forked from 1b-agent/fieldcraft-upstream
jyvikoandClaude Opus 5.5
3f9e9e30d8
Temperatures now strain the material in nonlinear steps instead of being refused. At finite strain the deformation gradient splits multiplicatively, F = F_m F_theta with F_theta = diag(1 + alpha_i dT) at each point: the material sees F_m and the loops run on the thermally expanded volume J_theta dV0 (mixed elements project det F_m), so the tangent stays consistent. At small strain the split is additive, and elements on their linear stiffness take the equivalent nodal forces as a dead load. The step's temperatures are its temperature loads, or the steady conduction of its temperature conditions and heat loads (one-way coupling, as the linear coupled step); both at once are refused. They ramp with the load factor from each material's reference temperature. Johnson-Cook plasticity softens at the point's temperature. Verified: free expansion and a fully constrained neo-Hookean block at 20 % thermal stretch, full and hybrid (exact); a bar held at its ends heated past yield (exact); the linear limit and the conducted temperatures against the linear solvers; tangents by central differences with a temperature field. Co-Authored-By: Claude Opus 5.5 <[email protected]> Claude-Session: https://claude.ai/code/session_01NmAttHhUZTokgPeEJia8sm