Browsing by Author "Costa, D. M. S."
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- Assessing the static behavior of hybrid CNT-metal-ceramic composite platesPublication . Costa, D. M. S.; Loja, AméliaFunctionally graded materials are commonly particulate composites characterized by a varying spatial distribution of the inclusion particles. Because of this, these materials possess a great suitability potential concerning to material properties, which can be very useful to achieve specified structural behaviors. Significant features of these materials are related to their thermal barrier properties especially when ceramic materials are involved, and to the mitigation of abrupt stresses transitions, typically found in laminates. From the manufacturing point of view as well as from the computational perspective, these materials can be thought as effectively having a continuous variation of their constituent phases and consequently their properties, or by resulting from the stacking of a specified number of layers, each having constant properties. This work presents a set of parametric studies aiming to characterize the static response of hybrid functionally graded plates, concerning to their transverse displacement profile and stresses distributions. To this purpose, one considers parameters such as different ceramic materials, plates’ aspect ratio, continuous or discrete variation of phase’s mixture through thickness, the carbon nanotubes (CNT) weight fraction contents and the type of nanotubes. The results obtained are discussed and conclusions are drawn.
- Bat-inspired optimization of multilayered adaptive structuresPublication . Costa, D. M. S.; Loja, M. A. R.Adaptive structures constituted by composites and smart materials is a remarkable engineering combination that join together the already known composites’ advantages and the possibility of actively control the mechanical response of a structure. These versatile structures are able to react and interact with their surrounding environments, continuously, to accomplish specific objectives. In this work, the main objective is to study, model and predict the mechanical behaviour of adaptive structures by programming the finite element method and optimization algorithms based on micro-bats’ echolocation capacity. An integrated symbolic-numerical-graphical package devoted to the analysis of plate/beam-type structures and its meta-heuristic optimization is implemented, with capabilities of simulating active multilayered structures, constituted by a variable number of different material models. Graded mixtures of piezoelectric particles and non-active materials are also modelled along the structures’ length direction. A set of illustrative case studies are performed, for different types of structures and materials and the results obtained are discussed and conclusions are drawn.
- Comparison between 3D laser scanning and computed tomography on the modelling of head surfacePublication . Sousa, E.; Vieira, L.; Costa, D. M. S.; Costa, D. C.; Parafita, R.; Loja, AméliaThe measurement of people physical parameters and proportions constitutes an importante field of science, the anthropometry, since it is related to the characterization of the human size and constitution; it allows improving the design and sizing of systems and devices to human use. To enable these measurements, different direct and indirect methodologies may be used depending on the particular aim of a specific study and on the eventual availability of data sources that can be used also for this purpose. Because of this relevance, the present work intends to assess the influence of diferente acquisition and reconstruction methods in the modelling of a 3D head surface. In order to assess the significance of the differences between acquisition and reconstruction methods a set of measurements between several anatomic references of a physical phantom were carried out. Statistical evaluation using the Friedman test for non-parametrical pared samples was considered. We found, so far, no statistically significant differences between the several methods considered for acquisition and reconstruction.
- Functionally graded particulate composite plates: a dydactic case studyPublication . Costa, D. M. S.; Bernardo, G. M. S.; Loja, AméliaThis work is part of an educational symbolic platform which was designed to aid and promote the learning of the mechanical behaviour of thin, simply supported rectangular plates. The integration of such simulation tools into the teaching process as an assisting tool can be an additional factor to contribute for a successful competences achievement on this subject. The present case study is focused on the deflection analysis of a functionally graded particulate composite plate submitted to a user-defined transverse loading.
- Mechanics of homogeneous and non-homogeneous thin plates: a symbolic simulation platformPublication . Costa, D. M. S.; Loja, AméliaThe present work presents a learning platform focused on the analysis of thin rectangular plates, which main objectives beyond the prediction of the mechanical behaviour of these structures, are the improvement of the perception of the physical phenomena and the parameters involved in the evaluation of the structural model. The platform developed allows studying homogeneous and non homogeneous rectangular plates, supported along its four edges and submitted to arbitrary loads. Intermediate outputs are presented either in graphical or numerical format, and cover all relevant physical quantities related to static and free vibrations analysis of these plates. To enable the development of this work in such a generic form, this simulation didactic platform stands upon a symbolic computation environment. The present simulation platform is part of a major project that is being developed in the context of the mechanical design scientific area, and it intends to improve the learning process in structural mechanics at BSc and MSc levels.
- Optimization of desalination heat exchanger`s geometries using bat-inspired techniquesPublication . Costa, D. M. S.; Trindade, J. M. F.; Loja, AméliaIn many regions of the world there are persisting situations of lack of potable water with the well-known consequences in population’s daily life, where a poverty logic loop seems to be definitely installed. In some of those regions, where seawater and solar energy resources are abundant, the use of this kind of energy may be an effective alternative to consider for seawater desalination. Falling film evaporators allow high heat transfer rates and are an important key to achieve greater efficiencies throughout several industries. Desalination systems, especially when driven by renewable energies, tend to be highly dependent of appropriate efficiencies. In order to study this matter, a meta-heuristic optimization of a desalination model of this kind is done, focusing on some design variables of the evaporator’s geometry. Because of the context of the present work, the achievement of an optimal solution, from the global heat transfer perspective is a particularly important objective. To enable this optimization study, different implementations of bat-inspired optimization technique will be considered, aiming at the minimization and maximization of the falling film heat transfer coefficient, within a desalination model, based on a horizontal falling film evaporator. A parametric study concerning the heat exchangers’ selected design variables will be carried out and discussed, along with an influence analysis ofother optimization parameters.
- A symbolic simulator platform for the static analysis of thin platesPublication . Costa, D. M. S.; Bernardo, G. M. S.; Loja, AméliaThe integration of symbolic capabilities into a simulation platform devoted to the analysis of thin plates can provide a greater flexibility in the learning process as it enables to incorporate, to experiment and simulate more complex and user-defined characteristics. With the present work one has built a symbolic simulator for the study of the mechanical behaviour of thin plates. These plates, with a rectangular/square basis geometric configuration, are simply supported along its four edges, and can be made from homogeneous or non-homogeneous materials. The capabilities of this platform are briefly illustrated through an illustrative case study.