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1
Knapp, Steven. „Mechanical Properties of an Inconel Dissimilar Metal Weld“. Thèse, Université d'Ottawa / University of Ottawa, 2014. http://hdl.handle.net/10393/31126.
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A pipe consisting of Inconel 600 welded to grade 106-B Carbon-Steel using Inconel 182 weld filler is used to transport heavy water in nuclear reactors. A confidential report concluded that cracking is one of the problems these pipes are currently facing. Before cracking can be fully understood the mechanical properties of the weld must be determined.
This thesis analyzed the pipe at various length-scales using optical microscopy, micro-hardness testing, small and large scale tensile testing and digital image correlation (DIC). This thesis successfully achieved it goals of determining the mechanical properties and creating a model of the Inconel dissimilar metal weld. It partially met the goal of observing fracture mechanisms as it was able to observe fracture in tensile samples but was not able to successfully track crack growth.
2
Salisbury, Shaun M. „A Method for Characterizing the Properties of Industrial Foams“. Diss., CLICK HERE for online access, 2005. http://contentdm.lib.byu.edu/ETD/image/etd990.pdf.
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3
Marquina, Edgar Alberto. „Use of Dynamic Mechanical Testing, WAXD and SEM Image Analysis to Study the Properties of Polypropylene/Calcium Carbonate Nanocomposites“. University of Akron / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=akron1269363578.
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4
Mahmud, Jamaluddin. „Development of a novel technique in measuring human skin deformation in vivo to determine its mechanical properties“. Thesis, Cardiff University, 2009. http://orca.cf.ac.uk/54890/.
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5
Demirci, Emrah. „Mechanical behaviour of thermally bonded bicomponent fibre nonwovens : experimental analysis and numerical modelling“. Thesis, Loughborough University, 2011. https://dspace.lboro.ac.uk/2134/8235.
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In contrast to composites and woven fabrics, nonwoven materials have a unique web structure, which is composed of randomly oriented fibres bonded in a pattern by mechanical, thermal or chemical techniques. The type of nonwovens studied in this research is a thermally bonded one with polymer-based bicomponent fibres. Such fibres have a core/sheath structure with outer layer (sheath) having a lower melting temperature than that of the core. In thermal bonding of such fibres, as the hot calender with an engraved pattern contacts the fibrous web, bond points are formed thanks to melting of the sheath material. Molten sheath material acts as an adhesive while core parts of the fibres remain fully intact in the bond points. On the other hand, web regions, which are not in contact with the hot engraved pattern, remain unaffected and form the fibre matrix that acts as a link between bond points. With two distinct regions, namely, bond points and fibre matrix, with different structures, nonwovens exhibit a unique deformation behaviour. This research aims to analyse the complex mechanical behaviour of thermally bonded bicomponent fibre nonwoven materials using a combination of experimental and numerical methods. A novel approach is introduced in the thesis to predict the complex mechanical behaviour of thermally bonded bicomponent fibre nonwovens under various threedimensional time-dependent loading conditions. Development of the approach starts with experimental studies on thermally bonded bicomponent fibre nonwovens to achieve a better understating of their complex deformation characteristics. Mechanical performance of single bicomponent fibres is investigated with tensile and relaxation tests since they are the basic constituents of nonwoven fabrics. The fabric microstructure, which is one of the most important factors affecting its mechanical behaviour, is examined with scanning electron microscopy and X-ray micro computed tomography techniques. At the final part of experimental studies, mechanical response of thermally bonded bicomponent fibre nonwovens is characterised with several mechanical tests. (Continues...).
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Weseman, Brian D. „The Effects of Retention Aid Dosage and Mechanical Energy Dissipation on Fiber Flocculation in a Flow Channel“. Diss., Georgia Institute of Technology, 2004. http://hdl.handle.net/1853/7960.
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Formation plays an important role in the end-use properties of paper products,
but before formation can be optimized to achieve superior properties, an understanding
about the causes of formation must be developed. Formation is caused by variations in
the basis weight of paper that are results of fiber floc formation before and during the
forming of the sheet. This project is a first step in a larger research program aimed at
studying formation. By observing the effects that mechanical energy dissipation (in the
form of turbulence) and retention chemical dosage have on floc formation, we may
develop a better understanding of how to control formation.
In this study, a rectangular cross-section flow channel was constructed to aid in
the acquisition of digital images of a flowing fiber suspension. The furnish consisted of a
55:45 spruce:pine bleached market pulp mix from a Western Canadian mill. Turbulence
was varied by changing the flow rate; Reynolds numbers achieved range from 20,000 to
40,000. The retention aid used was a cationic polyacrylamide with a medium charge
density. Dosage of the retention aid was varied from 0 to 2 pounds per ton OD fiber.
Digital images of the flowing fiber suspension were acquired with a professional digital
SLR camera with a forensics-quality lens. Three separate image analysis techniques were
used to measure the flocculation state of the fiber suspension: morphological image
operations, formation number analysis, and fast Fourier transform analysis.
Morphological image analysis was capable of measuring floc size increases seen in
the acquired floc images. It was shown how floc diameter could increase simultaneously
with decreasing total floc area and total floc number. A regression model relating
retention aid dosage and energy dissipation was constructed in an effort to predict
flocculation. The regression model was used to predict F2 (formation number squared)
results from the study. The interaction effect RE was shown to have a differing effect across the retention aid dosage levels. As a result, this model and technique may prove to
be a beneficial tool in optimizing retention aid applications.
7
永正, 邵., und Yongzheng Shao. „Study on the effects of matrix properties on the mechanical properties of carbon fiber reinforced plastic composites“. Thesis, https://doors.doshisha.ac.jp/opac/opac_link/bibid/BB12902982/?lang=0, 2015. https://doors.doshisha.ac.jp/opac/opac_link/bibid/BB12902982/?lang=0.
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It was found that a significant improvement of mechanical properties of CFRPs can be achieved by the adjustment of the matrix properties such as toughness and CF/matrix adhesion via the chemical modification, as well as the physical modification by a small amount of cheap and environment-friendly nano fibers. Based on investigation of fracture mechanisms at macro/micro scale, the effects of matrix properties and nano fiber on the mechanical properties of CFRP have been discussed. Subsequently, the relationship has been characterized by a numerical model to show how to modulate the parameters of the matrix properties to achieve excellent fatigue properties of CFRP.博士(工学)
Doctor of Philosophy in Engineering
同志社大学
Doshisha University
8
Ulm, Daniel. „Optimalizace způsobu očkování litiny s kuličkovým grafitem“. Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2018. http://www.nusl.cz/ntk/nusl-382194.
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The master‘s thesis deals in theoretical part with the casting classification, ductile iron casting, its inoculation and modification and quality evaluation using thermal analysis, image analysis and testing of mechanical properties. The aim of the practical part was to test the effects of preconditioning on the properties of ductile iron and to find out whether it is able to replace the current method of inoculation or to increase the mechanical properties of ductile iron castings. The state of the ductile iron was under control by spectral and thermal analysis. The mechanical properties and image analysis were checked on finished casting.
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Straka, Jakub. „Hodnocení porezity u tlakově litých odlitků z Al slitin“. Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2011. http://www.nusl.cz/ntk/nusl-229463.
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The purpose of this diploma thesis is an evaluation of die-castings porosity, eventually the evaluation of seats with local squeeze in connection with their mechanical and structural properties. The swatches of alloy AISi9Cu3 were taken from the engine block made by Škoda Auto Company, Mladá Boleslav. To the evaluation and the comparison of the results there were used value of porosity with own measure and other student´s thesis of Brno University of technology. Sets of mechanical and structural properties were selected, evaluated and tested by statistical programs.
10
Subramaniam, Dhananjay Radhakrishnan. „Role of Elasticity in Respiratory and Cardiovascular Flow“. University of Cincinnati / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1522054562050044.
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11
Martin, Boris. „Etudes expérimentales de l’influence des paramètres de conception des renforts NCF unidirectionnels sur leurs propriétés de transport et leurs performances mécaniques“. Thesis, Paris, ENMP, 2015. http://www.theses.fr/2015ENMP0084.
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L'augmentation des dimensions des éoliennes est nécessaire pour réduire le coût du rendement énergétique des parcs éoliens. L'optimisation de ces structures est liée aux renforts fibreux qu'elles utilisent. La rigidité des pâles d'éoliennes provient des longerons en composites monolithiques mis en forme à partir de renforts NCF (« Non-Crimp Fabrics ») unidirectionnels et de résine thermodurcissable. Les renforts se présentent sous forme d'empilement de deux couches (0° et+/- 80°) cousues dans l'épaisseur par un fil polyester. La structure fibreuse, contrôlée par les paramètres de conception, influence les liens de causes à effets entre les paramètres de conception et les performances du renfort et du composite. Il est donc nécessaire d'optimiser les composites pour leur application. Trois paramètres de conception sont étudiés pour établir ces liens : la longueur de couture, le dessin de couture et la masse linéique de la trame. Ces liens sont dévoilés par la mise en relation de données morphologiques issues d'analyse d'images du renfort sec et du composite avec les propriétés macroscopiques déterminées par le biais de moyens expérimentaux. Ces derniers permettent notamment de déterminer le tenseur de perméabilité hydraulique des renforts ainsi que les propriétés élastiques des composites. Il apparait que chacun des paramètres étudiés influence l'hétérogénéité des composites. Cette caractéristique est favorable pour le procédé d'infusion mais affecte la tenue en fatigue des longerons. L'optimisation des renforts NCF pour leur application requiert donc d'établir un compromis. Une autre solution consisterait à permettre une évolution de la morphologie du composite lors de la mise en forme, pour passer d'un renfort sec hétérogène à un composite homogène en terme de fraction volumique de fibreThe energetic pricing of windmills involves the production cost of wind turbines and theirlifespan. Increasing the performances of these structures comes with an increase of the bladesdimensions. The spar caps of the latters, providing the strength to the blades, are made ofunidirectional glass fiber reinforcement known as NCF (Non-Crimp Fabrics). They involve two layers ofspecific orientations (0° and +/- 80°) stitched together. The architecture formed by the reinforcement isdependent on the design parameters which control the performance, on the fabric during the infusionprocess, and on the composite in the final structure. Therefore, the optimization of the NCF for thewindmill application is controlled by the design parameters. Three parameters (the stitch length, thestitch pattern and the weft Tex) are studied in order to establish the links morphology / process andmorphology / mechanical performances. Experimental investigations are undertaken to determine boththe hydraulic permeability tensor of the fabrics and the elastic properties of their composite. Thesemacroscopic properties are related to the morphology determined using images analysis technics. It isdemonstrated that each of the design parameters impacts the heterogeneity of the composite. Highheterogeneity allows improving the performance during the infusion process while reducing themechanical one. The optimization of the NCF using the design parameters requires setting acompromise in the heterogeneity of the architecture formed by the reinforcement. Another solutionwould consist in allowing the morphology to evolve during the infusion process, to go from an openstructure that eases the flow to a homogeneous structure safer for the windmill application
12
Evans, T. Matthew. „Microscale Physical and Numerical Investigations of Shear Banding in Granular Soils“. Diss., Georgia Institute of Technology, 2005. http://hdl.handle.net/1853/7576.
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Under loading conditions found in many geotechnical structures, it is common to observe failure in zones of high localized strain called shear bands. Existing models predict these localizations, but provide little insight into the micromechanics within the shear bands. This research captures the variation in microstructure inside and outside of shear bands that were formed in laboratory plane strain and two-dimensional discrete element method (DEM) biaxial compression experiments.
Plane strain compression tests were conducted on dry specimens of Ottawa 20-30 sand to calibrate the device, assess global response repeatability, and develop a procedure to quantitatively define the onset of localization. A new methodology was employed to quantify and correct for the additional stresses imparted by the confining membrane in the vicinity of the shear band. Unsheared and sheared specimens of varying dilatancy were solidified using a two-stage resin impregnation procedure. DEM tests were performed using an innovative servo-controlled flexible lateral confinement algorithm to provide additional insights into laboratory results.
The solidified specimens were sectioned and the resulting surfaces prepared for microstructure observation using bright field microscopy and morphological analysis. Local void ratio distributions and their statistical properties were determined and compared. Microstructural parameters for subregions in a grid pattern and along predefined inclined zones were also calculated. Virtual surfaces parallel to the shear band were identified and their roughnesses assessed. Similar calculations were performed on the DEM simulations at varying strain levels to characterize the evolution of microstructure with increasing strain.
The various observations showed that the mean, standard deviation, and entropy of the local void ratio distributions all increased with increasing strain levels, particularly within regions of high local strains. These results indicate that disorder increases within a shear band and that the soil within the shear band does not adhere to the classical concept of critical state, but reaches a terminal void ratio that is largely a function of initial void ratio. Furthermore, there appears to be a transition zone between the far field and the fully formed shear block, as opposed to an abrupt delineation as traditionally inferred.
13
Krahula, Karel. „Analýza změn struktury a vlastností slitiny Al-Si během odstátí taveniny“. Doctoral thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2021. http://www.nusl.cz/ntk/nusl-446742.
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This thesis is dedicated to the production of aluminum casting alloys. It maps the course of changes in the morphology of eutectic and its influence on mechanical properties during the long-term meltdown. In particular, the use of image analysis methods contributes to describing these processes. The presented results show that the eutectic shape does not change even during the meltdown for 110 minutes. There is only a roughing and an increase in grain size. There was also no influence on the mechanical properties that fit the practical application of the alloy examined
14
Abedsoltan, Hossein. „Meso-Scale Wetting of Paper Towels“. Miami University / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=miami1501246506048675.
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15
Baimpas, Nikolaos. „'Hybrid' non-destructive imaging techniques for engineering materials applications“. Thesis, University of Oxford, 2014. http://ora.ox.ac.uk/objects/uuid:1aa00fed-34e6-4a5e-951b-c710e21ac23c.
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The combination of X-ray imaging and diffraction techniques provides a unique tool for structural and mechanical analysis of engineering components. A variety of modes can be employed in terms of the spatial resolution (length-scale), time resolution (frequency), and the nature of the physical quantity being interrogated. This thesis describes my contributions towards the development of novel X-ray “rich” imaging experimental techniques and data interpretation. The experimental findings have been validated via comparison with other experimental methods and numerical modelling. The combination of fast acquisition rate and high penetration properties of X-ray beams allows the collection of high-resolution 3-D tomographic data sets at submicron resolution during in situ deformation experiments. Digital Volume Correlation analysis tools developed in this study help understand crack propagation mechanisms in quasi-brittle materials and elasto-plastic deformation in co-sprayed composites. For the cases of crystalline specimens where the knowledge of “live” or residual elastic strain distributions is required, diffraction techniques have been advanced. Diffraction Strain Tomography (DST) allows non-destructive reconstruction of the 2-D (in-plane) variation of the out-of-plane strain component. Another diffraction modality dubbed Laue Orientation Tomography (LOT), a grain mapping approach has been proposed and developed based on the translate-rotate tomographic acquisition strategy. It allows the reconstruction of grain shape and orientation within polycrystalline samples, and provides information about intragranular lattice strain and distortion. The implications of this method have been thoroughly investigated. State-of-the-art engineering characterisation techniques evolve towards scrutinising submicron scale structural features and strain variation using the complementarity of X-ray imaging and diffraction. The first successful feasibility study is reported of in operando stress analysis in an internal combustion engine. Finally, further advancement of ‘rich’ imaging techniques is illustrated via the first successful application of Time-of-Flight Neutron Diffraction Strain (TOF-NDST) tomography for non-destructive reconstruction of the complete strain tensor using an inverse eigenstrain formulation.
16
Zhao, Nilu. „Haze measurements through image analysis“. Thesis, Massachusetts Institute of Technology, 2014. http://hdl.handle.net/1721.1/92216.
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Thesis: S.B., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2014.Cataloged from PDF version of thesis.
Includes bibliographical references (page 28).
In the recent years, Singapore has been affected by haze caused by slash-and-bum fires in Indonesia. Currently, haze concentration is measured by filtering air samples at various stations in Singapore. In this thesis, optical approaches to haze measurements are explored. Images of haze were taken in fifteen minute intervals in June, 2013. These images were analyzed to obtain image contrast, and power spectral density functions. The power spectral density functions were characterized by maximum power, full width at half maximum, second and third moments, and exponential fit. Out of these methods, contrast and exponential fit results showed trend to the Pollutant Standards Index (PSI) values provided by the National Environmental Agency (NEA). Further studies on mapping contrast to PSI values are recommended.
by Nilu Zhao.
S.B.
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Loveless, Thomas A. „Mechanical Properties of Kenaf Composites Using Dynamic Mechanical Analysis“. DigitalCommons@USU, 2015. https://digitalcommons.usu.edu/etd/4310.
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Natural fibers show potential to replace glass fibers in thermoset and thermoplastic composites. Kenaf is a bast-type fiber with high specific strength and great potential to compete with glass fibers.
In this research kenaf/epoxy composites were analyzed using Dynamic Mechanical Analysis (DMA). A three-point bend apparatus was used in the DMA testing. The samples were tested at 1 hertz, at a displacement of 10 μm, and at room temperature.
The fiber volume content of the kenaf was varied from 20%-40% in 5% increments. Ten samples of each fiber volume fraction were manufactured and tested. The flexural storage modulus, the flexural loss modulus, and the loss factor were reported. Generally as the fiber volume fraction of kenaf increased, the flexural storage and flexural loss modulus increased. The loss factor remained relatively constant with increasing fiber volume fraction.
Woven and chopped fiberglass/epoxy composites were manufactured and tested to be compared with the kanaf/epoxy composites were manufactured and tested to be compared with the kenaf/epoxy composites. Both of the fiberglass/epoxy composites reported higher flexural storage and flexural loss modulus values. The kenaf/epoxy composites reported higher loss factor values. The specific flexural storage and specific flexural loss modulus were calculated for both the fiberglass and kenaf fiber composites. Even though the kenaf composites reported a lower density, the fiberglass composites reported higher specific mechanical properties.
18
MacLean, Sean. „Brain tissue analysis of mechanical properties /“. Connect to resource, 2010. http://hdl.handle.net/1811/44968.
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Reda, Ali. „A multiscale mechanical study of flax stems and fibres for the development of an in-the-field tool capable of predicting optimum retting“. Electronic Thesis or Diss., Université de Lille (2022-....), 2023. http://www.theses.fr/2023ULILN055.
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L'agriculture 4.0 se développe actuellement rapidement en termes de recherche, de développement et d'applications commerciales. L'objectif de l'agriculture 4.0 est d'utiliser la technologie pour améliorer tous les domaines de l'agriculture. L'agriculture 4.0 est tellement vaste que si l'on veut y contribuer, il faut choisir un domaine spécifique. Le domaine choisi pour l'étude de ce doctorat est la production de fibres de lin. Les fibres de lin sont des fibres naturellement solides qui peuvent être extraites des tiges de lin. Les tiges de lin ont évolué pour avoir des fibres robustes d'un diamètre de l'ordre du micromètre qui courent le long de l'extérieur de la tige et sont maintenues en place dans le tissu externe de la tige. Une fois extraites et isolées, les fibres de lin ont de nombreuses applications, allant des textiles aux matériaux composites. Afin de faciliter l'extraction mécanique des fibres de lin de leurs tiges mères, les tiges subissent un processus connu sous le nom de « rouissage ». Le rouissage entraîne la décomposition du tissu externe (appelé lamelle moyenne) entre les fibres. Une forme courante de rouissage est connue sous le nom de « rouissage de rosée ». Dans le rouissage de la rosée, des processus naturels tels que les bactéries et les champignons produisent des enzymes qui décomposent la lamelle centrale et séparent progressivement les grappes de fibres et les fibres des grappes. La durée du rouissage dépend fortement des conditions météorologiques. Un rouissage insuffisant entraîne une extraction difficile des fibres dans l'usine, tandis qu'un rouissage excessif peut compromettre la qualité des fibres. On sait depuis longtemps qu'il existe un point de rouissage optimal - même les anciens le savaient. Certains agriculteurs artisans qualifiés sont capables de juger ce point par une combinaison de manipulation manuelle des tiges, d'observation des dommages causés aux tissus externes par cette manœuvre, et aussi d'observation de la couleur et de l'odeur des tiges au cours de ce test très habile, mais artisanal. Il est clair que l'artisan effectue des tests de laboratoire rudimentaires littéralement « sur le terrain ». Il semblerait donc logique d'essayer de quantifier ces tests et de voir si un outil fiable peut être mis au point pour aider l'artisan. Et c'est exactement ce que d'autres ont tenté de faire. L'introduction de la thèse donne des exemples de tentatives de fabrication d'outils de rouissage optimal dans les années 1980 et suivantes. Inspirés par ces premiers travaux, les travaux de cette thèse tentent une caractérisation mécanique multi-échelle complète des tiges et des fibres de lin pendant un cycle de rouissage (été 2022) et, de manière quelque peu ambitieuse, réalisée en temps réel - à notre connaissance pour la première fois. La caractérisation mécanique comprend des essais mécaniques macroscopiques (flexion, écrasement et torsion de la tige), ainsi que des essais mécaniques microscopiques inédits sur des fibres de lin individuelles à l'aide de nouvelles méthodes inspirées des MEMS. En outre, les propriétés mécaniques nanoscopiques de la paroi cellulaire primaire des fibres de lin en cours de rouissage ont été caractérisées à l'aide de l'AFM par nanoindentation. Au fur et à mesure que le travail expérimental, l'analyse via la modélisation analytique et l'interprétation descendent en échelle, de la macro au nano en passant par le micro, nous en apprenons un peu plus sur la manière dont le rouissage affecte les tiges, leurs propriétés et leurs fibres. En plus de l'apprentissage, un résultat très positif du doctorat est que l'on est capable de suggérer un mécanisme de dommage induit mécaniquement dans les tiges, qui pourrait être la base d'un outil. On peut cependant noter que la nature multiparamétrique incontrôlable du sujet, par exemple le temps, signifie que plusieurs études seraient nécessaires pour confirmer sans aucun doute les observations d'un seul cycle de rouissageAgriculture 4.0, also known under several aliases such as ‘digital agriculture', ‘smart farming', and ‘e-farming' is currently developing rapidly in terms of research, development, and commercial applications. As with Agriculture 1.0, 2.0, and 3.0, the objective of Agriculture 4.0 is the use of technology to improve all areas of agriculture. In Agriculture 4.0 it is the application of microelectronics and microtechnologies. Unlike before, these technologies bring things such as the internet-of-things, big data, telecommunications, novel sensing, rapid feedback, data analysis, connectivity, artificial intelligence etc. In principle, all these areas should result in a massive modernization of farming in terms of organisation, yield, efficiency, and quality of produce. However, Agriculture 4.0 is so vast that if one is to contribute to it, even in a minor way, one has to choose a specific area to contribute. The area chosen for the study in this PhD was flax fibre production. Flax fibres are naturally strong fibres which can be extracted from flax stems. The flax stems have evolved to have robust micrometre-diameter fibres running the length of the outside of the stem, and held in place in the external tissue of the stem. Once extracted and isolated, flax fibres have numerous applications ranging from textiles to composite materials. In order to facilitate the mechanical extraction of flax fibres from their parent stems, the stems undergo a process known as ‘retting'. Retting leads to the breakdown of the external tissue between the fibres. A common form of retting is known as ‘dew retting'. In dew retting, natural processes such as bacteria and fungi result in enzymes which break down the middle lamella and gradually separate fibre bunches and fibres from bunches. The length of dew retting depends heavily on the weather. Too little retting results in difficult fibre extraction in the factory, too much retting can result in a compromise in fibre quality. It has long been known that there is an optimum retting point-even the ancients knew this. Certain skilled artisan farmers are able to judge this point via a combination of manual manipulation of the stems, observation of damage caused to the external tissue via this manoeuvre, and also observing the colour and the smell of the stems during this very skilled, but artisanal, testing. It is clear that the artisan is performing rudimentary laboratory tests quite literally ‘in-the-field'. It would seem logical therefore to try to quantify such tests and see if a reliable tool can be made to help the artisan. And indeed, this is exactly what others have attempted. The introduction of the PhD gives examples of attempts to make optimal-retting tools in the 1980s and after. Inspired by this early work, the work of this PhD attempts a full multiscale mechanical characterization of flax stems and fibres during a retting cycle (summer 2022) and, somewhat ambitiously, performed in real time-to our knowledge for the first time. The mechanical characterization involved macroscopic mechanical tests (bending, crushing, and twisting), as well as novel microscopic mechanical testing of single flax fibres using novel methods inspired by MEMS. In addition, the nanoscopic mechanical properties of the primary cell wall of retting flax fibres was characterised using nanoindentation AFM. As the experimental work, analysis via analytical modelling, and interpretation descends in scale from macro, through micro, to nano, we learn a little more of how the retting affects the stems, their properties, and their fibres. In addition to simply learning, a very positive outcome of the PhD is that one is able to suggest a mechanically-induced damage mechanism in stems which could be the basis for a tool. One can note however, that the uncontrollable multiparameter nature of the subject, e.g. the weather, means that several studies would be needed to confirm beyond doubt observations from a single retting cycle
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Pinfold, Martyn Keith. „Composite mechanical properties for use in structural analysis“. Thesis, University of Warwick, 1995. http://wrap.warwick.ac.uk/3995/.
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In order to be able to undertake an analysis of a component the designer will need to know the properties of the material being used. The aim of this work is help the design engineer such that the mechanical properties of continuous glass fibre reinforced composite material can be determined and used in the design analysis of components manufactured from this material. The literature survey has shown that for the material considered here, then given the constituent properties, the fibre arrangement and the fibre volume fraction, the composite mechanical properties may be determined mathematically by the use of micromechanical equations. The micromechanical prediction of the mechanical properties of uni-directional, random and woven fibre reinforced composites has been examined. The variation of these mechanical properties that may occur in a composite component due to the manufacturing process has been highlighted as being of importance. This has been studied to determine whether such a variation is significant by analysing examples of composite components and plates. The results from these analyses have been correlated with experimental results and investigated to study the importance of such variations in properties. Many micromechanical equations have been found in the literature for the prediction of the mechanical properties of continuous fibre reinforced composite materials. An accuracy of the predicted properties to within 10% of the experimental data was concluded to be acceptable and good enough for initial design purposes as design engineers are not usually able to design to such tight tolerances. This work has shown that further development of the micromechanical theories is not the most important problem concerning the prediction of the mechanical properties. These properties can currently be predicted with acceptable accuracy from the micromechanical equations already available in the literature. However, the design engineer is unlikely to have knowledge of the micromechanical equations necessary to determine the required properties. It is only by undertaking a large literature survey that the designer would be able to find this information. Many of the micromechanical equations require the use of an empirical factor. The knowledge of a value for such a factor is again something that would not be readily available to the designer. Rather than concentrating upon improving the micromechanical predictions, this work shows that effort should be made to understand the influence of other factors upon the mechanical properties of composite materials. In particular, the behaviour and flow of the material during the manufacturing process has been highlighted as being of importance as it can cause a significant variation in the properties. Thus, analyses of composite components cannot assume that the mechanical properties are constant throughout, and it is therefore necessary to first model the manufacturing process to determine the mechanical properties before undertaking a structural analysis.
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Krus, David Jr. „Finite element analysis of thin film mechanical properties“. Case Western Reserve University School of Graduate Studies / OhioLINK, 1992. http://rave.ohiolink.edu/etdc/view?acc_num=case1059745475.
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Cooley, Dane A. „Effects of Reclaimed Asphalt Pavement on Mechanical Properties of Base Materials“. Diss., CLICK HERE for online access, 2005. http://contentdm.lib.byu.edu/ETD/image/etd1094.pdf.
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King, Raymond John. „Dynamic Mechanical Properties of Resilin“. Thesis, Virginia Tech, 2010. http://hdl.handle.net/10919/33677.
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Resilin is an almost perfect elastic protein found in many insects. It can be stretched up to 300% of its resting length and is not affected by creep or stress relaxation. While much is known about the static mechanical properties of resilin, it is most often used dynamically by insects. Unfortunately, the dynamic mechanical properties of resilin over the biologically relevant frequency range are unknown. Here, nearly pure samples of resilin were obtained from the dragonfly, Libellua luctuosa, and dynamic mechanical analysis was performed with a combination of time-temperature and time-concentration superposition to push resilin through its glass transition. The tensile properties for resilin were found over five different ethanol concentrations (65, 70, 82, 86 and 90% by volume in water) between temperatures of -5°C and 60°C, allowing for the quantification of resilinâ s dynamic mechanical properties over the entire master curve. The glass transition frequency of resilin in water at 22°C was found to be 106.3 Hz. The rubber storage modulus was 1.6 MPa, increasing to 30 MPa in the glassy state. At 50 Hz and 35% strain over 98% of the elastic strain energy can returned each cycle, decreasing to 81% at the highest frequencies used by insects (13 kHz). However, despite its remarkable ability to store and return energy, the resilin tendon in dragonflies does not act to improve the energetic efficiency of flight or as a power amplifying spring. Rather, it likely functions to passively control and stabilize the trailing edge of each wing during flight.Master of Science
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Duff, Richard A. „Determination of bulk mechanical properties of nano structures from molecular dynamic simulation“. Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2003. http://library.nps.navy.mil/uhtbin/hyperion-image/03Jun%5FDuff.pdf.
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Khasawneh, Qais Azzam. „On the Analysis of Mechanical Properties of Nanofiber Materials“. University of Akron / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=akron1226939318.
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Cao, Kunlin. „Mechanical analysis of lung CT images using nonrigid registration“. Diss., University of Iowa, 2012. https://ir.uiowa.edu/etd/2833.
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Image registration plays an important role in pulmonary image analysis. Accurate image registration is a challenging problem when the lungs have deformation with large distance. Registration results estimate the local tissue movement and are useful for studying lung mechanical quantities. In this thesis, we propose a new registration algorithm and a registration scheme to solve lung CT matching problems. Approaches to study lung functions are discussed and presented through a practical application. The overall objective of our project is to develop image registration techniques and analysis approaches to measure lung functions at high resolution. We design a nonrigid volumetric registration algorithm to catch lung motion from a pair of intrasubject CT images acquired at different inflation levels. This registration algorithm preserves both parenchymal tissue volume and vesselness measure, and is regularized by a linear elasticity cost. Validation methods for lung CT matching are introduced and used to evaluate the performance of different registration algorithms. Evaluation shows the feature-based vesselness constraint can efficiently improve the registration accuracy around lung boundaries and in the base lung region. Meanwhile, a new scheme to solve complex registration problem is introduced utilizing both surface and volumetric registration. The first step of this scheme is to register the boundaries of two images using surface registration. The resulting boundary displacements are extended to the entire ROI domains using the Element Free Galerkin Method (EFGM) based on weighted extended B-Splines (WEB-Splines). These displacement fields are used as initial conditions for the tissue volume– and vessel–preserving non-rigid registration over the object domain. Both B-Splines and WEB-Splines are used to parameterize the transformations. Our algorithms achieve high accuracy and provide reasonable lung function maps. The mean errors on landmarks, vessel locations, and fissure planes are on the order of 1 mm (sub-voxel level). Furthermore, we establish methods based on registration derived transformation to analyze mechanical quantities and measure regional lung function. The proposed registration method and lung function measurement are applied on a practical application to detect mechanical alternations in the lung following bronchoalveolar lavage, which achieves satisfactory results and demonstrates the applicability of our proposed approaches.
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Lehn, Andrea Michelle. „Volumetric analysis of lamprey hydrodynamics using synthetic aperture particle image velocimetry“. Thesis, Massachusetts Institute of Technology, 2019. https://hdl.handle.net/1721.1/121805.
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Thesis: S.M., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2019Cataloged from PDF version of thesis.
Includes bibliographical references (pages 85-89).
An experimental procedure to study lamprey hydrodynamics using Synthetic Aperture Particle Image Velocimetry (SAPIV) was developed and applied in this thesis. Volumetric, time-resolved flow field analysis of freely swimming lamprey, Petromyzon marinus, are presented from SAPIV experiments. As the most primitive living vertebrate, this eel-shaped fish has served as a model organism for understanding locomotion control in vertebrates. Brain and spinal cord mappings of the lamprey nervous system are well characterized and share key features with neural systems across the animal kingdom. However, a comprehensive understanding of locomotion control strategies in lampreys hinges upon characterizing the external fluid environment they experience. Thus, its role as a model organism has motivated this hydrodynamic study. Lamprey are slender-bodied, anguilliform swimmers that move by sending a traveling wave of increasing amplitude from head to tail, around Reynolds number order 10⁵. Generally, lamprey swim by advecting momentum downstream via the traveling wave on the body, creating a thrust-like wake with downstream momentum flux. Previous investigation suggests that lamprey locomotion arises from complex 3D flow field interactions, although this has never been studied using a live fish. To investigate the degree to which 3D effects are meaningful in lamprey hydrodynamics, SAPIV was used to study their unconstrained swimming in a quiescent tank more than 15 body diameters deep. SAPIV velocity fields show that a bifurcated wake consisting of predominantly lateral jets is produced by lamprey. Downstream velocities are also observed although they are about one half the magnitude of lateral velocities. This measurement contribution moves towards an understanding of lamprey swimming behavior and builds upon the foundation for understanding the hydrodynamics of unsteady, flexible propulsors.
by Andrea Michelle Lehn.
S.M.
S.M. Massachusetts Institute of Technology, Department of Mechanical Engineering
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Ding, Kai. „Registration-based regional lung mechanical analysis“. Thesis, University of Iowa, 2008. http://ir.uiowa.edu/etd/20.
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Ramakrishna, Yogendra Jayanth. „Image Analysis Methods For Additive Manufacturing Applications“. Thesis, Högskolan Väst, Avdelningen för avverkande och additativa tillverkningsprocesser (AAT), 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:hv:diva-15891.
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There is an upsurge of research interest on Ni-based superalloys additively manufactured (AM) in aerospace sectors. However, achieving the accuracy and quality of the AM part is a challenging task because it is a process of adding material layer by layer with different process parameters. Hence, defects can be observed, and these defects have a detrimental effect on the mechanical properties of the material. Also, AM materials commonly portray a columnar grain structure which also makes it difficult to determine the average grain size because while using the commonly used intercept method, the grain boundaries do not intercept to the test line appropriately. It is important to measure the defects and grain size before performing mechanical testing on the material. Defect measurement and grain size measurements are usually measured manually which results in longer lead time. This work is addressed towards testing recipes in the automated image analysis software to optimize the lead time with good accuracy. Haynes 282, a γ' strengthened superalloy is used in this work. It was assumed that 1,5mm of material from the surface will be machined away so defects had to be measured in this region of interest. The image analysis tools used to test its potentials are MIPAR and ImageJ. Initially, five images in MIPAR and Image J were tested keeping the manual measurements as a benchmark. From this part, it was concluded that metallography and image quality play an important role in the automated measurement. Also, basic Image J software cannot give the measurements of lack of fusion in terms of caliper diameter (longest measurable diameter). Hence, MIPAR was chosen for the application because it was more promising. In the next part, 15 samples were used with manual measurements from a stitched sample and batch processing with MIPAR. The total caliper diameter results were plotted to compare manual measurements and MIPAR. It was observed that scratches were measured as lack of fusion defects at few instances by MIPAR which were further refined using a post-processing function. The defect density results were plotted and compared as well. Due to the difference in calculation of region of interest, the difference in results was observed.To perform the grain size measurement, Haynes 282 was used in HIP and heat treated condition, achieving equiaxed grains. The etchant should be appropriate to reveal the grains. Hence four different etchants were used in this study hydrogen peroxide+HCl, Kallings (electro etch), Kallings (swab) and diluted oxalic acid. This measurement was performed on the material which was cut along the build direction as well as 90º to the growth direction. Since there is no standard for additively manufactured material yet, the results were tested with hall-petch equation to be convinced of the results obtained. It was observed that MIPAR recipe portrayed good results. The results of manual measurements and MIPAR measurements were plotted and compared. It was observed that Hydrogen peroxide and Kallings (swab) showed the grains evidently but twin boundaries were revealed as well. MIPAR calculated the twin boundaries as grains so it over calculated than manual measurements. Kallings (electro etch) and diluted oxalic acid did not reveal the grains so it was difficult for MIPAR to identify the grains.
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Cros, Olivier. „Structural properties of the mastoid using image analysis and visualization“. Doctoral thesis, Linköpings universitet, Institutionen för medicinsk teknik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-137288.
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The mastoid, located in the temporal bone, houses an air cell system whose cells have a variation in size that can go far below current conventional clinical CT scanner resolution. Therefore, the mastoid air cell system is only partially represented in a CT scan. Where the conventional clinical CT scanner lacks level of minute details, micro-CT scanning provides an overwhelming amount of ne details. The temporal bone being one of the most complex in the human body, visualization of micro-CT scanning of this boneawakens the curiosity of the experimenter, especially with the correct visualization settings. This thesis first presents a statistical analysis determining the surface area to volume ratio of the mastoid air cell system of human temporal bone, from micro-CT scanning using methods previously applied for conventional clinical CT scans. The study compared current results with previous studies, with successive downsampling the data down to a resolution found in conventional clinical CT scanning. The results from the statistical analysis showed that all the small mastoid air cells, that cannot be detected in conventional clinical CT scans, do heavily contribute to the estimation of the surface area, and in consequence to the estimation of the surface area to volume ratio by a factor of about 2.6. Such a result further strengthens the idea of the mastoid to play an active role in pressure regulation and gas exchange. Discovery of micro-channels through specific use of a non-traditional transfer function was then reported, where a qualitative and a quantitative pre-analysis were performed and reported. To gain more knowledge about these micro-channels, a local structure tensor analysis was applied where structures are described in terms of planar, tubular, or isotropic structures. The results from this structural tensor analysis suggest these microchannels to potentially be part of a more complex framework, which hypothetically would provide a separate blood supply for the mucosa lining the mastoid air cell system. The knowledge gained from analysing the micro-channels as locally providing blood to the mucosa, led to the consideration of how inflammation of the mucosa could impact the pneumatization of the mastoid air cell system. Though very primitive, a 3D shape analysis of the mastoid air cell system was carried out. The mastoid air cell system was first represented in a compact form through a medial axis, from which medial balls could be used. The medial balls, representative of how large the mastoid air cells can be locally, were used in two complementary clustering methods, one based on the size diameter of the medial balls and one based on their location within the mastoid air cell system. From both quantitative and qualitative statistics, it was possible to map the clusters based on pre-defined regions already described in the literature, which opened the door for new hypotheses concerning the effect of mucosal inflammation on the mastoid pneumatization. Last but not least, discovery of other structures, previously unreported in the literature, were also visually observed and briefly discussed in this thesis. Further analysis of these unknown structures is needed.
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Mendelson, Leah Rose. „Volumetric analysis of fish swimming hydrodynamics using synthetic aperture particle image velocimetry“. Thesis, Massachusetts Institute of Technology, 2013. http://hdl.handle.net/1721.1/85223.
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Thesis: S.M., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2013.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (pages 81-86).
Abstract This thesis details the implementation of a three-dimensional PIV system to study the hydrodynamics of freely swimming Giant Danio (Danio aequipinnatus). Volumetric particle fields are reconstructed using synthetic aperture refocusing. The experiment is designed with minimal constraints on animal behavior to ensure that natural swimming occurs. Resultantly, the fish exhibits a variety of forward swimming and turning behaviors at speeds between 1.0-1.5 body-lengths/second. During these maneuvers, the imaging system is also used to track and reconstruct the fish body. The resultant velocity fields are used to characterize the size and shape of the vortex rings shed by the fish during forward swimming and turning. Results show clearly isolated and linked vortex rings in the wake structure, as well as the thrust jet coming off of a visual hull reconstruction of the fish body. Depending on the maneuver, the amount of symmetry in the wake varies, emphasizing the shortcomings of a single planar slice to characterize these behaviors. The additional information provided by volumetric measurement is also used to analyze the momentum in the fish's wake. The circulation of the vortex rings is computed across several slices of the ring taken through its center axis and analyzed over time. Circulation can be used to compute the fluid impulse in the vortex ring to better understand propulsive performance. The measured impulse, combined with visualization of the wake, provides a comparison between forward swimming and turning based on volumetric measurements. The development of this system lays a foundation for further volumetric studies of swimming hydrodynamics.
by Leah Rose Mendelson.
S.M.
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Alrished, Mohamad Ayad A. „A quantitative analysis and assessment of the performance of image quality metrics“. Thesis, Massachusetts Institute of Technology, 2020. https://hdl.handle.net/1721.1/128987.
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Thesis: S.M., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2020Cataloged from student-submitted PDF of thesis.
Includes bibliographical references (pages 79-82).
Image quality assessment addresses the distortion levels and the perceptual quality of a restored or corrupted image. A plethora of metrics has been developed to that end. The usual mean of success of an image quality metric is their ability to agree with the opinions of human subjects, often represented by the mean opinion score. Despite the promising performance of some image quality metrics in predicting the mean opinion score, several problems are still unaddressed. This thesis focuses on analyzing and assessing the performance of image quality metrics. To that end, this work proposes an objective assessment criterion and considers three indicators related to the metrics: (i) robustness to local distortions; (ii) consistency in their values'; and (iii) sensitivity to distortion parameters. In addition, the implementation procedures of the proposed indicators is presented. The thesis then analyzes and assesses several image quality metrics using the developed indicators for images corrupted with Gaussian noise. This work uses both widely-used public image datasets and self-designed controlled cases to measure the performance of IQMs. The results indicate that some image quality metrics are prone to poor performance depending on the number of features. In addition, the work shows that the consistency in IQMs' values depends on the distortion level. Finally, the results highlight the sensitivity of different metrics to the Gaussian noise parameter. The objective methodology in this thesis unlocks additional insights regarding the performance of IQMs. In addition to the subjective assessment, studying the properties of IQMs outlined in the framework helps in finding a metric suitable for specific applications.
by Mohamad Ayad A. Alrished.
S.M.
S.M. Massachusetts Institute of Technology, Department of Mechanical Engineering
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De, Maillé Austin (Austin C. ). „Finite Element Analysis on the skin properties affecting wound closure“. Thesis, Massachusetts Institute of Technology, 2017. http://hdl.handle.net/1721.1/112586.
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Thesis: S.B., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2017.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 32-33).
This thesis presents a Finite Element Analysis investigation on the properties of skin that affect skin wound closure and scar formation. It begins with an in depth literature review of mammalian studies and computer simulations of skin wounds, providing a better understanding of the mechanics of skin during wound healing. Details are then provided into the construction, simulation, and data processing of a finite element model in which wound shape, wound contraction forces, and subcutaneous tissue resistance are all varied. Two major conclusions can be drawn from these simulations. (1) When comparing rectangular, square, and circular wounds of the same initial wound size, rectangular wounds close fastest and circle wounds close slowest. (2) Subcutaneous tissue appears to be physically connected to the underlying dermis. Increased resistance/stiffness forces by subcutaneous tissue lead to less tissue contraction, however the relationship between skin deformation and subcutaneous resistance has not been determined. It appears that as skin displacement increases, subcutaneous tissue stiffness exponentially increases. Additional simulations must be completed to confirm this theory. Other factors affecting skin contraction, including skin thickness and Langer lines, have yet to be tested and should be pursued in future studies.
by Austin de Maillé.
S.B.
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Paton, Alan G. „The analysis of fatigue and mechanical properties of mooring tethers“. Thesis, University of Strathclyde, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.325444.
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Bow, Hansen Chang. „Microfluidic devices for analysis of red blood cell mechanical properties“. Thesis, Massachusetts Institute of Technology, 2010. http://hdl.handle.net/1721.1/60139.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2010.Cataloged PDF version of thesis.
Includes bibliographical references (p. 118-126).
Decreased deformability of human red blood cells (RBCs) is both a cause of disease and biomarker for disease (1). To traverse blood capillaries, the biconcave disk-shaped RBC must deform dramatically, since the diameter of the unconstrained RBC is larger than that of the capillaries. If the RBC becomes immobilized in a capillary, hypoxia and tissue injury may result, potentially leading to death. Changes in RBC deformability may be attributable to genetics (e.g. sickle cell anemia (2) and spherocytosis (3)), drug exposure (e.g. pentoxifylline (4)), and disease (e.g. diabetes (5) and malaria (6)). Within the past 15 years, microfabrication techniques have enabled the creation of pores comparable in size and shape to the smallest human capillaries (7) and slits in the spleen (8). We use this microfabrication ability to create devices that analyze and separate RBCs of different deformability. The first device we create is an automated 'deformability cytometer' that measures dynamic mechanical responses of 103~104 individual cells in a cell population. Fluorescence measurements of each cell are simultaneously acquired, resulting in a population-based correlation between biochemical properties (e.g. cell surface markers) and dynamic mechanical deformability. This device is especially applicable to heterogeneous cell populations, and we demonstrate its ability to mechanically characterize a small number of ring-stage malaria-infected RBCs in a large population of healthy RBCs. Next we present a device whose design is based on the architecture of the human spleen. This device is able to continuously separate more deformable from less deformable RBCs. We demonstrate the ability of this device to separate schizont-stage malaria-infected RBCs from healthy RBCs. Together, these devices enable the analysis and separation of single-RBCs based on deformability.
by Hansen Chang Bow.
Ph.D.
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Shah, Udit. „Mechanical Properties and Failure Analysis of Cellular Core Sandwich Panels“. Thesis, Virginia Tech, 2018. http://hdl.handle.net/10919/81699.
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Sandwich Panels with cellular cores are widely used in the aerospace industry for their higher stiffness to mass, strength to mass ratio, and excellent energy absorption capability. Even though, sandwich panels are considered state of the art for lightweight aerospace structures, the requirement to further reduce the mass exists due to the direct impact of mass on mission costs.
Traditional manufacturing techniques have limited the shape of the cores to be either hexagonal or rectangular, but, with rapid advancements in additive manufacturing, other core shapes can now be explored. This research aims to identify and evaluate the mechanical performance of two-dimensional cores having standard wall geometry, which provide higher specific stiffness than honeycomb cores. Triangular cores were identified to have higher specific in-plane moduli and equivalent specific out-of-plane and transverse shear moduli. To consider practical use of the triangular cores, elastic and elastic-plastic structural analysis was performed to evaluate the stiffness, strength, failure, and energy absorption characteristics of both the core and sandwich panels. The comparison made between triangular cores and hexagonal cores having the same cell size and relative density showed that triangular cores outperform hexagonal cores in elastic range and for applications where in-plane loading is dominant. Triangular cores also have excellent in-plane energy absorption capabilities at higher densities.Master of Science
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Johnson, Lindsay W. „The mechanical and microstructural analysis of the human cornea“. Diss., Georgia Institute of Technology, 1998. http://hdl.handle.net/1853/17065.
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Rummel, Nicholas J. „Dynamic mechanical analysis of magnetic tapes at ultra-low frequencies“. Scholarly Commons, 2011. https://scholarlycommons.pacific.edu/uop_etds/773.
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The purpose of this thesis is to investigate the correlated effects of temperature and frequency on the viscoelastic behavior of magnetic tapes, using a custom, ultra-low frequency, dynamic mechanical analyzer. The long-term mechanical and thermal properties of magnetic tapes can be simulated using high temperature and low frequency dynamic mechanical analysis (DMA) experiments. These experiments investigate how the viscoelastic characteristics of tape samples influence the extent to which the tape deforms. The experiments and analyses implemented in this paper examine the influence of the molecular structure on the viscoelasticity of magnetic tapes. Experiments were performed on a variety of magnetic tapes, including poly( ethylene terephthalatc) (PET), poly( ethylene naphthalate) (PEN), metallized poly( ethylene terephthalate) (MPET), and metallized Spaltan (M-SPA). To determine characteristic relating to the magnetic tape substrates, additional experiments examined PEN and PET substrates by removing the front and back magnetic layers from the tape sample. Due to the viscoelastic behavior of the tapes, a time delay was present between the strain and stress signals, which was determined using a Fourier transform program. The elastic modulus (E), storage modulus (E'), loss modulus (E"), and loss tangent (tan 8) were obtained from the time delay for each of the DMA experiments
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Guise, Sarah E. „Use of colour image analysis for assessment of fire damaged concrete“. Thesis, Aston University, 1997. http://publications.aston.ac.uk/13276/.
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The aim of this project was to carry out a fundamental study to assess the potential of colour image analysis for use in investigations of fire damaged concrete. This involved: (a) Quantification (rather than purely visual assessment) of colour change as an indicator of the thermal history of concrete. (b) Quantification of the nature and intensity of crack development as an indication of the thermal history of concrete, supporting and in addition to, colour change observations. (c) Further understanding of changes in the physical and chemical properties of aggregate and mortar matrix after heating. (d) An indication of the relationship between cracking and non-destructive methods of testing e.g. UPV or Schmidt hammer. Results showed that colour image analysis could be used to quantify the colour changes found when concrete is heated. Development of red colour coincided with significant reduction in compressive strength. Such measurements may be used to determine the thermal history of concrete by providing information regarding the temperature distribution that existed at the height of a fire. The actual colours observed depended on the types of cement and aggregate that were used to make the concrete. With some aggregates it may be more appropriate to only analyse the mortar matrix. Petrographic techniques may also be used to determine the nature and density of cracks developing at elevated temperatures and values of crack density correlate well with measurements of residual compressive strength. Small differences in crack density were observed with different cements and aggregates, although good correlations were always found with the residual compressive strength. Taken together these two techniques can provide further useful information for the evaluation of fire damaged concrete. This is especially so since petrographic analysis can also provide information on the quality of the original concrete such as cement content and water / cement ratio.
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Klintström, Eva. „Image Analysis for Trabecular Bone Properties on Cone-Beam CT Data“. Doctoral thesis, Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-142066.
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Trabecular bone structure as well as bone mineral density (BMD) have impact on the biomechanical competence of bone. In osteoporosis-related fractures, there have been shown to exist disconnections in the trabecular network as well as low bone mineral density. Imaging of bone parameters is therefore of importance in detecting osteoporosis. One available imaging device is cone-beam computed tomography (CBCT). This device is often used in pre-operative imaging of dental implants, for which the trabecular network also has great importance. Fourteen or 15 trabecular bone specimens from the radius were imaged for conducting this in vitro project. The imaging data from one dual-energy X-ray absorptiometry (DXA), two multi-slice computed tomography (MSCT), one high-resolution peripheral quantitative computed tomography (HR-pQCT) and four CBCT devices were segmented using an in-house developed code based on homogeneity thresholding. Seven trabecular microarchitecture parameters, as well as two trabecular bone stiffness parameters, were computed from the segmented data. Measurements from micro-computed tomography (micro-CT) data of the same bone specimens were regarded as gold standard. Correlations between MSCT and micro-CT data showed great variations, depending on device, imaging parameters and between the bone parameters. Only the bone-volume fraction (BV/TV) parameter was stable with strong correlations. Regarding both HR-pQCT and CBCT, the correlations to micro-CT were strong for bone structure parameters as well as bone stiffness parameters. The CBCT device 3D Accuitomo showed the strongest correlations, but overestimated BV/TV more than three times compared to micro-CT. The imaging protocol most often used in clinical imaging practice at our clinic demonstrated strong correlations as well as low radiation dose. CBCT data of trabecular bone can be used for analysing trabecular bone properties, like bone microstructure and bone biomechanics, showing strong correlations to the reference method of micro-CT. The results depend on choice of CBCT device as well as segmentation method used. The in-house developed code based on homogeneity thresholding is appropriate for CBCT data. The overestimations of BV/TV must be considered when estimating bone properties in future clinical dental implant and osteoporosis research.
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Choudhury, Udit. „Dynamic Mechanical Properties of Cockroach(Periplaneta americana) Resilin“. Thesis, Virginia Tech, 2012. http://hdl.handle.net/10919/40869.
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Resilin is a cuticular protein found in a variety of insects. It can stretch up to 300% of its natural length without any creep or relaxation. Further, it operates across a wide frequency range from 5 Hz in locomotion to 13 kHz in sound production. Both the protein sequence and composition of natural resilin as well as the dynamic mechanical properties vary substantially across species. This suggests that mechanical properties may be evolutionarily tuned for specific functions within an insect. Here, samples of resilin obtained from the tibia-tarsal joint of the cockroach, Periplaneta americana, were tested using a custom built dynamic mechanical analyzer. The material properties in compression are obtained from the rubbery to glassy domain with time-temperature superposition (-2C to 55C) and time-concentration superposition (0 % to 93% ethanol by volume in water). At low frequency the storage modulus was found to be 1.5 MPa increasing to about 5 MPa in the transition zone. The glass transition frequency at 23C in complete hydration was found to be 200 kHz. The data shows that cockroach resilin is less resilient than dragonfly resilin at low frequencies, returning about 79% of the elastic strain energy at 25 Hz compared to 97% for dragonfly resilin. However, at the glass transition (200 kHz) the material returns about 47% of the elastic strain energy compared to 30% in dragonfly (2MHz ). The resilin pad in cockroach is a composite structure, acting as a compressive spring to passively extend the tibia-tarsal joint during cockroach locomotion. Its mechanical properties are more similar to the composite locust pre-alar arm than to the pure resilin dragonfly tendon, suggesting that macroscopic structural influences may be as important as molecular sequence differences in setting properties.Master of Science
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Hatami, Mohammad. „Multiscale Analysis of Mechanical and Transport Properties in Shale Gas Reservoirs“. Ohio University / OhioLINK, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1614950615095796.
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Grullon, Varela Rodolfo Antonio. „Particle Image Velocimetry Sensitivity Analysis Using Automatic Differentiation“. Thesis, University of North Texas, 2016. https://digital.library.unt.edu/ark:/67531/metadc955037/.
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A particle image velocimetry (PIV) computer software is analyzed in this work by applying automatic differentiation on it. We create two artificial images that contained particles that where moved with a known velocity field over time. These artificial images were created with parameters that we would have on real PIV experiments. Then we applied a PIV software to find the velocity output vectors. As we mentioned before, we applied automatic differentiation through all the algorithm to track the derivatives of the output vectors regarding interesting parameters declared as inputs. By analyzing these derivatives we analyze the sensitivity of the output vectors to changes on each one of the parameters analyzed. One of the most important derivatives calculated in this project was the derivative of the output regarding the image intensity. In future work we plan to use this derivative combined with the intensity probability distribution of each image pixel, to find PIV uncertainties. If we achieve this goal we will find an uncertainty method that will save computational power and will give uncertainty values with computer accuracy.
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Haupt, Brandon Levi. „Design and Analysis of a Positively Engaged Continuously Variable Transmission“. Diss., CLICK HERE for online access, 2008. http://contentdm.lib.byu.edu/ETD/image/etd2635.pdf.
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Morgan, David Scott. „A microstructural and mechanical analysis of perforation of aluminum alloys“. Thesis, Georgia Institute of Technology, 1992. http://hdl.handle.net/1853/16361.
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Fang, Zhibin Sun Wei. „Image-guided modeling, fabrication and micromechanical analysis of bone and heterogeneous structure /“. Philadelphia, Pa. : Drexel University, 2005. http://dspace.library.drexel.edu/handle/1860/549.
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Sterling, Colin J. „Effects of Friction Stir Processing on the Microstructure and Mechanical Properties of Fusion Welded 304L Stainless Steel“. Diss., CLICK HERE for online access, 2004. http://contentdm.lib.byu.edu/ETD/image/etd440.pdf.
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Neve, de Mevergnies Nathalie. „The MicroPIVOT : an Integrated Particle Image Velocimeter and Optical Tweezers Instrument for Microscale Investigations“. PDXScholar, 2010. https://pdxscholar.library.pdx.edu/open_access_etds/31.
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This dissertation describes the development of a device capable of suspending a microscale object in a controlled flow. The uPIVOT is a system integrating two laser-based techniques: micron particle image velocimetry (uPIV) and optical tweezers (OT). The OT allows the suspension and manipulation of micron-sized objects such as microspheres or biological cells. uPIV provides imaging of the suspended object and velocity measurements from which fluid induced stresses can be determined. Using this device, we measured fluid velocities around an optically suspended polystyrene microsphere (an experimental first) and studied the interaction between two particles suspended in a uniform flow. The results were consistent with theoretical low Reynolds number, Newtonian flow predictions. Additionally, we analyzed a single cell's mechanical response to a controlled and measurable multiaxial external force (fluid flow) without the cell being physically attached to a surface. The cell's mechanical response was monitored by observing its morphology and measuring its deformation. The results show significant deformations of optically suspended cells at substantially smaller stresses than previously reported and demonstrate the opportunity to optically distinguish a cell by its trapping efficiency. These initial applications of the uPIVOT demonstrate the potential of this unique device as a research tool for novel studies in the fields of fluid/particle(s) interactions, non-Newtonian fluid mechanics, and single cell biomechanics.
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Pasupuleti, Ajay. „Analysis of effective mechanical properties of thin films used in microelectromechanical systems /“. Online version of thesis, 2007. http://hdl.handle.net/1850/5283.
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Bayliss, Roger W. „The sintering, microstructural analysis and mechanical properties of two β' MgSiAlON ceramics“. Thesis, University of Warwick, 1986. http://wrap.warwick.ac.uk/2823/.
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This work describes the preparation and the determination of some properties of two magnesium SiAlON ceramics, one with a low substitution level and one with a high substitution level ' phase. Each had a specific amount of spinel as second phase which would form on sintering or after a post-sintering heat-treatment. The work was undertaken because (a) the improvement in the properties of pressureless-sintered yttrium SiAlON ceramics was not as high as anticipated and (b) by applying the knowledge gained with the widely researched yttrium system to the MgSiAlON ceramic system, the properties of the magnesium system may be further improved. Under consideration in this thesis were the sintering of these ceramics and some sintering reactions are proposed. Also discussed is the effect on the microstructure of heating the ceramic in both oxidising and inert atmospheres. Some mechanical properties were determined, including fracture toughness and hardness testing at ambient temperature, and creep testing at upto 1300^oC. It was expected that MgSiAlONs would be easier to sinter due to the lower ternary oxide eutectic temperature and from a sintering view-point the high z materials do offer an alternative system to the yttrium system by being easier to sinter, but the low z material was as difficult to sinter as the yttrium system. Whilst the MgSiAlONs that were produced in this project were generally out-performed, encouraging results were obtained for the high z material in oxidation resistance. Low z material had the highest fracture toughness and hardness - both of which increased by heat-treatment. It is proposed that alterations to this heat-treatment would improve matters and would form a useful area for future work.