Accession Number:

ADA622343

Title:

Modeling Finite Deformations in Trigonal Ceramic Crystals with Lattice Defects

Descriptive Note:

Journal article

Corporate Author:

ARMY RESEARCH LAB ABERDEEN PROVING GROUND MD WEAPONS AND MATERIALS RESEARCH DIR PROTECTION DIV/IMPACT PHYSICS BRANCH

Personal Author(s):

Report Date:

2010-02-08

Pagination or Media Count:

36.0

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.

Subject Categories:

  • Inorganic Chemistry
  • Ceramics, Refractories and Glass
  • Crystallography
  • Mechanics
  • Thermodynamics

Distribution Statement:

APPROVED FOR PUBLIC RELEASE