Please note that Brownfield Briefing does not offer retrospective discounts to members that are already registered for this conference. The event was open to the public and was exceptionally well attended with a full capacity audience of over people. Through powerful images of melting glaciers, the film shows the impact which climate change is having on the Arctic supporting the latest finding of the Intergovernmental Panel of Climate Change which reports a rapid acceleration of ice melt in the Arctic. This high successful and well-attended event demonstrates that there is an appetite amongst the public for scientific outreach events on matters of environmental issues where they can directly meet and interact with scientists and engineers.
Hot tear formation has been observed during the solidification of a succinonitrile-acetone SCN-acetone alloy by pulling the columnar dendrites in the transverse direction with a stick.
The cracking of the mushy zone hot tears always occurs at grain boundaries. At low volume fraction of solid, the opening can be compensated for by leaner-solute interdendritic liquid i.
Tcd thesis submission higher volume fraction of solid, hot tears directly nucleate in the interdendritic liquid or develop from pre-existing micropores or air bubbles induced by solidification shrinkage. Located across a grain boundary intergranular coalescencethese results shed new light on the formation of hot tears in metallic alloys.
They represent a major defect commonly encountered during the casting of large freezing range alloys and can lead to catastrophic cracking of the cast parts. In Figure 1aa cracked rolling sheet ingot of very large dimensions is shown.
In this example, two hot tears that were initiated during the start-up phase degenerated in two long cracks all along the ingot. In extrusion billets, hot tears are located in the center of the cast part, as shown in Figure 1b. This phenomenon leads to a loss in productivity as high as ten percent for some very sensitive alloys.
The study of hot tear formation has gained a new interest during the last few years, in particular with the derivation of predictive criteria 1356 that can be implemented in finite element method models of casting. Hot tears originate from a lack of liquid feeding of the mushy zone, 1 especially at the end of solidification, and, more precisely, as highlighted by Campbell, when grains start to impinge and finally touch one another, but are still surrounded by a continuous liquid film.
Clyne and Davies 4 defined a criterion in which the time interval spent by the mushy zone in a vulnerable stage appears. As an alternative, Feurer 5 focused on the liquid present between the grains and argued that a hot tear will nucleate as a pore if the liquid is no longer able to fill the intergranular openings.
Recently, Farup and Mo 6 formulated a two-phase model of a deforming, solidifying mushy zone where both interdendritic liquid flow and thermally-induced deformation of the solid phase were taken into account. Although the investigations on as-cracked surfaces flourish, in situ observations of hot tear formation are rare.
Nevertheless, transparent organic alloys offer an interesting alternative to observe the formation of hot cracks. Succinonitrile with acetone SCN-acetone alloy was selected by Farup et al. The same device has been used in the present investigation with two improvements: The main purpose of the present work is to visualize in situ hot tear formation during solidification, and, in particular, to study the nucleation of hot tears and the coalescence of grains.
The schematics of the experimental device used to observe in-situ the formation of hot tears in succinonitrile-acetone alloys Click on the figure to enlarge it.
A small quantity of Fuchsin was added to the transparent alloy typically 0. Temperature was measured every second by placing a type-K thermocouple, 50 mm in diameter, in the cell. This measurement was coupled with video recording of the growing dendrites in order to deduce the temperature at which dendrites coalesce or bridge.
As already reported in Reference 7hot tears always appear between two grains; the grain boundary being the last part of the system to solidify. Moreover, two situations can be distinguished from these observations.
First, when the stick is pulled at too high liquid fractions, liquid can feed the opening because of the high permeability of the mush. Therefore, the crack is healed by solute-enriched liquid and no defect results from this event, as shown in Figure 3except maybe some enhanced segregation.
A healed hot crack Click on the figure to enlarge it. The formation of a "healed" hot crack. To best experience this presentation, you should employ the latest version of RealPlayer.
Animation 1 shows how, by using a stick to induce a tensile opening in the organic alloy, deformation concentrates at the grain boundary. The dotted lines indicate the position of grain boundaries. In this case, the opening takes place between grains 2 and 3 i. Moreover, the solid fraction at this point of solidification is still low enough to allow liquid metal to feed the opening owing to the relatively high permeability of the mush.Received the Early Career Researcher Award Press release by Elsevier: Dr.
Amir A. Zadpoor has received the Early Career Researcher Award on the 6 th International Conference on Mechanics of Biomaterials and Tissues held in Waikoloa, Hawaii, USA from December This is the first award of the journal of this sort with the purpose of identifying young outstanding researchers in the.
A 'Academic Costumes', British Medical Journal, , Vol.
II, pp. (23 July).A short essay on how to identify the degrees held by medical people from their robes. Includes a section on the origins of academical dress and a .
Akustisches Kolloquium Das Akustische Kolloquium ist ein Forum zur Präsentation und Diskusion von Forschungen, die am Institut für Technische Akustik durchgeführt wurden. Trinity College Dublin Theses. Trinity College Dublin research theses can be found using Stella Search and refining your search results by selecting the format ‘TCD Thesis’ for print theses, or ‘TCD E-Thesis’ for electronic theses, or by limiting results to the Library Collection ‘TCD Theses’ for both.
Joint SimInhale COST Action Summer School and 5 th Workshop on Pulmonary Drug Delivery. Dublin, September, Trinity College Dublin.
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