Dissertations / Theses: 'Frictional forces'

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Gan, Aik Ben. "The effect of frictional and thermal forces upon sea bed pipeline buckling behaviour." Thesis, Sheffield Hallam University, 1985. http://shura.shu.ac.uk/19217/.

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The objective of the research programme has been to develop design parameters applicable to in-service submarine pipeline buckling behaviour. The programme has involved experimental and theoretical studies and computer graphics are widely employed throughout. Initially, as detailed in Chapter 1, the necessary buckling mechanisms in. pipelines subjected to axial compression have been identified and analysed in the form of relatively basic fully mobilised studies. In addition, errors and limitations contained within these studies have been determined and delineated. Consequently, geotechnical experimentation as reported in Chapter 2 was deemed necessary particularly given the dearth of information available relating to the nature of the friction resistance force between the pipeline and its supporting medium. Full scale values for the axial and lateral friction coefficients together with their respective fully mobilised displacements have been deduced upon the basis of model tests. A semi-empirical formula has thereby been produced for use in design practice. Further, a novel interpretation of sea bed recovery, or the pipeline's submerged self-weight inertial characteristics associated with vertical buckling, has also been determined. Following on from the above geotechnical study,more refined quasi-idealised analyses,dealt with in Chapter 3, have been undertaken incorporating the appropriate full scale deformation-dependent axial and lateral friction-response loci together with the respective sea bed recovery characteristics. These analyses enable, for the first time, definition of the appropriate critical temperature rise at which axial-flexural bifurcation occurs. Finally, noting that previous buckling analyses have been based on quasi-idealised buckling phenomena, attempts have also been made to incorporate practical submarine pipeline imperfections. Pipelines are not perfectly straight in field conditions and, consequently, the imperfection studies denoted in Chapter 4 have attempted to model the appropriate behaviour. Design charts have been produced accordingly and suggestions made regarding further studies.

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Wood, Peter Edwin. "An investigation of contact forces, flow, pressure, hysteresis and frictional effects in brush seals." Thesis, University of Oxford, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.393118.

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Christman, Benjamin M. "Evaluation of frictional forces between brackets of different types at various angulations and an arch wire: With and without pulsating vibration." Thesis, NSUWorks, 2015. https://nsuworks.nova.edu/hpd_cdm_stuetd/61.

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Objective: The objective of this study was to determine the effect of pulsating vibration on the sliding resistance between orthodontic brackets and stainless steel wires. Brackets were placed at two different angulations (0° and 5°) to simulate leveling of a tipped tooth during tooth movement. Pulsating vibration was delivered via the AcceleDent device. Background: Friction is defined as a force that retards or resists the relative motion of two objects in contact, and its direction is tangential to the common boundary of the two surfaces in contact. This has been of interest to the orthodontist since the mid-20th century. Since the time of Stoner’s paper in 1960, the orthodontic literature has been full of studies done on friction in orthodontics including: friction with different ligation methods, friction among different arch wire materials, friction and different bracket materials, and friction with various slot designs. Understanding friction has led to the emergence of new technologies in orthodontics. One of the most popular is the self-ligating bracket. This popularity arose from claims that they reduce friction during treatment. Other innovations have been introduced in the field of orthodontics to help accelerate tooth movement. Among these innovations is the application of a pulsating vibration during active orthodontic treatment. Such pulsating vibration can be delivered during orthodontic treatment by AcceleDent, which is a hands- free device designed by OrthoAccel Technologies, Inc., Bellaire, TX. The company claims the output force helps accelerate bone turnover. The following study investigated whether it could decrease treatment time via a different mechanism: decreasing frictional resistance to tooth movement along the arch wire. Methods: A paper template was made of a typodont tooth with a bracket window cut out. The bracket cut out was made with the bracket window angulated 0° and 5°. 0.022” x 0.028” standard prescription edgewise brackets (American Orthodontics, Sheboygan, WI) of ceramic, twin and self-ligating design were bonded to 3 maxillary 1st premolar typodont teeth using the template. The teeth were leveled with a 0.019” x 0.025” SS arch wire and placed in a metal scaffold. They were held in place with Aquasil Ultra XLV wash material PVS (DENTSPLY Caulk, Milford, DE.). Only the middle bracket was adjusted for angulation and accuracy was checked with the iPhone 6 level. The AcceleDent Aura device (OrthoAccel Technologies, Inc., Bellaire, TX). was attached to the occlusal surface of the teeth via cable ties. The AcceleDent Aura device provided 30 Hz of pulsating vibration. All tests were performed with a 0.019” x 0.025” SS arch wire pulled through the brackets via a Universal Testing Machine (Instron, Grove City, PA) at a crosshead speed of 2.5mm/min for 30 seconds. Frictional resistance was measured by averaging 6 recordings every 5 seconds. Results: The pulsating vibration provided by the AcceleDent device significantly reduced the resistance to sliding for each bracket type at both 0° and 5° (p<0.05). Ceramic brackets had the highest resistance to sliding of all bracket types. Conclusions: Pulsating vibration via the AcceleDent Aura device reduces the resistance to sliding between a bracket and arch wire in vitro. This may potentially decrease overall treatment time but more in vivo studies need to be done to evaluate this.

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Nguyen, le Anh Vu. "Interparticle friction and Rheology of Dense suspensions." Electronic Thesis or Diss., Université Paris sciences et lettres, 2021. http://www.theses.fr/2021UPSLS085.

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Les suspensions—un type de matériau qui comporte des particules solides dispersées dans un milieu liquide—sont omniprésentes dans notre vie quotidienne et dans l’industrie. Leur caractéristique-clé est la contrainte requise pour les mettre en écoulement à une vitesse désirée : cet attribut est le centre d’intérêt de la rhéologie. Récemment, il émerge que le frottement entre les particules se répercute sur la rhéologie des suspensions concentrées. Cette interaction microscopique peut être altérée en modifiant la surface des particules ou, notamment, en changeant le milieu liquide. Dans cette thèse, nous cherchons à démontrer et caractériser l’effet du frottement inter-particulaire sur des comportements rhéologiques des suspensions dans le régime dense. Nous trouvons que des suspensions de mêmes particules se comportent de façons différentes (newtonienne ou rhéofluidifiante) en dépendant des solvants utilisés. En outre, leur courbe d’écoulement peut être connectée à la mesure de coefficient de frottement en fonction de la force normale appliqué sur les particules. Notre travail expérimental aide ouvrir la voie aux études sur des effets de forces à l’échelle microscopique sur la rhéologie en bulk
Suspensions - a type of material consisted of solid particles dispersed in a liquid medium— are omnipresent in our daily life and in industry. Their key characteristic is the shear stress required to make them flow at a desire shear rate: this attribute is the area of interest of Rheology. Recently, it emerged that the friction between the particles impact the rheology of concentrated suspensions. This microscopic interaction can be altered by modifying the particle surface or, especially, by changing the liquid medium. In this thesis, we are looking to evidence and characterize the effect of interparticle friction on the rheological behaviors of suspension in the dense regime. We found that suspensions of same particles behave differently (Newtonian or shear-thinning) depending on the solvents utilized. Furthermore, their flow curve can be connected to the measurement of friction coefficient as a function of the normal force applied on the particles. Our work help paving the way for studies on effects of forces at microscopic scale on the bulk rheology

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White, Joshua Childs. "Development and validity assessment of the Max Power Model for the detection, separation, and quantification of differences in resistive and propulsive forces in swimming." [Bloomington, Ind.] : Indiana University, 2006. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3219898.

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Thesis (Ph.D.)--Indiana University, School of Health, Physical Education and Recreation, 2006.
"Title from dissertation home page (viewed June 28, 2007)." Source: Dissertation Abstracts International, Volume: 67-06, Section: B, page: 3092. Adviser: Joel M. Stager.

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Quignon, Benoit. "Investigations of the frictional behaviour of nanotextured surfaces by friction force microscopy." Thesis, University of Bristol, 2015. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.685551.

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Friction is omnipresent in our daily life, and although this phenomenon has been studied for centuries, the fundamental understanding on tribological processes as a whole is still lacking. Reducing friction is beneficial in many applications, from mediating wear to improving the life span of devices, hence improving our knowledge of the parameters affecting frictional forces is of paramount importance. In particular, the miniaturisation of modern devices implies that their reliability and durability become friction limited. Recent advances in the fabrication of nanostructured surfaces with tuneable topographic properties, along with advances in metrological tools such as the atomic force microscope (AFM), now provide the means to systematically study friction on well-defined nanostructured surfaces. This research project is focused on the lubricated and un lubricated frictional behaviour of nanotextured surfaces using the AFM with conventional and colloidal probes. The frictional properties of nanotextured surfaces bearing aluminium oxide nanodomes and zinc oxide nanorods of varying topographic properties in air, as well as the frictional properties in aqueous solutions of ionic and nonionic surfactants on flat and textured surfaces of titanium oxide, are reported. The results show that for the nanodomed-textured surfaces, the ancient Amontons laws of dry friction are obeyed; however, the friction coefficient was insufficient to fully characterise the frictional behaviour of such nanotextured surfaces. Pronounced stick-slip frictional characteristics were observed, with the amplitude of the stick-slip varying linearly with the applied load. On nanorod-textured surfaces, the friction-applied load linear relationship was however lost, due to the bending contributions of the rods to the lateral force experienced by the probe. Finally, the results obtained on flat and pillar-textured titanium oxide surfaces showed that ionic surfactants could mediate effective boundary lubrication with the existence of two frictional regimes, due to load- and shear-induced structural changes in the nanofilms of the adsorbed surfactant molecules.

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Raftari, Maryam. "Investigation of the frictional behaviour of end-grafted polymer layers using friction force microscopy." Thesis, University of Sheffield, 2014. http://etheses.whiterose.ac.uk/7001/.

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Cigeroglu, Ender. "Development of microslip friction models and forced response prediction methods for frictionally constrained turbine blades." Columbus, Ohio : Ohio State University, 2007. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1181856489.

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Garoff, Niklas. "The Friction between Paper Surfaces." Doctoral thesis, Stockholm, 2002. http://www.diva-portal.org/kth/theses/abstract.xsql?dbid=3415.

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Wallin, Harald. "An investigation of friction graphs ranking ability regarding the galling phenomenon in dry SOFS contact : (Adhesive material transfere and friction)." Thesis, Karlstad University, Faculty of Technology and Science, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-2790.

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The main purpose of this project is to investigate different tool steels in terms of their ability to withstand material transfer buildup, so-called galling, occurring in SMF (sheet metal forming) operations. The ability to withstand galling is vital to optimize cost-effectiveness and increase the work tool’s effective operational time. This investigation studies four different tool steels, including a TiN-coating, with the intention of evaluating the microstructures, chemical composition and hardness effect on galling resistance in dry conditions using a slider-on-flatsurface (SOFS) tribo-tester which measures the coefficient of friction during sliding.

An OP (optical profilometer) was used to measure the size and geometry of lump growth on the tool and damage on the work sheet. A scanning electron microscope (SEM) was used to identify the interacting tribological mechanisms exhibited at different stages during the slide. The SEM figures confirmed three different types of characteristic patterns exhibited in the tracks after tribo- testing which were categorized as mild adhesive, abrasive and severe adhesive damage.

A SEM figure that illustrates a ragged contact surface and an obvious change in the sheet materials plastic behavior is in this report regarded as a sign of severe adhesive contact, the characteristics could possibly be explained by local high temperature and high pressure followed by a sudden pressure drop and creation of hardened welds or solders between the two surfaces which increase the frictional input needed for further advancement. Friction coefficients observed in the initial 100% mild adhesive stage were, μ=0,22-0,26 succeeded by abrasive SEM characteristics often in association with mild adhesive contact and friction values between μ=0,25-0,4 which where sometimes followed by severe adhesive SEM characteristics in 100% of the contact zone with friction values between μ=0,34- 0,9 respectively. The tool material that performed best according to the friction detection criteria was Sv21 closely followed by Sleipner (TiN coated) and Va40 (HRC 63.3). Unfortunately was the friction criteria, a significant raise in friction for defining a sliding length to galling, not adequate for dry conditions due to immediate material transfer succeeded by cyclic changes between partial or 100% abrasive+mild adhesive and severe adhesive contact. The mechanism that change abrasive wear in association with mild adhesive contact, (moderate friction input), to sever adhesive wear, (higher friction input), is dependent on lump shape (lump geometry) and can appear at comparably low speeds 0,04-0,08 [m/s] and low friction energy input (μ=0,34), the magnitude of the change in friction is therefore not always significant and hardly detectable on the friction graph. This was quite unexpected but could be explained by concentration of friction energy rater than the absolute amount. The problem with using friction graphs for galling evaluation was increased even further when a very small lump size and low corresponding rate of material transfer to the tool surface caused a sustainable high raise in friction (μ≈0,3→0,6) on a TiN-coated tool steel called Sleipner.

A hardly detectable or similar friction raise for Sv21 and Va40 showed much larger corresponding lump size and rate of material transfer. This means that friction graphs demonstrate a clear problem with quantifying lump size [m3] and rate of material transfer [m3/s]. Another phenomenon called stick slip behavior, material transfer and lump growth followed by a sudden decrease in lump size and transfer of material back to the work sheet, is also not possible to detect on a friction graph. Because a drop in friction can easily be a change in contact temperature and lump attack angle due to a growing lump and not a decreasing lump.

The conclusion, a friction graph is not suited for galling evaluation and ranking in dry SOFS conditions. A ranking should primarily be based on dimensional OP measurements of the cross section of formed tracks and scratches or preferably by repeated OP measurements of the tool surface during a single test, the last revel the exact lump growth history and true lump growth even in the sliding direction.

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Ляшенко, Яків Олександрович, Яков Александрович Ляшенко, and Yakiv Oleksandrovych Liashenko. "Friction force for boundary lubrication." Thesis, Видавництво СумДУ, 2011. http://essuir.sumdu.edu.ua/handle/123456789/20362.

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Sinclair, E. C. "Geometric reaction forces in billiards." Thesis, University of Bristol, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.294868.

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Ahmed, Mohammed Zakaria. "Plastic buckling of plates including edge contact-frictional force effects." Diss., The University of Arizona, 1991. http://hdl.handle.net/10150/185662.

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In this study, the effects of edge contact-frictional force imposed by the machine heads on the distribution of stress state prior to buckling of plates are investigated. A contact-friction interface element is included in the pre-buckling analysis which considers the possibility of slip between the machine heads and the plate. All analyses are performed using the incremental theory of plasticity in which the formulations given by Ramberg-Osgood and Richard are implemented to calculate the tangent modulus. The pre-buckling stress states are used to determine the buckling stresses. In the buckling formulation of the plate, an element stiffness based on Hermitian interpolation function is included. The buckling stresses are compared with those of the test results and the closed form solutions available in the literature. The effect of edge boundary imperfections are also considered in this study.

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Colburn, Tracie Jane. "Friction force microscopy : quantifying nanoscale chemistry." Thesis, University of Sheffield, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.443886.

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Lovrich, Neil Robert. "Fretting Fatigue of Ti-6Al-4V: Experimental Characterization and Simple Design Parameter." Thesis, Available online, Georgia Institute of Technology, 2004:, 2004. http://etd.gatech.edu/theses/available/etd-07072004-113607/unrestricted/lovrich%5Fneil%5Fr%5F200408%5Fmast.pdf.

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Thesis (M.S.)--Mechanical Engineering, Georgia Institute of Technology, 2005. Directed by Richard Neu.
Johnson, Steven, Committee Member ; McDowell, David, Committee Member ; Neu, Richard, Committee Chair. Includes bibliographical references.

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Kweon, Hyo Jin Jin. "Adhesion and friction forces of colloidal particles in atmospheric systems." Diss., Georgia Institute of Technology, 2013. http://hdl.handle.net/1853/51933.

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Interactions of colloidal particles with surfaces occur in natural and engineered systems, and they influence the transport of contaminants through diffusion, aggregation, filtration, and sedimentation. To quantify the transport and fate of colloidal particles and their influence on environmental systems, it is important to understand their interactions with surfaces. These interactions are influenced by physical and chemical surface properties such as hydrophobicity, charge density, and roughness, as well as environmental conditions such as relative humidity (RH). In atmospheric systems, RH induces the capillary force and also influences the contributions of van der Waals and electrostatic forces. To investigate the role of surface properties and RH in the interaction of colloidal particles with surfaces, atomic force microscopy was employed to measure the adhesion and friction forces of colloidal particles including Bacillus thuringiensis spores, silica, and gold at various experimental conditions with several types of surfaces including mica, silica, and radioactive gold. Contributions to the adhesion force by van der Waals, capillary, and electrostatic forces were theoretically calculated and compared to measured forces. Through experimental results and theoretical studies, it was identified how surface properties of interacting surfaces and experimental conditions influence the interfacial interactions of colloidal particles in atmospheric systems. The role of RH in adhesion and friction depends on the hydrophobicity or contact angles of interacting surfaces and surface roughness. Relative humidity also influences the contribution of electrostatic force to the total adhesion force by screening the strength of surface potential or providing a passage for charge leakage. The results of this thesis provide a better understanding of particulate processes that are influenced by the interactions of colloidal particles with surfaces and can be useful in monitoring and control of contamination in atmospheric systems.

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ITHARAJU, RAJESWARI R. "FRICTION STIR PROCESSING OF ALUMINUM ALLOYS." UKnowledge, 2004. http://uknowledge.uky.edu/gradschool_theses/322.

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Friction stir processing (FSP) is one of the new and promising thermomechanical processing techniques that alters the microstructural and mechanical properties of the material in single pass to achieve maximum performance with low production cost in less time using a simple and inexpensive tool. Preliminary studies of different FS processed alloys report the processed zone to contain fine grained, homogeneous and equiaxed microstructure. Several studies have been conducted to optimize the process and relate various process parameters like rotational and translational speeds to resulting microstructure. But there is only a little data reported on the effect of the process parameters on the forces generated during processing, and the resulting microstructure of aluminum alloys especially AA5052 which is a potential superplastic alloy. In the present work, sheets of aluminum alloys were friction stir processed under various combinations of rotational and translational speeds. The processing forces were measured during the process and the resulting microstructure was analyzed using TEM. The results indicate that the processing forces and the microstructure evolved during FSP are sensitive to the rotational and translational speed. It is observed that the forces generated increase with the increasing rotational speed. The grain refinement was observed to vary directly with rotational speed and inversely with the translational speed. Also these forces generated were proportional to the grain refinement i.e., greater refinement of grains occurred at lower forces. Thus the choice of process parameters especially the rotational speed has a significant effect on the control and optimization of the process.

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PHADKE, RAHUL A. "A MICROSLIP SUPERELEMENT FOR FRICTIONALLY-DAMPED FORCED RESPONSE PREDICTIONS." University of Cincinnati / OhioLINK, 2004. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1085760663.

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Hurtado, José Francisco. "Experimental study of workpiece-fixture contact forces and friction during machining." Thesis, Georgia Institute of Technology, 1998. http://hdl.handle.net/1853/16096.

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Hahlin, Mattias. "Evaluation of variations of the frictional force between a bullet and a case in a loaded cartridge." Thesis, Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-68653.

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To ensure that manufactured cartridges is safe to use, a tensile test is performed. The frictional force between the bullet and the case is required according to Normas standard to be between 15 – 75 Kg. Variations of the frictional force, with values outside of the standard had been noted by Norma Precision without understanding the cause. The aim of this report was to investigate and evaluate possible causes of the variations measured by tensile tests, difference between extreme values and to find a solution to what can be done to prevent the variations. Two different cases and three different bullets were used by request from Norma in the scope of this report. Different combinations of the bullets and cases was tested by alternating process parameter, surfaces and loading procedures. The loaded cartridges went through tensile tests to investigate differences. Bullets and cases with extreme values from the measured frictional force were chosen for further investigation in SEM and profilometer. To be able to draw further conclusions four different simulation models was created in Abaqus and different parameters was calculated. The dimensions and shape of the bullet resulted as the cause of changes of the tensile test curves. The smallest frictional force was found to differ from the largest by a change in wear mechanism from mainly abrasive ploughing to cutting and adhesion that caused transfer of material from the bullet to the case. The change in wear mechanism was found to be caused by an increased bullet diameter. The loading procedure was found to cause variations in plastic deformation on the neck of the case and damage the bottom of the bullet. The loading procedure was assumed to have the largest impact on the variations in frictional force. To minimize the variations the central axis of the case was suggested to be in line with the central axis of the bullet.

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Anderson, Evan V. "Atomic Force Microscopy: Lateral-Force Calibration and Force-Curve Analysis." Digital WPI, 2012. https://digitalcommons.wpi.edu/etd-theses/337.

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This thesis reflects two advances in atomic force microscopy. The first half is a new lateral force calibration procedure, which, in contrast to existing procedures, is independent of sample and cantilever shape, simple, direct, and quick. The second half is a high-throughput method for processing, fitting, and analyzing force curves taken on Pseudomonas aeruginosa bacteria in an effort to inspire better care for statistics and increase measurement precision.

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Laine, Antoine. "Sliding Friction at the nanoscale." Thesis, Université de Paris (2019-....), 2020. http://www.theses.fr/2020UNIP7076.

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Dans ce manuscrit, nous utilisons des méthodes dérivées de la microscopie à force atomique afin de mesurer, à l'échelle nanométrique, la réponse mécanique de différents systèmes. L'accent est porté sur la mise en lumière de la réponse frictionnelle et des mécanismes de dissipation à l'échelle du contact unique, où matières molle et condensée se confondent.Nous présentons premièrement le développement d'un nouvel outil expérimental permettant des mesures de nano-rhéologie et de nano-tribologie en environnement contrôlé. L'étude des propriétés mécaniques de liquides ioniques nano-confinés, avec cet instrument, nous révèle le caractère vitreux de ces électrolytes denses aux interfaces métalliques.Nous étudions par la suite les phénomènes de dissipation à l'échelle ultime, pour des jonctions métalliques de quelques atomes de diamètre. De l'absence de défauts découle une réponse plastique aux antipodes de notre expérience macroscopique.In fine, nous mettons l'accent sur l'étude de la dynamique d'une interface métallique de quelques atomes et développons de nouvelles stratégies expérimentales afin de résoudre la réponse frictionnelle du système soumis à une contrainte harmonique. Nos mesures, quantitativement reproduites numériquement, révèlent un mécanisme de friction quantifiée à l'échelle atomique
In this manuscript, we use methodes inherited from Atomic Force Microscopy in order to measure the nanoscale mechanical response of different systems. The focus is put on highlighting the frictional response and dissipation mechanisms taking place at the single asperity level, where soft and hard condensed matter meet.We first present the development of a new experimental tool allowing nanorheology and nanotribology measurement in controlled environment. The study of mechanical properties of nanoconfined RTILs with this apparatus revealed the glassy nature of these dense electrolytes at metallic interfaces.We then study the dissipation phenomena at the ultimate scale for metallic nanojunctions made of a few atoms. The absence of defects rationalizes their unexpected mechanical properties in striking difference with the macroscopic realm.In fine, we focus on the dynamics of a metallic interface made of a few atoms and develop new experimental strategies to probe the frictional response of the interface under harmonic applied stress. Our measurements are quantitatively reproduced numerically and reveal an atomic-scale quantized slip friction mechanism

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Gregoris, Daniele. "Cosmological models, nonideal fluids and viscous forces in general relativity." Doctoral thesis, Stockholms universitet, Fysikum, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-107130.

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This thesis addresses the open questions of providing a cosmological model describing an accelerated expanding Universe without violating the energy conditions or a model that contributes to the physical interpretation of the dark energy. The former case is analyzed considering a closed model based on a regular lattice of black holes using the Einstein equation in vacuum. In the latter case I will connect the dark energy to the Shan-Chen equation of state. A comparison between these two proposals is then discussed. As a complementary topic I will discuss the motion of test particles in a general relativistic spacetime undergoing friction effects. This is modeled following the formalism of Poynting-Robertson whose link with the Stokes’ formula is presented. The cases of geodesic and non-geodesic motion are compared and contrasted for Schwarzschild, Tolman, Pant-Sah and Friedman metrics respectively.

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Chen, Jin-Jae. "Prediction of periodic forced response of frictionally constrained turbine blades /." The Ohio State University, 1999. http://rave.ohiolink.edu/etdc/view?acc_num=osu1488187763847997.

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Essa, Irfan A. (Irfan Aziz). "Contact detection, collision forces and friction for physically based virtual world modeling." Thesis, Massachusetts Institute of Technology, 1990. http://hdl.handle.net/1721.1/14054.

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Kinsella, Mary E. "Ejection forces and static friction coefficients for rapid tooled injection mold inserts." Connect to this title online, 2004. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1092660338.

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Thesis (Ph. D.)--Ohio State University, 2004.
Title from first page of PDF file. Document formatted into pages; contains xvi, 206 p.; also includes graphics (some col.). Includes bibliographical references (p. 167-173). Available online via OhioLINK's ETD Center

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Хоменко, Алексей Витальевич, Яків Олександрович Ляшенко, Яков Александрович Ляшенко, Yakiv Oleksandrovych Liashenko, Т. С. Медина, Oleksii Vitaliiovych Khomenko, Олексій Віталійович Хоменко, and Oleksii Vitaliiovych Khomenko. "Феноменологическая модель граничного трения." Thesis, Видавництво СумДУ, 2010. http://essuir.sumdu.edu.ua/handle/123456789/3982.

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В рамках теории фазовых переходов Ландау построена термодинамическая модель плавления ультратонкой пленки смазки, зажатой между двумя атомарно-гладкими твердыми поверхностями. Введена неравновесная энтропия, описывающая часть теплового движения, обусловленного неравновесным и неравномерным характером теплового распределения. Равновесная энтропия изменяется во времени за счет перехода неравновесной энтропии в равновесную подсистему. При цитировании документа, используйте ссылку http://essuir.sumdu.edu.ua/handle/123456789/3982

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Hurley, Claire R. "Friction Force Microscopy: A Quantitative Analysis of Polymer Surfaces." Thesis, University of Sheffield, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.485878.

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Friction force microscopy (FFM) measurements have been carried out on films of poly(ethylene terepthalate) (pET) in a variety of media. In ethanol, the adhesion force is small and the frictionload relationship is linear. In perfluorodecalin, non-linear load dependence is observed and the data have been found to fit the Johnson-Kendall-Roberts model of contact mechanics. The behaviour in hexadecane is also characterised by a single asperity contact model, the DerjaguinMiiller- Toporov model. It is suggested that these differences are due to the different dielectric constants ofthe media and their influence on the strength oftip-sample adhesion. PET films have been exposed to ultra-violet (UV) light and characterised using X-ray photoelectron spectroscopy (XPS), contact angle measurement and FFM. XPS data indicated an increase in the overall oxygen content at the surface; attributed to the introduction of atmospheric oxygen. The surface coefficient of friction was found to increase over the exposure approaching a limiting value after 100 min. This increase in the microscopic properties ofthe surface reflected a change in the macroscopic properties observed by contact angle goniometry. Plasma-polymerised tetraglyme films (pP4G) have been modified by exposure to UV light and characterised using XPS and FFM. XPS data have shown that the ether component of the CIs spectrum declines after UV exposure, while carbonyl and carboxylate contributions increase. The coefficient of friction increased, reaching a limiting value after 10 min, in agreement with ether and carboxylate components in the CIs spectra. Samples exposed to UV light through a mask yielded excellent frictional contrast. When immersed in solutions of proteins labelled with fluorescent markers, patterns were formed yielding excellent fluorescence contrast when characterised by confocal microscopy. The exposed areas became adhesive towards proteins, while the masked areas remained resistant. Sub-micron structures as small as 338 nm were formed via scanning near-field photo-lithography; resulting features were used to immobilise proteins, suggesting an effective route to the formation of sub-micron protein patterns.

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Bernstein, Nicholas L. "Force sensor modeling and friction compensation for haptic interfaces." Connect to online resource, 2007. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3273727.

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Fernandes, Thales Fernando Damasceno. "Friction-induced artifact in atomic force microscopy topographic images." Universidade Federal de Minas Gerais, 2014. http://hdl.handle.net/1843/BUOS-9PQHRG.

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In Contact Mode Atomic Force Microscopy (CM-AFM), a cantilever with a sharp tip on its end is employed to acquire topographic information. Such acquisition is normally made by monitoring the deflection of the cantilever when it is in contact with the surface being scanned and using deflection variations as a feedback signal to the control electronics in order to keep the deflection constant (also known as constant force imaging mode in the literature). However, there is a major problem with this approach since, in most cases, a constant force scanning is not possible: frictional forces, besides normal forces, may bend the cantilever. Such additional bending (deflection) needs to be considered in the formulation of the problem. The present dissertation investigates how these forces (frictional and normal) can give rise to a topographic artifact when scanning along the cantilever axis direction. Such artifact is even more dramatic when the friction coefficient of the sample changes from region to region. This effect is studied experimentally, with a sample composed of graphene monolayer atop silicon oxide. The observed artifact, caused by frictional forces, causes the graphene to appear either thicker or thinner than it really is depending on scan direction. A theoretical examination is also made both with analytical methods (Euler-Bernoulli beam theory) and a simulation on COMSOL Multiphysics package. The theory not only predicts the artifact, but also indicates how it can be completely avoided by changing the scanning angle to the perpendicular direction of the cantilever axis.
No Modo Contato da Microscopia de Força Atômica (CM-AFM), uma alavanca com uma ponta bastante afiada em sua extremidade é usada para adquirir informação topográfica. Tal aquisição normalmente é feita monitorando a deflexão da alavanca quando em contato com a superfície a ser varrida. Usa-se a variação da deflexão como um sinal de feedback que controla a eletrônica, mantendo a deflexão constante (conhecido como modo de força constante na literatura). Porém, existe um grande problema com essa abordagem, já que, na maioria dos casos, fazer uma varredura com força constante não é possível: forças de atrito, além da força normal, podem fletir a alavanca. Tal curvatura adicional (deflexão) deve ser considerada na formulação do problema. Essa dissertação investiga como essas forças (normal e de atrito) podem dar origem a um artefato de topografia quando é feito uma varredura ao longo do eixo da alavanca. Tal artefato é ainda mais dramático quando o coeficiente de atrito da amostra muda de região para região. Esse efeito é estudado experimentalmente, com uma amostra composta de uma monocamada de grafeno em cima de oxido de silício. O artefato observado, causado pelas forças de atrito, faz o grafeno aparecer mais espesso ou mais estreito do que realmente é, dependendo da direção de varredura. Uma verificação teórica também é feita usando métodos analíticos (teoria de vigas de Euler-Bernoulli) e simulações usando o pacote COMSOL Multiplysics. A teoria não apenas prediz o artefato, mas também indica como ele pode ser completamente evitado ao trocar o ângulo de varredura para perpendicular à direção do eixo da alavanca.

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Hemmer, Jason D. "Characterization of vascular smooth muscle cell mechanical and frictional properties using atomic force microscopy." Connect to this title online, 2008. http://etd.lib.clemson.edu/documents/1239894622/.

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Najafi, Seyed Kamran. "Design of Contact Line Friction Measurement Machine Apparatus." Scholar Commons, 2012. http://scholarcommons.usf.edu/etd/4377.

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The purpose of this project is to design and manufacture a high precision machine to directly measure the surface force of fluids. Knowing how to move droplets easier with less resistance can increase the potential of a wide range of applications and improve the performance of things such as self-assembly applications. This machine has the ability to measure forces of up to 100 N with a MEMS based sensor. The motion system on this machine moves a substrate underneath of a droplet for 100 mm and applies dragging force to the sensor. It moves with a controlled speed with high accuracy and repeatability. The machine also consists of three manual, three axis controls for positioning key components for observation, control of the air vacuum lifter, and adjustment of the sensor position. There is also an enclosure box that provides visibility to operate and protects the inside environment from dirt during process and also by applying positive air flow during setting up with open windows. The test components were designed to provide maximum flexibility to adjust the setup. A camera in the machine contributes to collect data during the test progress and has the ability to capture pictures and record videos.

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Reardon-Smith, Mardi Jane. "Forces and Frictions of Belonging: Land, People and Changing Environments in Cape York, Australia." Thesis, The University of Sydney, 2021. https://hdl.handle.net/2123/25462.

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This thesis is an anthropological study of people involved in land management in Cape York Peninsula, Australia. It investigates how this diversity of people come to belong in meaningful ways, examining the multi-layered and intercultural situations in which people form, maintain and transform relationships in changing environments. Contemporary Cape York is a site of complex land-tenure arrangements, political struggles and environmental change. Based on 14 months of field research with settler-descended graziers, Aboriginal traditional owners and Queensland Parks and Wildlife Service rangers the thesis investigates how these diverse groups of people articulate, value and experience their social, cultural and practical connections to land. By attending to non-Indigenous people and Aboriginal traditional owners, the analysis grapples with the friction of intercultural engagement in the region. A key argument is that social and cultural differences between groups of people are not fixed or stable. Instead, through various kinds of interactions, social differentiation and cultural norms and practices are re-worked, making an indeterminate space of intercultural encounter that can result in both new forms of difference and inequality, and, importantly, partially shared environmental knowledges, practices and ways of relating to land. Developing the analytical concepts of intercultural mediation and friction, this thesis thus examines how forms of belonging and difference are enacted, experienced and transformed relationally. It contends that relationships to land and forms of belonging are mediated by property rights, manual labour, conservation initiatives, bureaucratic interventions, cattle, fire, seasonality, climate change and invasive species. In the interactions and contingent collaborations among people as well as between people and more-than-human forces, meaningful relationships to land are continually co-produced and reworked. This ethnographic study contributes to a growing body of scholarly work in anthropology and related disciplines that attend to the details of intercultural and multispecies relationships, and to questions of human and non-human belonging in settler-colonial states.

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Mertens, Felix [Verfasser]. "Fractional resonance excitation in dynamic friction force microscopy / Felix Mertens." Gießen : Universitätsbibliothek, 2015. http://d-nb.info/1073821609/34.

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Crespo, Alexia. "Compréhension de la tribologie des films limites : de l'organisation moléculaire à la réponse en friction." Thesis, Lyon, 2017. http://www.theses.fr/2017LYSEC021/document.

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Le contrôle de la friction en régime limite s’effectue par le biais de lubrifiants qui, par l’adsorption de molécules sur les surfaces, réduisent les contacts directs entre aspérités. Dans ce contexte, l’objectif de cette thèse est de comprendre et de coupler les mécanismes, à la fois, d’adsorption et d’auto-organisation de différents acides gras sur des surfaces, et les mécanismes de friction interfaciale sous des conditions stationnaires et transitoires. L’effet de l’architecture moléculaire, modifiée par la présence et la conformation d’une insaturation dans la chaîne aliphatique des acides gras, a également été analysé. La caractérisation in-situ, à l’échelle moléculaire, a été réalisée avec le tribomètre moléculaire ATLAS développé au LTDS. Cet appareil permet des déplacements quasi-statiques et dynamiques, d’une sphère mise en regard d’un plan, suivant trois axes. Trois solutions d’acides gras, en faible concentration dans du dodécane, ont été analysées. Les déplacements et les forces, normaux et tangentiels, sont mesurés à l’aide de capteurs capacitifs d’une résolution respective de 0.015 nm et 10 nN. Des sollicitations dynamiques superposées permettent de caractériser simultanément la rhéologie de l’interface confinée en termes d’amortissement et de raideur, dans les deux directions. Les résultats montrent que les acides gras s’adsorbent par interaction physique sur les surfaces pour former des films visco-élastiques d’une épaisseur d’environ 15 Å sur chaque surface. Le taux de couverture et la cinétique d’adsorption de ces couches dépendent de l’architecture moléculaire des acides gras. Cette dernière gouverne également la friction interfaciale, qui a été qualifiée de supraglissement, et la rhéologie des monocouches auto-assemblées. Les différentes organisations de films conduisent ainsi à différentes évolutions de la friction en fonction de la vitesse de glissement et de la pression de contact. La réponse en friction transitoire et l’accommodation lors du glissement vers un nouvel état stationnaire ont de plus été décrites par des distances caractéristiques, de plusieurs nanomètres, reflétant le renouvellement statistique des spots de contact, et par des temps de relaxation, de l’ordre de la seconde, décrivant le réarrangement moléculaire au sein de l’interface. Enfin, une modélisation théorique de la friction limite a été proposée afin de comprendre l’origine moléculaire de la friction entre monocouches d’acides gras mettant ainsi en évidence le couplage fort de deux échelles spatiales et temporelles
Friction in boundary lubrication can be controlled by the adsorption of molecules on surfaces that reduce direct contacts between asperities. In this context, the aim of this thesis is to understand and to couple the mechanisms of adsorption and self-organization of different fatty acids on surfaces, with the mechanisms of interfacial friction under steady-state regime and transient conditions. The effect of the molecular architecture, modified by the presence and conformation of one unsaturation in the aliphatic chain of fatty acids, was also analyzed. In-situ characterization, at the molecular level, was performed with the molecular tribometer ATLAS, developed at LTDS. This apparatus allows quasi-static and dynamic displacements, of a sphere in front of a plane in three directions. Three fatty acids solutions, in low concentration in dodecane, were analyzed. The displacements and the forces, normal and tangential, are measured using capacitive sensors with a resolution of 0.015 nm and 10 nN respectively. Dynamic superimposed measurements allow a simultaneous rheological characterization of the confined interface in terms of damping and stiffness in two directions. The results show that the fatty acids adsorb on the surfaces by weak interactions and form viscoelastic films with a thickness of about 15 Å on each surface. The coverage rate and adsorption kinetics of these layers depend on the molecular architecture of the fatty acids. This architecture also governs interfacial friction, which has been described as superlubricity, and the rheology of self-assembled monolayers. Various film organizations have thus led to different evolutions of the friction as a function of the sliding speed and the contact pressure. The transient friction response and its accommodation during slip to a new stationary state have also been described by characteristic distances of several nanometers, reflecting the statistic average renewal of the contact spots, and by relaxation times of the order of the second, describing the molecular rearrangement within the interface. Finally, theoretical modeling of boundary friction has been proposed to understand the molecular origin of the friction between monolayers of fatty acids and highlight the strong coupling between both spatial and temporal scales

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36

Nikogeorgos, Nikolaos. "Adhesion, friction & mechanics of nanoscale contacts between coated surfaces studied by atomic & friction force microscopy." Thesis, University of Sheffield, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.574567.

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Friction force microscopy was employed for the tribological investigation of human head hair in: a dry atmosphere and in de-ionized water. The effects of bleaching, conditioning, and immersion in methanolic KOH were quantified using the relative coefficient of friction (u). The coefficient of friction in both environments increased in the order: virgin < virgin-conditioned < damaged-conditioned < bleached < KOH-damaged hair. All categories of hair exhibited higher friction coefficients in the aqueous environment, attributed mainly to the higher elastic compliance of the fibres due to water absorption. Secondary ion mass spectroscopy was used as a complementary technique to examine the presence 0 f fatty acids on the cuticular surface 0 r the different categories of hair as well as the conditioner distribution. Conditioner species were detected along the whole cuticular surface. The combination of SIMS with FFM data suggests that the main reason for the different tribological properties of the categories of hair examined is the altered chemistry of the surface, i.e., partial removal of the covalently bound lubricant layer of 18-MEA and, also, of the unbound fatty acids (stearic, palmitic, myristic, etc.) by the damaging agents. Atomic and friction force microscopy was employed to investigate friction and adhesion between polar and between non-polar self-assembled mono layers in pure solvents as well as in heptane/acetone mixtures of varying polarity. The two polar interfaces examined were l l-rnercapto-l-undecanol vs l l-rnercapto-l-undecanol (MUT), and II-mercapto-l- undecanol vs Oiethoxy-Phosphatoethyl-Triethoxysilane (OPTS), while the non-polar interface examined was l-dodecanethiol vs l-dodecanethiol (000). For the MUT and OPTS interfaces the pull-off forces were found to decrease with increasing static dielectric constant of the medium (e), while for the 000 interface the opposite trend was observed. A simple model based on functional group H-bond parameters was found adequate to describe the adhesive interactions for the MUT and OPTS interfaces in terms of the degree of so lvation of the functional groups of the mono layers by the medium. In the heptane/acetone mixtures the pull-off force was observed to correlate excellently to the free energy of interaction as predicted by the model. For the 000 interface an approximation of the Lifshitz theory predicted satisfactorily the pull-off forces in media of weak hydrogen bond donor ability. The friction-load relationship at the 'wearless' regime (L < 20 nN) was found to be dependent on the strength of adhesion as well as to the molecular properties of the medium. Systems of lowest adhesion obeyed Arnonton's law, while as adhesion increased their offset displaced towards tensile loads and their slope increased, but strongly adhering systems provided a sublinear Friction - Load relation best fitted by the Derjaguin-Muller-Toporov (DMT) model of contact mechanics. Exceptionally, in n-octanol a two-sloped linear relation was observed for all interfaces, attributed to its ability to strongly physisorb on them, decreasing the friction coefficient considerably and eliminating the frictional differences of the three interfaces at loads lower than about 3 nN. These observations were rationalized by friction being considered to be the sum of an interfacial and a plowing term. The Fr-L data for all interfaces were successfully modeled, under the assumption that DMT contact mechanics is obeyed, with an adhesion-independent friction coefficient due to plowing, and an adhesion-dependent shear strength due to interfacial friction. For all interfaces the shear strength was found to increase as the pull-off force increased, thus explaining Amontori's law as the limit of zero shear strength at very weakly adhesive systems. For the MUT and OPTS interfaces in the mixtures, the shear strength was found to correlate closely to the free energy of interaction predicted by the H-bonding model used. The OPTS interface exhibited lower adhesion but higher friction than the MUT one, while the DOD interface exhibited the lowest friction. Analysis with the model used resulted in very close friction coefficients for the DOD and MUT films, but considerably higher one for the OPTS films. The shear strength of the MUT and DPTS was similar, but that of the DOD monolayer was clearly lower. These findings demonstrate the importance of packing effects and hydrogen bonding to friction.

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37

Zhao, Xin. "Empirical dynamic modeling and nonlinear force control of friction stir welding." Diss., Rolla, Mo. : University of Missouri-Rolla, 2007. http://scholarsmine.mst.edu/thesis/pdf/Zhao_09007dcc803fbd7f.pdf.

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Thesis (M.S.)--University of Missouri--Rolla, 2007.
Vita. The entire thesis text is included in file. Title from title screen of thesis/dissertation PDF file (viewed February 4, 2008) Includes bibliographical references.

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38

Liu, Xiaoyan. "Surface Force and Friction : effects of adsorbed layers and surface topography." Doctoral thesis, KTH, Yt- och korrosionsvetenskap, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-157321.

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Interfacial features of polymers are a complex, fascinating topic, and industrially very important. There is clearly a need to understand interactions between polymer layers as they can be used for controlling surface properties, colloidal stability and lubrication. The aim of my Ph.D study was to investigate fundamental phenomena of polymers at interfaces, covering adsorption, interactions between polymer layers and surfactants, surface forces and friction between adsorbed layers. A branched brush layer with high water content was formed on silica surfaces by a diblock copolymer, (METAC)m-b-(PEO45MEMA)n, via physisorption. The adsorption properties were determined using several complementary methods. Interactions between pre-adsorbed branched brush layers and the anionic surfactant SDS were investigated as well. Surface forces and friction between polymer layers in aqueous media were investigated by employing the Atomic Force Microscopy (AFM) colloidal probe technique. Friction forces between the surfaces coated by (METAC)m-b-(PEO45MEMA)n in water are characterized by a low friction coefficient. Further, the layers remain intact under high load and shear, and no destruction of the layer was noted even under the highest pressure employed, about 50 MPa. Interactions between polymer layers formed by a temperature responsive diblock copolymer, PIPOZ60-b-PAMPTMA17 (phase transition temperature of 46.1 °C), was investigated in the temperature interval 25-50 °C by using the AFM colloidal probe technique. Friction between the layers increases with increasing temperature (25-45 °C), while at 50 °C friction was found to be slightly lower than that at 45 °C. We suggest that this is due to decreased energy dissipation caused by PIPOZ chains crystallizing in water above the phase transition temperature. The structure of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) bilayers was determined by X-ray reflectometry. Surface forces and friction between DPPC bilayer-coated silica surfaces were measured utilizing the AFM colloidal probe technique. Our study showed that DPPC bilayers are able to provide low friction forces both in the gel (below ≈ 41°C) and in the liquid crystalline state (above ≈ 41°C). However, the load bearing capacity is lower in the gel state. This is attributed to a higher rigidity and lower self-healing capacity of the DPPC bilayer in the gel state. Friction forces in single asperity contact acting between a micro-patterned silicon surface and an AFM tip was measured in air. We found that both nanoscale surface heterogeneities and the µm-sized depressions affect friction forces, and considerable reproducible variations were found along a particular scan line. Nevertheless, Amontons’ first rule described average friction forces reasonably well. Amontons’ third rule and Euler’s rule were found to be less applicable to our system.

QC 20141209

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39

Hochmann, David. "Friction force excitations in spur and helical involute parallel axis gearing /." The Ohio State University, 1997. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487948158628115.

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Hansson, Petra M. "Hydrophobic surfaces: Effect of surface structure on wetting and interaction forces." Doctoral thesis, KTH, Yt- och korrosionsvetenskap, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-103409.

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The use of hydrophobic surfaces is important for many processes both in nature and industry. Interactions between hydrophobic species play a key role in industrial applications such as water-cleaning procedures and pitch control during papermaking but they also give information on how to design surfaces like hydrophobic mineral pigments. In this thesis, the influence of surface properties on wetting and interaction forces has been studied. Surfaces with close-packed particles, pore arrays, randomly deposited nanoparticles as well as reference surfaces were prepared. The atomic force microscope (AFM) was utilized for force and friction measurements while contact angles and confocal Raman microscopy experiments were mainly used for wetting studies. The deposition of silica particles in the size range of nano- to micrometers using the Langmuir-Blodgett (LB) technique resulted in particle coated surfaces exhibiting hexagonal close-packing and close to Wenzel state wetting after hydrophobization. Force measurements displayed long-range interaction forces assigned to be a consequence of air cavitation. Smaller roughness features provided larger forces and interaction distances interpreted as being due to fewer restrictions of capillary growth. Friction measurements proved both the surface structure and chemistry to be important for the observed forces. On hydrophobic pore array surfaces, the three-phase contact line of water droplets avoided the pores which created a jagged interface. The influence of the pores was evident in the force curves, both in terms of the shape, in which the three-phase contact line movements around the pores could be detected, as well as the depth of the pores providing different access and amount of air. When water/ethanol mixtures were used, the interactions were concluded to be due to ethanol condensation. Confocal Raman microscopy experiments with water and water/ethanol mixtures on superhydrophobic surfaces gave evidence for water depletion and ethanol/air accumulation close to the surface. Force measurements using superhydrophobic surfaces showed extremely long-range interaction distances. This work has provided evidence for air cavitation between hydrophobic surfaces in aqueous solution. It was also shown that the range and magnitude of interaction forces could, to some extent, be predicted by looking at certain surface features like structure,roughness and the overall length scales.

QC 20121011

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41

Nasrallah, Hussein. "Capillary adhesion and friction : an approach with the AFM Circular Mode." Phd thesis, Université du Maine, 2011. http://tel.archives-ouvertes.fr/tel-00651818.

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The aim of this thesis is concerned with the influence of sliding velocity on capillary adhesion at the nanometer scale. In ambient conditions, capillary condensation which is a thermally activated process, allows the formation of a capillary meniscus at the interface between an atomic force microscope (AFM) probe and a substrate. This capillary meniscus leads to a capillary force that acts as an additional normal load on the tip, and affects the adhesion and friction forces. The Atomic Force Microscopy (AFM) offers interesting opportunities for the measurement of surface properties at the nanometer scale. Nevertheless, in the classical imaging mode, limitations are encountered that lead to a non stationary state. These limitations are overcome by implementing a new AFM mode (called Circular AFM mode). By employing the Circular AFM mode, the evolution of the adhesion force vs. the sliding velocity was investigated in ambient conditions on model hydrophilic and hydrophobic surfaces with different physical-chemical surface properties such as hydrophilicity. For hydrophobic surfaces, the adhesion forces or mainly van der Waals forces showed no velocity dependence, whereas, in the case of hydrophilic surfaces, adhesion forces, mainly due to capillary forces follow three regimes. From a threshold value of the sliding velocity, the adhesion forces start decreasing linearly with the logarithm increase of the sliding velocity and vanish at high sliding velocities. This decrease is also observed on a monoasperity contact between a atomically flat mica surface and a smooth probe, thus eliminating the possibility of the kinetics of the capillary condensation being related to a thermally activated nucleation process as usually assumed. Therefore, we propose a model based on a thermally activated growth process of a capillary meniscus, which perfectly explains the experimental results. Based on these results, we focused on directly investigating with the Circular mode the role of capillary adhesion in friction mechanisms. We investigated the influence of the sliding velocity on the friction coefficient, and a decrease following three regimes, similar to the sliding velocity dependence of the capillary adhesion, was observed for hydrophilic surfaces that possess a roughness higher than 0.1 nm. Whereas, an increase of the friction coefficient was observed on hydrophilic (Mica) or hydrophobic (HOPG) atomically flat surfaces that posses a roughness lower than 0.1 nm. However, in this latter case, the three regimes are not established. Finally, on a rough hydrophobic surface, the friction coefficient was sliding velocity independent. A direct comparison with capillary adhesion behavior with the sliding velocity is expected to give new insights to explain this interplay.

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42

Staheli, Kimberlie. "Jacking Force Prediction: An Interface Friction Approach based on Pipe Surface Roughness." Diss., Available online, Georgia Institute of Technology, 2006, 2006. http://etd.gatech.edu/theses/available/etd-07052006-203035/.

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Thesis (Ph. D.)--Civil and Environmental Engineering, Georgia Institute of Technology, 2007.
Dr. J. David Frost, Committee Chair ; Dr. G. Wayne Clough, Committee Co-Chair ; Dr. William F. Marcuson III, Committee Member ; Dr. Paul W. Mayne, Committee Member ; Dr. Susan Burns, Committee Member.

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Unsal, Memet. "Force control of a new semi-active pieozoelectric-based [sic] friction damper." [Gainesville, Fla.] : University of Florida, 2002. http://purl.fcla.edu/fcla/etd/UFE1001189.

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Stahl, Aaron L. "Experimental Measurements of Longitudinal Load Distributions on Friction Stir Weld Pin Tools." Diss., CLICK HERE for online access, 2005. http://contentdm.lib.byu.edu/ETD/image/etd1018.pdf.

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von, Mackensen Jana. "Thinking Friction : Uncover the true colours of Berlin." Thesis, KTH, Stadsbyggnad, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-100151.

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Tarasova, Anna Optometry UNSW. "Fabrication and characterisation of affinity-bound liposomes." Awarded by:University of New South Wales. Optometry, 2007. http://handle.unsw.edu.au/1959.4/29114.

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In considering the concept of surface-immobilised liposomes as a drug release system, two factors need to addressed, the interfacial surface density of the liposomes for maximum drug loading and the stability of these liposomes to allow for controlled drug release. This thesis investigates a multilayer system for the affinity immobilisation of liposomes and their stability to various applied stresses. In the work presented here an allylamine monomer was used to create plasma coatings that were stable, thin and amine-rich. The aging studies using AFM showed these films to rapidly oxidise on exposure to water. The freshly deposited films were used for further surface modifications, by the covalent grafting of PEG layers of different interfacial densities under the conditions of varying polymer solvation. The AFM was used to measure the interaction forces between the grafted PEG layers and modified silica interfaces. It was found that the polydispersity of the PEG species resulted in bridging interactions of ???brush???-like PEG layers with the silica surface. These interactions were screened minimised by increasing the ionic strength of the solution. Although the densely grafted PEG layers were found to be highly protein-resistant by the XPS and QCM-D some minor protein-polymer adhesions were observed by the AFM. The densely anchored biotinylated PEG chains served as an optimum affinity platform for affinity-docking of NeutrAvidinTM molecules, which assembled in a rigid, 2-D layer as confirmed by the QCM-D. The submonolayer surface density of NeutrAvidin, as determined by Europium-labelling, was attributed to steric hindrance of the immobilised molecules. The final protein layer enabled specific binding of biotin-PEG-liposomes as a highly dissipative, dense and stable layer verified by tapping mode AFM and QCM-D. We found that these liposomes were also stable under a range of stresses induced by the shearing effects of water, silica probe and HSA layer at increased loads and velocities. The frictional response of the liposome layer also demonstrated the viscoelasticity and stability of these surface immobilised liposomes. Finally, the minimal adhesive interaction forces, as measured by the AFM, demonstrated the repellency of these liposomes to commonly found proteins, such as HSA.

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Madhani, Akhil J. (Akhil Jiten) 1968. "Design and motion planning of robotic systems subject to force and friction constraints." Thesis, Massachusetts Institute of Technology, 1991. http://hdl.handle.net/1721.1/13027.

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Seneviratne, Vajira Namal. "Friction force microscopy using self-assembled monolayers : molecular scale roughness and chiral interactions." Thesis, University of Cambridge, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.614350.

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Vyas, Mukesh Kumar. "Nanoscale Investigation of Adhesion, Friction, and Wear in Chemically Heterogeneous Responsive Polymer Brushes." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2008. http://nbn-resolving.de/urn:nbn:de:bsz:14-ds-1226414812035-21826.

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Polymer brushes provide the responsive smart surfaces which can be used for fabrication of various devices. In this thesis work, adhesion, friction, and wear of polystyrene (PS) - poly(2-vinyl pyridine) (P2VP) and polystyrene - poly(acrylic acid) (PAA) binary brushes and corresponding monobrushes were investigated in dried state under controlled environment. Spin-coated films were also investigated for comparison. The aim was to explore possibilities to control/tune adhesion, friction, and wear between inorganic or polymeric surfaces by use of polymer brushes. Atomic force microscopy (AFM) with sharp silicon nitride tip and colloidal probes was employed to investigate the nanoscale adhesion and friction forces between different inorganic and polymeric surfaces. Adhesion and friction on the polymer brushes were comparable to that on the spin-coated films. Adhesion and friction force values were correlated, and were in accordance with the wettability of the brush surfaces for most of the samples. Switching in the adhesion and friction forces was observed for the PS+P2VP and PS+PAA binary brushes on treatment with selective solvents. Maximum switching in adhesion force and friction coefficient was by a factor of 2.7 and 5.4, respectively. Furthermore, switching of friction for mixed brush surface was observed during macroscale friction measurements using nanoindenter. Friction coefficients at macroscale were higher than those at the nanoscale. Moreover, adhesion and friction forces between the surfaces were significantly influenced by the humidity, grafting density of polymer brushes, chemical composition of top of the binary brush surface, and tip scan velocity. Nanowear studies were carried out with AFM using sharp silicon nitride tip while macrowear studies were carried out using nanoindenter. Nanowear on the surfaces was affected by molecular entanglements, adhesion and friction forces as well as shape and status of the tip. It was observed that the typical wear mode for PS brushes (treated with toluene) was ripple formation. In case of P2VP brushes (treated with ethanol) and PAA brushes (treated with pH 10 water), wear occurred via removal of the polymeric material. Wear mechanism observed for the monobrushes was similar to that observed for the spin-coated thick films of the same polymeric material. However, extent of the wear on the brush surfaces significantly differed from that on the spin-coated films. In case of PS+P2VP and PS+PAA binary brush samples, change in the wear mode was observed on treatment with the different selective solvents. On treatment with toluene (PS on the top), both of these binary brushes showed the wear by formation of the ripples. On the other hand, when these binary brushes were treated with selective solvent for P2VP or PAA, wear occurred mainly via removal of the polymeric material. The amount of wear increased with the number of scans for all the polymer brush samples. Moreover, wear on the polymer brush surfaces was also increased on increase in the applied load and decrease in the scan speed. Wear behavior on macroscale was averaged due to contact between surfaces at large number of asperities. Our results show that adhesion, friction, and wear of polymer surfaces can be controlled/tuned by the use of binary polymer brushes.

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50

Georgiou, Kyriakos V. "Analysis and numerics for the local and global dynamics of periodically forced nonlinear pendula." Thesis, University of Surrey, 2000. http://epubs.surrey.ac.uk/842943/.

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This thesis involves the analysis of four classes of nonlinear oscillators. We investigate a damped planar pendulum subject to vertical sinusoidal displacement of appropriate amplitude and frequency, a Hamiltonian planar pendulum with support point oscillating in the vertical direction, a forced spherical pendulum as a constrained dynamical system and a spinning double pendulum with the two masses oscillating in transversal planes. The motivation for this research was to understand and determine the fundamental dynamical properties of the four model systems. For this purpose analytical and numerical tools have been employed. Linearization, phase portraits, Poincare sections, basins of attraction, KAM theory, Lyapunov exponents and normal form theory have been considered as examples. For the damped planar pendulum a rigorous analysis is presented in order to show that, in the presence of friction, the upward equilibrium position becomes asymptotically stable. Furthermore, using numerical tools, the dynamics of the system far from its equilibrium points is systematically investigated. For the undamped and parametrically perturbed planar pendulum, we use KAM type arguments to rigorously prove the stability of the equilibrium point corresponding to the upside-down position. For the spherical pendulum a numerical framework is developed, which allows orbits to explore the entire sphere. We show that the qualitative change in the Poincare sections from regular to chaotic behaviour is in excellent qualitative agreement with corresponding computations of the Lyapunov exponents. Finally we study the dynamics of the spinning double pendulum by using normal form theory. We have identified the regions in physical parameter space where a codimension-two singularity occurs. An algorithm for the Cushman-Sanders normal form is constructed and analyzed. A representative model for the truncated normal form is presented.

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