crystal-plasticity-workflow

Crystal Plasticity Workflow

Description

This skill covers crystal plasticity and crystal plasticity finite element (CPFE) modeling of metals: orientation representations and conventions, slip-system definitions for FCC/BCC/HCP, resolved shear stress and Schmid factors, the multiplicative decomposition F = Fe Fp, rate-dependent and rate-independent flow rules, hardening laws, single-crystal and polycrystal (RVE) simulation, texture evolution, parameter calibration and identifiability, and validation against stress-strain curves and crystallographic observables. Invoke this skill when anisotropy, crystallographic slip, texture evolution, or grain-scale heterogeneity control the mechanical response and an isotropic or phenomenological anisotropic plasticity model is insufficient.

Domain Context

Crystal plasticity resolves plastic deformation onto crystallographic slip systems rather than treating the material as an isotropic continuum. It sits above dislocation dynamics and below macroscopic phenomenological plasticity: it does not resolve individual dislocations, but it carries crystallographic orientation, slip-system geometry, and their evolution, which lets it predict anisotropy, lattice rotation, and texture development that isotropic J2 plasticity cannot. Choosing the right model tier matters — isotropic plasticity for texture-free bulk response, phenomenological anisotropic (e.g. Hill/Barlat) yield surfaces for formability without explicit crystallography, crystal plasticity when slip-system activity and orientation evolution are the target, and CPFE when grain morphology and intergranular stress fields must be spatially resolved.

The kinematic core is the multiplicative decomposition of the deformation gradient F = Fe Fp, where Fp accumulates plastic shear on slip systems and Fe carries elastic stretch and lattice rotation. The plastic velocity gradient Lp = Fp_dot Fp^{-1} is a sum over slip systems of shear rate times the Schmid tensor (slip direction dyad slip-plane normal). The resolved shear stress on each system is the projection of the Mandel/second Piola-Kirchhoff stress onto its Schmid tensor, and slip is driven by that resolved stress relative to a slip resistance. Rate-dependent (viscoplastic power-law) formulations regularize slip-system selection and improve convergence at the cost of a rate-sensitivity parameter; rate-independent formulations require an active-set or singular-value treatment of the ambiguous slip-selection problem. [EXPERT REVIEW NEEDED]