus de greffage spontané a permis d'abaisser considérablement le temps de réaction (15 minutes de greffage spontané des sels de diazonium contre 3 jours pour la formation de monocouches auto-assemblées de thiols) tout en travaillant dans des conditions douces. Les films minces ainsi obtenus présentent une stabilité comparable à celles des monocouches de thiols. Des systèmes conjugués linéaires ont été greffés à la fois sous forme de thiol et sous forme de sels de diazonium afin de déterminer l'influence du noyau aromatique sur la formation du film et sur ses propriétés. Enfin, les systèmes " push-pull " ont également été greffés. Des premières études électroniques sur or avec les systèmes conjugués linéaires ont été réalisées. Ces études ont été étendues au germanium et laissent envisager des résultats significatifs avec les molécules " push-pull "
Despite its excellent electronic properties, germanium is limited by the low passivation of its oxide. Therefore, new dielectrics must be developed. Furthermore, germanium sensitivity requires the creation of a passivation layer on the surface. Even if numerous studies were carried out on new inorganic dielectrics, this research project concerns the design, the realization and the development of thin passivating organic dielectric films on germanium for nanoelectronics applications. This work principally involves the synthesis of new push-pull molecules (π-conjugated systems bearing a donor and an acceptor part) and germanium functionalization. New donor-acceptor systems and π-conjugated linear systems containing an anchoring group were synthesized through new ways. In particular, a series of azobenzene derivatives with different acceptors (fluorinated groups, pyridinium, nitro) and donors (amines, alkoxyl) and various anchoring groups (thiol, carboxylic acid, diazonium salt, triazene) was obtained. Meanwhile, preparation and functionalization of germanium surfaces was studied. A new process to etch the native oxide and obtain halogenated surfaces with low roughness was developed. Germanium substrates were then functionalized with thiol but also with diazonium salts. This new spontaneous grafting process considerably decreased the reaction time (15 minutes spontaneous grafting of diazonium salts against 3 days for self-assembled monolayers of thiol formation) in mild conditions. Thin films obtained present stability similar to the one of thiol monolayers. Π-conjugated linear systems were grafted both as thiol and diazonium salt to probe the influence of the aromatic core on the film formation and properties. Finally, push-pull systems were also grafted. Electronic studies on gold with π-conjugated systems were realized. These studies were extended to germanium and allow expecting significant results with push-pull molecules

After the turmoil of the 1890s shearing contractors eliminated some of the frustration from shearers recruitment. At the same time closer settlement concentrated more sheep in small flocks in farming regions, replacing the huge leasehold pastoral empires which were at the cutting edge of wool expansion in the nineteenth century. Meanwhile the AWU succeeded in getting an award for the pastoral industry under the new arbitration legislation in 1907. Cultural and administrative influences, therefore, eased some of the bitter enmity which had made the annual shearing so unstable. Not all was plain sailing. A pattern of militancy re-emerged during World War I. Shearing shed unrest persisted throughout the interwar period and during World War II. In the 1930s a rival union with communist connections, the PWIU, was a major disruptive influence. Militancy was a factor in a major shearing strike in 1956, when the boom conditions of the early-1950s were beginning to fade. The economic system did not have satisfactory mechanisms to cope. Unionised shearers continued to be locked in a psyche of confrontation as wool profits eroded further in the 1970s. This ultimately led to the wide comb dispute, which occurred as wider pressures changed an economic order which had not been seriously challenged since Federation, and which the AWU had been instrumental in shaping. Shearing was always identified with bushworker ‘mateship’, but its larrikinism and irreverence to authority also fostered individualism, and an aggressive ‘moneymaking’ competitive culture. Early in the century, when old blade shearers resented the aggressive pursuit of tallies by fast men engaged by shearing contractors, tensions boiled over. While militants in the 1930s steered money-makers into collectivist versions of mateship, in the farming regions the culture of self-improvement drew others towards the shearing competitions taking root around agricultural show days. Others formed their own contracting firms and had no interest in confrontation with graziers. Late in the century New Zealanders arrived with combs an inch wider than those that had been standard for 70 years. It was the catalyst for the assertion of meritocracy over democracy, which had ruled since Federation.

Doctor of Philosophy (PhD)
After the turmoil of the 1890s shearing contractors eliminated some of the frustration from shearers recruitment. At the same time closer settlement concentrated more sheep in small flocks in farming regions, replacing the huge leasehold pastoral empires which were at the cutting edge of wool expansion in the nineteenth century. Meanwhile the AWU succeeded in getting an award for the pastoral industry under the new arbitration legislation in 1907. Cultural and administrative influences, therefore, eased some of the bitter enmity which had made the annual shearing so unstable. Not all was plain sailing. A pattern of militancy re-emerged during World War I. Shearing shed unrest persisted throughout the interwar period and during World War II. In the 1930s a rival union with communist connections, the PWIU, was a major disruptive influence. Militancy was a factor in a major shearing strike in 1956, when the boom conditions of the early-1950s were beginning to fade. The economic system did not have satisfactory mechanisms to cope. Unionised shearers continued to be locked in a psyche of confrontation as wool profits eroded further in the 1970s. This ultimately led to the wide comb dispute, which occurred as wider pressures changed an economic order which had not been seriously challenged since Federation, and which the AWU had been instrumental in shaping. Shearing was always identified with bushworker ‘mateship’, but its larrikinism and irreverence to authority also fostered individualism, and an aggressive ‘moneymaking’ competitive culture. Early in the century, when old blade shearers resented the aggressive pursuit of tallies by fast men engaged by shearing contractors, tensions boiled over. While militants in the 1930s steered money-makers into collectivist versions of mateship, in the farming regions the culture of self-improvement drew others towards the shearing competitions taking root around agricultural show days. Others formed their own contracting firms and had no interest in confrontation with graziers. Late in the century New Zealanders arrived with combs an inch wider than those that had been standard for 70 years. It was the catalyst for the assertion of meritocracy over democracy, which had ruled since Federation.

The thesis presents a design of a progressive cutting tool for the production of shaped blanks from sheet metal Usibor 1500 (22MnB5) with a thickness of 1.5 mm. The tool is designed by using CATIA V5 software in cooperation with Žďas, a.s. company. Based on the literature review of the cutting process, cutters were designed, shear clearance and order of operations in the tool were determined. The proposed cutting tool consists of both manufactured and standardized parts. Tool parts fall out of the chute onto the conveyor belt. The tool is designed to operate on an AIDA 1000 excentric press with a nominal force of 10,000 kN. Cutters that are not standardized are made of tool steel and heat treated according to drawing documentation.

Accretion discs efficiently transport angular momentum by a wide variety of as yet imperfectly understood mechanisms, with profound implications for the disc lifetime and planet formation. We discuss two different methods of angular momentum transport: first, generation of acoustic waves by mixing of inertial waves, and second, the generation of a self-sustaining magnetic field via the magnetorotational instability (MRI) which would be a source of dissipative turbulence. Previous local simulations of the MRI have shown that the dynamo changes character on addition of vertical stratification. We investigate numerically 3D hydrodynamic shearing waves with a conserved Hermitian form in an isothermal disc with vertical gravity, and describe the associated symplectic structure. We continue with a numerical investigation into the linear evolution of the MRI and the undular magnetic buoyancy instability in isolated flux regions and characterise the resultant quasi-linear EMFs as a function of height above the midplane. We combine this with an analytic description of the linear modes under an assumption of a poloidal-toroidal scale separation. Finally, we use RAMSES to perform full MHD simulations in a zero net flux shearing box, followed by spatial and a novel temporal averaging to reveal the essential structure of the dynamo. We find that inertial modes may be efficiently converted into acoustic modes for "bending waves", despite a fundamental ambiguity in the inertial mode structure. With our linear MRI and the undular magnetic buoyancy modes we find the localisation of the instability high in the atmosphere becomes determined by magnetic buoyancy rather than field strength for small enough azimuthal wavenumber, and that the critical Alfven speed below which the dynamo can operate increases with increasing distance from the midplane. We calculate analytically quasi-linear EMFs which predict both a vertical propagation of toroidal field and a method for creation of radial field. From our fully nonlinear calculations we find an electromotive force in phase with the toroidal field, which is itself 3π/2 out of phase with the radial (sheared) field at the midplane, and good agreement with our quasi-linear analytics. We have identified an efficient mechanism for generating acoustic waves in a disc. In our investigation of the accretion disc dynamo, we have reproduced analytically the EMFs calculated in our simulations, given arguments based on the phase of relevant quantities, several correlation integrals and the scalings suggested by our analytic work. Our analysis contributes significantly to an explanation for the dynamo in an accretion disc.

Non-corrosive reinforcement of concrete provides great potential for reducing life cycle costs (LCC) of highway infrastructure (bridge decks and columns, light-standards, dividers) and concrete structures near water (piers, retaining walls, platforms). This is especially important in areas where salts are common (cold weather road salting, coastal regions) and is achieved by extending the life of structures and the period between major repairs. Costs of infrastructure rehabilitation due to corrosion of reinforcement are estimated to be $1.2 billion dollars in Ontario in the next few years, and up to 40% of all annual infrastructure costs in the province of Quebec. Efforts to reduce the frequency of repair and replacement of ageing structures include using epoxy coating of the reinforcing bar (rebar), cathodic protection, alternate types of steel and fibre reinforced polymer (FRP) rebar. Of these, FRP rebar appears to be the most promising. The limitation of FRP rebar is the low maximum strain and linear behaviour up to failure. Prior attempts at increasing the ductility and producing non-linear behaviour have had limited success. Maximum strain remains limited to that of the highest strain fibres available. Pseudo-ductility has been achieved by combining multiple fibre types having different material properties. The work described in this thesis focussed on non-traditional methods for achieving ductility in FRP rebars by taking advantage of the frictional interface of two materials. Two methods were tested. The first employed a solid inner-core with an over-wrap cut at regular intervals and relied on the rebar pulling out of the concrete at sustained load. Rods were tested in concrete beams under bending loads. Sustained load was achieved for significant pull-out. The second method combined continuous fibres with discontinuous meso-rods wherein the continuous fibres provide initial stiffness and maximum strength and the discontinuous meso-rods provide high-ductility via fibre pull-out. A concept model using aligned short steel fibres was manufactured and tested. Load-displacement behaviour showed substantial local elongation. Prototype models using carbon fibres were manufactured and tested. Specimens showed evidence of fibre pull-out. Future specimens should employ an intermediate material with a controlled and repeatable shear strength for the interface.

Shearing is the process where sheet metal is mechanically cut between two tools. Various shearing technologies are commonly used in the sheet metal industry, for example, in cut to length lines, slitting lines, end cropping etc. Shearing has speed and cost advantages over competing cutting methods like laser and plasma cutting, but involves large forces on the equipment and large strains in the sheet material. The constant development of sheet metals toward higher strength and formability leads to increased forces on the shearing equipment and tools. Shearing of new sheet materials imply new suitable shearing parameters. Investigations of the shearing parameters through live tests in the production are expensive and separate experiments are time consuming and requires specialized equipment. Studies involving a large number of parameters and coupled effects are therefore preferably performed by finite element based simulations. Accurate experimental data is still a prerequisite to validate such simulations. There is, however, a shortage of accurate experimental data to validate such simulations. In industrial shearing processes, measured forces are always larger than the actual forces acting on the sheet, due to friction losses. Shearing also generates a force that attempts to separate the two tools with changed shearing conditions through increased clearance between the tools as result. Tool clearance is also the most common shearing parameter to adjust, depending on material grade and sheet thickness, to moderate the required force and to control the final sheared edge geometry. In this work, an experimental procedure that provides a stable tool clearance together with accurate measurements of tool forces and tool displacements, was designed, built and evaluated. Important shearing parameters and demands on the experimental set-up were identified in a sensitivity analysis performed with finite element simulations under the assumption of plane strain. With respect to large tool clearance stability and accurate force measurements, a symmetric experiment with two simultaneous shears and internal balancing of forces attempting to separate the tools was constructed. Steel sheets of different strength levels were sheared using the above mentioned experimental set-up, with various tool clearances, sheet clamping and rake angles. Results showed that tool penetration before fracture decreased with increased material strength. When one side of the sheet was left unclamped and free to move, the required shearing force decreased but instead the force attempting to separate the two tools increased. Further, the maximum shearing force decreased and the rollover increased with increased tool clearance. Digital image correlation was applied to measure strains on the sheet surface. The obtained strain fields, together with a material model, were used to compute the stress state in the sheet. A comparison, up to crack initiation, of these experimental results with corresponding results from finite element simulations in three dimensions and at a plane strain approximation showed that effective strains on the surface are representative also for the bulk material. A simple model was successfully applied to calculate the tool forces in shearing with angled tools from forces measured with parallel tools. These results suggest that, with respect to tool forces, a plane strain approximation is valid also at angled tools, at least for small rake angles. In general terms, this study provide a stable symmetric experimental set-up with internal balancing of lateral forces, for accurate measurements of tool forces, tool displacements, and sheet deformations, to study the effects of important shearing parameters. The results give further insight to the strain and stress conditions at crack initiation during shearing, and can also be used to validate models of the shearing process.

Existing theories for the mechanical response of particle fluid mixtures have been reviewed and extended. They are made appropriate to geometries in which the dominant loading is a shearing one. The theories are then applied to the description of filtration experiments (these were performed by researchers dn a parallel research programme at Loughborough University). Two limits are distinguished: one in which particles experience a strong double layer interaction and one in which the particles are neutral and the fluid is the only significant force-mediating medium. The existing theories that have been reviewed and used are the quasi-static two-phase continuum mechanics framework (including seepage effects), the granular temperature theory for neutral particles and the common consolidation theory for strongly interacting particles. To extend these general theories - and especially to enter reliable constitutive relations - a micromechanical analysis is carried out and methods are developed to arrive at expressions for bulk properties. An analysis is performed of the response to a small localised fluctuation in either stress or solidosity of a particle-fluid mixture under arbitrary mean loading conditions. This analysis leads to a condition for stability of a mixture in terms of the solidosity sensitivity of the particle pressure and the solidosity sensitivity of the viscous constitutive parameters of the mixture given a mean loading regime. In the analysis it is recognised that a slurry in motion (especially shear) will always experience fluctuations. Two applications of the stability analysis are then presented. First it is recognised that homogenisation is impossible when the system is unstable. Second the border between a stable (packed) region and a free flowing region is defined by the edge of the stability condition, as made appropriate to the prevailing loading conditions. This piece of fundamental analysis is then used to describe filtration experiments, notably ones in which shear plays a distinctive role - these are torsion shear filtration and crossflow filtration. In order to analyse torsion shear filtration a calculation is carried out of a Newtonian fluid in a cylindrical vessel, loaded at the top by a rotating piston. A range of result is obtained: flow in an infinite cylinder, flow in a cylinder of finite length and flow in a finite cylinder with two immiscible fluids, occupying various sections of the cylindrical domain. The latter problem is particularly relevant to the torsion shear filtration problem as it shows that no significant shearing stress reaches, the cake until the fluid region near the piston is of the order of magnitude of the particle size of the mixture. Once shear can penetrate the cake the effects of it are noticed in that in a stable heterogeneous medium structures formation takes place in the direction of the major principal stress, implying that the greater the shear that is applied the greater the angle at which structures form. Then a calculation is presented to demonstrate the reduction in uniaxial stiffnes due to structures formation and the experimental result is recovered that for neutral particles cakes becoine denser when the shear is increased. This result is qualitative, though quantitative formulas are presented. The latter require parameters such as an estimate of the magnitude of the stiffness fluctuations that are hard to determine from current experiments. For double layer interacting particles the effects of shear are noticed at an earlier stage in the filtration process as particle interactions transmit the forces exerted externally on the mixture. The overall stiffness due to shearing is then estimated (stability is here required) and it is shown that the normal stress on the medium is reduced due to the fluctuations induced by the shearing. A lattice-Boltzmann, simulation of the same configuration confirms this interesting result. A crossflow setup has been analysed. A somewhat simplified one dimensional investigation is presented. The key point is that the edge of the cake near the septum is defined by the edge of stability analysis and this piece of information enables' a full survey of experimental results with a wide range of process paraméters (feed solidosity, crossflow velocity, crossflow pressure, particle type, pH). Two key experimental parameters are predicted: the end of filtration filtrate flow and time constant with which this end stage is reached. Double layer interacting particles and neutral particles have been explored. Some key findings pertaining especially to cases of thisn cakes are as follows. Double layer interacting particles: the end of filtration filtrate flux depends on the ratio of the crossflow velocity and feed solidosity only. The time constant depends Existing theories for the mechanical response of particle fluid mixtures have been reviewed and extended. They are made appropriate to geometries in which the dominant loading is a shearing one. The theories are then applied to the description of filtration experiments (these were performed by researchers dn a parallel research programme at Loughborough University). Two limits are distinguished: one in which particles experience a strong double layer interaction and one in which the particles are neutral and the fluid is the only significant force-mediating medium. The existing theories that have been reviewed and used are the quasi-static two-phase continuum mechanics framework (including seepage effects), the granular temperature theory for neutral particles and the common consolidation theory for strongly interacting particles. To extend these general theories - and especially to enter reliable constitutive relations - a micromechanical analysis is carried out and methods are developed to arrive at expressions for bulk properties. An analysis is performed of the response to a small localised fluctuation in either stress or solidosity of a particle-fluid mixture under arbitrary mean loading conditions. This analysis leads to a condition for stability of a mixture in terms of the solidosity sensitivity of the particle pressure and the solidosity sensitivity of the viscous constitutive parameters of the mixture given a mean loading regime. In the analysis it is recognised that a slurry in motion (especially shear) will always experience fluctuations. Two applications of the stability analysis are then presented. First it is recognised that homogenisation is impossible when the system is unstable. Second the border between a stable (packed) region and a free flowing region is defined by the edge of the stability condition, as made appropriate to the prevailing loading conditions. This piece of fundamental analysis is then used to describe filtration experiments, notably ones in which shear plays a distinctive role - these are torsion shear filtration and crossflow filtration. In order to analyse torsion shear filtration a calculation is carried out of a Newtonian fluid in a cylindrical vessel, loaded at the top by a rotating piston. A range of result is obtained: flow in an infinite cylinder, flow in a cylinder of finite length and flow in a finite cylinder with two immiscible fluids, occupying various sections of the cylindrical domain. The latter problem is particularly relevant to the torsion shear filtration problem as it shows that no significant shearing stress reaches, the cake until the fluid region near the piston is of the order of magnitude of the particle size of the mixture. Once shear can penetrate the cake the effects of it are noticed in that in a stable heterogeneous medium structures formation takes place in the direction of the major principal stress, implying that the greater the shear that is applied the greater the angle at which structures form. Then a calculation is presented to demonstrate the reduction in uniaxial stiffnes due to structures formation and the experimental result is recovered that for neutral particles cakes becoine denser when the shear is increased. This result is qualitative, though quantitative formulas are presented. The latter require parameters such as an estimate of the magnitude of the stiffness fluctuations that are hard to determine from current experiments.
For double layer interacting particles the effects of shear are noticed at an earlier stage in the filtration process as particle interactions transmit the forces exerted externally on the mixture. The overall stiffness due to shearing is then estimated (stability is here required) and it is shown that the normal stress on the medium is reduced due to the fluctuations induced by the shearing. A lattice-Boltzmann simulation of the same configuration confirms this interesting result. A crossflow setup has been analysed. A somewhat simplified one dimensional investigation is presented. The key point is that the edge of the cake near the septum is defined by the edge of stability analysis and this piece of information enables a full survey of experimental results with a wide range of process parameters (feed solidosity, crossflow velocity, crossflow pressure, particle type, pH).

The aim of the thesis is the design of the production process and tools for production of two grooves in coats of concrete clamp. Shell anchors are made of longitudinally welded stainless steel tubes 17 240. The size of the production of all types of shell of concrete clamps is 18 000 PCs per year. The number and the dimensions of grooves in the coats of anchors were determined on the basis of a practical verification. To the present day the grooves are made by cutting on a band saw, which is little productive and on finishing operations demanding way. The grooves in the coats of anchors will be newly manufactured by technology of shearing, which was a literary study. On the basis of the calculations was selected for the production a hydraulic press of CUPS 25 D. The grooves will be produced on the newly designed shearing tool. Work is carried out by technical-economic evaluation, which compares the current technology of production with the newly proposed technology. Part of the thesis is drawing documentation of coats of concrete clamps of all dimensions and drawing documentation of shearing tool.

Geotechnical design relies on correct interpretation of field observations from site investigation, full scale testing and laboratory element strength tests. A wide spectrum of applied shear strain rates are adopted which have the potential to generate conflicting soil strength parameters. Modern geotechnical applications frequently operate at significantly higher levels of applied shear strain rate than traditional construction methods. This can often lead to overestimation of strength parameters and thus caution must be exercised when interpreting data to prevent unsafe design. A new Rowe Cell-Vane Shear apparatus has been developed to investigate the relationship between undrianed shear strength and rate effects. This apparatus is capable of providing a torque up to 20Nm and rotation rates from O.5mm/s to 400mm/s. The consolidometer was 254 mm in diameter and 126 mm high, with an aluminium base plate designed to accommodate four vanes during consolidation. Rigorous calibrations have been conducted to account for vane shaft friction and motor lag time. Three design mixes were established by using a mixture of Speswhite Kaolin, a silica flour (Oakamoor HPF3) and a silica sand (Buckland P30) at different percentages. The design mixes covered a range of Atterberg limits from low to high plasticity. Functionality of the newly developed apparatus is confirmed through the test results. Rate effects were observed for the peak undisturbed, residual undisturbed and residual disturbed strengths. The rate effects on peak undisturbed shear strength increased with decreasing LI. The results from three different soils at similar liquidity indices indicated that the rate effect was dependant on liquidity index not the plastic limit or liquid limit.

Dunlop Aerospace Braking Systems Plc. (DABS) is an international leading aircraft wheel and brake manufacturer. DABS had two wheel units, which were causing qualification problems in terms of fatigue cracking. Loughborough University (LU) proposed a novel robust non-contact, and non-destructive optical Shearographic Sensor System (SSS) for measuring and studying aircraft wheel deformation and behaviour when subjected to large static structural loading, with the aim to: i) Develop a novel robust optical sensor system for routine industrial use. ii) Demonstrate the novel and routine implementation for large scale structural loading/testing. iii) Identify high deformation concentration areas on aircraft wheel structures. iv) Provide routine quantitative data to DABS. v) Develop the novel understanding of error propagation, resolution and repeatability of the interferometer design. A series of laboratory experiments were conducted to demonstrate the functionality, repeatability, and reliability of the instrument to produce valid deformation data in a controlled environment in the optical metrology laboratory at LU. The SSS produced valid high quality deformation data using a Square Clamped Plate (SCP). The data was calibrated and correlated using a Linear Variable Differential Transducer (LVDT) system. The repeatability and reliability tests showed a high repeatability range of the SSS in the controlled environment of (5.95x10-8m) in the case of 10mm Horizontal lateral shear with Collimated laser illumination (10HC) and (1.22x10-7m) in the case of 10mm Vertical lateral shear with Collimated laser illumination (10VC). This accelerated the transfer of the SSS into the industrial environment at DABS, where heavy testing machineries operate routinely, which generated additional error and variation sources to the data produced by the SSS. A series of deflation/ inflation pressure and static structural load tests were completed on Boeing757 and BAe 146 wheel. The results showed that the data quality was sufficiently good to allow DABS to validate the FE model of the wheel, in spite of the surrounding uncontrolled and disturbing environment. Further repeatability and reliability tests were completed on the BAel46 wheel. This was to identify and discuss the engineering reality of the repeatability, reproducibility, and accuracy of the SSS, The results showed that the SSS achieved a better repeatability range in the laboratory in comparison to the industrial workplace at DABS, whichwas (1.60xl0-5m) and (1.08xl0-5m) forthe same shearing directions. As a result, DABS was provided with large amount of numerical data from the Boeing757 and the BAe142 wheels, in partial derivative and displacement format, ready for FE model validation. Commercial exploitation of the SSS into other industrial sectors and for various applications was completed via Laser Optical Engineering Ltd.

Motion parallax is often considered to be an inherently ambiguous cue to depth. Despite the theoretical ambiguity associated with the pattern of retinal image motion, motion parallax generally evokes compelling three-dimensional (3-D) percepts and for this reason is regarded as an important source of 3-D information. Certain studies have indicated, however, that a parallax surface that contains a given amount of simulated depth is often perceived to rotate, rather than simply remain stationary, as the observer moves. This thesis provides an experimental investigation of the factors which influence perceived rotation and shearing in motion parallax surfaces. In a series of psychophysical experiments, the cue of self-produced motion parallax was manipulated in order to provide insights into the mechanisms underlying the perception of 3-D surfaces. Since larger parallax motions often produce the impression of rotation, the "transition point" between stationarity and rotation was measured as a function of several factors. The maximum motion gradient was shown to be the principal determinant of this transition point surfaces with a steep motion gradient were perceived to rotate at lower relative motion amplitudes than surfaces with shallow motion gradients. Vertical perspective information played a smaller role. The transition point also fell with increasing viewing distance. At even higher amplitudes, parallax surfaces can appear nonrigid or even lacking in all 3-D structure, and the experiments reported have measured the transition points between each of the different perceptual zones. A model was introduced in order to determine whether the perceived magnitudes of depth and rotation of sinusoidal parallax surfaces were in accordance with geometric constraints. Qualitative support was found for a trade-off between depth and rotation when corrugation frequency or stimulus size was manipulated. Results were less conclusive when a dynamic vertical perspective cue was varied. A similar model was applied to the perceived magnitudes of depth and shearing in square wave surfaces. The relationship between these attributes was less clear-cut. The perceived rotation of sinusoidal surfaces increased with increasing viewing distance; possibly due to a decreasing propensity of the observer, with increasing viewing distance, to attribute the vertical perspective changes to self-motion. In sum, these experiments demonstrate the importance of motion gradients and vertical perspective information in the perception of motion parallax surfaces, and suggest that the surfaces are generally perceived in qualitative accord with the totality of visual information present (Helmholtz, 1909).

Drops are self-contained systems which do not need solid walls as surface tension provides containment. Solid walls can have associated issues such as sorption, chemical and electrostatic effects which can complicate the study of scientific phenomenon such as amyloid fibril formation. Amyloid fibrils are aggregates of protein that are generally associated with numerous neurodegenerative diseases, including Alzheimer's and Parkinson's. The containerless nature of drops motivated the ring-sheared drop (RSD) which is a platform for shearing of constrained drops through the action of surface shear viscosity. The ring-sheared drop will be used to study amyloidogenesis by utilizing the microgravity environment aboard the international space station (ISS) since microgravity enables testing with large-scale drops. Recently, the ring-sheared drop was also considered or analyzed for mixing within drops. This work presents a study of formation and shearing of constrained drops which are key scientific phenomena associated with the RSD. The formation of constrained drops as in the case of RSD was investigated both experimentally and computationally. Microgravity experiments performed aboard parabolic flights demonstrated successful formation and pinning of 10 mm diameter water drops. The computational model developed to simulate drop growth was validated against Earth-based (1 g) experiments. Also, it was found that the same computational model was able to predict the drop formation in microgravity. The shearing of constrained drops and resulting mixing within the drop were studied through numerical simulations of a 2.5 mm diameter drop. For benchmarking purposes, the numerical method used here was implemented on a knife-edge surface viscometer previously reported and the results were reproduced. The numerical results for the RSD showed that interfacial shear created by the differential rotation of the contact rings can produce azimuthal (primary) flow and meridional (secondary) flow through the action of surface shear viscosity. Further, the numerical results also demonstrated that the secondary motion effectively causes mixing within the drop. Such a surface shear viscosity based droplet mixing was found to be faster by at-least an order of magnitude as compared to the mixing produced in a diffusion-only (quiescent) case. Mixing produced by three configurations of the ring-sheared drop was assessed, namely steadily-driven single ring, oscillatory-driven single ring and steadily-driven counter rotating rings. Steadily-driven single ring produced the fastest mixing among the three configurations for the same Reynolds number (Re). However, at Re ₁ = 50, a range of oscillation frequencies 1.4 < ω < 9 was discovered for which the oscillatory-driven single ring case resulted in a faster mixing than the steadily-driven ring case. Hence, oscillatory driving can be tuned to achieve faster mixing than the steady driving. Steadily-driven counter rotating rings produced a slower mixing than one ring rotating steadily. Overall, it was concluded that RSD is an effective droplet mixer suitable for containerless applications in biophysics and bioprocessing.

The industrial practice of grain refinement of aluminium alloys involves the addition of inoculant particles to initiate alpha-aluminium grains at small undercoolings. This results in a uniformly fine, equiaxed as-cast microstructure and is commonly achieved using Al-Ti-B additions. The phase responsible for initiation of grains in aluminium melts inoculated with Al-Ti-B was determined during the 1990s; since that time, scientific understanding of grain refinement has advanced rapidly. However, one of the main problems of addition inoculants is impurities which is added to the melt and may affect the desired characteristics of the product. With regards to this problem other methods of refinement and the mechanisms of refining have not been fully understood and prediction of as-cast Microstructures in aluminium alloys has much scope for improvement. In this thesis: 1-Factors in establishing equiaxed microstructure were analysed and the origin of equiaxed grains were explored. Then the nucleation process and the involved mechanisms were investigated in depth and control of nucleation process to achieve a fine and uniform structure was set as target. 2-Refinement of microstructure with introduction of shearing was evaluated and the process of refinement in the mushy zone (semisolid state) as a base line was established. Then introduction of shearing above liquidus as a development was analysed and outstanding refinement was seen with shearing above liquidus which have not been investigated properly elsewhere. 3- The mechanisms of refinement by introducing shearing were investigated and the refining mechanisms below and specifically above liquidus were investigated systematically. As results an appropriate understanding about the mechanisms of nucleation and refinement above liquidus was established. 4- Finally, with simulation the most dominant factor in approaching fine grain size by applying shear was identified and the results of experimental examination was verified by simulation.

Over the past 50 years, experimental studies have repeatedly demonstrated that the mechanical behaviour of sand is sensitive to the material fabric, i.e., the arrangement of the grains. Up until now there have been relatively few attempts to describe quantitatively the fabric of sands. In fact, most of our understanding of the link between the particle movements and interactions and the macro-scale response of granular materials, including sand, comes from discrete element modelling (DEM) and experiments on “analogue” sands with simple, idealized shapes. The aim of this study had been to describe quantitatively the particle morphology and fabric of real sand and their evolution under loading. The material investigated was Reigate sand (from Southeast England), a geologically old sand which, in its intact state, exhibits significant grain interlocking and no bonding. To explore the effects of fabric on the mechanical response of the soil, intact and reconstituted specimens both having similar densities were tested under triaxial compression. The specimens were impregnated with an epoxy resin at three different stages of shear deformation and small cores from each specimen were scanned using X-ray micro-tomography. Different systems and scanning parameters were explored in order to obtain three-dimensional high-resolution images with a voxel size of 5/im (0.018^50) and a quality level required for the identification of the individual particles and the surface defining each particle-particle contact. The quantification of particle size and shape has shown that breakage of fractured grains, along existing fissures, occurs both during reconstitution and shearing of the intact soil, a phenomenon that cannot be observed using invasive techniques such as sieve analysis. Statistical analyses of the distribution of fabric directional data in terms of particle orientations, contact normals, branch vectors and void orientations were carried out at each loading stage. It has been shown that the initial particle orientation fabric that develops during the deposition of the material tends to persist during shearing, while the contact normals seem to be reorientated along the direction of the major principal stress in the post-peak regime. Different patterns were observed within the shear band as both the particles and the contact normals appeared to rotate towards the direction of the shear plane. The measurements from the tomographic data were complemented with a qualitative description of the morphology and fabric using SEM and optical microscope images of thin sections.

This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Thesis: S.M., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2019
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (pages 67-72).
This thesis describes the development of a new class of electrically-driven soft robotic actuators built from handed shearing auxetics (HSAs). Soft robots - robots made out of more compliant materials such as rubber and silicone - are significantly more robust and safer than their rigid-bodied counterparts due to their intrinsic compliance. However, existing soft robots are mostly fluid-driven, causing them to be significantly more energy inefficient, susceptible to puncture and limited in controllability. To address these issues, we use HSAs to create compliant actuators without the inherent issues of pneumatic actuation. Through analysis of planar symmetry groups, we add chirality to shearing auxetic patterns, creating materials that expand with a handed bias when pulled in tension. This new metamaterial design enables us to create new structures that have a strong coupling between twisting and extension, letting us use traditional electric-based motors to get linear motion. In this thesis, we explain the theory behind this new class of auxetics, demonstrate how HSAs can be coupled to form compliant linear actuators, and characterize the actuators' performance in a variety of applications. This work culminates in an electrically driven soft robotic gripper which is significantly smaller, more energy efficient and more puncture resistant than existing pneumatic soft robotic grippers.
"This work was done in the Distributed Robotics Laboratory at MIT with support from The Boeing Company, Amazon, JD, the Toyota Research Institute (TRI), the NASA Space Technology Research Grant NNX13AL38H, and the National Science Foundation - grant numbers EFRI-1240383, IIS-1226883, CCF-1138967, and #1830901. I was personally supported under the National Science Foundation Graduate Research Fellowship grant #1122374, the Paul & Daisy Soros Fellowship for New Americans, and the Fannie and John Hertz Foundation"
by Lillian Tiffany Chin.
S.M.
S.M. Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science

Several studies have been conducted to research the effectiveness of brush removal on hydrologic properties such as increased water yields and water quality. The Leon River Restoration Project (LRRP) is a large scale brush management program aimed at assessing the impacts of the mechanical removal of Ashe juniper (Juniperus ashei) on the quantity and quality of water, as well as wildlife habitat and livestock forage production. The objectives of this particular study are to assess the short and long term impacts of mechanical rangeland management techniques on runoff water yield and sediment loss from rainfall simulator plots. Two ecological sites were used to conduct rainfall simulation in 3 stages. Rainfall simulations were completed on Redland and Low Stony Hill sites in June 2003 prior to treatment, July 2003 after Ashe juniper was sheared from treated areas of both sites and 11 months after treatment in June 2004. Infiltration rates on both the Redland and Low Stony Hill sites increased after juniper was removed except for the treated brush plots on the Redland site, which experienced a 33% decrease. During the third simulation, infiltration rates decreased on all plots. Grass and litter biomass, as well as bare ground were influential on both sites. Percent bare ground affected infiltration rates the most on the Redland site where bare ground on the treated brush site was 23% in July 2003 and 42% in June 2004. The grass plots on the Low Stony Hill site had the greatest percentages of bare ground during the second simulation. Very few significant differences were apparent with sediment production on the Low Stony Hill site; however, the treated brush plots on the Redland site did experience a significant increase in soil loss following treatment. Sediment production increased from 24.6 kg/ha to 1,730 kg/ha in one month on the treated brush site. All other plots on the Redland site decreased in sediment discharge. Sediment production also had minor increases on the grass plots and treated brush of the Low Stony Hill. Once again, standing crop and bare ground seemed to have the greatest influence on sediment production.

Abstract Cellulose micro- and nanofibrils are elongated, flexible nano-scale particles produced from natural fibres with intensive mechanical treatments, usually in the form of dilute aqueous suspensions. Due to the recalcitrant structure of the fibres, mechanical, chemical and enzymatic pre-treatments are often used to loosen the fibre wall structure so as to facilitate the mechanical liberation of micro- and nanofibrils and reduce the high amount of mechanical energy needed. However, it is still unclear how different chemistries affect the disintegration phenomena and how mechanical action starts to unravel the fibre structure, and thus how micro- and nanofibrillation could best benefit from the pre-treatments. In addition, the high water content used in the process increases the production and transportation costs of the material, so that the solids content should be increased. Reducing the water content before or after production would be challenging, however, due to changes in fibre properties during drying (hornification) and the tendency for the resulting nanofibrils to agglomerate. Also, the effect of high solids content and temperature on the reduction of fibres to nano- and microfibrils is still not well understood. The aims of this work were to follow the changes in fibre morphology after mechanical, chemical and thermal modification and address their effects on the disintegration phenomena of the fibres to microfibrils. Mechanical compression-shearing, two selective oxidations and thermal drying in combination with TEMPO oxidation were used to modify the fibre structure before mechanical disintegration in a high-shear homogenizer or ball mill. The results showed that sufficient swelling of the fibre cell walls was a prerequisite for successful microfibrillation. Swelling can be promoted by loosening the hydrogen bonding network with compression and shearing forces or by increasing the charge density. Different charge thresholds were observed for microfibrillation depending on the chemistry used. Extremely hornified fibres were also successfully microfibrillated with the aid of TEMPO oxidation. Different fibre disintegration mechanisms were seen depending on the modification type and disintegration conditions. In addition, micro- and nanofibrils and nanocrystals were successfully produced under high solids (≥ 50%) conditions
Tiivistelmä Luonnonkuiduista saatavat selluloosamikro- ja -nanofibrillit ovat pitkiä ja joustavia nanokokoluokan partikkeleita, joita valmistetaan yleensä intensiivisillä mekaanisilla käsittelyillä vesiliuoksissa. Kuitujen lujan rakenteen vuoksi valmistuksessa käytetään usein mekaanisia, kemiallisia ja entsymaattisia esikäsittelyjä heikentämään kuituseinämän tiivistä rakennetta, mikä helpottaa mikro- ja nanofibrillien irtoamista kuituseinämästä, sekä alentaa valmistuksen mekaanisen energian tarvetta. On kuitenkin edelleen epäselvää, miten erilaiset kemialliset käsittelyt vaikuttavat kuitujen hajoamiseen, miten kuiturakenne alkaa purkautua mekaanisessa käsittelyssä ja miten esikäsittelyillä voitaisiin parhaiten edistää mikro- ja nanofibrilloitumista. Valmistuksessa käytettävä korkea vesipitoisuus lisää mikro- ja nanofibrillien valmistus- ja kuljetuskustannuksia. Vesipitoisuuden alentaminen valmistuksessa tai sen jälkeen on kuitenkin haastavaa, sillä kuituominaisuudet muuttuvat kuivatuksessa ja valmiit nanofibrillit kimppuuntuvat helposti. Korkean kuiva-ainepitoisuuden ja lämpötilan vaikutusta kuidun hajoamiseen mikro- ja nanofibrilleiksi ei myöskään ymmärretä vielä täysin. Työn tarkoituksena oli tutkia sellukuitujen rakenteen muutoksia mekaanisen, kemiallisen ja lämpömuokkauksen seurauksena, sekä tutkia niiden vaikutusta kuidun purkautumiseen mikrofibrilleiksi. Kuiturakennetta muokattiin puristus-hiertomenetelmällä, kahdella selektiivisellä hapetusmenetelmällä, sekä lämpökuivauksen ja nk. TEMPO-hapetuksen yhdistelmällä ennen kuitujen mekaanista hajottamista joko leikkaavassa homogenisaattorissa tai kuulamyllyssä. Tulosten perusteella riittävä kuituseinämän turvottaminen oli edellytys onnistuneelle mikrofibrilloinnille. Turpoamista saatiin edistettyä hajottamalla kuiduissa olevia vetysidosverkostoja puristus- ja leikkausvoimilla tai kasvattamalla anionisen varauksen määrää kuiduissa. Varauksen kynnysarvo mikrofibrilloitumiselle riippui käytetystä hapetusmenetelmästä. Myös kuivatuksessa erittäin sarveistuneet kuidut saatiin mikrofibrilloitua TEMPO-hapetuksen avulla. Tulosten perusteella kuiduilla on erilaisia hajoamismekanismeja, jotka riippuvat käytetystä muokkauksesta, sen intensiivisyydestä, sekä hajottamisolosuhteista. Työssä onnistuttiin myös valmistamaan mikro- ja nanofibrillejä, sekä nanokiteitä tavanomaista huomattavasti korkeammassa (≥50 %) kuiva-ainepitoisuudessa