DIRECT SIMULATION OF SUBGRAIN DISLOCATION STRUCTURES

1
DIRECT SIMULATION OF SUBGRAIN DISLOCATION
STRUCTURES Srinivasan M. Sivakumar and Michael
Ortiz Graduate Aeronautical Laboratories CALIFORNI
A INSTITUTE OF TECHNOLOGY
AN APPLICATION
EQUAL CHANNEL ANGULAR EXTRUSION

• LARGE DEFORMATION SINGLE CRYSTAL PLASTICITY
• STRONG LATENT HARDENING SINGLE SLIP PLASTICITY
• SEQUENTIAL LAMINATION CONSTRUCTION MIMICS THE
  LAMELLAR DISLOCATION STRUCTURES OBSERVED
• RANK-ONE CONVEXIFICATION ALGORITHM
• NON-LOCAL EFFECTS USING DISLOCATION DENSITY
  TENSOR
• KEY APPLICATIONS
• ALL SEVERE PLASTIC DEFORMN. PROCESSES (SPD)
• EXAMPLE ECAE

(ECAE)
PATCHY SLIP Asaro (1983)
LAMELLAR STRUCTURES (Cu) (Lee, et al. 2002)
MULTIPLE LENGTH SCALE SEPARATIONS
SEQUENTIAL LAMINATION - RANK-1 CONVEXIFICATION
SEQUENTIAL LAMINATES
CALCULATIONS FOR ? 900 ECAE - SINGLE PASS
Shear strain200
FCC AL-CU ALLOY
KOHN, 1991
SINGLE CRYSTAL RESULTS (for a particular random
orientation)
COMPATIBILITY
EQUILIBRIUM EQUATIONS
CONFIGURATIONAL EQUILIBRIUM
ESTIMATED
CALCULATED
(AN A POSTERIORI ESTIMATON OF SIZES)
INTERFACES
POLYCRYSTAL RESULTS
Thanks to Caltechs ASCI ASAP Center C.Tome and
I. Beyerlein (LANL) Matt Fago (Caltech) Lydia
Suarez (Caltech) and Marta Kahl (Caltech)
EXPERIMENTAL
EVOLUTION OF CALCULATED POLE FIGURES