Este trabajo fue apoyado por la NASA subvención NNX11AC68G y la Institución Carnegie de Washington. Doy las gracias a Chi Zhang por su ayuda con la recopilación de datos. También agradezco a Anat Shahar y Valerie Hillgren por sus útiles comentarios de este manuscrito.

1. Preparar materiales de partida y las Cámaras de muestra <ol><li> Preparar dos tipos de materiales de partida, (1) una mezcla de silicato de olivino natural y polvo de hierro metálico con 10% en peso de azufre (metal / proporciones de silicato que van de 4 a 30% en peso) para la simulación de percolación de aleación de hierro líquido en una matriz de silicato sólida durante la formación del núcleo inicial de un pequeño cuerpo planetario, y (2) una mezcla homogénea de finamente a tierra de hierro puro y sulfuro de hierro para la determinación del planetario cristalización núcleo interno. </li><li> Moler los materiales de partida a polvo mezclado bien en virtud de etanol en un mortero de ágata durante una hora y se secó a 100 ° C. </li><li> Cargue el material de partida en una MgO sinterizado o Al 2 O 3 cápsulas (típicamente 1,5 mm de diámetro y 1,5 de largo), y luego se coloca en un conjunto de celda de alta presión para los experimentos multi-yunque. </li><li> Cargar la mezcla de Fe-FeS en una pequeña cámara de muestra (típicamente 100 m de diámetro y 25 y #181; m de espesor) perforado en una junta de renio preindented para los experimentos con láser de calefacción en la celda de yunque de diamante. Sandwich la mezcla de Fe-FeS entre las capas de NaCl que sirven como aislantes térmicos. </li></ol> 2. De alta presión y alta temperatura Experimentos en el aparato multi-yunque <ol><li> El conjunto de celda de alta presión de múltiples yunque consta de un octaedro de MgO como un medio de presión, un manguito de ZrO 2 como el aislante térmico, y un renio cilíndrico o un calentador de grafito. La cápsula de la muestra se ajusta dentro del calentador. Un termopar tipo C se inserta en la cámara de muestra para determinar la temperatura de la muestra. </li><li> Coloque el conjunto de alta presión en un aparato de alta presión multi-yunque para presurización. </li><li> El aparato multi-yunque consiste en una prensa hidráulica de 1500 toneladas y un módulo de presión que contiene un anillo de retención con seis cuñas de empuje desmontable formando una cavidad cúbica en el centro 15. La cavidad cúbica houses ocho cubos de metal duro con esquinas truncadas. Los cubos truncadas, que convergen en el conjunto de celda de octaedro, están separadas una de otra por las juntas compresibles. El ariete hidráulico transmite la fuerza efectiva en el conjunto de la muestra por una de dos etapas de configuración de yunque. Figura 1 ilustra el procedimiento experimental para el experimento de múltiples yunque. </li><li> Presurizar la muestra a una presión objetivo entre 2-27 GPa a temperatura ambiente sobre la base de FIX-punto de la curva de calibración de presión 16, y luego calentar a las temperaturas experimentales de hasta 2.300 ° C por calentamiento por resistencia eléctrica; mantener el experimento a una temperatura constante durante la duración del experimento, y apague la alimentación para apagar la muestra a temperatura ambiente al final del experimento. </li><li> Liberar la presión lentamente mediante la apertura de la válvula de aceite hidráulico y recuperar la carga experimental. </li></ol> 3. Los experimentos con láser de calefacción en elDiamond-yunque Celular <ol><li> Presión en una celda de yunque de diamante se genera entre dos yunques de diamante de cristal único de calidad gema (aproximadamente 0,25 quilates cada uno). Utilizamos una célula de diamante yunque simétrica para conducir los yunques opuestos perfectamente alineados con un sistema de pistón-cilindro. La célula es capaz de generar presiones correspondientes a las condiciones de presión de núcleo de la Tierra 17. De alta temperatura se consigue mediante calentamiento por láser en la celda de diamante yunque. Nosotros utilizamos un sistema en el Avance Photon Source (APS), que se basa en una técnica de calentamiento por láser de doble cara y se compone de dos láseres de fibra óptica, para calentar la muestra desde ambos lados, y dos sistemas de espectroradiométricas para mediciones de temperatura en ambos lados 18. El sistema está diseñado para generar una gran mancha de calentamiento (25 m de diámetro), minimizar los gradientes de temperatura de la muestra tanto radial como axialmente en la celda de yunque de diamante, y maximizar la estabilidad de calefacción. La figura 2 muestra esquemáticas de la configuración experimental para el experimento de láser de caldeo en la celda de yunque de diamante con una imagen del punto de láser-calefacción. </li><li> Alinear los yunques de diamante con 300 micras culets y preindent una junta de renio a un espesor de 30 micras de un espesor inicial de 250 micras. </li><li> Haga un agujero en la junta preindented con un diámetro de 120 micras en el centro, y la carga de la muestra en el agujero. </li><li> Presurizar la muestra a una presión objetivo a temperatura ambiente, y a continuación, calentar la muestra mediante el aumento de la potencia del láser mientras que toma mediciones de temperatura y en medidas de difracción de rayos X in situ en la instalación de sincrotrón. </li><li> Apagar la potencia del láser para apagar la muestra cuando la fusión parcial se detecta por un cambio en la radiación térmica y a partir del patrón de difracción. </li><li> Recuperar la muestra calentada para la caracterización ex situ. </li></ol> 4. Recuperación de muestras y análisis <ol><li> MoUNT la muestra multi-yunque recuperado en resina epoxi y pulir su superficie mediante un conjunto de grano de polvo de diamante de 150 micras a 0,25 micras. </li><li> Carbono-capa de la superficie de la muestra y cargarlo en la cámara de muestra de un instrumento Zeiss traviesa Auriga FIB / SEM (Figura 3A) para el análisis. </li><li> Alinear la muestra hasta el punto coincidente de la FIB y SEM a una distancia de trabajo de 5 mm (Figura 3B), y luego premill la muestra para exponer un volumen de 15 x 20 x 20 m 3 (Figura 3C). </li><li> Tomar imágenes de SEM en un intervalo de 25 nm utilizando la rebanada y función de vista en el instrumento Zeiss Auriga FIB / SEM (grabar automáticamente una serie de imágenes después de la molienda del haz iónico y con resolución de imagen típica de aproximadamente 35 nm). </li><li> Entrada de los archivos de datos de imágenes al software de visualización y reconstruir imágenes 3D para visualizar la distribución de la masa fundida y la conectividad en la muestra templada (Figura 3D). </li></ol>

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Ningún conflicto de interés declarado.

Las técnicas para los experimentos múltiples de yunque están bien establecidos, la generación de presión y temperatura estables durante un período prolongado de tiempo de ejecución y la producción de volumen de muestra relativamente grande. Es una poderosa herramienta para simular los procesos interiores de planetas, especialmente para experimentos, como la filtración de masa fundida, que requieren cierto volumen de muestra. La limitación es la presión máxima alcanzable, hasta 27 GPa con carburo de tungsteno...

Los planetas terrestres como la Tierra, Venus, Marte y Mercurio son cuerpos planetarios diferenciados que consisten en un manto de silicatos y un núcleo metálico. El modelo de formación planetaria moderna sugiere que los planetas terrestres se formaron a partir de colisiones de embriones planetarios-Moon-to del tamaño de Marte que crecen de-kilometros de tamaño o más grandes planetesimales mediante interacciones gravitacionales 1-2. Los planetesimales fueron probablemente ya diferenciarse una vez que las aleaciones de hierro metálico alcanzó la temperatura de fusión debido a la calefacción a partir de fuentes tales como la desintegración radiactiva de los isótopos de vida corta como 26 Al y Fe 60, el impacto, y la liberación del potencial de energía 3. Es importante entender cómo percola el metal líquido a través de una matriz de silicato durante la diferenciación temprana. Diferenciación Planet podría proceder a través de la separación líquido-líquido eficiente o por percolación de metal líquido en una matriz de silicato sólido, dependiendoen el tamaño y la temperatura interior de los cuerpos planetarios. La percolación de metal líquido en la matriz de silicato sólido es probablemente un proceso dominante en la diferenciación inicial cuando la temperatura no es lo suficientemente alta como para fundir todo el cuerpo planetario. La eficiencia de percolación depende del ángulo diedro, determinado por las energías interfaciales de las interfaces sólido-sólido y sólido-líquido. Podemos simular este proceso en el laboratorio mediante la realización de experimentos de alta presión y alta temperatura de una mezcla de aleación de hierro y silicatos. Estudios recientes 4-7 han investigado la capacidad de humectación de las aleaciones de hierro líquido en una matriz de silicato sólido a alta presión y temperatura. Utilizaron un método convencional para medir la distribución de frecuencias relativas de los ángulos diedros aparentes entre el metal líquido templado y granos de silicato en las secciones transversales pulidas para la determinación del verdadero ángulo diedro. El método convencional produce relativamente grande UNCertainties en el ángulo diedro medido y el posible sesgo en función de las estadísticas de muestreo. Aquí les presentamos una nueva técnica de imagen para visualizar la distribución de metal líquido en la matriz de silicato en tres dimensiones (3D) por combinación de fresado FIB y de alta resolución de emisión de campo de imagen SEM. La nueva técnica de formación de imágenes proporciona una determinación precisa del ángulo diedro y medida cuantitativa de la fracción de volumen y la conectividad de la fase líquida. El núcleo de la Tierra se formó en un tiempo relativamente corto (&lt;100 millones de años) 8, presumiblemente en estado líquido en su historia temprana. Marte y Mercurio también tienen núcleos líquidos basados ​​en la deformación de las mareas solares partir de los datos de seguimiento de la radio de la Mars Global Surveyor 9 y los patrones de speckle radar atados a la rotación planetaria 10, respectivamente. Modelos de evolución térmica y experimentos de fusión de alta presión sobre materiales de la base de apoyo, además, un núcleo marciano líquido11-12. Recientes datos de la nave espacial MESSENGER proporcionan evidencia adicional para un núcleo líquido de Mercurio 13. Incluso la pequeña Luna es probable que tenga un pequeño núcleo líquido basado en recientes reanálisis de Appollo sismogramas lunares 14. Núcleos planetarios líquidos son consistentes con energía de alta acumulación en la fase temprana de la formación de planetas. El posterior enfriamiento puede conducir a la formación de núcleo interno sólido de algunos planetas. Los datos sísmicos han revelado que la tierra se compone de un núcleo externo líquido y un núcleo interior sólido. La formación del núcleo interno tiene importantes implicaciones para la dinámica del núcleo impulsado por convecciones térmicas y de composición y la generación del campo magnético del planeta. La solidificación del núcleo interno es controlado por la temperatura de fusión de los materiales de núcleo y la evolución térmica del núcleo. La formación del núcleo de planetas terrestres compartida caminos de acreción similares y la composición química de los núcleos se considera que be dominada por el hierro con alrededor de 10% en peso elementos ligeros tales como azufre (S), silicio (Si), de oxígeno (O), carbono (C), y de hidrógeno (H) 15. Es esencial tener un conocimiento de las relaciones de fusión en los sistemas relevantes para el núcleo, tal como Fe-FeS, Fe-C, Fe-FeO, Fe-FEH y Fe-FeSiat alta presión, con el fin de entender la composición de los núcleos planetarios. En este estudio, vamos a demostrar los experimentos llevados a cabo en el dispositivo de múltiples yunque y de células de yunque de diamante, imitando las condiciones de los núcleos planetarios. Los experimentos proporcionan información sobre la secuencia de la cristalización y el elemento de partición entre el metal sólido y el líquido, lo que lleva a una mejor comprensión de los requisitos de la cristalización núcleo interno y la distribución de los elementos de luz entre el núcleo interno y el núcleo cristalino líquido fuera. Para extender las relaciones de fusión a muy altas presiones, se han desarrollado nuevas técnicas para analizar las muestras inactivadas recuperados de láser calienta un diamanteexperimentos de células nvil. Con el fresado FIB precisión del punto de láser-calefacción, determinamos fusión utilizando criterios textura de extinción fotografiados con alta resolución de SEM y análisis químico cuantitativo con un detector de deriva de silicio a una resolución espacial submicron. Aquí resumimos dos series de experimentos para simular la formación del núcleo planetario por percolación de metal se funde en matriz de silicato durante la acreción temprana y la cristalización del núcleo interno de un enfriamiento posterior. La simulación tiene como objetivo entender los dos procesos importantes durante la evolución del núcleo planetario.

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			<td class="xl63" height="43" style="height:32.25pt;width:66pt" width="88">Multi-anvil apparatus</td>
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			<td class="xl63" style="border-left:none;width:66pt" width="88">Home Builder</td>
			<td class="xl63" style="border-left:none;width:66pt" width="88"> </td>
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			<td class="xl63" height="43" style="height:32.25pt;border-top:none;
 width:66pt" width="88">Diamond-anvil cell</td>
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			<td class="xl63" style="border-top:none;border-left:none;width:66pt" width="88">Home Builder</td>
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			<td class="xl63" height="64" style="height:48.0pt;border-top:none;
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			<td class="xl63" style="border-top:none;border-left:none;width:66pt" width="88">Designed by beamline staff</td>
			<td class="xl63" style="border-top:none;border-left:none;width:66pt" width="88"> Public beamline</td>
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			<td class="xl63" style="border-top:none;border-left:none;width:66pt" width="88">Auriga</td>
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			<td class="xl63" style="border-top:none;border-left:none;width:66pt" width="88">Fire for materials science</td>
			<td class="xl63" style="border-top:none;border-left:none;width:66pt" width="88"> </td>
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simulation of the planetary interior differentiation processes in the laboratory

Un interior del planeta se encuentra bajo condiciones de alta presión y alta temperatura y tiene una estructura en capas. Hay dos procesos importantes que condujeron a que la estructura en capas, (1) percolación de metal líquido en una matriz de silicato sólido por diferenciación planeta, y (2) la cristalización núcleo interno mediante la posterior planeta de refrigeración. Llevamos a cabo los experimentos de alta presión y alta temperatura para simular los procesos en el laboratorio. Formación de núcleo planetario percolación depende de la eficiencia de la filtración de masa fundida, que es controlada por el ángulo diedro (humectante). La simulación de percolación incluye calentar la muestra a alta presión a una temperatura objetivo en el que aleación de hierro-azufre es fundido mientras que el silicato se mantiene sólido, y luego determinar el verdadero ángulo diedro para evaluar el estilo de la migración de líquido en una matriz cristalina mediante la visualización 3D. La representación de volumen 3D se consigue cortando la muestra recuperada con un haz de iones (FIB) y taimagen Rey del SEM de cada rebanada con un instrumento travesaño FIB / SEM. El segundo conjunto de experimentos está diseñado para comprender la cristalización y elemento de distribución de núcleo interno entre el núcleo externo líquido y el núcleo interno sólido mediante la determinación de la temperatura de fusión y elemento de segmentación a alta presión. Los experimentos de fusión se llevan a cabo en el aparato de múltiples yunque hasta 27 GPa y extenderse a una mayor presión en la celda de yunque de diamante con láser de calefacción. Hemos desarrollado técnicas para recuperar pequeñas muestras calentadas por molienda FIB precisión y obtener imágenes de alta resolución de la mancha láser calienta que muestran la fusión de textura a alta presión. Mediante el análisis de la composición química del líquido coexistente y fases sólidas, se determina con precisión la curva de liquidus, proporcionando los datos necesarios para entender el proceso de cristalización del núcleo interno.

Hemos llevado a cabo una serie de experimentos utilizando mezclas de San Carlos olivino y aleación de metal de Fe-FeS con diferentes proporciones de metal-silicatos, como materiales de partida. El contenido de S del metal es 10% en peso S. Aquí se muestran algunos resultados representativos de los experimentos de alta presión realizadas en 6 GPa y 1800 ° C, utilizando conjuntos múltiples de yunque bien calibrados 15. En las condiciones experimentales, la aleación de metal de Fe-FeS es completamente fund...

Watch this Scientific Journal Video about Simulation of the Planetary Interior Differentiation Processes in the Laboratory at JoVE.com

Simulation of the Planetary Interior Differentiation Processes in the Laboratory

Los experimentos de alta presión y alta temperatura que se describen aquí imitan planeta procesos de diferenciación interiores. Los procesos son visualizados y mejor entendidos por imágenes de alta resolución en 3D y el análisis químico cuantitativo.

Simulación de la Planetary Interior Diferenciación Procesos en el Laboratorio

A planetary interior is under high-pressure and high-temperature conditions and it has a layered structure. There are two important processes that led to ...

simulation-planetary-interior-differentiation-processes

Research

JoVE Journal

Engineering

11.5K vistas.  Carnegie Institution of Washington.  Los experimentos de alta presión y alta temperatura que se describen aquí imitan planeta procesos de diferenciación interiores. Los procesos son visualizados y mejor entendidos por imágenes de alta resolución en 3D y el análisis químico cuantitativo. 

Video: Simulation of the Planetary Interior Differentiation Processes in the Laboratory

Revealing Dynamic Processes of Materials in Liquids Using Liquid Cell Transmission Electron Microscopy

The recent development for in situ transmission electron microscopy, which allows imaging through liquids with high spatial resolution, has attracted significant interests across the research fields of materials science, physics, chemistry and biology. The key enabling technology is a liquid cell. We fabricate liquid cells with thin viewing windows through a sequential microfabrication process, including silicon nitride membrane deposition, photolithographic patterning, wafer etching, cell bonding, etc. A liquid cell with the dimensions of a regular TEM grid can fit in any standard TEM sample holder. About 100 nanoliters reaction solution is loaded into the reservoirs and about 30 picoliters liquid is drawn into the viewing windows by capillary force. Subsequently, the cell is sealed and loaded into a microscope for in situ imaging. Inside the TEM, the electron beam goes through the thin liquid layer sandwiched between two silicon nitride membranes. Dynamic processes of nanoparticles in liquids, such as nucleation and growth of nanocrystals, diffusion and assembly of nanoparticles, etc., have been imaged in real time with sub-nanometer resolution. We have also applied this method to other research areas, e.g., imaging proteins in water. Liquid cell TEM is poised to play a major role in revealing dynamic processes of materials in their working environments. It may also bring high impact in the study of biological processes in their native environment.

We have developed a self-contained liquid cell, which allows imaging through liquids using a transmission electron microscope. Dynamic processes of nanoparticles in liquids can be revealed in real time with sub-nanometer resolution.

Revelando los procesos dinámicos de los materiales en líquidos con líquido de transmisión celular Microscopía Electrónica

The recent development for in situ transmission electron microscopy, which allows imaging through liquids with high spatial resolution, has attracted ...

Investigación

Ingeniería

Flame Experiments at the Advanced Light Source: New Insights into Soot Formation Processes

The following experimental protocols and the accompanying video are concerned with the flame experiments that are performed at the Chemical Dynamics Beamline of the Advanced Light Source (ALS) of the Lawrence Berkeley National Laboratory1-4. This video demonstrates how the complex chemical structures of laboratory-based model flames are analyzed using flame-sampling mass spectrometry with tunable synchrotron-generated vacuum-ultraviolet (VUV) radiation. This experimental approach combines isomer-resolving capabilities with high sensitivity and a large dynamic range5,6. The first part of the video describes experiments involving burner-stabilized, reduced-pressure (20-80 mbar) laminar premixed flames. A small hydrocarbon fuel was used for the selected flame to demonstrate the general experimental approach. It is shown how species&#8217; profiles are acquired as a function of distance from the burner surface and how the tunability of the VUV photon energy is used advantageously to identify many combustion intermediates based on their ionization energies. For example, this technique has been used to study gas-phase aspects of the soot-formation processes, and the video shows how the resonance-stabilized radicals, such as C3H3, C3H5, and i-C4H5, are identified as important intermediates7. The work has been focused on soot formation processes, and, from the chemical point of view, this process is very intriguing because chemical structures containing millions of carbon atoms are assembled from a fuel molecule possessing only a few carbon atoms in just milliseconds. The second part of the video highlights a new experiment, in which an opposed-flow diffusion flame and synchrotron-based aerosol mass spectrometry are used to study the chemical composition of the combustion-generated soot particles4. The experimental results indicate that the widely accepted H-abstraction-C2H2-addition (HACA) mechanism is not the sole molecular growth process responsible for the formation of the observed large polycyclic aromatic hydrocarbons (PAHs).

Gas sampling from laboratory-scale flames with online analysis of all species by mass spectrometry is a powerful method to investigate the complex mixture of chemical compounds occurring during combustion processes. Coupled with tunable soft ionization via synchrotron-generated vacuum-ultraviolet radiation, this technique provides isomer-resolved information and potentially fragment-free mass spectra.

Los experimentos de la llama a la fuente de luz avanzada: nuevos conocimientos sobre los procesos de formación de hollín

The following experimental protocols and the accompanying video are concerned with the flame experiments that are performed at the Chemical Dynamics ...

Laboratory Drop Towers for the Experimental Simulation of Dust-aggregate Collisions in the Early Solar System

For the purpose of investigating the evolution of dust aggregates in the early Solar System, we developed two vacuum drop towers in which fragile dust aggregates with sizes up to ~10 cm and porosities up to 70% can be collided. One of the drop towers is primarily used for very low impact speeds down to below 0.01 m/sec and makes use of a double release mechanism. Collisions are recorded in stereo-view by two high-speed cameras, which fall along the glass vacuum tube in the center-of-mass frame of the two dust aggregates. The other free-fall tower makes use of an electromagnetic accelerator that is capable of gently accelerating dust aggregates to up to 5 m/sec. In combination with the release of another dust aggregate to free fall, collision speeds up to ~10 m/sec can be achieved. Here, two fixed high-speed cameras record the collision events. In both drop towers, the dust aggregates are in free fall during the collision so that they are weightless and match the conditions in the early Solar System.

We present a technique to achieve low-velocity to intermediate-velocity collisions between fragile dust aggregates in the laboratory. For this purpose, two vacuum drop-tower setups have been developed that allow collision velocities between &#60;0.01 and ~10 m/sec. The collision events are recorded by high-speed imaging.

Laboratorio torres de caída para el experimental Simulación de colisiones de polvo acumuladas en el Sistema Solar temprano

For the purpose of investigating the evolution of dust aggregates in the early Solar System, we developed two vacuum drop towers in which fragile dust ...

Quantification of Hydrogen Concentrations in Surface and Interface Layers and Bulk Materials through Depth Profiling with Nuclear Reaction Analysis

Nuclear reaction analysis (NRA) via the resonant 1H(15N,&#945;&#947;)12C reaction is a highly effective method of depth profiling that quantitatively and non-destructively reveals the hydrogen density distribution at surfaces, at interfaces, and in the volume of solid materials with high depth resolution. The technique applies a 15N ion beam of 6.385 MeV provided by an electrostatic accelerator and specifically detects the 1H isotope in depths up to about 2 &#956;m from the target surface. Surface H coverages are measured with a sensitivity in the order of ~1013 cm-2 (~1% of a typical atomic monolayer density) and H volume concentrations with a detection limit of ~1018 cm-3 (~100 at. ppm). The near-surface depth resolution is 2-5 nm for surface-normal 15N ion incidence onto the target and can be enhanced to values below 1 nm for very flat targets by adopting a surface-grazing incidence geometry. The method is versatile and readily applied to any high vacuum compatible homogeneous material with a smooth surface (no pores). Electrically conductive targets usually tolerate the ion beam irradiation with negligible degradation. Hydrogen quantitation and correct depth analysis require knowledge of the elementary composition (besides hydrogen) and mass density of the target material. Especially in combination with ultra-high vacuum methods for in-situ target preparation and characterization, 1H(15N,&#945;&#947;)12C NRA is ideally suited for hydrogen analysis at atomically controlled surfaces and nanostructured interfaces. We exemplarily demonstrate here the application of 15N NRA at the MALT Tandem accelerator facility of the University of Tokyo to (1) quantitatively measure the surface coverage and the bulk concentration of hydrogen in the near-surface region of a H2 exposed Pd(110) single crystal, and (2) to determine the depth location and layer density of hydrogen near the interfaces of thin SiO2 films on Si(100).

We illustrate the application of 1H(15N,&#945;&#947;)12C resonant nuclear reaction analysis (NRA) to quantitatively evaluate the density of hydrogen atoms on the surface, in the volume, and at an interfacial layer of solid materials. The near-surface hydrogen depth profiling of a Pd(110) single crystal and of SiO2/Si(100) stacks is described.

La cuantificación de las concentraciones de hidrógeno en superficies e interfaces de capas y materiales a granel a través de perfiles de profundidad con el análisis de Reacción nuclear

Nuclear reaction analysis (NRA) via the resonant 1H(15N,&#945;&#947;)12C reaction is a highly effective method of depth profiling that quantitatively and ...

Simulation of Human-induced Vibrations Based on the Characterized In-field Pedestrian Behavior

For slender and lightweight structures, vibration serviceability is a matter of growing concern, often constituting the critical design requirement. With designs governed by the dynamic performance under human-induced loads, a strong demand exists for the verification and refinement of currently available load models. The present contribution uses a 3D inertial motion tracking technique for the characterization of the in-field pedestrian behavior. The technique is first tested in laboratory experiments with simultaneous registration of the corresponding ground reaction forces. The experiments include walking persons as well as rhythmical human activities such as jumping and bobbing. It is shown that the registered motion allows for the identification of the time variant pacing rate of the activity. Together with the weight of the person and the application of generalized force models available in literature, the identified time-variant pacing rate allows to characterize the human-induced loads. In addition, time synchronization among the wireless motion trackers allows identifying the synchronization rate among the participants. Subsequently, the technique is used on a real footbridge where both the motion of the persons and the induced structural vibrations are registered. It is shown how the characterized in-field pedestrian behavior can be applied to simulate the induced structural response. It is demonstrated that the in situ identified pacing rate and synchronization rate constitute an essential input for the simulation and verification of the human-induced loads. The main potential applications of the proposed methodology are the estimation of human-structure interaction phenomena and the development of suitable models for the correlation among pedestrians in real traffic conditions.

A protocol is presented for the characterization of the in-field pedestrian behavior and the simulation of the resulting structural response. Field-tests demonstrate that the in situ identified pacing rate and synchronization rate among the participants constitute an essential input for the simulation and verification of the human-induced loads.

Simulación de vibraciones humanas inducida Basado en la calificó el comportamiento peatonal en el terreno

For slender and lightweight structures, vibration serviceability is a matter of growing concern, often constituting the critical design requirement. With ...

Knowledge Based Cloud FE Simulation of Sheet Metal Forming Processes

The use of Finite Element (FE) simulation software to adequately predict the outcome of sheet metal forming processes is crucial to enhancing the efficiency and lowering the development time of such processes, whilst reducing costs involved in trial-and-error prototyping. Recent focus on the substitution of steel components with aluminum alloy alternatives in the automotive and aerospace sectors has increased the need to simulate the forming behavior of such alloys for ever more complex component geometries. However these alloys, and in particular their high strength variants, exhibit limited formability at room temperature, and high temperature manufacturing technologies have been developed to form them. Consequently, advanced constitutive models are required to reflect the associated temperature and strain rate effects. Simulating such behavior is computationally very expensive using conventional FE simulation techniques.
This paper presents a novel Knowledge Based Cloud FE (KBC-FE) simulation technique that combines advanced material and friction models with conventional FE simulations in an efficient manner thus enhancing the capability of commercial simulation software packages. The application of these methods is demonstrated through two example case studies, namely: the prediction of a material's forming limit under hot stamping conditions, and the tool life prediction under multi-cycle loading conditions.

The following paper presents a novel FE simulation technique (KBC-FE), which reduces computational cost by performing simulations on a cloud computing environment, through the application of individual modules. Moreover, it establishes a seamless collaborative network between world leading scientists, enabling the integration of cutting edge knowledge modules into FE simulations.

Basada en el Conocimiento de la simulación de la nube FE de los Procesos de conformado de chapa de metal

The use of Finite Element (FE) simulation software to adequately predict the outcome of sheet metal forming processes is crucial to enhancing the ...

Wicking Tests for Unidirectional Fabrics: Measurements of Capillary Parameters to Evaluate Capillary Pressure in Liquid Composite Molding Processes

During impregnation of a fibrous reinforcement in liquid composite molding (LCM) processes, capillary effects have to be understood in order to identify their influence on void formation in composite parts. Wicking in a fibrous medium described by the Washburn equation was considered equivalent to a flow under the effect of capillary pressure according to the Darcy law. Experimental tests for the characterization of wicking were conducted with both carbon and flax fiber reinforcement. Quasi-unidirectional fabrics were then tested by means of a tensiometer to determine the morphological and wetting parameters along the fiber direction. The procedure was shown to be promising when the morphology of the fabric is unchanged during capillary wicking. In the case of carbon fabrics, the capillary pressure can be calculated. Flax fibers are sensitive to moisture sorption and swell in water. This phenomenon has to be taken into account to assess the wetting parameters. In order to make fibers less sensitive to water sorption, a thermal treatment was carried out on flax reinforcements. This treatment enhances fiber morphological stability and prevents swelling in water. It was shown that treated fabrics have a linear wicking trend similar to those found in carbon fabrics, allowing for the determination of capillary pressure.

An experimental method to measure geometrical parameters and the apparent advancing contact angles describing capillary wicking in unidirectional synthetic and natural fabrics is proposed. These parameters are mandatory for the determination of the capillary pressures that must be taken into account for liquid composite molding (LCM) applications.

Las pruebas de mecha para unidireccionales Tejidos: Las mediciones de parámetros para evaluar capilar capilar de presión en los procesos de líquido compuesto de moldeo

During impregnation of a fibrous reinforcement in liquid composite molding (LCM) processes, capillary effects have to be understood in order to identify ...

Characterization of Ultra-fine Grained and Nanocrystalline Materials Using Transmission Kikuchi Diffraction

One of the challenges in microstructure analysis nowadays resides in the reliable and accurate characterization of ultra-fine grained (UFG) and nanocrystalline materials. The traditional techniques associated with scanning electron microscopy (SEM), such as electron backscatter diffraction (EBSD), do not possess the required spatial resolution due to the large interaction volume between the electrons from the beam and the atoms of the material. Transmission electron microscopy (TEM) has the required spatial resolution. However, due to a lack of automation in the analysis system, the rate of data acquisition is slow which limits the area of the specimen that can be characterized. This paper presents a new characterization technique, Transmission Kikuchi Diffraction (TKD), which enables the analysis of the microstructure of UFG and nanocrystalline materials using an SEM equipped with a standard EBSD system. The spatial resolution of this technique can reach 2 nm. This technique can be applied to a large range of materials that would be difficult to analyze using traditional EBSD. After presenting the experimental set up and describing the different steps necessary to realize a TKD analysis, examples of its use on metal alloys and minerals are shown to illustrate the resolution of the technique and its flexibility in term of material to be characterized.

This paper provides a detailed method to characterize the microstructure of ultra-fine grained and nanocrystalline materials using a scanning electron microscope equipped with a standard electron backscatter diffraction system. Metal alloys and minerals presenting refined microstructures are analyzed using this technique, showing the diversity of its possible applications.

Caracterización de ultra-grano fino y nanocristalinos materiales que utilizan la transmisión Kikuchi Difracción

One of the challenges in microstructure analysis nowadays resides in the reliable and accurate characterization of ultra-fine grained (UFG) and ...

Processing of Bulk Nanocrystalline Metals at the US Army Research Laboratory

Given their potential for significant property improvements relative to their large grained counterparts, much work has been devoted to the continued development of nanocrystalline metals. Despite these efforts, the transition of these materials from the lab bench to actual applications has been blocked by the inability to produce large scale parts that retain the desired nanocrystalline microstructures. Following the development of a method proven to stabilize the nanosized grain structure to temperatures approaching that of the melting point for the given metal, the US Army Research Laboratory (ARL) has progressed to the next stage in the development of these materials - namely the production of large scale parts suitable for testing and evaluation in a range of relevant test environments. This report provides a broad overview of the ongoing efforts in the processing, characterization, and consolidation of these materials at ARL. In particular, focus is placed on the methodology used for producing the nanocrystalline metal powders, in both small and large-scale amounts, that are at the center of ongoing research efforts.

This paper provides a brief overview of the ongoing efforts at the Army Research Laboratory on the processing of bulk nanocrystalline metals with an emphasis on the methodologies used for the production of the novel metal powders.

Tratamiento de metales nanocristalinos de bulto en el laboratorio de investigación del ejército de Estados Unidos

Given their potential for significant property improvements relative to their large grained counterparts, much work has been devoted to the continued ...

Methods of Ex Situ and In Situ Investigations of Structural Transformations: The Case of Crystallization of Metallic Glasses

We demonstrate the use of two nuclear-based analytical methods that can follow the modifications of microstructural arrangement of iron-based metallic glasses (MGs). Despite their amorphous nature, the identification of hyperfine interactions unveils faint structural modifications. For this purpose, we have employed two techniques that utilize nuclear resonance among nuclear levels of a stable 57Fe isotope, namely M&#246;ssbauer spectrometry and nuclear forward scattering (NFS) of synchrotron radiation. The effects of heat treatment upon (Fe2.85Co1)77Mo8Cu1B14 MG are discussed using the results of ex situ and in situ experiments, respectively. As both methods are sensitive to hyperfine interactions, information on structural arrangement as well as on magnetic microstructure is readily available. M&#246;ssbauer spectrometry performed ex situ describes how the structural arrangement and magnetic microstructure appears at room temperature after the annealing under certain conditions (temperature, time), and thus this technique inspects steady states. On the other hand, NFS data are recorded in situ during dynamically changing temperature and NFS examines transient states. The use of both techniques provides complementary information. In general, they can be applied to any suitable system in which it is important to know its steady state but also transient states.

Methods of Ex Situ and In Situ Investigations of Structural Transformations: The Case of Crystallization of Metallic Glasses

Here, we present a protocol to describe ex situ and in situ investigations of structural transformations in metallic glasses. We employed nuclear-based analytical methods which inspect hyperfine interactions. We demonstrate the applicability of M&#246;ssbauer spectrometry and nuclear forward scattering of synchrotron radiation during temperature-driven experiments.

Métodos Ex Situ e In Situ las investigaciones de las transformaciones estructurales: el caso de la cristalización de vidrios metálicos

We demonstrate the use of two nuclear-based analytical methods that can follow the modifications of microstructural arrangement of iron-based metallic ...