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.

A técnica de simulação KBC-FE permite simulações avançadas a ser realizado fora do local usando os módulos dedicados. Ele pode ser executado módulos funcionais em um ambiente de nuvem, que apontam-se os nós de diferentes especializações, para garantir que as simulações de processos são conduzidos com a maior precisão possível. Os aspectos críticos na simulação KBC-FE pode envolver a independência dos códigos FE, a eficiência da computação, ea precisão dos módulos funcionais. A realização de cada função avançada em um módulo seria contar com o desenvolvimento de um novo modelo e / ou uma nova técnica experimental. Por exemplo, o módulo de limite de conformação é desenvolvido com base no novo modelo de previsão de limite de conformação unificado 11, eo módulo de previsão de vida útil da ferramenta atrito atualmente tem sido desenvolvido pela implementação do modelo de atrito interativa 20. A técnica de simulação KBC-FE também oferece a função de cálculo selectiva, isto é, apenas os elementos cumprindo a selecçãocritérios são selecionados para uma avaliação mais aprofundada nos módulos individuais. Por exemplo, o módulo de previsão de vida da ferramenta selecciona automaticamente os elementos para os quais o revestimento duro tende a desagregação, pela classificação da taxa de desgaste de todos os elementos na primeira formando ciclo, assim, normalmente menos de 1% dos elementos serão seleccionados para posterior avaliações de vida útil da ferramenta sob condições de carga multi-ciclo. Na presente pesquisa, a previsão de vida útil da ferramenta depois de 300 ciclos de formação pode ser concluído dentro de 5 min. Ao realizar os testes pertinentes e calibração em conformidade, o modelo de formação de limite poderia ser aplicada para a formação de simulações de processos para determinar consequentemente, os parâmetros ideais para a produção de um componente a partir de tais ligas com sucesso, e sem ocorrência de estiramento. O modelo de previsão limite de conformação foi desenvolvido como um módulo de nuvem que era independente do software FE ser utilizado, e pode ser aplicado a qualquer software FE para avaliar a formabilidade de um material duranteformando, sem sub-rotinas complicadas 17. Ao importar os dados relevantes para o modelo, os cálculos podem ser realizados para determinar se a falha poderia ocorrer, em regiões do componente que o usuário pode especificar, economizando recursos computacionais. No entanto, deve notar-se que, como as curvas de tensão-deformação são inseridos no software FE por meio de uma simples tabela de consulta, que podem ser difíceis de representar totalmente as propriedades do material a várias temperaturas e taxas de deformação durante a simulação. No módulo de previsão de vida útil da ferramenta, o comportamento de atrito durante a formação pode ser previsto através da importação dos dados do histórico de deformação necessários para o módulo de atrito verificados 20, e em seguida, importando os pontos de dados discretos calculados pelo módulo de nuvem para cada elemento de volta para o software FE. Isso garante que o módulo de atrito avançado pode ser utilizado por todos os códigos de FE, independentemente da sua capacidade para incorporar utilizadores-sub-rotinas. Além disso, a modificaçãoule poderia ser executado em paralelo para reduzir ainda mais o tempo de computação. O modelo de atrito / desgaste interativo assumiu a ausência de partículas de desgaste durante a inicial de correr, e, como resultado, seria razoável esperar um valor inicial constante de coeficiente de atrito de 0,17 20. Embora este modelo revelou a evolução da distribuição de atrito, o comportamento de atrito durante um processo de formação é muito complicado e é difícil de integrar completamente o comportamento de atrito complexo a partir do módulo de nuvem para a simulação FE. Enquanto tecnologia do futuro, a simulação KBC-FE contará com o desenvolvimento de pacotes de software de simulação FE baseados na Internet dedicado e robusto, o que exigiria um modelo de negócio altamente rentável, mas completamente diferente a ser estabelecida pelos desenvolvedores de software. Além disso, uma rede interna dedicada precisa ser construída dentro dos partidos de colaboração para garantir a segurança dos dados ea confiabilidade do sistema de controle 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.

Simulação KBC-FE para Estiramento Prediction Em um processo de estampagem a quente, o uso de um espaço em branco otimizado-forma não só irá poupar custos de material, mas também ajudar a reduzir a presença de defeitos, tais como carícias, rachaduras e enrugamento. A forma em branco inicial afecta significativamente o fluxo de material durante a formação e, portanto, um desenho sensível da forma em branco é crítico para o sucesso do processo de estampagem a quente e a qualidade dos produtos finais. Para reduzir os esforços de experiências de tentativa e erro para determinar a geometria em branco ideal, simulação KBC-FE foi provado ser um método altamente eficiente e eficaz para minimizar as áreas com carícias. Usando esta técnica, cada simulação demora cerca de 2 horas, enquanto o paralelo computação módulo de nuvem para carícias previsão é concluída dentro de 4 horas. A Figura 4 mostra a evolução da forma em branco usado na estampagem a quente, um exemplo de componente interno da porta automóvel. A forma em branco inicial, adotada a partir de um processo de estampagem a frio convencional, foi utilizado pela primeira vez na simulação KBC-FE. Os resultados experimentais na Figura 4 (a) mostram que a grande falha (rachaduras ou estiramento) áreas são visíveis após a estampagem a quente. Depois de uma iteração da optimização forma em branco, que pode ser visto na Figura 4 (b), que um painel de quase totalmente bem sucedida é formado com muito menos estiramento, comparado com a utilização da forma inicial em branco. Pode ver-se que existe ainda uma indicação de estiramento nos bolsos na parte superior direita e cantos esquerdo do painel. Após optimização adicional na Figura 4 (c), a forma optimizada em branco foi finalmente obtido sem estreitamento visível no painel. A forma em branco otimizado determinada pela simulação KBC-FE foi verificado experimentalmente através de estampagem a quenteEnsaios realizados sobre uma linha de produção totalmente automatizada oferecido por um fabricante do sistema de produção. Simulação KBC-FE de Previsão de Vida Ferramenta FE simulações convencionais de processos de formação de metal são realizados por um único ciclo. No entanto, num ambiente de produção, ciclos múltiplos de formação são executadas sobre uma dada ferramenta, onde se verificar que um aumento no número de ciclos que formam resulta num aumento da diferença entre os componentes formados. Esta variação durante o carregamento ferramenta multi-ciclo é o resultado de mudar a topografia da superfície. Por exemplo, o carregamento de múltiplos ciclos de formação de ferramentas com revestimentos funcionais irá levar a uma redução de espessura de revestimento devido ao desgaste. Além disso, a desagregação do revestimento, também irá ser influenciada por formação de parâmetros, tais como a carga / pressão, formando velocidades, etc A técnica KBC-FE permite osimulação de folha de metal formando processos sob condições de carga multi-ciclo, o que é essencial para a previsão da vida em serviço de formação de ferramentas com revestimentos funcionais avançados. Para investigar os efeitos da força de retenção em branco na vida útil da ferramenta, em branco valores força de retenção de 5, 20 e 50 kN foram examinados para uma velocidade de formação constante de 250 mm / s. A Figura 5 mostra a distribuição da espessura do revestimento da ferramenta restante com diferentes forças de retenção em branco depois de 300 ciclos de formação. Isto indica claramente que a espessura do revestimento restante diminui com um aumento da força de retenção em branco. A Figura 6 mostra a distribuição da espessura de revestimento e a pressão remanescente com as forças de retenção em branco de 5, 20 e 50 kN, respectivamente, ao longo da distância curvilínea do molde após 300 ciclos de formação. Como a região AB representa o ent dierance região durante o processo de dobragem em forma de U, a pressão e a distância em relação ao desgaste nesta região eram muito maiores do que outras regiões da matriz. Por conseguinte, o desgaste do revestimento ocorreu principalmente nesta área. Existem dois valores de pico de redução da espessura de revestimento a 20 kN e 50 kN, que correspondem aos dois picos, sob a pressão. Enquanto isso, a espessura do revestimento restante diminui com o aumento da força de retenção em branco. Os menores espessuras de revestimento restante com as forças de exploração em branco de 5, 20 e 50 kN, foram 0,905, 0,570 e 0,403 microns, respectivamente, em que a espessura do revestimento inicial foi de 2,1 microns. <img alt="figura 1" src="/files/ftp_upload/53957/53957fig1.jpg" /> Figura 1: Comparação entre as estirpes experimentais e previstos, formando-limite em diferentes temperaturas. As estirpes limite de conformação aumentar à medida que a temperatura sobe, a uma velocidade constante de 250 mm/ s, ou equivalentemente, a taxa de deformação de 6,26 s-1. <a href="https://www.jove.com/files/ftp_upload/53957/53957fig1large.jpg" target="_blank">Por favor clique aqui para ver uma versão maior desta figura.</a> <img alt="Figura 2" src="/files/ftp_upload/53957/53957fig2.jpg" /> Figura 2: Gráfico esquemático para o conhecimento baseado em nuvem FE simulação de um processo de chapa. software comercial de simulação FE, é usado para executar a simulação e exportar os resultados necessários para os módulos individuais. Os módulos, por exemplo, maleabilidade, transferência de calor, força pós-formação (microestrutura), previsão de vida útil da ferramenta, da ferramenta de projeto, etc., trabalham simultaneamente e independentemente na nuvem, portanto, permitindo a integração de conhecimentos de ponta de várias fontes em simulações FE . <a href="https://www.jove.com/files/ftp_upload/53957/53957fig2large.jpg" target="_blank">Por favor cl</a>ick aqui para ver uma versão maior desta figura. <img alt="Figura 3" src="/files/ftp_upload/53957/53957fig3.jpg" /> Figura 3: Geometria da peça de trabalho e ferramentas para a forma de U flexão simulação. As ferramentas, ou seja, soco, titular em branco e morrem, são modelados usando elementos rígidos. elementos de casca são usadas para elementos da peça de trabalho (em branco). <a href="https://www.jove.com/files/ftp_upload/53957/53957fig3large.jpg" target="_blank">Por favor clique aqui para ver uma versão maior desta figura.</a> <img alt="Figura 4" src="/files/ftp_upload/53957/53957fig4.jpg" /> Figura 4: Evolução da forma em branco para estampagem a quente de uma porta de painel interno (exibido na simulação FE). Esquerda: Os números em molduras verdes representam formas em branco em cada fase de otimização, e os de vermelhoquadros de correspondência com a forma em branco antes da sua optimização. Direita: estiramento resultados de previsão em cada fase de otimização. (A) Os resultados iniciais com grande fracasso (craqueamento / estiramento mostrado na cor vermelha), (b) Redução do fracasso com algum estiramento após a primeira etapa de otimização, (c) forma em branco otimizado final sem estiramento visível. <a href="https://www.jove.com/files/ftp_upload/53957/53957fig4large.jpg" target="_blank">Por favor clique aqui para ver uma versão maior desta figura.</a> <img alt="Figura 5" src="/files/ftp_upload/53957/53957fig5.jpg" /> Figura 5: A distribuição da espessura do revestimento restante (exibido na simulação FE) com forças que prende o de: (a) 5 kN, (b) de 20 kN, e (c) 50 kN, após 300 ciclos que formam a uma velocidade de estampagem constante de 250 mm / s. <a href="https://www.jove.com/files/ftp_upload/53957/53957fig5large.jpg" target="_blank">Por favor</a>clique aqui para ver uma versão maior desta figura. <img alt="Figura 6" src="/files/ftp_upload/53957/53957fig6.jpg" /> Figura 6: Previsão da pressão de contacto e a espessura do revestimento restante com as forças de retenção em branco de: (a) 5 kN, (b) de 20 kN, e (c) 50 kN, ao longo da distância curvilínea da fieira a uma velocidade de estampagem constante de 250 mm / s. <a href="https://www.jove.com/files/ftp_upload/53957/53957fig6large.jpg" target="_blank">Por favor clique aqui para ver uma versão maior desta 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.

Conhecimento Baseado Simulação Nuvem FE dos Processos de formação de folha 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 ...

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12.0K visualizações.  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.

Vídeo: 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.

Fabricação de simulação, e Caracterização de THz Absorvedores de metamateriais

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

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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.

Simulação do Planetary Interior Diferenciação processos laboratoriais

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 Microfluidic Drops sem metal Eletrodos

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.

Seletiva Área Modificação de Superfície Wettability Silicon por Pulsed Laser irradiação UV em meio 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.

Visualizando Hyporheic Fluxo Através bedforms Usando Experimentos corante e Simulação

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 experimentais para processos de resfriamento Elastocaloric Investigação de Memória de Forma baseada e Validação de 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.

Simulação de vibrações induzidas por humanos com base no comportamento do pedestre no campo Caracterizada

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.

Estudar processos dinâmicos de Nano porte Objects no líquido utilizando a Transmissão Microscopia Eletrônica de Varredura

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.

Estudo do experimento de quebra de sifão e simulação para um Reactor de investigação

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.