http://hdl.handle.net/10366/4369 Tue, 21 Apr 2026 05:34:07 GMT 2026-04-21T05:34:07Z http://hdl.handle.net/10366/169373 [EN] The interference fit is a common process for the assembly of mechanical parts on a shaft for diverse mechanical engineering applications. One of the manufacturing methods consists of introducing a shaft into a hub by applying a force being the hub diameter lower than the shaft diameter. This way, contact pressure is generated at the shaft–hub interface at the end of the process, enabling torque transmission. Thus, a non-uniformly distributed stress state appears at the shaft–hub interface with significant stress peaks at the hub edges. In addition, as a consequence of the manufacturing process, local plasticity is generated in the hub on the insertion side causing changes in stress distributions. In this paper, an analysis based on finite elements simulations is carried out to reveal the influence of, on one hand, manufacturing parameters such as friction on stress concentrations at the interface and, on the other hand, geometrical parameters such as hub chamfer angle, considering chamfer hubs and conventional hubs. To achieve this goal, different simulations of the mechanical manufacturing process of the axial assembly of press fits are carried out to reveal the stress fields at the interface. Thus, stress concentrations under different friction conditions from a case without friction to a dry friction case are revealed and analyzed. The results show, on one hand, the friction coefficient as a highly influential factor, causing asymmetrical stress distributions with high stress concentrations that reduce the mechanical performance of press fits and, on the other hand, the beneficial impact of chamfer hubs for lowering stress concentrations.; [ES] El ajuste por interferencia es un proceso común para el ensamblaje de piezas mecánicas en ejes para diversas aplicaciones de ingeniería mecánica. Uno de los métodos de fabricación consiste en introducir un eje en un cubo aplicando una fuerza cuyo diámetro es menor que el del eje. De esta manera, se genera presión de contacto en la interfaz eje-cubo al final del proceso, lo que permite la transmisión de par. Por lo tanto, se genera un estado de tensión distribuido de forma no uniforme en la interfaz eje-cubo, con picos de tensión significativos en los bordes del cubo. Además, como consecuencia del proceso de fabricación, se genera plasticidad local en el cubo en el lado de inserción, lo que provoca cambios en la distribución de tensiones. En este artículo, se realiza un análisis basado en simulaciones de elementos finitos para revelar la influencia de, por un lado, parámetros de fabricación como la fricción en las concentraciones de tensiones en la interfaz y, por otro, parámetros geométricos como el ángulo de chaflán del cubo, considerando cubos con chaflán y cubos convencionales. Para lograr este objetivo, se realizan diferentes simulaciones del proceso de fabricación mecánica del ensamblaje axial de ajustes a presión para revelar los campos de tensión en la interfaz. De este modo, se revelan y analizan las concentraciones de tensión en diferentes condiciones de fricción, desde un caso sin fricción hasta un caso de fricción en seco. Los resultados muestran, por un lado, que el coeficiente de fricción es un factor muy influyente, causando distribuciones asimétricas de tensión con altas concentraciones que reducen el rendimiento mecánico de los ajustes a presión y, por otro, el efecto beneficioso de los cubos chaflanados para reducir las concentraciones de tensión. Wed, 01 Jan 2025 00:00:00 GMT http://hdl.handle.net/10366/169373 2025-01-01T00:00:00Z http://hdl.handle.net/10366/169372 [EN] The theoretical expressions commonly used in the design of interference fits do not take into account the huge stress concentrations located at the edges of the hub. This underestimation of the real stress state can induce the incorrect performance of the shaft–hub assembly. Among the different methods to address this problem is the use of chamfer hubs, which are used for reducing such stress concentrations. In this paper, an analysis, performed via finite element method, of the influence of the geometric parameters of a shrink fit with chamfer hubs was carried out with the aim of determining the optimal dimensions for the design of this type of mechanical assembly. To achieve this goal, different chamfer hub geometries were considered: (i) full–chamfer hubs defined by the chamfer angle and (ii) partial–chamfer hubs defined by the chamfer angle and the chamfer height. According to the obtained results, stress concentrations can be reduced by using a full–chamfer hub with chamfer angles within the range 13°–15° depending on the hub thickness. In addition, similar results can be obtained by using partial–chamfer hubs with a chamfer height of half of the hub thickness and chamfer angles within the range 13°–15°. By using these design recommendations, the theoretical equations can be used without underestimating the real stress state.; [ES] Las expresiones teóricas comúnmente utilizadas en el diseño de ajustes por interferencia no consideran las altas concentraciones de tensión localizadas en los bordes del cubo. Esta subestimación del estado real de tensión puede inducir el funcionamiento incorrecto del conjunto eje-cubo. Entre los diferentes métodos para abordar este problema se encuentra el uso de cubos chaflanados, que se utilizan para reducir dichas concentraciones de tensión. En este trabajo, se realizó un análisis, realizado mediante el método de elementos finitos, de la influencia de los parámetros geométricos de un ajuste por contracción con cubos chaflanados con el objetivo de determinar las dimensiones óptimas para el diseño de este tipo de conjunto mecánico. Para lograr este objetivo, se consideraron diferentes geometrías de cubos chaflanados: (i) cubos con chaflán completo definidos por el ángulo del chaflán y (ii) cubos con chaflán parcial definidos por el ángulo y la altura del chaflán. De acuerdo con los resultados obtenidos, las concentraciones de tensión se pueden reducir utilizando un cubo con chaflán completo con ángulos de chaflán dentro del rango de 13° a 15°, dependiendo del espesor del cubo. Además, se pueden obtener resultados similares utilizando cubos con chaflán parcial, con una altura de chaflán de la mitad del espesor del cubo y ángulos de chaflán entre 13° y 15°. Con estas recomendaciones de diseño, se pueden aplicar las ecuaciones teóricas sin subestimar el estado de tensión real. Sun, 01 Jan 2023 00:00:00 GMT http://hdl.handle.net/10366/169372 2023-01-01T00:00:00Z http://hdl.handle.net/10366/169370 [EN] Press fits are a simple and effective method for assembling a shaft into a hub for different applications in the mechanical engineering field. This method consists of forcing to pass a shaft into a hub via axial insertion. As a result of the difference in the diameters of both components of the shaft and hub, a radial interference is generated, causing a contact pressure at the interface shaft–hub. Contact pressure and the friction coefficient are key factors influencing the maximum transmitted torque. So, in this study, different scenarios for the assembly of a press fit were simulated using finite elements (FE) in order to reveal the influence of this key parameter on the manufacturing-induced stresses in the hub. This way, different friction conditions were considered in terms of the friction coefficient from the frictionless case to a case of high dry friction. In addition, different hub geometries were analyzed including conventional hubs and chamfer hubs with optimal geometry that allows lowering the localized stress concentrations at the hub edges. This way, a more realistic estimation of the final stress state of a press fit is obtained. According to the obtained results, the friction coefficient is revealed as a key parameter in the resulting stress field, causing a non-uniform distribution of stress that can affect the mechanical performance of the press-fit assembly.; [ES] Los ajustes a presión son un método simple y efectivo para ensamblar un eje en un cubo para diversas aplicaciones en ingeniería mecánica. Este método consiste en forzar el paso de un eje en un cubo mediante inserción axial. Como resultado de la diferencia en los diámetros de ambos componentes, el eje y el cubo, se genera una interferencia radial que genera una presión de contacto en la interfaz eje-cubo. La presión de contacto y el coeficiente de fricción son factores clave que influyen en el par máximo transmitido. Por lo tanto, en este estudio, se simularon diferentes escenarios para el ensamblaje de un ajuste a presión mediante elementos finitos (EF) para revelar la influencia de este parámetro clave en las tensiones inducidas por la fabricación en el cubo. De esta manera, se consideraron diferentes condiciones de fricción en términos del coeficiente de fricción, desde un caso sin fricción hasta un caso de alta fricción en seco. Además, se analizaron diferentes geometrías de cubo, incluyendo cubos convencionales y cubos chaflanados con una geometría óptima que permite reducir las concentraciones de tensión localizadas en los bordes del cubo. De esta manera, se obtiene una estimación más realista del estado de tensión final de un ajuste a presión. De acuerdo con los resultados obtenidos, el coeficiente de fricción se revela como un parámetro clave en el campo de tensiones resultante, provocando una distribución no uniforme de la tensión que puede afectar al rendimiento mecánico del conjunto prensado. Sun, 01 Jan 2023 00:00:00 GMT http://hdl.handle.net/10366/169370 2023-01-01T00:00:00Z http://hdl.handle.net/10366/169369 [EN] As it is well known, shrink fits exhibit a stress concentration at the hub edges that can cause the failure of such mechanical components. A method for reducing such a stress concentration is placing a contact ring between the hub and the shaft. To achieve the desired effect, the Young Modulus of the material used for the contact ring must be lower than the one used in the hub and the shaft. Unfortunately, there are no design methods for estimating the optimal dimensions or materials of the contact ring. To fill this gap, in this study, diverse numerical simulations by the finite elements method (FEM) were carried out considering different geometries and materials in order to obtain recommendations that allow mechanical designers to significantly reduce the stress concentrations in these components. According to the obtained results, a contact ring of 25% of the hub thickness allows to significantly reduce up to 40% of the stress concentration. In addition, a linear influence of the stress reduction with the Young modulus was found thereby, and the most recommendable material for the contact ring is the one with the lowest Young modulus. On the other hand, according to the obtained results, the influence of the Poisson coefficient can be considered negligible.; [ES] Como es bien sabido, los ajustes por contracción presentan una concentración de tensiones en los bordes del cubo que puede provocar la falla de dichos componentes mecánicos. Un método para reducir dicha concentración consiste en colocar un anillo de contacto entre el cubo y el eje. Para lograr el efecto deseado, el módulo de Young del material utilizado para el anillo de contacto debe ser menor que el utilizado en el cubo y el eje. Desafortunadamente, no existen métodos de diseño para estimar las dimensiones o materiales óptimos del anillo de contacto. Para subsanar esta deficiencia, en este estudio se realizaron diversas simulaciones numéricas mediante el método de elementos finitos (MEF), considerando diferentes geometrías y materiales, con el fin de obtener recomendaciones que permitan a los diseñadores mecánicos reducir significativamente la concentración de tensiones en estos componentes. Según los resultados obtenidos, un anillo de contacto del 25 % del espesor del cubo permite reducir significativamente hasta un 40 % la concentración de tensiones. Además, se observó una influencia lineal de la reducción de tensiones con el módulo de Young, y el material más recomendable para el anillo de contacto es el que presenta el módulo de Young más bajo. Por otra parte, según los resultados obtenidos, la influencia del coeficiente de Poisson puede considerarse insignificante. Sat, 01 Jan 2022 00:00:00 GMT http://hdl.handle.net/10366/169369 2022-01-01T00:00:00Z http://hdl.handle.net/10366/169247 [EN] The main cause of in-service failure of cold drawn wires in aggressive environments is hydrogen embrittlement (HE). The non-uniform plastic strains and residual stresses generated after cold drawing play a significant role in the matter of HE susceptibility of prestressing steels. In this paper, a new and innovative design of the drawing scheme is developed, geared towards the reduction in both manufacturing-induced residual stresses and plastic strains. To achieve this goal, three innovative cold drawing chains (consisting in diverse multi-step dies where multiple diameter reductions are progressively carried out in a single die) are numerically simulated by the finite element (FE) method. From the residual stress and plastic strain fields revealed from FE numerical simulations, hydrogen accumulation for diverse times of exposure is obtained by means of FE simulations of the hydrogen diffusion assisted by stress and strains. Thus, an estimation of the HE susceptibility of the cold drawn wires after each process was obtained. Results reveal that cold drawn wire using multi-step dies exhibits lower stress and strain states nearby the wire surface. This reduction causes a decrease in the hydrogen concentration at the prospective damage zones, thereby improving the performance of the prestressing steel wires in hydrogenating environments promoting HE. Thus, the optimal wire drawing process design is carried out using special dies with several reductions per die.; [ES] La principal causa de fallos en servicio de los alambres trefilados en frío en entornos agresivos es la fragilización por hidrógeno (FE). Las deformaciones plásticas no uniformes y las tensiones residuales generadas tras el trefilado en frío influyen significativamente en la susceptibilidad a la FE de los aceros de pretensado. En este artículo, se desarrolla un diseño innovador del esquema de trefilado, orientado a la reducción tanto de las tensiones residuales como de las deformaciones plásticas inducidas por la fabricación. Para lograr este objetivo, se simulan numéricamente tres innovadoras cadenas de trefilado en frío (que constan de diversas matrices multietapa donde se realizan múltiples reducciones de diámetro progresivamente en una sola matriz) mediante el método de elementos finitos (EF). A partir de los campos de tensiones residuales y deformaciones plásticas revelados por las simulaciones numéricas de EF, se obtiene la acumulación de hidrógeno para diversos tiempos de exposición mediante simulaciones de EF de la difusión de hidrógeno asistida por tensiones y deformaciones. De este modo, se obtiene una estimación de la susceptibilidad a la FE de los alambres trefilados en frío después de cada proceso. Los resultados revelan que el alambre trefilado en frío utilizando matrices multietapa presenta menores estados de tensión y deformación cerca de la superficie del alambre. Esta reducción provoca una disminución de la concentración de hidrógeno en las zonas de posible daño, mejorando así el rendimiento de los alambres de acero de pretensado en entornos hidrogenantes que promueven la hidrogenación. Por lo tanto, el diseño óptimo del proceso de trefilado se realiza utilizando matrices especiales con varias reducciones por matriz. Mon, 19 Dec 2022 00:00:00 GMT http://hdl.handle.net/10366/169247 2022-12-19T00:00:00Z http://hdl.handle.net/10366/167956 [EN] Brick-and-mortar carbon fibre laminates combine high damage tolerance, multiple energy-dissipation mechanisms, and improved formability. However, compared with their properties found in natural materials, their mechanical performance is still really limited. One of the main advantages of natural materials is their complex structure, composed of several hierarchical levels at different scales. Regarding carbon fibre laminates, numerous works have shown the advantages of adding a small amount of nanofiller, but their behaviour in brick-and-mortar structures has still not fully understood. In this work, we have investigated the effect of graphene oxide in carbon fibre/epoxy brick-and-mortar laminates. We fabricated continuous and 25-mm length brick-and-mortar laminates from standard prepreg and prepreg filled with graphene oxide (0.68 wt%.). Tensile tests, Mode I (double cantilever test), and Mode II (thee point end-notched flexure) fracture test were carried out. Despite the low amount of graphene oxide, a slight increase in properties have been observed.; [ES] Los laminados de fibra de carbono tipo ladrillo y mortero combinan una alta tolerancia al daño, múltiples mecanismos de disipación de energía y una mejor conformabilidad. Sin embargo, en comparación con las propiedades de los materiales naturales, su rendimiento mecánico aún es bastante limitado. Una de las principales ventajas de los materiales naturales es su compleja estructura, compuesta por varios niveles jerárquicos a diferentes escalas. En el caso de los laminados de fibra de carbono, numerosos estudios han demostrado las ventajas de añadir una pequeña cantidad de nanofibras, pero su comportamiento en estructuras tipo ladrillo y mortero aún no se comprende del todo. En este trabajo, hemos investigado el efecto del óxido de grafeno en laminados tipo ladrillo y mortero de fibra de carbono/epoxi. Fabricamos laminados tipo ladrillo y mortero continuos y de 25 mm de longitud a partir de preimpregnado estándar y preimpregnado con óxido de grafeno (0,68 % en peso). Se realizaron ensayos de tracción, de fractura en modo I (doble voladizo) y de fractura en modo II (flexión con muesca en el extremo de tres puntos). A pesar de la baja cantidad de óxido de grafeno, se ha observado un ligero aumento en las propiedades. Wed, 01 Jan 2025 00:00:00 GMT http://hdl.handle.net/10366/167956 2025-01-01T00:00:00Z http://hdl.handle.net/10366/167925 [EN] Brick-and-mortar carbon fibre structures have attracted considerable attention owing to their reliable mechanical performance and processability. Their primary advantages include high damage tolerance, multiple energy dissipation mechanisms and the potential to use carbon fibre scraps instead of pristine carbon fibre prepregs. However, their behaviour under specific loading conditions, particularly Mode I and Mode II fracture, remains unclear. Moreover, while most studies have focused on thermoset matrix systems, research on brick-and-mortar composites with high-performance thermoplastic matrices remains scarce. To address this, the present study investigated the mechanical behaviour of brick-and-mortar laminates fabricated from carbon fibre/poly-ether-ether-ketone tapes. Tensile, Mode I (double cantilever beam) and Mode II (three-point end-notched flexure) fracture tests were conducted. Numerical simulations were also conducted to examine the underlying failure mechanisms, yielding good agreement with experimental observations.; [ES] Las estructuras de fibra de carbono tipo ladrillo y mortero han atraído considerable atención debido a su fiable rendimiento mecánico y procesabilidad. Sus principales ventajas incluyen una alta tolerancia al daño, múltiples mecanismos de disipación de energía y la posibilidad de utilizar restos de fibra de carbono en lugar de preimpregnados de fibra de carbono vírgenes. Sin embargo, su comportamiento bajo condiciones de carga específicas, en particular la fractura en Modo I y Modo II, aún no está claro. Además, si bien la mayoría de los estudios se han centrado en sistemas de matriz termoestable, la investigación sobre compuestos tipo ladrillo y mortero con matrices termoplásticas de alto rendimiento sigue siendo escasa. Para abordar esta cuestión, el presente estudio investigó el comportamiento mecánico de laminados tipo ladrillo y mortero fabricados con cintas de fibra de carbono/poliéter-éter-cetona. Se realizaron ensayos de tracción, fractura en Modo I (viga doble en voladizo) y fractura en Modo II (flexión en tres puntos con muesca en el extremo). También se llevaron a cabo simulaciones numéricas para examinar los mecanismos de fallo subyacentes, obteniendo una buena concordancia con las observaciones experimentales. Wed, 01 Jan 2025 00:00:00 GMT http://hdl.handle.net/10366/167925 2025-01-01T00:00:00Z http://hdl.handle.net/10366/160059 [EN] Natural structures such as nacre show an outstanding balance of strength and toughness, despite comprising mainly brittle constituents; this is a highly desirable combination of properties scarcely seen in synthetic composites. In this study, carbon fibre-reinforced polymer (CFRP) laminates mimicking the structure of nacre (‘brick-and-mortar’) were manufactured using the automated tape laying (ATL) technique, as a means of enhancing their interlaminar properties and fracture toughness. The interlaminar fracture toughness of the bio-inspired CFRP laminates was measured via double cantilever beam (DCB) and three-point bending end-notched flexure (3ENF) tests. The results indicated increments of up to 32% and 92%, respectively, in the interlaminar fracture toughness when compared with that of conventional continuous CFRP samples. In addition, the translaminar fracture toughness of the developed nacre-inspired CFRPs was measured through a compact tension (CT) test, which revealed increments of up to 30%. Finally, different reinforcement mechanisms were analysed to understand the effect of the ‘brick-and-mortar’ structure. Sat, 01 Jan 2022 00:00:00 GMT http://hdl.handle.net/10366/160059 2022-01-01T00:00:00Z http://hdl.handle.net/10366/159542 [EN] Carbon-fibre reinforced polymers (CFRPs) present outstanding mechanical performance per unit of mass; however, they also fail in a brittle manner, with little or no warning of their forthcoming catastrophic failure. In this study, a ‘brick-and-mortar’ design inspired by the structure of nacre was implemented by automated tape lay-up for the first time with the aim of changing the failure response of CFRPs. Standard procedures and materials already implemented in the aerospace industry have been used to produce bio-inspired CFRPs laminates, providing the first example of bio-inspired concepts scaled-up to industrial level. The effects of the proposed automated manufacturing process on the morphology and tensile properties of the laminates were investigated. A non-linear response was observed when the bio-inspired laminates were subjected to tensile forces. This type of response agrees with those of previous studies on lab-scale manufactured aligned discontinuous CFRPs. Fri, 01 Jan 2021 00:00:00 GMT http://hdl.handle.net/10366/159542 2021-01-01T00:00:00Z http://hdl.handle.net/10366/159541 [EN] A methodology based on step-heating thermography for predicting the length dimension of small defects in additive manufacturing from temperature data measured on thermal images is proposed. Regression learners were applied with different configurations to predict the length of the defects. These algorithms were trained using large datasets generated with Finite Element Method simulations. The different predictive methods obtained were optimized using Bayesian inference. Using predictive methods generated and based on intrinsic performance results, knowing the material characteristics, the defect length can be predicted from single temperature data in defect and non-defect zone. Thus, the developed algorithms were implemented in a laboratory set-up carried out on ad-hoc manufactured parts of Nylon and polylactic acid which include induced defects with different sizes and thicknesses. Using the trained algorithm, the deviation of the predicted results for the defect size varied between 13% and 37% for PLA and between 13% and 36% for Nylon. Sat, 01 Jan 2022 00:00:00 GMT http://hdl.handle.net/10366/159541 2022-01-01T00:00:00Z http://hdl.handle.net/10366/159440 [EN] This study investigates the low velocity impact behaviour and the energy absorption capability of a hybrid 3D woven composite made from S2-glass (GF), T700 carbon (CF) and Dyneema fibres. The laminate was asymmetric, having a high concentration of CF on one side and GF on the other. Experimental results revealed a pseudo-ductile behaviour of the material and a higher capability to absorb impact energy when glass plies are located at the back face of the laminate. A detailed fractographic analysis by means of X-ray microCT and a FE model was included to explain such differences. Sat, 01 Jan 2022 00:00:00 GMT http://hdl.handle.net/10366/159440 2022-01-01T00:00:00Z http://hdl.handle.net/10366/159033 This study aims to investigate the scientific impact of additive manufacturing in recent years, considering its evolution as an Industry 4.0 technology and also in the current context of Industry 5.0. For this aim, advanced statistics and scientometric tools have been used. Design/methodology/approach – This study aims to explore the trends and impacts of additive manufacturing, focusing on its evolution and its relationship with Industry 4.0 and 5.0. For this purpose, a scientometric study and a meta-analysis of data extracted from the scientific Scopus database have been carried out. R programming and specific bibliometric software have been used to conduct the research. Initially, the data were evaluated from various perspectives, including sources, topics and impact indexes, to assess trends derived from the volume of publications, the impact of sources and affiliations, as well as the production segmented by country and the relationships between authors from different countries. Subsequently, a meta-analysis on keywords has been carried out using two distinct clustering methodologies: link strength and fractionalization. The results obtained were compared to establish a specific taxonomy of the AM subtopics, considering AM as a single body of knowledge related to Industries 4.0 and 5.0 paradigms. The analyses carried out have shown the impact and strong evolution of additive manufacturing as a field of knowledge at the world level, both from the point of view of manufacturing processes and from the point of view of materials science. In addition, some differences have been detected depending on the country. As a result of the meta-analysis, four different subtopics have been detected, some of which are highly related to other technologies and approaches in Industries 4.0 and 5.0 paradigms. Additionally, it establishes a comprehensive taxonomy for AM research, serving as a foundational reference for future studies aimed at exploring the evolution and transformative impact of this technology. Tue, 28 May 2024 00:00:00 GMT http://hdl.handle.net/10366/159033 2024-05-28T00:00:00Z http://hdl.handle.net/10366/155188 [EN] The accumulation of load on asphalt pavement as a result of increased vehicle traffic generates problems in the asphalt layer due to permanent deformation. For correct design, it is essential to carry out a rheological characterization of the aggregate-binder materials that make up the asphalt mix. This article shows the analysis of permanent deformation based on the rheological behavior of asphalt mixtures and binders. Experimental tests based on creep and recovery phenomena allow the study of permanent deformations using theoretical models of fractional viscoelasticity. The rheological characterization allows us to detail the elasticity of the aggregate, n2, and the elastic-viscous properties of the different binders used, n1 and g. The results obtained show that it is possible to predict the deformations of the recovery phenomenon in asphalt mixtures from the rheological values (aggregate-binder) obtained in the creep process. Besides, the properties of the asphalt binder (n1 and g) correlate with the recovery phenomenon of the MSCR test for conventional and modified materials. The methodology proposed allows a better understanding of the states of permanent deformation to improve the design of binders and asphalt mixtures. Tue, 10 Nov 2020 00:00:00 GMT http://hdl.handle.net/10366/155188 2020-11-10T00:00:00Z http://hdl.handle.net/10366/155185 [EN] Temperature variations caused by seasonal changes and vehicle loads generate severe damage to asphalt layers. For a correct design, it is essential to carry out an adequate rheological characterization of both bitumen and bituminous mastic, since they are considered the weakest elements of the mixture. This article shows the results of the rheological behavior of mastics made of limestone filler and three types of binders, with a filler-bitumen ratio of 1/1, finding that the filler-bitumen interaction has a significant influence on asphalt mastics. Vehicle loads and climatic temperatures were simulated from MSCR and DSR tests to study the viscoelastic behavior of the bitumen and the mastic. Thus, stiffness, variation of the internal structure, viscosity, thermal susceptibility, permanent deformation, and cracking were determined. The results indicated that the filler causes an increase in the rigidity of the mastic for the whole range of temperatures and load frequencies, but this increase varies depending on the type of bitumen used. There is also no significant change in the phase angle variation between bitumens and mastics. This indicates that the bitumens maintain their internal structure when the filler is added, as well as considerably decreasing the accumulated strain in multiple stress creep recovery (MSCR) tests. Mon, 20 Jan 2020 00:00:00 GMT http://hdl.handle.net/10366/155185 2020-01-20T00:00:00Z http://hdl.handle.net/10366/155183 [EN] Copper slag (CS) is a derivative of copper production that is mainly composed of heavy metals. The large amount of this material accumulated around the world entails a serious environmental danger. Its use as a replacement of mineral aggregate in asphalt mixtures would allow to increase the durability and resistance, taking advantage of its physical-chemical properties. In this research, physicochemical analyses of different combinations of CS, reclaimed asphalt pavements (RAP), asphalt cement and aggregates by XRay Diffraction (XRD) and Fourier-Transform InfraRed spectroscopy (FT-IR) were developed. Subsequently, Marshall stiffness ratio, indirect tensile strength (IDT) and resilient modulus tests were performed to determine their implication in mechanical behaviour. Asphalt mixes with ranges from 45 to 55% of recycled material have improved stability, Marshall Flow and Stiffness ratio, obtaining values comparable with those from a conventional mixture. At the same time, its resilient modulus and IDT values increased by 35% compared to conventional mixes. To maintain values similar to conventional mixes, when the amount of RAP decreases the amount of CS should be increased, with a maximum value of 35%. This behaviour is explained by the presence of fayalite and magnetite in CS, which are hard, dense and hydrophobic components that produce increased elastic deformation of the binder before breaking. Fri, 30 Nov 2018 00:00:00 GMT http://hdl.handle.net/10366/155183 2018-11-30T00:00:00Z http://hdl.handle.net/10366/155181 [EN] asphalt bitumens. Asphalt mastics are viscoelastic composite materials widely used in the construction of pavement layers. The mechanical properties and the influence of the fillers on the filler/bitumen (f/b) matrix is one of the main areas of current research. In particular, the elastic determination of fillers for mechanical testing in asphalt mastic is relevant to understand permanent deformation caused by temperature variations caused by seasonal changes and vehicular traffic loads. In this sense, this research proposes a new methodology for rheological characterization of the elastic properties of the filler ξ2 and elastic-viscous properties of the asphalt bitumen, ξ1 and η, respectively, complementing the existing designs of asphalt mixture. The proposed methodology allows for identification of the influence of non-conventional fillers in the behavior of the asphalt mastic for the different recovery cycles of the Multiple Stress Creep Recovery (MSCR) and determination of new rheological parameters for the compression of the recovery phenomena and the elastic capacity of the type of filler and weight of the base bitumen. The results obtained show a greater adjustment to the experimental curves in determining the elastic modulus in each cycle for the hydrated lime and fly ash fillers with different filler/ bitumen ratios. In particular, the proposed model for bituminous mastics achieves a strong fit with the experimental curves by empirically reducing the quadratic error (R2 = 0.99) and managing to differentiate the elastic capacity ξ2 of each filler and its effect with increasing concentration. For example, it establishes that the Hydrated lime filler (HL) acquires an average Young’s modulus of 0.005 MPa, being 99.31% more elastic than Fly ash filler (FA) for a load of 3.2 kPa at a 1.25f/b ratio. In addition, the new model can be used to modify bitumen properties to design optimized and stronger asphalt mixtures. Mon, 25 Apr 2022 00:00:00 GMT http://hdl.handle.net/10366/155181 2022-04-25T00:00:00Z