FluxFEM

FluxFEM 0.3.10

FluxFEM 0.3.10 is a broad structural-mechanics release. It collects the recent work on structural elements, coupling constraints, plate/shell helpers, mixed-dimensional models, Craig-Bampton ROM workflows, contact utilities, and nonlinear- material diagnostics.

Capability Overview

• Core FEM

  • Weak-form-centered assembly
  • JAX-based residual/Jacobian workflows
  • SciPy/NumPy-oriented sparse assembly paths
  • Hex/tet continuum spaces
  • Dirichlet handling
  • Mass assembly
  • VTU export utilities

• Structural Elements

  • Spring helpers
  • Mass helpers
  • Dashpot helpers
  • 2D bar/truss helpers
  • 3D bar/truss helpers
  • 2D frame helpers
  • 3D Euler-Bernoulli beam helpers
  • Beam point loads
  • Beam distributed/uniform loads
  • Truss point loads
  • Consistent/lumped mass support where available

• Constraints and Coupling

  • MPC-style constraint rows
  • Tie constraints
  • Rigid/RBE2-style constraints
  • RBE3-style distributed coupling
  • Distributed coupling rows
  • Bolt preload helpers
  • Component-selective slave/reference coupling
  • Solid-beam RBE3-style coupling
  • Solid-truss RBE3-style coupling
  • Solid-shell translational ties
  • Nonmatching shell-solid translational interpolation
  • Solid-shell patch-to-edge RBE3-style coupling

• Plate and Shell

  • Q4 Mindlin/Reissner-Mindlin plate helpers
  • Q4 Reissner-Mindlin shell helpers
  • Reduced shear integration
  • Full shear integration
  • MITC4-style shear option
  • Plate/shell stiffness assembly
  • Plate/shell mass assembly
  • Shell examples with 2D and tilted 3D coordinates
  • Shear-locking benchmark tutorials
  • Shell-solid cantilever comparison tutorial

• Dynamics

  • Linear Newmark workflows
  • Lumped spring-mass-dashpot examples
  • Beam tip spring/dashpot dynamics
  • Reduced-coordinate Newmark utilities
  • Mass/stiffness projection workflows

• Craig-Bampton ROM

  • CB basis construction from assembled FE systems
  • Stiffness/mass matrix reduction
  • Sparse-preserving projection utilities
  • Matrix-free reduced operator actions
  • Retained interface/contact DOF workflows
  • Multi-field CB builder workflows
  • Beam/truss/plate/shell ROM coverage
  • Solid-shell, solid-beam, and solid-truss CB checks
  • Mixed solid + shell + beam CB-ROM checks
  • Static, modal, and Newmark-history regression coverage
  • Contact-ready retained interface examples

• Contact and Interfaces

  • Penalty-style contact helpers
  • Active contact update loops
  • Node/surface contact utilities
  • Paired-surface contact utilities
  • Contact diagnostics
  • KKT/contact builder paths
  • Mortar-oriented utilities
  • Two-body contact VTU tutorial
  • Supported-box contact tutorials
  • Contact/CB-ROM example workflows

• Nonlinear Materials

  • Neo-Hookean hyperelastic residual examples
  • Small-strain J2 material-point return mapping
  • J2 FE quadrature-state helpers
  • J2 load-step helper with committed history updates
  • J2 VTU output
  • J2 load-history CSV output
  • J2 Newton-iteration CSV output
  • J2 dtype defaults aligned with active JAX x64 configuration
  • J2 convergence diagnostics
  • J2 material-point tangent finite-difference tests
  • J2 FE residual Jacobian finite-difference checks

• Tutorials and Documentation

  • Roadmap implementation status added to README
  • Beam/truss tutorials
  • Plate/shell tutorials
  • Shell-solid coupling tutorials
  • Contact tutorials
  • Craig-Bampton ROM tutorials
  • Nonlinear J2 tutorial
  • PETSc shell solver tutorial
  • VTU-output examples for inspection

Notes

• RBE2/RBE3 helpers are FluxFEM-style tested constructions, not complete Nastran card-compatible implementations.
• Current shell helpers focus on flat/planar Reissner-Mindlin-style workflows; general curved shell kinematics and layered shells remain future work.
• J2 plasticity is now well covered for material-point and small FE verification cases, but production restart/output and broader material lifecycle APIs remain future work.
• Large-sliding/frictional contact and full mortar contact lifecycle management remain active development areas.
• Polished support-layout optimization, shape-parameter optimization, and nonlinear/contact ROM workflows are still good next targets.