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MEASUREMENT OF ELASTIC PROPERTIES OF MATERIALS BY THE ULTRASONIC THROUGH-TRANSMISSION TECHNIQUE

FRANCO, Ediguer E.; MEZA, Juan M.; BUIOCHI, Flavio
Fonte: UNIV NAC COLOMBIA, FAC NAC MINAS Publicador: UNIV NAC COLOMBIA, FAC NAC MINAS
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
66.12%
The elastic mechanical behavior of elastic materials is modeled by a pair of independent constants (Young`s modulus and Poisson`s coefficient). A precise measurement for both constants is necessary in some applications, such as the quality control of mechanical elements and standard materials used for the calibration of some equipment. Ultrasonic techniques have been used because wave velocity depends on the elastic properties of the propagation medium. The ultrasonic test shows better repeatability and accuracy than the tensile and indentation test. In this work, the theoretical and experimental aspects related to the ultrasonic through-transmission technique for the characterization of elastic solids is presented. Furthermore, an amorphous material and some polycrystalline materials were tested. Results have shown an excellent repeatability and numerical errors that are less than 3% in high-purity samples.; Centro Integrado para el Desarrollo de la Investigacion (CIDI) of the Universidad Pontificia Bolivariana

Optimal design of periodic functionally graded composites with prescribed properties

PAULINO, Glaucio H.; SILVA, Emilio Carlos Nelli; LE, Chau H.
Fonte: SPRINGER Publicador: SPRINGER
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
55.98%
The computational design of a composite where the properties of its constituents change gradually within a unit cell can be successfully achieved by means of a material design method that combines topology optimization with homogenization. This is an iterative numerical method, which leads to changes in the composite material unit cell until desired properties (or performance) are obtained. Such method has been applied to several types of materials in the last few years. In this work, the objective is to extend the material design method to obtain functionally graded material architectures, i.e. materials that are graded at the local level (e.g. microstructural level). Consistent with this goal, a continuum distribution of the design variable inside the finite element domain is considered to represent a fully continuous material variation during the design process. Thus the topology optimization naturally leads to a smoothly graded material system. To illustrate the theoretical and numerical approaches, numerical examples are provided. The homogenization method is verified by considering one-dimensional material gradation profiles for which analytical solutions for the effective elastic properties are available. The verification of the homogenization method is extended to two dimensions considering a trigonometric material gradation...

"Efeitos do tabagismo sobre o sistema cardiovascular: hemodinâmica e propriedades elásticas arteriais" ; Effects of cigarette smoking on cardiovascular system: hemodynamic and elastic properties arterial

Silva, Maria Alice Melo Rosa Tavares
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 25/07/2005 PT
Relevância na Pesquisa
46.16%
Objetivo Avaliar os efeitos do tabagismo sobre o sistema cardiovascular, através de metodologia não invasiva, analisando as alterações hemodinâmicas clínicas e propriedades elásticas arteriais, após exposição ao fumo. Métodos Estudo realizado em 45 voluntários sendo 18 (F) e 27 (M), fumantes T (n = 25, idade 40 ± 9 anos) e não fumantes NT (n = 20, idade 39 ± 9 anos), que foram submetidos a determinação do monóxido de carbono (CO) e avaliação das propriedades elásticas arteriais por ultrassonografia e teste de função endotelial (hiperemia reativa - HR) antes (B1) e após (B2) a exposição por 20 minutos a um cigarro ou à degustação de uma bala. Resultados Os grupos NT e T mostraram-se homogêneos. A concentração de CO no grupo T era maior do que no grupo NT em condições basais. A concentração de CO no grupo NT não variou antes e após à exposição proposta (bala) mas no grupo T aumentou de maneira significante após o cigarro. A pressão arterial sistólica (PAS) foi igual no B1 nos dois grupos, mas significativamente maior no B2 para o Gr T. A pressão arterial diastólica (PAD) no B1 e B2 não mostrou variação estatísticamente significante nos dois grupos. A freqüência cardíaca (FC) apresentou comportamento estatisticamente diferente nos dois grupos (NT apresentou redução e T apresentou aumento). Em relação às propriedades elásticas arteriais e resposta do fluxo regional: a complacência e a distensibilidade já se mostraram diferentes (p < 0...

Estudo da influência das propriedades elásticas da interface bloco-argamassa na rigidez de paredes de alvenaria; Study of the influence of elastic properties of unit-mortar interfaces on the stiffness of masonry walls

Santos, Emerson Acácio Feitosa
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 26/11/2014 PT
Relevância na Pesquisa
46.18%
Este trabalho tem o objetivo de avaliar a influência das propriedades elásticas da interface bloco-argamassa no comportamento elástico global de paredes de alvenaria. Por ser um material heterogêneo, as propriedades mecânicas da alvenaria são influenciadas pelas propriedades dos seus diferentes componentes, bloco e argamassa, e pela ligação entre eles. As juntas de argamassa constituem planos de fraqueza, desta forma, características como rigidez, direção e o estado de tensão podem influenciar consideravelmente o comportamento global e consequentemente os parâmetros de projeto. O trabalho foi composto por duas etapas, uma experimental e outra numérica. Na etapa experimental um extenso programa de ensaios foi realizado buscando avaliar as propriedades elásticas normais e tangenciais as juntas de argamassa. Nesta etapa também é apresentado um conjunto de procedimentos que possibilita a caracterização dos componentes da alvenaria de forma não destrutiva. Um estudo paramétrico foi realizado na parte numérica, permitindo identificar quais propriedades da interface exercem mais efeito sobre o comportamento elástico da alvenaria. Também foi avaliado como a heterogeneidade da alvenaria pode afetar a distribuição de ações horizontais ao longo de uma edificação. Os resultados obtidos indicaram que a interface bloco-argamassa exerce influência significativa sobre o comportamento elástico da alvenaria...

Simulações Monte Carlo de integrais de trajetória : propriedades elásticas do 4He sólido; Path integrals Monte Carlo simulations : elastic properties of 4He

Luis Aldemar Peña Ardila
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 30/11/2010 PT
Relevância na Pesquisa
56.17%
O método Monte Carlo de integrais de trajetória (PIMC) é um sofisticado método para simular sistemas quânticos de muitos corpos. Em particular, é usado para a simulação de sistemas bosônicos como o 4He. O principal objetivo deste trabalho de Mestrado é aplicar o método PIMC para determinar as constantes elásticas do 4He sólido na sua fase hcp. Estas propriedades são muito importantes por estarem envolvidas num possível novo estado da matéria que foi descoberto no hélio sólido: a fase supersólida. Para realizar este objetivo, empregamos o pacote computacional PIMC++, que é uma implementação do método PIMC na linguagem C++, desenvolvido no grupo do Prof. David Ceperley. Primeiro realizamos testes básicos, calculando a energia total e a capacidade térmica para bósons livres, para as quais existem resultados exatos. Em seguida, consideramos a fase líquida do 4He, determinando propriedades como a energia, a fração de condensado e a densidade superfluida para o 4He líquido abaixo de 4K às condições de pressão de vapor saturado. Além disso, determinamos a função de correlação de pares e o fator de estrutura. Todas as propriedades apresentam boa concordância com dados experimentais. Após estes testes iniciais...

Modelagens teóricas e empíricas aplicadas à investigação da conexão entre as propriedades petrofísicas e elásticas em rochas carbonáticas; Theoretical and empirical models applied to the investigation of connection between the petrophysical and elastic properties on carbonate rocks

Elita Selmara de Abreu
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 17/12/2010 PT
Relevância na Pesquisa
46.16%
O principal propósito dessa dissertação é estudar modelos de meio efetivo de física de rochas que conecte as propriedades petrofísicas e as propriedades elásticas, assim como a sua aplicação na investigação dessas propriedades em rochas carbonáticas. Inicialmente será feita uma introdução a alguns modelos de física de rochas para meio efetivo, conhecidos como modelo de Voigt-Reuss-Hill, modelo de Kuster & Toksöz, modelo Diferencial de Meio Efetivo e relação de Gassmann, com objetivo de estabelecer os parâmetros que serão medidos e utilizados no desenvolver do trabalho. Após essa parte introdutória, baseado no modelo de Xu-Payne, foram realizadas uma série de análises de atributos geométricos, como a distribuição de tipos de poros, obtidas através de lâminas petrográficas com intuito de descrever a correlação entre as propriedades petrofísicas e elásticas e assim poder calibrar o modelo teórico utilizado na predição dessas propriedades. Dessa forma, o modelo calibrado passa a desempenhar um papel mais condizente com o sistema poroso da rocha permitindo uma melhor correlação entre os parâmetros elásticos e petrofísicos. Os resultados obtidos mostram que a utilização da informação de lâminas petrográficas...

Assessing wood quality by spatial variability of transverse elastic properties within the stem: case study on P. pinaster at the meso scale

Pereira, João
Fonte: Instituto Politécnico de Viseu Publicador: Instituto Politécnico de Viseu
Tipo: Tese de Doutorado
Publicado em 17/06/2013 ENG
Relevância na Pesquisa
56.16%
In this work the radial and longitudinal variations of maritime pine (Pinus pinaster Ait.) transverse elastic properties, within the stem, were investigated. Ring-oriented tensile tests through five radial positions and three height levels were carried out in 750 radial-tangential specimens, at the growth ring scale (meso scale). The strain fields over the gauge section were measured by digital image correlation. A balance between accuracy and spatial resolution was found out in order to assess the gradient strain fields generated by the material heterogeneous mesostructure. A segmentation technique based on image processing and analysis was implemented in order to split each annual ring, at the region of interest, in three main tissues: resin ducts, earlywood (EW) and latewood (LW). Accordingly, transverse elastic moduli of each EW and LW layers were then estimated by two different identification methods: the Anisotropic based method (AbM) and the Virtual fields method (VFM). The VFM was applied to directly identify in-situ Q11 and Q66 stiffness components associated to EW and LW and the AbM was applied to the global ER and GRT evaluation. These effective mechanical properties were used to infer the local ones as a function of mean density...

Contributions of Trabecular Rods of Various Orientations in Determining the Elastic Properties of Human Vertebral Trabecular Bone

Liu, X. Sherry; Zhang, X. Henry; Guo, X. Edward
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
46.15%
Trabecular bone networks consist of two basic microstructural types: plates and rods. Although trabecular rods represent only a small fraction of total bone volume, their existence has important roles in failure initiation and progression. The goal of this study was to quantitatively examine the contributions of trabecular rods in various orientations to the anisotropic elastic moduli of human vertebral trabecular bone. Twenty-one human vertebral trabecular bone specimens were scanned by micro computed tomography (µCT). A coordinate system of orthotropic axes representing the best elastic orthotropic symmetry was determined for each sample. Individual trabeculae segmentation (ITS), a 3D image analysis technique, was performed to identify each individual trabecular rod and determine its orientation in the orthotropic coordinate system. Next, three rod-removed images were created where longitudinal, oblique, or transverse trabecular rods were removed, respectively, from the original µCT images. The original and three categories of rod-removed images were then converted to finite element (FE) models for evaluation of their elastic moduli and anisotropy. Both the transverse and oblique rod-removal caused significant decreases in all six elastic moduli. However...

Regional, ontogenetic, and sex-related variations in elastic properties of cortical bone in baboon mandibles

Wang, Qian; Ashley, Dennis W.; Dechow, Paul C.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /04/2010 EN
Relevância na Pesquisa
46.19%
Understanding the mechanical features of cortical bone and their changes with growth and adaptation to function plays an important role in our ability to interpret the morphology and evolution of craniofacial skeletons. We assessed the elastic properties of cortical bone of juvenile and adult baboon mandibles using ultrasonic techniques. Results showed that, overall, cortical bone from baboon mandibles could be modeled as an orthotropic elastic solid. There were significant differences in the directions of maximum stiffness, thickness, density, and elastic stiffness among different functional areas, indicating regional adaptations. After maturity, the cortical bone becomes thicker, denser, and stiffer, but less anisotropic. There were differences in elastic properties of the corpus and ramus between male and female mandibles which are not observed in human mandibles. There were correlations between cortical thicknesses and densities, between bone elastic properties and microstructural configuration, and between the directions of maximum stiffness and bone anatomical axes in some areas. The relationships between bone extrinsic and intrinsic properties bring us insights into the integration of form and function in craniofacial skeletons and suggest that we need to consider both macroscopic form...

NUMERICAL PREDICTION OF EFFECTIVE ELASTIC PROPERTIES AND EFFECTIVE THERMAL EXPANSION COEFFICIENT FOR POROUS YSZ MICROSTRUCTURES IN SOLID OXIDE FUEL CELLS

Shakrawar, Sangeeta
Fonte: Quens University Publicador: Quens University
Tipo: Tese de Doutorado
EN; EN
Relevância na Pesquisa
66.21%
Solid oxide fuel cells represent a potentially important application for ceramic materials. There are, however, some significant issues which can affect the reliability and durability of the cell. Mechanical failure owing to stress is one of the critical factors which can affect the stability and working life of the fuel cell stacks. These stresses generate in Solid Oxide Fuel Cells (SOFCs) owing to mechanical forces and change in temperature during fabrication, assembly and operating conditions. There can be chances of cell delamination and micro-cracks in cell electrodes if these stresses are too high. The elastic properties and thermal expansion coefficient play a vital role to improve cell stability and performance. These properties depend on the types of materials and geometries of the composites. In this research, a numerical framework to predict the effective elastic properties and the effective thermal expansion coefficient for porous Yttria-Stabilized Zirconia (YSZ) electrode microstructures in a Solid Oxide Fuel Cell is presented. The electrodes of Solid Oxide Fuel Cells are discretized as porous microstructures that are formed by randomly distributed and overlapping spheres with particle size distributions that match those of actual ceramic powder. Three-dimensional (3D) microstructures of YSZ-pore are formed with a porosity ranging from 25% to 40%. The technique involves the construction of the YSZ-pores microstructures based on measurable starting parameters and subsequent numerical prediction of effective elastic properties and effective thermal expansion coefficient. Three domain sizes are considered for the generation of YSZ-pore microstructures. The method of prediction of effective Young’s modulus (Eeff)...

Subsampling and homogenization to investigate variability of composite material mechanical properties

PINEAU, Pierre; DAU, Frédéric
Fonte: Elsevier Publicador: Elsevier
EN
Relevância na Pesquisa
56.12%
This paper presents an innovative homogenization sampling technique applied to multiscale modelling of composite materials. The goal is to build efficiently statistical variability of mechanical properties at mesoscopic scale from the heterogeneous media analysis at microscopic scale. It is applied to the transverse elastic properties of a unidirectional Long Fibres Reinforced Composite (LFRC). A large representative part of the ply – the cell – is modelled from a micrography and studied at microscopic scale with the Finite Element Analysis (FEA) under 2D plane strain hypothesis. The study consists in estimating the effective elastic properties of subcells, subparts of the previous cell, thanks to a specifically developed numerical procedure. A unique calculation is computed on the entire ply reduced to three basic loading cases is applied to the cell. Subsamples taken into the simulation cell are homogenized at post-processing level of strain and stress fields. A standard mechanics approach was considered. Various subsampling schemes are performed with various size and spatial distribution to generate variability functions of effective elastic properties at mesoscopic scale. A statistical inference is highlighted: the variability parameters vary with the way of sampling. Dispersion functions are finally obtained and discussed.

Simulation of the stretch blow moulding process: from the modelling of the microstructure evolution to the end-use elastic properties of polyethylene terephthalate bottles

COSSON, Benoit; CHEVALIER, Luc; REGNIER, Gilles
Fonte: Springer Publicador: Springer
Relevância na Pesquisa
66.09%
The original publication is available at www.springerlink.com; The whole stretch blow-moulding process of PET bottles is simulated at the usual process temperature in order to predict the elastic end-use properties of the bottles. An anisotropic viscoplastic constitutive law, coupled with microscopic variables, is dentified from uniaxial tensile tests performed at different strain rates and temperatures. The microstructure evolution is characterised by crystallinity measurements from interrupted tests and frozen samples. For each specimen tested, the Young modulus is measured at room temperature. Numerical simulations of the blow moulding process are run using the C-NEM method. A micromechanical modelling is post-processed after the simulation to predict the elastic properties. Predictions of Young modulus distributions in bottles are in agreement with the ones measured on blow-moulded bottles.

Determination of the Elastic Properties of Tomato Fruit Cells with an Atomic Force Microscope

Zdunek, Artur; Kurenda, Andrzej
Fonte: MDPI Publicador: MDPI
Tipo: Artigo de Revista Científica
Publicado em 11/09/2013 EN
Relevância na Pesquisa
46.15%
Since the mechanical properties of single cells together with the intercellular adhesive properties determine the macro-mechanical properties of plants, a method for evaluation of the cell elastic properties is needed to help explanation of the behavior of fruits and vegetables in handling and food processing. For this purpose, indentation of tomato mesocarp cells with an atomic force microscope was used. The Young's modulus of a cell using the Hertz and Sneddon models, and stiffness were calculated from force-indentation curves. Use of two probes of distinct radius of curvature (20 nm and 10,000nm) showed that the measured elastic properties were significantly affected by tip geometry. The Young's modulus was about 100 kPa ± 35 kPa and 20 kPa ± 14 kPa for the sharper tip and a bead tip, respectively. Moreover, large variability regarding elastic properties (>100%) among cells sampled from the same region in the fruit was observed. We showed that AFM provides the possibility of combining nano-mechanical properties with topography imaging, which could be very useful for the study of structure-related properties of fruits and vegetables at the cellular and sub-cellular scale.

First-principles study of structural, electronic and elastic properties of Nb4AlC3

Bouhemadou,A.
Fonte: Sociedade Brasileira de Física Publicador: Sociedade Brasileira de Física
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/03/2010 EN
Relevância na Pesquisa
66.16%
Using First-principles calculations, we have studied the structural, electronic and elastic properties of Nb4AlC3, a new compound belonging to the MAX phases. Geometrical optimization of the unit cell is in good agreement with the experimental data. The effect of high pressures, up to 20 GPa, on the lattice constants shows that the contractions are higher along the c-axis than along the a-axis. We have observed a quadratic dependence of the lattice parameters versus the applied pressure. The band structure shows that this compound is electrical conductor. The analysis of the site and momentum projected densities shows that bonding is due to Nb d-C p and Nb d-Al p hybridizations. The Nb d-C p bond is lower in energy and stiffer than Nb d-Al p bond. The elastic constants are calculated using the static finite strain technique. We derived the bulk and shear moduli, Young's modulus and Poisson's ratio for ideal polycrystalline Nb4AlC3 aggregate. We estimated the Debye temperature of Nb4AlC3 from the average sound velocity. This is the first quantitative theoretical prediction of the elastic properties of Nb4AlC3 compound, and it still awaits experimental confirmation.

Finite element modelling of the effective elastic properties of partially saturated rocks

Makarynska, Dina; Gurevich, Boris; Ciz, Radim; Arns, Christoph; Knackstedt, Mark
Fonte: Pergamon Press Publicador: Pergamon Press
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
66.06%
Simulation of effective physical properties from microtomographic 3D images of porous structures allows one to relate properties of rocks directly to their microstructure. A static FEM code has been previously used to estimate effective elastic properties

Study of the effect of freezing on the visco-elastic properties of strawberries

Fundo, J.; Brandão, T. R. S.; Quintas, M.; Silva, C. L. M.
Fonte: Grupo Español de Reologia / Sociedade Portuguesa de Reologia Publicador: Grupo Español de Reologia / Sociedade Portuguesa de Reologia
Tipo: Artigo de Revista Científica
Publicado em //2004 ENG
Relevância na Pesquisa
66.18%
The objective of this work was to study the influence of freezing on the visco-elastic properties of strawberries. Food structure plays an important role in food quality and functionality. It is important for the consumers to find an identical sensation when they eat a fresh strawberry and when the strawberry is defrosted. The visco-elastic properties of a food product are an indirect measure of its structure. Experimental measurements of these properties may correlate to changes on the physical attributes of the product. In this work, a dynamic mechanical analyser was used to assess changes on loss (E’’) and storage (E’) modulus, applying a compressive test with a Ø1.5 cm parallel plate geometry. Strawberries were acquired in a local market and frozen in a blast and fluidized bed freezer at –30 ºC for 1 hour. Samples were stored at –30 ºC in freezing chambers. Analyses were performed on fresh strawberries, after freezing and during storage. The samples were cut in small cylinders (1.5cm x 1.5cm) and left to relax during 1 hour at room temperature. Preliminary tests were performed in order to evaluate the linear visco-elastic region and the loss and storage modulus were determined. A dynamic frequency sweep test was also performed. Results showed that the behaviour of fresh strawberry sample varies significantly when compared with a defrosted sample. The influence of the storage still cannot be evaluated and is currently under study. Overall...

The Influence of the Degree of Heterogeneity on the Elastic Properties of Random Sphere Packings

Schenker, Iwan; Filser, Frank T.; Hütter, Markus; Gauckler, Ludwig J.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
46.21%
The macroscopic mechanical properties of colloidal particle gels strongly depend on the local arrangement of the powder particles. Experiments have shown that more heterogeneous microstructures exhibit up to one order of magnitude higher elastic properties than their more homogeneous counterparts at equal volume fraction. In this paper, packings of spherical particles are used as model structures to computationally investigate the elastic properties of coagulated particle gels as a function of their degree of heterogeneity. The discrete element model comprises a linear elastic contact law, particle bonding and damping. The simulation parameters were calibrated using a homogeneous and a heterogeneous microstructure originating from earlier Brownian dynamics simulations. A systematic study of the elastic properties as a function of the degree of heterogeneity was performed using two sets of microstructures obtained from Brownian dynamics simulation and from the void expansion method. Both sets cover a broad and to a large extent overlapping range of degrees of heterogeneity. The simulations have shown that the elastic properties as a function of the degree of heterogeneity are independent of the structure generation algorithm and that the relation between the shear modulus and the degree of heterogeneity can be well described by a power law. This suggests the presence of a critical degree of heterogeneity and...

On the determination of the elastic properties of geopolymeric materials using non-destructive ultrasonic techniques

Lawson, Joseph L.
Fonte: Rochester Instituto de Tecnologia Publicador: Rochester Instituto de Tecnologia
Tipo: Tese de Doutorado
EN_US
Relevância na Pesquisa
66.23%
Current methods of determining the elastic modulus and Poisson’s ratio for geopolymeric materials are limited by the destructive nature of compressive strength and bending testing analysis techniques. Since these tests are not repeatable, there is no means of evaluating whether measured properties are a result of the actual materials or the effect of possible mechanical defects. This study applies a relationship between the speed of sound through a material and its elastic properties to determine the elastic modulus and Poisson’s ratio of geopolymeric samples. In addition to these elastic properties, the density, percent pore volume, average pore diameter and standard deviation of pore diameter were also evaluated. These material characteristics were determined as a relationship to the Si:Al ratio of sodium activated metakaolin based geopolymers with Si:Al ranging from 1.49 to 6.4. It was found that lower Si:Al values were consistently around 8.5 GPA while the elastic modulus experienced a decrease to around 5.5 GPa in samples above 3.1 Si:Al ratio. The Poisson’s ratio for each sample decreased proportionally to the Si:Al ratio with a maximum value of 0.22 and a minimum value of 0.05.

Computation of Linear Elastic Properties from Microtomographic Images: Methodology and Agreement between Theory and Experiment

Arns, Christoph; Knackstedt, Mark; Pinczewski, Wolf Val; Garboczi, Edward J
Fonte: Society of Exploration Geophysicists Publicador: Society of Exploration Geophysicists
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
56.22%
Elastic property-porosity relationships are derived directly from microtomographic images. This is illustrated for a suite of four samples of Fontainebleau sandstone with porosities ranging from 7.5% to 22%. A finite-element method is used to derive the elastic properties of digitized images. By estimating and minimizing several sources of numerical error, very accurate predictions of properties are derived in excellent agreement with experimental measurements over a wide range of the porosity. We consider the elastic properties of the digitized images under dry, water-saturated, and oil-saturated conditions. The observed change in the elastic properties due to fluid substitution is in excellent agreement with the exact Gassmann's equations. This shows both the accuracy and the feasibility of combining microtomographic images with elastic calculations to accurately predict petrophysical properties of individual rock morphologies. We compare the numerical predictions to various empirical, effective medium and rigorous approximations used to relate the elastic properties of rocks to porosity under different saturation conditions.

MEASUREMENT OF ELASTIC PROPERTIES OF MATERIALS BY THE ULTRASONIC THROUGH-TRANSMISSION TECHNIQUE

FRANCO,EDIGUER E; MEZA,JUAN M.; BUIOCHI,FLÁVIO
Fonte: DYNA Publicador: DYNA
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/08/2011 EN
Relevância na Pesquisa
66.12%
The elastic mechanical behavior of elastic materials is modeled by a pair of independent constants (Young's modulus and Poisson's coefficient). A precise measurement for both constants is necessary in some applications, such as the quality control of mechanical elements and standard materials used for the calibration of some equipment. Ultrasonic techniques have been used because wave velocity depends on the elastic properties of the propagation medium. The ultrasonic test shows better repeatability and accuracy than the tensile and indentation test. In this work, the theoretical and experimental aspects related to the ultrasonic through-transmission technique for the characterization of elastic solids is presented. Furthermore, an amorphous material and some polycrystalline materials were tested. Results have shown an excellent repeatability and numerical errors that are less than 3% in high-purity samples.