The financial support from Innovate UK, Ultra-light Car Bodies (UlCab, reference 101568) and Make it lighter, with less (LightBlank, reference 131818) are gratefully acknowledged. The research leading to these results has received funding from the European Union's Seventh Framework Program (FP7/2007-2013) under grant agreement No. 604240, project title 'An industrial system enabling the use of a patented, lab-proven materials processing technology for Low Cost forming of Lightweight structures for transportation industries (LoCoLite)'. Significant support was also received from the AVIC Centre for Structural Design and Manufacture at Imperial College London, which is funded by Aviation Industry Corporation of China (AVIC).

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The authors have nothing to disclose.

La técnica de simulación KBC-FE permite simulaciones avanzadas para llevar a cabo fuera de las instalaciones a través de módulos dedicados. Se puede ejecutar módulos funcionales en un entorno de nube, que enlazan los nodos de diferentes especialidades, para asegurar que las simulaciones de procesos se llevan a cabo con la mayor precisión posible. Los aspectos críticos en la simulación KBC-FE pueden implicar la independencia de los códigos FE, la eficiencia de la computación, y la precisión de los módulos funcionales. La realización de cada función avanzada en un módulo se basaría en el desarrollo de un nuevo modelo y / o una nueva técnica experimental. Por ejemplo, el módulo de límite de conformación está desarrollado en base a la nueva modelo de predicción límite que forma unificada 11, y el módulo de predicción de vida de la herramienta de fricción actualmente ha sido desarrollado por la aplicación del modelo de fricción 20 interactiva. La técnica de simulación KBC-FE también ofrece la función de cálculo diferencial, es decir, sólo los elementos cumplimiento de la seleccióncriterios se seleccionan para su posterior evaluación en los módulos individuales. Por ejemplo, el módulo de herramienta de predicción de la vida selecciona automáticamente los elementos para los que el revestimiento duro tiende a la descomposición, por la clasificación de la velocidad de desgaste de todos los elementos de la primera ciclo de formación, por lo general menos de 1% de los elementos será seleccionado para su posterior evaluaciones vida de la herramienta bajo condiciones de carga con ciclos múltiples. En la presente investigación, la predicción de vida de la herramienta después de 300 ciclos de formación puede ser completado dentro de los 5 min. Al llevar a cabo las pruebas pertinentes y calibrar en consecuencia, el modelo de formación de límite podría aplicarse a la formación de simulaciones de proceso para determinar, en consecuencia los parámetros óptimos para la producción de un componente a partir de tales aleaciones con éxito, y sin incidencias de formación de cuello. El modelo de predicción límite de formación fue desarrollado como un módulo de nube que era independiente del software FE se está utilizando, y se podría aplicar a cualquier software FE para evaluar la capacidad de conformado de un material duranteformando, sin subrutinas complicados 17. Mediante la importación de los datos relevantes en el modelo, los cálculos podrían llevarse a cabo para determinar si se produciría el fracaso, en las regiones del componente que el usuario pueda especificar, el ahorro en recursos computacionales. Sin embargo, hay que señalar que a medida que las curvas de esfuerzo-deformación se introducen en el software FE través de una sencilla tabla de consulta, puede ser difícil de representar completamente de las propiedades del material a diferentes temperaturas y velocidades de deformación durante la simulación. En el módulo de predicción de la vida de la herramienta, el comportamiento de rozamiento durante la formación se puede predecir mediante la importación de los datos de la historia de deformación necesarios en el módulo de fricción verificada 20, y luego importar los puntos de datos discretos calculados por el módulo de nube para cada elemento de nuevo en el software FE. Esto asegura que el módulo de fricción avanzado puede ser utilizado por todos los códigos de FE, independientemente de su capacidad de incorporar user-subrutinas. Además, el Ministerio de DefensaULE se puede correr en paralelo para reducir aún más el tiempo de cálculo. El modelo de fricción / desgaste interactiva supone la ausencia de partículas de desgaste durante el deslizamiento inicial, y como resultado, sería razonable esperar que un valor inicial constante de coeficiente de fricción 0,17 20. Aunque este modelo reveló la evolución de la distribución de fricción, el comportamiento de fricción durante un proceso de formación es muy complicado, y es difícil de integrar completamente el comportamiento de fricción complejo desde el módulo de la nube en la simulación FE. Como una tecnología futura, la simulación KBC-FE se basará en el desarrollo de paquetes de software de simulación basado FE dedicado y robusta de Internet, lo que requeriría un modelo de negocio muy rentable, pero completamente diferente que será establecido por los desarrolladores de software. Además, una red interna específica debe ser construido dentro de los partidos de colaboración para garantizar la seguridad de los datos y la fiabilidad del sistema de control industrial. </p&gt;

Finite Element (FE) simulations have become a powerful tool for optimizing process parameters in the metal forming industry. The reliability of FE simulation results is dependent on the accuracy of the material definition, input in the form of flow stress data or constitutive equations, and the assignment of the boundary conditions, such as the friction coefficient and the heat transfer coefficient. In the past few years, advanced FE simulations have been developed via the implementation of user-defined subroutines, which have significantly broadened the capability of FE software.
The use of such advanced FE simulations in the design of forming processes for structural components has been investigated by both the aviation and automotive industries, with the intention of producing lightweight structures that reduces operating costs and CO2 emissions. Particular focus has been placed on the replacement of steel components with lower density materials, such as aluminum alloys and magnesium alloys. However, these alloys, especially the stronger variants, offer limited formability at room temperature and thus complex-shaped components cannot be manufactured using the conventional cold stamping process. Therefore, advanced high temperature forming technologies, such as warm aluminum forming 1-4, hot stamping of aluminum alloys 5-9 and hot stamping of high strength steels 10, have been developed over the past decades to enable complex-shaped components to be formed. In general, high temperature forming processes involve significant temperature variations, strain rate and loading path changes 11, which would, for instance, cause inevitable viscoplastic and loading history dependent responses from the work piece materials. These are intrinsic features of high temperature forming processes and may be difficult to represent using conventional FE simulation techniques. Another desirable feature would be the ability to predict the tool life over multiple forming cycles in such processes, since they require low friction characteristics achieved through coatings that degrade with each forming operation. To represent all these features via the implementation of user-defined subroutines would be computationally very expensive. Moreover, the development and implementation of multiple subroutines would require excessive multi-disciplinary knowledge from an engineer conducting the simulations.
In the present work, a novel Knowledge Based Cloud FE (KBC-FE) simulation technique is proposed, based on the application of modules on a cloud computing environment, that enables an efficient and effective method of modeling advanced forming features in conjunction with conventional FE simulations. In this technique, data from the FE software is processed at each cloud module, and then imported back into the FE software in the relevant consistent format, for further processing and analysis. The development of these modules and their implementation in the KBC-FE is detailed.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>AA6082-T6</td>
			<td>AMAG</td>
			<td></td>
			<td>Material</td>
		</tr>
		<tr>
			<td>AA5754-H111</td>
			<td>AMAG</td>
			<td></td>
			<td>Material</td>
		</tr>
		<tr>
			<td>&#160;1000 kN high-speed press</td>
			<td>ESH</td>
			<td></td>
			<td>Forming press</td>
		</tr>
		<tr>
			<td>ARGUS</td>
			<td>GOM</td>
			<td></td>
			<td>Optical forming analysis</td>
		</tr>
		<tr>
			<td>PAM-STAMP 2015</td>
			<td>ESI</td>
			<td></td>
			<td>FE simulation software</td>
		</tr>
		<tr>
			<td>Matlab&#160;</td>
			<td>MathWorks</td>
			<td></td>
			<td>Numerical calculation software</td>
		</tr>
		<tr>
			<td>Gleeble 3800</td>
			<td>DSI</td>
			<td></td>
			<td>Uniaxial tensile test</td>
		</tr>
		<tr>
			<td>High Temperature Tribometer (THT)</td>
			<td>Anton Paar</td>
			<td></td>
			<td>Friction property test</td>
		</tr>
		<tr>
			<td>NewViewTM 7100</td>
			<td>ZYGO</td>
			<td></td>
			<td>Surface profilometer</td>
		</tr>
		<tr>
			<td>&#160;Magnetron sputtering equipment</td>
			<td></td>
			<td></td>
			<td>Coating deposition</td>
		</tr>
		<tr>
			<td>Microhardness tester</td>
			<td>Wolpert Wilson Instruments</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Nano-hardness indenter&#160;</td>
			<td>MTS</td>
			<td></td>
			<td></td>
		</tr>
	</tbody>
</table>

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.

Simulación KBC-FE para la Predicción Collarino En un proceso de estampación en caliente, el uso de un blanco de forma optimizada no sólo ahorrará el coste del material, sino también ayudar a reducir la presencia de defectos, tales como la formación de cuellos, grietas y arrugas. La forma en blanco inicial afecta el flujo de material de manera significativa durante la formación, y por lo tanto un diseño razonable de la forma en blanco es crucial para el éxito del proceso de estampación en caliente y la calidad de los productos finales. Para reducir los esfuerzos de los experimentos de prueba y error para determinar la geometría óptima en blanco, simulación KBC-FE fue demostrado ser un método altamente eficiente y eficaz para reducir al mínimo las zonas de estrechamiento. Usando esta técnica, cada simulación dura aproximadamente 2 horas, mientras que el cálculo módulo nube paralelo para la predicción de formación de cuello se completa dentro de 4 horas. La figura 4 muestra la evolución de la forma de fogueo para la estampación en caliente, un ejemplo de puerta de automóvil componente interno. La forma en blanco inicial, adoptado de un proceso de estampación en frío convencional, se utilizó por primera vez en la simulación KBC-FE. Los resultados experimentales en la Figura 4 (a) muestran que gran fracaso (como grietas o estrechamiento) áreas son visibles después de la estampación en caliente. Después de una iteración de la optimización de la forma en blanco, se puede ver en la Figura 4 (b) que un panel casi totalmente exitosa se forma con mucho menos de formación de cuello, en comparación con el uso de la forma en blanco inicial. Se puede ver que todavía hay una indicación de formación de cuello en los bolsillos en la parte superior derecha y las esquinas izquierda del panel. Después de una optimización adicional en la Figura 4 (c), la forma en blanco optimizado se obtiene finalmente sin estricción visible en el panel. La forma en blanco optimizado determinada por la simulación KBC-FE se verificó experimentalmente a través de estampación en calienteLos ensayos realizados en una línea de producción totalmente automatizada ofrecido por un fabricante de sistemas de producción. Simulación KBC-FE para la Predicción vida de la herramienta Convencionales simulaciones FE de los procesos de formación de metal se realizan para un solo ciclo. Sin embargo, en un entorno de producción, múltiples ciclos de formación se realizan en una herramienta dada, donde se encuentra que un aumento en el número de ciclos que forman resulta en un aumento de la variación entre los componentes formados. Esta variación durante herramienta de carga multi-ciclo es el resultado del cambio de topografía de la superficie. Por ejemplo, la carga de múltiples ciclos de formación de herramientas con recubrimientos funcionales dará lugar a una reducción del espesor del revestimiento debido al desgaste. Por otra parte, la descomposición del recubrimiento también se verá influenciada por la formación de parámetros, tales como la carga / presión, formando velocidades, etc. La técnica KBC-FE permite lasimulación de chapa procesos bajo condiciones de carga multi-ciclo de conformación, que es esencial para la predicción de la vida en servicio de formación de herramientas con recubrimientos funcionales avanzados. Para investigar los efectos de la fuerza de retención en blanco en la vida de la herramienta, los valores de fuerza de retención en blanco de 5, 20 y 50 kN fueron examinados para una velocidad de formación constante de 250 mm / s. La Figura 5 muestra la distribución de espesor de revestimiento herramienta restante con diferentes fuerzas de retención en blanco después de 300 ciclos de conformado. Se indica claramente que el espesor del recubrimiento restante disminuye con un aumento en la fuerza de sujeción en blanco. La Figura 6 muestra la distribución del espesor de la presión y el revestimiento restante con fuerzas de retención en blanco de 5, 20, y 50 kN, respectivamente, a lo largo de la distancia curvilínea de la matriz después de 300 ciclos de conformado. Dado que la región AB representa la matriz entregión Rance durante el proceso de plegado en forma de U, la presión y la distancia desgaste relativo en esta región eran mucho más alta que otras regiones de la matriz. En consecuencia, el desgaste del recubrimiento se produjo principalmente en esta área. Hay dos valores pico de reducción de espesor de revestimiento a 20 kN y 50 kN que corresponden a los dos picos en virtud de la presión. Mientras tanto, el espesor del recubrimiento restante disminuye con el aumento de la fuerza de sujeción en blanco. Los espesores de recubrimiento restante más bajos con fuerzas de retención en blanco de 5, 20, y 50 kN, fueron 0,905, 0,570, y 0,403 micras, respectivamente, donde el espesor del revestimiento inicial fue de 2,1 micras. <img alt="Figura 1" src="/files/ftp_upload/53957/53957fig1.jpg" /> Figura 1: Comparación entre las cepas límite experimentales y predijo que forman a diferentes temperaturas. Las cepas de límite forman aumentan a medida que aumenta la temperatura, a una velocidad constante de 250 mm/ s, o equivalentemente, una velocidad de deformación de 6,26 s-1. <a href="https://www.jove.com/files/ftp_upload/53957/53957fig1large.jpg" target="_blank">Haga clic aquí para ver una versión más grande de esta figura.</a> <img alt="Figura 2" src="/files/ftp_upload/53957/53957fig2.jpg" /> Figura 2: diagrama esquemático de la nube basada en el conocimiento FE simulación de un proceso de conformado de chapa metálica. FE software de simulación comercial, se utiliza para ejecutar la simulación y exportar los resultados requeridos para los módulos individuales. Los módulos, por ejemplo, la capacidad de conformado, transferencia de calor, la fuerza de formación de post (microestructura), predicción de vida de la herramienta, herramienta de diseño, etc., funcionan simultáneamente y de forma independiente en la nube, por lo tanto, permite la integración de los conocimientos de vanguardia a partir de múltiples fuentes en simulaciones FE . <a href="https://www.jove.com/files/ftp_upload/53957/53957fig2large.jpg" target="_blank">Por favor, cl</a>ick aquí para ver una versión más grande de esta figura. <img alt="figura 3" src="/files/ftp_upload/53957/53957fig3.jpg" /> Figura 3: La geometría de la pieza de trabajo y herramientas para la forma en U de simulación de doblado. Las herramientas, es decir, ponche, pisador y mueren, se modelan mediante elementos rígidos. elementos de vaciado se utilizan para la pieza de trabajo elementos (en blanco). <a href="https://www.jove.com/files/ftp_upload/53957/53957fig3large.jpg" target="_blank">Haga clic aquí para ver una versión más grande de esta figura.</a> <img alt="Figura 4" src="/files/ftp_upload/53957/53957fig4.jpg" /> Figura 4: Evolución de la forma en blanco para estampación en caliente de un panel interior de la puerta (que se muestra en la simulación FE). Izquierda: Las cifras contenidas en los marcos verdes representan formas en blanco en cada etapa de optimización, y los que están en rojomarcos corresponden a la forma en blanco antes de su optimización. Derecha: collarino predicción de resultados en cada etapa de optimización. (A) Los resultados iniciales con un gran fracaso (craqueo / estricción mostrados en color rojo), (b) la falta de formación de cuello rebajado con un poco después de la primera etapa de optimización, (c) la forma en blanco optimizado final sin formación de cuello visible. <a href="https://www.jove.com/files/ftp_upload/53957/53957fig4large.jpg" target="_blank">Haga clic aquí para ver una versión más grande de esta figura.</a> <img alt="Figura 5" src="/files/ftp_upload/53957/53957fig5.jpg" /> Figura 5: La distribución de espesor de revestimiento restante (que se muestra en la simulación FE) con fuerzas de retención en blanco de: (a) 5 kN, (b) 20 kN, y (c) 50 kN, después de 300 ciclos de formación a una velocidad de estampación constante de 250 mm / s. <a href="https://www.jove.com/files/ftp_upload/53957/53957fig5large.jpg" target="_blank">Por favor</a>clic aquí para ver una versión más grande de esta figura. <img alt="Figura 6" src="/files/ftp_upload/53957/53957fig6.jpg" /> Figura 6: Predicción de la presión de contacto y el espesor de recubrimiento restante con fuerzas de retención en blanco de: (a) 5 kN, (b) 20 kN, y (c) 50 kN, a lo largo de la distancia curvilínea de la matriz a una velocidad de estampación constante de 250 mm / s. <a href="https://www.jove.com/files/ftp_upload/53957/53957fig6large.jpg" target="_blank">Haga clic aquí para ver una versión más grande de esta figura.</a>

Watch this Scientific Journal Video about Knowledge Based Cloud FE Simulation of Sheet Metal Forming Processes at JoVE.com

Knowledge Based Cloud FE Simulation of Sheet Metal Forming Processes

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 ...

knowledge-based-cloud-fe-simulation-of-sheet-metal-forming-processes

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Unit 1

Introduction to Concrete

SCIENTISTS IN ACTION

12.0K vistas.  Imperial College London. 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.

Video: Knowledge Based Cloud FE Simulation of Sheet Metal Forming Processes

Simulation, Fabrication and Characterization of THz Metamaterial Absorbers

Metamaterials (MM), artificial materials engineered to have properties that may not be found in nature, have been widely explored since the first theoretical1 and experimental demonstration2 of their unique properties. MMs can provide a highly controllable electromagnetic response, and to date have been demonstrated in every technologically relevant spectral range including the optical3, near IR4, mid IR5 , THz6 , mm-wave7 , microwave8 and radio9 bands. Applications include perfect lenses10, sensors11, telecommunications12, invisibility cloaks13 and filters14,15. We have recently developed single band16, dual band17 and broadband18 THz metamaterial absorber devices capable of greater than 80% absorption at the resonance peak. The concept of a MM absorber is especially important at THz frequencies where it is difficult to find strong frequency selective THz absorbers19. In our MM absorber the THz radiation is absorbed in a thickness of ~ &lambda;/20, overcoming the thickness limitation of traditional quarter wavelength absorbers. MM absorbers naturally lend themselves to THz detection applications, such as thermal sensors, and if integrated with suitable THz sources (e.g. QCLs), could lead to compact, highly sensitive, low cost, real time THz imaging systems.

This protocol outlines the simulation, fabrication and characterization of THz metamaterial absorbers. Such absorbers, when coupled with an appropriate sensor, have applications in THz imaging and spectroscopy.

Simulación, Fabricación y Caracterización de THz Amortiguadores metamateriales

Metamaterials (MM),  artificial materials engineered to have properties that may not be found in  nature, have been widely explored since the first ...

Investigación

Ingeniería

Simulation of the Planetary Interior Differentiation Processes in the Laboratory

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 that layered structure, (1) percolation of liquid metal in a solid silicate matrix by planet differentiation, and (2) inner core crystallization by subsequent planet cooling. We conduct high-pressure and high-temperature experiments to simulate both processes in the laboratory. Formation of percolative planetary core depends on the efficiency of melt percolation, which is controlled by the dihedral (wetting) angle. The percolation simulation includes heating the sample at high pressure to a target temperature at which iron-sulfur alloy is molten while the silicate remains solid, and then determining the true dihedral angle to evaluate the style of liquid migration in a crystalline matrix by 3D visualization. The 3D volume rendering is achieved by slicing the recovered sample with a focused ion beam (FIB) and taking SEM image of each slice with a FIB/SEM crossbeam instrument. The second set of experiments is designed to understand the inner core crystallization and element distribution between the liquid outer core and solid inner core by determining the melting temperature and element partitioning at high pressure. The melting experiments are conducted in the multi-anvil apparatus up to 27 GPa and extended to higher pressure in the diamond-anvil cell with laser-heating. We have developed techniques to recover small heated samples by precision FIB milling and obtain high-resolution images of the laser-heated spot that show melting texture at high pressure. By analyzing the chemical compositions of the coexisting liquid and solid phases, we precisely determine the liquidus curve, providing necessary data to understand the inner core crystallization process.

The high-pressure and high-temperature experiments described here mimic planet interior differentiation processes. The processes are visualized and better understood by high-resolution 3D imaging and quantitative chemical analysis.

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 ...

Picoinjection of Microfluidic Drops Without Metal Electrodes

Existing methods for picoinjecting reagents into microfluidic drops require metal electrodes integrated into the microfluidic chip. The integration of these electrodes adds cumbersome and error-prone steps to the device fabrication process. We have developed a technique that obviates the needs for metal electrodes during picoinjection. Instead, it uses the injection fluid itself as an electrode, since most biological reagents contain dissolved electrolytes and are conductive. By eliminating the electrodes, we reduce device fabrication time and complexity, and make the devices more robust. In addition, with our approach, the injection volume depends on the voltage applied to the picoinjection solution; this allows us to rapidly adjust the volume injected by modulating the applied voltage. We demonstrate that our technique is compatible with reagents incorporating common biological compounds, including buffers, enzymes, and nucleic acids.

We have developed a technique for picoinjecting microfluidic drops that does not require metal electrodes. As such, devices incorporating our technique are simpler to fabricate and to use.

Picoinjection de microfluidos gotas sin electrodos metálicos

Existing methods for picoinjecting reagents into microfluidic drops require metal electrodes integrated into the microfluidic chip. The integration of ...

Selective Area Modification of Silicon Surface Wettability by Pulsed UV Laser Irradiation in Liquid Environment

The wettability of silicon (Si) is one of the important parameters in the technology of surface functionalization of this material and fabrication of biosensing devices. We report on a protocol of using KrF and ArF lasers irradiating Si (001) samples immersed in a liquid environment with low number of pulses and operating at moderately low pulse fluences to induce Si wettability modification. Wafers immersed for up to 4 hr in a 0.01% H2O2/H2O solution did not show measurable change in their initial contact angle (CA) ~75&#176;. However, the 500-pulse KrF and ArF lasers irradiation of such wafers in a microchamber filled with 0.01% H2O2/H2O solution at 250 and 65 mJ/cm2, respectively, has decreased the CA to near 15&#176;, indicating the formation of a superhydrophilic surface. The formation of OH-terminated Si (001), with no measurable change of the wafer&#8217;s surface morphology, has been confirmed by X-ray photoelectron spectroscopy and atomic force microscopy measurements. The selective area irradiated samples were then immersed in a biotin-conjugated fluorescein-stained nanospheres solution for 2 hr, resulting in a successful immobilization of the nanospheres in the non-irradiated area. This illustrates the potential of&#160;the method for selective area biofunctionalization and fabrication of advanced Si-based biosensing architectures. We also describe a similar protocol of irradiation of wafers immersed in methanol (CH3OH) using ArF laser operating at pulse fluence of 65 mJ/cm2 and in situ formation of a strongly hydrophobic surface of Si (001) with the CA of 103&#176;. The XPS results indicate ArF laser induced formation of Si&#8211;(OCH3)x compounds responsible for the observed hydrophobicity. However, no such compounds were found by XPS on the Si surface irradiated by KrF laser in methanol, demonstrating the inability of the KrF laser to photodissociate methanol and create -OCH3 radicals.

We report on a process of in situ alteration of HF treated Si (001) surface into a hydrophilic or hydrophobic state by irradiating samples in microfluidic chambers filled with&#160;H2O2/H2O solution (0.01%-0.5%) or methanol solutions using pulsed UV laser of a relative low pulse fluence.

Área selectivo Modificación de humectabilidad de la superficie del silicio por pulsos láser UV irradiación en Ambiente Líquido

The wettability of silicon (Si) is one of the important parameters in the technology of surface functionalization of this material and fabrication of ...

Visualizing Hyporheic Flow Through Bedforms Using Dye Experiments and Simulation

Advective exchange between the pore space of sediments and the overlying water column, called hyporheic exchange in fluvial environments, drives solute transport in rivers and many important biogeochemical processes. To improve understanding of these processes through visual demonstration, we created a hyporheic flow simulation in the multi-agent computer modeling platform NetLogo. The simulation shows virtual tracer flowing through a streambed covered with two-dimensional bedforms. Sediment, flow, and bedform characteristics are used as input variables for the model. We illustrate how these simulations match experimental observations from laboratory flume experiments based on measured input parameters. Dye is injected into the flume sediments to visualize the porewater flow. For comparison virtual tracer particles are placed at the same locations in the simulation. This coupled simulation and lab experiment has been used successfully in undergraduate and graduate laboratories to directly visualize river-porewater interactions and show how physically-based flow simulations can reproduce environmental phenomena. Students took photographs of the bed through the transparent flume walls and compared them to shapes of the dye at the same times in the simulation. This resulted in very similar trends, which allowed the students to better understand both the flow patterns and the mathematical model. The simulations also allow the user to quickly visualize the impact of each input parameter by running multiple simulations. This process can also be used in research applications to illustrate basic processes, relate interfacial fluxes and porewater transport, and support quantitative process-based modeling.

This manuscript describes how to create regular bedforms in a flume, visualize flow through the bedforms, and use computer simulations to simulate the hyporheic flow. The computer simulations compare well with the experimental observations. This coupled simulation and experiment is well-suited for both research and educational purposes.

Visualización de Flujo hyporheic A través de formas de fondo Utilizando Experimentos Dye y Simulación

Advective exchange between the pore space of sediments and the overlying water column, called hyporheic exchange in fluvial environments, drives solute ...

Experimental Methods for Investigation of Shape Memory Based Elastocaloric Cooling Processes and Model Validation

Shape Memory Alloys (SMA) using elastocaloric cooling processes have the potential to be an environmentally friendly alternative to the conventional vapor compression based cooling process. Nickel-Titanium (Ni-Ti) based alloy systems, especially, show large elastocaloric effects. Furthermore, exhibit large latent heats which is a necessary material property for the development of an efficient solid-state based cooling process. A scientific test rig has been designed to investigate these processes and the elastocaloric effects in SMAs. The realized test rig enables independent control of an SMA&#39;s mechanical loading and unloading cycles, as well as conductive heat transfer between SMA cooling elements and a heat source/sink. The test rig is equipped with a comprehensive monitoring system capable of synchronized measurements of mechanical and thermal parameters. In addition to determining the process-dependent mechanical work, the system also enables measurement of thermal caloric aspects of the elastocaloric cooling effect through use of a high-performance infrared camera. This combination is of particular interest, because it allows illustrations of localization and rate effects &#8212; both important for efficient heat transfer from the medium to be cooled.
The work presented describes an experimental method to identify elastocaloric material properties in different materials and sample geometries. Furthermore, the test rig is used to investigate different cooling process variations. The introduced analysis methods enable a differentiated consideration of material, process and related boundary condition influences on the process efficiency. The comparison of the experimental data with the simulation results (of a thermomechanically coupled finite element model) allows for better understanding of the underlying physics of the elastocaloric effect. In addition, the experimental results, as well as the findings based on the simulation results, are used to improve the material properties.

Experimental methods for investigation of solid state cooling processes and characterization of elastocaloric material properties of Shape Memory Alloys (SMA) are presented. A custom-built test rig has been designed for controlling and comprehensive monitoring of elastocaloric cooling processes. Furthermore, it provides a validation platform for thermomechanically coupled modeling approaches.

Métodos experimentales para procesos de enfriamiento Elastocaloric Investigación de memoria de forma basada y validación del modelo

Shape Memory Alloys (SMA) using elastocaloric cooling processes have the potential to be an environmentally friendly alternative to the conventional vapor ...

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 ...

Studying Dynamic Processes of Nano-sized Objects in Liquid using Scanning Transmission Electron Microscopy

Samples fully embedded in liquid can be studied at a nanoscale spatial resolution with Scanning Transmission Electron Microscopy (STEM) using a microfluidic chamber assembled in the specimen holder for Transmission Electron Microscopy (TEM) and STEM. The microfluidic system consists of two silicon microchips supporting thin Silicon Nitride (SiN) membrane windows. This article describes the basic steps of sample loading and data acquisition. Most important of all is to ensure that the liquid compartment is correctly assembled, thus providing a thin liquid layer and a vacuum seal. This protocol also includes a number of tests necessary to perform during sample loading in order to ensure correct assembly. Once the sample is loaded in the electron microscope, the liquid thickness needs to be measured. Incorrect assembly may result in a too-thick liquid, while a too-thin liquid may indicate the absence of liquid, such as when a bubble is formed. Finally, the protocol explains how images are taken and how dynamic processes can be studied. A sample containing AuNPs is imaged both in pure water and in saline.

This protocol describes the operation of a liquid flow specimen holder for scanning transmission electron microscopy of AuNPs in water, as used for the observation of nanoscale dynamic processes.

El estudio de procesos dinámicos de nano-objetos de tamaño en el líquido de utilizar el escaneado Microscopía Electrónica de Transmisión

Samples fully embedded in liquid can be studied at a nanoscale spatial resolution with Scanning Transmission Electron Microscopy (STEM) using a ...

Study of Siphon Breaker Experiment and Simulation for a Research Reactor

Under the design conditions of a research reactor, the siphon phenomenon induced by pipe rupture can cause continuous outward flow of water. To prevent this outflow, a control device is required. A siphon breaker is a type of safety device that can be utilized to control the loss of coolant water effectively.
To analyze the characteristics of siphon breaking, a real-scale experiment was conducted. From the results of the experiment, it was found that there are several design factors that affect the siphon breaking phenomenon. Therefore, there is a need to develop a theoretical model capable of predicting and analyzing the siphon breaking phenomenon under various design conditions. Using the experimental data, it was possible to formulate a theoretical model that accurately predicts the progress and the result of the siphon breaking phenomenon. The established theoretical model is based on fluid mechanics and incorporates the Chisholm model to analyze two-phase flow. From Bernoulli&#39;s equation, the velocity, quantity, undershooting height, water level, pressure, friction coefficient, and factors related to the two-phase flow could be obtained or calculated. Moreover, to utilize the model established in this study, a siphon breaker analysis and design program was developed. The simulation program operates on the theoretical model basis and returns the result as a graph. The user can confirm the possibility of the siphon breaking by checking the shape of the graph. Furthermore, saving the entire simulation result is possible and it can be used as a resource for analyzing the real siphon breaking system.
In conclusion, the user can confirm the status of the siphon breaking and design the siphon breaker system using the program developed in this study.

The siphon breaking phenomenon was investigated experimentally and a theoretical model was proposed. A simulation program based on the theoretical model was developed and the results of the simulation program were compared with experimental results. It was concluded that the results of the simulation program matched the experimental results well.

Estudio de sifón interruptor experimento y simulación de un Reactor de investigación

Under the design conditions of a research reactor, the siphon phenomenon induced by pipe rupture can cause continuous outward flow of water. To prevent ...

Growth and Electrostatic/chemical Properties of Metal/LaAlO3/SrTiO3 Heterostructures

The quasi 2D electron system (q2DES) that forms at the interface between LaAlO3 (LAO) and SrTiO3 (STO) has attracted much attention from the oxide electronics community. One of its hallmark features is the existence of a critical LAO thickness of 4 unit-cells (uc) for interfacial conductivity to emerge. Although electrostatic mechanisms have been proposed in the past to describe the existence of this critical thickness, the importance of chemical defects has been recently accentuated. Here, we describe the growth of metal/LAO/STO heterostructures in an ultra-high vacuum (UHV) cluster system combining pulsed laser deposition (to grow the LAO), magnetron sputtering (to grow the metal) and X-ray photoelectron spectroscopy (XPS). We study step by step the formation and evolution of the q2DES and the chemical interactions that occur between the metal and the LAO/STO. Additionally, magnetotransport experiments elucidate on the transport and electronic properties of the q2DES. This systematic work not only demonstrates a way to study the electrostatic and chemical interplay between the q2DES and its environment, but also unlocks the possibility to couple multifunctional capping layers with the rich physics observed in two-dimensional electron systems, allowing the fabrication of new types of devices.

Growth and Electrostatic/chemical Properties of Metal/LaAlO3/SrTiO3 Heterostructures

We fabricate metal/LaAlO3/SrTiO3 heterostructures using a combination of pulsed laser deposition and in situ magnetron sputtering. Through magnetotransport and in situ X-ray photoelectron spectroscopy experiments, we investigate the interplay between electrostatic and chemical phenomena of the quasi two-dimensional electron gas formed in this system.