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In the current work is presented a comparison of non-right-angle ship-ship collision events generated with numerical simulations based on nonlinear explicit finite element method and super-element method. The purpose is to analyse the limitations of the two approaches when non-perpendicular collisions occur on the side structure of a ship which is not considered at rest. Besides, facing the importance of the inclusion of crashworthiness analysis in ship construction, a first analytical tool for the pre-design stage is proposed in collaboration with the shipyard Chantiers de L’Atlantique in the second part of this document.
Since ship collisions are considered as the most hazardous accidental state, it is first highlighted the attempts of the research marine structure community in the understanding of this event. The literature about numerical analysis of ship collision is reviewed to find the existing procedures to assess the resistance force of structures subjected to impact loads. The relation between the existing methods is presented as well as the current limitations in the field of collision of ship structures. It is found the requirements from the Classification Societies regarding ship collision and grounding are still at a low level of assessment.
A recent benchmark collision study is used for the validation of parametrized collision scenarios made up with LS-Dyna. The setup of the simulation file is described considering the association with the MCOL code to assess the rigid body dynamics of the ships, finding differences due to the rupture criteria assumed. Non-right-angle collisions were generated considering the struck ship has initial velocity and the damage is evaluated with the side penetration and the internal energy dissipated. The same collision scenarios are reproduced with the super-element-based SHARP program and the comparison of results is analysed. It was found how the closed-form expression of the SHARP program limits the deformation energy contribution from other elements that according to LS-Dyna are deforming in the process. The sliding energy was found to be more important in narrow collision angles when both ships have opposite directions.
An analytical tool based on a shared-energy design procedure is also proposed for the pre-design stage of impact loads in the ship construction. The deformation energy obtained by the damaged volume in the crushing process of both deformable ships is expected to be like the initial kinetic energy mainly influenced by the initial velocity of the striking ship. A threshold value for the velocity of the striking ship is estimated from the maximum penetration expected in the struck ship to avoid a large-scale explosion event. Simulations in LS-Dyna are generated to find the influence of the damage due to a high-velocity impact and to the striking ship bow. En este trabajo se presenta una comparación de colisiones no perpendiculares de buques utilizando simulaciones numéricas basadas en el método de elementos finitos explícito no lineal y el método de super elementos. El fin es analizar las limitaciones de los dos enfoques en el caso de colisiones no perpendiculares que afectan el costado de un barco en movimiento. Además, contemplando la importancia de evaluar la resistencia a colisiones, en una segunda sección de este documento se busca proponer una primera herramienta que pueda estimar la misma en la etapa preliminar de diseño en colaboración con el astillero Chantiers de L’Atlantique.
Ya que las colisiones entre buques son consideradas como el estado accidental más peligroso, primero se destacan los intentos por la comunidad de investigación en estructuras navales por entender este suceso. Se revisa la literatura referida al análisis numérico de las colisiones de barcos para identificar los procedimientos actuales en la evaluación la resistencia estructural de objetos sujetos a cargas de impacto. Se presenta una relación entre los dichos métodos, así como también las limitaciones actuales en el campo de estudio de colisiones entre estructuras de buques. Se revela que aún se encuentran en bajo nivel de evaluación los requerimientos actuales de las Sociedades Clasificadores referidos a los problemas estructurales de colisiones de buques y varamiento.
En una siguiente etapa, se utilizó un reciente estudio de colisiones como base para la validación de un escenario de colisiones parametrizado utilizando LS-Dyna. La configuración del archivo de simulación es descrita considerando su relación con la subrutina MCOL para evaluar la dinámica externa de los buques considerados como cuerpos rígidos, donde finalmente se encontraron diferencias debido al criterio de falla de material asumido. Luego, considerando velocidad inicial en el barco golpeado se generaron colisiones no perpendiculares evaluando el daño perpetrado en base a la penetración en el costado y la energía interna disipada. Los mismos escenarios fueron reproducidos en el programa SHARP para después ser comparados y analizados. Se encontró que las formulaciones del programa SHARP limitan la contribución en la energía de deformación de diferentes componentes que de acuerdo con LS-Dyna, también se deforman. Además, se obtuvo que la energía debido a la fricción de componentes es más importante cuando se evalúan colisiones con ángulos agudos.
En una última sección, se propone una herramienta analítica basada en un diseño-compartido de energía para evaluar cargas de impacto en la etapa preliminar de diseño. La energía de deformación se obtiene en función del volumen de material afectado en ambos barcos que se asume iguale a la energía cinética inicial del barco que choca. Se sugiere una velocidad límite para este barco estimada a partir de la máxima penetración permitida en el barco golpeado para evitar una explosión a larga escala. También, se generaron simulaciones con LS-Dyna para encontrar diferencias en el daño del barco, debido a un impacto a alta velocidad y a las formas de la proa del barco que impacta.

Finite Element Method --- Ship Collision --- SuperElement --- Non-linear FEM --- Ingénierie, informatique & technologie > Ingénierie mécanique

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L’évolution de la structure des protéines lors de leur passage en phase gazeuse est encore méconnue. Dans le cadre de ce mémoire, nous avons utilisé le marquage covalent pour modifier les chaînes latérales d’un type d’acide aminé ciblé afin d’en apprendre davantage sur son rôle structural lors du passage en phase gazeuse. Nous avons étudié l’impact du marquage des lysines sur le comportement en phase gazeuse d’une protéine modèle, le cytochrome C en utilisant le dépliement induit par collision couplé à la mobilité ionique. Différents marqueurs ont été utilisés et leurs effets sont comparés. Ces tests sont accompagnés de l’élaboration d’un protocole efficace, d’une étude de l’impact du marquage sur la structure de la protéine en solution et d’une étude sur les sites de marquage et leur réactivité respectives. Nos résultats montrent que le marquage des lysines par des groupement -Ac entraîne l’adoption de conformation plus compactes, ce qui met en évidence leur rôle structurel en phase gazeuse. La comparaison de l’impact des groupements -Ac avec celui de groupements plus volumineux portant un deux ou trois phényls révèle deux effets dépendants du groupement lié. Une augmentation de l’impact du marqueur sur la structure pour les marqueurs plus volumineux et une augmentation de la section efficace de collision de la protéine marquée. Ces résultats ouvrent la voix à de nombreuses perspectives utilisant la même technique mais en variant la protéine cible ou les marqueurs utilisés afin d’améliorer notre compréhension des phénomènes en jeu.

mobilité ionique --- spectrométrie de masse --- dépliement induit par collision --- NHS-ester --- cytochrome c --- Physique, chimie, mathématiques & sciences de la terre > Chimie

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Recent industrial criteria increasingly require the production of multi-material components. However, the manufacturing requirements of these components are not met by conventional welding techniques. Alternative solid-state technologies, such as impact-based processes, must be considered. The impact welding family is composed of several processes, such as explosion welding, magnetic pulse welding, vaporizing foil actuator welding, and laser impact welding. These processes present very different length scales, providing the impact welding family with a broad applicability range. A sample of the cutting-edge research that is being conducted on the multidisciplinary field of impact welding is presented in this book.

Technology: general issues --- dissimilar materials --- interlayer --- vaporizing foil actuators welding --- impact welding --- impact velocity --- impact angle --- welding interface --- flyer velocity --- energy efficiency --- peak velocity --- flyer rebound --- flyer size --- confinement layer --- explosive welding --- Ti6Al4V/Al-1060 --- microstructure --- mechanical properties --- smooth particle hydrodynamic (SPH) --- high-velocity impact welding --- smoothed particle hydrodynamics simulation --- welding window --- gelatin --- thin aluminum plate --- magnesium alloys --- LPSO phase --- cellular metal --- composite structure --- unidirectional cellular metal --- explosive compaction --- high-energy-rate forming --- tantalum/copper/stainless steel clads --- severe plastic deformation --- SEM/EBSD --- microhardness --- magnetic pulse welding --- dissimilar metals --- surface preparation --- interface --- aluminum --- carbon steel --- stainless steel --- collision welding --- pressure welding --- process glare --- jet --- cloud of particles --- shock compression --- surface roughness --- collision conditions --- model test rig --- welding mechanisms --- n/a

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Recent industrial criteria increasingly require the production of multi-material components. However, the manufacturing requirements of these components are not met by conventional welding techniques. Alternative solid-state technologies, such as impact-based processes, must be considered. The impact welding family is composed of several processes, such as explosion welding, magnetic pulse welding, vaporizing foil actuator welding, and laser impact welding. These processes present very different length scales, providing the impact welding family with a broad applicability range. A sample of the cutting-edge research that is being conducted on the multidisciplinary field of impact welding is presented in this book.

dissimilar materials --- interlayer --- vaporizing foil actuators welding --- impact welding --- impact velocity --- impact angle --- welding interface --- flyer velocity --- energy efficiency --- peak velocity --- flyer rebound --- flyer size --- confinement layer --- explosive welding --- Ti6Al4V/Al-1060 --- microstructure --- mechanical properties --- smooth particle hydrodynamic (SPH) --- high-velocity impact welding --- smoothed particle hydrodynamics simulation --- welding window --- gelatin --- thin aluminum plate --- magnesium alloys --- LPSO phase --- cellular metal --- composite structure --- unidirectional cellular metal --- explosive compaction --- high-energy-rate forming --- tantalum/copper/stainless steel clads --- severe plastic deformation --- SEM/EBSD --- microhardness --- magnetic pulse welding --- dissimilar metals --- surface preparation --- interface --- aluminum --- carbon steel --- stainless steel --- collision welding --- pressure welding --- process glare --- jet --- cloud of particles --- shock compression --- surface roughness --- collision conditions --- model test rig --- welding mechanisms --- n/a

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Connected and automated vehicles have revolutionized the way we move, granting new services on roads. This Special Issue collects contributions that address reliable and ultra-low-latency vehicular applications that range from advancements at the access layer, such as using the visible light spectrum to accommodate ultra-low-latency applications, to data dissemination solutions. Further, articles discuss edge computing, neural network-based techniques, and the use of reconfigurable intelligent surfaces (RIS) to boost throughput and enhance coverage.

vehicular networks --- 5G --- C-RAN --- resource allocation --- edge computing --- optimization --- vehicle-to-everything communication --- pedestrian --- vehicles --- safety --- automotive --- damper --- convolutional neural networks --- fault detection --- diagnosis --- machine learning --- deep learning --- connected vehicles --- reconfigurable meta-surface --- smart environment --- cooperative driving --- vulnerable road user detection --- collision probability --- probabilistic flooding --- vehicular communication --- visible light communications --- 5G networks --- smart vehicles --- field trials --- infrastructure-to-vehicle --- vehicle-to-vehicle --- Intelligent Transportation Systems --- Visible Light Communication --- Fresnel lenses --- AODV --- end-to-end delay --- packet loss ratio --- throughput --- VANET --- n/a