Mecánica de Medios Continuos y Teoría de Estructuras
https://hdl.handle.net/11441/11396
2024-03-29T06:32:18Z
2024-03-29T06:32:18Z
Development of Mortars That Use Recycled Aggregates from a Sodium Silicate Process and the Influence of Graphene Oxide as a Nano-Addition
https://hdl.handle.net/11441/156312
2024-03-15T10:27:18Z
2023-11-01T00:00:00Z
Development of Mortars That Use Recycled Aggregates from a Sodium Silicate Process and the Influence of Graphene Oxide as a Nano-Addition
This research analyses how different cement mortars behave in terms of their physical and mechanical properties. Several components were necessary to make seven mixes of mortars, such as Portland cement, standard sand, and solid waste from a factory of sodium silicate, in addition to graphene oxide. Furthermore, graphene oxide (GO) was selected to reduce the micropores and increase the nanopores in the cement mortar. Hence, some tests were carried out to determine their density, humidity content, water absorption capacity, open void porosity, the alkali–silica reaction, as well as flexural and mechanical strength and acid resistance. Thus, standard-sand-manufactured mortars’ mechanical properties were proved to be slightly better than those manufactured with recycled waste; the mortars with this recycled aggregate presented problems of alkali–silica reaction. In addition, GO (in a ratio GO/cement = 0.0003) performed as a filler, improving the mechanical properties (30%), alkali–silica (80%), and acid resistance
© 2023 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/)
2023-11-01T00:00:00Z
Effect of stacking direction and raster angle on the fracture properties of Onyx 3D printed components: A mesoscale analysis
https://hdl.handle.net/11441/155877
2024-03-06T10:32:56Z
2024-02-01T00:00:00Z
Effect of stacking direction and raster angle on the fracture properties of Onyx 3D printed components: A mesoscale analysis
3D printing is a technology that has gained increasing importance both in academia and industry for the possibilities offered. Among the many, one of the most appealing is the possibility to choose different printing configurations, tailoring stacking direction, and raster angle. The choice of such parameters deeply influences the structural response, as already shown in the literature. This study aims at providing a deep understanding of the phenomena taking place at the mesoscale level which justify such differences in the fracture behavior. An experimental campaign is carried out with a Single Edge Notch Bending (SENB) specimen printed in Onyx using four different combinations of raster angles and stacking directions. The results are compared in terms of mechanical response, fracture toughness and surface roughness to identify the main driving mechanisms during the fracture process. The same bending test is replicated numerically, aiming at comparing the fracture toughness values obtained experimentally with the ones used in the simulation to match the experimental curves. The study shows that the stacking direction and the raster angle deeply influence the fracture behavior and the mechanical properties of the specimen, along with the fracture toughness and surface roughness. In particular, it is highlighted how improved mechanical behavior can be achieved by printing the specimen in the vertical direction and with a raster angle of 45°/−45°. Moreover, useful fracture toughness values are identified for different combinations of printing parameters by means of a Cohesive Zone Model formulation, providing useful input values for numerical simulations.
©2023 TheAuthor(s).Published by Elsevier Ltd.This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/bync-nd/4.0/).
2024-02-01T00:00:00Z
Tensile and shear strength of bimaterial interfaces within composite materials
https://hdl.handle.net/11441/155823
2024-03-05T09:14:55Z
2016-03-01T00:00:00Z
Tensile and shear strength of bimaterial interfaces within composite materials
The determination of the tensile and shear strengths of homogeneous materials can be easily performed by standard tensile and shear (e.g. Iosipescu) tests. Nevertheless, when the determination of these strengths involves a bimaterial interface, the standard samples present bimaterial corner configurations at their free-edges which generate singular stress fields. In the presence of these singular stress fields, the tensile and shear stress distributions are strongly non-uniform at these edges, where failure initiates and propagates along the bimaterial interface. The apparent strength obtained from these tests is not representative of the regularized strength of the bimaterial interface. To eliminate the stress singularities, a small notch is made on one of the materials along the interface perimeter, in this study. This idea, originally proposed by Lauke and Barroso (Compos. Interface, 18:661-669, 2011) for ascertaining tensile strength, is now adapted to ascertain shear strength, using a modified geometry of the Iosipescu sample, and it has also been generalized to configurations involving composite materials. Both proposals, for the tensile and shear tests, are performed using the bimaterial configuration of a composite and an adhesive; a bimaterial interface which typically appears in adhesive joints with composites. The local notch geometry is defined using semi-analytical tools developed by the authors and numerically verified by Finite Element models. The modified bimaterial geometries, tested under tension, demonstrated a higher tensile strength. However, the modified bimaterial geometries tested in shear did not show any clear influence over the failure load with or without the notch in the particular bimaterial configuration tested in this study. © 2016 Elsevier Ltd.
2016-03-01T00:00:00Z
3D analysis of railway induced vibrations on skew girder bridges including ballast track–bridge interaction effects
https://hdl.handle.net/11441/155753
2024-03-01T13:11:16Z
2023-03-01T00:00:00Z
3D analysis of railway induced vibrations on skew girder bridges including ballast track–bridge interaction effects
This work is devoted to the analysis of the vibratory response of High-Speed (HS) multi-track railway bridges composed by simply-supported spans. In particular, it aims to investigate the influence of three geometrical aspects usually disregarded in numerical models used to evaluate the Serviceability Limit State of traffic safety in such structures: (i) the deck obliquity, (ii) the presence and correct execution of transverse diaphragms at the supports, and (iii) the number of successive simply-supported spans weakly coupled through the ballast track layer. The influence of these aspects is analysed from the correlation of a detailed numerical model and experimental measurements on an in-service High Speed (HS) multi-track railway bridge. From the reference model, a set of variants accounting for different levels of deck obliquity and diaphragm configurations are envisaged and the maximum transverse acceleration over the platform is determined under railway excitation. The analysis is extended to bridges with an increasing number of successive spans. Special attention is paid to the particular location of the maximum response and to the participation of modes different from the longitudinal bending one. Finally, a numerical–experimental comparison of the bridge response under two train passages is presented for the straight and oblique models, and the response adjustment along with the actual bridge performance are assessed.
2023-03-01T00:00:00Z