Finite element approximation of finite deformation dislocation mechanics

• Published in: Computer methods in applied mechanics and engineering Vol. 367; p. 113076
• Main Authors: Arora, Rajat, Zhang, Xiaohan, Acharya, Amit
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01.08.2020; Elsevier BV
• Subjects: Boundary conditions; Deformation; Dislocation mechanics; Edge dislocations; Elastic anisotropy; Finite deformation; Mathematical analysis; Mechanics; Mechanics (physics); Mesoscale phenomena; S waves; Size effect; Size effects; Software; Strain gradient plasticity; Stress distribution; Time dependence; Dislocation mechanics; Finite deformation; Strain gradient plasticity; Size effect
• ISSN: 0045-7825; 1879-2138
• DOI: 10.1016/j.cma.2020.113076

We develop and demonstrate the first general computational tool for finite deformation static and dynamic dislocation mechanics. A finite element formulation of finite deformation (Mesoscale) Field Dislocation Mechanics theory is presented. The model is a minimal enhancement of classical crystal/J2 plasticity that fundamentally accounts for polar/excess dislocations at the mesoscale. It has the ability to compute the static and dynamic finite deformation stress fields of arbitrary (evolving) dislocation distributions in finite bodies of arbitrary shape and elastic anisotropy under general boundary conditions. This capability is used to present a comparison of the static stress fields, at finite and small deformations, for screw and edge dislocations, revealing heretofore unexpected differences. The computational framework is verified against the sharply contrasting predictions of geometrically linear and nonlinear theories for the stress field of a spatially homogeneous dislocation distribution in the body, as well as against other exact results of the theory. Verification tests of the time-dependent numerics are also presented. Size effects in crystal and isotropic versions of the theory are shown to be a natural consequence of the model and are validated against available experimental data. With inertial effects incorporated, the development of an (asymmetric) propagating Mach cone is demonstrated in the finite deformation theory when a dislocation moves at speeds greater than the linear elastic shear wave speed of the material. •The first general computational tool for finite deformation static and dynamic dislocation mechanics.•Comparison of finite and small deformation stress fields of dislocations revealing unexpected differences.•Sharply contrasting geometrically linear and nonlinear stress fields of a spatially homogeneous dislocation distribution.•Validated prediction of size effects in crystal and isotropic versions of the theory.•(Asymmetric) propagating Mach cone at finite deformation for a dislocation moving faster than linear elastic shear wave speed.