Seigneurs marchands, abolition et mémoire : le cas de la seigneurie d’Aubert-Gallion

"Établi dès les débuts de la Nouvelle-France, le régime seigneurial, calqué sur les institutions françaises, est le principal moteur de développement durant les premières décennies de la colonie. Que ce soit pour mettre en valeur un nouveau territoire ou pour développer des activités commerciales, ce système foncier permet une croissance constante, mais inégale du territoire. Ainsi, les terres aux abords du fleuve Saint-Laurent sont les premières à être développées alors que les seigneuries dans l’est du Québec se caractérisent par un peuplement plus tardif. […]

De la sinophilie à la sinophobie ? : les femmes chinoises sous le regard des voyageurs européens aux XVIIe et XVIIIe siècles

Ce mémoire cherche à démontrer les liens qui existent entre la représentation des femmes chinoises et celle de la Chine en général aux XVIIe et XVIIIe siècles. L’historiographie soutient qu’il y a une transition dans la manière de percevoir la Chine qui fait passer celle-ci de généralement positive à négative vers la fin du XVIIIe siècle. René Étiemble qualifie cette évolution de sinophilie/sinophobie et se base principalement sur les échanges philosophiques, scientifiques et théologiques entre la Chine et l’Europe. Ces concepts ont cependant été peu analysés sous l’angle du genre. M’appuyant sur les récits de voyages des diplomates et marchands de cette période, je défends que les représentations des Chinoises évoluent dans plusieurs directions : certaines d’entre elles s’inscrivent dans la mouvance de la sinophilie/sinophobie, alors que d’autres s’écartent de ce cadre théorique. Dans certains cas, la Chinoise devient un truchement par lequel on s’invente l’Empire du Milieu. Dans d’autres situations, la représentation des Chinoises se fait indépendamment de l’image de la Chine, et il convient donc de la concevoir autrement. En observant le corps des Chinoises, les rapports de genre dans le quotidien et la marginalité féminine, ce mémoire a la modeste prétention de vérifier la pertinence du modèle théorique d’Étiemble du point de vue des représentations de genre

Toughening elastomers via microstructured thermoplastic fibers with sacrificial bonds and hidden lengths

Soft materials capable of large inelastic deformation play an essential role in high-performance nacre-inspired architectured materials with a combination of stiffness, strength and toughness. The rigid "building blocks" made from glass or ceramic in these architectured materials lack inelastic deformation capabilities and thus rely on the soft interface material that bonds together these building blocks to achieve large deformation and high toughness. Here, we demonstrate the concept of achieving large inelastic deformation and high energy dissipation in soft materials by embedding microstructured thermoplastic fibers with sacrificial bonds and hidden lengths in a widely used elastomer. The microstructured fibers are fabricated by harnessing the fluid-mechanical instability of a molten polycarbonate (PC) thread on a commercial 3D printer. Polydimethylsiloxane (PDMS) resin is infiltrated around the fibers, creating a soft composite after curing. The failure mechanism and damage tolerance of the composite are analyzed through fracture tests. The high energy dissipation is found to be related to the multiple fracture events of both the sacrificial bonds and elastomer matrix. Combining the microstructured fibers and straight fibers in the elastomer composite results in a ~ 17 times increase in stiffness and a ~ 7 times increase in total energy to failure compared to the neat elastomer. Our findings in applying the sacrificial bonds and hidden lengths toughening mechanism in soft materials at the microscopic scale will facilitate the development of novel bioinspired laminated composite materials with high mechanical performance

Efficient planning of peen-forming patterns via artificial neural networks

Robust automation of the shot peen forming process demands a closed-loop feedback in which a suitable treatment pattern needs to be found in real-time for each treatment iteration. In this work, we present a method for finding the peen-forming patterns, based on a neural network (NN), which learns the nonlinear function that relates a given target shape (input) to its optimal peening pattern (output), from data generated by finite element simulations. The trained NN yields patterns with an average binary accuracy of 98.8\% with respect to the ground truth in microseconds

Vortex-induced vibrations: a soft coral feeding strategy?

Soft corals, such as the bipinnate sea plume Antillogorgia bipinnata, are colony building animals that feed by catching food particles brought by currents. Because of their flexible skeleton, they bend and sway back and forth with the wave swell. In addition to this low-frequency sway of the whole colony, branches of A. bipinnata vibrate at high frequency with small amplitude and transverse to the flow as the wave flow speed peaks. In this paper, we investigate the origin of these yet unexplained vibrations and consider their effect on soft corals. Estimation of dynamical variables along with finite element implementation of the wake-oscillator model favour vortex-induced vibrations (VIVs) as the most probable origin of the observed rapid dynamics. To assess the impact of the dynamics on filter feeding, we simulated particles advected by the flow around a circular cylinder and calculated the capture rate with an in-house monolithic fluid-structure interaction (FSI) finite element solver and Python code. We observe that vibrating cylinders can capture up to 40% more particles than fixed ones at frequency lock-in. Therefore, VIVs plausibly offer soft corals a better food capture.Comment: 20 page

Simulating shot peen forming with eigenstrains

Shot peen forming is a cold work process used to shape thin metallic components by bombarding them with small shots at high velocities. Several simulation procedures have been reported in the literature for this process, but their predictive capabilities remain limited as they systematically require some form of calibration or empirical adjustments. We intend to show how procedures based on the concept of eigenstrains, which were initially developed for applications in other fields of residual stress engineering, can be adapted to peen forming and stress-peen forming. These tools prove to be able to reproduce experimental results when the plastic strain field that develop inside a part is known with sufficient accuracy. They are, however, not mature enough to address the forming of panels that are free to deform during peening. For validation purposes, we peen formed several 1 by 1 m 2024-T3 aluminum alloy panels. These experiments revealed a transition from spherical to cylindrical shapes as the panel thickness is decreased for a given treatment, that we show results from an elastic instability

Drag reduction of flexible plates by reconfiguration

International audienceThrough an extensive and systematic experimental investigation of two geometries of flexible plates in air, it is shown that a properly defined scaled Cauchy number allows collapsing all drag measurements of the reconfiguration number. In the asymptotic regime of large deformation, it is shown that the Vogel exponents that scale the drag with the flow velocity for different geometries of plates can be predicted with a simple dimensional analysis reasoning. These predicted Vogel exponents are in agreement with previously published models of reconfiguration. The mechanisms responsible for reconfiguration, namely area reduction and streamlining, are studied with the help of a simple model for flexible plates based on an empirical drag formulation. The model predicts well the reconfiguration observed in the experiments and shows that for a rectangular plate, the effect of streamlining is prominent at the onset of reconfiguration, but area reduction dominates in the regime of large deformation. Additionally, the model demonstrates for both geometries of plates that the reconfiguration cannot be described by a single value of the Vogel exponent. The Vogel exponent asymptotically approaches constant values for small and for very large scaled Cauchy numbers, but in between both extremes it varies significantly over a large range of scaled Cauchy number. Copyright © Cambridge University Press 2010

Flutter Limitation of Drag Reduction by Elastic Reconfiguration

Through experiments, we idealise a plant leaf as a flexible, thin, rectangular plate clamped at the midpoint and positioned perpendicular to an airflow. Flexibility of the structure is considered as an advantage at moderate flow speed because it allows drag reduction by elastic reconfiguration, but it can also be at the origin of several flow-induced vibration phenomena at higher flow speeds. A wind tunnel campaign is conducted to identify the limitation to elastic reconfiguration that dynamic instability imposes. Here we show by increasing the flow speed that the flexibility permits a considerable drag reduction by reconfiguration, compared to the rigid case. However, beyond the stability limit, vibrations occur and limit the reconfiguration. This limit is represented by two dimensionless numbers: the mass number, and the Cauchy number. Our results reveal the existence of a critical Cauchy number below which static reconfiguration with drag reduction is possible and above which a dynamic instability with important fluctuating loads is present. The critical dimensionless velocity is dependant on the mass number. Flexibility is related to the critical reduced velocity, and allows defining an optimal flexibility for the structure that leads to a drag reduction by reconfiguration while avoiding dynamic instability. Furthermore, experiments show that our flexible structure can exhibit two vibration modes: symmetric and anti-symmetric, depending on its mass number. Because the system we consider is bluff yet aligned with the flow, it is unclear whether the vibrations are due to a flutter instability or vortex-induced vibration or a combination of both phenomena.Comment: 10 pages, 11 figures, Published in Physics of Fluid

Modal analysis of a spinning disk in a dense fluid as a model for high head hydraulic turbines

In high head Francis turbines and pump-turbines in particular, Rotor Stator Interaction (RSI) is an unavoidable source of excitation that needs to be predicted accurately. Precise knowledge of turbine dynamic characteristics, notably the variation of the rotor natural frequencies with rotation speed and added mass of the surrounding water, is essential to assess potential resonance and resulting amplification of vibrations. In these machines, the disk-like structures of the runner crown and band as well as the head cover and bottom ring give rise to the emergence of diametrical modes and a mode split phenomenon for which no efficient prediction method exists to date. Fully coupled Fluid-Structure Interaction (FSI) methods are too computationally expensive; hence, we seek a simplified modelling tool for the design and the expected-life prediction of these turbines. We present the development of both an analytical modal analysis based on the assumed mode approach and potential flow theory, and a modal force Computational Fluid Dynamics (CFD) approach for rotating disks in dense fluid. Both methods accurately predict the natural frequency split as well as the natural frequency drift within 7.9% of the values measured experimentally. The analytical model explains how mode split and drift are respectively caused by linear and quadratic dependence of the added mass with relative circumferential velocity between flexural waves and fluid rotation

Stability of a rotating cylindrical shell containing axial viscous flow

Un modèle d'écoulement visqueux a été développé pour étudier la stabilité d'une coque cylindrique contenant un écoulement axial parce que le modèle de fluide parfait a été démontré comme étant inadéquat. Il a été montré que la stabilité du système est très sensible à la modélisation de l'interface coque-fluide et qu'un faible taux de rotation tend à stabiliser le système