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41.
Oscar Björklund Alexander GovikLarsgunnar Nilsson 《Journal of Materials Processing Technology》2014,214(11):2748-2758
In this work, selected fracture criteria are applied to predict the fracture of dual-phase steel subjected to non-linear strain paths. Furthermore, the effects of manufacturing history are studied. Four fracture criteria were calibrated in three tests using standard specimens. The fracture criteria were first validated in the circular Nakajima test. A second validation test case was included in order to validate fracture prediction for non-linear strain paths. In this test a sheet metal component was manufactured and subsequently stretched until it fractured. All fracture criteria included in this study predict fracture during the Nakajima test with reasonable accuracy. In the second validation test however, the different fracture criteria show considerable diversity in accumulated damage during manufacturing which caused substantial scatter of the fracture prediction in the subsequent stretching. This shows that manufacturing history influences the prediction of fracture. 相似文献
42.
Oscar Pieiro Carlos Fernndez Mercedes Medrano Macarena Liniers Jose Botija Javier Alonso Xabier Sarasola Carlo Damiani 《Fusion Engineering and Design》2009,84(7-11):1515-1520
The maintenance operations of ITER NB components inside the vessel - Beam Line Components (BLC's) involve the removal of the faulty component, its transport to the hot cell as well as the reverse operations of transport of the repaired/new component and its reinstallation inside the vessel. Prior to the removal of the BLC's the cooling pipes must be detached from the component following a procedure that applies to the cutting of the pipes and subsequent welding when the component is re-installed. The purpose of this study, conducted in the framework of EFDA, is to demonstrate the feasibility of the cut and weld operations on the water pipes of the BLC's using fully remote handling techniques. Viable technologies for the cut and weld operations have been identified within the study; in particular the following aspects will be presented in the paper:
- • Different strategies can be pursued in the detachment of the components depending on the number of cut and weld operations to be performed on the pipes. The selected strategy will impact on the procedure to be followed likewise on important aspects as the requirements of the flexible joints assembled on the pipes.
- • The existing cutting techniques have been examined in the light of the remotely performed pipe cutting at the NB cell. Modifications of commercial tools have been proposed in order to adapt them to the BLC's pipes requirements. The debris produced during the cutting process must be controlled and collected, therefore a cleaning system has been integrated in the adapted cutting tool referred above.
- • The existing welding techniques have been also examined and compared based on different criteria such as complexity, reliability, alignment tolerances, etc. TIG welding is the preferred technique as it stands out for its superior performance. The commercial tools identified need to be adapted to the NB environment.
- • The alignment of the pipes is a critical issue concerning the remote welding. A proper alignment system has been proposed taking into account the pre-selected welding technique.
Keywords: Remote handling; NBI; Cut and weld 相似文献
43.
Red mud, a toxic waste product from bauxite processing, was used as a catalyst for the synthesis of multi-walled carbon nanotubes (MWCNTs) by fluidised bed chemical vapour deposition. The products were analysed using thermogravimetric analysis, Raman spectroscopy, and transmission electron microscopy. Using ethylene at 650 °C a MWCNT yield of 375% (with respect to Fe loading) was obtained. Carbon products were approximately 75% MWCNTs with an IG/ID ratio from Raman spectroscopy of 1.43. The production technique and reaction conditions used are conducive to large-scale CNT production, offering a potential value-added commercial use for red mud. 相似文献
44.
Rieiro Ignacio Carsí Manuel Ruano Oscar A. 《Metallurgical and Materials Transactions A》2017,48(7):3445-3460
Metallurgical and Materials Transactions A - In the present work, a new stability criterion is presented that uses the single sine hyperbolic equation of Garofalo for all values of the... 相似文献
45.
White Jesse F. Lee Jaewoo Hessling Oscar Glaser Bjoern 《Metallurgical and Materials Transactions B》2017,48(1):506-515
Metallurgical and Materials Transactions B - In this study, the spreading and infiltration behavior of liquid slag in contact with different grades of graphite was investigated. The wetting and... 相似文献
46.
Isabel Sánchez Mario Ramírez Marina Casas Angulo Raquel Vigil de la Villa Rosario García-Giménez Oscar Bomati Antonio Zapardiel 《Journal of the American Ceramic Society》2019,102(8):4990-4998
Reutilization of industrial waste products as cement additives yields a number of secondary materials, yet their identification is not always trivial. Confirmation of the formation of a LDH-type (phyllosilicate/carbonate) material is the main purpose of this study. Mineralogically, organic and inorganic compounds form some industrial wastes, among which the phyllosilicates are prominent. Crystalline and amorphous hydrated phases appeared during the pozzolanic reaction in a dehydroxylated phyllosilicate/lime system, whose controlled activation yielded dehydroxylated products with high pozzolanic properties. The LDH-type (phyllosilicate/carbonate) material was one of the reaction products; this material could be considered as the superposition type 1:1 of tetrahedral layers of silicon and aluminum and octahedral layers of aluminum (dehydroxylated kaolinite), generating a positive charge in the interlaminar region compensated by carbonate anions with a basal spacing (001) measured by XRD at 7.57Å. Therefore, several techniques were used to determine whether they could be included in the structural group named Layered Double Hydroxides (LDHs), as they are, too, laminar layers of oxides and hydroxides with a positive laminar charge in the interlayer region compensated by the presence of anions with similar basal spacing. In this research, the effects of activation temperature and calcite proportion were analyzed on the hydrated phases formed after 28 days of pozzolanic reaction in a metakaolin (MK)/lime system. The MK was obtained from a mix of 1:1; 2:1 and 3:1 kaolinite:calcite mixture, thermally activated at 750°C for 2 hours, comparing it with kaolinite activated at 600°C for 2 hours. As the most LDH-rich sample, the 1:1 LDH-type (phyllosilicate/carbonate) phase was characterized using XRD, SEM-EDX, HRTEM-EDX, FTIR, NMR-MAS, and Raman spectroscopy. 相似文献
47.
Oscar A. Anunziata Liliana B. Pierella Marcos Gómez Costa Andrea R. Beltramone 《Catalysis Letters》2001,71(1-2):127-131
Diacetyl (2,3-butanedione) synthesis from methyl ethyl ketone over oxidation zeolites using O2 as oxidant was studied. Various zeolites with Fe, V and Ti as active sites were employed. VS-1, Ti-NCL, Ti-MCM-41 and FeBEA type materials were synthesized and characterized by BET, FTIR, XRD, pyridine adsorption and template desorption. The detailed study of the effect of reaction temperature, the effect of concentration of oxygen and the addition of water was realized. The most active catalyst was zeolites with V as oxidation center. 相似文献
48.
This paper presents the results of an experimental study to measure professionalism for the purpose of assessing a professional development program. Soft skills such as professionalism are increasingly recognized as important, yet measuring and assessing these skills, typically best acquired experientially, has remained challenging. Following established research, we conceptualize professionalism as a construct with the dimensions of autonomy, commitment, belief in public service, self-regulation, and the use of a professional organization as a major referent. We demonstrate how these dimensions can be expressed and the professionalism of free-form text responses measured. These responses are reflections submitted online by participants in a professional development program for undergraduate business majors known as the Management Achievement Program (MAP). Latent semantic analysis is employed to measure the professionalism of these responses and to assess MAP along each of the five dimensions. The method demonstrated in this paper has several advantages over existing methods for assessment, which can be costly, require considerable time and training, and are often tied to subjective interpretation. The method demonstrated here is suitable for replication that leads to continuous improvement by “closing the loop.” 相似文献
49.
The distance from the observer's eye at which the image appears to be focused was measured with monocular, convergent and parallel eyepiece bodies, interchangeable on a Spencer microscope, with a camera lucida prism and a calibrated optometer. Five optometric tests for binocular vision and one for stereopsis made on thirty-four observers revealed no significant correlation with the positions of the images. The apparent image position from the eye using the parallel binocular eyepieces averaged 671 mm, with the convergent eyepiece body at 587 mm, and 469 mm with monocular observation. The relations of these image positions with possible rest equilibrium positions of the accommodative mechanism of the eye and optical design of binocular instruments are discussed. 相似文献
50.
Hydropeaking dam operation and water extractions for irrigation have been broadly stated as alterations to natural flow regimes, which have also been noticed in the Biobío Watershed, in Central Chile, since 1996. In the Biobío River, most of native fish species are endemic and very little is known about them. Their ecological and social values have never been estimated, and there is lack of information about their habitat preferences. Furthermore, changes on fish habitat availability due to natural and/or man‐made causes have not been evaluated. In this study, eight native fish species, in a representative reach of the Biobío River, were studied and their preferred habitats were surveyed and characterized. A hydrodynamic model was built and linked to the fish habitat simulation model CASiMiR. Fuzzy rules and fuzzy sets were developed for describing habitat preference of the native fish species. CASiMiR was then used to simulate how physical habitat conditions vary due to flow control (i.e. upstream dams). Results show how overall habitat quality, expressed as weighted usable area (WUA) and hydraulic habitat suitability (HHS), changes and fluctuates due to the dam operation and how the daily hydropeaking is influencing quantity, quality and location of different habitats. The study suggests that the analysed fish are highly susceptible to flow control, as dams are currently operated, and fish habitat improvement suggestions are proposed. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献