Dissertations / Theses on the topic 'Surface stress'
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Mansfield, Mark. "Surface stress and reconstructions on metal surfaces." Thesis, University of Cambridge, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.359866.
Full textHarrison, Michael James. "Density functional theory investigations of surface stress and surface structure." Thesis, University of Warwick, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.429720.
Full textBradley, Matthew K. "Density functional theory investigations of surface structure and surface stress in adsorbate layers on Cu, Pd and Ir surfaces." Thesis, University of Warwick, 2012. http://wrap.warwick.ac.uk/51619/.
Full textTabard-Cossa, Vincent. "Microcantilever actuation generated by redox-induced surface stress." Thesis, McGill University, 2005. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=102214.
Full textThe objective of the present study is to gain a better understanding of the mechanisms responsible for the nanomechanical motion of cantilever sensors during adsorption and absorption processes. The study of these simple model systems will lead to a general understanding of the cantilever-based sensor's response and provide insights into the physical origin of the measured surface stress.
The surface stress generated by the electrochemically-controlled absorption of ions into a thin polypyrrole film is investigated. A compressive change in surface stress of about -2 N/m is measured when the polymer is electrochemically switched between its oxidized and neutral (swollen) state. The volume change of the polymer phase with respect to the gold-coated cantilever is shown to be responsible for the mechanical motion observed.
The potential-induced surface stress and surface energy change on an Au(111)-textured cantilever, in a 0.1 M HClO4 electrolyte, are simultaneously measured. These measurements revealed that for solid electrodes these two thermodynamic parameters are significantly different. In the double layer region, a surface stress change of -0.55 +/-0.06 N/m is measured during ClO4- adsorption whereas the surface energy variation is smaller by one order of magnitude. The origin of the surface stress change at the metal-electrolyte interface is understood by the variation in electron density at the surface which alters the inter-atomic bonds strength between surface atoms, while the specificity of adsorption of ions is found to be mostly responsible for the fine structure of the surface stress profile.
Godfrey, Michael John. "Quantum-mechanical theory of stress and its applications." Thesis, University of Cambridge, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.279694.
Full textChua, Bun Hiong. "Investigation into the stress assisted damage of copper surface under single asperity influence of contact pressures, surfaces stress states and environments /." [Ames, Iowa : Iowa State University], 2008.
Find full textCelik, Aytac. "Investigation Of Electromigration And Stress Induced Surface Dynamics On The Interconnect By Computer Simulation." Phd thesis, METU, 2011. http://etd.lib.metu.edu.tr/upload/12613146/index.pdf.
Full textABU-NABAH, BASSAM ABDEL JABER. "EDDY CURRENT SPECTROSCOPY FOR NEAR-SURFACE RESIDUAL STRESS PROFILING IN SURFACE TREATED NONMAGNETIC ENGINE ALLOYS." University of Cincinnati / OhioLINK, 2007. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1186763648.
Full textHays, Richard A. "Surface residual stress effects on stress corrosion cracking/hydrogen embrittlement behavior of AISI 4340 steel." Thesis, Virginia Polytechnic Institute and State University, 1988. http://hdl.handle.net/10919/80148.
Full textMaster of Science
Barrans, Simon Mark. "Enhancing finite element analysis boundary stress predictions." Thesis, University of Huddersfield, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.338613.
Full textGodin, Michel. "Surface stress, kinetics, and structure of alkanethiol self-assembled monolayers." Thesis, McGill University, 2004. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=85551.
Full textThese measurements were performed in order to gain insight into the mechanisms involved in the self-assembly process and into the origins of the associated surface stress. Moreover, these studies were used to characterize and optimize the response of cantilever-based sensors based on functionalized SAM technology in terms of reliability, sensitivity, and reproducibility.
The evolution of the surface stress induced during alkanethiol SAM formation reveals features associated with coverage-dependent structural phase transitions. These results show that both the kinetics of SAM formation and the resulting SAM structure are strongly influenced by the surface structure of the underlying gold substrate, by the impingement rate of the alkanethiol molecules onto the gold surface, and by the cleanliness of the gold surface. In particular, it was found that a minimum gold grain size is necessary in order for the SAM to achieve the standing-up phase, for which large compressive surface stresses (~10 N/m) are measured. In addition, these results show that alkanethiol SAMs can become kinetically trapped in metastable intermediate states (lying-down phase) for formation on small-grained gold surfaces and/or at low alkanethiol vapor concentrations. Theoretical modeling of the origins of the induced surface stress reveals that inter-molecular Lennard-Jones interactions and electrostatic repulsion between adsorbed species play minimal roles in the development of the surface stress. Changes in the electronic structure of the underlying gold substrate are more likely to account for the large compressive surface stresses observed during alkanethiol SAM formation.
Ngiam, Shi Song. "The influence of surface residual stress on fatigue crack growth." Thesis, University College London (University of London), 2007. http://discovery.ucl.ac.uk/1444870/.
Full textLewis, Trevor Stephen. "The form-finding of structures possessing a constant surface stress." Thesis, University of Warwick, 1997. http://wrap.warwick.ac.uk/39026/.
Full textLiangruksa, Monrudee. "Effect of Surface Stress on Micromechanical Cantilevers for Sensing Applications." Thesis, Virginia Tech, 2008. http://hdl.handle.net/10919/34043.
Full text Model III for surface stress loading effect is then used to demonstrate the applications of a microcantilever in sensor technology through the measurement of tip deflection under an atomic adsorption as the source of surface stress. Dual
attractive or repulsive characteristics of interactions between a pair of mercury atoms are described in terms of Lennard-Jones potential. The force per unit atomic spacing induced by the adjacent free surface atoms of a monolayer is then computed using the potential. The sensitivities of atomic spacing and monolayer thickness to the tip-deflection of a
microcantilever are studied in this research.
Master of Science
Jørgensen, Loren. "Wetting of yield-stress fluids : capillary bridges and drop spreading." Thesis, Lyon, 2016. http://www.theses.fr/2016LYSE1163/document.
Full textWetting phenomena and yield-stress fluids rheology are subfields of soft matter physics where big understanding steps have been made during the last centuries. In addition, these two fields have very important potential implications for industry, which contributes to their dynamism. But their combination, the wetting of yield-stress fluids, has received little interest until the very last years, although it is a situation that happens all the time. Indeed, yield-stress fluids gather nearly all the fluids encountered in food industry, cosmetics, building industry, oil and gas industry… and wetting properties are crucial when processing or using the fluids, as many processes involve interfaces with air or a solid surface.In this thesis, I consider the following questions: how is the apparent surface tension affected by yield stress? How does the yield stress influence the wetting dynamics, classically described by Tanner’s law? Why can the final contact angle of a sessile drop of yield-stress fluid not be predicted by Young-Dupré’s theory?I performed experiments with a model yield-stress fluid called carbopol. The first experiment consisted in measuring the adhesion force of a capillary bridge and comparing it to the case of simple fluids. The main results show the importance of the deformation history and of the fluid elasticity. The second main experiment concerned spreading of drops on a hydrophilic surface. I studied the short-time dynamics and the long-time dynamics, as well as the final contact angle. The first regime is controlled by viscoelasticity, whereas the final state is determined by the yield stress
Al-Mayali, Maasi. "Plastic deformation and residual stress of surface roughness asperities in elastohydrodynamic contact with consideration of surface fatigue." Thesis, Cardiff University, 2017. http://orca.cf.ac.uk/103494/.
Full textShapiro, Karen Naomi. "'The effect of residual stress and surface condition on the stress corrosion cracking of austenitic stainless steel'." Thesis, University of Manchester, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.499863.
Full textGullbrand, Jörgen. "The influence of stress variations in wet pressing." Licentiate thesis, KTH, Fibre and Polymer Technology, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-1758.
Full textTwo methods for the measurement of micro-scale stressvariations of press felt surfaces were developed. The methodswere based on a thin plastic film that was coated with anopaque stress-sensitive layer (Cronapress conversion film). Thefilm was compressed between a felt and a smooth surface. Uponapplication of load the opaque layer became partiallytransparent at the locations where load was applied by thesurface fibres of the felt. The degree of transparency was afunction of the locally applied stress. The spatial resolutionof the method was 6.3 µm, which means that even details ofthe order of the diameter of a batt fibre diameter can beresolved.
Parameters characterising the stress variations were used toquantitatively describe the extent of the stress variations,the size of the contact areas and the distance between them.The applicability of these contact characterisation parameterswas evaluated in laboratory wet pressing experiments and inpilot paper machine trials for two sets of specially designedpress felts. In general, the dewatering result was mainlyinfluenced by the diameter of the felt surface batt fibres andby the web grammage. For a specific pulp type and operatingconditions a multivariate model was formulated based on themeasured web dryness, web grammage and each contactcharacterisation parameter. The model was able to describe thedewatering capability of the different felts tested. Contactcharacterisation parameters related to contact properties (e.g.contact area ratio) gave the best prediction for low grammagewebs, while parameters related to flow properties (e.g. size ofopenings) gave the best prediction for high grammage webs.
Furthermore it was found that at a certain web grammage, thesurface batt fibre diameter did not have an influence on thedewatering result. This grammage was termed "transitiongrammage". Below the transition grammage a fine surface gavesignificantly better dewatering, while the opposite trend wasobserved above the transition grammage. Based on these results,a modified dewatering hypothesis was formulated. Thishypothesis links the non-uniform compression of the wet webwith different dewatering situations for low and high grammagewebs.
KeywordsPress felts, Roughness, Smoothness, SurfaceStructure, Uniformity, Wet pressing, Batt fibre, Base weave,Stress variations, Micro-scale.
Noriega, Motta Julio Amilcar. "Portable transparent indenter instrumentation for material surface characterization." Morgantown, W. Va. : [West Virginia University Libraries], 2006. https://eidr.wvu.edu/etd/documentdata.eTD?documentid=4765.
Full textTitle from document title page. Document formatted into pages; contains xiii, 105 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 97-98).
Hakim, Ali. "Characterization of Hard Metal Surfaces after Various Surface Process Treatments." Thesis, Linköping University, The Department of Physics, Chemistry and Biology, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-12433.
Full textThe aim of this thesis is to investigate how material surfaces are affected by various surface treatments and how this relates to the adhesion of the coating. The materials that were studied were WC-Co and Cermets and the surface treatments used were polishing, grinding with coarser and finer abrasive grains, and finally wet blasting and dry blasting. Focus was on deformations and residual stresses in the surface, surface roughness and cracks. The test methods used for examining the samples included surface roughness measurements, residual stress measurements, adhesion tests using Rockwell indentation and SEM images of the surface and the cross section.
The results concluded that polishing gives very good adhesion. Additionally, the adhesion for ground surfaces was good for WC-Co but very poor for Cermets. Furthermore, it was observed that finer abrasive grains did not result in better adhesion. In fact, the coarser grains gave slightly better results. Finally, it was concluded that wet blasting has a clear advantage over dry blasting and results in much better adhesion, especially for the Cermets. The results for the WC-Co were a bit inconsistent and so further research is required.
Sabetnia, Sahar Z. S. "Studies on the regulation and role of the cell integrity pathway of Saccharomyces cerevisiae." Thesis, University of Glasgow, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.248131.
Full textMonga, Tanya. "Surface stress at the solid-liquid interface : alkanethiol monolayers on gold." Thesis, McGill University, 2006. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=101628.
Full textDuhaut, Thomas H. A. "Wind-driven circulation : impact of a surface velocity dependent wind stress." Thesis, McGill University, 2006. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=101117.
Full textThe ocean current signature is clearly visible in the scatterometer-derived wind stress fields. We argue that because the actual ocean velocity differs from the modeled ocean velocities, care must be taken in directly applying scatterometer-derived wind stress products to the ocean circulation models. This is not to say that the scatterometer-derived wind stress is not useful. Clearly the great spatial and temporal coverage make these data sets invaluable. Our point is that it is better to separate the atmospheric and oceanic contribution to the stresses.
Finally, the new wind stress decreases the sensitivity of the solution to the (poorly known) bottom friction coefficient. The dependence of the circulation strength on different values of bottom friction is examined under the standard and the new wind stress forcing for two topographic configurations. A flat bottom and a meridional ridge case are studied. In the flat bottom case, the new wind stress leads to a significant reduction of the sensitivity to the bottom friction parameter, implying that inertial runaway occurs for smaller values of bottom friction coefficient. The ridge case also gives similar results. In the case of the ridge and the new wind stress formulation, no real inertial runaway regime has been found over the range of parameters explored.
Guskey, Christopher R. "NEAR WALL SHEAR STRESS MODIFICATION USING AN ACTIVE PIEZOELECTRIC NANOWIRE SURFACE." UKnowledge, 2013. http://uknowledge.uky.edu/me_etds/27.
Full textNasseri, Mahnaz. "The relationship between surface heat transfer and stress generation in components." Thesis, Sheffield Hallam University, 1993. http://shura.shu.ac.uk/20111/.
Full textMartinez, Hurtado Alonso. "An integrated laser cladding and stress improvement for enhancing surface properties." Thesis, University of Manchester, 2016. https://www.research.manchester.ac.uk/portal/en/theses/an-integrated-laser-cladding-and-stress-improvement-for-enhancing-surface-properties(83659199-bfe1-4adb-850c-2dcc9e5334f4).html.
Full textMarks, Christopher R. "Surface Stress Sensors for Closed Loop Low Reynolds Number Separation Control." Wright State University / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=wright1309998636.
Full textArli, Sirisha Divya. "An Investigation on the Stress Intensity Factor of Surface Micro-cracks." Wright State University / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=wright1495620917553525.
Full textYanagi, Junior Tadayuki. "Partial surface wetting to relieve acute thermal stress of laying hens." Universidade Federal de Viçosa, 2002. http://www.locus.ufv.br/handle/123456789/11515.
Full textMade available in DSpace on 2017-07-28T13:57:52Z (GMT). No. of bitstreams: 1 texto completo.PDF: 1092273 bytes, checksum: 61189e2f9ff1c859ecd3bbb9a9959c9a (MD5) Previous issue date: 2002-02-28
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
Um sistema de medição e controle foi desenvolvido para o estudo de respostas fisiológicas de aves sujeitas a mudanças térmicas como meio de alívio de estresse térmico. O sistema faz o controle automático da temperatura (t a,SP ±0,2 oC) e da umidade relativa do ar (RH SP ±2 %); sendo que a velocidade do ar foi controlada manualmente (V SP ±0,1 m· s -1 ); e contínuo armazenamento das termografias (ex., temperatura superficial, t surf ) e da temperatura corporais (t b ) dos animais. As condições térmicas controladas na zona de ocupação animal (AZO) são atingidas pela operação de um pequeno túnel de vento (V = 0 to 1,5 m· s -1 ) colocado no interior de uma sala ambiental com t a e RH controlados (5,0 m comprimento × 3,5 m largura × 3,0 m altura). Os valores desejados de t a e RH foram alcançados por meio de aquecedores e umidificadores controlados em dois estágios via um módulo de controle e medição programável, e periféricos. Termografias (discernabilidade de 0.06°C) são adquiridas com uma camera infravermelho cuja operação é controlada remotamente por um PC. t b (±0.1°C) é armazenado em uma unidade de telemetria, sem a necessidade de intervenção cirurgica, que também é conectado a um PC. Em adição, um sistema de video tem sido usado para observar e arquivar os comportamentos do animal. A instrumentação desenvolvida foi usada em um experimento para ajustar equações empíricas para descrever as necessidades de molhamento parcial da superfície em galinhas poedeiras (Hy-Line W98, com 34 ± 1 semanas) sujeitas a condições de estresse térmico. A água necessária para limitar o aumento da temperatura superficial das galinhas foi expressada em termos de intervalo de aspersão (SI 10 , min) para uma dosagem constante (10 ml· aspersão -1 ) ou para uma taxa de evaporação (ER, ml.min -1 ) de água aspergida. As exposições térmicas consistiram de uma combinação fatorial de 3 temperaturas de bulbo seco (t db ) (35, 38 e 41 °C) x 2 temperaturas de ponto de orvalho (t dp ) (21,1 e 26,7 °C) x 3 velocidades do ar (V) (0,2, 0,7 e 1,2 m· s -1 ). As condições ambientais foram expressas como 18 combinações de déficit de vapor de pressão do ar (VPD air ) x V. ER foi diretamente proporcional ao produto VPD air · V . As relações podem servir como a base para a otimizar o sistema de resfriamento superficial intermitente para alívio de estresse térmico em galinhas criadas em gaiolas. Ademais, um índice de desconforto térmico (TDI) foi derivado com base nas respostas fisiológicas, temperatura superficial (t surf ) e temperatura corporal (t b ), de galinhas sujeitas a exposições térmicas. Com base no aumento da t b aos 50 min de exposição térmica (Δt b,50 ), um TDI foi relacionado ao VPD air e a V da seguinte forma: TDI = -15.17 + 18.62 (t db ) n – 0.92 · (VPD air · V ) n . Usando TDI, quatro zonas de desconforto térmico (segura, alerta, perigo e fatal) foram definidas para as várias combinações de condições térmicas. Um modelo teórico de transferência de calor e massa em regime transiente também foi proposto para predizer Δt b,50 em função das condições ambientais, das condições fisiológicas das aves e do nível de molhamento (β). O modelo proporciona uma ferramenta conveniente e interativa para determinar Δt b,50 nas galinhas submetidas ou não ao molhamento superficial para t db variando de 35 a 38 °C.
A control and measurement system was developed for studying physiological responses of poultry to thermal challenges and means of thermal stress relief. The system features automatic control of air temperature (t a,SP ±0.2 oC) and relative humidity (RH SP ± 2 %); manual setting of air velocity (V SP ± 0.1 m· s -1 ); and continuous recording of thermographs (i.e., core body temperature (t b ) of the animal. surface temperature, t surf ) and The controlled thermal conditions in the animal-occupied zone (AOZ) are achieved through operation of a small wind tunnel (V = 0 to 1.5 m· s -1 ) inside a t a - and RH-controlled environmental room (5 m L × 3.5 m W × 3.0 m H). Target t a and RH values are achieved by controlling auxiliary heaters and humidifiers in two stages via a programmable measurement and control module and peripherals. Thermographs (0.06°C discernability) are acquired with an infrared (IR) imager whose operation is remotely controlled by a PC. Core body temperature (t b , ±0.1°C) is recorded with a surgery-free telemetric sensing unit that is also interfaced with a PC. In addition, a video monitoring system is used to observe and archive animal behaviors. The instrumentation developed was used in an experiment to establish empirical equations to describe the need of partial surface wetting for cooling laying hens (Hy-Line W-98, 34 ±1 wk old) subjected to a range of thermal stress conditions. The thermal exposures consisted of a factorial combination of 3 dry bulb temperatures (t db ) (35, 38 and 41 °C) × 2 dew point temperatures (t dp ) (21.1 and 26.7 ° C) × 3 air velocities (V) (0.2, 0.7 and 1.2 m· s - ). The environmental conditions were expressed as 18 combinations of air vapor pressure deficit (VPD air ) × V. The water necessary to limit hen surface temperature from rising was expressed in terms of sprinkle interval (SI 10 , min) for a constant spray dosage (10 ml· spray -1 ) or evaporation rate (ER, ml· min -1 ) of the sprayed water. ER was directly proportional to VPD air · V . The relationships may serve as the basis for optimizing an intermittent partial surface cooling system for thermal stress relief of caged layers. Also from the study, a thermal discomfort index (TDI) was derived based on physiological responses, surface temperature (t surf ) and core body temperature (t b ) of the control (non-cooled) hens. Based on t b rise after 50 min of thermal exposure (Δt b,50 ), TDI related to VPD air and V as: TDI = -15.17 + 18.62 (t db ) n – 0.92· (VPD air · was V ) n . Using TDI, four zones of thermal discomfort (safe, alert, danger, and fatal) were defined for various combinations of thermal conditions. Furthermore, theoretical transient heat and mass transfer model was proposed to predict Δt b,50 as a function of environmental conditions, physiological responses of the hens and surface wetness level (β). The model provides a convenient, interactive tool for determining Δt b,50 on wetted and non-wetted hens for t db ranging from 35 to 38 °C.
Crowson, Douglas A. "Stability of Nanoporous Metals." Diss., Virginia Tech, 2006. http://hdl.handle.net/10919/28111.
Full textPh. D.
Lao, Wai Keong. "Stress intensity factors for deep circumferential external surface cracks in hollow cylinders." Thesis, University of Macau, 2004. http://umaclib3.umac.mo/record=b1445132.
Full textJayanta, Joglekar Sameer. "Surface and mechanical stress effects in AlGaN/GaN high electron mobility transistors." Thesis, Massachusetts Institute of Technology, 2017. http://hdl.handle.net/1721.1/111325.
Full textCataloged from PDF version of thesis.
Includes bibliographical references (pages 153-161).
Gallium Nitride (GaN) belongs to a class of materials called wide band-gap semiconductors. In recent years, the versatile nature of this material has been exploited for a wide range of applications from solid state lighting to RF and microwave communication, as well as high power switching. The first part of this thesis discusses planar AlGaN/GaN transistors. GaN is a piezoelectric material, and changes in mechanical stress result in a change in the charge density which in turn affects the maximum current in AlGaN/GaN transistors. Finite element modelling techniques were applied to quantify the mechanical stress distribution in planar AlGaN/GaN RF transistors resulting from device fabrication, and operation in the on- and off-state. Thereafter, two important surface and interface effects were studied in this thesis. In the first one, the impact of surface cleanings, surface treatments and plasma-based dry etch conditions on two different types of ohmic contact technologies was investigated. Contact resistance measurements were correlated with surface characterization results. The second was that of interface positive charges at the Al₂O₃-GaN interface and the increase in electron density in the device resulting from them. In both these problems, a combination of device electrical measurements and material characterization techniques was used to establish direct correlations between device behavior and material properties. The second part of the thesis deals exclusively with nano-ribbon (NR) or fin-like AlGaN/GaN transistors. Fundamental transport properties of charge density and mobility in NR devices were studied in order to understand the difference in behavior of these devices from planar devices. The influence of passivation films on the charge density in these structures was investigated, using Al₂O₃ passivation as a specific example. Electron mobility degradation due to sidewall-scattering in NR devices was quantified using different mobility extraction methods based on device measurements. The thesis concludes with a potential application of NR AlGaN/GaN transistors for high linearity power amplification. A new kind of transistor with varying threshold voltages along the gate width is proposed to improve the DC and RF linearity of GaN-based devices.
by Sameer Jayanta Joglekar.
Ph. D.
Liang, L. H., and Y. G. Wei. "Ultralow Thermal Conductivity and Thermal Stress of Ceramics with Surface Nanowire-structures." Thesis, Sumy State University, 2012. http://essuir.sumdu.edu.ua/handle/123456789/34880.
Full textKim, Tae Hyun. "Fatigue of surface engineered steel in rolling-sliding contact." Thesis, Imperial College London, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.325019.
Full textAdiguzel, Sinem. "Determining Surface Residual Stress In Steel Sheets After Deep Drawing And Bulging Processes." Master's thesis, METU, 2011. http://etd.lib.metu.edu.tr/upload/12613054/index.pdf.
Full textX-ray diffraction and Magnetic Barkhausen Noise. The experimental and simulation results were correlated with each other.
Wang, Xin. "Stress intensity factors and weight functions for surface cracked plates and welded joints." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape17/PQDD_0012/NQ30658.pdf.
Full textAfshari, Mana. "Nonlinear modeling of the adsorption-induced surface stress in piezoelectrically-driven microcantilever biosensors." Connect to this title online, 2007. http://etd.lib.clemson.edu/documents/1193078958/.
Full textHenderson, Marc Bryson. "Changes in Streambank Erodibility and Critical Shear Stress Due to Surface Subaerial Processes." Thesis, Virginia Tech, 2006. http://hdl.handle.net/10919/33114.
Full textMaster of Science
Tunde, Raji Abdulrafiu. "Changes in the near-surface stress in titanium caused by krypton ion-implantation." Master's thesis, University of Cape Town, 2006. http://hdl.handle.net/11427/6515.
Full textIncludes bibliographical references.
In this work, the effect of krypton implantation on the morphology of titanium samples is investigated through scanning electron microscopy (SEM). Rutherford backscattering spectrometry (RBS) was also used to determine the dose and depth of implanted krypton. The krypton profiile in titanium, and the associated damage profile, was modelled with TRIM calculations. In addition, metallurgical techniques were also used to examine the microstructure details of the as-received, unimplanted titanium sample.
Matheny, Ashley Michelle. "Quantifying the Sensitivity of Land-Surface Models to Hydrodynamic Stress Limitations on Transpiration." The Ohio State University, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=osu1364572098.
Full textYU, FENG. "NONDESTRUCTIVE EVALUATION OF NEAR-SURFACE RESIDUAL STRESS IN SHOT-PEENED NICKEL-BASE SUPERALLOYS." University of Cincinnati / OhioLINK, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1130282650.
Full textWard, David John. "Finite element modelling of stress development during deposition of ion assisted coatings." Thesis, University of Salford, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.366326.
Full textHansson, Tobias, and Kristoffer Skogsberg. "Comparison of stress behaviour in thermal barrier coatings using FE analyses." Thesis, Högskolan Väst, Institutionen för ingenjörsvetenskap, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:hv:diva-4285.
Full textBrady, Michael P. "Evaluation of laser surface melting to mitigate chloride stress corrosion cracking in an austenitic stainless steel." Thesis, This resource online, 1990. http://scholar.lib.vt.edu/theses/available/etd-03122009-040851/.
Full textKuok, Kin Man. "The stress intensity factors for deep semi-elliptical surface crack in finite-thickness plate." Thesis, University of Macau, 2002. http://umaclib3.umac.mo/record=b1445044.
Full textBergholz, Katharina. "An extended bounding surface model for the application to general stress paths in sand." Institut für Geotechnik, 2019. https://tud.qucosa.de/id/qucosa%3A72600.
Full textDie Prognose von Setzungen für die Bemessung von Infrastrukturbauwerken stellt hohe Anforderungen an die numerische Untersuchung des Baugrunds und das damit verbundene Stoffgesetz: komplexe Herstellungsprozesse und zyklisch wiederkehrende Verkehrslasten stellen beachtliche Herausforderungen dar. Während das Hauptaugenmerk zumeist auf der realitätsnahen Abbildung des Bodenverhaltens liegt und damit die analytischen Anforderungen des geotechnischen Problems im Fokus stehen, sollten die Bedürfnisse der Ingenieurspraxis in der Stoffgesetzmodellierung nicht außer Acht gelassen werden. In diesem Sinne wurde im Rahmen der Elastoplastizität ein neues Materialmodell für nichtbindige Böden entwickelt. Auf dem Konzept der Bounding Surface Plastizität nach Manzari und Dafalias (1997) beruhend, sind Eigenschaften wie Festigkeit, Steifigkeit und Dilatanz Funktion des Abstands zwischen aktuellem Spannungszustand und einer zugeordneten Modellfläche im Spannungsraum. Auf diese Weise bildet das Mehrflächenmodell fundamentale Verhaltensmuster von Boden korrekt ab, einschließlich beispielsweise scherbezogener Phänomene wie Ver- und Entfestigung, Kontraktanz und Dilatanz oder das Erreichen des kritischen Zustands (Scherfestigkeit bei konstantem Volumen). Des Weiteren erfasst das Modell die Zustandsabhängigkeit des Bodenverhaltens (Barotropie und Pyknotropie). So kann mit nur einem Parametersatz das mechanische Verhalten einer großen Spannweite unterschiedlicher Anfangszustände hinsichtlich Spannung und Lagerungsdichte simuliert werden. Der kinematische Verfestigungsmechanismus der konusförmigen Fließfläche trägt bei Ent- und Wiederbelastungen zu einer realistischeren Steifigkeitsentwicklung bei und ist damit von essenzieller Bedeutung für die Akkumulation von Spannungen oder Verformungen infolge von Lastwechseln. Da sich der gewählte konstitutive Rahmen für Weiterentwicklungen eignet, wurde die ursprüngliche Formulierung des Stoffgesetzes erweitert, um das Modell an die definierten Anforderungen anzupassen. Um geotechnisch relevante Spannungspfade niedriger und höherer Komplexität adäquat reproduzieren zu können, wurde zunächst eine kappenförmige Fließfläche ergänzt. So können irreversible Verformungen nicht nur bei Scherung, sondern auch bei Belastungen ohne Änderung des Spannungsverhältnisses, wie z. B. bei isotroper oder ödometrischer Kompression, auftreten. Bei Spannungspfaden ungewöhnlicher Orientierung, bei Lastwechseln oder zusammengesetzten Spannungspfaden mit Änderung der Belastungsrichtung hat sich eine erhöhte Steifigkeit bei kleinen Dehnungen mit anschließendem dehnungsabhängigen Abfall als nützlich erwiesen. Darüber hinaus berücksichtigt ein zusätzlicher Mechanismus die rückläufige Akkumulation von Spannung oder Verformung mit zunehmender Zyklenanzahl (mittels dissipierter Energie). Im Hinblick auf die Eignung des Stoffgesetzes für die Praxis ist das Modell modular aufgebaut. So kann die Komplexität des Modells (und damit die Anzahl der Parameter) durch Ein- und Ausschalten bestimmter Erweiterungen an die Komplexität des geotechnischen Problems angepasst werden. Die Mehrzahl der Modellparameter wird mit Hilfe konventioneller Laborversuche bestimmt. Eine interne Routine erleichtert durch die Kalibrierung bestimmter Bounding Surface bezogener Größen anhand eines alternativen, stärker an Versuchsergebnissen orientierten User-Inputs bei Bedarf die Parameterwahl. Da die Kenntnis eines Stoffgesetzes entscheidend ist für dessen vernünftigen und verantwortungsvollen Einsatz, soll die vorliegende Arbeit eine fundierte und umfassende Dokumentation bieten. Der erste Teil vermittelt daher zunächst einen Überblick über das zugrunde liegende Bounding Surface Konzept und beschreibt die Neuerungen auf konstitutiver Ebene mit Bezug auf theoretische Hintergründe. Er wird gefolgt von einer detaillierten Darlegung von Potenzialen und Einschränkungen für die Nutzung des erweiterten Modells. Der nächste Abschnitt widmet sich der numerischen Implementierung des Stoffgesetzes und seiner Kalibrierung auf Basis von Versuchsergebnissen. Des Weiteren wird die Kalibrierungsroutine einschließlich des verwendeten Optimierungsalgorithmus präsentiert. Der nachfolgende Teil dient der Modellvalidierung: durch die Simulation von Elementversuchen, die Erzeugung von Antwortellipsen sowie die Abbildung allgemeinerer (beispielsweise zusammengesetzter) Spannungspfade wird die Leistungsfähigkeit des erweiterten Bounding Surface Modells demonstriert. Abschließend werden Schlussfolgerungen gezogen und potenzielle Perspektiven aufgezeigt.:1 Introduction 1.1 General aspects on constitutive modelling 1.2 Motivation and outline of the thesis 1.3 Basic assumptions and terminology 2 Literature review 2.1 From elastoplasticity to bounding surface plasticity 2.1.1 Bounding surface model according to Manzari and Dafalias (1997) 2.2 Further development of the original model 2.2.1 Papadimitriou and Bouckovalas (2002) 2.2.2 Taiebat and Dafalias (2008) 2.3 Small strain stiffness 2.3.1 Observations 2.3.2 Micromechanical considerations 2.3.3 Very small strain shear modulus G0 2.3.4 Constitutive modelling approaches 2.4 Dilatancy 3 The extended bounding surface model 3.1 Fundamental capabilities of the bounding surface concept 3.1.1 Elastic region 3.1.2 Critical state 3.1.3 Shear strength 3.1.4 Shear stiffness (monotonic) 3.1.5 Contractancy and dilatancy 3.1.6 Barotropy and pycnotropy 3.1.7 Compressive stiffness 3.1.8 Shear stiffness in reversed loading 3.1.9 Additional features 3.2 New features of the extended bounding surface model 3.2.1 Minor modifications 3.2.2 Dilatancy formulation 3.2.3 Cap yield surface 3.2.4 Small strain stiffness mechanism 3.2.5 Cyclic loading mechanism 3.2.6 Summary 3.3 Limitations of the bounding surface model 3.3.1 Intrinsic insuffciencies of the bounding surface concept 3.3.2 Remaining shortcomings of the advanced model version 3.3.3 Newly introduced deficiencies 4 The numerical model and its calibration procedure 4.1 Octave implementation of an element test programme 4.2 Calibration procedure 4.2.1 Sands for calibration 4.2.2 Calibration of basic parameters 4.2.3 Calibration of extended model parameters 4.3 User friendly calibration routine 4.3.1 Conceptual background 4.3.2 Optimisation algorithm 5 Performance of the extended bounding surface model 5.1 Model performance in element tests 5.1.1 Monotonic drained triaxial compression test 5.1.2 Monotonic undrained triaxial compression test 5.1.3 Monotonic eta-constant tests 5.2 Model performance in non-standard triaxial testing 5.2.1 Concept of response envelopes 5.2.2 Simulation of response envelopes 5.3 Model performance on general stress paths 5.3.1 Triaxial compression at small strains 5.3.2 Cyclic triaxial loading 6 Conclusions and perspectives 6.1 Conclusions 6.2 Future perspectives Bibliography Appendices A Mathematical background A.1 Fundamental equations of elastoplasticity A.2 Compilation of major constitutive equations (multiaxial formulation) A.3 Elastoplastic stiffness matrix for singular yield surfaces A.4 Coefficient matrices S and E for loading constraints A.5 Derivation of Mcap and Hcap A.6 Intergranular strain adjustment A.7 Intergranular strain correlation B Details on particle swarm optimisation C Compilation of simulation results C.1 Monotonic triaxial loading C.1.1 Toyoura sand C.1.2 Sacramento River sand C.1.3 Hostun sand C.2 Monotonic eta-constant loading C.2.1 Sacramento River sand C.2.2 Hostun sand C.3 Cyclic triaxial loading
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