Modeling Finite Deformations in Trigonal Ceramic Crystals with Lattice Defects

Abstract

A model is developed for thermomechanical behavior of defective, low-symmetry ceramic crystals such as alpha-corundum. Kinematics resolved are nonlinear elastic deformation, thermal expansion, dislocation glide, mechanical twinning, and residual lattice strains associated with eigenstress fields of defects such as dislocations and stacking faults. Multiscale concepts are applied to describe effects of twinning on effective thermoelastic properties. Glide and twinning are thermodynamically irreversible, while free energy accumulates with geometrically necessary dislocations associated with strain and rotation gradients, statistically stored dislocations, and twin boundaries. The model is applied to describe single crystals of corundum. Hardening behaviors of glide and twin systems from the total density of dislocations accumulated during basal slip are quantified for pure and doped corundum crystals. Residual lattice expansion is predicted from nonlinear elasticity and dislocation line and stacking fault energies.

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Document Details

Document Type
Technical Report
Publication Date
Feb 08, 2010
Accession Number
ADA622343

Entities

People

  • John D. Clayton

Organizations

  • United States Army Research Laboratory

Tags

Communities of Interest

  • Energy and Power Technologies

DTIC Thesaurus Topics

  • Bravais Lattices
  • Ceramic Materials
  • Continuum Mechanics
  • Crystal Lattices
  • Crystal Structure
  • Crystallography
  • Crystals
  • Cubic Lattices
  • Elastic Properties
  • Free Energy
  • Mechanical Properties
  • Mechanical Working
  • Mechanics
  • Molecular Dynamics
  • Plastic Properties
  • Thermal Expansion
  • Thermodynamic Properties

Fields of Study

  • Physics

Readers

  • Materials Science and Engineering.
  • Mechanical Engineering/Mechanics of Materials.
  • Structural Health Monitoring of Composite Structures.