Development and calibration of a numerical model of a VANT wing for aeroelastic applications

Um dos maiores desafios da indústria aeronáutica é reduzir o impacto ambiental das aeronaves, tornando suas estruturas mais eficientes energeticamente e mecanicamente. Este objetivo se reflete no desenvolvimento de aeronaves mais leves, com um menor consumo de combustível. Inovações como estas têm produzido também estruturas alares mais flexíveis que, em voo, estão sujeitas à ação de fenômenos aeroelásticos, como o flutter, que podem ser catastróficos. A correta previsão deste fenômeno inicia no desenvolvimento de um modelo que represente adequadamente a estrutura do ponto de vista dinâmico. Este modelo pode ter diferentes níveis de detalhamento do ponto de vista de projeto, porém depende de calibração para ter capacidade de predição de suas características dinâmicas. Neste contexto, este trabalho apresenta o estudo e o desenvolvimento de um modelo numérico representativo de uma asa da aeronave de competição JF-02 da equipe UFRGS PAMPA AeroDesign e de um projeto experimental capaz de fornecer informações úteis para sua calibração. A fim de representar fielmente o modelo físico, o modelo numérico é calibrado utilizando dados de ensaios de flexão e vibração livre. Os resultados demostram que, com a calibração, as propriedades de rigidez e massa da asa melhoram de forma significativa frente aos experimentos, tornando o modelo mais adequado para análises aeroelásticas.One of the biggest challenges of the aeronautical industry is to reduce the environmental impact of aircrafts, making their structures more energetically and mechanically efficient. This objective is reflected in the development of lighter aircrafts, with lower fuel consumption. These innovations have also produced more flexible wing structures that are subjected to the action of aeroelastic phenomena in flight, such as flutter, which can be catastrophic. The correct prediction of this phenomenon starts with the development of a model that represents adequately the structure from a dynamic point of view. This model can have different levels of detail from the design point of view. However, it depends on calibration to be able to predict its dynamic characteristics. In this context, this work presents the study and development of a representative numerical model of a wing of the competition aircraft JF-02 from the UFRGS PAMPA AeroDesign team and of an experimental project capable of providing useful information for its calibration. In order to accurately represent the physical model, the numerical model is calibrated using data from flexion and free vibration tests. The results show that, with the calibration, the wing's rigidity and mass properties improve significantly compared to the experiments, making the model more suitable for aeroelastic analyzes

Exploitation de la dynamique non-linéaire dans des chaînes « mass-in-mass » pour la conception de métamatériaux

Les phénomènes de bruits et de vibrations peuvent être avantageusement exploités, par exemple, pour récupérer leur énergie afin d'alimenter des capteurs déportés, pour surveiller l'intégrité des structures, pour augmenter la précision de mesure d'accélération ou de masse infime de dispositifs médicaux. Exploiter ces phénomènes nécessite avant tout de maîtriser leurs effets afin d'induire des réponses spécifiques. Des stratégies telles que le couplage d'absorbeurs au système principal ou la conception de matériaux aux comportements sur mesure peuvent être utilisées pour atténuer les oscillations et réguler les comportements vibratoires. Cette recherche se concentre sur les interactions entre les cellules "mass-in-mass" non linéaires et la modélisation de leurs comportements, et se veut ainsi une étape préliminaire vers la création de nouveaux types de métamatériaux non linéaires à comportement prédéfini. Cela englobe des développements analytiques et numériques, ainsi que des études d'optimisation visant à ajuster de manière précise les paramètres de conception de la non linéarité explorée dans cette étude.This thesis focuses on the interactions of nonlinear mass-in-mass cells and on modeling their behaviors, serving as a preliminary step towards the creation of new types of nonlinear metamaterials with designed behaviors. During this investigation, a specific piecewise nonlinearity is explored, initially in a single mass-in-mass cell and, subsequently, in a chain of coupled cells. For the latter, certain approximations are applied to transition from the discrete to the continuous domain and to study the behavior of the chain in the vicinity of one of its arbitrary modes. Both fast and slow dynamics are unveiled for the single cell and the chain, providing design tools to tune parameters of the piecewise nonlinearity. Moreover, a stochastic optimization study is conducted to design a mass-in-mass meta-cell. Given the mechanical complexity of implementing the explored nonlinearity in this thesis, an experimental study is performed on a programmable electroacoustic loudspeaker

Experimental evidences of nonlinear programmable electroacoustic loudspeaker

International audienceA two degrees-of-freedom system coupling an acoustical mode of a closed tube to an electroacoustic loudspeaker is considered. A model-inversion technique is presented to digitally program the impedance of the loudspeaker for reaching a targeted nonlinear behavior. Experimental results show that the programed nonlinearity can guide the system to both periodic and non- periodic responses while acoustical levels for activation of the nonlinearity are less than the ones for systems with passive nonlinear oscillators (94 and 100 dB in this paper compared to 138 dB in previous papers), allowing building applications. Moreover, it is spotted that the programed nonlinearity of the electroacoustic loudspeaker, even in its non-optimized form, performs non- linear noise control for some frequency ranges. The main objective of this article is to show that it is possible to program the behavior of an electroacoustic loudspeaker

NEOTROPICAL ALIEN MAMMALS: a data set of occurrence and abundance of alien mammals in the Neotropics

Biological invasion is one of the main threats to native biodiversity. For a species to become invasive, it must be voluntarily or involuntarily introduced by humans into a nonnative habitat. Mammals were among first taxa to be introduced worldwide for game, meat, and labor, yet the number of species introduced in the Neotropics remains unknown. In this data set, we make available occurrence and abundance data on mammal species that (1) transposed a geographical barrier and (2) were voluntarily or involuntarily introduced by humans into the Neotropics. Our data set is composed of 73,738 historical and current georeferenced records on alien mammal species of which around 96% correspond to occurrence data on 77 species belonging to eight orders and 26 families. Data cover 26 continental countries in the Neotropics, ranging from Mexico and its frontier regions (southern Florida and coastal-central Florida in the southeast United States) to Argentina, Paraguay, Chile, and Uruguay, and the 13 countries of Caribbean islands. Our data set also includes neotropical species (e.g., Callithrix sp., Myocastor coypus, Nasua nasua) considered alien in particular areas of Neotropics. The most numerous species in terms of records are from Bos sp. (n = 37,782), Sus scrofa (n = 6,730), and Canis familiaris (n = 10,084); 17 species were represented by only one record (e.g., Syncerus caffer, Cervus timorensis, Cervus unicolor, Canis latrans). Primates have the highest number of species in the data set (n = 20 species), partly because of uncertainties regarding taxonomic identification of the genera Callithrix, which includes the species Callithrix aurita, Callithrix flaviceps, Callithrix geoffroyi, Callithrix jacchus, Callithrix kuhlii, Callithrix penicillata, and their hybrids. This unique data set will be a valuable source of information on invasion risk assessments, biodiversity redistribution and conservation-related research. There are no copyright restrictions. Please cite this data paper when using the data in publications. We also request that researchers and teachers inform us on how they are using the data