The radial return of the explicit update is now J2::radial_return, called by
both solvers, with the consistent tangent J2::tangent (Simo & Hughes 1998,
Box 3.2). The new elastoplastic module gives the implicit material point:
Simo's multiplicative plasticity with the exponential return map in the
principal logarithmic strains (CMAME 99, 1992) and its spatial tangent through
the Daleckii-Krein divided differences of the logarithm, and the additive
radial return of small strain with kinematic hardening. MaterialModel::Plastic
carries it, decoupled (deviatoric return, Hencky volume) so hybrid elements
take it. The element loops of finite.rs gain small-strain kinematics for
inelastic materials and pass history through the mixed path. Every tangent is
checked against central differences, element by element, from a plastic
history.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01NmAttHhUZTokgPeEJia8sm
solve.nonlinear follows a nonlinear static step in load increments: dead
loads and prescribed displacements ramp with the load factor, a pressure
follows the deformed faces (its load stiffness symmetrised so the
supernodal Cholesky stays), the consistent tangent is refactored every
iteration with an optional line search, and an increment converges on
force, displacement and energy together. Increments start from the
extrapolated last one, grow after fast convergence and are cut back on
inversion, a non-finite or growing residual, an indefinite tangent or too
many iterations; the step stops cleanly at the minimum increment, the
increment cap or the Newton iteration limit. Elements are assembled in
parallel in label order (same bits on any thread count). Results carry
Cauchy stress, logarithmic strain, the increment history and a displacement
frame per increment, which results.frame and the results panel show.
Trusses, shells, beams, plane stress, incompatible modes, temperature and
centrifugal loads are refused by name; couplings warn that they stay
linear.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01NmAttHhUZTokgPeEJia8sm
