Brittle Fracture
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Figure 1: Embrittled grain boundary networks are an example of heterogeneous random materials. Randomness comes from different strength properties of various grain boundaries (special boundaries as Sigma 3, Sigma 9, or random). The location of the fracture surfaces is predicted using efficient graph-theoretical optimization algorithm [1], and compared with actual surfaces from embrittled polycrystalline materials, such as bismuth-embrittled copper.

Fractality of Fracture Surfaces in Polycrystalline Materials


Eira T. Seppälä, Bryan Reed, Mukul Kumar and Robert E. Rudd



In this joint project with experimentalists from CMS/MSTD fracture surfaces of embrittled polycrystalline materials, such as pure aluminum and bismuth-embrittled copper, are studied both by computations and experimentally. In statistical mechanics fracture surfaces of random media have attracted considerable interest due to their self-affine scaling properties with a characteristic exponent, zeta. Grain boundary networks are constructed computationally by matching empirical special boundary fractions (e.g. of Sigma 3, Sigma 9, or random types) and triple junction distributions which have been obtained from electron backscatter diffraction (EBSD) data using scanning electron microscopy (SEM) [2]. The minimum energy paths through the dual networks of the grain boundary structures are searched, where the edges of the networks are assigned with strength values depending on the type of the grain boundary. These minimum energy paths serve as predicted cracks through the samples [1]. Finally such properties as roughness, special boundaries belonging to the cracks, etc., of the surfaces of the simulated networks with the properties from actual fracture surfaces in polycrystalline materials are compared.

SELECTED PUBLICATIONS


  1. "Roughness Scaling of Fracture Surfaces in Polycrystalline Materials," E. T. Seppälä, B. W. Reed, M. Kumar, R. W. Minich, and R. E. Rudd, Mater. Research Soc. Symp. Proc. 819, N1.4.1-6 (2004).
  2. "The Structure of the Cubic Coincident Site Lattice Rotation Group," B. W. Reed, R. W. Minich, R. E. Rudd and M. Kumar, Acta Cryst. A60, 263-277 (2004).
  3. "Quasi-Static Cracks and Minimal Energy Surfaces," V. I. Räisänen, E. T. Seppälä, M. J. Alava, and P. M. Duxbury, Phys. Rev. Lett. 80, 329 (1998).
  4. "Role of topological constraints on the statistical properties of grain boundary networks," R. W. Minich, C. A. Schuh, and M. Kumar, Phys. Rev. B 66, 052101 (2002).
EOS & Materials Theory | Condensed Matter Physics | Physics & Adv. Tech. | LLNL

Maintained by Robert E. Rudd -- Last updated on 7 March 2007.
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