Questo lavoro è stato supportato dalla NASA concessione NNX11AC68G e Carnegie Institution di Washington. Ringrazio Chi Zhang per la sua assistenza con la raccolta dei dati. Ringrazio anche Anat Shahar e Valerie Hillgren per voti recensioni di questo manoscritto.

1. Preparare materiali di partenza e delle Camere di esempio <ol><li> Preparare due tipi di materiali di partenza, (1) una miscela di olivina silicato naturale e polvere di ferro metallico con 10% in peso di zolfo (metallo / rapporti silicato vanno da 4 a 30% in peso) per simulare percolazione di lega di ferro liquido in una matrice di silicato solido durante la formazione del nucleo iniziale di un piccolo corpo planetario, e (2) una miscela omogenea di ferro puro finemente a terra e solfuro di ferro per la determinazione del planetario nucleo di cristallizzazione interno. </li><li> Macinare i materiali di partenza per polvere fine mista sotto etanolo in un mortaio di agata per un&#39;ora ed essiccato a 100 ° C. </li><li> Caricare il materiale di partenza in un MgO sinterizzato o Al 2 O 3 capsula (tipicamente 1,5 mm di diametro e 1,5 di lunghezza), e poi riporla in un gruppo della cella di alta pressione per gli esperimenti multi-incudine. </li><li> Caricare il composto Fe-FeS in una piccola camera del campione (tipicamente 100 micron di diametro e 25 &amp; #181; m di spessore) forato in una guarnizione renio preindented per gli esperimenti laser-riscaldamento nella cella diamante-incudine. Panino la miscela di Fe-FeS tra gli strati di NaCl che fungono da isolanti termici. </li></ol> 2. Gli esperimenti ad alta pressione e ad alte temperature nell&#39;apparato Multi-incudine <ol><li> Il gruppo della cella di alta pressione multi-incudine consiste di un ottaedro MgO come mezzo di pressione, un manicotto ZrO 2 come isolante termico, e un renio cilindrica o riscaldatore grafite. La capsula campione si inserisce all&#39;interno del riscaldatore. Una termocoppia di tipo C viene inserito nella camera del campione per determinare la temperatura del campione. </li><li> Posizionare il gruppo ad alta pressione in un apparecchio ad alta pressione multi-incudine per la pressurizzazione. </li><li> L&#39;apparato multi-incudine è costituito da una pressa idraulica 1.500 ton e un modulo di pressione che contiene un anello di ritenuta con sei cunei di spinta rimovibili formando una cavità cubica al centro 15. Il cubo della cavità houses otto cubi in carburo di tungsteno con angoli troncati. I cubi troncati, che convergono sul gruppo cella ottaedro, vengono separati l&#39;uno dall&#39;altro da guarnizioni comprimibili. Il pistone idraulico trasmette la forza efficace sul gruppo campione da una configurazione a due stadi incudine. Figura 1 illustra la procedura sperimentale per l&#39;esperimento multi-incudine. </li><li> Pressurizzare il campione ad una pressione designata tra 2-27 GPa a temperatura ambiente basato su punto fisso curva di calibrazione di pressione 16, e poi riscaldare a temperature sperimentali fino a 2.300 ° C mediante riscaldamento a resistenza elettrica; mantenere l&#39;esperimento a temperatura costante per tutta la durata dell&#39;esperimento, e disattivare l&#39;alimentazione per spegnere il campione a temperatura ambiente al fine dell&#39;esperimento. </li><li> Rilasciare lentamente la pressione aprendo la valvola dell&#39;olio idraulico e recuperare la carica sperimentale. </li></ol> 3. Esperimenti laser di riscaldamento inDiamond-incudine cellulare <ol><li> Pressione in una cella di diamante incudine è generato tra due incudini di diamante gemma-qualità cristallo singolo (circa 0,25 carati ciascuno). Usiamo una cella di diamante-incudine simmetrica per guidare le incudini opposte perfettamente allineate con un sistema cilindro-pistone. La cella è in grado di generare pressioni corrispondenti alle condizioni di pressione del nucleo della Terra 17. Temperatura elevata viene ottenuta mediante riscaldamento laser nella cella diamante-incudine. Utilizziamo un sistema al Advance Photon Source (APS), che si basa su un laser tecnica biadesivo riscaldamento e consiste di due laser a fibra ottica, per riscaldare il campione da entrambi i lati, e due sistemi spettroradiometriche per misure di temperatura su entrambi i lati 18. Il sistema è progettato per generare una macchia riscaldamento grande (25 micron di diametro), minimizzare le gradienti di temperatura del campione sia radialmente che assialmente nella cella ad incudine di diamante, e massimizzare la stabilità riscaldamento. Figura 2 mostra schematicamentes della configurazione sperimentale per l&#39;esperimento laser-riscaldamento nella cella diamante-incudine con l&#39;immagine del punto laser-riscaldamento. </li><li> Allineare le incudini di diamante con 300 micron culets e preindent una guarnizione renio ad uno spessore di 30 micron da uno spessore iniziale di 250 micron. </li><li> Praticare un foro nella guarnizione preindented con un diametro di 120 micron al centro, e caricare il campione nel foro. </li><li> Pressurizzare il campione ad una pressione designata a temperatura ambiente, e poi riscaldare il campione aumentando la potenza del laser durante le misure di temperatura e in situ raggi X misure di diffrazione presso l&#39;impianto di sincrotrone. </li><li> Spegnere il laser per spegnere il campione quando la fusione parziale viene rilevata da un cambiamento di radiazione termica e dal modello di diffrazione. </li><li> Recuperare il campione riscaldato per la caratterizzazione ex situ. </li></ol> 4. Il recupero del campione e analisi <ol><li> Momentount il campione multi-incudine recuperato in resina epossidica e lucidare la superficie utilizzando una suite di polvere di graniglia diamante da 150 micron a 0,25 micron. </li><li> Carbon-rivestire la superficie del campione e caricarlo nell&#39;apposita camera di uno strumento trave Zeiss Auriga FIB / SEM (Figura 3A) per l&#39;analisi. </li><li> Allineare il campione nel punto coincidente della FIB e SEM a una distanza di lavoro di 5 mm (Figura 3B), e poi premill il campione per esporre un volume di 15 x 20 x 20 micron 3 (Figura 3C). </li><li> Prendere immagini SEM ad un intervallo di 25 nm, usando la fetta e funzione di visualizzazione sullo strumento Zeiss Auriga FIB / SEM (registrare automaticamente una serie di immagini dopo la fresatura fascio ionico con tipica risoluzione di immagine di circa 35 nm). </li><li> Inserire i file di dati immagine ad un software di visualizzazione e ricostruire immagini 3D per visualizzare la distribuzione di fusione e la connettività nel campione spento (Figura 3D). </li></ol>

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Nessun conflitto di interessi dichiarati.

Le tecniche per gli esperimenti multi-incudine sono ben stabiliti, generando pressione stabile e temperatura per un periodo di tempo di funzionamento prolungato e producendo relativamente grande volume di campione. Si tratta di un potente strumento per simulare i processi interni di pianeti, in particolare per gli esperimenti, come fusione di percolazione, che richiedono un certo volume di campione. La limitazione è la pressione massima raggiungibile, fino a 27 GPa con carburo di tungsteno (WC) incudini, raggiungendo l...

Pianeti terrestri, come la Terra, Venere, Marte e Mercurio sono corpi planetari differenziati costituiti da un mantello di silicati e di un nucleo metallico. Il moderno modello di formazione dei pianeti suggerisce che i pianeti terrestri sono formate da collisioni di embrioni planetari Luna-to-Mars-sized cresciute da chilometri di dimensioni o più grande planetesimi attraverso le interazioni gravitazionali 1-2. I planetesimi erano probabilmente già differenziati una volta che le leghe di ferro metalliche raggiunto temperatura di fusione a causa del riscaldamento da fonti come il decadimento radioattivo di isotopi a vita breve come 26 Al 60 Fe, impatto, e il rilascio di energia potenziale 3. È importante capire come il metallo liquido percolato attraverso una matrice di silicato durante la prima differenziazione. Pianeta differenziazione potrebbe procedere attraverso separazione liquido-liquido efficiente o per percolazione di metallo liquido in una matrice di silicato solido, a secondadelle dimensioni e della temperatura all&#39;interno degli organismi planetari. La percolazione di metallo liquido nella matrice di silicato solido è probabile un processo dominante nella differenziazione iniziale quando la temperatura non è sufficientemente elevata per fondere l&#39;intero corpo planetario. L&#39;efficienza di percolazione dipende dall&#39;angolo diedro, determinata dalle energie interfacciali delle interfacce solido-solido e solido-liquido. Possiamo simulare questo processo in laboratorio conducendo esperimenti ad alta pressione e ad alta temperatura su una miscela di lega di ferro e silicati. Recenti studi 4-7 hanno indagato la capacità bagnante di leghe di ferro liquido in una matrice di silicato solido ad alta pressione e temperatura. Hanno usato un metodo convenzionale per misurare la distribuzione di frequenza relativa di angoli diedri apparenti tra il metallo liquido da bonifica grani silicati sulle sezioni lucide per la determinazione del vero angolo diedro. Il metodo convenzionale produce relativamente grande uncertainties dell&#39;angolo diedro misurato e possibili distorsioni seconda delle statistiche di campionamento. Qui presentiamo una nuova tecnica di imaging per visualizzare la distribuzione del metallo liquido nella matrice di silicato in tre dimensioni (3D) mediante combinazione di fresatura FIB ed alta risoluzione emissione di campo dell&#39;imaging SEM. La nuova tecnica di imaging fornisce determinazione precisa dell&#39;angolo diedro e misura quantitativa della frazione volumetrica e la connettività della fase liquida. Il nucleo della Terra si è formata in un tempo relativamente breve (&lt;100.000 mila anni) 8, presumibilmente in uno stato liquido a sua storia antica. Marte e Mercurio hanno anche nuclei liquidi a base di deformazione di marea solare dai dati di rilevamento della radio Mars Global Surveyor 9 e modelli di radar speckle legati alla rotazione planetaria 10, rispettivamente. Modelli di evoluzione termica ed esperimenti di fusione ad alta pressione sulle materie fondamentali sostenere ulteriormente un nucleo marziano liquido11-12. Dati recenti Messenger veicoli spaziali forniscono ulteriori prove per un nucleo liquido di Mercurio 13. Anche la piccola Luna ha probabilmente un piccolo nucleo liquido a base di recente ri-analisi dei sismogrammi APPOLLO lunari 14. Nuclei planetari liquidi sono coerenti con alta energia di accrescimento nella fase iniziale della formazione dei pianeti. Successivo raffreddamento può portare alla formazione di nucleo interno solido per alcuni pianeti. Dati sismici hanno rivelato che la Terra è costituito da un nucleo esterno liquido e un solido interno. La formazione del nucleo interno ha importanti implicazioni per la dinamica del nucleo guidato da convezione termica e composizione e la generazione del campo magnetico del pianeta. Solidificazione del nucleo interno è controllata dalla temperatura di fusione dei materiali di base e l&#39;evoluzione termica del nucleo. Formazione del nucleo di pianeti terrestri condiviso percorsi di accrescimento simili e la composizione chimica dei nuclei è considerato abe dominato dal ferro con circa 10% in peso elementi leggeri quali zolfo (S), silicio (Si), ossigeno (O), carbonio (C) e idrogeno (H) 15. E &#39;essenziale avere conoscenza delle relazioni di fusione nei sistemi pertinenti al nucleo, come Fe-FeS, Fe-C, Fe-FeO, Fe-FEh e alta pressione-Fe FeSiat, al fine di comprendere la composizione i nuclei planetari. In questo studio, dimostreremo esperimenti condotti nel dispositivo multi-incudine e cella di diamante-incudine, simulando le condizioni dei nuclei planetari. Gli esperimenti forniscono informazioni sulla sequenza di cristallizzazione e elemento di partizionamento tra metallo solido e liquido, portando ad una migliore comprensione per le esigenze della cristallizzazione nucleo interno e la distribuzione degli elementi leggeri tra il nucleo interno cristallino e liquido fuori centro. Per estendere i rapporti di fusione a pressioni molto elevate, abbiamo sviluppato nuove tecniche per analizzare i campioni temprati recuperati da laser-riscaldato diamante-aesperimenti sulle cellule nvil. Con precisione FIB fresatura dello spot laser-riscaldamento, determiniamo fusione con criteri trama tempra ripreso con alta risoluzione di SEM e analisi chimica quantitativa con un rivelatore a deriva di silicio al submicron risoluzione spaziale. Qui delineare due serie di esperimenti per simulare la formazione di base planetaria da percolazione di metallica sciogliersi in matrice di silicato durante l&#39;accrescimento precoce e nucleo interno cristallizzazione successivo raffreddamento. La simulazione è volto a comprendere le due importanti processi durante l&#39;evoluzione del nucleo 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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 width:66pt" width="88">Diamond-anvil cell</td>
			<td class="xl63" style="border-top:none;border-left:none;width:66pt" width="88">Geophysical Lab</td>
			<td class="xl63" style="border-top:none;border-left:none;width:66pt" width="88">Home Builder</td>
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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 interno planetario è in condizioni di alta pressione e ad alta temperatura ed ha una struttura a strati. Ci sono due importanti processi che hanno portato a tale struttura stratificata, (1) percolazione di metallo liquido in un solido matrice di silicato dalla differenziazione pianeta, e (2) cristallizzazione nucleo interno dalla successiva pianeta raffreddamento. Noi conduciamo esperimenti ad alta pressione e ad alta temperatura per simulare entrambi i processi in laboratorio. Formazione di percolativo nucleo planetario dipende dall&#39;efficienza di percolazione melt, che è controllata dal diedro (wetting) angolo. La simulazione percolazione comprende riscaldamento del campione ad alta pressione ad una temperatura obiettivo a cui lega di ferro-zolfo è fuso mentre il silicato rimane solido e quindi determinare il vero angolo diedro di valutare lo stile di migrazione liquido in una matrice cristallina da visualizzazione 3D. Il volume rendering 3D si ottiene tagliando il campione recuperato con un raggio di ioni focalizzati (FIB) e tare SEM immagine di ogni fetta con uno strumento trave FIB / SEM. La seconda serie di esperimenti è progettata per comprendere il nucleo di cristallizzazione e elemento distribuzione interna tra il nucleo esterno liquido e solido interno determinando la temperatura di fusione e elemento di partizionamento ad alta pressione. Gli esperimenti sono condotti in fusione dell&#39;apparato multi-incudine fino a 27 GPa ed estese a più alta pressione nella cella diamante-incudine con laser-riscaldamento. Abbiamo sviluppato tecniche per recuperare i piccoli campioni riscaldati con specificità FIB fresatura e ottenere immagini ad alta risoluzione dello spot laser-riscaldata che mostrano fusione struttura ad alta pressione. Analizzando la composizione chimica del liquido coesistenti e fasi solide, abbiamo appunto determinare la curva di liquidus, fornendo i dati necessari per comprendere il processo di cristallizzazione nucleo interno.

Abbiamo condotto una serie di esperimenti usando miscele di San Carlos olivina e lega metallica Fe-FeS con diversi rapporti metallo-silicati, come materiali di partenza. Il contenuto di S del metallo è del 10% in peso S. Qui vi mostriamo alcuni risultati rappresentativi da esperimenti ad alta pressione eseguiti a 6 GPa e 1.800 ° C, con ben calibrati gruppi multi-incudine 15. Nelle condizioni sperimentali, la lega metallica Fe-FeS è completamente fuso e il silicato (San Carlos olivina) rimane cristallina. L...

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

Gli esperimenti ad alta pressione e alta temperatura descritte qui imitano processi di differenziazione interni pianeta. I processi sono visualizzati e meglio compresi da alta risoluzione di immagini 3D e analisi chimica quantitativa.

Simulazione del Planetary Interior differenziazione processi in 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 Views.  Carnegie Institution of Washington.  Gli esperimenti ad alta pressione e alta temperatura descritte qui imitano processi di differenziazione interni pianeta. I processi sono visualizzati e meglio compresi da alta risoluzione di immagini 3D e analisi chimica quantitativa. 

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.

Rivelare processi dinamici dei materiali in liquidi con liquido di trasmissione microscopia elettronica cellulare

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

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Ingegneria

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.

Esperimenti di fiamma alla Advanced Light Source: nuove informazioni sui processi fuliggine Formazione

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 di goccia Torri per la simulazione sperimentale di collisioni Dust-aggregati nel sistema solare

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 quantificazione delle concentrazioni di idrogeno in superficie e di interfaccia Livelli e materiale sfuso attraverso profili di profondità con l&#39;analisi reazione nucleare

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.

Simulazione di vibrazioni indotte dall&#39;uomo Sulla base della caratterizzato campo pedonale Comportamento

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.

La conoscenza basate su cloud FE Simulazione di stampaggio della lamiera Processi

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.

Wicking Test per unidirezionali Tessuti: Misure di capillare parametri per valutare capillare pressione nei Processi Liquid Composite Molding

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.

Caratterizzazione di Ultra-grana fine e nanocristallini materiali utilizzando la trasmissione Kikuchi Diffraction

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.

Lavorazione dei metalli nanocristallini Bulk presso la 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 ...

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.

Metodi di Ex Situ ed In Situ indagini sulle trasformazioni strutturali: il caso di cristallizzazione dei vetri metallici

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