FESADev/references/quad_02_notes.md

quad_02 Reference Notes

Purpose

quad_02 is the first stored Abaqus TYPE=S4 reference pair intended for the Phase 1 MITC4 rebaseline path.

The original Abaqus input remains preserved as provenance:

• quad_02.inp
• quad_02_displacements.csv
• quad_02_reactionforces.csv

The Phase 1 parser-compatible derivative input is:

• quad_02_phase1.inp

Provenance

• Source solver: Abaqus/CAE Learning Edition 2024, as recorded in quad_02.inp.
• Original job name: quad_02.
• Source model name: Model-1.
• Unit system: self-consistent source units. FESA does not enforce or convert units.

Compatibility

quad_02.inp uses TYPE=S4, which is the Phase 1 target mapped to FESA MITC4.

The original file also contains Abaqus/CAE features outside the current Phase 1 parser subset:

• *Part
• *Assembly
• *Instance
• *Density
• output and restart request keywords

These features remain unsupported in Phase 1 unless docs/ABAQUS_INPUT_SUBSET.md and ADRs are explicitly updated. Tests must continue to reject the original file as unsupported provenance.

Normalized Input

quad_02_phase1.inp is a derivative input created for Phase 1 parser and later solver regression work.

It preserves:

• 121 node ids and coordinates.
• 100 TYPE=S4 quadrilateral elements and connectivity.
• Elastic material values E = 7.0e10, nu = 0.3.
• Shell thickness 1.0.
• Fixed boundary nodes from the original assembly-level boundary set.
• Concentrated load at node 2, DOF 3, magnitude -100000.0.

It removes:

• Abaqus/CAE Part/Assembly/Instance scaffolding.
• *Density, because density is not used by Phase 1 linear static analysis.
• restart/output requests.
• step increment parameters and static time data not needed by the Phase 1 parser subset.

Result Mapping

quad_02_displacements.csv is an Abaqus-exported nodal displacement table with 121 rows.

Required columns:

• Node Label
• U-U1
• U-U2
• U-U3
• UR-UR1
• UR-UR2
• UR-UR3

It maps to FESA field output:

/results/steps/Step-1/frames/0/fieldOutputs/U

with component order:

UX, UY, UZ, RX, RY, RZ

quad_02_reactionforces.csv is an Abaqus-exported nodal reaction force/moment table with 121 rows.

Required columns:

• Node Label
• RF-RF1
• RF-RF2
• RF-RF3
• RM-RM1
• RM-RM2
• RM-RM3

It maps to FESA field output:

/results/steps/Step-1/frames/0/fieldOutputs/RF

with component order:

RFX, RFY, RFZ, RMX, RMY, RMZ

Initial Tolerance

The active automated displacement regression uses:

abs_tol = 1.0e-12
rel_tol = 1.0e-5
reference_scale = 1.0

Do not tune tolerances or drilling stiffness to make this single case pass.

Automated Regression Status

quad_02_phase1.inp and quad_02_displacements.csv are wired into the Phase 1 test suite as the first stored Abaqus displacement regression.

The regression compares FESA U against the stored Abaqus CSV by node id and uses the tolerance above.

quad_02_phase1.inp and quad_02_reactionforces.csv are also wired through the reaction CSV loader and node-wise RF comparator. This comparison currently records a known non-passing gap rather than an accepted pass gate:

abs_tol = 1.0e-6
rel_tol = 1.0e-5
reference_scale = 1.0
max_abs_error ~= 612.751347
max_rel_error ~= 0.494032
first_mismatch = node 1 RFZ, expected 6860.0, actual 6652.459896

Do not relax reaction tolerances to make this case pass. Treat the mismatch as a solver/formulation verification item.

Current Limitations

• The stored Abaqus reaction CSV is available, but node-wise RF agreement is not accepted yet because the current comparison fails.
• This is currently the only passing stored Abaqus reference regression. The PRD target still requires at least three stored reference models: one single-element case, one simple multi-element plate/shell case, and one curved shell benchmark.