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Ingul, Charlotte Björk. "Quantification of regional myocardial function by strain rate and strain for evaluation of coronary artery disease : Automated versus manual analysis during acute myocardial infarction and dobutamine stress echocardiography." Doctoral thesis, Norwegian University of Science and Technology, Faculty of Medicine, 2006. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-777.
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Kvantifisering av hjertets muskelfunksjon med tøyning og tøyningshastighet målt med ultralyd for vurdering av koronar sykdom.
Automatisert metode versus manuell ved akutt hjerteinfarkt og ultralyd stress test.
Vanligvis måles hjertets muskelfunksjon med ultralyd, en mye brukt metode for å diagnostisere hjertesykdommer. Vurderingen av muskelfunksjonen baserer seg i dag på en subjektiv visuell gradering av bevegelsen av hjertemuskelen, og dette krever erfaring. En ny automatisert diagnostisk ultralydsmetode basert på måling av hastigheten i hjertemuskelen gir et kvantitativt mål på muskelens tøyning og sammentrekning. Den nye metoden gir ny og mer detaljert informasjon om hjertets funksjon og om pasientens prognose enn vanlig ultralydsvurdering.
Den nye metoden er mer presis ved oppfølgning etter hjerteinfarkt. Et hjerteinfarkt gir nedsatt bevegelse av muskelen og måles med den nye metoden som nedsatt hastighet som muskelen forkortes med. Små forandringer i den skadde hjertemuskelen, ikke alltid synlige for øyet, kan mer nøyaktig følges over tid med den nye metoden. Utbredelsen av hjerteinfarktet kan også vurderes mer nøyaktig.
Det samme gjelder når angina vurderes under belastning. Når en pasient ikke kan sykle eller gå på tredemølle brukes en medisinsk belastningstest. Ved å belaste hjertet med et medikament som øker hjertemuskelens arbeid samtidig med en ultralydundersøkelse, kan vi oppdage redusert blodforsyningsreserve i hjertet. Stresstesten hjelper til med å vurdere om en trang blodåre bør åpnes etter et hjerteinfarkt, og til å vurdere pasienters risiko for hjertekomplikasjoner før en større operasjon. Den nye metoden gir i tillegg mer informasjon om den langsiktige prognosen sammenlignet med den gamle metoden. Vi har funnet at den nye ultralydsmetoden er mer presis (gir større diagnostisk treffsikkerhet i diagnostikk av koronarsykdom) sammenlignet med den gamle.
Måling av sammentrekningshastigheter i hjertemuskelen ble utviklet og testet på Institutt for sirkulasjon og bildediagnostikk ved NTNU av Andreas Heimdal og Asbjørn Støylen i 1998. Metoden trengte teknisk videreutvikling og testing i et større pasientmateriale. Metoden har ikke fått stor utbredelse på sykehusene pga støyfylte kurver og tidskrevende analyser, men med denne automatiserte metoden blir brukervennligheten større som muliggjør klinisk bruk.
Paper I and II preprinted with kind permission of Elsevier, sciencedirect.com
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Maša, Marek. "Deformačně-napěťová analýza aterosklerotické tepny." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2008. http://www.nusl.cz/ntk/nusl-228122.
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The main goal of this diploma thesis was the stress-strain analysis of iliac artery with atheroma.This problem was solved using finite element method (FEM).For the calculation purposes three two-dimensional models were created. The geometry was gained from transversal sections through the iliac artery with ateroma. This geometry is educed from used literature review. The main calculation process was run by ANSYS 11.0 program system.
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Walimbe, Vivek S. "Interactive, quantitative 3D stress echocardiography and myocardial perfusion spect for improved diagnosis of coronary artery disease." Columbus, Ohio : Ohio State University, 2006. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1154710169.
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Janík, Rostislav. "Deformačně-napěťová analýza tepny s ateromem." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2021. http://www.nusl.cz/ntk/nusl-443748.
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This master thesis analyses stress and strain of iliac artery with atheroma. Model of artery is created as 2D and symmetric about the y-axis. The first part of the thesis deals with a research, which includes obtaining information from medicine, which is necessary fort the right solution of the task. Next part dedicates to nonlinear mechanics, constitutive modeling from the view of biomechanice and computational modeling of arteries. In the next part is made analysis for load on artery by physiological and also by high blood pressure. In the end were specified uncertainties of the used model and evaluated chance of atherosclerotic plaque rupture.
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Kida, Naoki. "Finite element formulation and analysis for an arterial wall with residual and active stresses." Kyoto University, 2014. http://hdl.handle.net/2433/189352.
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Nagy, Ellerie. "The Effect of Calcified Plaque on Stress within a Fibrous Thin Cap Atheroma in an Atherosclerotic Coronary Artery Using Finite Element Analysis (FEA)." DigitalCommons@CalPoly, 2010. https://digitalcommons.calpoly.edu/theses/385.
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Atherosclerosis causes hundreds of thousands of deaths in the US alone every year. Fibrous cap rupture is one of the leading causes of these fatalities. Thin cap atheromas are commonly regarded as vulnerable plaque, however the effect of calcium upon a thin fibrous cap with lipid pool is poorly understood. Some studies have shown that calcium adds to stability of the lesion, while others have proven otherwise. An article by Li et al. 2007 suggests location is the key factor. By varying the percentage of calcium and lipid within a defined region, the stress on the cap was estimated using an idealized finite element arterial model. Also the thickness of the fibrous cap was varied to determine whether the stress was solely a function of lipid percentage or a combination. Plaque, arterial wall, lipid, and calcium were modeled using linear elastic, isotropic, and incompressible material properties. The first test varied the thin cap thickness from 65 to 500 microns and tested the calcified lipid model at varying lipid/calcium percentages. The lipid/Calcium pool increased/decreased 10% each test. As the cap thickness becomes thinner than 100 microns, the stress level increases rapidly. The second test compared a model with lipid pool and calcium behind the lipid with a thin cap of 65 microns to a model with lipid pool of the same size and thin cap of 65 microns but only fibrous tissue surrounding (no calcium). The lipid pool increased from 10 to 90% lipid. The result of this test found that at higher lipid percentages, the calcium increased the stress on the cap. By understanding the material properties of plaque and the structure of the lesion, future developments may be able to evaluate rupture risk. This idealized study illustrates the ability of computation models to provide insight into clinical situations.
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Polzer, Stanislav. "Stress-Strain Analysis of Aortic Aneurysms." Doctoral thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2012. http://www.nusl.cz/ntk/nusl-234135.
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Tato práce se zabývá problematikou aneurysmat břišní aorty a možností využít konečnoprvkovou deformačně-napěťovou analýzu těchto aneurysmat ke stanovení rizika ruptury. První část práce je věnována úvodu do problematiky, popisu kardiovaskulární soustavy člověka s důrazem na abdominální aortu, anatomii, fyziologii a patologii stěny tepny s důrazem na procesy vedoucí ke vzniku aneurysmatu. Dále se práce věnuje rizikovým faktorům přispívajících ke vzniku aneurysmat spolu s analýzou současných klinických postupů ke stanovení rizika ruptury spolu se srovnáním navrhovaného kritéria maximálního napětí. Dominantní část této disertace je věnována identifikaci faktorů ovlivňujících napjatost a deformaci stěny aneurysmatu spolu s návrhem nových postupů, prezentací vlastních poznatků vedoucích ke zpřesnění určení rizika ruptury pomocí deformačně- napěťové analýzy a metody konečných prvků. Nejprve je analyzován vliv geometrie, vedoucí k závěru, že je nezbytné používání individuálních geometrií pacienta. Dále je pozornost zaměřena na odbočující tepny, které ve stěně působí jako koncentrátor napětí a mohou tedy ovlivňovat napjatost v ní. Jako další podstatný faktor byl identifikován vliv nezatížené geometrie a bylo napsáno makro pro její nalezení, které bylo opět zahrnuto jako standardní součást do výpočtového modelu. Mechanické vlastnosti jak stěny aneurysmatu, tak intraluminálního trombu jsou experimentálně testovány pomocí dvouosých zkoušek. Také je zde analyzován vliv modelu materiálu, kde je ukázáno, že srovnávání maximálních napětí u jednotlivých modelů materiálu není vhodné díky zcela rozdílným gradientům napětí ve stěně aneurysmatu. Dále je zdůrazněna potřeba znalosti distribuce kolagenních vláken ve stěně a navržen program k jejímu získání. Intraluminální trombus je analyzován ve dvou souvislostech. Jednak je ukázán vliv jeho ruptury na napětí ve stěně a jednak je analyzován vliv jeho poroelastické struktury na totéž. Posledním identifikovaným podstatným faktorem je zbytková napjatost ve stěně. Její významnost je demonstrována na několika aneurysmatech a i tato je zahrnuta jako integrální součást do našeho výpočtového modelu.Na závěr jsou pak navrženy další možné směry výzkumu.
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Howell, Geoffrey Peter. "Identification of plastic strain using thermoelastic stress analysis." Thesis, University of Southampton, 2017. https://eprints.soton.ac.uk/412636/.
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Identification of regions containing plastic strain arising from the welding process is performed through the application of thermoelastic stress analysis (TSA) and finite element (FE) modelling. An approach is developed that removes the requirement to have a physical reference specimen for the component studied by developing a 'synthetic reference bitmap' using finite element analysis. The regions containing plastic strain can be identified with TSA by collecting data from a 'reference' plastic strain free specimen from the TSA data and creating a resultant bitmap. Here, a synthetic bitmap is developed that mimics the thermoelastic response of a physical reference specimen. The approach is validated against physical reference specimens of different geometries and materials (AL2024 and 316L stainless steel) and is shown to accurately model the thermoelastic response. The newly developed synthetic bit map approach is applied to specimens containing welds and it is shown that the regions that contain plastic strain in the heat affected zone (HAZ) of a double bead welded 316L stainless steel specimen can be revealed. The predicted changes in thermoelastic response are compared to plastic strain predictions generated by thermomechanical modelling of the welded specimen and the distribution of plastic strain found by the TSA matches that given by the model. The relationship between the change in thermoelastic response and plastic strain has been investigated and the results suggest there is a change in the thermoelastic response as a result of plastic straining. However, uncertainties in the data resulting from detector noise and other errors mean that further development of the experiments and the equipment is required to provide a conclusive and quantitative relationship. It has also been demonstrated that TSA can be used outside of the laboratory in onsite trials in two coal fired power stations. Thermoelastic data was successfully recorded from pipe welds in-situ. To achieve this a new means of loading the pipes was devised based on vibration excitation, and the difficulties of performing surface measurements on heavily corroded pipes were overcome. The results from the onsite tests show that TSA can be used as an in-situ assessment technique and that is no longer restricted to being a laboratory based technique.
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Hemmat, Abbas. "Stress/strain analysis and internal bruising in potato tubers." Thesis, Cranfield University, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.357842.
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Kang, Wei-Ping. "Application of numerical analysis to neutron strain scanning." Thesis, University of Salford, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.360449.
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TAVARES, CARLOS ALBERTO VIANNA. "STRESS AND STRAIN ANALYSIS OF COMPOSITE SHELLS WITH GENERAL GEOMETRIES." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 1991. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=19394@1.
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PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIROCOORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIOR
Este trabalho apresenta a modelagem teórica e correspondente solução numérica, associada ao problema de tensões e deformações em cascas compostas de geometrias arbitrárias, submetidas a carregamento térmico e/ou de pressão. A casca composta é constituída de uma camada viscoelástica reforçada por outras duas elásticas. Apresentam-se as hipóteses adotadas na caracterização térmica e mecânica do material, bem como procedimentos e resultados obtidos na aplicação destas suposições. Problemas envolvendo geometrias cilíndricas e cônicas são resolvidas com o objetivo de exemplificar a teoria desenvolvida.
The present work sets forth the expressions for the stresses and strains in a sandwich shell of arbitrary shape under thermal and pressure loads. The composite shell is made of two elastic face lawers with a viscoelastic core. The elastic facings are isotropic of the same material and obey the kirchhoff hypotesis. The viscoelastic core is assumed to be thermorheologically simple as a way to facilitate the mathematical representation of the creep modulus on temperature. In order to simplify the derivations of the needed equations it is assumed that the stresses in the core acting in the tangencial directions are much smaller than those developed in the facing, so that theycan be neglected. The general equations for the stresses and strains are written using curvilinear shell coordinates and some results are then shown for cylindrical and conical shell geometries.
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Ryšavý, Pavel. "Deformačně-napěťová analýza aneurysmatu břišní aorty." Doctoral thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2011. http://www.nusl.cz/ntk/nusl-233960.
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This thesis deals with problems of biomechanics of soft tissues, namely of stress-strain analysis of abdominal aortic aneurysm (AAA). The introduction describes briefly the possibility of aneurysm occurrence with a focus on an aneurysm in the abdominal aorta.
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Holmqvist, Marcus, and Marcus Gunnteg. "Seepage, Solute transport and Strain-stress Analysis of Ashele Tailings Dams." Thesis, Uppsala universitet, Elektricitetslära, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-237732.
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This master thesis has been conducted through cooperation between Elforsk, Uppsala University and Tsinghua University in Beijing. Ashele Tailings Dam, located in Haba Town, Xianjing Province, China, is designed and used for high sulphur tailings. Because of a new mineral separation technique, the dam is now also being filled with low sulphur tailings. Since the dam was not originally designed for the new tailings materials, the seepage and stress-strain analyses of the dam need to be re-evaluated and refined. The Ashele Ltd. is also planning on building a new dam to meet its growing need for tailings deposit capacity. This dam will be used for the new low sulphur tailings and a thorough analysis of the dam will have to be performed.The purpose of this thesis is to re-evaluate the analyses of the seepage and stress-strain in the old dam and to perform the same type of analyses on the newdam. Numerical analyses of the seepage, solute transport and strain-stress in the dam are performed, using the physical and mechanical properties of the tailings materials. It is shown, that the construction of the new tailings dam, will have a good effect on the seepage and therefore also solute transport. The results also show that theseepage, solute transport, stress and deformation are depending on the amount ofwater in the tailings pond and that a lower water level has a positive effect on all thestudied variables.
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Shoghi, Kiumars. "Stress and strain analysis of flat and v-section band clamps." Thesis, University of Huddersfield, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.397435.
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Hossain, Tasnia. "GaN based structures on patterned silicon substrate : stress and strain analysis." Nice, 2012. http://www.theses.fr/2012NICE4096.
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This work deals with the stress and strain analysis of GaN grown on patterned Si substrate in order to avoid crack generation and to obtain the suitable size of the pattern for device (LED, LD, transistor etc. ) applications. Using patterned substrate we have grown thick crack free continuous GaN layers by MBE and by MOCVD. In this work, we have used different sizes of patterns, different trench widths, trench heights, different shapes and in-plane orientations of the patterns and two crystal orientations of Si substrate. We have found that beyond a critical film thickness, the number of cracked mesa increases with the increase in mesa size for a particular shape of mesa. In the case of square and lozenge shape mesas of 200 μm length, 96 and 88% mesas respectively are found crack free for 12 μm thick GaN film. To analyze the stress and strain, micro-Raman spectroscopy and micro-photoluminescence measurements are carried out on GaN mesa. A U-shape stress distribution is observed on different sizes of mesa where the maximum tensile stress is found at the center of the mesa while towards the free edges or corners of the mesa the stress gradually relaxes. It is also revealed that the in-plane stress increases with the increase in mesa size. In contrast, the in-plane stress decreases with the increase in trench height of Si substrate. However, the trench width shows no significant effect on the in-plane stress. An analytical model has been used to account for the stress distribution in the patterns. This study of thick GaN on patterned Si substrate seems to be promising for the fabrication of optoelectronic and electronic devices which were limited by the planar substrateLe présent travail concerne l’étude des contraintes et des déformations dans le matériau GaN épitaxié par EJM et par EPVOM sur substrat silicium texturé en vue d’éviter la fissuration du matériau et ainsi obtenir des motifs compatibles avec la réalisation de composants (DELs, Lasers, transistors etc. ). Nous avons étudié des motifs différents en tailles, séparations, hauteurs de tranchées, formes, orientations dans le plan ainsi que deux orientations cristallines du substrat silicium. Au-delà d’une épaisseur critique du film déposé, pour une forme de motif donnée, la fraction de motifs fissurés augmente avec la taille des motifs. 88% des motifs en losange et 96% des motifs carrés sont exempts de fissures pour des films GaN épais de 12 μm pour une largeur égale à 200 μm. Une distribution en U de la contrainte en tension est mise en évidence par spectroscopie micro-Raman et par micro-photoluminescence pour les différentes tailles de motifs étudiés, le maximum de contrainte se situant en leur centre et la contrainte se relaxant graduellement vers les bords libres. La contrainte augmente avec la taille des motifs, mais diminue avec la hauteur des tranchées réalisées dans le substrat. Un modèle analytique a été adapté pour rendre compte de la répartition des contraintes. La distance séparant les motifs influe peu. Quoi que la répartition des contraintes puisse être différente durant la croissance, nous avons montré la possibilité d’obtenir des films de GaN avec une bonne qualité cristalline sur ces motifs, ce qui montre que cette voie est prometteuse pour la fabrication de composants optoélectronique et électroniques jusqu’ici limités par la croissance sur substrat planaire
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Jain, Vibhor. "Analysis of structural development during superdrawing of poly(ethylene terephthalate) fibers." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/28185.
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Thesis (M. S.)--Polymer, Textile and Fiber Engineering, Georgia Institute of Technology, 2009.Committee Chair: Wang, Youjiang; Committee Co-Chair: Jacob, K.I.; Committee Member: Aneja, A.P.; Committee Member: Garmestani, Hamid; Committee Member: Thio, Yonathan S.; Committee Member: Yao, Donggang
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Seki, Wataru. "Analysis of strain localization in hyperelastic materials, using assumed stress hybrid elements." Diss., Georgia Institute of Technology, 1994. http://hdl.handle.net/1853/19088.
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Chevallier, Elise Camille. "Assessment of welding induced plastic strain using the thermoelastic stress analysis technique." Thesis, University of Southampton, 2017. https://eprints.soton.ac.uk/420750/.
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The work presented in the thesis is dedicated to the development and validation of a new technique to assess plastic strain based on thermoelastic stress analysis (TSA). Welding induced plasticity (WIP) and welding residual stresses can negatively affect the structural integrity of welded structures as they can exacerbate creep and stress corrosion cracking and limit the structure’s resistance to failure. Moreover, WIP has been shown to negatively affect weld integrity, since the associated accumulation of defects (dislocations) in the material will accelerate the nucleation of macro-scale defects that lead to component failure. There has been considerable amount of work published on determining the magnitude and distribution of the residual stresses both experimentally and by using numerical techniques. WIP can be predicted using finite element analysis (FEA), however, there is currently no standardised experimental method to characterise plastic strain and hence, model predictions are not readily validated with confidence. Recently, two techniques, based on electron backscatter diffraction and indentation respectively, were developed to assess WIP. However, both techniques are destructive and would not be applicable on in-situ components. TSA is a non-contact stress analysis method which is quick to apply and fully portable. TSA is based on the measurement of a small temperature change that occurs as a result of a change in the stress. The small temperature change is measured using an infrared detector. A method for plastic strain assessment (PSA) using TSA has been proposed based on the change in the thermoelastic response due to the plastic strain a material has experienced during a process, e.g. deformation or welding. TSA has the potential to be the first nondestructive, non-contact plastic strain assessment technique, termed as TSA-PSA. The aim of the PhD is to investigate the potential of using the TSA-PSA approach for assessing WIP in austenitic (AISI 316L) and ferritic (SA508 Gr.3 Cl.1) steels. The influence of welding induced microstructural changes on the thermoelastic response is investigated to establish any changes in the thermoelastic response relating to plastic straining only. The study focuses on two typical nuclear grade steels; ferritic SA508 Gr.3 Cl.1 and austenitic stainless steel AISI 316L. The effect of plastic strain on the thermoelastic response of both steels is investigated through the design and assessment of a calibration specimen used to determine the thermoelastic constant variation with plastic strain alongside with microstructural changes. It was found that the plastic strain has a stronger influence on the thermoelastic constant in SA508 than in AISI 316L. For uniform microstructures the influence of plastic strain on the thermoelastic response can be defined and, a larger influence of plastic strain on thermoelastic response was reported for coarse grains of austenite in AISI 316L and coarse grains of ferrite in SA508. The second part of the work concerns development finite element (FE) models of weld mock-ups to demonstrate application of TSA-PSA. The modelling enabled the plastic strain experienced during welding to be predicted and adjustments made to the design prior to the mock-up manufacture. Once satisfied that the mock-ups were suitable for TSA, they were manufactured at TWI Ltd. TSA experimental work was conducted on each mock-up and the outcome was compared with the outputs from the calibrated FE models. The capability of TSA to identify plastic strain in welded components is assessed through the use of the weld mock-ups. The thesis makes a novel contribution to the development of TSA as a portable non-destructive, non-contact technique to assess WIP in components with the investigation of the influence of microstructural changes similar to that found in welds on the technique, as well as the design, manufacture and plastic strain predictions in weldments dedicated to the technique. The results indicate a stronger influence of the plastic strain on the thermoelastic constant in coarse-grained microstructure in both grades of steel.
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Schenk, Jason Robert. "Meta-uncertainty and resilience with applications in intelligence analysis." Columbus, Ohio : Ohio State University, 2007. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1199129269.
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Ye, Wei. "Nano-heteroepitaxy stress and strain analysis: from molecular dynamic simulations to continuum methods." Thesis, Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/34752.
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For decades, epitaxy is used in nanotechnologies and semiconductor fabrications. So far, it's the only affordable method of high quality crystal growth for many semiconductor materials. Heterostructures developed from these make it possible to solve the considerably more general problem of controlling the fundamental parameters inside the semiconductor crystals and devices. Moreover, as one newly arising study and application branch of epitaxy, selective area growth (SAG) is widely used to fabricate materials of different thicknesses and composition on different regions of a single wafer. All of these new and promising fields have caught the interests and attentions of all the researchers around the world.
In this work, we will study the stress and strain analysis of epitaxy in nano-scale materials, in which we seek a methodology to bridge the gap between continuum mechanical models and incorporate surface excess energy effects, which can be obtained by molecular dynamical simulations. We will make a brief description of the elastic behavior of the bulk material, covering the concepts of stress, strain, elastic energy and especially, the elastic constants. After that, we explained in details about the definitions of surface/interface excess energy and their characteristic property tensors. For both elastic constants and surface excess energy, we will use molecular dynamic simulations to calculate them out, which is mainly about curve-fitting the parabola function between the total strain energy density and the strain.
After this, we analyzed the stress and strain state in nanoisland during the selective area growth of epitaxy. When the nanoisland is relaxed, the lattice structure becomes equilibrated, which means the total strain energy of system need to be minimized. Compared to other researcher's work, our model is based on continuum mechanics but also adopts the outcome from MD simulations. By combining these microscopic informations and those macroscopic observable properties, such as bulk elastic constants, we can provide a novel way of analyzing the stress and strain profile in epitaxy. The most important idea behind this approach is that, whenever we can obtain the elastic constants and surface property tensors from MD simulations, we can follow the same methodology to analyse the stress and strain in any epitaxy process. This is the power of combining atomistic simulations and continuum method, which can take considerations of both the microscopic and macroscopic factors.
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Singh, Meera Nand Kaur. "Notch tip stress strain analysis in bodies subjected to non-proportional cyclic loads." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape17/PQDD_0010/NQ30647.pdf.
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Guzelbey, Ibrahim H. "Finite and boundary element analysis of elasto-plastic finite strain contact problems." Thesis, Cranfield University, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.335006.
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Nowak, Stephanie Beth. "Understanding Time-Variant Stress-Strain in Turkey: A Numerical Modeling Approach." Diss., Virginia Tech, 2004. http://hdl.handle.net/10919/26072.
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Over the past century, a series of large (> 6.5) magnitude earthquakes have struck along the North Anatolian Fault Zone (NAFZ) in Turkey in a roughly East to West progression. The progression of this earthquake sequence began in 1939 with the Ms 8.0 earthquake near the town of Erzincan and continued westward, with two of the most recent ruptures occurring near the Sea of Marmara in 1999. The sequential nature of ruptures along this fault zone implies that there is a connection between the location of the previous rupture and that of the future rupture zones. This study focuses on understanding how previous rupture events and tectonic influences affect the stress regime of the NAFZ and how these stress changes affect the probability of future rupture along any unbroken segments of the fault zone using a two dimensional finite element modeling program.
In this study, stress changes due to an earthquake are estimated using the slip history of the event, estimations of rock and fault properties along the fault zone (elastic parameters), and the far-field tectonic influence due to plate motions. Stress changes are not measured directly. The stress regime is then used to calculate the probability of rupture along another segment of the fault zone.
This study found that when improper estimates of rock properties are utilized, the stress changes may be under- or over- estimated by as much as 350% or more. Because these calculated stress changes are used in probability calculations, the estimates of probability can be off by as much as 20%. A two dimensional model was built to reflect the interpreted geophysical and geological variations in elastic parameters and the 1939 through 1999 rupture sequence was modeled. The far-field tectonic influence due to plate motions contributed between 1 and 4 bars of stress to the unbroken segments of the fault zone while earthquake events transferred up to 50 bars of stress to the adjacent portions of the fault zone.
The 1999 rupture events near Izmit and Düzce have increased the probability of rupture during the next ten years along faults in the Marmara Sea to 38% while decreasing the probability of rupture along the faults near the city of Bursa by ~6%. Large amounts of strain accumulation are interpreted along faults in the Marmara Sea, further compounding the case for a large rupture event occurring in that area in the future.Ph. D.
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Kayaoglu, Mustafa Williamson David A. "Terrorism and strain an exploratory analysis of the impact that individual strain and negative affect have on violent behavior among trained Turkish Hezbollah members /." [Denton, Tex.] : University of North Texas, 2008. http://digital.library.unt.edu/permalink/meta-dc-9076.
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BAMIRO, OLUYINKA OLUGBENGA. "ANALYSIS OF THERMAL STRESS AND PLASTIC STRAIN IN STUDS/VIAS OF MULTILEVEL INTEGRATED CIRCUITS." University of Toledo / OhioLINK, 2004. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1099778888.
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Moita, Gray Farias. "Non-linear finite element analysis of continua with emphasis on hyperelasticity." Thesis, Imperial College London, 1994. http://hdl.handle.net/10044/1/7943.
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Crist, Nancy Gilbert. "Women’s Perceptions of Postpartum Stress: A Narrative Analysis." Scholar Commons, 2010. http://scholarcommons.usf.edu/etd/3560.
Full textAbstract:
The impact of stress on the health of postpartum mothers is poorly understood. Although the postpartum period increases risk for stress related diseases such as depression and autoimmune disorders, little qualitative research has focused on women’s perceptions of postpartum stressors.
A constant comparative content analysis using Atlas.Ti was done on data collected by Groer (NIH R01 NR05000“Influence of Lactation on Postpartum Stress & Immunity) from 2001 to 2005. Women (n=127) answered the prompt, “Think of any one incident, thought, or feeling that stands out as very stressful to you and describe in as much detail as you choose.” Researcher triangulation was provided by independent coding of data by two qualitative researchers.
The women were predominantly white (91%), married (72%), and not yet working following the baby’s birth (70%). Only 28% had family incomes greater than $40,000 per year. Vaginal births were experienced by 66%, 83% without complications. Forty-seven percent were breastfeeding exclusively with 43% bottle feeding. Slightly less than half (48%) were first time mothers. Eighty-nine percent claimed no recent major life event, such as a death in the family. Twenty-seven postpartum stressors were identified that were grouped into five themes: 1) environmental stressors, 2) symptoms of depression, 3) infant health and safety issues, 4) maternal role strain, and 5) lack of support. Seventeen women identified fatigue or lack of sleep as stressful and each questioned her ability to parent a newborn.
Though these women would seem low risk for stress (having had an uncomplicated birth, being married and not yet back at work postpartum), 27 different postpartum stressors were identified. Stressors such as lack of sleep may be known by maternal-child nurses, but women are unprepared for them. Interventions need to be designed to provide anticipatory guidance for new mothers regarding postpartum stressors. Tools should be developed for use by clinicians to assess maternal stress in the postpartum period. Prenatal preparation anticipating stressors and postpartum vigilance in assessing stressors could ease the transition into motherhood.
28
Thomková, Barbora. "Vliv orientace a umístění dentálního implantátu na deformačně-napěťové stavy v dolní čelisti." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2020. http://www.nusl.cz/ntk/nusl-418201.
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The master’s thesis deals with issues belonging to the field of dental biomechanics, specifically the mechanical interaction of dental implants with the bone tissue of the mandible. The thesis focuses on the stress-strain analysis of the mandible with the implant inserted in different positions, with a different angle relative to the occlusal plane. The solution is performed by computational modeling using the finite element method. The geometry model of mandible was created based on CT images. The aim of the master’s thesis was also to compare the influence of the choice of the material model of cancellous bone tissue on the resulting stress-strain states of the mandible with the dental implant. Three material models of cancellous bone tissue were created - two homogeneous material model and a heterogeneous material model, which was based on CT image data. The work also investigates the effect of rotation (+5° or -5°) of implants in basic positions on the resulting stress-strain states. The stress-strain analysis showed that position and rotation has a greater effect on the stress and strain of bone tissue and implant than the chosen material model of cancellous bone tissue.
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Mercimek, Umit. "Shock Failure Analysis Of Military Equipments By Using Strain Energy Density." Master's thesis, METU, 2010. http://etd.lib.metu.edu.tr/upload/12612721/index.pdf.
Full textAbstract:
Failure of metallic structures operating under shock loading is a common
occurrence in engineering applications. It is difficult to estimate the response of
complicated systems analytically, due to structure&rsquos dynamic characteristics and varying loadings. Therefore, experimental, numerical or a combination of both methods are used for evaluations. The experimental analysis of the shocks due to firing is done for 12.7mm Gatling gun and 25mm cannon. During the tests, the Gatling gun and the cannon are located on military Stabilized Machine Gun Platform and Stabilized Cannon Platform respectively. For the firing tests, ICP (integrated circuit piezoelectric) accelerometers are attached to obtain the loading history for corresponding points. Shock Response Spectrum (SRS) analysis (nCode Glypworks) is done to define the equivalent shock profiles created on test pieces and the mount of 25mm cannon by means of the gun and the cannon firing. Transient shock analysis of the test pieces and the mount are done by applying the obtained shock profiles on the parts in a finite element model (ANSYS). Furthermore, experimental stress analysis due to shock loading is performed for two different types of material and different thicknesses of the test pieces. The input data for the analysis is obtained through measurements from strain rosette precisely located at the critical location of the test pieces. As a result of the thesis, a proposal is tried to be introduced where strain energy density theory is applied to predict the shock failure at military structures.
30
Yamashita, Tatsuya. "Analysis of anisotropic material." Ohio : Ohio University, 1996. http://www.ohiolink.edu/etd/view.cgi?ohiou1177700236.
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Schenk, Jason Robert. "Meta-uncertainty and resilience with applications in intelligence analysis." The Ohio State University, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=osu1199129269.
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Tse, Man Kit. "Influence of stress states on soil-water characteristics, conjunctive surface-subsurface flow modelling and stability analysis /." View abstract or full-text, 2007. http://library.ust.hk/cgi/db/thesis.pl?CIVL%202007%20TSE.
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Lokuge, W. P. (Weena Priyanganie) 1967. "Stress-strain behaviour of confined high strength concrete under monotonically increasing and cyclic loadings." Monash University, Dept. of Civil Engineering, 2003. http://arrow.monash.edu.au/hdl/1959.1/9425.
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Kayaoglu, Mustafa. "Terrorism and strain: An exploratory analysis of the impact that individual strain and negative affect have on violent behavior among trained Turkish Hezbollah members." Thesis, University of North Texas, 2008. https://digital.library.unt.edu/ark:/67531/metadc9076/.
Full textAbstract:
This study attempts to explore the strains that terror organization members experience prior to the training process in the organization. The primary goal of this research is to understand the relationship between the earlier experienced strains of terrorists and their violent behaviors. In the study a Turkish Hezbollah terror organization sample (N = 144) was utilized in the frame of Agnew's (1992) general strain theory. Initially, quantitative methods, such as bivariate analysis and multivariate analysis, were utilized to identify the cumulative effect of strains on the violent behaviors of terrorists. Later, by utilizing case studies with a qualitative approach the mediating effect of negative emotions (anger, frustration, depression and fear) were identified. This study found that among Turkish Hezbollah members, prior to joining the terrorist organization, individuals who experience higher levels of strain are more likely to perform violent acts when compared to individuals who experience lower levels of strain. This study affirmed earlier studies on strain-crime relationship. Moreover, utilized case studies support that negative emotions -specifically anger- mediate between strains and violent actions. In sum, this research retests and builds on Agnew's theory and argues that general strain theory can help terrorism studies to understand the sources of strains of terrorists and the effect of strains on their violent behavior.
35
Ručinskas, Artūras. "Comparative analysis of stress-strain calculation methods and algorithms for concrete members reinforced with FRP re-bars." Master's thesis, Lithuanian Academic Libraries Network (LABT), 2011. http://vddb.laba.lt/obj/LT-eLABa-0001:E.02~2011~D_20110620_141822-28189.
Full textAbstract:
The final thesis consists of three main parts, each covering a certain aspect of investigation.
First chapter presents an extensive literature review, covering such aspects as: application of
FRP (fiber reinforced polymer) materials in modern-day civil engineering, characteristics of
FRP reinforcement for reinforced concrete structures, advantages and drawbacks of FRP rebars
compared to traditional materials, peculiarities of flexural behavior of FRP reinforced
members, review of existing empirical stress-strain calculation algorithms and building codes
for concrete members reinforced with FRP.
Second part aims at presenting gathered experimental data consisting of 51 FRP reinforced
flexural members under 4 point bending scheme. Taking into account such parameters as
reinforcement ratio, load intensity and elasticity modulus of FRP reinforcement, statistical
analysis on a number of calculation algorithms and building codes is performed in order to
evaluate their credibility and reliability for use in real-world structures.
The final part of the work presents a Simplified Discrete Crack model developed in VGTU
Department of Bridges and Special Structures. The model is applied for a series of collected
beams. The results are compared with theoretical predictions made by different design codes
and experimental values.
The final thesis consists of: 90 pages of text (without appendixes), 46 pictures, 17 tables. 3
appendixes are included. Literature list consisting of 82... [to full text]Baigiamąjį magistro darbą sudaro trys pagrindinės dalys. Pirmajame skyriuje pateikiama literatūros apžvalga, kurioje nagrinėjamos temos susijusios su pluoštinės armatūros panaudojimu lenkiamiems betoniniams elementams. Apžvelgiamos tokių elementų panaudojimo galimybės, privalumai ir trūkumai, deformacijų skaičiavimo metodai bei matematiniai modeliai. Antrajame skyriuje nagrinėjama surinkta polimerine armatūra armuotų sijų eksperimentinių duomenų imtis. Siekiant įvertinti skirtingų skaičiavimo metodų patikimumą ir pritaikomumą ne plienine armatūra armuotiems elementams, atliekama lyginamoji statistinė analizė. Jos metu įvertinama armavimo procento, apkrovimo lygio bei pluoštinės armatūros tamprumo modulio įtaka. Trečiojoje darbo dalyje surinktai eksperimentinių duomenų imčiai pritaikytas VGTU Tiltų ir Specialiųjų Statinių Katedroje sukurtas Diskrečiųjų plyšių modelis. Gautos priklausomybės palygintos su kitų skaičiavimo normų rezultatais bei eksperimentiniais duomenimis. Gauti rezultatai parodė, kad pritaikius tikslesnius praslydimo bei armatūros ir betono sąveikos ruožuose tarp plyšių modelius, diskrečiųjų plyšių modelis gali būti sėkmingai taikomas polimerine armatūra armuotų elementų elgsenai prognozuoti.
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Sutherland, Brandy. "Experimental and analytical analysis of the stress-strain diagram of FRP-confined concrete with different loading rates." Thesis, Manhattan, Kan. : Kansas State University, 2007. http://hdl.handle.net/2097/420.
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Petre, Marc Thomas. "INVESTIGATING THE INTERNAL STRESS/STRAIN STATE OF THE FOOT USING MAGNETIC RESONANCE IMAGING AND FINITE ELEMENT ANALYSIS." Case Western Reserve University School of Graduate Studies / OhioLINK, 2007. http://rave.ohiolink.edu/etdc/view?acc_num=case1181240611.
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Wang, Zhi G. "Simultaneous measurement of strain and temperature using two-mode elliptical core optical fiber." Thesis, Virginia Tech, 1992. http://hdl.handle.net/10919/41527.
Full textAbstract:
A single piece of optical fiber can be utilized to sense both strain and temperature simultaneously. To develop such a sensor, we sandwich a section of two-mode elliptical core (e-core) fiber between two partially reflecting mirrors. This configuration can be considered as an intrinsic Fabry-Perot interferometer, in which the two-mode, e-core fiber serves as the resonant cavity. Two different types of phase modulation can be extracted under perturbations of strain and temperature on the fiber. These phase changes are due to the two-mode interference and intrinsic Fabry-Perot interference, respectively. The relationship between the phase information and the two physical measurands, i.e. strain and temperature, can be established using two coupled equations, in which the strain and temperature are considered as two unknowns. By solving these two coupled equations, we can simultaneously determine the strain and temperature. The waveguide theory and the Cross sensitivity analysis of this sensor are presented. The descriptions of four independent experiments that have been used to determine the coefficients of the two coupled equations are given. The resolutions of the strain and temperature measurements have been obtained to be 31 μm/m and 4.5 °C, respectively.Master of Science
39
Suh, Jong Beom. "STRESS ANALYSIS OF RUBBER BLOCKS UNDER VERTICAL LOADING AND SHEAR LOADING." University of Akron / OhioLINK, 2007. http://rave.ohiolink.edu/etdc/view?acc_num=akron1185822927.
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Giardina, Ronald J. Jr. "On The Ramberg-Osgood Stress-Strain Model And Large Deformations of Cantilever Beams." ScholarWorks@UNO, 2017. http://scholarworks.uno.edu/td/2377.
Full textAbstract:
In this thesis the Ramberg-Osgood nonlinear model for describing the behavior of many different materials is investigated. A brief overview of the model as it is currently used in the literature is undertaken and several misunderstandings and possible pitfalls in its application is pointed out, especially as it pertains to more recent approaches to finding solutions involving the model. There is an investigation of the displacement of a cantilever beam under a combined loading consisting of a distributed load across the entire length of the beam and a point load at its end and new solutions to this problem are provided with a mixture of numerical techniques, which suggest strong mathematical consistency within the model for all theoretical assumptions made. A physical experiment was undertaken and the results prove to be inaccurate when using parameters derived from tensile tests, but when back calculating parameters from the beam test the model has a 14.40% error at its extreme against the experimental data suggesting the necessity for further testing.
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Iwamoto, Sohei. "Analysis of multiple cracking and interfacial debonding of the galvannealed coating layer under applied tensile strain." 京都大学 (Kyoto University), 2009. http://hdl.handle.net/2433/77968.
Full textAbstract:
Kyoto University (京都大学)0048
新制・課程博士
博士(工学)
甲第14575号
工博第3043号
新制||工||1453(附属図書館)
26927
UT51-2009-D287
京都大学大学院工学研究科材料工学専攻
(主査)教授 落合 庄治郎, 教授 粟倉 泰弘, 准教授 奥田 浩司
学位規則第4条第1項該当
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Benz, Joan Clark. "An analysis of the stress, strain and coping levels of public school teachers of seriously emotionally disturbed students." Diss., Virginia Polytechnic Institute and State University, 1987. http://hdl.handle.net/10919/82899.
Full textAbstract:
The purpose of this study was to assess the stress, strain and coping levels of public school teachers of seriously emotionally disturbed students. A secondary purpose was to determine if relationships existed between dependent variables stress, strain and coping and teacher experience and teaching assignment variables. The sample consisted of five hundred teachers of seriously emotionally disturbed students in the southeast region of the United States. The usable return rate was 62% with N = 295.
Respondents completed a demographic information survey which provided data for variables sex, year of birth, highest degree earned, degree area, experience in education, community size and present special education teaching setting. The Occupational Environment Scales, Personal Strain Questionnaire and Personal Resources Questionnaire developed by Samuel Osipow and Arnold Spokane (1981) were used to collect data on stress, strain and coping levels. Frequencies, means, standard deviations, medians and modes were computed for all variables. Pearson correlations and t-tests were calculated for teacher experience variables and stress, strain and coping. Chi-square and ANOVA procedures were completed for teacher assignment variables and the dependent variables.
The major finding of the study was that the majority of public school teachers of the seriously emotionally disturbed had low to average stress and strain levels, and above average coping skills. The sample of teachers of seriously emotionally disturbed students who participated in this study do not appear to be as stressed and strained as samples reviewed in other recent studies. This may be due to the nature of the sample.
Older teachers were found slightly less stressed, less strained and possessing slightly higher coping skill levels than younger teachers. There were no significant relationships found between teaching experience variables and dependent variables of stress, strain and coping.
No significant relationship between stress and teaching assignment variables, community size and teaching setting resulted. A relationship was found between strain levels and community size and teaching setting. There was evidence of a relationship between coping skills and community size (urban, suburban, rural), but no relationship was found between coping skill levels and special education teaching setting (resource, self-contained, center, center with therapy).Ed. D.
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TANAKA, Keisuke, Yoshiaki AKINIWA, Yoshihisa SAKAIDA, and Hirohisa KIMACHI. "Lattice Strain and Domain Switching Induced in Tetragonal PZT by Poling and Mechanical Loading." The Japan Society of Mechanical Engineers, 2000. http://hdl.handle.net/2237/9183.
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Crammond, G. "Development of optical techniques for the experimental analysis of local stress and strain distributions in adhesively bonded composite joints." Thesis, University of Southampton, 2013. https://eprints.soton.ac.uk/355981/.
Full textAbstract:
This research seeks to evaluate the local stress and strain distributions formed in adhesively bonded composite joints under quasi static and high strain rate loading. A literature review of current analytical, numerical and experimental studies of adhesively bonded joints is presented and identifies the lack of knowledge in the behaviour of composite bonded joints in the through-thickness direction. Detailed analysis of the stress and strain in the joint, and their impact on the development of damage prior to and during failure have been obtained using Digital Image Correlation (DIC). An experimental methodology is established to perform DIC at the mesoscopic scale using high magnification optics, enabling accurate, high spatial resolution analysis of the strains around the geometric discontinuity between adherends. It is demonstrated that the small through-thickness strains are critical in the development of damage in the joint around the discontinuity between adherends. Errors in the DIC technique are assessed using a robust morphological methodology to evaluate the quality of different speckle patterns based upon the properties of the speckles in the pattern. The strain data is manipulated to evaluate the principal stresses in the joint, which govern failure in the brittle epoxy matrix of the composite, providing a concise evaluation of the transfer of load between the adherends and damage initiation within the joint. The DIC results and methodology are validated against independent infra-red measurements using Thermoelastic Stress Analysis (TSA). Limitations in the TSA analysis approach are identified around joint discontinuity due to the varying principal stress direction. A new TSA analysis methodology is presented to overcome this. The results of the experimental analysis are used to validate a representative 2D finite element model modelling approach for adhesively bonded joints, showing good agreement to the experimental data. Finally the full-field DIC methodology is applied to analyse the response of a single lap joint during high strain rate loading, providing unprecedented full-field measurement of the strain fields up to failure.
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Mustansar, Zartasha. "Selection of modelling level of detail for incorporating stress analysis into evolutionary robotics simulations of extinct and extant vertebrates." Thesis, University of Manchester, 2015. https://www.research.manchester.ac.uk/portal/en/theses/selection-of-modelling-level-of-detail-for-incorporating-stress-analysis-into-evolutionary-robotics-simulations-of-extinct-and-extant-vertebrates(1210393b-d7e7-40dd-91d8-c33598aca8dc).html.
Full textAbstract:
This thesis concerns the simulation of locomotion in vertebrates. The state-of-the-art uses genetic algorithms together with solid body kinematics to generate possible solutions for stable gaits. In recent work, this methodology led to a hopping gait in a dinosaur and the researchers wondered if this was realistic. The purpose of the research carried out in this thesis was to examine whether quick and simple finite-element analyses could be added to the simulator, to evaluate a simple ―break or―not break failure criterion. A break would rule out gaits that might damage theowner‘s skeleton. Linear elastic analysis was considered as a possible approach as it would add little overhead to the simulations. The author used X-ray computed tomography and the finite element method to examine the axial loading of a barnacle goose femur. The study considered four levels of detail for a linear elastic simulation, finding that all the analyses carried out overestimated the strength of the bone, when considering safety factors. The conclusion is that to incorporate stress-strain analysis into the gait simulation requires more realistic models of bone behaviour that incorporate the nonlinear response of bone to applied loading. A new study focusing on the use of novel techniques such as model order reduction is recommended for future work. The outputs of this research include chapters written up as journal papers covering a 4D tomography experiment; a level of detail study; an analysis of a purported tendon avulsion injury in Tyrannosaurus rex and a review of the elastic properties of bone.
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Hy, Henrik, and Viktor Hällqvist. "Safety Analysis of Longtan High Dam Considering the Construction Process." Thesis, Umeå universitet, Institutionen för tillämpad fysik och elektronik, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-123289.
Full textAbstract:
To manage China’s growing demands of electricity, more and larger dams could be a part of the solution. It is important to evaluate and perform safety analysis for existing dams, in order to improve our understanding and knowledge about future dams. In this master thesis, a safety research of Longtan Dam on the Hongshui River in China was analysed. The main objectives in this research were to construct a 3D model and determine the critical points of large stress, strain and yield area in the dam for different cases.The factor of safety for sliding when primary loads were acting on the dam was calculated to be 0.50 for the non-overflow section of the dam and 0.48 for the overflow section. A safety factor against overturning was also calculated for the non-overflow and overflow section to 2.24 and 1.96 respectively. The results showed that the dam was safe from both sliding and overturning. The numerical results for distribution of stress, strain and yield area were simulated in 3D models by using ANSYS, a finite element program. Several cases for non-overflow and overflow sections of Longtan Dam were analysed for different heights and load combinations. For the first three cases where only self-weight was applied on the dam, high impacts of stress and strain were located at the dam heel, toe and at the largest maintenance tunnel of the dam. Appearance of plastic strain was also found around these areas. However, when primary loads were applied to the dam sections, the values of stress and strain became larger, especially in the toe area. In the last case when the dam was subjected to seismic activity, the distribution of stress and strain along the z-direction (along the dam) showed an uneven distribution, hence showing the importance of simulation in 3D.
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Rolle, Trenicka. "Lung Alveolar and Tissue Analysis Under Mechanical Ventilation." VCU Scholars Compass, 2014. http://scholarscompass.vcu.edu/etd/3398.
Full textAbstract:
Mechanical ventilation has been a major therapy used by physicians in support of surgery as well as for treating patients with reduced lung function. Despite its many positive outcomes and ability to maintain life, in many cases, it has also led to increased injury of the lungs, further exacerbating the diseased state. Numerous studies have investigated the effects of long term ventilation with respect to lungs, however, the connection between the global deformation of the whole organ and the strains reaching the alveolar walls remains unclear. The walls of lung alveoli also called the alveolar septum are characterized as a multilayer heterogeneous biological tissue. In cases where damage to this parenchymal structure insist, alveolar overdistension occurs. Therefore, damage is most profound at the alveolar level and the deformation as a result of such mechanical forces must be investigated thoroughly. This study investigates a three-dimensional lung alveolar model from generations 22 (alveolar ducts) through 24 (alveoli sacs) in order to estimate the strain/stress levels under mechanical ventilation conditions. Additionally, a multilayer alveolar tissue model was generated to investigate localized damage at the alveolar wall. Using ANSYS, a commercial finite element software package, a fluid-structure interaction analysis (FSI) was performed on both models. Various cases were simulated that included a normal healthy lung, normal lung with structural changes to model disease and normal lung with mechanical property changes to model aging. In the alveolar tissue analysis, strains obtained from the aged lung alveolar analysis were applied as a boundary condition and used to obtain the mechanical forces exerted as a result. This work seeks to give both a qualitative and quantitative description of the stress/strain fields exerted at the alveolar region of the lungs. Regions of stress/strain concentration will be identified in order to gain perspective on where excess damage may occur. Such damage can lead to overdistension and possible collapse of a single alveolus. Furthermore, such regions of intensified stress/strain are translated to the cellular level and offset a signaling cascade. Hence, this work will provide distributions of mechanical forces across alveolar and tissue models as well as significant quantifications of damaging stresses and strains.
48
Shah, Saujanya. "Finite Element Modelling of Compact Gears Using Strain Measurements." Thesis, KTH, Maskinkonstruktion (Avd.), 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-281777.
Full textAbstract:
Robot design and development has been the backbone of industrial automation and is in the forefront of accelerated development across all areas. Robot designers have been using simulations for reducing product development lead times. With growing demand for faster, precise and efficient robots, the requirements on computerized simulation for stress analysis has become stringent. While the product structure is mostly designed and developed from scratch, some components are sourced from suppliers, leaving a gap in the knowledge for modelling an entirety of a robot. This thesis applies a structured method to develop a grey-box model of the compact gears, which provides the robots its dexterity in a compact form factor. The method utilizes experimental strain measurements as a basis for building the model. Design of experiment is used as the guide for conducting FE analysis on robot links with unit load case, followed by scaling of stresses to actual load case. Simulated and measured stress plots are compared to conclude on optimum modelling approach. Further, the thesis proposes an alternative method for stress analysis of robot links by omitting the compact gear embodiment. While the method applies well on the robot links considered during the study, its validation across other links and robot architecture is yet to be performed. Finally, recommendations for implementation of proposed method and areas for expanding this thesis work are proposed.Robotdesign har varit ryggraden inom industriell automation och är i framkanten av utvecklingen inom alla områden. Robotdesigners använder sig av simuleringar för att korta utvecklingstider. Med växande krav på snabbare, effektiva och noggranna robotar, har kraven på datorsimuleringar ökat. Medan huvuddelen av strukturen är utvecklad från grunden, är några komponenter köpta från leverantörer vilket skapar ett glapp i kunskapen för att kunna modellera en hel robot. Det här examensarbetet använder en strukturerad metod för att utveckla en "grey-box" modell av en kompaktväxel, vilken tillåter robotens mångsidighet i ett kompakt format. Metoden använder töjningsmätningar till grund för att bygga modellen. Experimentell design används som en guide för att utföra FE analyser på robotdelar med enhetslastfall, vilka skalas till verkliga lastfall. Simulerade och uppmätta spänningar jämförs för att optimera modelleringen. Det föreslås även en metod där kompaktväxlarna inte modelleras som solider. Metoden fungerar väl för robotarmar som ingick i denna studie, dock bör den verifieras på andra modeller och delar. Slutligen föreslås implementering av metoden som tagits fram i denna rapport samt ytterligare arbete för att verifiera metoden.
49
Arefi, Mohammad Jawad. "Dynamic Characteristics and Evaluation of Ground Response for Sands with Non-Plastic Fines." Thesis, University of Canterbury. Civil & Natural Resources Engineering, 2014. http://hdl.handle.net/10092/9173.
Full textAbstract:
Deformational properties of soil, in terms of modulus and damping, exert a great influence on seismic response of soil sites. However, these properties for sands containing some portion of fines particles have not been systematically addressed. In addition, simultaneous modelling of the modulus and damping behaviour of soils during cyclic loading is desirable. This study presents an experimental and computational investigation into the deformational properties of sands containing fines content in the context of site response analysis. The experimental investigation is carried on sandy soils sourced from Christchurch, New Zealand using a dynamic triaxial apparatus while the computational aspect is based on the framework of total-stress one-dimensional (1D) cyclic behaviour of soil.
The experimental investigation focused on a systematic study on the deformational behaviour of sand with different amounts of fines content (particle diameter ≤ 75µm) under drained conditions. The silty sands were prepared by mixing clean sand with three different percentages of fines content. A series of bender element tests at small-strain range and stress-controlled dynamic triaxial tests at medium to high-strain ranges were conducted on samples of clean sand and silty sand. This allowed measurements of linear and nonlinear deformational properties of the same specimen for a wide strain range. The testing program was designed to quantify the effects of void ratio and fines content on the low-strain stiffness of the silty sand as well as on the nonlinear stress-strain relationship and corresponding shear modulus and damping properties as a function of cyclic shear strains.
Shear wave velocity, Vs, and maximum shear modulus, Gmax, of silty sand was shown to be significantly smaller than the respective values for clean sands measured at the same void ratio, e, or same relative density, Dr. However, the test results showed that the difference in the level of nonlinearity between clean sand and silty sands was small. For loose samples prepared at an identical relative density, the behaviour of clean sand was slightly less nonlinear as compared to sandy soils with higher fines content. This difference in the nonlinear behaviour of clean sand and sandy soils was negligible for dense soils. Furthermore, no systematic influence of fines content on the material damping curve was observed for sands with fines content FC = 0 to 30%.
In order to normalize the effects of fines on moduli of sands, equivalent granular void ratio, e*, was employed. This was done through quantifying the participation of fines content in the force transfer chain of the sand matrix. As such, a unified framework for modelling of the variability of shear wave velocity, Vs, (or shear modulus, Gmax) with void ratio was achieved for clean sands and sands with fines, irrespective of their fines content.
Furthermore, modelling of the cyclic stress-strain behaviour based on this experimental program was investigated. The modelling effort focused on developing a simple constitutive model which simultaneously models the soil modulus and damping relationships with shear strains observed in laboratory tests. The backbone curve of the cyclic model was adopted based on a modified version of Kondner and Zelasko (MKZ) hyperbolic function, with a curvature coefficient, a. In order to simulate the hysteretic cycles, the conventional Masing rules (Pyke 1979) were revised. The parameter n, in the Masing’s criteria was assumed to be a function of material damping, h, measured in the laboratory. As such the modulus and damping produced by the numerical model could match the stress-strain behaviour observed in the laboratory over the course of this study. It was shown that the Masing parameter n, is strain-dependent and generally takes values of n ≤ 2. The model was then verified through element test simulations under different cyclic loadings. It was shown that the model could accurately simulate the modulus and the damping simultaneously.
The model was then incorporated within the OpenSees computational platform and was used to scrutinize the effects of damping on one-dimensional seismic site response analysis. For this purpose, several strong motion stations which recorded the Canterbury earthquake sequence were selected. The soil profiles were modelled as semi-infinite horizontally layered deposits overlying a uniform half-space subjected to vertically propagating shear waves. The advantages and limitations of the nonlinear model in terms of simulating soil nonlinearity and associated material damping were further scrutinized.
It was shown that generally, the conventional Masing criteria unconservatively may underestimate some response parameters such as spectral accelerations. This was shown to be due to larger hysteretic damping modelled by using conventional Masing criteria. In addition, maximum shear strains within the soil profiles were also computed smaller in comparison to the values calculated by the proposed model. Further analyses were performed to study the simulation of backbone curve beyond the strain ranges addressed in the experimental phase of this study. A key issue that was identified was that relying only on the modulus reduction curves to simulate the stress-strain behaviour of soil may not capture the actual soil strength at larger strains. Hence, strength properties of the soil layer should also be incorporated to accurately simulate the backbone curve.
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Burford, Eva-Maria. "The analysis of the strain level and the predicted human error probability for critical hospital tasks." Thesis, Rhodes University, 2012. http://hdl.handle.net/10962/d1005182.
Full textAbstract:
South African hospitals, as a result of numerous factors, have the problem of an increasing workload for nursing staff, which in turn may affect patient treatment quality. This project aimed at addressing patient treatment quality specifically from the perspective of worker capabilities by investigating the strain level and predicted human error probability associated with specific patient-centered tasks in the South African health care sector. This was achieved through two independent yet interlinked studies which focused on seven patient-centred tasks. The tasks analysed were the tasks of setting up and changing intravenous medication, administering injection and pill medication, measuring blood glucose, temperature and heart rate and blood pressure. In the first study, work environment and task characteristics, task structure and execution were analysed. In addition to the task execution, the resulting strain levels, in the form of heart rate measures and subjective ratings of workload, were studied. The second study determined the error protocols and predictive error probability within the healthcare environment for the seven pre-defined tasks. The results for the first study established that different organizational and environment factors could affect task complexity and workload. The individual task components and information processing requirements for each task was also established. For the strain analysis, significant results for the tasks were determined for heart rate frequency and the heart rate variability measures, but some of these were contradictory. For the second study, specific error protocols and error reporting data were determined for the hospital where this research was conducted. Additionally the predictive error probability for the pre-defined tasks was determined. This combined approach and collective results indicate that strain and predictive error probability as a result of task workload can be determined in the field as well as being able to identify which factors have an effect on task strain and error probability. The value of this research lies in the foundation that the gathered information provides and the numerous potential applications of this data. These applications include providing recommendations aimed at improving nursing work environment with regards to workload, improving patient treatment as a result of a reduction in errors and the potential foundation these results provide for future research