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Journal articles on the topic "Conditions locales de solidification":
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Balint, Stefan, and Agneta M. Balint. "On the Creation of a Stable Drop-Like Static Meniscus, Appropriate for the Growth of a Single Crystal Tube with Prior Specified Inner and Outer Radii." Mathematical Problems in Engineering 2009 (2009): 1–22. http://dx.doi.org/10.1155/2009/348538.
A theoretical procedure for the creation of a stable drop-like static meniscus, appropriate for the growth of a single crystal tube, with a priori specified inner and outer radius, is presented. The method locates the controllable partpof the pressure difference across the free surface. It consists in a set of calculus, which leads to the determination of the melt column height (between the horizontal crucible melt level and the shaper top level) in function of the pressure of the gas flow (introduced in the furnace for release the heat) in order to obtain the desired meniscus. The procedure is presented in general and is numerically illustrated for InSb tubes. The novelty is the algorithm for the exact determination ofp, which has to be used, the determination of the melt column height, and the evaluation of the effect of shaper radii. The setting of the thermal conditions, which assure that for the obtained static meniscus the solidification conditions are satisfied at the “right” places, is not considered here.
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Maqsood, Dr Naila. "A Depiction of Indian Muslim Women’s Plight in Culture and Literature Around the Mid-Eighteen Century." Journal of Law & Social Studies 4, no. 1 (March 31, 2022): 86–97. http://dx.doi.org/10.52279/jlss.04.01.8697.
This paper locates the Muslim women’s social conditions particularly in the Indo-Pak Subcontinent which largely arose out of two sources; a) evolution of Islam and development of several schools of jurisprudence; b) Muslim’s contact with the Indian culture. Over several centuries, more particularly from the early 13th century onward (by this time, Muslim Turkish rule had been established in India), and the impact of Bhakti movement both on Hindus and Muslims and spread of teachings of Guru Nanak and Bhagat Kabir, Muslims came to adopt many of the Hindu notions and practices. This was in addition to attitudes that came with them by their conversion to Islam. The first part of the paper deals with the effects of Hindu culture regarding status of women on Muslims. The second part of the paper discusses the plight of Muslim women in literature i.e Punjab folk lore of Heer Ranjha. It tries to convey the thoughts on several social customs, particularly emphasizing the various aspects of women’s life. The third part provides the ethnographic evidence which confirms that women, particularly in rural areas, have faced low status and problem connected with rapes, marriages, dowry, and divorces, etc. With solidification of customs, discrimination against a female endures through centuries. As a result, Muslim women were become socially backward, economically susceptible, and politically marginalized segment of society.
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Turchin, A. N., Dmitry G. Eskin, and Laurens Katgerman. "Unsteady-State Solidification under Forced Flow Conditions." Materials Science Forum 561-565 (October 2007): 991–94. http://dx.doi.org/10.4028/www.scientific.net/msf.561-565.991.
The interaction between flow and progressing solidification front is of great importance, since it occurs in all casting processes. The present paper provides a better understanding of the flow phenomena and associated complex effects on solidification in a rectangular cavity under forced flow conditions, by means of experiments and computer simulations. It is shown that the cavity-driven flow with solidification is determined by several interacting features. The variation in bulk flow velocity and initial superheat dramatically changes the macro- and microstructure, promoting grain refinement, formation of peculiar grain and dendrite morphologies, etc. In particular, twinned feathery grains are found in the structure formed under certain heat and flow conditions during solidification. Some correlations between twinned feathery morphology, flow and solidification parameters are obtained. The effect of flow vortices on progressing solidification front and their effects on structure evolution are analyzed. Finally, the quantitative correlations between microstructure, solidification and flow parameters are established.
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MOTEGI, Tetsuichi. "Solidification of metals under microgravity conditions." Journal of Japan Institute of Light Metals 41, no. 12 (1991): 858–65. http://dx.doi.org/10.2464/jilm.41.858.
Sobolev, S. L. "Rapid solidification under local nonequilibrium conditions." Physical Review E 55, no. 6 (June 1, 1997): 6845–54. http://dx.doi.org/10.1103/physreve.55.6845.
Kurz, W., and R. Trivedi. "Eutectic growth under rapid solidification conditions." Metallurgical Transactions A 22, no. 12 (December 1991): 3051–57. http://dx.doi.org/10.1007/bf02650266.
Lysenko, A. B., G. V. Borisova, O. L. Kravets, and A. A. Lysenko. "Solidification of metals under melt quenching conditions." Physics of Metals and Metallography 106, no. 5 (November 2008): 435–43. http://dx.doi.org/10.1134/s0031918x0811001x.
Li, Q., D. Li, and B. Qian. "Modelling dendrite evolution under rapid solidification conditions." International Journal of Cast Metals Research 17, no. 6 (December 2004): 339–44. http://dx.doi.org/10.1179/136404604225022720.
Giovanola, B., and W. Kurz. "Modeling of microsegregation under rapid solidification conditions." Metallurgical Transactions A 21, no. 1 (January 1990): 260–63. http://dx.doi.org/10.1007/bf02656445.
Dissertations / Theses on the topic "Conditions locales de solidification":
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Banos, Julien. "Modélisation du procédé de refusion à l’arc sous vide : Échanges thermiques et défauts de solidification." Electronic Thesis or Diss., Université de Lorraine, 2023. http://www.theses.fr/2023LORR0117.
Le procédé de refusion à l'arc sous vide (Vacuum Arc Remelting ou VAR en anglais) est employé dans la production d'alliages métalliques à haute valeur ajoutée tels que les alliages de titane ou superalliages base nickel à destination de l'industrie aéronautique. La maîtrise des conditions de solidification constitue un enjeu industriel important pour obtenir des lingots d'une homogénéité chimique adéquate et dépourvus de défauts de solidification. Les travaux présentés dans ce document visent à améliorer la description des échanges thermiques dans un modèle du procédé VAR (SOLAR) et proposer une nouvelle approche pour la prédiction des défauts de solidification de type canaux ségrégés. Dans un premier temps, la description dans le modèle des échanges thermiques entre l'électrode, le lingot, la lingotière et le circuit de refroidissement a été améliorée. Les modifications ont fait l'objet de validation par comparaison des résultats numériques avec des mesures sur des refusions industrielles réelles. Un dispositif expérimental original de mesure de température à la paroi extérieure de la lingotière adapté aux refusions industrielles a été conçu et utilisé lors d'une campagne expérimentale sur site industriel lors de la refusion d'un alliage de titane. Les mesures obtenues ont été confrontées aux résultats numériques de SOLAR. Ces deux activités ont abouti à une première implémentation du phénomène de side-arcing dans le modèle. En parallèle, une approche numérique multi-échelle a été développée pour prédire la formation de canaux ségrégés en fonction des conditions locales de solidification. Une première étude sur un alliage Sn-Pb a été réalisée et un critère mathématique de prédiction a été calculé à partir des résultats. Cette première étude montre un impact du gradient thermique sur la formation de canaux ségrégés bien plus faible que celui généralement considéré dans la littérature The Vacuum Arc Remelting (VAR) process is used in the production of high-added value metals such as titanium alloys or nickel-based superalloys for the aerospace industry. The control of solidification conditions is an important industrial issue in order to process ingots of adequate chemical homogeneity and free of solidification defects. The work presented in this manuscript aims at improving the description of heat exchanges in a VAR process model (SOLAR) and at proposing a new approach for the prediction of segregated channels type solidification defects. First, the description of the heat exchanges in the model between the electrode, the ingot, the mould and the cooling circuit has been improved. These modifications were validated by comparing the numerical results with measurements from real industrial melts. An original experimental apparatus for measuring the external mould temperature adapted to industrial melts was designed. This apparatus was used during an experimental campaign on an industrial site during the remelting of a titanium alloy. The measurements obtained were compared with the numerical results from SOLAR. These two activities led to a first implementation of the side-arcing phenomenon in the model. In parallel, a multi-scale numerical approach was developed to predict the formation of segregated channels as a function of local solidification conditions. A first study on a Sn-Pb alloy was carried out and a mathematical criterion was calculated from the results. This first study shows a much lower impact of the thermal gradient on the formation of segregated channels than that generally considered in the literature
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Buset, Dominique. "Quelques conditions locales et extrêmales en théorie des graphes." Doctoral thesis, Universite Libre de Bruxelles, 1998. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/212094.
L'évolution des stratégies d'investissements directs étrangers (ide) vers des stratégies globales a laissé penser a une perte de substance des territoires. En effet, si dans le cadre les stratégies traditionnelles, l'implantation a l'étranger dépendait de variables locales prédéterminées, dans le cadre de la stratégie globale l'espace propre à la firme apparait comme un élément déterminant. L'objet de la thèse est de prendre le contre-pied de cette affirmation. Paradoxalement, les variables locales prennent une signification nouvelle dans les stratégies globales. Cela offre ainsi des possibilités de mise en oeuvre de politiques d'attraction des investisseurs par les institutions locales. En fait, le site d'implantation est devenu un élément de compétitivité des firmes. Parmi les facteurs de localisation recherchés, on trouve la main-d'oeuvre qualifiée, des activités complémentaires, la proximité de fournisseurs,. . Le territoire attire donc parce qu'il offre des avantages tels que des effets de proximité, des économies externes, des économies d'agglomeration. A l'attrait de variables locales prédéterminées comme les ressources du sol ou du sous-sol, une offre de main-d'oeuvre bon marche (. . . ) succède donc celui de variables locales construites. Cette construction de variables peut être soutenue par des institutions locales. Les interventions peuvent prendre différentes formes, des incitations financières aux actions de promotion-prospection et à la construction d'avantages afin de favoriser la génération de ressources spécifiques. Pour que ces interventions soient efficaces, il faut une coordination entre les différentes mesures d'attraction. Il parait également nécessaire d'assurer une meilleure coordination entre les divers niveaux d'intervention territoriaux. L'observation de quelques cas d'ide en bretagne ces dernières années a permis de mettre en évidence cette évolution dans les stratégies d'ide et dans les rapports au territoire. Dans le domaine des télécoms, particulièrement, la région a réussi a constituer des ressources spécifiques qui en font une des régions les plus attractives de France en la matière.
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Brun, Catherine, and Christine Dupuis. "Quel avenir pour la montagne ariégeoise ? : acteurs, dynamiques locales et fonctions de l'espace." Paris 7, 1985. http://www.theses.fr/1985PA070020.
Aborder la complexite au travers de p. Creation de deux entites villageois nees de 2 discontinuites. Une approche methodologique originale permet de designer les interactions entre technique. Territoire-societe, et de les analyser sur le terrain par diachronie. C'est ainsi. Que l'on decouvre la variete des "frontieres" et leur signification To deal with complexite through the creation of the towns borned from two discontinuities. An original methodological approach aiming to show. The interrelations between techiolog - geograph and society, and to analyse them by "diachron". It is thus demonstrated the bordere variet and their meaning
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Stainsack, Cristiane. "Mécanismes et conditions locales de concrétisation de l'innovation inverse : le cas du Brésil." Thesis, Paris Sciences et Lettres (ComUE), 2018. http://www.theses.fr/2018PSLED051.
Le travail de thèse porte sur l’innovation inverse et ses particularités managériales et organisationnelles au sein d’une filiale d’entreprise multinationale (EMN) localisée dans un pays émergent. Contrairement au modèle classique, l’innovation inverse peut se produire à partir d’un pays en voie de développement ou émergent, et ensuite être transférée vers un pays développé. Dans le cadre de cette recherche, nous nous intéressons au Brésil, un pays émergent où des entreprises mondiales disposent de centres de R&D de référence en Amérique Latine. L’innovation portée par la filiale d’une EMN est réalisée en fonction de divers facteurs et caractéristiques locales qui contribuent à ce que l’innovation menée par cette filiale se propage à l’échelle globale. Les objectifs de la recherche sont de mieux comprendre comment les EMN’s s’organisent dans une approche d’innovation inverse, de progresser sur l’éclairage théorique, et de proposer un modèle de management favorisant l’innovation mondiale à partir des initiatives locales dans un pays émergent. Nos travaux mettent en œuvre une démarche qualitative qui s’appuie sur une méthode d’études multi-cas. Notre contribution est un nouveau modèle théorique et fonctionnel pour l’innovation inverse prenant en compte les éléments qui contribuent à ce phénomène: l’intégration entre la maison mère et la filiale, la décentralisation de la R&D et la valorisation de compétences locales et l’insertion dans le système national d’innovation (SNI). Nos résultats de recherche ont mis en avant l’existence d’autres types d’innovations au-delà de l’innovation technologique qui induit une innovation mondiale. Nous avons observé que les innovations au niveau managérial, processus ou marketing sont absorbées au sein de la maison mère et diffusées vers d’autres filiales à une échelle mondiale Our research work concerns reverse innovation and its managerial and organizational features in a multinational corporation (MNC) subsidiary located in emerging markets. Unlike the traditional model, reverse innovation can occur from a developing or emerging country, and then be transferred to a developed country. Our empirical field is Brazil, an emerging country which hosts the reference R&D centers for Latin America of several global companies. The successful transfer to the global scale of an innovation coming from the subsidiary of an MNC depends on various factors and local characteristics that are explored in the thesis. The aims of this PhD dissertation are to better understand the mechanisms of reverse innovation in the context of MNCs, to advance theory and to propose a management model encouraging global innovation based on local initiatives in an emerging country. We show that practices carried out by MNC subsidiaries can have organizational, managerial and environmental implications that can account for the success of reverse innovation. Our research work implements a qualitative approach based on a multi-case study method. Our contribution is a new theoretical and functional model for reverse innovation that takes into account the elements that contribute to this phenomenon: the integration between the parent corporation and the subsidiary, the decentralization of R&D and the valorization of local skills and the insertion into the national system of innovation (SNI). Our research results highlight the existence of other types of innovation beyond technological innovation that lead to global innovation. We show that innovations at management, process or marketing level are absorbed within the parent company and disseminated to other subsidiaries on a global level
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Dramé, Seydou. "Les radios locales au Burkina Faso." Paris 2, 2007. http://www.theses.fr/2007PA020014.
Cette thèse présente le fonctionnement actuel des radios locales au Burkina Faso, le processus de création de ces médias de proximité, leur historique et les problèmes vécus par leurs promoteurs et les stations elles-mêmes, les radios locales sont étudiées comme des outils de développement et d'épanouissement des populations locales, surtout rurales
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Ledgard, Louise Joyce. "Macrostructural and microstructural evolution during unidirectional solidification of aluminium alloys under steady state conditions." Thesis, University of Liverpool, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.385219.
Feng, Zhili. "A methodology for quantifyin gthe thermal and mechanical conditions for weld metal solidification cracking." The Ohio State University, 1993. http://rave.ohiolink.edu/etdc/view?acc_num=osu1258486536.
Feng, Zhili. "A methodology for quantifying the thermal and mechanical conditions for weld metal solidification cracking." The Ohio State University, 1993. http://rave.ohiolink.edu/etdc/view?acc_num=osu1297357046.
Francisco, Cebrián Abellán, and Panadero Moya Miguel, eds. América Latina: Lógicas locales, lógicas globales. Cuenca: Universidad de Castilla-La Mancha, 1999.
Veiga, Danilo. Sociedades locales y territorio en el escenario de la globalización. Montevideo, Uruguay: Universidad de la República, Facultad de Ciencias Sociales, Departamento de Sociología, 2000.
González, José Guadalupe Rivera. Globalización, procesos locales, territorios y cambio sociocultural en San Luis Potosí. México, D.F: Universidad Autónoma de San Luis Potosí, 2010.
Coutiño, Reynol Díaz. Los límites locales del crecimiento: Sinaloa en la dimensión global. Culiacán Rosales, Sinaloa: Universidad Autónoma de Sinaloa, Instituto de Investigaciones Económicas y Sociales, 2004.
Serna, Carlos La. La cuestión de género en las políticas locales. Córdoba, Argentina]: Universidad Nacional de Córdoba, Instituto de Investigación y Formación en Administración Pública, Programa de Investigación Modernidad y Políticas Sociales, 2011.
Book chapters on the topic "Conditions locales de solidification":
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Cross, Carl E., N. Coniglio, P. Schempp, and M. Mousavi. "Critical Conditions for Weld Solidification Crack Growth." In Hot Cracking Phenomena in Welds III, 25–41. Berlin, Heidelberg: Springer Berlin Heidelberg, 2011. http://dx.doi.org/10.1007/978-3-642-16864-2_2.
Turchin, A. N., Dmitry G. Eskin, and Laurens Katgerman. "Unsteady-State Solidification under Forced Flow Conditions." In Materials Science Forum, 991–94. Stafa: Trans Tech Publications Ltd., 2007. http://dx.doi.org/10.4028/0-87849-462-6.991.
Glicksman, M. E., J. E. Frei, J. C. LaCombe, M. B. Koss, A. O. Lupulescu, and C. Giummarra. "Time-Dependent Behavior of Dendrites Under Diffusion-Controlled Conditions." In Interactive Dynamics of Convection and Solidification, 33–46. Dordrecht: Springer Netherlands, 2001. http://dx.doi.org/10.1007/978-94-015-9807-1_5.
Fredriksson, Hasse. "On the Solidification of Metal Alloys during Microgravity Conditions." In Advances in the Science and Engineering of Casting Solidification, 9–13. Hoboken, NJ, USA: John Wiley & Sons, Inc., 2015. http://dx.doi.org/10.1002/9781119093367.ch2.
Fredriksson, Hasse. "On the Solidification of Metal Alloys during Microgravity Conditions." In Advances in the Science and Engineering of Casting Solidification, 9–13. Cham: Springer International Publishing, 2015. http://dx.doi.org/10.1007/978-3-319-48117-3_2.
Cerimele, M. M., D. Mansutti, and F. Pistella. "Front-Fixing Modeling of Directional Solidification in Microgravity Conditions." In Progress in Industrial Mathematics at ECMI 2000, 197–203. Berlin, Heidelberg: Springer Berlin Heidelberg, 2002. http://dx.doi.org/10.1007/978-3-662-04784-2_26.
Cochet-Muchy, D., and S. Païdassi. "The Nd15Fe77B8 Microstructure: Some Effects of Oxygen for Different Solidification Conditions." In Concerted European Action on Magnets (CEAM), 369–76. Dordrecht: Springer Netherlands, 1989. http://dx.doi.org/10.1007/978-94-009-1135-2_31.
Ohshima, Yosuke, Takeshi Yoshikawa, and Kazuki Morita. "Effect of Solidification Conditions on Si Growth from Si-Cu Melts." In Supplemental Proceedings, 677–84. Hoboken, NJ, USA: John Wiley & Sons, Inc., 2011. http://dx.doi.org/10.1002/9781118062111.ch78.
Ruxanda, Roxana, and Richard Obara. "Microstructure Investigation of Aluminum Die-Cast Parts with Different Gating Conditions Tested in Fatigue." In Advances in the Science and Engineering of Casting Solidification, 101–9. Hoboken, NJ, USA: John Wiley & Sons, Inc., 2015. http://dx.doi.org/10.1002/9781119093367.ch13.
Conference papers on the topic "Conditions locales de solidification":
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Shu, Y., and B. Q. Li. "Phase-Field Modeling of Microstructure Formation of Polycrystalline Materials in Various Cooling Conditions." In ASME 2006 International Mechanical Engineering Congress and Exposition. ASMEDC, 2006. http://dx.doi.org/10.1115/imece2006-13900.
This paper presents a discontinuous finite element computational framework for the numerical solution to the phase-field equations during the solidification of polycrystalline materials. An important feature of the discontinuous method is that the continuity across the elements within the calculation domain is only weakly enforced, rather than rigorously enforced as done in conventional finite element method. The mathematical formulation and computational implementation are briefly described. Numerical simulations are conducted to study the interactions between the grains and the nuclei that are initially located close to or away from the boundary of the bulk grain. The phase-field evolutions during solidification in various cooling conditions are presented. Results indicate the dependence of grain growth behavior and its interface morphology on the undercooling temperature suppressed to the liquid pool. And this dependence is not so much related to the distance between the grain and nuclei.
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Hope, Adam T., Hai-Lin Chen, João Pedro Oliveira, and Carolin Fink. "Solidification and Homogenization Modeling of High Entropy Alloys." In HT 2017. ASM International, 2017. http://dx.doi.org/10.31399/asm.cp.ht2017p0302.
Abstract High entropy alloys (HEA) are an exciting new class of alloys composed of several metallic elements with equiatomic or near-equiatomic composition to maximize configurational entropy, leading to desirable properties. However, during solidification, as in casting or welding processes, elements segregate, creating local regions of distinct composition. In conventional alloy systems, homogenization heat treatments are used to remove this segregation effect. This study examines the conditions of the heat treatment needed in HEA alloys. First, the solidification behavior of equiatomic alloy composition AlCoCrCuFeNi is modeled using the Scheil module within Thermo-Calc along with the TCHEA2 database. Energy dispersive spectroscopy (EDS) is performed across the dendrite arms of the as-melted HEA to compare with the Scheil calculations. The resulting dendritic and interdendritic compositions are used as inputs in Thermo- Calc to determine the stable phases as a function of temperature. Selected heat treatments are conducted on the as-melted HEA to compare with the calculation results.
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Nissley, Nathan, Timothy D. Anderson, Fredrick F. Noecker, Caleb Roepke, Morgan Gallagher, and Martin Hukle. "Dissimilar Metal Welding of Nitronic 50 HS® and 25% Cr Super Duplex Stainless Steel." In ASME 2014 33rd International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/omae2014-24706.
High pressure tubing and associated tubing couplers are critical components required for the operational control of subsea oil and gas production equipment. Tubing couplers used in subsea oil and gas developments are commonly made from Nitronic 50 HS® (N50HS) due to its high strength, corrosion resistance, and resistance to galling. Nitronic couplers are typically welded to several dissimilar metals including super duplex stainless steel (SDSS) control tubing using SDSS filler metals such as AWS A5.9 ER2594. Recent evaluations have found that sigma (σ) phase forms in N50HS weldments and its effect is not broadly understood by industry. During N50HS solidification, Scheil solidification conditions establish compositional gradients in the unmixed zone located along the fusion line adjacent to the N50HS base metal. This solidification-induced segregation promotes compositions that are susceptible to interdendritic intermetallic compound formation when they are reheated by subsequent weld passes such as in multipass welding or at weld start-stop locations. Decreasing heat input is a common approach to reduce or eliminate the formation of intermetallic compounds in SDSS. Although decreasing heat input can reduce the amount of energy available to drive the solid state transformation from ferrite to σ, it does not change the solidification mode (AF) or solidification conditions from Scheil to para-equilibrium within the range of cooling rates possible with arc welding processes. As such, the compositional gradients that promote intermetallic compound formation along the N50HS fusion line can only be minimized through heat input control and cannot be eliminated in arc welds regardless of the heat input used. The effects of σ on toughness and corrosion resistance of Nitronic weldments were evaluated. N50HS solidified samples with up to 2 volume percent σ were found to have CVN of >40J at −40°C, and no evidence of pitting at 25°C in the ASTM G48 test.
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Rawlings, A. L. K., A. J. Birnbaum, J. G. Michopoulos, J. C. Steuben, A. P. Iliopoulos, and H. Ryou. "Simulation Informed Effects of Solidification Rate on 316L Single Tracks Produced by Selective Laser Melting." In ASME 2020 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/detc2020-22451.
Abstract The formation of sub-grain cellular structures generated during the rapid solidification associated with selective laser melting (SLM) typically yields enhanced mechanical properties in terms of yield stress without considerable loss in ductility when compared with those of wrought material. The extent to which the sub-grain structure appears under standard metallographic preparation shows dependence on multiple systematic conditions. This study identifies the effects of solidification and cooling rate on the grain and sub-grain structure in stainless steel through varying the processing parameters (laser power, scan velocity and spot size) of single tracks on both as-received, small grain and annealed, giant grain substrates. The process parameters, in conjunction with the initial substrate microstructure, are key components in understanding the resulting microstructure. Process parameters, particularly scan velocity, dictate the solidification rate and primary regrowth directions while the initial microstructure and its thermomechanical history dictate the propensity for stored strain energy density. Modeling the thermal process allows for experimental analysis within the context of predicted location within processing space as it pertains to local interface velocity and temperature gradient. Furthermore, it highlights the fact that this specific material system behaves in a manner that is inconsistent with classical solidification theory.
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Vasileiou, A. N. "Investigating the suitability of using a single heat transfer coefficient in metal casting simulation: An inverse approach." In Material Forming. Materials Research Forum LLC, 2023. http://dx.doi.org/10.21741/9781644902479-128.
Abstract. In metal casting simulation the Heat Transfer Coefficient (HTC) is unknown as it depends on melt and mold materials, on the casting modulus at different regions of the casting and on local conditions at the mold-casting gap. In this paper, thermocouple measurements at three regions of a brass investment casting provided reference cooling curves. A genetic algorithm (GA) determined the optimum 3-step time-dependent HTC for the whole of the casting in a simulation program for which cooling curves are as close as possible to the reference curves. The resulting prediction of solidification times is satisfactory but prediction of qualitative characteristics such as start / end of solidification in different regions was not accurate enough.
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Schulte-Fischedick, Jan, Rainer Tamme, and Ulf Herrmann. "CFD Analysis of the Cool Down Behaviour of Molten Salt Thermal Storage Systems." In ASME 2008 2nd International Conference on Energy Sustainability collocated with the Heat Transfer, Fluids Engineering, and 3rd Energy Nanotechnology Conferences. ASMEDC, 2008. http://dx.doi.org/10.1115/es2008-54101.
CFD analysis has been conducted to obtain information on heat losses, velocity and temperature distribution of large molten salt Thermal Energy Storage (TES) systems. A two-tank 880 MWh storage system was modeled according to the molten salt TES containment design proposed for the 50 MWel commercial parabolic trough solar thermal power plants in Spain. Heat losses were established using the Finite Element Method (FEM), and used to determine the boundary conditions for the subsequent two- and three-dimensional Computational Fluid Mechanics (CFD) calculations. The investigations reveal that a high heat loss flux occurs at the lower edges of the salt storage tanks (between side wall and bottom plate). Thus the maximum temperature difference can be found at this location, resulting in the onset of local solidification within 3.25 days in the case of the empty cool tank. As a consequence, the detailed design of the lower edge has a large impact on both the overall heat losses and the period until the onset of local solidification.
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Wang, G. X., Chengcai Yao, and B. T. F. Chung. "On Physical Mechanisms of Mushy Zone Formation in Solidification of Pure Semitransparent Materials." In ASME 1999 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 1999. http://dx.doi.org/10.1115/imece1999-1039.
Abstract Two different models, the isothermal mushy zone model and the non-equilibrium planar interface model, are employed to solve the solidification problem of a one-dimensional semitransparent slab subject to radiative and convective cooling at the surface. The mushy zone model is based on the assumption of local equilibrium and predicts the formation of a mushy zone as soon as the temperature of the slab surface reaches the equilibrium melting temperature. The non-equilibrium planar interface model, on the other hand, assumes a stable planar solid/liquid interface during solidification. It allows the existence of melt undercooling at the interface and in the bulk melt. The stability of the planar interface is then examined approximately using the linear stability criterion derived for an opaque material. It is found that a planar interface would be stable even if a large undercooling is generated in the bulk melt in front of the interface. If the rate of external heat transfer is small, however, the planar interface will break down and develop into thermal cells or dendrites. In addition, a transition from a mushy zone to a planar interface is also observed. Based on these results, the thermodynamics and kinetics of crystalline nucleation and growth are examined to illustrate the physical mechanisms of mushy zone formation during solidification of a semi transparent material. It is suggested that the isothermal mushy model and the planar interface model are valid only under corresponding processing conditions, and more research is needed to provide a complete description of the process.
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Yang, Zhuo, Brandon Lane, Yan Lu, Ho Yeung, Jaehyuk Kim, Yande Ndiaye, and Sundar Krishnamurty. "Using Coaxial Melt Pool Monitoring Images to Estimate Cooling Rate for Powder Bed Fusion Additive Manufacturing." In ASME 2022 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. American Society of Mechanical Engineers, 2022. http://dx.doi.org/10.1115/detc2022-89934.
Abstract Cooling rate is a decisive index to characterize melt pool solidification and determine local microstructure formation in metal powder bed fusion processes. Traditional methods to estimate the cooling rate include in-situ temperature measurement and thermal simulation. However, these methods may not be accurate or efficient enough under complex conditions in real-time. This paper proposes a method to approximate the melt pool cooling rate using temperature profile acquired via thermally-calibrated melt pool camera, and based on continuous pixel tracking result. The proposed method can estimate the temperature and associated cooling rate for every pixel immediately, which is potentially applicable for real-time process monitoring. This paper focuses on investigating image data processing, method development, and cooling condition analysis. This work presents the preliminary result of the cooling rate estimation under different conditions such as position, layer number, and overhanging.
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Wan, Y. P., X. Y. Jiang, H. Zhang, S. Sampath, V. Prasad, and J. R. Fincke. "Modeling of Oxidation of Plasma-Sprayed Molybdenum Coatings." In ITSC 2000, edited by Christopher C. Berndt. ASM International, 2000. http://dx.doi.org/10.31399/asm.cp.itsc2000p0135.
Abstract A model for oxidation of molybdenum particles during plasma spray deposition is developed. The diffusion of metal an-ions or oxygen cat-ions through a thin oxidized film, chemical reactions on the surface, and diffusion of oxidant in gas phase are considered as possible rate-controlling mechanisms with controlling parameters as the temperature of the particle surface, and local oxygen concentration and flow field surrounding the particle. The deposition of molten particle and its rapid solidification and deformation is treated using a Madejski-type model, in which the mechanical energy conservation equation is solved to determine the splat deformation and one-dimensional heat conduction equation with phase change is solved to predict the solidification and temperature evolution. Calculations are performed for a single molybdenum particle sprayed under the Sulzer Metco-9MB spraying conditions. Results show that the mechanism that controls the oxidation of this droplet is the diffusion of metal/oxygen ions through a very thin oxide film. A higher substrate temperature results in a larger rate of oxidation at the splat surface, and hence, a larger oxygen content in the coating layer. Compared to the oxidation of droplet during m-flight, the oxidation during deposition is not weak and can become dominant at high substrate temperatures.
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Kocherlakota, Pavan, and Jerome Savarimuthu. "Effect of Welding Conditions on TIG Welded AISI 304 Stainless Steels Using FEM and Experimental Methods." In ASME 2008 Pressure Vessels and Piping Conference. ASMEDC, 2008. http://dx.doi.org/10.1115/pvp2008-61047.
Classical approaches to the modeling of welding, whilst accurate, are not readily usable in the industry. The time and cost associated with running such models appear to be the main reasons contributing to the situation. The use of computer simulative techniques has the potential to significantly reduce the cost of welded fabrications by allowing for predictions to be made long before a single weld bead is put down on the workshop floor. In this paper, a computational procedure is presented to analyze temperature fields during TIG welding process using a non linear transient thermal analysis in ANSYS [1]. Various phenomena associated with welding like temperature dependent material properties, effects of latent heat of fusion are accounted for in the model. The heat loss through radiation and effect of shielding gas are neglected here. This work has considered only a 2D analysis considering axis symmetric model. The analysis was done on AISI 304 stainless steels. The effect of welding conditions on the weld microstructure is studied over a range of heat input values and welding speed and the columnar to equiaxed transition (CET) is investigated. The influence of the welding conditions is related to changes in temperature gradient G, and local solidification velocity R, at the solid-liquid interface along the weld pool edge. It was observed that increase in the welding speed increases the equiaxed fraction. The effect of alloy composition on CET was neglected during this study. The results of finite element analysis were compared with experimental results and were found in good agreement. Based on these studies, a simplified modelling procedure of reasonable accuracy was proposed.
Reports on the topic "Conditions locales de solidification":
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Campbell, J., and F. Incropera. Experimental study of solidification under mixed convection conditions. Office of Scientific and Technical Information (OSTI), February 1990. http://dx.doi.org/10.2172/7196276.
Chernov, A. A., and J. L. Belof. Homogeneous vs. Heterogeneous Nucleation Modes of Solidification at Strong Driving Force Conditions. Office of Scientific and Technical Information (OSTI), April 2018. http://dx.doi.org/10.2172/1459152.
Magirl, C. S., and F. P. Incropera. Flow and morphological conditions associated with the directional solidification of aqueous ammonium chloride. Office of Scientific and Technical Information (OSTI), January 1993. http://dx.doi.org/10.2172/6794124.
Magirl, C. S., and F. P. Incropera. Flow and morphological conditions associated with the directional solidification of aqueous ammonium chloride. Annual performance report. Office of Scientific and Technical Information (OSTI), January 1993. http://dx.doi.org/10.2172/10130109.
Miller, Jonathan D., and Tresa M. Pollock. Development and Application of a Protocol for Definition of Process Conditions for Directional Solidification: Integrating Fundamental Theory, Experimentation and Modeling Tools (Preprint). Fort Belvoir, VA: Defense Technical Information Center, March 2012. http://dx.doi.org/10.21236/ada559145.
Needham, Glenn R., Uri Gerson, Gloria DeGrandi-Hoffman, D. Samatero, J. Yoder, and William Bruce. Integrated Management of Tracheal Mite, Acarapis woodi, and of Varroa Mite, Varroa jacobsoni, Major Pests of Honey Bees. United States Department of Agriculture, March 2000. http://dx.doi.org/10.32747/2000.7573068.bard.
Objectives: The Israeli work plan regarding HBTM included: (a) producing a better diagnostic method; (b) following infestations during the season and evaluating damage to resistant bees and, (c) controlling HBTM by conventional means under local conditions. For varroa our plans to try novel control (e.g. oil novel control (e.g. oil patties & essential oils) were initially delayed by very low pest populations, then disrupted by the emergence of fluvalinate resistance. We monitored the spread of resistance to understand it better, and analyzed an underlying biochemical resistance mechanism in varroa. The US work plan focused on novel management methods for both mites with an emphasis on reducing use of traditional insecticides due to resistance and contamination issues. Objectives were: (a) evaluating plant essential oils for varroa control; (b) exploring the vulnerability of varroa to desiccation for their management; and (c) looking for biological variation in HBTM that could explain virulence variability between colonies. Although the initial PI at the USDA Beltsville Bee Lab, W.A. Bruce, retired during the project we made significant strides especially on varroa water balance. Subcontracts were performed by Yoder (Illinois College) on varroa water balance and DeGrandi-Hoffman (USDA) who evaluated plant essential oils for their potential to control varroa. We devised an IPM strategy for mite control i the U.S. Background: Mites that parasitize honey bees are a global problem. They are threatening the survival of managed and feral bees, the well-being of commercial/hobby beekeeping, and due to pollination, the future of some agricultural commodities is threatened. Specific economic consequences of these mites are that: (a) apiculture/breeder business are failing; (b) fewer colonies exist; (c) demand and cost for hive leasing are growing; (d) incidences of bee pathogens are increasing; and, (e) there are ore problems with commercial-reared bees. As a reflection of the continued significance f bee mites, a mite book is now in press (Webster & delaplane, 2000); and the 2nd International Conference on Africanized Honey Bees and Bee Mites is scheduled (April, 2000, Arizona). The first such conference was at OSU (1987, GRN was co-organizer). The major challenge is controlling two very different mites within a colony while not adversely impacting the hive. Colony management practices vary, as do the laws dictating acaricide use. Our basic postulates were that: (a) both mites are of economic importance with moderate to high infestations but not at low rates and, (b) once established they will not be eradicated. A novel strategy was devised that deals with the pests concomitantly by maintaining populations at low levels, without unnecessary recourse to synthetic acaricides. Major Conclusions, Solutions, Achievements: A major recent revelation is that there are several species of "Varroa jacobsoni" (Anderson & Trueman 1999). Work on control, resistance, population dynamics, and virulence awaits knowing whether this is a problem. In the U.S. there was no difference between varroa from three locales in terms of water balance parameters (AZ, MN & PA), which bodes well for our work to date. Winter varroa (U.S.) were more prone to desiccation than during other seasons. Varroa sensitivity to desiccation has important implications for improving IPM. Several botanicals showed some promise for varroa control (thymol & origanum). Unfortunately there is varroa resistance to Apistan in Israel but a resistance mechanism was detected for the first time. The Israel team also has a new method for HBTM diagnosis. Annual tracheal mite population trends in Israel were characterized, which will help in targeting treatment. Effects of HBTM on honey yields were shown. HBTM control by Amitraz was demonstrated for at least 6 months. Showing partial resistance by Buckfast bees to HBTM will be an important IPM tactic in Israel and U.S.
