Recursos de colección

Archivo Digital UPM (109.492 recursos)

This is an institutional repository providing access to the research output of the institution. Primarily contains thesis.

Materia = Materiales

Mostrando recursos 1 - 20 de 1.034

  1. Incorporación del reparto y disipación de la energía en el modelo del impacto humano en vidrio

    Pardo Fernández, Sergio
    Este trabajo se plantea como una pequeña aportación, a la gran labor que se está desarrollando desde el año 2003, en el estudio del impacto humano sobre el vidrio de edificación. En este contexto se propone como objetivo principal la investigación de una serie de hipótesis y el estudio de su validez mediante el empleo de modelos, con la intención de mejorar la respuesta obtenida con los modelos actuales, así como tratar de entender mejor los fenómenos que están afectando al desarrollo del ensayo. Para ello se utilizaran herramientas informáticas, entre ellas programas de elementos finitos, así como modelos elaborados...

  2. Micro-vascular shape-memory polymer actuators with complex geometries obtaines by laser stereolithography

    Díaz Lantada, Andrés; Blas Romero, Adrián de; Chacón Tanarro, Enrique
    In our work we present the complete development process of geometrically complex microvascular shape-memory polymer actuators. The complex geometries and three-dimensional networks are designed by means of computer aided design resources. Manufacture is accomplished, in a single step, by means of laser stereolithography, directly from the computeraided design files with the three dimensional geometries of the different actuators under development. To our knowledge, laser stereolithography is applied here for the first time to the development of shape memory polymer devices with complex geometries and inner microvasculatures for their activation using a thermal fluid. Final testing of the developed actuators helps...

  3. Morphology and thermal properties of biodegradable poly(hydroxybutyrate-co-hydroxyvalerate)/tungsten disulphide inorganic nanotube nanocomposites

    Silverman, Tyler; Naffakh Cherradi Hadi, Mohammed; Marco, Carlos; Ellis, Gary
    Promising biodegradable and renewable poly(hydroxybutyrate-co-hydroxyvalerate) (PHBV) nanocomposites based on tungsten disulphide inorganic nanotubes (INT-WS2) were efficiently prepared by a simple solution blending method. The structure, morphology, thermal stability and crystallization behavior of the nanocomposites were investigated by ultra-high field-emission scanning electron microscope (FESEM), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), wide-angle X-ray scattering (WAXS) and polarized optical microscopy (POM) techniques. As previously observed in poly(3-hydroxybutyrate) (PHB) hybrid systems, the dispersion, morphology and thermal properties of PHBV/INT-WS2 nanocomposites could be tuned by the introduction of small amounts of INT-WS2. The results revealed that a good dispersion of INT-WS2 in the PHBV...

  4. Polymer blend nanocomposites based on poly(L-lactic acid), polypropylene and WS2 inorganic nanotubes

    Naffakh Cherradi Hadi, Mohammed; Díez-Pascual, Ana M.; Marco, Carlos
    Tungsten disulphide inorganic nanotubes (INT-WS2) have been incorporated into poly(L-lactic acid) (PLLA)/ polypropylene (PP) blends compatibilized with polypropylene-grafted-maleic anhydride (PP-g-MAH), and their effects on the morphology, thermal and mechanical properties of the resulting nanocomposites have been investigated. The nanofillers were uniformly dispersed at the nanoscale via a melt-blending process. The addition of 1.0 wt% INT-WS2 to the PLLA/PP blends hardly affected their thermal stability or their degradation mechanism. Differential scanning calorimetry (DSC) thermograms revealed the nucleating role of INT-WS2 on both polymeric components, reflected not only in an increase in the crystallization temperature from the melt but also in a rise...

  5. Residual stress measurements of alumina-zirconia ceramics by time-of-flight neutron diffraction

    Fan, Kunyang; Ruiz Hervías, Jesús; Gurauskis, J.; Baudin, C.
    Neutron strain scanning and Rietveld analysis were used to study the residual stresses in Al2O3/Y-TZP ceramic composites fabricated by different green processing techniques (a novel tape casting and conventional slip casting) and with different zirconia content. The results show that the residual stresses in zirconia particulates are tensile and the ones in alumina matrix are compressive, with almost flat through-thickness residual stress profiles in all bulk samples. The residual stresses for both phases were mainly dependent on the zirconia content, irrespective of the measurement direction and the fabrication process.

  6. Measurement of fracture properties of concrete at high strain rates

    Rey de Pedraza Ruiz, Víctor; Cendón Franco, David Ángel; Sanchez Galvez, Vicente; Galvez Diaz-Rubio, Francisco
    An analysis of the spalling technique of concrete bars using the modified Hopkinson bar was carried out. A new experimental configuration is proposed adding some variations to previous works. An increased length for concrete specimens was chosen and finiteelement analysis was used for designing a conic projectile to obtain a suitable triangular impulse wave. The aim of this initial work is to establish an experimental framework which allows a simple and direct analysis of concrete subjected to high strain rates. The efforts and configuration of these primary tests, as well as the selected geometry and dimensions for the different elements, have been focused to achieve a simple way of identifying the fracture position and...

  7. Envejecimiento hidrotérmico en nanocompuestos epoxi/organoarcilla

    Gómez, A.; García del Cid, M.A.; Gonzalez Prolongo, Margarita; Salom Coll, Catalina; Masegosa Fanego, Rosa Maria
    Las dispersiones de organoarcillas como refuerzo en nanocompuestos de matriz polimérica han sido ampliamente estudiadas como una vía en la mejora de las propiedades (mecánicas, térmicas, de barrera frente a gases y disolventes e inflamabilidad). Una ventaja añadida es que se consigue una mejora de propiedades con la adición de una pequeña cantidad de refuerzo. En este trabajo se han preparado nanocompuestos basados en una matriz epoxi tipo DGEBA reforzada con dos organoarcillas, C30B e I.30E. Con el fin de mejorar la interfase matriz-refuerzo, también se han preparado nanocompuestos en los que las organoarcillas han sido previamente funcionalizadas a través...

  8. Material properties of evolutionary diverse spider silks described by variation in a single structural parameter

    Madurga, Rodrigo; Plaza Baonza, Gustavo Ramon; Blackledge, Todd A; Guinea Tortuero, Gustavo Víctor; Elices Calafat, Manuel; Pérez Rigueiro, José
    Spider major ampullate gland silks (MAS) vary greatly in material properties among species but, this variation is shown here to be confined to evolutionary shifts along a single universal performance trajectory. This reveals an underlying design principle that is maintained across large changes in both spider ecology and silk chemistry. Persistence of this design principle becomes apparent after the material properties are defined relative to the true alignment parameter, which describes the orientation and stretching of the protein chains in the silk fiber. Our results show that the mechanical behavior of all Entelegynae major ampullate silk fibers, under any conditions,...

  9. Betunes modificados con azufre: aditivos estabilizadores

    Masegosa Fanego, Rosa Maria; Cañamero, Pedro; Viñas Sanchez, Maria Teresa; Sánchez Cabezudo, Marta; Salom Coll, Catalina; Gonzalez Prolongo, Margarita; Paez, Antonio
    En el presente trabajo se estudia la influencia de aditivos encaminados a conseguir la estabilidad de dichos betunes modificados. Mediante medidas de viscosidad y penetración se ha comprobado que la presencia combinada de diciclopentadieno + aminas, favorece la interacción del azufre con el betún por formación de polisulfuros. Asimismo, se ha analizado la influencia de inhibidores de radicales libres

  10. Analysis of long-term corrosion behavior in mortars containing recycled ladle furnace slag using computerized tomography and SEM

    Rodríguez, A.; Gutierrez González, S.; Prieto Barrio, Maria Isabel; Cobo Escamilla, Alfonso; Calderón, V.
    A series of mortars subjected to accelerated corrosion in a humid environment form the basis for this study. In particular, we studied the corrosion behavior of steel reinforcement bars that were embedded in cement mortars that contained white ladle furnace slag (LFS) in partial substitution for fines and cement. The effects were observed using computerized axial tomography and scanning electron microscopy. Zones with fissures resulting from corrosion and the degree of damage due to passivation were identified from the imaging analysis.

  11. Evaluación de elementos de madera de pino silvestre de pequeña escuadría sometidos a compresión longitudinal a las fibras

    Llauradó Pérez, Nuria; González García, María de las Nieves; Martínez Pérez, Inmaculada; Pozo Fernández-Quejo, Tamara del
    En este trabajo se analiza el comportamiento a compresión de piezas de madera de pino silvestre de pequeña escuadría sometidas a un esfuerzo de compresión longitudinal a las fibras. Se han obtenido las propiedades mecánicas asociadas a este tipo de solicitación, se ha comprobado qué correlaciones pueden emplearse con éxito y se ha comprobado el ajuste de los valores obtenidos con los estimados por las normas de clasificación visual y resistente de la madera en uso. Para ello se han ensayado a compresión en sentido longitudinal a la fibra y hasta rotura 11 piezas de madera de pino silvestre de...

  12. Nuevo procedimiento de ensayo para determinar el coeficiente de pulimento acelerado de mezclas bituminosas

    Ramírez Rodríguez, Antonio
    La resistencia al deslizamiento es una de las propiedades que tienen más influencia en lo que respecta a la seguridad ofrecida por el pavimento y tiene una gran repercusión en la reducción de los accidentes, especialmente en circunstancias de lluvia o superficie mojada. La resistencia al deslizamiento en los pavimentos tiende a decrecer con el paso del tiempo, debido a la acción del tráfico y a otros factores, lo que repercute en una mayor inseguridad para los conductores. La medida de la resistencia al deslizamiento se ha convertido en una herramienta básica para la gestión de las redes de carreteras....

  13. Experimental Investigation of Wear and Structural Change During Hybrid Machining

    Rodríguez Marín, Elena
    This thesis aims at establishing the impact on the cutting tools from a macro- and microscopical point of view when milling Ti6Al4V using an hybrid process. Additionally, the microstructure of the workpiece after this procedure is submitted to analysis, too. The effect of the thermal cycle, that an hybrid procedure exerts on the cutting tool is on the focus of this work. This thermal cycle is intensiffed by the heat input of an inductor and the cooling effect of liquid CO2. Hybrid machining, is a new technique, developed to improve the machinability of certain diffcult to cut materials like titanium and its alloys....

  14. Evaluación de elementos de madera de pino insigne de pequeña escuadría sometidos a compresión transversal a las fibras

    González García, María de las Nieves; Llauradó Pérez, Nuria; Prieto Barrio, Maria Isabel; Gallego Guisado, José Luis
    Se han ensayado a compresión en sentido transversal a la fibra y hasta rotura 22 piezas de madera de pino silvestre de pequeña escuadría de 27 mm de espesor y 140 mm de altura y de ancho variable, comprendido entre 68 y 150 mm. Todas las tablas ensayadas son ME1 según la clasificación visual UNE-EN 56544:2011 y les corresponde una clasificación mecánica C27

  15. Consideraciones respecto al comportamiento físico y mecanico de hormigones ligeros estructurales

    Olmedo Zazo, Fernando Israel; Mateos Delso, Isabel; Díaz, F. Borja; González García, María de las Nieves; Cobo Escamilla, Alfonso
    Resulta paradójico que a pesar de las enormes ventajas que supone en muchas aplicaciones de construcción el empleo del hormigón ligero estructural (HLE) frente a un hormigón convencional (HC), su uso todavía no se haya generalizado. Muy posiblemente, el desconocimiento de su comportamiento físico y mecánico contribuye de forma decisiva a la utilización de un HC en muchas ocasiones en las que su sustitución por HLE sería totalmente competitivo y ventajoso. Este trabajo pretende ampliar el conocimiento del comportamiento del HLE para contribuir a su utilización en todas las situaciones en donde su empleo supone una clara ventaja frente al...

  16. Insights into the production and characterization of electrospun fibers from regenerated silk fibroin

    Solanas Díaz, María Concepción; Herrero Galán, Sara; Dasari, Aravind; Plaza Baonza, Gustavo Ramon; Llorca Martinez, Francisco Javier; Pérez Rigueiro, José; Elices Calafat, Manuel; Guinea Tortuero, Gustavo Víctor
    Regenerated silk fibroin solutions from Bombyx mori were tested for electrospinning.Simple and reproducible tensile tests were performed on threads of aligned fibers to obtain information about their mechanical performance at the fiber level. The binary solvent formic acid/chloroform (10:1, v/v) rendered unbeaded thinner fibers with increased extensibility before failure when compared with pure formic acid. A remarkable improvement in strength was induced by immersing length-restricted fibers into ethanol for 5 min. Conformational changes of the protein chains were studied by solid-state NMR.

  17. Persistence and variation in microstructural design during the evolution of spider silk

    Madurga, Rodrigo; Blackledge, Todd A; Perea, B.; Plaza Baonza, Gustavo Ramón; Riekel, Christian; Burghammer, Manfred; Elices, Margarita L.; Guinea Tortuero, Gustavo V.; Pérez Rigueiro, José
    The extraordinary mechanical performance of spider dragline silk is explained by its highly ordered microstructure and results from the sequences of its constituent proteins. This optimized microstructural organization simultaneously achieves high tensile strength and strain at breaking by taking advantage of weak molecular interactions. However, elucidating how the original design evolved over the 400 million year history of spider silk, and identifying the basic relationships between microstructural details and performance have proven difficult tasks. Here we show that the analysis of maximum supercontracted single spider silk fibers using X ray diffraction shows a complex picture of silk evolution where some...

  18. Standard and strain gradient crystal plasticity models: application to Titanium

    Rodríguez Galán, Daniel
    The necessity of improvements in metallic materials requires to understand the mechanisms that give the evolution of its mechanical properties at the micrometer scale. These mechanisms whose dependence and effects span several scales over length and time derive from plasticity in metals. In this realm, the current work is focused on the simulation at the continuum scale of the mechanical behavior of metals with a micromechanical description based on crystal plasticity because of its proven suitability to characterize the microstructural behaviour in crystalline materials. However, local crystal plasticity models are not able to capture the size effects. For this reason, strain gradient plasticity theories are introduced. This...

  19. Influencia de las condiciones de ejecución en la resistencia de anclajes de fibra de carbono para refuerzos en estructuras de hormigón

    Villanueva Llauradó, Paula
    Los materiales compuestos con fibra en matriz polimérica (FRP) son muy utilizados actualmente para actuaciones de refuerzo y rehabilitación de estructuras de hormigón armado y de fábrica, tanto de obra civil como de edificación. Entre las ventajas de estos materiales destacan su alta resistencia a tracción, alta relación resistencia/peso y buenas propiedades durables. En estructuras de hormigón se pueden emplear para refuerzo de elementos a compresión por confinamiento, y de elementos a flexión y cortante tales como vigas y losas. Las técnicas de refuerzo con FRP se clasifican atendiendo a la disposición del refuerzo, que puede ser exterior adherida a la superficie del elemento a reforzar o bien parcialmente embebida...

  20. Experimental mechanical characterisation of a estructural lightweigth aggregate concrete acording to EC-2

    Olmedo Zazo, Fernando Israel; Cobo Escamilla, Alfonso; Díaz, Borja; Vidal Mesa, María Ángeles
    The self load of a structure is usually higher than the loads it has to carry. It means that these kind of structures are quite often inefficient. The replacement in concrete of the normal aggregate by other lighter materials leads to a significant fall in the concrete weight. The normal aggregate has been replaced by lightweight aggregate since Roman Empire Ages. It has let singular buildings as Agripa's Pantheon or the Coliseum in Rome. Teh evolution according to the age of the compression and tensile strength and the Elastic Modulus in a Lightweight Aggregate Concrete (LAC) has been analysed in...

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