Examinando por Materia "Porosity"
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Ítem Análisis y comparación entre el proceso de centrifugado e inyección para la fabricación de piezas en Zamac(Universidad EAFIT, 2008) Gallego Alzate, Andrés Felipe; Paniagua Villa, Marco AurelioÍtem Cerámicos de alta resistencia inspirados en nuestra naturaleza(Universidad EAFIT, 2020-12-01) Martinez Guerrero, Christian Alexander; Martinez-Guerrero, Christian Alexander; Gil Duran, S.; Arola, D.; Ossa, Edgar; Materiales de IngenieríaÍtem A comparative computational study of blood flow pattern in exemplary textile vascular grafts(Taylor and Francis Ltd., 2018-01-01) Valencia, R.A.; García, M.J.; Bustamante, J.; Mecánica AplicadaTextile vascular grafts are biomedical devices and play an important role serving as a solution for the partial replacement of damaged arterial vessels. It is believed that the success of a textile vascular graft, in the healing process after implantation, is due to the porous micro-structure of the wall. Although the transport of fluids through textiles is of great technical interest in biomedical applications, little is known about predicting the micro-flow pattern and cellular transport through the wall. The aim of this work is to investigate how the type of fabric, permeability and porosity affect both the local fluid dynamics at several scales and the fluid-particle interaction between platelets in textile grafts, related with the graft occlusion. This study involves both experimental and computational tests. Experimental tests are performed to characterize the permeability and porosity according to the ISO 7198 standard. The numerical process is based on a multi-scale approach where the fluid flow is solved with the Finite Element Method and the discrete particles are solved with the Molecular Dynamic Method. The results have shown that the type of fabric in textile vascular grafts and the degree of porosity and permeability affect both the local fluid dynamics and the level of penetration of platelets through the wall, thus indicating their importance as design parameters. © 2017 Informa UK Limited, trading as Taylor & Francis Group.Ítem A comparative computational study of blood flow pattern in exemplary textile vascular grafts(Taylor and Francis Ltd., 2018-01-01) R. VALENCIA; M. GARCÍA; J. BUSTAMANTE; R. VALENCIA; M. GARCÍA; J. BUSTAMANTE; Universidad EAFIT. Departamento de Humanidades; Centro de Estudios Urbanos y Ambientales (URBAM)Textile vascular grafts are biomedical devices and play an important role serving as a solution for the partial replacement of damaged arterial vessels. It is believed that the success of a textile vascular graft, in the healing process after implantation, is due to the porous micro-structure of the wall. Although the transport of fluids through textiles is of great technical interest in biomedical applications, little is known about predicting the micro-flow pattern and cellular transport through the wall. The aim of this work is to investigate how the type of fabric, permeability and porosity affect both the local fluid dynamics at several scales and the fluid-particle interaction between platelets in textile grafts, related with the graft occlusion. This study involves both experimental and computational tests. Experimental tests are performed to characterize the permeability and porosity according to the ISO 7198 standard. The numerical process is based on a multi-scale approach where the fluid flow is solved with the Finite Element Method and the discrete particles are solved with the Molecular Dynamic Method. The results have shown that the type of fabric in textile vascular grafts and the degree of porosity and permeability affect both the local fluid dynamics and the level of penetration of platelets through the wall, thus indicating their importance as design parameters. © 2017 Informa UK Limited, trading as Taylor & Francis Group.Ítem Digital material laboratory: Wave propagation effects in open-cell aluminium foams(Elsevier, 2012-09) Saenger, E.H.; Uribe, D.; Jänicke, R.; Ruíz, O.; Steeb, H.; Universidad EAFIT. Departamento de Ingeniería Mecánica; Laboratorio CAD/CAM/CAEThis paper is concerned with numerical wave propagation effects in highly porous media using digitized images of aluminum foam -- Starting point is a virtual material laboratory approach -- The Aluminum foam microstructure is imaged by 3D X-ray tomography -- Effective velocities for the fluid-saturated media are derived by dynamic wave propagation simulations -- We apply a displacement-stress rotated staggered fnite-difference grid technique to solve the elastodynamic wave equation -- The used setup is similar to laboratory ultrasound measurements and the computed results are in agreement with our experimental data -- Theoretical investigations allow to quantify the influence of the interaction of foam and fluid during wave propagation – Together with simulations using an artificial dense foam we are able to determine the tortuosity of aluminum foamÍtem Efecto del tratamiento térmico sobre la densidad y la respuesta electromecánica de una porcelana para aisladores de media tensión(Universidad EAFIT, 2023) Echeverry Otálvaro, Deysi Yuliet; Ossa Henao, Edgar AlexanderÍtem Estimation of large domain Al foam permeability by Finite Difference methods(WILEY-VCH Verlag, 2013) Osorno, María; Steeb, Holger; Uribe, David; Ruíz, Óscar; Universidad EAFIT. Departamento de Ingeniería Mecánica; Laboratorio CAD/CAM/CAEClassical methods to calculate permeability of porous media have been proposed mainly for high density (e.g. granular) materials -- These methods present shortcomings in high porosity, i.e. high permeability media (e.g. metallic foams) -- While for dense materials permeability seems to be a function of bulk properties and occupancy averaged over the volume, for highly porous materials these parameters fail to predict it -- Several authors have attacked the problem by solving the Navier-Stokes equations for the pressure and velocity of a liquid flowing through a small domain (Ωs) of aluminium foam and by comparing the numerical results with experimental values (prediction error approx. 9%) -- In this article, we present calculations for much larger domains (ΩL) using the Finite Difference (FD) method, solving also for the pressure and velocity of a viscous liquid flowing through the Packed Spheres scenario -- The ratio Vol(ΩL)/Vol(Ωs) is around 103 -- The comparison of our results with the Packed Spheres example yields a prediction error of 5% for the intrinsic permeability -- Additionally, numerical permeability calculations have been performed for Al foam samples -- Our geometric modelling of the porous domain stems from 3D X-ray tomography, yielding voxel information, which is particularly appropriate for FD -- Ongoing work concerns the reduction in computing times of the FD method, consideration of other materials and fluids, and comparison with experimental dataÍtem Esto pasa cuando imitamos a la naturaleza(2020-12-01) Martinez Guerrero, Christian Alexander; Christian Alexander Martinez-Guerrero; Gil Duran, S; Arola, D; Ossa, E.A; Vicerrectoría de Descubrimiento y CreaciónÍtem ¡Esto pasa cuando nos inspiramos en la naturaleza!(2020-12-01) Martinez Guerrero, Christian Alexander; Christian Alexander Martinez-Guerrero; Arola, D; Ossa, E.A; Gil Duran, SÍtem Finite difference calculations of permeability in large domains in a wide porosity range(Springer Verlag, 2015-08-01) Osorno, M.; Uribe, D.; Ruiz, O.E.; Steeb, H.; Universidad EAFIT. Departamento de Ingeniería Mecánica; Laboratorio CAD/CAM/CAEDetermining effective hydraulic, thermal, mechanical and electrical properties of porous materials by means of classical physical experiments is often time-consuming and expensive. Thus, accurate numerical calculations of material properties are of increasing interest in geophysical, manufacturing, bio-mechanical and environmental applications, among other fields. Characteristic material properties (e.g. intrinsic permeability, thermal conductivity and elastic moduli) depend on morphological details on the porescale such as shape and size of pores and pore throats or cracks. To obtain reliable predictions of these properties it is necessary to perform numerical analyses of sufficiently large unit cells. Such representative volume elements require optimized numerical simulation techniques. Current state-of-the-art simulation tools to calculate effective permeabilities of porous materials are based on various methods, e.g. lattice Boltzmann, finite volumes or explicit jump Stokes methods. All approaches still have limitations in the maximum size of the simulation domain. In response to these deficits of the well-established methods we propose an efficient and reliable numerical method which allows to calculate intrinsic permeabilities directly from voxel-based data obtained from 3D imaging techniques like X-ray microtomography. We present a modelling framework based on a parallel finite differences solver, allowing the calculation of large domains with relative low computing requirements (i.e. desktop computers). The presented method is validated in a diverse selection of materials, obtaining accurate results for a large range of porosities, wider than the ranges previously reported. Ongoing work includes the estimation of other effective properties of porous media. © 2015, Springer-Verlag Berlin Heidelberg.Ítem Hardness of thermal sprayed coatings: Relevance of the scale of measurement(ELSEVIER SCIENCE SA, 2015-04-25) Chicot, D.; Ageorges, H.; Voda, M.; Louis, G.; Ben Dhia, M.A.; Palacio, C.C.; Kossman, S.; Universidad EAFIT. Departamento de Ciencias Básicas; Electromagnetismo Aplicado (Gema)The coatings obtained by thermal spraying can present a large variety of geometrical parameters (thickness, roughness...), of microstructures (constituents, nature of phases...), of mechanical properties (hardness, elastic modulus...) and of morphological defects (cracks, pores...) depending on the spraying conditions. In order to determine the mechanical properties of the coating, one of the most relevant techniques is probably the instrumented indentation test. Nowadays this technique is very attractive since it allows the determination of numerous parameters. Moreover, recent developments allow the use of a phenomenological approach and modeling at different scales of measurement, from nano (even ultra-nano) to macro scale, i.e. from few milligrams to several kilograms of loading. However, the information, which can be extracted at the different regimes of loading can be the same or lead to different values of the mechanical properties, which can be complementary or contradictory depending on the nature of the coating and the preparation of the sample. For example, roughness, porosity and cracks present in the coating will affect the mechanical characterization since the indentation data analysis is based on how a rigid indenter penetrates into the material. So, an important question arises: Should the influence of these defects to be taken into account, or neglected, for the mechanical characterization? The present work proposes different methodologies for determining the hardness of coated materials by considering or not the influence of both the porosity and roughness of the surface. In the first part, results of microindentation experiments performed on the rough surface of alumina coatings are compared to those obtained on a polished cross-section. Although the surface of the cross-section is irregular even after caution polishing, the hardness can be measured. A decrease of about 30% of the hardness number on the cross-section is observed. The second part is related to the microstructured yttria-stabilized zirconia analysis. A methodology based on the indentation size effect analysis is presented to avoid the influence of roughness and the defects, which can be crossed by the indenter during the indentation. This methodology allows the hardness determination of the coating exempt of defects. In the last part, a statistical analysis using nanoindentation data resulting from the continuous stiffness measurement mode applied to nanostructured yttria-stabilized zirconia shows that, even if the hardness number varies to a great extent according to the applied load and the location of the indent, the hardness can be represented by means of a unique hardness number independent of the sense of the hardness variation during the indenter displacement. (C) 2014 Elsevier B.V. All rights reserved.Ítem Importance of tubule density to the fracture toughness of dentin(PERGAMON-ELSEVIER SCIENCE LTD, 2016-07-01) Montoya, C.; Arola, D.; Ossa, E.A.; Montoya, C.; Arola, D.; Ossa, E.A.; Universidad EAFIT. Departamento de Ingeniería de Producción; Materiales de IngenieríaObjective: The fracture toughness of dentin is critical to the prevention of tooth fracture. Within the tooth crown, the mechanical properties of dentin are influenced by spatial variations in the density and diameter of the dentin tubules with distance from the pulp. There are also relevant changes to the microstructure of dentin with age. In this investigation the importance of tubule density to the fracture toughness of dentin was evaluated in ``young'' and ``old'' age groups. Methods: The variations in microstructure (density and diameter of tubules) from young and old donor teeth were studied by means of optical microscopy. Results: A reduction in the density and diameter of tubules was identified to occur with aging. An approach previously proposed to study the mechanical behavior of porous materials was used to model the fracture toughness of coronal dentin in terms of the tubule characteristics. Results were then compared with published results from previous studies. Conclusions: The model predictions were consistent with experimental results for the fracture toughness of dentin from young donor teeth, but overestimated the values that have been reported for ``old'' dentin. (C) 2016 Elsevier Ltd. All rights reserved.Ítem Numerical estimation of carbonate properties using a digital rock physics workflow(EAGE Publishing BV, 2014-01-01) Osorno, M.; Uribe, D.; Saenger, E.H.; Madonna, C.; Steeb, H.; Ruiz, O.; Universidad EAFIT. Departamento de Ingeniería Mecánica; Laboratorio CAD/CAM/CAEDigital rock physics combines modern imaging with advanced numerical simulations to analyze the physical properties of rocks. In this paper we suggest a special segmentation procedure which is applied to a carbonate rock from Switzerland. Starting point is a CT-scan of a specimen of Hauptmuschelkalk. The first step applied to the raw image data is a non-local mean filter. We then apply different thresholds to identify pores and solid phases. Because we are aware of a non-neglectable amount of unresolved microporosity we also define intermediate phases. Based on this segmentation determine porosity-dependent values for the p-wave velocity and for the permeability. The porosity measured in the laboratory is then used to compare our numerical data with experimental data. We observe a good agreement. Future work includes an analytic validation to the numerical results of the p-wave velocity upper bound, employing different filters for the image segmentation and using data with higher resolution.Ítem Numerical simulations toward validating undrained conditions in Geotechnical Earthquake Engineering(Universidad EAFIT, 2016) Gómez Zuluaga, Jesús David; Restrepo Sánchez, Doriam LeidinLiquefaction denotes the loss of shear resistance of granular materials due to pore pressure build up during cyclic load -- Traditionally, liquefaction is considered as an undrained phenomenon -- Consequently, pore-fluid flow is deemed nonexistent during the cyclic response of sandy soils -- This paper aims to shed light on the validity of this hypothesis by examining the response of natural structures made of saturated porous material subjected to vertically incident plane waves -- The two porous structures, i.e., (i) an alluvial basin, and (ii) a surficial topography, are analyzed under single- and double-drainage regimes -- The results are obtained using a dynamic undrained formulation and compared against an u-p scheme -- This work provides evidence on the impact of drainage conditions, incident wavefront, frequency content, and type of natural structure, on the accuracy of the no volumetric change hypothesis -- On particular, our findings show that the undrained approach exhibits a better agreement for interior topography than for surficial irregularities -- Similarly, P-incident wavefronts tend to be better represented for the undrained hypothesis than SV incident waves -- Finally, our results prove that the undrained approximation provides better estimates for single-drainage conditions than for double-flow regimes