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Ítem Failure analysis of a civil aircraft landing gear(PERGAMON-ELSEVIER SCIENCE LTD, 2006-10-01) Ossa, Edgar Alexander; Ossa, Edgar Alexander; Universidad EAFIT. Departamento de Ingeniería de Producción; Materiales de IngenieríaÍtem Estudio comparativo de las propiedades mecánicas de fibras de vidrio y queratina(2007-09-01) Ossa, Edgar Alexander; Montoya, Carolina; Ossa, Edgar Alexander; Montoya, Carolina; Universidad EAFIT. Departamento de Ingeniería de Producción; Materiales de IngenieríaÍtem Material properties of the skull layers of the primate parietal bone: A single-subject study(Public Library of Science, 2020-01-01) Zapata, U.; Wang, Q.; Zapata, U.; Wang, Q.; Universidad EAFIT. Departamento de Ingeniería de Producción; Materiales de IngenieríaThe outer cortical table of the parietal bone has been commonly used as a calvarial bone graft site for the craniofacial reconstruction. However, little is known about how removing the outer table may affect the function and structure of the inner table, and how the knowledge of the biomechanics and material properties of cortical bones will help the calvarial graft to better integrate into the biological and mechanical functions of its surrounding native tissues. In this study, it was hypothesized that there were significant differences in both density and material properties between inner and outer cortical plates in cranial bones. Twelve cylindrical specimens, including inner-outer layers, of cortical parietal bone of a female baboon were collected. Cortical thicknesses and densities were measured, and elastic properties were assessed using an ultrasonic technique. Results demonstrated remarkable difference in both thickness (t = 8.248, p .0.05) and density (t = 4.926, p.0.05) between inner and outer cortical paired samples. Orthotropic characteristics of the cortical plates were detected as well, these findings suggest that there are differences in biomechanical properties between two surfaces of cranial bones at both tissue and organ levels. How these differences are linked to the stress environments of the inner and outer cranial cortical layers awaits further studies. Further study will greatly enhance our ability to address questions derived from both morphological and craniofacial medicine fields about the development and biomechanics of craniofacial skeletons. © 2020 Zapata, Wang.Ítem Compressive Deformation Behaviour of Asphalt Mixtures(Association of Asphalt Paving Technologist, 2006-08-01) Ossa, Edgar Alexander; Ossa, Edgar Alexander; Universidad EAFIT. Departamento de Ingeniería de Producción; Materiales de IngenieríaÍtem Seismic risk assessment for the residential buildings of the major three cities in Colombia: Bogotá, Medellín, and Cali(EARTHQUAKE ENGINEERING RESEARCH INST, 2020-01-01) Acevedo A.B.; Yepes-Estrada C.; González D.; Silva V.; Mora M.; Arcila M.; Posada G.; Acevedo A.B.; Yepes-Estrada C.; González D.; Silva V.; Mora M.; Arcila M.; Posada G.; Universidad EAFIT. Departamento de Ingeniería de Producción; Materiales de IngenieríaThis study presents a seismic risk assessment and a set of earthquake scenarios for the residential building stock of the three largest metropolitan centers of Colombia: Bogotá, Medellín and Cali (with 8.0, 2.5, and 2.4 million inhabitants, respectively). A uniform methodology was followed for the development of the seismic hazard, vulnerability, and exposure models, thus allowing a direct comparison between the seismic risk of the different cities. Risk metrics such as exceedance probability curves and average annual losses were computed for each city. The earthquake scenarios were selected considering events whose direct economic impact is similar to the aggregated loss for a probability of exceedance of 10% in 50 years. Results show a higher mean aggregate loss ratio for Cali and similar mean aggregate loss ratios for Bogotá and Medellín. All of the models used in this study are openly accessible, enabling risk modelers, engineers, and stakeholders to explore them for disaster risk management. © The Author(s) 2020.Ítem Contributions of the layer topology and mineral content to the elastic modulus and strength of fish scales(ELSEVIER SCIENCE BV, 2018-12-01) Ossa, Edgar Alexander; Ossa, Edgar Alexander; Universidad EAFIT. Departamento de Ingeniería de Producción; Materiales de IngenieríaÍtem Dilation behaviour of asphalt mixtures(Taylor and Francis Ltd., 2006-08-01) Ossa, Edgar Alexander; Ossa, Edgar Alexander; Universidad EAFIT. Departamento de Ingeniería de Producción; Materiales de IngenieríaÍtem Fragilidad y comportamiento mecánico del esmalte dental(2012-12-01) Ossa, Edgar Alexander; Ossa, Edgar Alexander; Universidad EAFIT. Departamento de Ingeniería de Producción; Materiales de IngenieríaÍtem Nature-Inspired Protecto-Flexible Impact-Tolerant Materials(Wiley-VCH Verlag, 2020-01-01) Estrada, S.; Ossa, A.; Estrada, S.; Ossa, A.; Universidad EAFIT. Departamento de Ingeniería de Producción; Materiales de IngenieríaThe search for impact-tolerant, light-weight flexible materials has challenged materials scientists and engineers for decades. In this quest, many researchers have focused on studying natural armor as a guide to propose bioinspired materials with enhanced properties. The energy dissipation and flexibility mechanisms activated at different hierarchical structural levels of natural systems are used here as a guide to improve the energy and flexibility of synthetic materials. In particular, fish scales and osteoderms are selected as proper biological models to develop a novel family of cost-effective bioinspired protecto-flexible (Pf) materials. Furthermore, a bullet-proof protecto-flexible prototype is manufactured and tested. The ballistic tests suggest that under real stringent conditions, the system is capable of absorbing high levels of energy while remaining flexible enough to allow movement to the user. Remarkably, the material system developed allows its implementation into realistic high volumes of production with low added costs. Consequently, the proposed strategy for developing bioinspired Pf materials will enable the development of the next generation of high-performance impact-resistant materials. © 2020 WILEY-VCH Verlag GmbH & Co. KGaA, WeinheimÍtem Contribution of Root Canal Treatment to the Fracture Resistance of Dentin(Elsevier Inc., 2019-01-01) Yan W.; Montoya C.; Øilo M.; Ossa A.; Paranjpe A.; Zhang H.; Arola D.D.; Yan W.; Montoya C.; Øilo M.; Ossa A.; Paranjpe A.; Zhang H.; Arola D.D.; Universidad EAFIT. Departamento de Ingeniería de Producción; Materiales de IngenieríaIntroduction: Although the strength and toughness of dentin decrease with age, no study has explored if restorative treatments are a contributing factor. Methods: Multiple extracted teeth were obtained from randomly selected donors and categorized according to donor age and prior root canal treatment. The microstructure and chemical composition of radicular dentin were evaluated using scanning electron microscopy and Raman spectroscopy, respectively, and the strength was evaluated in 4-point flexure to failure. Data were compared using the Student t test. Results: Dentin from the root canal–restored teeth exhibited significantly lower strength (P <.05) than tissue from age- and donor-matched unrestored tooth pairs. Although there was no significant difference in the mineral-to-collagen ratio between the 2 groups, dentin obtained from the root canal–treated teeth exhibited more extensive collagen cross-linking and lower tubule occlusion ratios than the unrestored tooth pairs. Conclusions: There is a decrease in the strength of radicular dentin with aging, but prior root canal treatment increases the extent of degradation. © 2018 American Association of EndodontistsÍtem Effect of the Low Concentration of Nitrates and Phosphates on the Accumulation of Astaxantin in Haematococcus pluvialis UTEX 2505(Centro de Informacion Tecnologica, 2019-02-12) Ossa, E.; Ossa, E.; Universidad EAFIT. Departamento de Ingeniería de Producción; Materiales de IngenieríaIn this study, the effect of the concentration of nitrogen and phosphorus on the accumulation of Astaxanthin in Haematococcus pluvialis UTEX 2505 was evaluated using a factorial 32 design.Ítem Control of Porosity in Freeze Casting(J O M Institute, 2020-01-01) Gil-Duran S.; Arola D.; Ossa E.A.; Gil-Duran S.; Arola D.; Ossa E.A.; Universidad EAFIT. Departamento de Ingeniería de Producción; Materiales de IngenieríaMany biologic structural materials have porous microstructures with a distribution and orientation of pores that are challenging to achieve using traditional methods of processing. In this investigation, numerical and experimental methods of evaluation were used to understand effects from the primary processing parameters on the temperature gradients during solidification in freeze casting of ceramics. The location and orientation of the temperature gradients were found to be highly dependent on the geometrical and thermal properties of the mold material used in processing. Furthermore, it was found that careful control of these processing variables can be used to design bioinspired porous materials with graded orientations and distributions of pores. © 2020, The Minerals, Metals & Materials Society.Ítem Bioinspired hierarchical impact tolerant materials(IOP PUBLISHING LTD, 2020-07-01) Estrada, Susana; Munera, Juan Camilo; Hernandez, Javier; Arroyave, Mauricio; Arola, Dwayne; Ossa, Alex; Estrada, Susana; Munera, Juan Camilo; Hernandez, Javier; Arroyave, Mauricio; Arola, Dwayne; Ossa, Alex; Universidad EAFIT. Departamento de Ingeniería de Producción; Materiales de IngenieríaThe quest for new light-weight materials with superior mechanical properties is a goal of materials scientists and engineers worldwide. A promising route in this pursuit is drawing inspiration from nature to design and develop materials with enhanced properties. By emulating the graded mineral content and hierarchical structure of fish scales of the Arapaima gigas from the nano to macro scales, we were able to develop bioinspired laminated composites with improved impact resistance. Activated by the addition of nano-particles of Al2O3 and nano-layers of TiN to a thermoplastic fiber substrate, new energy dissipation mechanisms operating at the nanoscale enhanced the energy absorption and stiffness of the bioinspired material. Remarkably, the newly developed materials are easily transferred to the industry with minimum associated manufacturing costs.Ítem Efecto de las Bajas Concentraciones de Nitratos y Fosfatos sobre la Acumulación de Astaxantina en Haematococcus pluvialis UTEX 2505(Centro de Informacion Tecnologica, 2019-01-01) Miranda A.M.; Ossa E.A.; Vargas G.J.; Sáez A.A.; Miranda A.M.; Ossa E.A.; Vargas G.J.; Sáez A.A.; Universidad EAFIT. Departamento de Ingeniería de Producción; Materiales de IngenieríaIn this study, the effect of the concentration of nitrogen and phosphorus on the accumulation of Astaxanthin in Haematococcus pluvialis UTEX 2505 was evaluated using a factorial 3 2 design. The dependent variables were cell growth, Astaxanthin production, lipid profile and Young's modulus of the cell membrane. It was found that cellular productivity increases when nitrogen levels were high, in contrast to low concentrations of nitrogen and phosphorus that showed a positive effect on Astaxanthin production. The stress generated by the source of nutrients decreases the rigidity of the cellular wall in the microalgae. As a conclusion, to obtain higher concentrations of Astaxanthin it is necessary to limit the nitrogen and phosphorus levels. © 2019 Centro de Informacion Tecnologica. All Rights Reserved.Ítem Improving the mechanical properties of commercial feldspathic dental porcelain by addition of Alumina-Zirconia(IMPRENTA UNIV ANTIOQUIA, 2020-01-01) Gomez Tamayo, Juliana; Rueda Arango, Astrid Oasis; Ossa Henao, Edgar Alexander; Gomez Tamayo, Juliana; Rueda Arango, Astrid Oasis; Ossa Henao, Edgar Alexander; Universidad EAFIT. Departamento de Ingeniería de Producción; Materiales de IngenieríaDental ceramics made from Yttria stabilized tetragonal Zirconia polycrystalline (Y-TZP) with feldspathic porcelain veneers have similar mechanical and aesthetic response to natural tooth. However, cases of early failure, such as chipping or fracture in the veneering have been reported after short periods of use. The present study evaluated the feldspathic porcelain (VITA-VM9) with addition of 0.5 and 2.5 wt% Alumina-Zirconia as reinforcing agents. Hardness, fracture toughness, contact resistance and color variations were evaluated finding better mechanical performance on the new formulations.Ítem Contributions of intermolecular bonding and lubrication to the mechanical behavior of a natural armor(ELSEVIER SCI LTD, 2020-01-01) Jiang, H.; Ghods, S.; Weller, E.; Waddell, S.; Ossa, E.A.; Yang, F.; Arola, D.; Jiang, H.; Ghods, S.; Weller, E.; Waddell, S.; Ossa, E.A.; Yang, F.; Arola, D.; Universidad EAFIT. Departamento de Ingeniería de Producción; Materiales de IngenieríaAmong many dermal armors, fish scales have become a source of inspiration in the pursuit of “next-generation” structural materials. Although fish scales function in a hydrated environment, the role of water and intermolecular hydrogen bonding to their unique structural behavior has not been elucidated. Water molecules reside within and adjacent to the interpeptide locations of the collagen fibrils of the elasmodine and provide lubrication to the protein molecules during deformation. We evaluated the contributions of this lubrication and the intermolecular bonding to the mechanical behavior of elasmodine scales from the Black Carp (Mylopharyngodon piceus). Scales were exposed to polar solvents, followed by axial loading to failure and the deformation mechanisms were characterized via optical mechanics. Displacement of intermolecular water molecules by liquid polar solvents caused significant (p = 0.05) increases in stiffness, strength and toughness of the scales. Removal of this lubrication decreased the capacity for non-linear deformation and toughness, which results from the increased resistance to fibril rotations and sliding caused by molecular friction. The intermolecular lubrication is a key component of the “protecto-flexibility” of scales and these natural armors as a system; it can serve as an important component of biomimetic-driven designs for flexible armor systems. Statement of Significance: The natural armor of fish has become a topic of substantial scientific interest. Hydration is important to these materials as water molecules reside within the interpeptide locations of the collagen fibrils of the elasmodine and provide lubrication to the protein molecules during deformation. We explored the opportunity for tuning the mechanical behavior of scales as a model for next-generation engineering materials by adjusting the extent of hydrogen bonding with polar solvents and the corresponding interpeptide molecular lubrication. Removal of this lubrication decreased the capacity for non-linear deformation and toughness due to an increase in resistance to fibril rotations and sliding as imparted by molecular friction. We show that intermolecular lubrication is a key component of the “protecto-flexibility” of natural armors and it is an essential element of biomimetic approaches to develop flexible armor systems. © 2020 Acta Materialia Inc.Ítem Polietileno tereftalato como reemplazo parcial del agregado fino en mezclas de concreto(Universidad de Medellín, 2019-06-28) Acevedo, A.; Acevedo, A.; EAFIT University; Universidad EAFIT; Universidad EAFIT. Departamento de Ingeniería de Producción; Materiales de IngenieríaÍtem Time-dependent Mechanical Response at the Nanoscale(Elsevier B.V., 2020-01-01) Múnera, J.C.; Goswami, D.; Martinez, R.V.; Ossa, E.A.; Múnera, J.C.; Goswami, D.; Martinez, R.V.; Ossa, E.A.; Universidad EAFIT. Departamento de Ingeniería de Producción; Materiales de IngenieríaModern nanofabrication processes on metals, polymers, and ceramics often require deforming these materials at strain rates ranging ~101 – 107 s–1. Therefore, there is a need to develop an appropriate methodology capable of measuring and predicting the effects of these deformation rates on the final mechanical response of the nanomaterial being processed. Here we report an experimental study of the indentation response of three materials with different nature and mechanical properties, but with known time-dependent mechanical responses. These materials allow validation of the findings under a wide variety of conditions. One metal (Pb), and two polymers (PMMA and PS), were indented at the sub-20 nm scale using commercial atomic force microscopy (AFM) probes. Based on our experimental findings, we also propose an analytical model for creeping solids in which their nanoscale mechanical behavior is completely described by two components: an elastic component (characterized by the Hertz contact model) and a time-dependent component (characterized by a power-law model). The proposed experimental protocol is easy to implement, and the analytical model can be extended to a large variety of materials. The ability to characterize the time-dependence of the mechanical response of different materials at the nanoscale will enable a better estimation of the effect of manufacturing processes on the properties and performance of nanomaterials. © 2020 Elsevier LtdÍtem Interfibril hydrogen bonding improves the strain-rate response of natural armour(Royal Society Publishing, 2019-01-01) Arola D.; Ghods S.; Son C.; Murcia S.; Ossa E.A.; Arola D.; Ghods S.; Son C.; Murcia S.; Ossa E.A.; Universidad EAFIT. Departamento de Ingeniería de Producción; Materiales de IngenieríaFish scales are laminated composites that consist of plies of unidirectional collagen fibrils with twisted-plywood stacking arrangement. Owing to their composition, the toughness of scales is dependent on the intermolecular bonding within and between the collagen fibrils. Adjusting the extent of this bonding with an appropriate stimulus has implications for the design of next-generation bioinspired flexible armours. In this investigation, scales were exposed to environments of water or a polar solvent (i.e. ethanol) to influence the extent of intermolecular bonding, and their mechanical behaviour was evaluated in uniaxial tension and transverse puncture. Results showed that the resistance to failure of the scales increased with loading rate in both tension and puncture and that the polar solvent treatment increased both the strength and toughness through interpeptide bonding; the largest increase occurred in the puncture resistance of scales from the tail region (a factor of nearly 7). The increase in strength and damage tolerance with stronger intermolecular bonding is uncommon for structural materials and is a unique characteristic of the low mineral content. Scales from regions of the body with higher mineral content underwent less strengthening, which is most likely the result of interference posed by the mineral crystals to intermolecular bonding. Overall, the results showed that flexible bioinspired composite materials for puncture resistance should enrol constituents and complementary processing that capitalize on interfibril bonds. © 2019 The Author(s) Published by the Royal Society. All rights reserved.Ítem Chemical, structural and mechanical characterization of bovine enamel(PERGAMON-ELSEVIER SCIENCE LTD, 2020-01-01) Arango-Santander S.; Montoya C.; Pelaez-Vargas A.; Ossa E.A.; Arango-Santander S.; Montoya C.; Pelaez-Vargas A.; Ossa E.A.; Universidad EAFIT. Departamento de Ingeniería de Producción; Materiales de IngenieríaObjective: The purpose of this investigation was to establish microstructure, microhardness, fracture toughness, chemical composition, and crack repair of bovine enamel and to compare these features with their human counterparts. Design: Bovine enamel fragments were prepared and optical microscopy and atomic force microscopy were used to establish microstructure; Raman spectroscopy was used to estimate composition and microindentation using Vickers testing was performed to evaluate hardness. Results: A strong dependence between indentation load and microhardness values was observed, as was the case in human enamel. Similar microstructure and chemical composition between bovine and human enamel, 7.89% lower microhardness and 40% higher fracture toughness values for bovine enamel were found. Conclusion: From a structural and mechanical standpoint, bovine enamel is a suitable alternative to human enamel for in vitro testing of dental products. © 2019 Elsevier Ltd