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Dissertations / Theses on the topic 'Elastic properties'
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Hornby, Brian E. "The elastic properties of shales." Thesis, University of Cambridge, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.296669.
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Dunk, Alan. "Elastic properties of triglycine sulphate." Thesis, University of Bath, 1987. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.376297.
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Paine, A. C. "Elastic properties of granular materials." Thesis, University of Bath, 1998. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.245957.
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Harrington, Jonathan J. "Hierarchical modelling of softwood hygro-elastic properties." Thesis, University of Canterbury. Mechanical Engineering, 2002. http://hdl.handle.net/10092/8061.
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The hygro-elastic behaviour of wood under load or when subjected to environmental changes is of considerable practical interest. This behaviour can be determined by exhaustive experimentation, but such an approach makes explaining its origin, which from some perspectives can be more important than its prediction, problematic. This thesis attempts to establish a model (actually a hierarchical set of models) that goes some way toward both predicting and explaining the mechanics of wood. Attention is focused on radiata pine because of the commercial importance of this species in New
Zealand, but much of the modelling is applicable to other softwoods and, to a lesser extent, hardwoods.
Wood can be looked on as a hierarchical material, that is as a material possessing structure at multiple scales. For many problems involving such materials the heterogeneous structure at a particular scale can be replaced by a homogeneous one possessing similar properties. Homogenization theory defines what is meant by similar and also provides the means for determining these effective properties.
In this thesis wood structure is treated at three different scales: namely the supramolecular or nanostructural, the cell-wall or ultrastructural and the cellular or microstructural scales. Homogenization across these levels is performed either analytically or numerically, using the finite element method.
At the smallest scale, the constituent phases are treated as homogeneous continua.
Models for the hygro-elastic phase properties, as functions of temperature and moisture content are developed based on available experimental data.
The models devised to describe wood at each of the above mentioned scales introduce a large number of structural parameters, such as constituent mass fractions and cell-wall layer volume fractions. In the abscence of specific data, estimates for these parameters are developed based on data from the literature. Together with these auxiliary models, the main sequence of structural models can then be used to obtain estimates for the material properties of small domains within macrostuctural models.
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Han, Tongcheng. "Joint elastic-electrical properties of reservoir sandstones." Thesis, University of Southampton, 2010. https://eprints.soton.ac.uk/195017/.
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Over the last decade, marine controlled source electromagnetic (CSEM), sub-seabed imaging has developed to a state where routine resistivity mapping of hydrocarbon reservoirs is now possible. Co-located marine seismic and electrical resistivity survey data could provide the engineering parameters needed to better assess the economic potential of hydrocarbon reservoirs without the need for drilling, and could provide additional reservoir monitoring capabilities in the future. However, proper exploitation of joint seismic-CSEM datasets will require a much better understanding of the inter-relationships among geophysical (elastic and electrical) and reservoir engineering properties. This project seeks to study the inter-relationships among the elastic and electrical properties of typical reservoir sandstones for improved insight into wave propagation phenomena in porous rocks. A high quality joint elastic-electrical dataset has been collected on a set of 67 sandstone samples showing a range of porosities, permeabilities and clay contents. The measurements were simultaneously carried out at differential pressures up to 60 MPa. Elastic properties (compressional and shear wave velocity and attenuation) were measured using a pulse-echo technique; electrical resistivity was recorded at AC frequency of 2 Hz using a circumference resistivity measurement method. The effects of porosity, permeability, clay content and differential pressure on the low frequency (2 Hz) electrical resistivity properties and the influence of differential pressure and petrophysical parameters on the joint elastic-electrical properties of reservoir sandstones were analyzed. A three-phase (quartz, brine and pore-filling clay) effective medium model based on self-consistent approximation (SCA) and differential effective medium (DEM) for the joint elastic-electrical properties of reservoir sandstones was developed and was found to give a good description of the experimental observations.
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Chatterjee, Sudipta. "Tribological properties of pseudo-elastic nickel-titanium." Diss., Restricted to subscribing institutions, 2008. http://proquest.umi.com/pqdweb?did=1610048621&sid=1&Fmt=2&clientId=1564&RQT=309&VName=PQD.
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Bastos, de Paula Osni. "Elastic properties of carbonates : measurements and modelling." Thesis, Curtin University, 2011. http://hdl.handle.net/20.500.11937/1417.
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This thesis is a multi-scale study of carbonate rocks, from the nanoscale and digital rock investigations to the imaging studies of carbonate reservoir analogues. The essential links between these extremes are the carbonate physical properties and rock-physics models, which are investigated here through the modelling of ultrasonic wave propagation in carbonate samples, focusing on elastic stress sensitivities, saturating fluids and porosity models. Validation of Gassmann fluid substitution in carbonates is also investigated using correlations between core and well log measurements.On the nanoscale, we use the nanoindentation technique in an oolitic limestone to directly measure the calcite Young modulus and derive bulk and shear moduli. We have found a large variation in the calcite bulk modulus, from 56 to 144 GPa. The high values obtained in some oolite rings were interpreted as genetically associated with biologically generated calcite (biocalcite). There are many measurements that achieve these values in brachiopod shells, but none in oolitic limestone. We associate the smaller values with microporosity, which is undetectable by our microCT or even SEM images. On the microscale we use the X-ray microCT images. From these images we can compute oolite elastic parameters using finite difference methods (FDM). In this oolite sample, calcite was segmented in two distinct phases. Nanoindentation provides the elastic parameters for each phase. The results of the modelling are compared with ultrasonic measurements on dry samples.To compute the properties of rocks on fluid-saturated samples, one needs to use fluid substitution methods, such as Gassmann’s equations. However, the applicability of Gassmann’s equations and the fluid substitution technique to carbonate rocks is still a subject of debate. Here we compare the results of fluid substitution applied to dry core measurements against sonic log data. The 36 meters of continuously sampled carbonates data, comes from a cretaceous reservoir buried at a depth of 5000 metres in the Santos Basin, offshore Brazil. Compressional and shear velocities, density and porosity were measured in 50 samples covering the entire interval. We obtain good agreement between the elastic properties obtained from core and log measurements. This shows that Gassmann’s fluid substitution is applicable to these carbonates, at least at sonic log frequencies.Carbonate microstructure is investigated using the stress dependency of shear and compressional wave velocities according to the dual porosity model of Shapiro (2003). The model assumes that the pore space contains two types of pores: stiff and compliant pores. Understanding the parameters of this model for different rocks is important for constraining stress effects in these rocks. The results for a carbonate dataset from the Santos Basin show a good correlation between compliant porosity and dry bulk modulus, total porosity and density for 29 samples of carbonates from the Santos Basin. The correlations seem to be different for different facies distribution, with different trends for mudstone facies and grainstone and rudstone facies. We also performed the same analysis using 66 samples of sandstones of diverse origins (Han et al., 1986): a good correlation appears between compliant porosity and the dry bulk modulus for all samples.If we correlate only the 7 samples from Fontainebleau sandstone, a good correlation also appears between total and compliant porosity. This analysis shows that the correlation is facies dependent also for sandstones.While Gassmann’s equations may be valid for low frequencies, they are not applicable at higher frequencies, where squirt dispersion is significant. We propose a workflow to model wave dispersion and attenuation due to the squirt flow using the geometrical parameters of the pore space derived from the stress dependency of elastic moduli on dry samples. Our analysis shows the dispersion is controlled by the squirt flow between equant pores and intermediate pores (with aspect ratios between 10-3 - 2·10-1). Such intermediate porosity is expected to close at confining pressures of between 200-2000 MPa. We also infer the magnitude of the intermediate porosity and its characteristic aspect ratio. Substituting these parameters into the squirt model, we have computed elastic moduli and velocities of the water-saturated rock and compared these predictions against laboratory measurements of these velocities.The agreement is good for a number of clean sandstones, but much worse for a broad range of shaley sandstones. Our predictions show that dispersion and attenuation caused by the squirt flow between compliant and stiff pores may occur in the seismic frequency band. Confirmation of this prediction requires laboratory measurements of elastic properties at these frequencies.The carbonate system of Telegraph Station, Shark Bay (WA), is a unique environment where coquinas, stromatolites and microbial mats are linked: an excellent analogue to carbonate pre-salt offshore Brazil. We acquired 7.5 km of GPR data and high resolution seismic data in the coquina ridges. They are composed by calcite shells deposited by cyclones, which show excellent high resolution GPR images, being a low loss dielectric medium. Three classes of coquinas were mapped: tabular layers, convex-up crest and washover fan. From the correlation of 14C dating of 50 samples and the mapped events we can estimate an average rate of one event every 13 years. From our interpretation the Holocene regression is continuous but not homogeneous. Carbonate dissolution features, faults, trends and discontinuities were mapped. Analysis of these features helps us understand reservoir porosity and permeability distribution in carbonate deposits, and can be used to constrain reservoir properties in pre-salt carbonates in Brazilian basins.
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Ortolani, Matteo. "Elastic Properties of Textured Nanocrystalline Thin Films." Doctoral thesis, Università degli studi di Trento, 2011. https://hdl.handle.net/11572/367871.
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Polycrystalline thin films and coatings often show preferred orientation of grains and crystalline domains, and develop a residual stress state as an effect of the growth mechanisms. These features can be conveniently measured by means of non-contact and non-destructive X-ray diffraction. As the technique only measures a map of strains along selected directions, stress evaluation requires a suitable constitutive equation, where the expression of moduli can be far from trivial if texture effects are to be taken into account; additionally, a grain interaction model needs to be enforced to describe strain and stress distribution among grains in the aggregate, based on background assumptions.
Several grain interaction models are available from literature: usually, a model or a combination of them provides a good fit of experimental data; often however underlying hypotheses are too restrictive or require unavailable information on certain microstructural parameters, leading this approach to fail. For this reason an experimental method was developed, for the characterisation of elastic properties and residual stress in thin film components by means of X-ray diffraction during in-situ mechanical testing.
This thesis presents a review of major literature works describing grain interaction modelling in textured components, and their implementation in X-ray diffraction stress analysis procedures. Following, the method for experimental characterisation of thin film elastic properties is described in detail. Applications are presented in the final chapter, that illustrates selected case studies on electrodeposited coatings.
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Ortolani, Matteo. "Elastic Properties of Textured Nanocrystalline Thin Films." Doctoral thesis, University of Trento, 2011. http://eprints-phd.biblio.unitn.it/682/1/tesi_dottorato.pdf.
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Polycrystalline thin films and coatings often show preferred orientation of grains and crystalline domains, and develop a residual stress state as an effect of the growth mechanisms. These features can be conveniently measured by means of non-contact and non-destructive X-ray diffraction. As the technique only measures a map of strains along selected directions, stress evaluation requires a suitable constitutive equation, where the expression of moduli can be far from trivial if texture effects are to be taken into account; additionally, a grain interaction model needs to be enforced to describe strain and stress distribution among grains in the aggregate, based on background assumptions.
Several grain interaction models are available from literature: usually, a model or a combination of them provides a good fit of experimental data; often however underlying hypotheses are too restrictive or require unavailable information on certain microstructural parameters, leading this approach to fail. For this reason an experimental method was developed, for the characterisation of elastic properties and residual stress in thin film components by means of X-ray diffraction during in-situ mechanical testing.
This thesis presents a review of major literature works describing grain interaction modelling in textured components, and their implementation in X-ray diffraction stress analysis procedures. Following, the method for experimental characterisation of thin film elastic properties is described in detail. Applications are presented in the final chapter, that illustrates selected case studies on electrodeposited coatings.
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Topol, Heiko [Verfasser]. "Acoustic and mechanical properties of viscoelastic, linear elastic, and nonlinear elastic composites / Heiko Topol." Aachen : Hochschulbibliothek der Rheinisch-Westfälischen Technischen Hochschule Aachen, 2012. http://d-nb.info/1028213352/34.
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Mergell, Boris. "Structural and elastic properties of DNA and chromatin." [S.l. : s.n.], 2003. http://deposit.ddb.de/cgi-bin/dokserv?idn=96993775X.
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Ragauskas, Paulius. "Identification Of Elastic Properties Of Layered Composite Materials." Doctoral thesis, Lithuanian Academic Libraries Network (LABT), 2010. http://vddb.laba.lt/obj/LT-eLABa-0001:E.02~2010~D_20101119_134738-62490.
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In this thesis the problems of identification accuracy of elastic properties of materials are examined. The main object of study is samples of various materials and their elastic properties. This is an important subject of theoretical studies of various materials. The main thesis objective is to create an effective technology for precise identification of all the elastic characteristics of the sample. The de-veloped algorithms are to be applied in the material manufacturing industry. Thesis also aims at exploring accuracy and sensitivity of the identification of elastic properties of materials.
The paper deals with a number of objectives: 1) to optimize the geometric parameters of the sample striving for more accurate identification results of elas-tic properties; 2) to identify mode shapes of sample and regulate their place in spectrum of eigenvalues in order to minimize the distortion of the objective function; 3) to create the implementation algorithms of proposed technologies and verify their capabilities experimentally. The first task is formulated taking into account the relatively high level of identification error of elastic properties of composite materials. The second objective relates to distortion of the objec-tive function in the process of updating the mathematical model with the pre-sumed elastic characteristics of material.
The thesis is composed of four chapters, the summary of results, the list of literature and the list of author’s publications on the topic... [to full text]Disertacijoje nagrinėjamos medžiagų tamprumo rodiklių identifikavimo tikslumo problemos. Pagrindinis tyrimo objektas yra įvairių medžiagų bandiniai, jų tamprumo rodikliai. Šis objektas yra svarbus įvairių medžiagų teoriniams tyrimams. Pagrindinis disertacijos tikslas yra sukurti efektyvią technologiją, leidžiančią pakankamu tikslumu surasti visus bandinio tamprumo rodiklius. Sukurtų algoritmų taikymo sritis yra medžiagų gamybos pramonė. Disertacijoje tiriamas siūlomos technologijos tikslumas ieškant įvairių medžiagų tamprumo rodiklių. Darbe sprendžiami keli pagrindiniai uždaviniai: optimizuojami bandinio geometriniai parametrai siekiant tikslesnių tamprumo rodiklių identifikavimo rezultatų; atpažįstamos bandinio modų formos ir reguliuojama jų vieta tikrinių reikšmių spektre siekiant sumažinti tikslo funkcijos iškraipymus; sukuriami pasiūlytų technologijų įgyvendinimo algoritmai ir bandymais patikrinamos jų galimybės. Pirmasis uždavinys suformuluotas atsižvelgiant į palyginti didelę kompozitinių medžiagų tamprumo rodiklių identifikavimo paklaidą. Antrasis siejasi su tikslo funkcijos iškraipymu atnaujinant matematinį medžiagos modelį spėjamais tamprumo rodikliais. Disertaciją sudaro keturi skyriai, rezultatų apibendrinimas, naudotos literatūros ir autoriaus publikacijų disertacijos tema sąrašai. Įvadiniame skyriuje aptariamas problemos aktualumas, tyrimo objektas, formuluojamas darbo tikslas bei uždaviniai, aprašoma tyrimų metodika, darbo mokslinis naujumas, darbo rezultatų... [toliau žr. visą tekstą]
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Marquardt, Hauke [Verfasser]. "Single-crystal elastic properties of geomaterials / Hauke Marquardt." Berlin : Freie Universität Berlin, 2009. http://d-nb.info/1023665158/34.
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Andrea, Martijn. "The anisotropic elastic properties of clay-rich rocks." Thesis, Imperial College London, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.243413.
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Strömer, Jan. "Elastic properties of nematic and cholesteric liquid crystals." Thesis, University of Oxford, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.410665.
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Swift, Mark Jonathan. "Acoustic and Physical Properties of Poro-Elastic Media." Thesis, University of Bradford, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.520232.
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Jones, G. W. "Static Elastic Properties of Composite Materials Containing Microspheres." Thesis, University of Oxford, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.487266.
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This thesis aims to model the uniaxial deformation of a class of materials consisting of microscopic spherical shells embedded in a rubber matrix. These shells are assumed to buckle as the stress on the material increases. To motivate the analysis we consider the paradigm problem of the debonding of a distribution of cylindrical inclusions in an elastic material undergoing antiplane shear, with bonded and debonded inclusions playing the role of unbuckled and buckled shells respectively. We begin the modelling of the microsphere-containing material by considering the buckling of an isolated embedded shell inclusion with a uniaxial stress field at infinity, using Koiter's theory of shallow shells. The resulting energy functional is solved as an eigenvalue problem by the Rayleigh-Ritz method. Subsequently, we analyse the buckling criterion asymptotically in the limit as the thickness ratio tends to zero by analogy with the WKB analysis of a beam on a variable-stiffness substrate. To model the shell after buckling we consider the simplified case of an embedded shell with a crack around its equator. The system is solved by expressing the displacements in the shell and matrix as series of Love stress functions, with the resulting infinite system of equations solved numerically with the aid of a convergence acceleration method. Finally we consider a composite material consisting of a homogenised dilute distribution of buckled and unbuckled shells, with the proportion of each type of shell dependent on the stress applied to the material, according to an asymptotic formula relating the size of the inclusions and the critical buckling stress that was obtained previously.
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Zrida, Hana. "Composites with bundle mesostructure: Elastic properties and Damage." Doctoral thesis, Luleå tekniska universitet, Materialvetenskap, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-25761.
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Many types of composite materials are today used in various types of load carrying structures, due to their excellent strength and stiffness to weight ratio. Simplicity, reliability and low cost of the material processing are important factors affecting the final selection.With the textile reinforced composites, the cost-efficiency is reached by using dry preforms which are impregnated by resin infusion, resin transfer molding etc.; this have made a break-through and have been widely used. Textile composites with bundle meso-structure have been studied in this thesis for elastic properties and damage investigations. The first part of this thesis deals with elastic properties modeling for Non-crimp fabric (NCF) based composites for investigating the effect of meso-structure defects on mechanical properties degradation. The objective of the work is to formulate a model for the NCF composite mesostructure in an attempt to investigate the effect of the waviness on stiffness reduction. Moreover, the stiffness calculation methods for the complex geometry are explained and justified and finally, the different geometrical parameters changes are taken into consideration and included in the calculation.The damage initiation and development is presented is the second part, where woven fabric composites designated for high temperature application were investigated under severe thermal conditions to study their thermal stability and their resistance to thermal damage. The mechanical performance of the same composites was studied. The effect of aging was also investigated. 3D models were realized with Finite elements in order to explain the edge effect on the evolution of the cracks observed during the tensile tests. In addition, the differences and similarities in cracking in different layers were analysed using probabilistic approaches (a simple one as well as Monte Carlo simulations with Hashin’s and also shear lag model) and fracture mechanics arguments.Godkänd; 2016; 20160419 (hanzri); Nedanstående person kommer att disputera för avläggande av teknologie doktorsexamen. Namn: Hana Zrida Ammar Ämne: Polymera konstruktionsmaterial/Polymeric Composite Material Avhandling: Composites with Bundle Mesostructure: Elastic Properties and Damage Opponent: Professor Stephen L Ogin, Dept of Mechanical Engineering Sciences, Faculty of Engineering and Physical Sciences Materials Surface and Structural Systems, University of Surrey, Surrey, UK. Ordförande: Professor Janis Varna, Avdelningen för materialvetenskap, Institutionen för teknikvetenskap och matematik, Luleå tekniska universitet, Luleå. Tid: Måndag 30 maj, 2016 kl 10.00 Plats: E231, Luleå tekniska universitet
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Olsen, Casper. "Elastic and electric properties of North Sea chalk." Kgs. Lyngby : Institute of Environment & Resources, Technical University of Denmark, 2007. http://www.er.dtu.dk/publications/fulltext/2007/MR2007-123.pdf.
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Liu, Huijin. "The elastic and dielectric properties of structural ceramics." Thesis, University of Bath, 1999. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.285312.
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Alzubi, Feras G. "Atomistic modeling of elastic and transport properties of carbon nanotubes." Virtual Press, 2008. http://liblink.bsu.edu/uhtbin/catkey/1398706.
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A first principles atomistic calculation and analysis is used to conduct studies on the mechanical and electron transport properties of selected stretched single-wall carbon nanotube segments. The atomic forces, electron densities, current, voltage and total energies are calculated for these carbon nanotube segments using Atomistix's Virtual NanoLab (VNL) and ToolKit (ATK), a software package for electronic structure calculations and molecular dynamics simulations of different molecular systems. Plots of electronic energy spectra, densities of states, force versus length, and current-voltage data, are presented as output results. The mechanical properties of these carbon nanotube segments under a maximum strain of 1% are studied.A speculative atomistic-level stress-strain approach is tried for calculating Young's modulus for a single-wall carbon nanotube segment. The computed total energies are also used to extract the Young's modulus value. Based on the results, the approach is found to work and we were able to calculate the mechanical parameters for single-wall carbon nanotube segments. The electrical conductance is obtained from the current-voltage curves for strained single-wall metallic carbon nanotube segments placed between copper contacts.Department of Physics and Astronomy
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Andrews, Gordon Todd. "Elastic and structural properties of supported porous silicon layers." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape9/PQDD_0004/NQ42470.pdf.
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Masouras, Konstantinos. "Elastic and surface properties of model nanofilled resin-composites." Thesis, University of Manchester, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.509838.
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Liu, Harry. "Elastic properties and phases of bent core liquid crystal." Thesis, University of Manchester, 2016. https://www.research.manchester.ac.uk/portal/en/theses/elastic-properties-and-phases-of-bent-core-liquid-crystal(1428e685-754c-42c0-890b-9ae83f0b5f7c).html.
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The recent interest in bent core liquid crystal has shown many unique physical properties, such the anomalous behaviour of the elastic constants (SplayK1, Twist K2, and BendK3). In bent core liquid crystals it is observed that K3K1). Such behaviour is analogous to calamitic liquid crystals but is in contrast to all other bent-core nematic materials reported to date. Such a result questions some of the current explanations for the elastic behaviour of bent-core materials. Using molecular field theory and atomistic modelling the different elastic behaviour predicted is again in excellent agreement with experimental results. The bend angle is again shown to be an important part in determining the physical properties of bent-core nematic liquid crystals. In a mixture from an oxadiazole dopant and calamitic host liquid crystal, it was found that a filament structure appears in the nematic phase. The filaments appear to interfere with the measurements for elastic constants. In order to understand the filament structure many methods were used including SAXS, dielectric permittivity, and DSC. It was found that the mixture had formed a gel - like phase. The gel is composed of a liquid crystal network and a liquid crystal background, not seen before in any gel system. Due to the liquid crystalline properties both the network and the background can be aligned and manipulated. The new gel phase can possess many new unique properties which warrant further studies understand further into how fundamentally the phase is forming.
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Tsarouchas, Dimitris. "Fibre network materials : architecture and effective linear elastic properties." Thesis, University of Cambridge, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.610878.
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Tian, Liyun. "Density Functional Study of Elastic Properties of Metallic Alloys." Licentiate thesis, KTH, Tillämpad materialfysik, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-179336.
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Special quasi-random structure (SQS) and coherent potential approximation (CPA) are techniques widely employed in the first-principles calculations of random alloys. The aim of the thesis is to study these approaches by focusing on the local lattice distortion (LLD) and the crystal symmetry effects. We compare the elastic parameters obtained from SQS and CPA calculations. For the CPA and SQS calculations, we employ the Exact Muffin-Tin Orbitals (EMTO) method and the pseudopotential method as implemented in the Vienna Ab initio Simulation Package (VASP), respectively. We compare the predicted trends of the VASP-SQS and EMTO-CPA parameters against composition. As a first case study, we investigate the elastic parameters of face centered cubic (fcc) Ti1−xAlx(0≤x≤100at.%) random solid solutions as a function of Al content (x). The EMTO-CPA and VASP-SQS results are in good agreement with each other. Comparing the lattice constants from SQS calculations with and without local lattice relaxations, we find that in Ti-rich (Al-rich) side the lattice constants remain almost unchanged (slightly increase) upon atomic relaxations. Taking local lattice distortions into consideration decreases the C11 and C44 elastic parameters, but their trends are not significantly affected. The C12 elastic constant, on the other hand, is almost unchanged when atomic relaxations are included. In general, the uncertainties in the elastic parameters associated with the symmetry lowering in supercell studies turn out to be superior to the differences between the two alloy techniques including the effect of LLD. We also investigate the elastic properties of random fcc Cu1−xAux(0≤x≤100 at.%) alloys as a function of Au content employing the CPA and SQS approaches. It is found that the CPA and SQS values forC11andC12 are consistent with each other no matter whether the atomic relaxations are taken into account or not. On the other hand, the EMTO-CPA values for C44 are slightly larger than those from SQS calculations especially for Cu-rich alloys which we ascribe to the differences in the DFT solvers rather than the differences between CPA and SQS. The Perdew-Burke-Ernzerhof (PBE) approximation to the exchange-correlation term in density functional theory (DFT) is a mature approach and have been adopted routinely to investigate the properties of metallic alloys. In most of the cases, PBE provides theoretical results in good agreement with experiments. However, the ordered Cu-Au system turned out to be a special case where large deviations between the PBE predictions and observations occur. In this work, we make use of a recently developed exchange-correlation functional, the so-called quasi-non-uniform exchange-correlation approximation (QNA), to calculate the lattice constants and formation energies for ordered Cu-Au alloys as a function of composition. The calculations are performed using the EMTO method. We find that the QNA functional leads to excellent agreement betweent heory and experiment. The PBE strongly overestimates the lattice constants for ordered Cu3Au, CuAu, CuAu3 compounds and also for the pure metals which is nicely corrected by the QNA approach. The errors in the formation energies of Cu3Au, CuAu, CuAu3relative to the experimental data decrease from 38-45% obtained with PBE to 5-9% calculated for QNA.QC 20151216
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Duffy, Thomas S. Ahrens T. J. Ahrens T. J. "Elastic properties of metals and minerals under shock compression /." Diss., Pasadena, Calif. : California Institute of Technology, 1992. http://resolver.caltech.edu/CaltechETD:etd-05172007-104609.
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Ruiz, Penã Franklin J. (Franklin José) 1962. "Elastic properties of sedimentary anisotropic rocks : (measurements and applications)." Thesis, Massachusetts Institute of Technology, 1998. http://hdl.handle.net/1721.1/58361.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, February 1999.Includes bibliographical references (leaves 75-78).
In multidisciplinary studies carried out in the Budare Oil Field of the Great Oficina Oil Field, there was difficulty matching well log synthetic seismograms with 2D and 3D seismic data. In addition, the seismically determined depths of reservoir horizons are greater than the well sonic log depths. To examine this discrepancy we conducted an experimental study of dynamic elastic parameters of the rocks in the oil field. We chose core representative samples of the lower Oficina Formation, the main reservoir of the field. The rocks selected were sandstones, sandy shales and dolomitized shales. For the velocity measurements, we used the ultrasonic transmission method to measure P-, Sh- and Sv-wave travel times as a function of orientation, and pore and confining pressures to 60 and 65 MPa, respectively. We found that, in room dry condition, most of the rocks studied are transversely isotropic. The stiffnesses constants, Young's moduli, Poisson's ratios, and bulk moduli of these rocks, were also calculated. The velocity anisotropies, together with the behavior of the elastic constants for dry rocks, indicate that: (1) the elastic anisotropy of the sandstones and sandy shales is due to the combined effects of pores, cracks, mineral grain orientation, lamination and foliation. The velocity anisotropies caused by the preferred oriented cracks decrease with increasing confining pressure. (2) For the dolomitized shales, the elastic anisotropy is due to mineral orientation and microlamination. In these cases the very high intrinsic anisotropy does not decrease with increasing confining pressure. (3) The velocities of compressional waves are greater in sandstones saturated with water than in the dry specimens, but the opposite behavior was found for shear waves. (4) The P-wave velocity anisotropy decreases after saturation; the magnitude of the decrease depends on the crack density and on the abundance and distribution of clay. (5) The Vsh-anisotropy does not show a pronounced change after saturation, and it is only slightly affected by confining pressure. Visual description, petrography and mineralogical analyses from thin sections and x-ray diffraction revealed the vertical and lateral heterogeneous nature of sandstones and sandy shales, whereas the dolomitized shale specimens looked homogeneous. The results of the laboratory measurements are consistent with an elastic model, using the equivalent medium theory for fine-layered isotropic and anisotropic media. However, in order to do reliable seismic migration and solve the problem of thickness calculations and time-to-depth conversion of surface seismic data, the ultrasonic data need to be extrapolated to low frequencies. Determining rock mechanical properties in situ is important in many applications in the oil industry such as reservoir production, hydraulic fracturing, estimation of recoverable reserves, and subsidence. Direct measurement of mechanical properties in situ is difficult. Nevertheless, experimental methods exist to obtain these properties, such as measurements of the stress-strain relationships (static) and elastic wave velocities (dynamic). We investigate the static and dynamic elastic behavior of sedimentary, anisotropic rock specimens over a range of confining and pore pressures up to 70 MPa, the original reservoir conditions. The static and dynamic properties are simultaneously measured for room dry shales, room dry sandstones, and brine saturated sandstones ...
by Franklin J. Ruiz Peña.
S.M.
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Marchetti, Mara. "Elastic properties characterization of nuclear fuels under extreme conditions." Thesis, Montpellier, 2017. http://www.theses.fr/2017MONTS053/document.
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Ce travail de recherche vise à étudier les propriétés élastiques par microscopie acoustique du combustible nucléaire dans trois situations particulières: combustible en utilisation normale en réacteur nucléaire, combustible stocké après la période d’irradiation et combustible en conditions extrêmes suite à un accident nucléaire. Les mesures réalisées sur les échantillons irradiés ont conduit à plusieurs résultats majeurs: validation d’une loi corrélant la vitesse des ondes de Rayleigh à la densité du dioxyde d’uranium irradié ou frais; détermination de la porosité dans le combustible irradié; évaluation du gonflement de la matrice en fonction du taux de combustion dans la gamme 0-100 GWdt-1M; développement d'un modèle empirique capable de prévoir la variation de module de Young en fonction du taux de combustion en prenant même en compte la teneur en dopants (Gd2O3, CeO2) ; quantification de l’évolution du module de Young du combustible suite à l'endommagement en stockage ; premières mesures sur du corium. Enfin, grâce au lien entre les propriétés thermiques et élastiques, différentes propriétés thermiques de l'UO2 ont été calculées en mesurant la vitesse de l'onde de surface de Rayleigh seuleThe focus of the present thesis is the determination of the elastic properties of nuclear fuel using high frequency acoustic microscopy. The nuclear fuel is considered under three different conditions: during its normal life in reactor, after its discharge and disposal in interim or long-term storage and subsequently to its severe degradation caused by a nuclear accident. Measurements performed on irradiated fuels allowed to validate a law between the density of fresh and irradiated fuel and the Rayleigh wave velocity; the determination of the irradiated fuel porosity and matrix swelling in the broad burnup range 0-100 GWdt-1M; the development of an empirical model capable of predicting the evolution of Young's modulus versus burnup correcting also for the additives content (Gd2O3, CeO2); Young's modulus evolution due to alpha-decay damage as in-storage condition; first corium measurements. Moreover, several UO2 thermal parameters were calculated only by means of the Rayleigh wave velocity thanks to the link between thermal and elastic properties
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Davis, Roosevelt. "A PREDICTION OF ELASTIC PROPERTIES OF AN ELASTIC COUPLING USING EXPERIMENTAL DATA AND FINITE ELEMENT ANALYSIS." MSSTATE, 2003. http://sun.library.msstate.edu/ETD-db/theses/available/etd-07242003-163336/.
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The dynamic properties of the elastic coupling are not readily known; therefore testing has to be performed in order to determine these properties. This is the primary objective for this thesis. The dynamic properties in question are the stiffness and damping. An attempt to determine the dynamic properties was also be carried out through the use of finite element analysis. There are two different configurations of couplings. One configuration forms the coupling from several elastic elements, referred to as HRC elements, which are manufactured in three sizes: A, B, and C. The second configuration, referred to as the HEMD coupling, has a single elastic member in the form of a hollow rubber/fabric ring connecting the input to the output. The couplings have cords made of either polyester or nylon. These cords will affect the dynamic properties of the coupling.
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Farmer, David John. "Elastic measurements in ultra-thin polymer structures." Thesis, University of Nottingham, 2016. http://eprints.nottingham.ac.uk/33073/.
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This thesis contains details of a series of experiments performed to investigate the acoustic and elastic properties of ultra-thin polymer structures. Three main investigations were conducted. The first involved studying quantised vibrations in ultra-thin (∼100 nm) polystyrene films on silicon substrates. These films were vibrated via the picosecond acoustic technique, an optical pump-probe method. Quantised, harmonic vibrations were observed in the films with frequencies of the order of 10 GHz. The polymer films were then loaded by evaporating small thicknesses (2.5 - 30 nm) of gold. The frequencies of loaded areas were observed relative to the unloaded films. This frequency shift is described via a theory that considers the elastic wave equation in the structure with appropriate boundary conditions. Excellent agreement between experiment and theory is achieved, suggesting the potential for using these films as ultra-sensitive mass sensors. The second experimental chapter deals with experiments performed on polymer Bragg reflectors. These multilayer structures were again investigated via the picosecond technique. The reflected intensity of the probe laser beam was observed to be modulated by the strain pulse as it travelled through the structure. These results were compared to theoretically generated signals and this comparison suggests that, in the polymer structures considered here, the modulation can be described almost exclusively by the photo-elastic effect. Although the modulation is small it opens up the possibility of using similar structures in combinations with micro-cavities to act as high frequency optical components. The final experimental chapter details attempts to develop a new metrology for elastic properties in ultra-thin polymer films floated on a water surface. The films were cut into annuli and placed on a Langmuir-Blodgett trough before surfactant was placed around the outside. By moving the barriers of the trough, a surface pressure difference between the inside and outside of the annulus could be controlled and a wrinkling pattern induced around the annulus. A system for imaging and counting the wrinkles as a function of the surface pressure difference was developed and a theory that attempts to describe this is detailed. While the experimental technique is successful in producing highly controlled, reproducible wrinkles, the theoretical analysis currently overestimates the Young's modulus of the films. The reasons for this as well as avenues for further work are considered. The results of these three investigations all demonstrate the rich physics accessible in ultra-thin polymer films. Furthermore, it points to their potential to b e a key material as devices are more commonly manufactured at the nano-scale.
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Wan, Yanyi. "Static and dynamic transport properties of 2D elastic random media /." View abstract or full-text, 2007. http://library.ust.hk/cgi/db/thesis.pl?PHYS%202007%20WAN.
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Sevostianov, Igor, Mahesh Bogarapu, and Pavel Y. Tabakov. "Correlation between elastic and electric properties for cyclically loaded metals." Springer, 2002. http://hdl.handle.net/10321/639.
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Originally published in: International Journal of Fracture, Vol. 2, No. 3-4, 2005.A new method of evaluation of the elastic property deterioration due to accumulated damage is suggested and experimentally verified. It is based on the explicit correlations between two groups of anisotropic properties – conductivity and elasticity, recently established for porous/microcracked materials with anistropic microstructures. An experimental study of fatigue has been done to verify the theoretical predictions. The electrical resistance and Young''s modulus are measured as functions of the number of loading cycles in the standard fatigue tests. The agreement between the theoretical predictions and the direct experimental data is better than 10% in all cases. The results allow one to use measurements of the electric resistance to estimate the damage accumulated in methal structures and the decrease of the elastic modulus.
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Armstrong, D. E. J. "Measuring elastic, plastic and fracture properties using micro-cantilever testing." Thesis, University of Oxford, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.526568.
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SOBREIRA, GUSTAVO HENRIQUE OLIVEIRA. "EVALUATION OF ELASTIC PROPERTIES OF CARBONATIC ROCKS FROM MICROSTRUCTURAL ANALYSIS." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2015. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=29612@1.
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PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIROCOORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIOR
PROGRAMA DE EXCELENCIA ACADEMICA
Reservatórios carbonáticos contêm entre 50 e 60 porcento de petróleo e gás do mundo. No entanto, estas rochas têm apresentado problemas operacionais consideráveis durante as etapas de perfuração e produção. Tais problemas são originados pelas dificuldades na caracterização adequada destas rochas em função da complexa distribuição espacial de suas micro e macro estrutura. Enquanto ambas as escalas possuem importância no entendimento do comportamento de carbonatos, o presente trabalho trata da análise da microestrutura. Nesse âmbito, a proposta deste trabalho integra o processamento e análises de imagens digitais, elaboração de malhas de elementos finitos e simulação numérica de forma a prever propriedades elásticas, com o objetivo de correlacionar a microestrutura e o módulo de Young. Foram utilizadas imagens digitais de amostras de afloramento (travertinos) considerados como possíveis análogas a rochas carbonáticas de reservatório. A metodologia implementada permitiu obter subamostras que incluem uma gama de microestruturas e porosidades numa única amostra para assim simular numericamente o módulo de Young. Conclui-se neste estudo que os poros maiores (vuggys) são os principais responsáveis pelo comportamento do material quando o mesmo é carregado, e também a influência da estrutura porosa nos resultados, foi possível observar que a posição dos poros afeta o módulo de elasticidade do corpo de prova.
Carbonate reservoirs contain between 50 and 60 percent of oil and gas reserves in the world. However, these rocks have presented considerable operating problems during the phases of drilling and production. Such problems are originated by the difficulties in the proper characterization of these rocks due to the complex spatial distribution of its micro and macro structure. While both scales have importance on the carbonate behavior understanding, this paper deals with the analysis of the microstructure. In this context, the aim of this work is part of the processing and digital image analysis, mesh preparation and finite element numerical simulation to predict elastic properties, in order to correlate the microstructure and the Young s modulus. Using digital images of outcrop samples (travertine) considered as possible analogous to carbonate rocks reservoir. The methodology implemented afforded sub-samples that include a range of porosities and microstructures for a single sample well numerically simulate the Young s modulus. It is concluded in this study that the larger pores (vuggys) are mainly responsible for the behavior of the material when it is loaded, and also the influence of the porous structure in the results, it was observed that the position of pores affects the modulus of elasticity of sample.
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Zhu, Wenqi. "Effective elastic properties of foams : Morphological study and micromechanical modeling." Thesis, Lyon, 2018. http://www.theses.fr/2018LYSEI043.
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Les matériaux cellulaires poreux de type mousse présentent un grand intérêt pour de nombreuses applications. Leurs propriétés thermiques, mécaniques, acoustiques dépendent fortement de leur microstructure complexe. Afin de mieux comprendre la relation microstructure/propriétés mécaniques de ces matériaux, une modélisation micromécanique basée sur une méthode d’homogénéisation périodique et le lemme de Hill est proposée pour prédire les propriétés élastiques effectives de ces matériaux. Une approche basée sur le diagramme de Voronoï est utilisée pour générer des structures de mousse périodiques réalistes plus ou moins irrégulières, couvrant une large gamme de matériaux . Différents types de mousses à forte porosité sont générés, non seulement des matériaux cellulaires à pores ouverts mais aussi des matériaux cellulaires à pores fermés. Des comparaisons avec des résultats issus de tomographie X d’architectures réelles 3D de mousses valident ces approches de Voronoï. Les simulations numériques permettent d’étudier l’influence des paramètres morphologiques des mousses sur les propriétés élastiques effectives. De nouvelles lois analytiques génériques de propriétés effectives sont déduites pour des mousses à cellules ouvertes de type Kelvin. Une attention particulière est portée sur la détermination de l’élément de volume représentatif (VER). Des méthodes statistiques spécifiques sont proposées pour déterminer le VER approprié aux modèles de mousse. Dans le cas des mousses polymères isolantes à cellules fermées irrégulières anisotropes, la confrontation avec des résultats d’essais mécaniques confirme la validité des modèles développésThanks to the excellent combination of physical, mechanical and thermal properties, foam materials bring new possibilities to extend the range of the properties for engineering, which is limited by fully dense solids. In this study, a micromechanical modeling based on Hill's lemma (Hill's lemma periodic computational homogenization approach) is proposed for predicting the effective elastic properties of foam materials. An approach based on Voronoi diagram is used to generate realistic periodic foam structures, including regular and irregular open-cell structures, and irregular closed-cell structures. First, the influences of morphological parameters of open-cell foams on the effective elastic properties are studied. The generated structures allow representing the details of the microstructure and cover a large range of foam materials for engineering purposes. With the assessments, new generic analytical laws are proposed for Kelvin open-cell foams by considering their morphological parameters. Second, the tomography images are analysed to obtain the morphological description of the real irregular open-cell structure. With these morphological parameters, numerous numerical realistic structures are generated. Specific statistic methods are proposed to determine the Representative Volume Element (RVE) for foam models. Third, the anisotropic irregular closed-cell foam is studied. The numerical structures are generated with the morphological description of the reconstructed tomography structure and the effective elastic properties of the closed-cell foam models are estimated. The numerical results show the satisfying agreement with the experimental results
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Gump, Jared Clinton. "Elastic properties of germanium selenium glasses and metastable cobalt films /." The Ohio State University, 2002. http://rave.ohiolink.edu/etdc/view?acc_num=osu1486462067840445.
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Åkerlind, Amanda. "Elastic properties of the Singö zone from a discrete approach." Thesis, KTH, Skolan för arkitektur och samhällsbyggnad (ABE), 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-268640.
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A rock mass is characterised by the properties of the intact rock and the fractures. Considering the impact of both constituents is of vital importance for assessing the behaviour of the rock mass. In particular in the case of complex or heterogeneous rock mass compositions. A discrete approach, by using the Discrete Fracture Network (DFN) methodology, enables for the consideration of these aspects.This master’s thesis concerns the evaluation of elastic properties of the Singö deformation zone. A discrete approach has been applied by three-dimensional discrete fracture network modelling, using previously evaluated DFN parameters. The elastic properties have then been obtained by analytical means by using the methodology developed by Davy et al. (2018).The results show that in comparison to earlier evaluations of the elastic properties of the Singö zone, the respective Young’s moduli and Poisson’s ratios obtained by this thesis may indicate a weaker material. However, this study differs from the earlier evaluation by more extensive DFN modelling and the application of a state of stress which is more representative of the surroundings of the zone in Forsmark. The analysis indicates that theadequate model size is slightly larger than the maximum studied DFN model size. A suggested future improvement would be a re-evaluation and updating of the DFN parameters. As a concluding remark, the methodology of Davy et al. (2018) may prove successful in the future for the application to deformation zones.En bergmassa karakteriseras av egenskaperna hos det intakta berget och dess sprickor. Det är därmed av vikt att båda dessa beståndsdelar beaktas vid utvärdering av bergmassans beteende, speciellt vid komplexa eller heterogena bergartssammansättningar.Detta examensarbete syftar till att utvärdera deformationsegenskaper för den så kallade Singözonen. Ett diskret angreppsätt har tillämpats genom modellering av tredimensionella diskreta spricknätverk med hjälp av tidigare utvärderade DFN-parametrar. Deformationsegenskaperna har sedan utvärderats med hjälp av metodiken som presenteras i Davy et al. (2018).Jämfört med tidigare utvärderade deformationsegenskaper hos Singözonen så indikerar resultaten av denna masteruppsats en svagare bergmassa, med hänsyn till uppskattade värden på E-moduler och tvärkontraktionstal. Däremot skiljer sig modelleringsprocessen i detta arbete mot de som utförts i de tidigare studierna. Detta med hänsyn till omfattningen av DFN-modelleringen samt tillämpandet i detta arbete av en spänningsansats som är mer representativ för Forsmarksområdet. Vidare indikerar resultaten att den representativa modellvolymen är något större än den största modellvolym som tillämpats i detta arbete. Förslagsvis kan en utvärdering och eventuell uppdatering av de använda DFN-parametrarna utgöra en möjlig utveckling eller förbättring av det arbete som utförts i detta mastersarbete. Slutligen kan det konstateras att framtida tillämpningar av den metodik som tagits fram av Davy et al. (2018) verkar lämplig att applicera på deformationszoner.
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SALVALAGLIO, MARCO. "Continuum modeling of vertical heterostructures: elastic properties and morphological evolution." Doctoral thesis, Università degli Studi di Milano-Bicocca, 2016. http://hdl.handle.net/10281/100682.
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The development of cutting-edge opto- and micro-electronic devices requires novel fabrication techniques, able to deliver high-quality materials, monolithically integrable into Si-based technology. Theoretical models and simulations supporting the experimental activities are highly needed to fully understand the growth physics at the nano- and micro-scale and tailor semiconductor heterostructures for technological applications. In this work, the modeling of the plasticity onset and of the morphological evolution for Ge/Si vertical heterostructures is introduced, fostered by the peculiar features of such systems with respect to the standard heteroepitaxy. Indeed, the aim of this thesis is to understand the main properties of systems with large height-to-base aspect-ratios, in order to offer new solutions for the realization of heterostructures with unprecedented material quality. Continuum models are selected to describe length scales ranging from a few nanometers to microns, and time scales of minutes (or even more).
By means of the linear elasticity theory equations, solved by Finite Element Method (FEM) simulations, the competition between elastic and plastic relaxation in vertical Ge/Si systems is investigated. The critical parameters for the insertion of dislocations are determined for a single-layer structure, made of a SiGe layer on a Si pillar, and then generalized to multilayer configurations. Moreover, the possibility to achieve coherent structures at any size is demonstrated, provided that a proper grading of the Ge content during the growth is considered. A recipe for the calculation of such a grading of the Ge content is also introduced. Several comparisons with experiments show the generality of the proposed investigation for heterostructures at the nanoscale, and the versatility of the developed method. Moreover, thanks to dedicated experiments stimulated by the theoretical predictions, dislocation-free structures are proven to be feasible also at the micrometer scale.
The three-dimensional evolution in time of vertical microcrystals is investigated by means of a phase-field model and FEM simulations. In particular, the annealing of Ge on Si microcrystals is modeled by considering the surface diffusion driven by the tendency toward the minimization of the surface energy. This allows the evolution induced by annealing of single structures to be described. Moreover, the coalescence mechanism for crystal arrays, resulting in the formation of a suspended film, is predicted. Such an evolution is confirmed by dedicated experiments and leads to the fabrication of a promising system for the high-quality heterogeneous integration of semiconductors. The coalescence occurring for closely spaced crystals during high-temperature growth is also assessed. The original extensions of the PF model, required by the theoretical investigations of the morphological evolution, are illustrated in the details. Particular attention is devoted to the description of anisotropic surface energies responsible for crystal faceting in thermodynamic regimes. Moreover, further extensions of the method, dealing with an accurate description of the growth processes, are reported.
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Ashaolu, Folorunso. "Measuring the Nanoindentation Properties of Alendronate-Time Treated Canine Cortical." DigitalCommons@CalPoly, 2011. https://digitalcommons.calpoly.edu/theses/522.
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This study examines the nanoindentation (energy inclusive) properties of 0.2 mg/kg alendronate treated ribs at one and three years against a vehicle treated control in a fresh-frozen, non-cold-mounted, condition. This was to verify if the tissue-level properties for 0.2 ALN treated beagles would increase because of an increased level of mineralization despite a microdamage increase.
A total of twelve (12) skeletally mature (1–2 years old) female beagle dogs were treated daily for three years and one year with oral doses of vehicle (VEH, 1 mL/kg saline) or alendronate (ALN, 0.2 Merck, Rahway, NJ). The 0.2 mg dose corresponds, on a milligram per kilogram basis, to those used for treatment of postmenopausal osteoporosis. Transversely cut samples were ground and polished to 0.3μm, and were then mounted while nanoindentation was performed. The data obtained were analyzed using two modes of diamond area functions: ideal function and general function. The statistical analysis for the data were carried out using a repeated measured ANOVA (SAS V 9.1, Cary NC.) with the measured and calculated mechanical property (elastic modulus or hardness) or energy property (elastic work or plastic work) as the dependent variable and treatment (control, 1 year or 3 years) modeled as the subject. Either Turkey-Kramer or Bonferroni method was used to compute the pair-wise difference. The results indicate that when compared to one year, the three years of alendronate medication for postmenopausal osteoporosis did not have any effect on the strength of the canine cortical bone, whereas this had effect on the hardness of the subjects. This increase in the medication time resulted in an increase in the elastic work but a decrease in the plastic work. The two methods (modes) of diamond area function analysed showed different mechanical properties (elastic modulus and hardness).
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Puentes, Heras M. "The use of SAW methods in probing near-surface elastic properties." Thesis, University of Oxford, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.299101.
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Nanda, Atul. "Finite element analysis of elastic-plastic anisotropic soils." Diss., Virginia Polytechnic Institute and State University, 1987. http://hdl.handle.net/10919/53650.
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Elastic-plastic stress·strain models are developed for initially anisotropic soils. The models are developed for both total stress (undrained) analyses and for effective stress (drained) analyses. For anlsotroplc undralned coheslve soils under monotonic loading an elastic-plastic isotropic-hardening model is developed. For complex loading conditions the model is extended using multisurface plasticity. For effective stress analyses of soils, the Cam-Clay model concepts are generalized for initially anisotropic soils. Both isotropic and anisotropic hardening are used in the model. The behavior of the models is investigated under several loading conditions and some comparisons are made with experimental triaxial data. A nonlinear three-dimensional finite element program is developed in which the models are implemented. An updated Lagrangian large displacement analysis is also included. The constitutive models developed are used to investigate the influence of initial anisotropy on the bearing capacity, deformation and pore pressure development under footings in both plane-strain and three dimensional conditions. It is found that for the range of anisotropy encountered in the field, the deformation and bearing capacity are significantly different.Ph. D.
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Ziebarth, Noel Marysa. "Atomic Force Microscopy Measurement of the Elastic Properties of the Lens." Scholarly Repository, 2008. http://scholarlyrepository.miami.edu/oa_dissertations/181.
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The goal of this project was to develop techniques and instrumentation to measure the elastic properties of the lens and lens capsule in situ and their changes with age using Atomic Force Microscopy (AFM). The studies include the construction, characterization, and calibration of laboratory-based Atomic Force Microscope (AFM) to measure mechanical properties of ophthalmic tissues. Atomic Force Microscopy is a nanoscale imaging technique that has been applied to mechanical property measurement through nanoindentation. Young's modulus of elasticity is determined by monitoring the cantilever deflections when it contacts the sample. The studies also include the development of tissue preparation techniques to enable measurement of the lens elasticity using AFM. This study found that lens capsule elasticity decreases with age, outer lens cortex elasticity remains constant with age, and the inner lens cortex is stiffer than the outer lens cortex. The effect of the changing biometry and mechanical properties with age was investigated by developing a mathematical model of accommodation. These changes will be the limiting factor to accommodative amplitude. Changes in lens capsule mechanical properties will affect the maximal accommodative amplitude in older eyes.
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Sklar, Zenon. "Quantitative acoustic microscopy of coated materials." Thesis, University of Oxford, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.308851.
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Le, Menestrel Maxime. "Finite element modeling of the elastic properties of isotropic and anisotropic synthetic foams." Thesis, Georgia Institute of Technology, 2002. http://hdl.handle.net/1853/16038.
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Willoughby, Natasha. "Dynamic homogenization for the elastic properties of periodic and random composites." Thesis, University of Manchester, 2013. https://www.research.manchester.ac.uk/portal/en/theses/dynamic-homogenization-for-the-elastic-properties-of-periodic-and-random-composites(da82e607-bc1f-40e9-8e62-ec5fbca1f68f).html.
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In this thesis we are interested in the propagation of low-frequency linear elastic waves through composite materials. We use a variety of dynamic homogenization techniques to find the effective elastic properties of some composites. We consider composites with isotropic phases for ease of exposition but the theory could easily be extended to anisotropic inclusions or host.We use a Representative Volume Element approach with the Method of Asymptotic Homogenization to model a random fibre-reinforced composite. The fibres are all aligned in the same direction and are taken to be of infinite extent, so the composite is essentially two-dimensional. For a random composite we have considered the anti-plane case for SH wave propagation and the in-plane case for P and SV elastic wave propagation, extending the previous published work of Parnell and Abrahams (2006), (2008a), in which a periodic fibre-reinforced composite was studied. We also show, for a simple example, that it is possible to extend the Representative Volume Element method to a three-dimensional particulate composite.In this thesis an Integral Equation Method for homogenization is also studied, with application to periodic fibre-reinforced composites. We have extended the work of Parnell and Abrahams (2008b), which considered SH wave propagation only, to the case of P and SV wave propagation.
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Peydaye, Saheli Ghazal. "Homogenization Relations for Elastic Properties Based on Two-Point Statistical Functions." Diss., Georgia Institute of Technology, 2006. http://hdl.handle.net/1853/14492.
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In this research, the homogenization relations for elastic properties in isotropic and anisotropic materials are studied by applying two-point statistical functions to composite and polycrystalline materials. The validity of the results is investigated by direct comparison with experimental results.
In todays technology, where advanced processing methods can provide materials with a variety of morphologies and features in different scales, a methodology to link property to microstructure is necessary to develop a framework for material design. Statistical distribution functions are commonly used for the representation of microstructures and also for homogenization of materials properties. The use of two-point statistics allows the materials designer to consider morphology and distribution in addition to properties of individual phases and components in the design space.
This work is focused on studying the effect of anisotropy on the homogenization technique based on two-point statistics. The contribution of one-point and two-point statistics in the calculation of elastic properties of isotropic and anisotropic composites and textured polycrystalline materials will be investigated. For this purpose, an isotropic and anisotropic composite is simulated and an empirical form of the two-point probability functions are used which allows the construction of a composite Hull. The homogenization technique is also applied to two samples of Al-SiC composite that were fabricated through extrusion with two different particle size ratios (PSR). To validate the applied methodology, the elastic properties of the composites are measured by Ultrasonic methods. This methodology is then extended to completely random and textured polycrystalline materials with hexagonal crystal symmetry and the effect of cold rolling on the annealing texture of near- Titanium alloy are presented.
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Lee, Jae Sang. "Effective properties of three-phase electro-magneto-elastic multifunctional composite materials." Thesis, Texas A&M University, 2003. http://hdl.handle.net/1969.1/1448.
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Coupling between the electric field, magnetic field, and strain of composite materials is achieved when electro-elastic (piezoelectric) and magneto-elastic (piezomagnetic) particles are joined by an elastic matrix. Although the matrix is neither piezoelectric nor piezomagnetic, the strain field in the matrix couples the E field of the piezoelectric phase to the B field of the piezomagnetic phase. This three-phase electro-magneto-elastic composite should have greater ductility and formability than a two-phase composite in which E and B are coupled by directly bonding two ceramic materials with no compliant matrix. A finite element analysis and homogenization of a representative volume element is performed to determine the effective electric, magnetic, mechanical, and coupled-field properties of an elastic (epoxy) matrix reinforced with piezoelectric and piezomagnetic fibers as functions of the phase volume fractions, the fiber (or particle) shapes, the fiber arrangements in the unit cell, and the fiber material properties with special emphasis on the symmetry properties of the fibers and the poling directions of the piezoelectric and piezomagnetic fibers. The effective magnetoelectric moduli of this three-phase composite are, however, less than the effective magnetoelectric coefficients of a two-phase piezoelectric/piezomagnetic composite, because the epoxy matrix is not stiff enough to transfer significant strains between the piezomagnetic and piezoelectric fibers.
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Ridler, Anne C. "Can internal elastic properties of cartilage be measured using MR elastography?" Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2001. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/MQ58836.pdf.
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Sun, Miao. "Optimal Recovery of Elastic Properties for Anisotropic Materials through Ultrasonic Measurements." Fogler Library, University of Maine, 2002. http://www.library.umaine.edu/theses/pdf/SunM2002.pdf.
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