Examinando por Materia "Computerized tomography"
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Ítem Designed for resistance to puncture: The dynamic response of fish scales(ELSEVIER SCIENCE BV, 2019-01-01) Ghods S.; Murcia S.; Ossa E.A.; Arola D.; Ghods S.; Murcia S.; Ossa E.A.; Arola D.; Universidad EAFIT. Departamento de Ingeniería de Producción; Materiales de IngenieríaNatural dermal armors are serving as a source of inspiration in the pursuit of “next-generation” structural materials. Although the dynamic strain response of these materials is arguably the most relevant to their performance as armors, limited work has been performed in this area. Here, uniaxial tension and transverse puncture tests were performed on specimens obtained from the scales of Asian carp over strain rates spanning seven decades, from 10-4 to 103 s-1. The importance of anatomical variations was explored by comparing the performance of scales from the head, middle and tail regions. In both loading orientations, the scales exhibited a significant increase in the resistance to failure with loading rate. The rate sensitivity was substantially higher for transverse loading than for in-plane tension, with average strain rate sensitivity exponents for measures of the toughness of 0.35 and 0.08, respectively. Spatial variations in the properties were largest in the puncture responses, and scales from the head region exhibited the greatest resistance to puncture overall. The results suggest that the layered microstructure of fish scales is most effective at resisting puncture, rather than in-plane tension, and its effectiveness increases with rate of loading. X-ray microCT showed that delamination of plies in the internal elasmodine and stretching of the fibrils were key mechanisms of energy dissipation in response to puncture loading. Understanding contributions from the microstructure to this behavior could guide the development of flexible engineered laminates for penetration resistance and other related applications. © 2018 Elsevier LtdÍtem Diseño y manufactura de un implante personalizado de cráneo(SPRINGER, 2013-01-01) Isaza, J.F.; Correa, S.; Franco, J.M.; Torres, C.; Bedoya, B.; Universidad EAFIT. Departamento de Ingeniería Mecánica; Bioingeniería GIB (CES – EAFIT)This paper describes the methodology used to design a custom-made cranial implant for a 26 year-old patient, who suffered a lesion in the left frontoparietal region of the skull caused by a fibrous dysplasia. The design of the implant was carried out from the 3D reconstruction of the skull of the patient, obtained by a CT- Scan, using Rapid Form 2006. Once the preliminary design was obtained, 3D models of the injured region of the skull and implant were fabricated in a Rapid Prototyping (RP) machine using the Fused Deposition Modeling Technology (FDM) with the purpose of making a functional and dimensional validation of the implant. Subsequently, the implant was fabricated in titanium alloy (Ti6Al4V). With the methodology, the prosthesis was successfully implanted. The surgical time decreased by 50%, compared with the same type of surgery in which standard commercial implants and titanium meshes are used; due, principally, to the need of implementing trial and error procedures, which intend to achieve a good fit of the implant increasing the risk of the patient. Finally, the aesthetic appearance of the patient was recovered, allowing the patient to safely perform daily activities. © 2013 Springer.Ítem Diseño y manufactura de un implante personalizado de cráneo(SPRINGER, 2013-01-01) Isaza, J.F.; Correa, S.; Franco, J.M.; Torres, C.; Bedoya, B.This paper describes the methodology used to design a custom-made cranial implant for a 26 year-old patient, who suffered a lesion in the left frontoparietal region of the skull caused by a fibrous dysplasia. The design of the implant was carried out from the 3D reconstruction of the skull of the patient, obtained by a CT- Scan, using Rapid Form 2006. Once the preliminary design was obtained, 3D models of the injured region of the skull and implant were fabricated in a Rapid Prototyping (RP) machine using the Fused Deposition Modeling Technology (FDM) with the purpose of making a functional and dimensional validation of the implant. Subsequently, the implant was fabricated in titanium alloy (Ti6Al4V). With the methodology, the prosthesis was successfully implanted. The surgical time decreased by 50%, compared with the same type of surgery in which standard commercial implants and titanium meshes are used; due, principally, to the need of implementing trial and error procedures, which intend to achieve a good fit of the implant increasing the risk of the patient. Finally, the aesthetic appearance of the patient was recovered, allowing the patient to safely perform daily activities. © 2013 Springer.Ítem Geometry simplification of open-cell porous materials for elastic deformation FEA(SPRINGER, 2019-01-01) Cortés C.; Osorno M.; Uribe D.; Steeb H.; Ruiz-Salguero O.; Barandiarán I.; Flórez J.; Universidad EAFIT. Departamento de Ingeniería Mecánica; Laboratorio CAD/CAM/CAEEstimation of mechanical properties of porous materials is central for their medical and industrial application. However, the massive size of accurate boundary representations (B-Rep) of the foams makes the numerical estimations intractable. Even for small domain sizes, the mesh generation for finite element analysis (FEA) may not terminate. Current efforts for simulating porous materials use statistical predictions of the material structure. The simulated and actual materials present different geometry and topology, with consequences on the simulation results. To overcome these limitations, this manuscript presents a method, which (1) synthesizes an accurate truss abstraction from the raw geometry data, (2) executes efficient FEA simulations, and (3) processes nodal displacements to estimate apparent mechanical moduli of the porous material. The method addresses materials whose ligaments have circular cross-sections. The iso-surface present in the Computer Tomography (CT) scan of the porous material is used to synthesize a truss graph whose edges are truncated cones. Then, optimization and simplification methods are applied to produce a topologically and geometrically correct truss representation for the foam domain. Comparative FEA load simulations are conducted between the full B-Rep and truss representations of the material. The truss model proves to be significantly more efficient for FEA, departing from the Full B-Rep FEA by a maximum of 16% in the estimation of equivalent mechanical moduli. Geometric assessments such as porosity and Hausdorff distance confirm that the truss abstraction is a cost-effective one. Ongoing efforts concentrate on point set geometric algorithms for enforcement of standardized material testing. © 2018 Springer-Verlag London Ltd., part of Springer NatureÍtem 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 Volumetric non-local-means based speckle reduction for optical coherence tomography(OSA - The Optical Society, 2018-07-01) Cuartas-Vélez, C.; Restrepo, R.; Bouma, B.E.; Uribe-Patarroyo, N.; Universidad EAFIT. Departamento de Ciencias Básicas; Óptica AplicadaWe present a novel tomographic non-local-means based despeckling technique, TNode, for optical coherence tomography. TNode is built upon a weighting similarity criterion derived for speckle in a three-dimensional similarity window. We present an implementation using a two-dimensional search window, enabling the despeckling of volumes in the presence of motion artifacts, and an implementation using a three-dimensional window with improved performance in motion-free volumes. We show that our technique provides effective speckle reduction, comparable with B-scan compounding or out-of-plane averaging, while preserving isotropic resolution, even to the level of speckle-sized structures. We demonstrate its superior despeckling performance in a phantom data set, and in an ophthalmic data set we show that small, speckle-sized retinal vessels are clearly preserved in intensity images en-face and in two orthogonal, cross-sectional views. TNode does not rely on dictionaries or segmentation and therefore can readily be applied to arbitrary optical coherence tomography volumes. We show that despeckled esophageal volumes exhibit improved image quality and detail, even in the presence of significant motion artifacts. © 2018 Optical Society of America under the terms of the OSA Open Access Publishing Agreement.