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Отправлено: 29.07.08 02:35. Заголовок: И снова об извилистости... ;-(
Очередная публикация на сию тему.... ;-( Electrical and thermal tortuosity in powder compacts Granular Matter Springer Berlin / Heidelberg ISSN 1434-5021 (Print) 1434-7636 (Online) Volume 9, Number 6 / Ноябрь 2007 г. DOI 10.1007/s10035-007-0061-3 pp 401-406 Electrical and thermal tortuosity in powder compacts J. M. Montes1 , F. G. Cuevas1 and J. Cintas1 (1) Department of Mechanical and Materials Engineering, Escuela Superior de Ingenieros, Universidad de Sevilla, Camino de los Descubrimientos, s/n, 41092 Sevilla, Spain Received: 29 January 2007 Published online: 8 September 2007 Abstract A simple equation to calculate the effective mean path to be travelled by the heat flow or electrical current in a porous powdered material is proposed. In this equation, the effective mean path is a function of the sample porosity degree and the tap porosity of the original powder. This latter parameter determines to a great extent the compact pore structure, since it depends on the powder particle size, shape and distribution. The proposed equation has been validated using real metallographic images from sintered powders compacts. For measurements, a computer program, based on the Pathfinding A* Algorithm, has been developed. Results are in very good agreement with theoretical predictions. The proposed equation can be useful to model the electrical and thermal conductivity of sintered compacts. Keywords Tortuosity - Modelling - Pathfinding - A star algorithm -------------------------------------------------------------------------------- J. M. Montes Email: jmontes@esi.us.es References 1. Bear J. (1988). Dynamics of Fluids in Porous Media. Dover Publications, New York 2. Dullien F.A. (1979). Porous Media: Fluids Transport and Pore Structure, 2nd Ed. Academic, San Diego 3. Smith D.W. and Marth T. (1981). Principles and processes. In: Hausner, H.H., Antes, H.W. and Smith, G.D. (eds) Modern Developments in Powder Metallurgy, vol 12, pp 835–854. MPIF, Princeton 4. Smith, D.W., Smugeresky, J.E., Meyer, B.A.: Technical Report SAND87-8227, Sandia National Laboratories, Livermore (Oct.1987) 5. Meyer B.A. and Smith D.W. (1985). Flow through porous media: comparison of consolidated and unconsolidated materials. Indust. Eng. Chem. Fundamentals 24(3): 360–368 6. Koponen A., Kataja M. and Timonen J. (1996). Tortuous flow porous media. Phys. Rev. E. 54(1): 406–410 7. Exner, H.E., Hougardy, H.P.: Quantitative image analysis of microstructures. DGM Informationsgesellschaft mbH, Berlin (1988) 8. Montes J.M., Cuevas F.G. and Cintas J. (2005). Effective area in powder compacts under uniaxial compression. Mater. Sci. Eng. A. 395: 208–213 9. Montes J.M., Cuevas F.G. and Cintas J. (2006). A new expression for the effective pressure on powders under compression. Comp. Mater. Sci. 36: 329–337 10. Rabin S. (2002). A.I. Game programming wisdom. Charles River Media, Princeton 11. Lester, P.: A* Pathfinding for Beginners www.policyalmanac.org/games/aStarTutorial.htm, as on August 2007 12. MPIF Standard 46: Determination of tap density of metal powders. In: Standard Test Methods for Metal Powders and Powder Metallurgy Products. MPIF, Princeton (2002) 13. MPIF Standard 45: Determination of Compressibility of Metal Powders. In: Standard Test Methods for Metal Powders and Powder Metallurgy Products. MPIF, Princeton (2002) 14. Lenel F.V. (1980). Powder Metallurgy. Principles and Applications. MPIF, Princeton, 99–116
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