Examinando por Materia "Elastic moduli"
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Ítem Correlations between thermal and tensile behavior with friction coefficient in copolyamides 6/12(Elsevier Ltd, 2017-02-15) Álvarez-Láinez, M.L.; Palacio R., J.A.; Universidad EAFIT. Departamento de Ingeniería de Diseño; Ingeniería de Diseño (GRID)Although polyamide 6 (PA6) obtained from e-caprolactame (CL) is an engineering polymer with outstanding properties used in sliding applications, it exhibits low impact strength and high water absorption. Those are some of the reasons why copolymerization between CL and laurolactame (LL) is desired. In this work, copolymers from 0–100 wt% LL are prepared to evaluate crystallinity, melting behavior, tensile properties and those properties are correlated with coefficient of friction. Experimental results show that PA6 (0 wt%) crystallinity and elasticity modulus are higher than those obtained from 100 wt%LL (PA12), but friction coefficient in PA6 is lower than that of PA12. While with 60 wt% LL crystallinity and elastic modulus reach a minimum value, with 350% elongation and coefficient of friction they register a maximum value. Our results suggest that crystallinity and elastic modulus are opposed to coefficient of friction. The absence of hydrogen bonds produces irregularities in the chain, reducing the crystal formation; such behavior is a consequence of copolymerization. Our findings will help to customize copolyamide, modulate the response between mechanical properties and friction behavior, as well as evaluate when it is necessary to add lubricants in the copolymer formulations. © 2016 Elsevier B.V.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.; Universidad EAFIT. Departamento de Ciencias; Ciencias Biológicas y Bioprocesos (CIBIOP)In 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 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 FE-simulations with a simplified model for open-cell porous materials: A Kelvin cell approach(IOS Press, 2019-01-01) Montoya-Zapata D.; Cortés C.; Ruiz-Salguero O.; Universidad EAFIT. Departamento de Ingeniería Mecánica; Laboratorio CAD/CAM/CAEIn in-silico estimation of mechanical properties of open (Kelvin) cell porous materials, the geometrical model is intractable due to the large number of finite elements generated. Such a limitation impedes the study of reasonable domains. VoXel or Boundary representations of the porous domain result in FEA data sets which do not pass the stage of mesh generation, even for very modest domains. Our method to overcome such limitations partially replaces geometrical minutiae with kinematical constraints imposed on cylindrical bars (i.e. Truss model). Our implemented method uses node position equality constraints augmented with rotation constraints at the joints. Such a method significantly reduces the computational expense of the model, allowing the study of domains of 103 Kelvin cells. The results of the tests executed show the accuracy and efficiency of the Truss model in the estimation of Young's modulus and Poisson's ratio when compared with current procedures. The method allows application for materials which depart from Kelvin Cell uniformity, since the Truss model admits general configurations. As the simulation is made possible by the Truss model, new challenges appear, such as the application to anisotropic materials and the automatic generation of the Truss model from actual foam scans (e.g. tomographies). © 2019 - IOS Press and the authors. All rights reserved.Ítem Zylerberg, 1985 Contributions of the layer topology and mineral content to the elastic modulus and strength of fish scales(ELSEVIER SCIENCE BV, 2018-02-01) Murcia, S.; Miyamoto, Y.; Varma, M.P.; Ossa, A.; Arola, D.Fish scales are an interesting natural structural material and their functionality requires both flexibility and toughness. Our previous studies identified that there are spatial variations in the elastic properties of fish scales corresponding to the anatomical regions, and that they appear to be attributed to changes in the microstructure. In the present study, a model is proposed that describes the elastic behavior of elasmoid fish scales in terms of the relative contributions of the limiting layer and both the internal and external elasmodine. The mechanical properties of scales from the Megalops atlanticus (i.e. tarpon) were characterized in tension and compared with predictions from the model. The average error between the predicted and the experimental properties was 7%. It was found that the gradient in mineral content and aspect ratio of the apatite crystals in the limiting layer played the most important roles on the elastic modulus of the scales. Furthermore, misalignment of plies in the external elasmodine from the longitudinal direction was shown to reduce the elastic modulus significantly. This is one approach for modulating the fish scale flexibility for a high mineral content that is required to increase the resistance to puncture. © 2017