WP11B HEX8 buckling experimental-readiness campaign¶
WP11B is a separate experimental-readiness record. It does not rewrite WP06 or WP06B and does not change the 46-combination registry.
Scope and benchmark¶
The tested capability is HEX8 linear eigenvalue buckling from a linear-elastic
prestress state, for valid bounded geometries and the first positive mode only.
The frozen benchmark is a rectangular solid cantilever block (L=4.0, b=1.2,
h=1.0) with all DOFs fixed on x=0 and uniform nodal dead compression on the
x=L face (P=1.0). The material is homogeneous isotropic linear elasticity
with E=1000, nu=0.3.
The levels (2,2,2), (4,4,4) and (6,6,6) are used to characterize the
route. This is a solid-block physical-consistency benchmark, not a pinned Euler
column oracle. The first mode is expected to be lateral and UZ-dominant for the
declared weak-axis geometry.
Results¶
| Mesh | Critical factor | Solver residual | Recomputed eigen residual | Mode |
|---|---|---|---|---|
| 2×2×2 | 41.9396858064 | 2.15e-13 | 7.64e-14 | UZ |
| 4×4×4 | 21.5199859692 | 3.35e-13 | 5.45e-13 | UZ |
| 6×6×6 | 17.8648777257 | 3.38e-13 | 1.50e-12 | UZ |
All factors are finite and positive; preload residuals are below 1e-8,
geometric-stiffness symmetry is below 1e-12, and the lateral mode fraction is
about 0.984. The refinement trend is positive and decreasing, but adjacent
changes remain about 94.9% and 20.5%. It is therefore recorded as
CHARACTERIZED_ONLY, not as convergence and not as convergence to Euler.
Physical scaling passes the frozen contract: doubling E gives a factor ratio
of 2.00086, doubling preload gives 0.49957, doubling length gives a lower
positive factor (10.03819), and the moderate perturbation changes the level-4
factor by only 0.0046%. Invalid orientation is rejected explicitly. No NaN or
infinite eigenvalue was observed.
Two complete reference replays have identical critical factor, mode, residual
and evidence digest. No comparable current Code_Aster or CalculiX result was
available, so EXTERNAL_ORACLE = NOT_AVAILABLE; no external correlation is
claimed.
Decision and limitations¶
The technical decision is EXPERIMENTAL_CANDIDATE, with proposed public status
EXPERIMENTAL subject to a separate Owner gate. It is not
QUALIFIED_BOUNDED.
The proposed exposure is exploratory/research use only for the declared HEX8 linear eigenvalue buckling route, linear-elastic prestress, valid bounded cantilever solid blocks, explicitly tested constraints, and first positive mode. It excludes general Euler prediction, general convergence, certification, production use, imperfections, nonlinear/post-buckling, plasticity, arbitrary meshes, universal accuracy, multi-mode/mixed-mesh buckling, HEX8R, SRI, B-bar and hourglass formulations.
The historical WP06 Euler FAIL, WP06 mesh-convergence FAIL, and absence of a
comparable external oracle remain unchanged and visible. No numerical source or
0.2.7 evidence was modified.