Examinando por Materia "Mechanical behavior"
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Ítem Development of as-cast dual matrix structure (DMS) ductile iron(ELSEVIER SCIENCE SA, 2013-03-20) Murcia, S. C.; Paniagua, M. A.; Ossa, E. A.; Murcia, S. C.; Paniagua, M. A.; Ossa, E. A.; Universidad EAFIT. Departamento de Ingeniería de Producción; Materiales de IngenieríaDuctile iron is widely used due to its low cost and higher ductility than other cast irons. There has been an increased interest during the last years in improving the strength of these materials by means of heat-treating to obtain dual matrix structures (DMS) that enhance the properties found in Austempered Ductile Irons (ADI). This work studies the fabrication of DMS ductile cast irons with martensitic and bainitic structures in the as-cast condition, reducing costs related to heat treating processing while improving the mechanical behavior of the material. Cast irons alloyed with nickel ranging from 0% up to 7% were produced in order to evaluate the effect of Ni-Mo content on the phase transformations and mechanical properties of the material. The effect of cooling rate in phase transformations and mechanical properties were studied using molds with different wall thicknesses, finding that addition of Nickel and Molybdenum improves substantially the strength of the as-cast ductile iron, making unnecessary any further heat treating according to the level of properties desired. © 2012 Elsevier B.V.Ítem Effect of chemical composition and microstructure on the mechanical behavior of fish scales from Megalops Atlanticus(ELSEVIER SCIENCE BV, 2016-03-01) 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 IngenieríaThis paper presents an experimental study of the composition, microstructure and mechanical behavior of scales from the Megalops Atlanticus (Atlantic tarpon). The microstructure and composition were evaluated by Scanning Electron Microscopy (SEM) and RAMAN spectroscopy, respectively. The mechanical properties were evaluated in uniaxial tension as a function of position along the length of the fish (head, mid-length and tail). Results showed that the scales are composed of collagen and hydroxyapatite, and these constituents are distributed within three well-defined layers from the bottom to the top of the scale. The proportion of these layers with respect to the total scale thickness varies radially. The collagen fibers are arranged in plies with different orientations and with preferred orientation in the longitudinal direction of the fish. Results from the tensile tests showed that scales from Megalops Atlanticus exhibit variations in the elastic modulus as a function of body position. Additional testing performed with and without the highly mineralized top layers of the scale revealed that the mechanical behavior is anisotropic and that the highest strength was exhibited along the fish length. Furthermore, removing the top mineralized layers resulted in an increase in the tensile strength of the scale. © 2015 Elsevier Ltd.Ítem Effects of polar solvents on the mechanical behavior of fish scales(Elsevier Ltd, 2016-04-01) Murcia S; Li G; Yahyazadehfar M; Sasser M; Ossa A; Arola D; Murcia S; Li G; Yahyazadehfar M; Sasser M; Ossa A; Arola D; Universidad EAFIT. Departamento de Ingeniería de Producción; Materiales de IngenieríaFish scales are unique structural materials that serve as a form of natural armor. In this investigation the mechanical behavior of scales from the Cyprinus carpio was evaluated after exposure to a polar solvent. Uniaxial tensile and tear tests were conducted on specimens prepared from the scales of multiple fish extracted from near the head, middle and tail regions, and after exposure to ethanol for periods from 0 to 24 h. Submersion in ethanol caused instantaneous changes in the tensile properties regardless of anatomical site, with increases in the elastic modulus, strength and modulus of toughness exceeding 100%. The largest increase in properties overall occurred in the elastic modulus of scales from the tail region and exceeded 200%. Although ethanol treatment had significant effect on the tensile properties, it had limited influence on the tear resistance. The contribution of ethanol to the mechanical behavior appears to be derived from an increase in the degree of interpeptide hydrogen-bonding of the collagen molecules. Spatial variations in the effects of ethanol exposure on the mechanical behavior arise from the differences in degree of mineralization and lower mineral content in scales of the tail region. (C) 2015 Elsevier B.V. All rights reserved.Ítem Modelación micromecánica de polímeros reforzados con partículas(IMPRENTA UNIV ANTIOQUIA, 2010-01-01) Henao, E.A.O.; Henao, E.A.O.; Universidad EAFIT. Departamento de Ingeniería de Producción; Materiales de IngenieríaThis work describes an easy to use constitutive model able to predict the mechanical behavior of polymer matrix particulate composites at temperatures above the glass transition temperature Tg. This model was based on both phenomenological and micromechanical theories. With the model proposed it is possible to obtain the properties of the material (macro) using the characteristics of its components (micro). This model exhibits a reasonable agreement with experiments under various volume fractions of particles.Ítem Modeling added spatial variability due to soil improvement: Coupling FEM with binary random fields for seismic risk analysis(Elsevier Ltd, 2018-01-01) Montoya-Noguera, Silvana; Lopez-Caballero, Fernando; Mecánica AplicadaA binary mixture homogenization model is proposed for predicting the effects on liquefaction-induced settlement after soil improvement based on the consideration of the added spatial variability between the natural and the treated soil. A 2D finite element model of an inelastic structure founded on a shallow foundation was coupled with a binary random field. Nonlinear soil behavior is used and the model is tested for different mesh size, model parameters and input motions. Historical evidence as well as physical and numerical modeling indicate that improved sites present less liquefaction and ground deformation. In most cases this improvement is modeled as homogeneous; however, in-situ measurements evidence the high level of heterogeneity in the deposit. Inherent spatial variability in the soil and the application of some soil improvement techniques such as biogrouting and Bentonite permeations will necessary introduce heterogeneity in the soil deposit shown as clusters of the treated material in the natural soil. Hence, in this study, improvement zones are regarded as a two-phase mixture that will present a nonlinear relation due to the level of complexity of seismic liquefaction and the consequent settlement in a structure. This relation is greatly affected by the mechanical behavior of the soils used and the input motion. The effect on the latter can be efficiently related to the equivalent wave period as the proposed homogenization model depends on the stiffness demand of the input motion. © 2017 Elsevier LtdÍtem Quantifying the effects of thermal stress on the mechanical behavior of cretaceous source rocks in the Middle Magdalena Valley basin, Colombia(Universidad EAFIT, 2022) Meza Pemberti, Alejandro; Beltrán Triviño, Alejandro; Páez Reyes, ManuelÍtem 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 Ltd