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O.I. Bylya, M.K. Sarangi, N Rohit, A. Nayak, R.A. Vasin and P.L. Blackwell

Abstract

Deformation softening is quite often observed during hot working of different alloys. Steels, aluminium, titanium or nickel alloys can demonstrate a decrease in flow stress under active deformation at constant temperatures and strain rates. Though the background microstructural mechanisms as well as the softening rates can be quite different, the treatment of such processes requires special attention. Deformation softening can cause significant non-uniformity of the metal flow resulting in flow localization, formation of shear bands and variation of the microstructure across the workpiece. This paper is devoted to the investigation of the specific issues which arise in this respect in FEM simulation of processes involving softening. The possible role of softening in shear band formation is studied using numerical simulation and physical modelling. The effect of the softening rate on the probability of flow localization is discussed. The interplay of deformation softening with the stain rate and temperature sensitivity is demonstrated using as an example the simulation of Equal Channel Angular Pressing (ECAP). An approach to account for the deformation softening in FEM simulations via process modelling of the microstructure refinement is proposed.

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Martin Bajčičák and Roland Šuba

References 1. CLARSON, K. D. and all. 2002. Modeling of porosity formation and feeding flow in steel casting . Chicago: Steel Founders’ Society of America. 2. TIAN, C. and all. 2002. Effect of melt cleanliness on the formation of porosity defects in automotive aluminium high pressure die castings. Journal of Materials Processing Technology , 122 (1), pp. 82-93. 3. SHIPING, W. and all. 2003. Numerical simulation of off-centered porosity formation of TiAl-based alloy exhaust valve during vertical centrifugal casting. Modelling and simulation

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Aurelia Mihaela Sandu and Mircea Radu Gorgan

Abstract

Background: Giant arteriovenous malformations (AVMs) are congenital lesions, with nidus sizing more than 6 cm. According to Spetzler-Martin scale, grade V AVMs have a nidus larger than 6 cm in diameter, profound venous drainage and are located in eloquent areas.

Method: We report a case of a 39 years old woman, with giant left frontal AVM, grade V Spetzler-Martin, who was admitted for generalized seizures, with onset 32 years ago, refractory to full dose antiepileptic polytherapy, which severely impaired the patient’s quality of life.

Results: The patient underwent surgery and we performed total resection of the AVM. We emphasize on surgical technique, intraoperative difficulties and outcome.

Conclusions: Surgery is the therapy of choice in AVMs, because it provides cure of the lesion, and is the only treatment capable of preventing hemorrhage and controlling seizures. Management in grade V AVMs is challenging, because of their large size, multiple dilated arterial feeders from anterior and posterior circulation and external carotid arteries, high blood flow, vascular steel from the surrounding brain, enlarged draining veins, profound venous drainage and location in eloquent area. Giant AVMs with high flow nidus, causing a great degree of vascular steel in the surrounding brain, with hypoperfusion of normal parenchyma may develop early normal perfusion pressure breakthrough. Total resection in grade V AVMs can be performed with minimal transient morbidity and favorable outcome. Total resection permits control of intractable seizures with reduced dose of antiepileptic therapy.

Open access

K. Michalek, K. Gryc, M. Tkadleckova and D. Bocek

: 19 th International Conference of Metallurgy and Materials METAL 2010, Roznov p. Radhostem, Czech Republic, EU, pp. 47 (2010). ISBN 978-80-87294-17-8. K. Gryc, et. al.: Physical modelling of flow pattern in 5-strand asymmetrical tundish with baffles. In: 19 th International Conference of Metallurgy and Materials, METAL 2010, Roznov pod Radhostem. Czech Republic. EU, 2010, pp. 42-46, ISBN 978-80-87294-17-8.

Open access

P. Skubisz, A. Żak, M. Burdek, Ł. Lisiecki and P. Micek

] M. Mukherjee, U. Prahl, W. Bleck, Modelling of Microstructure and Flow Stress Evolution during Hot Forging, Steel Res. Intern. 81 , 1102-1116 (2010). [15] P. Skubisz, P. Micek, J. Sińczak, M. Tumidajewicz, Automated determination and on-line correction of emissivity coefficient in controlled cooling of drop forgings, Solid State Phen. 177 , 76-83 (2011). [16] P. Skubisz, J. Sińczak, T. Skowronek, M. Ruminski, Selection of Direct Cooling Conditions for Automotive Lever Made of Microalloy Steel, Arch. Civ. Mech. Eng 12 , 418-426 (2012). [17] J. Sińczak

Open access

M. Rywotycki, K. Miłkowska-Piszczek and L. Trębacz

References Z. Malinowski, M. Rywotycki, T. Telejko, Modeling of heat transfer and fluid flow in continuous casting of steel. 8th ICTP 2005 International Conference on Technology of Plasticity, October 9-13 2005, Verona, Italy, 753-754. B. G. Thomas, Modeling of the continuous casting of steel - past, present and future. Metallurgical Transactions 33B , 12, 795-812 (2002). B. Mochnacki, Zastosowanie metod numerycznych w obliczeniach cieplnych procesu ciągłego odlewania stali

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K. Vrbek, J. Lamut, M. Marolt and M. Knap

, Verbesserte Betriebsverfahren fur die Probenahme und Analyse des Wasserstoffgehaltes von Füssigen Stahl. Eisehüttenwesen 41 , 12, 1131-1135 (1970). [9] P Drozdz, J. Falkus, The modelling of vacuum steel refining in the RH degassing unit based on thermodynamic analysis of the system. Archives of Metallurgy and Materials 52 , 4, 585-591 (2007). [10] J. Falkus, J. Lamut, Model testing of the bath flow through the tundish of the continuous casting machine, Archives of the Metallurgy and Materials 50 , 3, 709-718 (2005). [11] K. Vrbek, Spremljanje vsebnosti vodika med

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Apoloniusz Kodura

Eng Des, 238, (8), 2084-2093 doi: 10.1016/j.nucengdes.2007.10.027. Mitosek M. (2007) Fluid Mechanics in Environmental Engineering, WNT Warsaw, (in Polish). Pires L. F. G., Laidea R. C. C., Baretto C. V. (2004) Transient Flow Analysis of Fast Valve Closure in Short Pipelines, Proceedings of International Pipeline Conference, October 4-8, 2004, Calgary, Alberta, Canada. Ramos H., de Almeida B. A. (2002) Parametric Analysis of Water Hammer Effects in Small Hydro Schemes, Journal of Hydraulic Engineering, 128 (7), pp. 689

Open access

J.-H. Lee, D.-O. Kim and K. Lee

. Zhang, J. Zhejiang Univ-SC. A 7 , 1453 (2006). [14] H.T. Zhao, G.Q. Liu, L. Xu, Mater. Sci. Eng. A 559 , 262 (2013). [15] H.J. McQueen, N.D. Ryan, Mater. Sci. Eng. A 322 , 43 (2002). [16] H. Mirzadeh, A. Najafizadeh, M. Moazeney, Metall. Mater. Trans. A 40 , 2950 (2009). [17] B. Kowalski, C.M. Sellars, M. Pietrzyk, ISIJ Int. 40 , 1230 (2000). [18] W.P. Sun, E.B. Hawbolt, ISIJ Int. 37 , 1000 (1997). [19] J.H. Yang, Q.Y. Liu, D.B. Sun, X.Y. Li, J. Iron Steel Res. Int. 16 , 75 (2009). [20] C. Zener, J.H. Hollomon, J. Appl

Open access

T. Kurşun

References W. R. Oates, A. M. Saitta, Weldind handbook, materials and applications-part 2, Volume 4, American Welding Society (1998). K. Devakumaran, P. K. Ghosh, Thermal characteristics of weld and HAZ during pulse current gas metal arc weld bead deposition on HSLA steel plate, Materials and Manufacturing Processes 25 , 616-630 (2010). P. Praveen, PKDV. Yarlagadda, Meeting challenges in welding of aluminum alloys through pulse gas metal arc welding, Journal of Materials Processing