Énergie potentielle élastique

En physique, l’énergie potentielle élastique est l'énergie potentielle emmagasinée dans un corps à caractère élastique lorsque ce dernier est compressé ou étiré par rapport à sa position naturelle. Lorsque la force comprimant ou étirant le ressort cesse, le corps tend naturellement à retourner à sa position naturelle et transforme ainsi son énergie potentielle en énergie cinétique. Le caractère élastique d'un objet est remarquable par la capacité de celui-ci à rebondir ou encore à reprendre sa forme après déformation. thumb|Le corps possède de l'énergie potentielle élastique lorsqu’il est comprimé ou étiré. Démonstration L'énergie potentielle élastique, notée E_{pe} et exprimée en joules, dépend de x (allongement ou raccourcissement du ressort par rapport à la longueur au repos de celui-ci) en mètres et de la constante de rappel ou de raideur k du ressort, exprimée en newtons par mètre (N/m) selon la relation : E_{pe}=\frac{1}

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Compressive-shear adhesion characterization of polyvinyl-butyral and ethylene-vinyl acetate at different curing times before and after exposure to damp-heat conditions

Christophe Ballif, Valentin Chapuis, Hengyu Li, Laure-Emmanuelle Perret Aebi

Photovoltaic (PV) module efficiency and reliability are two factors that have an important impact on the final cost of the PV electricity production. It is widely accepted that a good adhesion between the encapsulant and the different substrates of a PV module is needed to ensure long-term reliability. Several testing procedures exist that use a metric derived from the force at interface failure to characterize the adhesion. It has, however, not been demonstrated that those metrics relate directly to the interfacial adhesion (defined as the surface energy density needed to break interfacial bonds), and the obtained results usually relate to an apparent adhesion strength. In this work, we describe a new design for compressive-shear testing of polymer layers bonded to rigid substrates. We use it to characterize real interfacial adhesion of ethylene-vinyl acetate (EVA) and polyvinyl-butyral (PVB) to a glass substrate before and after degradation in damp-heat. Our results show that a peak-force based metric is unable to capture the evolution of adhesion through degradation, and a new metric based on the elastic strain energy of the encapsulant is proposed. Moreover, we show that PVB adhesion to glass is much more affected by damp-heat exposure where polymer saturation takes place, in comparison with the adhesion of EVA to glass. The presented characterization protocol is a powerful tool that can help in assessing the reliability of an encapsulant facing specific degradation conditions. Copyright © 2012 John Wiley & Sons, Ltd.

Wiley-Blackwell2012

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Characterization, mechanical properties and dimensional accuracy of a Zr-based bulk metallic glass manufactured via laser powder-bed fusion

Jamasp Jhabvala, Güven Kurtuldu, Roland Logé, Antonia Neels, Efthymios Polatidis, Navid Sohrabi, Steven Van Petegem

Bulk metallic glasses (BMGs) are high-strength, highly elastic materials due to their disordered atomic structure. Because BMGs require sufficiently high cooling rates to bypass crystallization, laser-based additive manufacturing (AM) methods have recently been employed for the fabrication of BMGs. In this study, we present an optimized Laser Powder-Bed Fusion (LPBF) process on a Zr-based BMG (Zr59.3Cu28.8Al10.4Nb1.5, in at.%), with a focus on characterization, mechanical properties, and dimensional accuracy. A volumetric density of 99.82% was achieved. Although the sample was qualified as amorphous via laboratory X-ray diffraction experiments, a more meticulous study using synchrotron radiation revealed nanocrystals in the heat-affected zones (HAZs) of the melt pool. Fast differential scanning calorimetry (FDSC) and numerical simulations were then employed to illustrate the mechanism of crystallization. The LPBF-processed alloy revealed excellent mechanical properties, such as high hardness, wear resistance, compressive strength, and flexural strength. Apart from vein-like patterns, the fracture surfaces of the compression test samples showed liquid-like features, which indicate a significant local temperature increase during fracture. The dimensional accuracy was assessed with a benchmark exhibiting complex geometrical features and reached at least 40 μm. The results indicate that LPBF processing is a promising route for the manufacturing of BMGs for various applications.

2020

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Universal Behavior in the Mesoscale Properties of Amyloid Fibrils

Salvatore Assenza, Paolo De Los Rios, Raffaele Mezzenga

Amyloid fibrils are ubiquitous proteinaceous aggregates occurring in vivo and in vitro, with an invariant structural fingerprint at the molecular length scale. However, interpretation of their mesoscopic architectures is complicated by diverse observable polymorphic states. We here present a constitutive model for amyloid fibrils based on the minimization of the total energy per fibril. The model is benchmarked on real amyloid fibrils studied by atomic force microscopy. We use multistranded ss-lactoglobulin amyloid fibrils as a model system exhibiting a rich polymorphism. The constitutive model quantitatively recapitulates the main mesoscopic topological features of amyloid fibrils, that is, the evolution of fibril periodicity as a function of the ionic strength of the solution and of the fibril width. A universal mesoscopic structural signature of the fibrils emerges from this picture, predicting a general, parameter-free law for the periodicity of the fibrils, that depends solely on the number of protofilaments per fibril. These predictions are validated experimentally and conclusively highlight the role of competing electrostatic and elastic contributions as the main players in the establishment of amyloid fibrils structure.

2014

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Énergie potentielle

L'énergie potentielle d'un système physique est l'énergie liée à une interaction, qui a la capacité de se transformer en d'autres formes d'énergie, le plus souvent en énergie cinétique, une énergie

Énergie (physique)

En physique, l'énergie est une grandeur qui mesure la capacité d'un système à modifier un état, à produire un travail entraînant un mouvement, un rayonnement électromagnétique ou de la chaleur. Dans

Travail d'une force

Le travail d'une force est l'énergie fournie par cette force lorsque son point d'application se déplace (l'objet subissant la force se déplace ou se déforme). Il est responsable de la variation de l

MICRO-200: Mechanism Design I

Ce cours introduit les bases de la mécanique des structures : calcul des contraintes et déformations provoquées par les forces extérieures et calcul des déformations. Ces enseignements théoriques sont appliqués à la conception des éléments importants des mécanismes de précision.

ME-232: Mechanics of structures (For GM)

L'étudiant acquiert les bases de l'analyse des contraintes et déformation des poutres élastiques linéaires soumises à la traction, cisaillement, torsion, flexion; les coefficients d'influence et la méthode de l'énergie pour analyser des systèmes isostatiques et hyperstatiques; critères de rupture.

MSE-101(b): Materials: from chemistry to properties

This class will teach the fundamental concepts regarding materials and their micro-structure, as well as the equilibrium and dynamics of chemical reactions. A link will be made between these concepts and the mechanical, thermal, electrical, magnetic and optical properties of materials.