Discrete element modelling of pebble beds: With application to uniaxial compression tests of ceramic breeder pebble beds

Abstract In this paper, a discrete element simulation scheme for pebble beds in fusion blankets is presented. Each individual pebble is considered as one element obeying equilibrium conditions under contact forces. We study not only the rearrangement of particles but also the overall behaviour of an assembly under the action of macroscopic compressive stresses. Using random close packing as initial configurations, the discrete element simulation of the uniaxial compression test has been quantitatively compared to experiments. This method yields the distribution of the inter-particle contact forces. Moreover, the micro–macro relations have been investigated to relate the microscopic information, such as the maximum contact force and the coordination number inside the assembly, to the macroscopic stress variables.

[1]  Alice Ying,et al.  Thermomechanics of solid breeder and Be pebble bed materials , 2002 .

[2]  Sia Nemat-Nasser,et al.  A micromechanically-based constitutive model for frictional deformation of granular materials , 2000 .

[3]  P. Cundall,et al.  A discrete numerical model for granular assemblies , 1979 .

[4]  L. Verlet.  Computer "Experiments" on Classical Fluids. I. Thermodynamical Properties of Lennard-Jones Molecules , 1967 .

[5]  Harald Kruggel-Emden,et al.  Review and extension of normal force models for the Discrete Element Method , 2007 .

[6]  Alice Ying,et al.  Numerical characterization of thermo-mechanical performance of breeder pebble beds , 2007 .

[7]  J. G. Ziegler,et al.  Optimum Settings for Automatic Controllers , 1942, Journal of Fluids Engineering.

[8]  S. Nemat-Nasser,et al.  A Micromechanical Description of Granular Material Behavior , 1981 .

[9]  Thomas J. R. Hughes,et al.  Encyclopedia of computational mechanics , 2004 .

[10]  Antonios Zavaliangos,et al.  Simulation of multi-axial compaction of granular media from loose to high relative densities , 2005 .

[11]  Schwartz,et al.  Packing of compressible granular materials , 2000, Physical review letters.

[12]  Hulin Huang,et al.  Numerical simulation of ceramic breeder pebble bed thermal creep behavior , 2002 .

[13]  Hans J. Herrmann,et al.  Modeling granular media on the computer , 1998 .

[14]  Numerical and experimental prediction of the thermomechanical performance of pebble beds for solid breeder blanket , 2000 .

[15]  Nenad Bićanić,et al.  Discrete Element Methods , 2004 .

[16]  Norman A. Fleck,et al.  THE COMPACTION OF A RANDOM DISTRIBUTION OF METAL CYLINDERS BY THE DISCRETE ELEMENT METHOD , 2001 .

[17]  Sinisa Dj. Mesarovic,et al.  Adhesive contact of elastic–plastic spheres , 2000 .

[18]  H. Jaeger,et al.  Granular solids, liquids, and gases , 1996 .

[19]  M. Michiel,et al.  X-ray tomography investigations on pebble bed structures , 2008 .

[20]  Christophe L. Martin,et al.  Study of particle rearrangement during powder compaction by the Discrete Element Method , 2003 .

[21]  I. Goldhirsch,et al.  Friction enhances elasticity in granular solids , 2005, Nature.

[22]  H. Zimmermann,et al.  Investigation of the mechanical properties of ceramic breeder materials , 1988 .

[23]  C. Thornton,et al.  Quasi–static deformation of particulate media , 1998, Philosophical Transactions of the Royal Society of London. Series A: Mathematical, Physical and Engineering Sciences.

[24]  A. A. Gusev.  Asymptotic Back Strain Approach for Estimation of Effective Properties of Multiphase Materials , 2007 .

[25]  A. A. Gusev.  Representative volume element size for elastic composites: A numerical study , 1997 .

[26]  W. C. Swope,et al.  A computer simulation method for the calculation of equilibrium constants for the formation of physi , 1981 .

[27]  Marc Kamlah,et al.  Computer simulation of packing structure in pebble beds , 2010 .

[28]  Jodrey,et al.  Computer simulation of close random packing of equal spheres. , 1985, Physical review. A, General physics.

[29]  D. Aquaro,et al.  Experimental and numerical analysis on Pebble beds used in an ITER Test Module Blanket , 2006 .

[30]  J. Roux,et al.  Computer simulation of model cohesive powders: influence of assembling procedure and contact laws on low consolidation states. , 2007, Physical review. E, Statistical, nonlinear, and soft matter physics.

[31]  Y. Gan,et al.  Identification of material parameters of a thermo-mechanical model for pebble beds in fusion blankets , 2007 .

[32]  Norman A. Fleck,et al.  The viscoplastic compaction of composite powders , 1999 .

[33]  D. Aquaro,et al.  Pebble bed thermal–mechanical theoretical model: Application at the geometry of test blanket module of ITER-FEAT nuclear fusion reactor , 2005 .

[34]  C. L. Martin.  Elasticity, fracture and yielding of cold compacted metal powders , 2004 .

[35]  G. Roth,et al.  Crystallisation and microstructure of lithium orthosilicate pebbles , 2007 .

[36]  M. Bolton,et al.  Quantifying the extent of crushing in granular materials: A probability-based predictive method , 2007 .

[37]  Zhang Zhi-hua,et al.  Procurement and Quality Control of Components Important to Safety in Nuclear Engineering Projects , 2006 .

[38]  Mario Nicodemi,et al.  Slow relaxation and compaction of granular systems , 2005, Nature materials.

[39]  S J Antony,et al.  Evolution of force distribution in three-dimensional granular media. , 2000, Physical review. E, Statistical, nonlinear, and soft matter physics.

[40]  Alice Ying,et al.  Application of discrete element method to study mechanical behaviors of ceramic breeder pebble beds , 2007 .