Dissertations / Theses on the topic 'Stress modelling'
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Jenter, Harry Leonard. "Modelling bottom stress in depth-averaged flows." Thesis, Massachusetts Institute of Technology, 1989. http://hdl.handle.net/1721.1/58501.
Full textIncludes bibliographical references (leaves 140-145).
The relationship between depth-averaged velocity and bottom stress for wind-driven flow in unstratified coastal waters is examined here. The adequacy of traditional linear and quadratic drag laws is addressed by comparison with a 2 1/2-D model. A 2 1/2-D model is one in which a simplified 1-D depth-resolving model (DRM) is used to provide an estimate of the relationship between the flow and bottom stress at each grid point of a depth-averaged model (DAM). Bottom stress information is passed from the DRM to the DAM in the form of drag tensor with two components: one which scales the flow and one which rotates it. This eliminates the problem of traditional drag laws requiring the flow and bottom stress to be collinear. In addition, the drag tensor field is updated periodically so that the relationship between the velocity and bottom stress can be time-dependent. However, simplifications in the 2 1/2-D model that render it computationally efficient also impose restrictions on the time-scale of resolvable processes. Basically, they must be much longer than the vertical diffusion time scale. Four progressively more complicated scenarios are investigated. The important factors governing the importance of bottom friction in each are found to be 1) non-dimensional surface Ekman depth ... is the surface shear velocity, f is the Coriolis parameter and h is the water depth 2) the non-dimensional bottom roughness, zo/h where zo is the roughness length and 3) the angle between the wind stress and the shoreline. Each has significant influence on the drag law. The drag tensor magnitude, r, and the drag tensor angle, 0 are functions of all three, while a drag tensor which scales with the square of the depth-averaged velocity has a magnitude, Cd, that only depends on zo/h. The choice of drag law is found to significantly affect the response of a domain. Spin up times and phase relationships vary between models. In general, the 2 1/2-D model responds more quickly than either a constant r or constant Cd model. Steady-state responses are also affected. The two most significant results are that failure to account for 0 in the drag law sometimes leads to substantial errors in estimating the sea surface height and to extremely poor resolution of cross-shore bottom stress. The latter implies that cross-shore near-bottom transport is essentially neglected by traditional DAMs.
by Harry Leonard Jenter, II.
Ph.D.
Thomson, Stuart. "Mathematical modelling of elastoplasticity at high stress." Thesis, University of Oxford, 2017. http://ora.ox.ac.uk/objects/uuid:a7d565c6-abeb-4932-8c1e-aebc38da7584.
Full textSolowski, Wojciech Tomasz. "Unsaturated soils : constitutive modelling and explicit stress integration." Thesis, Durham University, 2008. http://etheses.dur.ac.uk/2083/.
Full textHaque, Mainul. "Mathematical modelling of eukaryotic stress-response gene networks." Thesis, University of Nottingham, 2012. http://eprints.nottingham.ac.uk/12509/.
Full textHicks, Michael A. "Numerically modelling the stress-strain behaviour of soils." Thesis, University of Manchester, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.256573.
Full textRadmaneshfar, Elahe. "Mathematical modelling of the cell cycle stress response." Thesis, University of Aberdeen, 2012. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=192232.
Full textKarschau, Jens. "Mathematical modelling of chromosome replication and replicative stress." Thesis, University of Aberdeen, 2013. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=202763.
Full textLykostratis, K. "Mathematical modelling of shear stress signalling in endothelial cells." Thesis, University College London (University of London), 2007. http://discovery.ucl.ac.uk/1445634/.
Full textLamb, Angharad. "Mathematical Modelling of the Biological Stress Response to Chronium." Thesis, University of Nottingham, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.517846.
Full textRoth, Hugh. "Fundamental modelling of single crystal nickel superalloy yield stress." Thesis, University of Cambridge, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.627177.
Full textStefanatos, Rhoda Katerina Anne. "Modelling tumourigenesis and the stress response in Drosophila melanogaster." Thesis, University of Glasgow, 2013. http://theses.gla.ac.uk/4865/.
Full textWelzel, Udo Siegfried. "Diffraction analysis of residual stress modelling elastic grain interaction /." Stuttgart : Univ, 2002. http://www.bsz-bw.de/cgi-bin/xvms.cgi?SWB10221702.
Full textAldakheel, Yousef Yacoub. "Remote sensing of crop water stress : measurements and modelling." Thesis, University of Salford, 1998. http://usir.salford.ac.uk/43021/.
Full textSalvati, Enrico. "Residual stress evaluation and modelling at the micron scale." Thesis, University of Oxford, 2017. https://ora.ox.ac.uk/objects/uuid:b737925e-a200-4a61-87f1-0d834d642d7b.
Full textShuttle, Dawn Alison. "Numerical modelling of localisation in soils." Thesis, University of Manchester, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.277841.
Full textNilsson, Cecilia. "Modelling of Dynamically Loaded Shotcrete." Thesis, KTH, Betongbyggnad, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-36923.
Full textDzomeku, Israel K. "Modelling seed dormancy, germination and emergence of Striga hermonthica." Thesis, University of Reading, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.252261.
Full textBayliss, Martin. "The numerical modelling of elastomers." Thesis, Cranfield University, 2003. http://hdl.handle.net/1826/87.
Full textAlkathafi, Maftah Hussien Abdulgader. "Modelling of carbonate-bicarbonate stress corrosion cracking of pipeline steels." Thesis, University of Manchester, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.498675.
Full textRichardson, G. A. "Algebraic stress modelling for shock-wave/turbulent boundary-layer interactions." Thesis, Cranfield University, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.267213.
Full textKan, Chui-Chui Flora. "Modelling the behaviour of a process control operator under stress." Thesis, City University London, 1992. http://openaccess.city.ac.uk/14854/.
Full textIsiaka, Fatima. "Modelling stress levels based on physiological responses to web contents." Thesis, Sheffield Hallam University, 2017. http://shura.shu.ac.uk/16551/.
Full textLi, Xiangqian. "Modelling stress and damage interaction in fibre reinforced composite laminates." Thesis, University of Bristol, 2009. http://hdl.handle.net/1983/ac610f80-ded7-4d51-b390-5c6548e5c3cd.
Full textFriedrich, Anett, Astrid Ziemann, and Uwe Schlink. "Measurement and modelling of the cumulated thermal stress in Leipzig." Universität Leipzig, 2010. https://ul.qucosa.de/id/qucosa%3A16364.
Full textAbolghasemi, Sobhan. "Materials selection, stress analysis and CFD modelling of flare tips." Thesis, Imperial College London, 2012. http://hdl.handle.net/10044/1/9540.
Full textNogueira, Antonio Jose Arsenia. "Modelling the physiological performance of Daphnia (Crustacea: Cladocera) under stress." Thesis, University of Stirling, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.320355.
Full textLim, Yee Mei. "Detecting and modelling stress levels in e-learning environment users." Thesis, De Montfort University, 2017. http://hdl.handle.net/2086/14210.
Full textBeesley, Ross. "Crack growth modelling from stress concentrations under cyclic loading histories." Thesis, University of Strathclyde, 2017. http://digitool.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=28446.
Full textLobosco, Vinicius. "On the Modelling of Mechanical Dewatering in Papermaking." Doctoral thesis, KTH, Fibre and Polymer Technology, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3702.
Full textMost of the water fed into a paper machine is removedmechanically in the forming and press sections. One of thefactor which has an important influence on mechanicaldewatering, i.e. in both forming and pressing, is thestress-strain behaviour of the fibre network.
The focus of this thesis is on the development of improvedmathematical descriptions of the stress-strain behaviourexhibited by fibre networks in the forming and press sections.The first part of the thesis presents a physically based modelof the forming and densification of fibre mats in twin-wireformers. The model can calculate the ecect of the applicationof a varied load through the forming section. It was developedfrom mass and momentum balances of the fibre and liquid phases,the fibre mat stress-porosity relation and an expression forthe permeability as a function of the porosity. The fibre-matstress-porosity relation used is rate-independent and presentshysteresis. Simulations have been conducted to study theeffects of roll pressure, blade pulses, wire tension andbeating. The effect of sequential blade pressure pulses afterthe forming roll on the dewatering and the concentrationgradients could be characterised. The simulations alsoexhibited rewetting by expansion when the fibre mats left theforming roll. Increasing wire tension resulted in increaseddewatering, but the rate of increase diminished rapidly withincreasing tension. The simulation results also indicated thatbeating has a large influence on dewatering.
The second part of the thesis presents two models of therate-dependent stress-strain behaviour of the fibre networkthat is observed in wet pressing. The first model was based onthe approach pioneered by Perzyna (1966) for strain-ratedependent plasticity and was quite satisfactory for calculatingthe stress-strain behaviour of the fibre network in singlepress nips. It was successfully applied for studyingdensification and dewatering in both normal wet pressing andhigh temperature wet pressing. However, the first model onlyincludes rate dependence in the compression phase of thecompressionexpansion cycle; the expansion phase is treated asbeing rate independent
The second model of the stress-strain behaviour of the fibrenetwork treats both compression and expansion as being ratedependent, according to experimental observations. It is basedon the idea that the wet fibre web may be conceived as alayered network of restricted swelling gels. A swollen fibre isa restricted gel, the inner swelling pressure in a swollenfibre wall being balanced by the stresses in the fibre wallstructure. The observed rate dependence of wet webs in bothcompression and expansion phases was attributed to the flow ofwater out of and into the fibre walls. The second model gavepredictions that are in good agreement with results fromuniaxial experiments using pressure pulses of arbitrary shapefor both a single pulse and a sequence of pulses. It maytherefore be used as a general model for the rheologicalbehaviour of the wet fibre network in wet pressing, providedthe model parameters are estimated from experimental data withsmall experimental error.
KEYWORDS:Paper, modelling, dewatering, forming, wetpressing, fibre network stress, rheology, hysteresis,intra-fibre water, compressibility, structural stress,stress-strain, restricted gels, swelling.
Ventura, Antunes Fernando Jorge. "Influence of frequency, stress ratio and stress state on fatigue crack growth in nickel base superalloys at elevated temperature." Thesis, University of Portsmouth, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.285929.
Full textMok, K. K. K. "The physical and numerical modelling of anisotropic and discontinuous rock masses." Thesis, University of the West of Scotland, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.372554.
Full textHoward, Richard John Anderson. "Direct numerical simulation and modelling of turbulent channel flows subjected to complex distortions." Thesis, Queen Mary, University of London, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.313782.
Full textAgwubilo, Ikenna. "Manufacture, modelling and characterisation of novel composite tubes." Thesis, University of Manchester, 2016. https://www.research.manchester.ac.uk/portal/en/theses/manufacture-modelling-and-characterisation-of-novel-composite-tubes(c11f005b-e651-481f-8ef5-4e6784bfbaa7).html.
Full textMishra, Sanjay Kumar. "Evaluation of finite element modelling techniques and healing hypotheses for a tibial fracture." Thesis, University of Oxford, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.302131.
Full textFjeldstad, Arne. "Modelling of Fatigue Crack Growth at Notches and Other Stress Raisers." Doctoral thesis, Norwegian University of Science and Technology, Department of Engineering Design and Materials, 2007. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-1811.
Full textThis thesis consists of an introduction and eight papers [1–8]. Paper 1 presents simple and flexible methods to enhance the fatigue life of welded aluminium components. The key element of the methods is to change residual stresses from tension to compression at locations vulnerable to fatigue crack growth. This is accomplished by mechanical pre-stressing using elastic pre-deformation or thermal pre-stressing using induction heating. Based on fatigue test results induction heating tuned out to be the most promising method.
In Paper 2, an approximate method based on asymptotic solutions for estimating the stress intensity factor for cracks at stress concentrations is presented. The proposed solution makes use of the near-notch and remote-notch solution to interpolate over the entire range from shallow to deep cracks. Paper 3 extends the theory presented in Paper 2 to cover through-cracked plates of finite width subjected to bending or tension. Paper 4 examines how a decreasing stress field influences the fatigue crack growth. Even though the stress generally decreases from a maximum at some critical point, fatigue crack growth analyses are often performed assuming a homogeneous stress state to avoid the difficulties related to crack growth analyses in complex components. The degree of conservatism has been determined by comparing the calculated fatigue life of cracks growing in a homogeneous stress field with the fatigue life of cracks growing in a gradient stress field. In Paper 5, an approximate method based on asymptotic solutions for estimating the stress intensity factor for cracked V-notched plates is presented. The proposed solutions make use of a reference solution to interpolate from shallow to deep cracks. The reference solution is obtained by considering the current crack emanating from the associated specimen with a sharp notch. It is showed how the proposed theory can be used for estimating the stress intensity factor for a crack located at the root of a weld toe in a T-joint.
Paper 6 and 7 presents the probabilistic fatigue assessment tool, P•FAT, for the fatigue analysis of arbitrary components. General concepts which have to be considered for the accomplishment of a 3D fatigue crack simulation by postprocessing results from a standard finite element analysis are introduced. General features such as determination of the life controlling defect, fatigue strength and fatigue life distribution, and probability of component failure, have been presented. Furthermore, a new short crack growth model that accounts for short crack growth is presented. In Paper 8, the short crack growth model is used to predict the arrest of cracks growing in stress gradient fields. The predictions have been compared with experimentally obtained data for notched specimens and found to agree well.
Paper I and II reprinted with kind permission of Elsevier, sciencedirect.com
Olden, Vigdis. "FE modelling of hydrogeninduced stress crackingin 25% Cr duplex stainless steel." Doctoral thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for produktutvikling og materialer, 2008. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-5026.
Full textGonzalez, David. "A contribution on modelling deformation and residual stress in 3D polycrystals." Thesis, University of Manchester, 2013. https://www.research.manchester.ac.uk/portal/en/theses/a-contribution-on-modelling-deformation-and-residual-stress-in-3d-polycrystals(dad0c6be-0494-46e6-8dc8-d3a968212401).html.
Full textOllander, Simon. "Wearable Sensor Data Fusion for Human Stress Estimation." Thesis, Linköpings universitet, Reglerteknik, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-122348.
Full textI syfte att klassificera och modellera stress har olika sensorer, signalegenskaper, maskininlärningsmetoder och stressexperiment jämförts. Två databaser har studerats: MIT:s förarstressdatabas och en ny databas baserad på egna experiment, där stressuppgifter har genomförts av nio försökspersoner: Trier Social Stress Test, Socially Evaluated Cold Pressor Test och d2-testet, av vilka det sistnämnda inte normalt används för att generera stress. Support vector machine-, naive Bayes-, k-nearest neighbour- och probabilistic neural network-algoritmer har jämförts, av vilka support vector machine har uppnått den högsta prestandan i allmänhet (99.5 ± 0.6 % på förardatabasen, 91.4 ± 2.4 % på experimenten). För båda databaserna har signalegenskaper såsom medelvärdet av hjärtrytmen och hudens ledningsförmåga, tillsammans med medelvärdet av beloppet av hudens ledningsförmågas derivata identifierats som relevanta. En ny signalegenskap har också introducerats, med hög prestanda i stressklassificering på förarstressdatabasen. En kontinuerlig modell har också utvecklats, baserad på den upplevda stressnivån angiven av försökspersonerna under experimenten, där support vector regression har uppnått bättre resultat än linjär regression och variational Bayesian regression.
Moisio, K. (Kari). "Numerical lithospheric modelling: rheology, stress and deformation in the central Fennoscandian Shield." Doctoral thesis, University of Oulu, 2005. http://urn.fi/urn:isbn:9514279514.
Full textSpira, Daniel. "Near-wall Reynolds stress modelling in rotating channel flows using elliptic relaxation." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape11/PQDD_0004/MQ44042.pdf.
Full textSpira, Daniel. "Near-wall Reynolds stress modelling in rotating channel flows using elliptic relaxation." Thesis, McGill University, 1997. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=20521.
Full textThere are two challenges in using this method: (1) the determination of appropriate boundary conditions for the elliptic relaxation equations, and (2) the numerical implementation of those boundary conditions in non-Cartesian geometries. In this thesis, a set of 2D boundary conditions are derived via an asymptotic analysis of the Reynolds stress transport equations through the viscous sublayer. 1D and 2D finite volume numerical models to solve two elliptic relaxation models, the k-epsilon- vv model and a Reynolds stress version, are developed. These formulations are then used to compute the steady flow through stationary and rotating plane channels, and through a plane diffuser. The results are compared with benchmark direct numerical simulation and experimental data.
Cacace, Mauro [Verfasser]. "Stress and Strain modelling of the Central European Basin System / Mauro Cacace." Berlin : Freie Universität Berlin, 2008. http://d-nb.info/1023169886/34.
Full textDrews, Michael C. "Modelling stress-dependent effective porosity-permeability relationships of metre-scale heterogeneous mudstones." Thesis, University of Newcastle Upon Tyne, 2012. http://hdl.handle.net/10443/1672.
Full textParikh, Tejas. "Determination and modelling of residual stress and strain in Nb3Sn superconducting wires." Thesis, Oxford Brookes University, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.506092.
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 textParsa, Arash. "Finite element modelling of stress concentrations in a reinforced concrete offshore structure." Thesis, University of Southampton, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.292406.
Full textScanlon, Thomas Joseph. "Work and non-work stress among solicitors : modelling the work-home interface." Thesis, University of Central Lancashire, 2005. http://clok.uclan.ac.uk/22005/.
Full textBanks, James R. "Numerical modelling of lateral stress on integral abutments due to cyclic loading." Thesis, University of Southampton, 2009. https://eprints.soton.ac.uk/210943/.
Full textSu, Yang. "Modelling study of stress displacement theories for retaining walls under seismic excitation." Thesis, Curtin University, 2014. http://hdl.handle.net/20.500.11937/2253.
Full textMineault-Guitard, Alexandre. "Validation of Observed Bedload Transport Pathways Using Morphodynamic Modelling." Thesis, Université d'Ottawa / University of Ottawa, 2016. http://hdl.handle.net/10393/34587.
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