docs: simplify MITC4 verification and drilling scope
This commit is contained in:
KOKO\Mimi
@@ -8,9 +8,9 @@
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- source_numerical_review: `docs/numerical-reviews/linear-static-mitc4-shell-review.md`
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- status: `ready-for-numerical-review`
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- owner_agent: `formulation-agent`
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- date: `2026-08-11`
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- revision_basis: numerical review commit `0a5aad4`; findings `NR-C01` through
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`NR-C05` and decisions `NR-D01` through `NR-D02`
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- date: `2026-08-12`
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- revision_basis: approved independent-reference policy, fixed drilling rule, and
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removal of calibration gates `NR-O01` through `NR-O04`
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- revision_state: `ready-for-numerical-rereview-not-implementation-planning`
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- product_execution_scope: `small-strain, small-rotation linear static only`
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- future_formulation_scope: `geometrically nonlinear Total Lagrangian residual/tangent; not executable`
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@@ -41,11 +41,10 @@ Source labels `S4` and `S4R` both select this one FESA formulation by an approve
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semantic mapping. They do not select Abaqus integration or stabilization behavior,
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and this document makes no Abaqus formulation-equivalence claim.
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Exact drilling reference family/coefficient, drilling-energy warning ratio,
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smooth-director angle, and geometry thresholds remain Numerical Review decisions.
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The common dimensionless drilling coordinate, geometry-measure inventory,
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drilling-load projection tolerance, and normalized algebraic checks are fixed below
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by the first Numerical Review. No remaining open symbol is an implementation default.
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The drilling rule is fixed below by the approved requirements. Coefficient sweeps,
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drilling-energy warnings and datasets, smooth-director calibration (`NR-O03`), and
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distortion/warp threshold calibration (`NR-O04`) are outside the implementation gate.
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The drilling-load projection and normalized algebraic checks remain fixed below.
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## 2. Scope and assumptions
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@@ -218,18 +217,10 @@ $$
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\mathbf d_I=\frac{\mathbf s_I}{\|\mathbf s_I\|}.
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$$
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Incident elements are accumulated in the same stable order. After averaging, every
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incident deviation
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$$
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\theta_{eI}=\cos^{-1}\!\left(
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\operatorname{clamp}(\mathbf n_e\cdot\mathbf d_I,-1,1)\right)
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$$
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must satisfy an approved smooth-patch bound `theta_smooth`. The research value
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`20 degrees` is only the first Numerical Review candidate. It is not fixed here.
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Zero or near-zero cross products and averaged vectors fail using approved
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scale-aware tolerances. They are never replaced with a global axis.
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Incident elements are accumulated in the same stable order. No additional
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`theta_smooth` rejection is applied. Nonfinite or zero cross products and averaged
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vectors fail; they are never replaced with a global axis. The pairwise orientation
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rule above remains the exact supported-patch predicate.
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### 4.3 Deterministic nodal tangent frame
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@@ -575,7 +566,7 @@ Duplicate nodes, self-intersection, degenerate midsurface area, and reversed
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connectivity are separate fail-closed geometry errors. No failed location is
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discarded or replaced by a value from another point.
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### 9.3 Scale-aware measures
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### 9.3 Basic geometry predicates
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Let the consecutive midsurface edge inventory be
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@@ -585,73 +576,21 @@ $$
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\boxed{L_e=\max_{(I,J)\in\mathcal E}\|\mathbf X_J-\mathbf X_I\|}.
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$$
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`L_e` must be finite and strictly positive. It is the common element length used by
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geometry checks and the DOF scaling in Section 12.5. At every distinct in-plane
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location in the center, Gauss, tying, and committed recovery inventory, define
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$$
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a(\xi,\eta)=\|\mathbf A_\xi\times\mathbf A_\eta\|,
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\qquad
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\boxed{a_g(\xi,\eta)=\frac{a(\xi,\eta)}{L_e^2}},
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$$
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$$
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\mathbf n_s(\xi,\eta)=
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\frac{\mathbf A_\xi\times\mathbf A_\eta}{a(\xi,\eta)},
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\qquad
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c_d(\xi,\eta)=\mathbf n_s\cdot\overline{\mathbf d}.
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$$
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`a_g` is the normalized surface-collapse/aspect measure. In particular, for
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`A_xi=(1,0,0)` and `A_eta=(0,epsilon,0)` with `L_e=O(1)`, `a_g -> 0` as
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`epsilon -> 0`; the angular measure below alone cannot detect that collapse.
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At every full three-dimensional validation point, define the dimensionless
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angular/director determinant measure
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$$
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j_s=\frac{J}
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{\|\mathbf G_\xi\|\,\|\mathbf G_\eta\|\,\|\mathbf G_\zeta\|}.
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$$
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For all positive finite point determinants, define the element-variation measure
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$$
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\boxed{r_J=\frac{J_{min}}{J_{max}}},
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\qquad
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J_{min}=\min_{p\in\mathcal P_V}J_p,
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\quad
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J_{max}=\max_{p\in\mathcal P_V}J_p,
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$$
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and the surface-normal warpage measure relative to the center normal
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$$
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\boxed{\theta_w=
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\max_{p\in\mathcal P_S}
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\cos^{-1}\!\left(\operatorname{clamp}
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(\mathbf n_s(0,0)\cdot\mathbf n_s(p),-1,1)\right)}.
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$$
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Here `P_V` contains every volume Gauss point, tying point at `zeta=0`, center, and
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every committed bottom/middle/top recovery point; `P_S` contains their distinct
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in-plane projections. A valid element must satisfy, without denominator clamping,
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`L_e` must be finite and strictly positive. At every center, Gauss, tying, and
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committed recovery location required by Section 9.2, the following quantities must
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be finite and satisfy
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$$
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\boxed{
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J_p>0,\quad
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j_{s,p}>\tau_{ang},\quad
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a_{g,p}>\tau_{area},\quad
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c_{d,p}>\tau_{dir},\quad
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r_J>\tau_{var},\quad
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\theta_w<\theta_{warp}.}
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\|\mathbf A_\xi\times\mathbf A_\eta\|>0,
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\qquad J>0.}
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$$
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The measures and their location inventory are fixed by this formulation revision.
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The positive dimensionless thresholds remain `needs-numerical-calibration`; they
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must separate valid distortion/warp sweeps from collapsed negative sequences before
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Numerical Review may approve them. No `max(1, geometry_scale)`, zero denominator,
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failed-point omission, or pointwise orientation repair is permitted.
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The covariant vectors and reciprocal bases must also be finite. Duplicate nodes,
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self-intersection, zero-area mappings, and nonpositive determinants fail before
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stiffness or recovery is committed. No failed location is omitted, averaged, clamped,
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or repaired. This feature defines no calibrated distortion, aspect, warpage, or
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director-angle threshold; `NR-O03` and `NR-O04` are not acceptance tests.
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## 10. Linear kinematics and MITC4 shear projection
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@@ -846,97 +785,40 @@ $$
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\mathbf f_{phys}^{24}=\mathbf K_{phys}^{24}\mathbf q_g.
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$$
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### 12.2 Drilling candidate contract
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### 12.2 Fixed drilling stabilization
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Let
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Let `R` be the index set of the eight director-tangent rotational coordinates in the
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physical local ordering `q_20`. Form the finite strictly positive diagonal inventory
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$$
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\mathbf K_d^l=\operatorname{diag}(k_{d,1},k_{d,2},k_{d,3},k_{d,4}),
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\qquad k_{d,I}>0,
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\mathcal R_+=\{(K_{20})_{ii}\mid i\in\mathcal R,
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(K_{20})_{ii}>0,\ (K_{20})_{ii}\text{ finite}\}.
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$$
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with rotational-stiffness units `force*length`. The common physical normalization is
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Every member has rotational-stiffness units `force*length`. For an otherwise valid
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element, an empty `R+` is a deterministic numerical-validation failure. Define
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$$
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D_{iso}=\frac{Et^3}{12(1-\nu^2)},
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\qquad
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\boxed{\rho_{d,I}=\frac{k_{d,I}}{D_{iso}}}.
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\boxed{k_{ref}=\min\mathcal R_+,\qquad k_d=10^{-3}k_{ref}},
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$$
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`rho_d,I` is dimensionless and is the only common coordinate for comparing drilling
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families. For any candidate `c` written as
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and use the same positive scalar at all four local drilling coordinates:
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$$
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k_{d,I}^{(c)}=\alpha_d^{(c)}k_{ref,I}^{(c)},
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\boxed{\mathbf K_d^l=k_d\mathbf I_4}.
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$$
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the candidate-specific conversion is
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Translational diagonals have units `force/length` and shall never enter `R+`.
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Off-diagonal entries, nonpositive entries, and nonfinite entries also do not enter
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the minimum. The fixed coefficient is a project numerical-stability choice informed
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by the thesis rule; it is not a physical constitutive parameter, an Abaqus algorithm,
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or a claim of coefficient optimality.
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$$
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\boxed{
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\rho_{d,I}^{(c)}=\alpha_d^{(c)}
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\frac{k_{ref,I}^{(c)}}{D_{iso}},
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\qquad
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\alpha_{d,I}^{eq,(c)}=\rho_{d,I}^{(c)}
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\frac{D_{iso}}{k_{ref,I}^{(c)}}.}
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$$
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The second expression is the nodewise equivalent coefficient for a target `rho_d,I`.
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A single actual candidate coefficient may therefore generate a range of `rho_d,I`; that
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entire range is part of the calibration evidence. The dimensionally compatible
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candidate distributions carried from research are:
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1. transverse-shear/area transition family
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$$
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k_{ref,I}^{(A)}=
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\frac{GtA_{eI}}{1+qA_{eI}/t^2},
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\qquad q=2.5\times10^{-5},
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$$
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where
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$$
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A_{eI}=\int_{A_e}N_I\,dA
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\approx\sum_{g=1}^{4}N_I(\xi_g,\eta_g)
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\|\mathbf A_\xi\times\mathbf A_\eta\|_g w_g;
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$$
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2. isotropic bending rigidity
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$$
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k_{ref}^{(B)}=D_{iso},
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\qquad
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\rho_{d,I}^{(B)}=\alpha_d^{(B)};
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$$
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3. a documented positive statistic formed only from the physical rotational block
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of `K_20`, whose entries all have `force*length` units, converted by the same
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`k_ref/D_iso` ratio. A raw statistic is not comparable until this conversion is
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reported.
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The first two candidate scales differ sharply in the thin-shell limit:
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$$
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\boxed{\displaystyle \lim_{A_{eI}/t^2\to\infty}
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k_{ref,I}^{(A)}/D_{iso}=6(1-\nu)/q}.
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$$
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For `nu=0.3` and `q=2.5e-5`, this ratio is `168000`. Consequently the same raw
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coefficient, including `10^-3`, cannot represent the same small drilling stiffness
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for candidates A and B.
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The thesis rule `10^-3 min(all K_ii)` is not admissible because it can mix
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translational `force/length` and rotational `force*length` diagonals. A sweep must
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instead expand logarithmically in actual `rho_d,I` until it brackets both:
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1. a low-side scaled-rank/conditioning or factorization failure; and
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2. a high-side physical `U/N/M/Q` contamination boundary.
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A nominal value may be proposed only as the smallest point in a stable plateau, with
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the adjacent lower and higher decades and separate physical/drilling energies
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reported. The reference family, plateau, nominal value, and response/energy bounds
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remain `needs-numerical-calibration`; no common `10^-3` center is retained.
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There is no `rho_d`, coefficient sweep, stable-plateau selection, conditioning
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calibration, artificial-energy ratio, or drilling-specific output contract in this
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feature. Verification checks only the exact selection rule, dimensions, symmetry,
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positivity, four-mode regularization, deterministic repeatability, and separation
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from physical recovery.
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### 12.3 Stabilized 24-DOF matrix
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@@ -963,13 +845,11 @@ Mass and damping matrices are `N/A` for this linear-static feature.
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For a valid free isolated element, the expected physical rank is 14. Embedding it in
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24 coordinates creates the six physical rigid modes plus four drilling null modes.
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Four positive independent `k_d,I` values should remove only those drilling modes,
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The positive uniform `k_d` block should remove only those drilling modes,
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giving expected stabilized rank 18 and nullity 6. These are verification targets,
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not substitutes for the scaled singular-value/rank study defined in Section 12.5.
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The exact-arithmetic rank statement is independent of the calibrated numerical-rank
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threshold.
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not substitutes for the normalized rigid-action checks defined in Section 17.1.
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### 12.4 Energy split
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### 12.4 Energy identity
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The element energies are
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@@ -987,10 +867,9 @@ E_{drill}^e=\frac12\mathbf q_g^T
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=\frac12\boldsymbol\gamma^T\mathbf K_d^l\boldsymbol\gamma}.
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$$
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Both have units `force*length` and are aggregated separately in stable source order.
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The ratio `E_drill/E_phys` is reported only when mathematically classifiable. If
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`E_phys` is zero or near zero, the two energies are reported explicitly; no arbitrary
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denominator clamp is used. The warning ratio remains open.
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Both have units `force*length`. `E_drill` is the internal quadratic identity associated
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with `K_drill`; it is not a physical shell energy and is not emitted as a required
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result. No drilling-energy ratio or warning threshold is defined.
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### 12.5 DOF scaling for rank and conditioning evidence
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@@ -1032,10 +911,10 @@ $$
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\widehat{\mathbf K}_{ff}=\mathbf S_f^T\mathbf K_{ff}\mathbf S_f.
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$$
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Global condition and numerical-rank evidence uses `K_hat_ff`; a valid `0 x 0 Kff`
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Optional global condition and numerical-rank diagnostics use `K_hat_ff`; a valid `0 x 0 Kff`
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case is classified separately and is not reported as singular. Numerical
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rank/condition thresholds remain calibration decisions, but no raw mixed-unit
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matrix may be used to choose them.
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condition calibration is not an implementation gate, and no raw mixed-unit matrix
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may be used for any reported spectrum or condition estimate.
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## 13. Numerical integration
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@@ -1501,7 +1380,7 @@ for each shell element in stable source order:
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for each shell source node in stable source order:
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gather incident candidates in stable element order
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reject any nonpositive pairwise incident-normal dot product before averaging
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reject degenerate or too-sharp incident normals
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reject nonfinite or zero incident normals and averaged vectors
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d_I = normalize(sum(A_e * n_e))
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select least-aligned global axis with deterministic tie break
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construct right-handed (a_I, b_I, d_I)
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@@ -1515,7 +1394,7 @@ build T, T_p, T_d
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initialize K20[20,20] = 0
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evaluate the complete center/Gauss/tying/recovery geometry inventory
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validate pointwise J, j_s, a_g, c_d and aggregate r_J, theta_w
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validate finite nonzero surface area and finite positive J at every required location
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evaluate and validate four midsurface tying locations
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for each 2x2 midsurface Gauss location in fixed order:
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construct and validate local frame (e1,e2,e3)
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@@ -1530,20 +1409,21 @@ for each 2x2 midsurface Gauss location in fixed order:
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check K20 finite and symmetric within approved normalized tolerance
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Kphys24 = T_p^T * K20 * T_p
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construct positive Kd_local and report every k_d,I through rho_d,I = k_d,I/D_iso
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collect positive finite tangent-rotation diagonals R+ from K20
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require R+ nonempty; k_d = 1e-3 * min(R+); Kd_local = k_d * I4
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Kdrill24 = T_d^T * Kd_local * T_d
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Ke24 = Kphys24 + Kdrill24
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form S20, S24, Khat20, and Khat_e for rank/conditioning evidence only
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form S20, S24, Khat20, and Khat_e for normalized algebraic evidence only
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fint24 = Ke24 * q_g
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residual24 = fint24 - f_CLOAD
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return matrices, residual, transforms, frames, and separate energy operators
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return matrices, residual, transforms, and frames
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```
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### 16.3 Global linear-static lifecycle
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```text
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assemble all Ke24 contributions with stable element-local COO ordering
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form model-length DOF scaling and Khat_ff for global rank evidence only
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form model-length DOF scaling and Khat_ff for optional normalized diagnostics only
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partition full K into Kff, Kfc, Kcf, Kcc in stable free/constrained order
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factorize Kff before load assembly
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assemble and deterministically aggregate nodal CLOAD
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@@ -1551,7 +1431,7 @@ accept an exact-zero nodal moment separately; otherwise require rho_M <= 1e-12
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solve Kff * df = Ff - Kfc * dc
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reconstruct full displacement d
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compute full residual r = K*d - F
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recover shell rows and physical/drilling energies in stable source order
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recover shell rows and physical shell energy in stable source order
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validate complete finite candidate state/output, then commit
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```
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@@ -1565,7 +1445,7 @@ for each element and each 2x2 midsurface location in fixed order:
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attach exact natural coordinates, section position, frame, and source identity
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recover nodal global U/UR and full-residual RF/RM
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compute E_physical and E_drill separately; never clamp a near-zero denominator
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compute required physical shell energy; emit no drilling-specific result
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```
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### 16.5 Future nonlinear tangent check
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@@ -1587,14 +1467,15 @@ given an approved global Phi map, objective drill potential, and load work:
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- Shape-function partition of unity, Kronecker delta, and derivative sums.
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- Nodal and integration frames orthonormal and right-handed.
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- The complete `J/j_s/a_g/c_d/r_J/theta_w` inventory at center, Gauss, tying,
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and committed recovery points.
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- Finite nonzero surface area and finite positive `J` at every center, Gauss, tying,
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and committed recovery point.
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- Scaled `K20`, `Kphys24`, `Kdrill24`, and `Ke24` symmetry and spectrum.
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- Transformation work/energy invariance.
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- Physical rigid modes satisfy normalized scaled stiffness action.
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- Stabilized free-element nullity is exactly six; accepted non-rigid physical modes
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have positive physical energy.
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- Pure drill vectors have zero physical energy and positive drilling energy.
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- Pure drill vectors have zero physical-shell energy and positive action under the
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fixed numerical drilling block.
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- Consistent force/length unit rescaling leaves dimensionless decisions unchanged.
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For any nonzero scaled stiffness under test, the approved normalized checks are
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@@ -1634,41 +1515,35 @@ Independently verify:
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- pure twist and `K12/M12` convention;
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- zero strain/resultant/stress contribution from a pure drilling vector.
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### 17.3 Locking, distortion, and curved shells
|
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### 17.3 Nonblocking accuracy studies
|
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- Thin and thick plate/shell mesh and thickness sequences are required; one
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displacement on one mesh is insufficient.
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- Distorted and warped valid quadrilaterals must be swept through approved geometry
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measures.
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- Original MITC4 controls transverse-shear locking but can retain membrane locking
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in distorted curved meshes. This is a known limitation, not permission to add
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MITC4+.
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- Preferred nodal-load-compatible curved benchmarks are the pinched cylinder and
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NAFEMS LE3 hemispherical shell. Scordelis-Lo is admissible only after an equivalent
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nodal-load adaptation is documented.
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Thin/thick, distorted, warped, pinched-cylinder, NAFEMS LE3 and Scordelis-Lo studies
|
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remain useful for documenting the original MITC4 element's known shear- and
|
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membrane-locking limits. They are not required implementation-completion tests and
|
||||
do not authorize MITC4+ or an expanded input subset. `NR-O03` and `NR-O04` are
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explicitly removed from the acceptance scope.
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### 17.4 Drilling sensitivity
|
||||
### 17.4 Fixed drilling checks
|
||||
|
||||
For every candidate reference scale, convert candidate coefficients to the actual
|
||||
nodewise `rho_d,I` inventory. Expand a logarithmic sweep until both the low-side
|
||||
rank/conditioning failure and high-side physical-response contamination boundary
|
||||
are observed, and record:
|
||||
For representative valid element kernels, verify:
|
||||
|
||||
- free-element scaled rank and scaled constrained-system conditioning;
|
||||
- global `U` and physical `N/M/Q` sensitivity;
|
||||
- `E_phys` and `E_drill` without denominator clamping;
|
||||
- invariance under consistent unit conversion, thickness ratios, and mesh sizes.
|
||||
- `R+` contains only finite positive physical tangent-rotation diagonals;
|
||||
- `k_d=10^-3 min(R+)` and `K_d^l=k_d I4` exactly;
|
||||
- `K_drill^24` is symmetric and positive on each pure drilling coordinate;
|
||||
- four nonphysical drilling null modes are removed while the six physical rigid
|
||||
modes satisfy the normalized action test;
|
||||
- physical generalized strain, resultant and stress recovery is unchanged by a
|
||||
pure drilling vector.
|
||||
|
||||
Candidate runs are compared by overlapping actual `rho_d,I` ranges, never by equal
|
||||
raw `alpha_d`. The study must select the reference family, the smallest stable
|
||||
plateau value, its adjacent-decade sensitivity, and the energy warning criterion
|
||||
before Implementation Planning.
|
||||
No coefficient sweep, plateau, condition threshold, response-sensitivity criterion,
|
||||
or drilling-energy warning is part of this check.
|
||||
|
||||
### 17.5 Reference-comparison boundary
|
||||
|
||||
Abaqus comparisons block only on matched global `U1/U2/U3` rows under the approved
|
||||
mixed tolerance decided downstream. `UR1/UR2/UR3` is fully reported and may emit a
|
||||
deterministic nonblocking large-error warning, but it does not change pass/fail.
|
||||
Abaqus comparisons block only on matched global `U1/U2/U3` rows under
|
||||
`tolerance_c=1e-9+1e-6*reference_scale_c`, where `reference_scale_c` is the maximum
|
||||
absolute finite Abaqus value for the same component. `UR1/UR2/UR3` uses the same
|
||||
formula but an exceedance emits only a deterministic nonblocking warning.
|
||||
FESA `S4` and `S4R` inputs must produce the same internal numerical rows for identical
|
||||
supported models while preserving distinct source metadata. Abaqus S4 and S4R are
|
||||
not expected to be numerically identical on finite meshes.
|
||||
@@ -1686,16 +1561,15 @@ procedure.
|
||||
|
||||
| Risk | Consequence | Required control |
|
||||
| --- | --- | --- |
|
||||
| Transverse-shear locking | overly stiff thin-shell response | exact edge-midpoint MITC projection and thickness/mesh convergence |
|
||||
| Membrane locking on distorted curved meshes | slow or nonuniform convergence | distortion/curvature sweeps; document original MITC4 limitation |
|
||||
| Transverse-shear locking | overly stiff thin-shell response | exact edge-midpoint MITC projection and patch/reference evidence; broader convergence is a known limitation study |
|
||||
| Membrane locking on distorted curved meshes | slow or nonuniform convergence | document original MITC4 limitation; optional later studies do not alter the current gate |
|
||||
| Volumetric locking | N/A for the approved plane-stress shell contract | do not infer a three-dimensional incompressible formulation |
|
||||
| Wrong tying pair or engineering-shear factor | swapped/incorrect shear and loss of patch consistency | component-level tying and patch tests |
|
||||
| Reversed or degenerate Jacobian | invalid basis, sign, or energy | common location inventory with `J/j_s/a_g/c_d/r_J/theta_w` |
|
||||
| Reversed or degenerate Jacobian | invalid basis, sign, or energy | finite nonzero surface area and finite positive `J` at every required location |
|
||||
| Discontinuous shared director | artificial coupling or undefined frame | reject; require duplicate nodes at folds |
|
||||
| Fixed-axis tangent singularity | nondeterministic rotation transform | least-aligned global-axis construction |
|
||||
| Drilling coefficient too small | rank/conditioning failure | rank and conditioning sensitivity sweep |
|
||||
| Drilling coefficient too large | contaminated displacement/resultant | physical-output and separate-energy sensitivity sweep |
|
||||
| Mixed-unit drilling or spectrum scale | unit-dependent stabilization/rank | use `rho_d,I` and `S^T K S`; prohibit raw mixed-unit comparison |
|
||||
| Invalid drilling reference inventory | absent or nonpositive numerical regularization | require nonempty finite positive physical rotational diagonals and fail deterministically otherwise |
|
||||
| Mixed-unit drilling scale | unit-dependent stabilization | exclude every translational diagonal; use only the physical tangent-rotation block |
|
||||
| Misconstructed rigid test | false drill energy in a physical mode | use rigid translation plus tangent director change with `gamma=0` |
|
||||
| Recovery/stiffness mismatch | inconsistent energy and section output | same frames, tying, material, and thickness rule |
|
||||
| Location averaging | hidden sign/identity error | preserve exact location rows; no nodal extrapolation |
|
||||
@@ -1748,25 +1622,25 @@ research brief remain the project source of truth.
|
||||
| Requirement group | Formulation coverage | Remaining owner |
|
||||
| --- | --- | --- |
|
||||
| `001-004`, `030`, `037` | linear-static boundary; S4/S4R one FESA path, source identity distinct | I/O, planning |
|
||||
| `005`, `031-038` | 24 global DOFs; 20 physical plus four drill coordinates; `rho_d,I`, scaled rank, energy | Numerical Review for drill calibration |
|
||||
| `005`, `031-038` | 24 global DOFs; 20 physical plus four drill coordinates; fixed positive rotational-diagonal stabilization | Numerical Review for formula consistency |
|
||||
| `006-010` | isotropic plane stress, one centered constant-thickness layer | I/O validation |
|
||||
| `011-016` | pairwise normals, deterministic averaging/frames, complete geometry measures | Numerical Review for calibrated thresholds |
|
||||
| `011-016` | pairwise orientation, deterministic averaging/frames, basic finite/positive geometry predicates | I/O validation |
|
||||
| `017-020` | global 24-DOF virtual work; `rho_M <= 1e-12`; distributed loads excluded | I/O diagnostic/schema |
|
||||
| `024-029` | deterministic element buffers, partitioned linear lifecycle, full-residual reaction | planning |
|
||||
| `039-048` | nodal/global and shell/local recovery inventory, units, identities, energy split | I/O schema |
|
||||
| `049-057` | scaled normalized invariants, patches, locking, geometry, curved shells, drilling, equilibrium | Numerical Review/reference/physics |
|
||||
| `058-064` | U blocking, UR warning-only comparison boundary | Numerical Review/reference model |
|
||||
| `065-072` | reference immutability and displacement-only evidence boundary acknowledged | reference model |
|
||||
| `039-048` | nodal/global and shell/local recovery inventory, units, identities, physical shell energy | I/O schema |
|
||||
| `049-057` | normalized invariants, patches, fixed drilling, declared references and equilibrium | Numerical Review/reference/physics |
|
||||
| `058-064` | exact B33 mixed tolerance; U blocking and UR warning-only | reference verification |
|
||||
| `065-072` | exact existing S4/S4R paths, immutability and displacement-only boundary | reference model |
|
||||
|
||||
### 20.1 Numerical Review revision traceability
|
||||
|
||||
The first review findings map to this revision as follows.
|
||||
|
||||
`NR-C01` maps to Sections 9.2-9.3, 16.2, and 17.1/17.3. The geometry measures
|
||||
are fixed while their thresholds still require calibration.
|
||||
`NR-C01` maps to Sections 9.2-9.3, 16.2, and 17.1/17.3. Basic point inventory and
|
||||
finite/positive predicates remain; `NR-O03`/`NR-O04` calibration is removed.
|
||||
|
||||
`NR-C02` maps to Sections 12.2 and 17.4. The common `rho_d,I` coordinate and
|
||||
candidate conversions are fixed while the stable plateau remains open.
|
||||
`NR-C02` maps to Sections 12.2 and 17.4. The project decision replaces candidate
|
||||
normalization and plateau work with the exact fixed rotational-diagonal rule.
|
||||
|
||||
`NR-C03` maps to Sections 12.3/12.5 and 17.1. Element/global DOF scaling is fixed
|
||||
while the numerical-rank threshold remains open.
|
||||
@@ -1781,53 +1655,45 @@ normalized algebraic metrics.
|
||||
|
||||
## 21. Open issues and downstream handoff
|
||||
|
||||
### 21.1 Blocking Numerical Review decisions
|
||||
### 21.1 Current numerical-review boundary
|
||||
|
||||
1. Select the dimensionally compatible drilling reference-scale family.
|
||||
2. Select the nodewise `rho_d,I` stable plateau, nominal value, scaled
|
||||
conditioning/rank acceptance, and physical-output contamination bound.
|
||||
3. Define classification and warning behavior for `E_drill/E_phys`, including the
|
||||
zero/near-zero physical-energy case.
|
||||
4. Approve `theta_smooth` after curved-mesh resolution sweeps; `20 degrees` is only
|
||||
the initial candidate.
|
||||
5. Calibrate thresholds for the fixed `J/j_s/a_g/c_d/r_J/theta_w` geometry
|
||||
inventory using valid distortion/warp and collapsed negative sequences.
|
||||
6. Jointly with Reference Model, approve the U mixed tolerance and nonblocking UR
|
||||
large-error warning threshold.
|
||||
|
||||
The first review already approved `rho_M <= 1e-12`, the normalized algebraic checks,
|
||||
the MITC tying/component signs, constitutive law, quadrature, and recovery signs.
|
||||
This revision is ready for Numerical Review rerun but not for Implementation
|
||||
Planning until the six remaining evidence-backed decisions are closed.
|
||||
No calibration decision remains open for the linear implementation. The first review
|
||||
approved `rho_M <= 1e-12`, the normalized algebraic checks, MITC tying/component signs,
|
||||
constitutive law, quadrature, and recovery signs. The approved policy fixes drilling
|
||||
and U/UR tolerance and removes drilling-energy calibration plus `NR-O03`/`NR-O04`.
|
||||
Numerical Review shall now check internal consistency and may not treat those removed
|
||||
items or an expanded reference portfolio as missing evidence.
|
||||
|
||||
### 21.2 I/O Definition handoff
|
||||
|
||||
- Preserve source `S4`/`S4R` separately from internal `FESA-MITC4`.
|
||||
- Define exact keyword subset, section/material resolution, and fail-closed
|
||||
diagnostics for director, folds, Jacobians, unsupported loads, and recovery;
|
||||
diagnostics for director orientation, basic topology/Jacobians, unsupported loads, and recovery;
|
||||
encode exact-zero nodal moment separately and enforce `rho_M <= 1e-12` without
|
||||
a denominator clamp.
|
||||
- Define exact HDF5 row schemas for global `U/UR`, `RF/RM`; four midsurface
|
||||
generalized-strain/resultant locations; bottom/middle/top stress positions; full
|
||||
residual/equilibrium; and separate energies.
|
||||
residual/equilibrium; and physical shell energy. Do not add drilling-specific datasets.
|
||||
- Preserve local frame and natural-coordinate identity without location averaging.
|
||||
|
||||
### 21.3 Reference Model handoff
|
||||
|
||||
- Use at least one S4 and one S4R source artifact, but compare formulation-independent
|
||||
global displacement evidence rather than claiming element equivalence.
|
||||
- Prioritize pinched cylinder and NAFEMS LE3 models compatible with nodal loads and
|
||||
approved BC semantics.
|
||||
- Propose the mixed U tolerance and nonblocking UR warning threshold.
|
||||
- Record the existing `reference/shell/` S4 and `reference/shellR/` S4R input and
|
||||
displacement CSV paths, but compare only formulation-independent global displacement
|
||||
evidence rather than claiming element equivalence.
|
||||
- Use the exact B33 mixed tolerance; do not add administrative metadata or portfolio gates.
|
||||
- Do not create, repair, rename, or run reference artifacts during this formulation
|
||||
gate.
|
||||
|
||||
### 21.4 Implementation Planning handoff
|
||||
|
||||
- Do not begin until Numerical Review closes Section 21.1.
|
||||
- Begin after the Numerical Review, I/O contract, and lightweight Reference Model
|
||||
inventory agree with this formulation.
|
||||
- Translate the deterministic preprocessing, 24-to-20 transform, tying projection,
|
||||
physical/drill split, quadrature, recovery, and invariant portfolio into
|
||||
`RED -> GREEN -> VERIFY` tests before production changes.
|
||||
fixed physical/drill split, quadrature, recovery, and required invariants into
|
||||
Harness Step drafts with `RED -> GREEN -> VERIFY` tests before production changes.
|
||||
- Obtain user approval of the multi-Step draft before creating phase-planning files;
|
||||
Harness execution requires a separate explicit user request.
|
||||
- Keep future nonlinear state and tangent out of the current linear-static plan.
|
||||
|
||||
### 21.5 Future nonlinear formulation handoff
|
||||
|
||||
@@ -6,12 +6,11 @@
|
||||
- title: `Linear Static MITC4 Shell`
|
||||
- status: `approved`
|
||||
- owner_agent: `requirement-agent`
|
||||
- date: `2026-08-11`
|
||||
- date: `2026-08-12`
|
||||
- approval_basis: 사용자와 확정한 선형 정적 범위, `S4`/`S4R` 매핑, 6자유도 외부 계약, drilling 안정화, 자동 director 생성, 결과 및 검증 계약
|
||||
- current_product_state: `requirements-approved-not-implemented`
|
||||
- formulation_alignment: `docs/formulations/mitc4-shell-formulation.md`는 선행 draft이며 이 baseline의 6자유도 및 drilling 계약에 맞춘 후속 개정이 필요함
|
||||
- declared_reference_candidate: 사용자가 `reference/shell/`에 Abaqus `S4R` 모델을 추가했다고 `2026-08-11`에 선언함
|
||||
- reference_inventory_state: 요구조건 작성 시점의 workspace에서는 `reference/shell/`이 관찰되지 않아 exact artifact inventory는 `needs-reference-artifacts`로 유지함
|
||||
- formulation_alignment: `docs/formulations/mitc4-shell-formulation.md`는 이 baseline의 6자유도 및 고정 drilling 안정화 계약과 정렬함
|
||||
- reference_inventory_state: `reference/shell/`의 S4와 `reference/shellR/`의 S4R input/displacement CSV를 기존 경로와 이름 그대로 사용함
|
||||
|
||||
## Purpose
|
||||
|
||||
@@ -51,7 +50,7 @@ Formulation, Numerical Review, I/O, Reference Model, Implementation Planning 및
|
||||
- Abaqus source element type `S4`와 `S4R`의 동일한 FESA MITC4 매핑
|
||||
- 절점당 전역 자유도 `[UX, UY, UZ, URX, URY, URZ]`
|
||||
- 3개 병진과 director 접평면 회전 2개로 구성된 물리 MITC4 kernel
|
||||
- 비물리 local drilling 회전 1개에 대한 작은 scale-aware 수치 안정화
|
||||
- 비물리 local drilling 회전 1개에 대한 고정 수치 안정화
|
||||
- 막, 굽힘, 횡전단 및 이들의 coupling
|
||||
- 단일층, 균질 등방성 선형 탄성
|
||||
- element set별 일정한 양의 두께와 하나의 material을 갖는 `*SHELL SECTION`
|
||||
@@ -60,7 +59,7 @@ Formulation, Numerical Review, I/O, Reference Model, Implementation Planning 및
|
||||
- DOF 1~6의 nodal `*BOUNDARY`와 nodal `*CLOAD`
|
||||
- deterministic assembly와 기존 linear-static partition/factorization/substitution lifecycle
|
||||
- HDF5 nodal displacement/reaction, shell generalized strain/resultant, in-plane stress, residual 및 energy output
|
||||
- element invariant, patch, locking, distortion, curved-shell, reference 및 physics verification
|
||||
- element invariant, patch, 현재 S4/S4R displacement reference 및 physics verification
|
||||
|
||||
## Out Of Scope
|
||||
|
||||
@@ -115,9 +114,9 @@ Formulation, Numerical Review, I/O, Reference Model, Implementation Planning 및
|
||||
- **FESA-REQ-LSMITC4-011** — The initial nodal director shall be a dimensionless unit vector in the positive thickness direction; scalar thickness shall remain a separate property and shall not be encoded in the director magnitude.
|
||||
- **FESA-REQ-LSMITC4-012** — The positive element normal candidate shall be derived deterministically from the source node order and midsurface covariant tangent cross product.
|
||||
- **FESA-REQ-LSMITC4-013** — At a smooth shared node, consistently oriented incident element normal candidates shall be combined by deterministic area-weighted averaging and normalized to form the common nodal director.
|
||||
- **FESA-REQ-LSMITC4-014** — Zero/near-zero normal candidates, a zero/near-zero averaged director, opposing incident orientations, and a fold sharper than the approved smooth-patch criterion shall fail model validation.
|
||||
- **FESA-REQ-LSMITC4-014** — Nonfinite or zero normal candidates, a nonfinite or zero averaged director, and opposing incident orientations shall fail model validation; this feature does not introduce a calibrated smooth-patch angle.
|
||||
- **FESA-REQ-LSMITC4-015** — A physical fold or hinge shall be represented with duplicated source nodes so each smooth shell patch owns a separate director; the solver shall not silently average a discontinuous director field.
|
||||
- **FESA-REQ-LSMITC4-016** — Element geometry validation shall reject duplicate nodes, self-intersection, nonfinite coordinates, degenerate area, and nonpositive or near-singular Jacobians at every formulation-required Gauss and tying location.
|
||||
- **FESA-REQ-LSMITC4-016** — Element geometry validation shall reject duplicate nodes, self-intersection, nonfinite coordinates, zero area, and nonpositive or nonfinite Jacobians at every formulation-required Gauss and tying location; this feature does not introduce calibrated distortion or warp thresholds.
|
||||
- **FESA-REQ-LSMITC4-017** — The solver shall support nodal `*BOUNDARY` targets resolved by source node label or node set for global DOFs 1 through 6, including existing zero and nonzero prescribed-displacement semantics.
|
||||
- **FESA-REQ-LSMITC4-018** — The solver shall support nodal `*CLOAD` forces on DOFs 1 through 3 and nodal moments on DOFs 4 through 6 after deterministic aggregation in global coordinates.
|
||||
- **FESA-REQ-LSMITC4-019** — The aggregated nodal moment component parallel to the approved nodal director shall be rejected as `unsupported-drilling-load`; a drilling-direction moment shall not be carried only by numerical stabilization.
|
||||
@@ -140,10 +139,10 @@ Formulation, Numerical Review, I/O, Reference Model, Implementation Planning 및
|
||||
|
||||
- **FESA-REQ-LSMITC4-031** — The physical MITC4 kernel shall use three translations and two director-tangent rotations per node and shall not treat the drilling rotation as a physical strain variable.
|
||||
- **FESA-REQ-LSMITC4-032** — The six-DOF element embedding shall transform global nodal rotations into two director-tangent components and one director-parallel drilling component using deterministic right-handed orthonormal frames.
|
||||
- **FESA-REQ-LSMITC4-033** — The drilling contribution shall be symmetric, positive, scale-aware, sufficiently small to remain numerical, and sufficient to remove the nonphysical drilling null modes of otherwise valid models.
|
||||
- **FESA-REQ-LSMITC4-034** — The drilling scale shall be derived from dimensionally compatible physical rotational stiffness; the implementation shall not apply `10^-3 * min(all Kii)` across mixed translational and rotational diagonal entries without an approved dimensional derivation.
|
||||
- **FESA-REQ-LSMITC4-035** — Drilling stabilization shall not contribute to physical membrane, bending or transverse-shear generalized strain/resultant or section-point stress; its energy shall be recovered separately.
|
||||
- **FESA-REQ-LSMITC4-036** — Exact drilling reference scale, dimensionless coefficient and acceptable artificial-energy ratio shall be approved through Research and Numerical Review before Implementation Planning; no implementation-selected default may close this decision silently.
|
||||
- **FESA-REQ-LSMITC4-033** — The drilling contribution shall be a symmetric positive numerical stabilization of the four director-parallel coordinates and shall not define a physical drilling strain or load channel.
|
||||
- **FESA-REQ-LSMITC4-034** — Let `R+` be the finite strictly positive diagonal entries of the physical local stiffness belonging only to the eight director-tangent rotational DOFs. The element shall use `k_ref=min(R+)`, `k_d=10^-3*k_ref`, `K_drill_local=k_d I4`, and the documented drilling transformation `T_d`; translational diagonals shall never enter `R+`.
|
||||
- **FESA-REQ-LSMITC4-035** — Drilling stabilization shall not contribute to physical membrane, bending or transverse-shear generalized strain/resultant, section-point stress, or separately reported result quantities.
|
||||
- **FESA-REQ-LSMITC4-036** — An otherwise accepted element with no finite strictly positive entry in `R+` shall fail numerical validation deterministically; coefficient sweeps, plateau selection, conditioning calibration, artificial-energy ratios, and drilling-specific result datasets are outside this feature.
|
||||
- **FESA-REQ-LSMITC4-037** — Source `S4R` shall not select reduced integration or Abaqus hourglass control; all accepted `S4` and `S4R` inputs shall use the single quadrature and MITC tying contract approved by the FESA formulation.
|
||||
- **FESA-REQ-LSMITC4-038** — The stabilized element shall retain exactly six physical rigid-body modes within the approved normalized tolerance, preserve stiffness symmetry and coordinate-transformation energy, and have positive energy for every accepted non-rigid physical deformation mode.
|
||||
|
||||
@@ -156,7 +155,7 @@ Formulation, Numerical Review, I/O, Reference Model, Implementation Planning 및
|
||||
- **FESA-REQ-LSMITC4-043** — The same shell locations shall output local section resultant components `[N11,N22,N12,M11,M22,M12,Q13,Q23]`, where `N` and `Q` have dimension `force/length` and `M` has dimension `force` as moment resultant per unit edge length.
|
||||
- **FESA-REQ-LSMITC4-044** — Each required shell location shall output local in-plane stress `[S11,S22,S12]` at bottom, middle and top section positions with dimension `force/length^2`; `S33` shall be documented as the plane-stress assumption and `S13/S23` point stress shall not be emitted.
|
||||
- **FESA-REQ-LSMITC4-045** — Result rows shall identify source element, integration/tying or recovery location, natural coordinates, section position, local frame/director and component order without averaging mismatched locations.
|
||||
- **FESA-REQ-LSMITC4-046** — The output shall include free-DOF residual evidence, total force/moment equilibrium metrics, physical strain energy and drilling stabilization energy with dimension `force*length` and deterministic aggregation order.
|
||||
- **FESA-REQ-LSMITC4-046** — The output shall include free-DOF residual evidence, total force/moment equilibrium metrics and physical shell strain energy with dimension `force*length` and deterministic aggregation order; no drilling-specific stiffness, ratio or energy dataset is required.
|
||||
- **FESA-REQ-LSMITC4-047** — Abaqus output requests shall neither suppress nor expand the mandatory HDF5 quantity inventory; any deterministic FESA CSV projection shall remain a debugging/review view rather than official solver output.
|
||||
- **FESA-REQ-LSMITC4-048** — Nonfinite recovery values, inconsistent component/location inventory or failure to finalize required HDF5 rows shall fail the analysis without committing a partial successful state.
|
||||
|
||||
@@ -166,10 +165,10 @@ Formulation, Numerical Review, I/O, Reference Model, Implementation Planning 및
|
||||
- **FESA-REQ-LSMITC4-050** — Element invariant tests shall cover frame orthonormality/handedness, Jacobian sign, stiffness symmetry, coordinate-transformation energy invariance, six physical rigid modes, deformation-mode positivity and deterministic repeatability.
|
||||
- **FESA-REQ-LSMITC4-051** — Normalized algebraic acceptance shall use `1e-12` for symmetry, frame orthonormality and transformation-energy invariance and `1e-10` for rigid-mode action, linear-system residual and global equilibrium unless Numerical Review approves and documents an evidence-backed scale-aware replacement before Implementation Planning.
|
||||
- **FESA-REQ-LSMITC4-052** — Patch verification shall independently cover constant membrane strain/stress, pure bending, transverse shear and twist, including sign and component-order checks for generalized strain, resultant and recovered in-plane stress.
|
||||
- **FESA-REQ-LSMITC4-053** — Locking/convergence verification shall include thin- and thick-shell or plate sequences over documented thickness ratios and mesh refinements and shall demonstrate the approved MITC4 transverse-shear behavior rather than judge one displacement on one mesh.
|
||||
- **FESA-REQ-LSMITC4-054** — Geometry verification shall include planar, smoothly curved, distorted and warped valid elements plus negative tests for degenerate, inverted, self-intersecting, opposing-normal and sharp-fold topologies.
|
||||
- **FESA-REQ-LSMITC4-055** — Curved-shell verification shall include at least one nodal-load-compatible pinched-cylinder, hemispherical-shell or equivalently justified benchmark; Scordelis-Lo may be included only with documented equivalent nodal loading inside the approved input subset.
|
||||
- **FESA-REQ-LSMITC4-056** — Drilling verification shall vary the approved stabilization coefficient around its nominal value, confirm stable equation rank, report physical displacement/resultant sensitivity and enforce the approved drilling-to-physical energy warning criterion.
|
||||
- **FESA-REQ-LSMITC4-053** — The implementation shall pass the formulation-defined element invariants and patch/manufactured tests plus the two declared S4/S4R displacement reference cases; an expanded locking, distortion or curved-shell benchmark portfolio is not an implementation-completion gate for this feature.
|
||||
- **FESA-REQ-LSMITC4-054** — Geometry validation tests shall cover the exact accepted/rejected conditions defined by the formulation and I/O contract; `NR-O03` smooth-director calibration and `NR-O04` distortion/warp threshold sweeps are not required tests.
|
||||
- **FESA-REQ-LSMITC4-055** — Additional pinched-cylinder, hemispherical-shell, Scordelis-Lo or mesh-convergence studies may be added later as nonblocking research or release evidence, but are not required for Implementation Planning or feature completion.
|
||||
- **FESA-REQ-LSMITC4-056** — Drilling verification shall check the fixed formula in Requirement 034, symmetry, positivity, deterministic assembly, removal of the four nonphysical local drilling null modes, and exclusion from physical recovery; coefficient sweeps and drilling-energy checks are not required.
|
||||
- **FESA-REQ-LSMITC4-057** — Physics verification shall check load/reaction balance, global moment balance, displacement direction, symmetry, energy positivity, result sign and consistency between assembled residual and recovered shell resultants.
|
||||
|
||||
## Verification Quantities
|
||||
@@ -180,31 +179,29 @@ Formulation, Numerical Review, I/O, Reference Model, Implementation Planning 및
|
||||
- shell_section_resultant: required, local `N/M/Q` eight components at documented locations
|
||||
- stress: required, local bottom/middle/top `[S11,S22,S12]`; Abaqus equality comparison N/A
|
||||
- residual: required, free-DOF and normalized global equilibrium evidence
|
||||
- energy: required, separate physical strain and drilling stabilization energies
|
||||
- energy: required for the physical shell strain energy; drilling-specific energy output is not required
|
||||
- modes_and_invariants: required, six physical rigid modes, symmetry, transformation invariance and positive deformation energy
|
||||
|
||||
## Tolerance Policy
|
||||
|
||||
- **FESA-REQ-LSMITC4-058** — Abaqus reference pass/fail shall apply only to matched global `U1/U2/U3` rows using `tolerance_c = absolute_floor_c + relative_coefficient_c * reference_scale_c`.
|
||||
- **FESA-REQ-LSMITC4-058** — Abaqus reference pass/fail shall apply only to matched global `U1/U2/U3` rows using `tolerance_c = 1e-9 + 1e-6 * reference_scale_c`, exactly reusing the approved B33 displacement rule.
|
||||
- **FESA-REQ-LSMITC4-059** — `reference_scale_c` shall be computed only from finite Abaqus values in the same model, step/frame, quantity and component group; reference values shall not be zero-clamped and row-specific relative denominators shall not replace the group scale.
|
||||
- **FESA-REQ-LSMITC4-060** — MITC4 displacement absolute floors and relative coefficients shall not silently inherit the B33 numerical values; Reference Model shall propose dimensioned floors and coefficients from benchmark evidence and Numerical Review shall approve them before reference comparison implementation.
|
||||
- **FESA-REQ-LSMITC4-061** — Global `UR1/UR2/UR3` rows shall be compared and fully reported but shall not affect pass/fail; errors beyond the approved large-error threshold shall emit deterministic nonblocking warnings and remain visible in known limitations.
|
||||
- **FESA-REQ-LSMITC4-062** — The UR large-error threshold and drilling-energy warning ratio are `needs-downstream-decision` owned jointly by Reference Model and Numerical Review and shall be fixed before Implementation Planning.
|
||||
- **FESA-REQ-LSMITC4-060** — The `1e-9` absolute floor is expressed in the model's user-consistent length unit for U; no additional MITC4 tolerance calibration is required.
|
||||
- **FESA-REQ-LSMITC4-061** — Global `UR1/UR2/UR3` rows shall use the same component-scale formula as Requirement 058 and shall be fully reported; an exceedance emits a deterministic nonblocking warning and never changes pass/fail.
|
||||
- **FESA-REQ-LSMITC4-062** — The `1e-9` UR floor is dimensionless. No separate UR large-error or drilling-energy threshold is required.
|
||||
- **FESA-REQ-LSMITC4-063** — Missing, extra, duplicate, nonfinite, schema-mismatched or source-identity-mismatched rows shall fail artifact/schema validation before numeric tolerance evaluation for both U and UR inventories.
|
||||
- **FESA-REQ-LSMITC4-064** — The comparison report shall record each U/UR row decision, maximum absolute error, component-scale normalized error, RMS error, vector-norm error and worst source row/component; nonblocking UR warnings shall not be omitted from an otherwise passing report.
|
||||
|
||||
## Reference Artifact Requirements
|
||||
|
||||
The user-declared first candidate is `reference/shell/` and is said to contain an Abaqus
|
||||
`S4R` model. At requirements-authoring time that directory was not visible in the shared
|
||||
workspace, so no exact filename, schema, units, generator, step/frame or row inventory is
|
||||
asserted here. The bundle shall remain read-only when it becomes observable.
|
||||
The approved lightweight inventory uses the existing S4 and S4R paths below. These files
|
||||
remain read-only; their names are identities, not canonical/legacy-policy decisions.
|
||||
|
||||
- **FESA-REQ-LSMITC4-065** — Reference Model shall inventory `reference/shell/` without creating, renaming, rewriting or repairing files and shall classify a missing/unobservable candidate as `needs-reference-artifacts` rather than fabricate its content.
|
||||
- **FESA-REQ-LSMITC4-066** — A usable new reference bundle shall contain `model.inp` and `<model-id>_displacements.csv`, or shall receive an explicitly approved legacy-alias contract that records its exact existing filenames without rename; `metadata.json` is optional and its absence shall not make the bundle unusable.
|
||||
- **FESA-REQ-LSMITC4-067** — The approved Reference Model Contract shall record Abaqus generator/version, creation provenance, source element type, model/step/frame identity, user unit system, global coordinate convention, section/material/thickness data, CSV schema and tolerance policy; if `metadata.json` exists, it shall be inventoried read-only and checked against that contract and the stored artifacts.
|
||||
- **FESA-REQ-LSMITC4-068** — Artifact validation shall confirm an approved single `*STEP, *STATIC` model, expected `S4` or `S4R` source type, supported keyword subset, unique finite displacement rows and exact source-node/component identity before comparison.
|
||||
- **FESA-REQ-LSMITC4-069** — End-to-end mapping evidence shall cover at least one `S4` input and at least one `S4R` input; the declared `reference/shell/` S4R model may satisfy only the S4R side after inventory validation, so separate S4 evidence remains required.
|
||||
- **FESA-REQ-LSMITC4-065** — The S4 case shall use `reference/shell/shell.inp` and `reference/shell/shell displacements.csv` without creating, renaming, rewriting or repairing either file.
|
||||
- **FESA-REQ-LSMITC4-066** — The S4R case shall use `reference/shellR/shellR.inp` and `reference/shellR/shellR displacements.csv` without creating, renaming, rewriting or repairing either file.
|
||||
- **FESA-REQ-LSMITC4-067** — Reference readiness requires only the declared input and required displacement CSV, FESA `results.h5`, deterministic source-node/component mapping, and Requirements 058-063 tolerance/precheck rules. README, `metadata.json`, canonical naming, provenance, Abaqus version, duplicated model semantics, and a schema version are not required gates; a present `metadata.json` is optional read-only context.
|
||||
- **FESA-REQ-LSMITC4-068** — Artifact validation shall require unique finite displacement rows and deterministic source-node/component identity before comparison; it shall not attempt to establish Abaqus internal formulation equivalence.
|
||||
- **FESA-REQ-LSMITC4-069** — The two declared cases satisfy the required source-label coverage: `reference/shell/` covers S4 and `reference/shellR/` covers S4R. No expanded reference portfolio is required for this feature.
|
||||
- **FESA-REQ-LSMITC4-070** — Reference verification shall compare FESA HDF5 global nodal displacement rows directly against Abaqus displacement CSV rows by model, step/frame, source node and component identity; a FESA-generated CSV view shall not become the authoritative comparison source.
|
||||
- **FESA-REQ-LSMITC4-071** — Abaqus reaction, stress, strain and shell force/moment output may be retained as review evidence if present but shall not change the approved `U1/U2/U3` pass/fail boundary or become an undeclared equality gate.
|
||||
- **FESA-REQ-LSMITC4-072** — FESA agents shall not execute Abaqus or another reference solver and shall not generate, modify, restore or normalize reference artifacts during requirements, research, formulation, implementation or verification unless a later phase explicitly authorizes that operation.
|
||||
@@ -221,72 +218,61 @@ without gaps or overlap.
|
||||
| `002-004` | `S4`/`S4R` mapping and identity | input/model | User approval | must | Parser/semantic/HDF5 metadata tests | Both source types map to one MITC4 path and preserve distinct source metadata and four-node identity | Exact element/type identity | I/O Definition; Implementation Planning | approved |
|
||||
| `005` | Six global nodal DOFs | model | User approval; project DOF convention | must | DofManager and HDF5 schema tests | Exact component order and no distributed equation ownership | Exact ordering | Formulation; I/O Definition; Implementation Planning | approved |
|
||||
| `006-010` | Isotropic material and single-layer section | input/model | User approval | must | Parser, mapping and validation tests | Valid `E,nu,t` resolve once per element; excluded section/material meanings fail | Exact inequalities; finite values | Research; I/O Definition; Implementation Planning | approved |
|
||||
| `011-016` | Initial director and geometry validity | geometry | User approval; MITC director kinematics | must | Geometry/unit/property-based tests | Deterministic unit directors for smooth valid meshes; every invalid topology fails | Smooth-angle and scale-aware Jacobian thresholds: Research + Numerical Review | Research; Formulation; Numerical Review; I/O Definition | approved-with-downstream-decision |
|
||||
| `017-020` | Boundary and nodal-load subset | input/load | User approval | must | Parser/semantic/load tests | Global BC/CLOAD works; director-parallel moment and distributed loads fail | Drilling projection threshold: Numerical Review + I/O Definition | Formulation; I/O Definition; Implementation Planning | approved-with-downstream-decision |
|
||||
| `011-016` | Initial director and geometry validity | geometry | User approval; MITC director kinematics | must | Geometry/unit/property-based tests | Deterministic unit directors for supported valid meshes; explicitly invalid mappings fail | Exact formulation/I/O predicates; no `NR-O03`/`NR-O04` calibration gate | Formulation; I/O Definition; Implementation Planning | approved |
|
||||
| `017-020` | Boundary and nodal-load subset | input/load | User approval | must | Parser/semantic/load tests | Global BC/CLOAD works; director-parallel moment and distributed loads fail | Exact-zero/projection rule from Formulation and I/O | Formulation; I/O Definition; Implementation Planning | approved |
|
||||
| `021-023` | Parser subset, wrappers and no-op policy | input | User approval; ADR-003/013/018 | must | Parser diagnostic and semantic identity tests | Only approved meanings affect Domain; excluded meanings fail closed | Exact keyword/diagnostic inventory | I/O Definition; Implementation Planning | approved |
|
||||
| `024-030` | Ownership, deterministic assembly and linear-static execution | architecture/execution | PRD; ADR-004/007/008/009/016/017 | must | Unit, orchestration and repeated-thread-count tests | Ownership boundaries, event order, residual reaction and deterministic bytes/rows match | `1e-12` deterministic numeric target where applicable | Numerical Review; Implementation Planning | approved |
|
||||
| `031-038` | 5-DOF physics embedded in 6-DOF with drilling stabilization | numerical boundary | User approval; MITC literature and thesis 6-DOF discussion | must | Formulation review, element invariant, rank and energy tests | Physical outputs exclude drilling; stable system retains six physical rigid modes | Scale/coefficient/energy ratio: Research + Numerical Review | Research; Formulation; Numerical Review | approved-with-downstream-decision |
|
||||
| `031-038` | 5-DOF physics embedded in 6-DOF with fixed drilling stabilization | numerical boundary | User approval; MITC literature and thesis 6-DOF discussion | must | Formulation review, invariant and rank tests | Exact `10^-3` positive rotational-diagonal rule; physical outputs exclude drilling | Fixed by Requirements 033-036 | Formulation; Numerical Review; Implementation Planning | approved |
|
||||
| `039-048` | Mandatory HDF5 output and failure atomicity | output | User approval; ADR-005/016/018 | must | Recovery, schema, identity, nonfinite and atomicity tests | Every quantity/location/unit/identity exists; failure commits no partial success | Exact component/location inventory; I/O Definition owns schema | Formulation; I/O Definition; Implementation Planning | approved |
|
||||
| `049-057` | TDD, invariants, patch, locking, geometry, curved shell and physics | verification | User approval; shell benchmark evidence; project process | must | CTest evidence, analytical/patch/convergence reports and physics review | Every verification family has passing evidence before release | `1e-12` symmetry/frame; `1e-10` rigid/residual; convergence targets by Numerical Review | Research; Numerical Review; Reference Model; Implementation Planning | approved-with-downstream-decision |
|
||||
| `058-060` | Translational displacement pass/fail tolerance | tolerance | User approval | must | Comparator unit/integration tests and report review | Every matched U row uses the approved mixed tolerance without clamp/omission | Floors/coefficient: Reference Model + Numerical Review | Reference Model; Reference Verification | approved-with-downstream-decision |
|
||||
| `061-062` | Rotational warning and drilling-energy warning | tolerance/warning | User approval | must | Comparator/diagnostic tests and report review | UR never changes pass/fail; large error and energy ratio produce deterministic visible warnings | Thresholds: Reference Model + Numerical Review | Numerical Review; Reference Model; Reference Verification | approved-with-downstream-decision |
|
||||
| `049-057` | TDD, invariants, patch, declared references and physics | verification | User approval; shell formulation evidence; project process | must | CTest evidence, analytical/patch tests, two reference cases and physics review | Required tests pass; removed calibration/portfolio checks are not reintroduced | `1e-12` symmetry/frame; `1e-10` rigid/residual | Numerical Review; Implementation Planning | approved |
|
||||
| `058-060` | Translational displacement pass/fail tolerance | tolerance | User approval; B33 baseline | must | Comparator unit/integration tests and report review | Every matched U row uses `1e-9 + 1e-6*reference_scale_c` without clamp/omission | Fixed by Requirements 058-060 | Reference Verification | approved |
|
||||
| `061-062` | Rotational warning-only comparison | tolerance/warning | User approval; B33 baseline | must | Comparator/diagnostic tests and report review | UR never changes pass/fail; same mixed-tolerance exceedance emits a deterministic warning | Fixed by Requirements 061-062 | Reference Verification | approved |
|
||||
| `063-064` | Row/schema failure and report completeness | reference verification | User approval; ADR-005/014/018 | must | Negative comparator and report-schema tests | Invalid inventory fails before numeric comparison; all U/UR metrics remain visible | No ignored invalid rows | I/O Definition; Reference Verification | approved |
|
||||
| `065-068` | `reference/shell` inventory and artifact validity | reference | User declaration; project artifact policy | must | Read-only inventory and schema/provenance review | Candidate becomes usable only after exact files, S4R type, provenance and row schema are validated | Current state `needs-reference-artifacts` | Reference Model | needs-reference-artifacts |
|
||||
| `069-071` | S4/S4R coverage and displacement-only comparison | reference | User approval | must | Portfolio coverage and HDF5-to-CSV comparison | At least one model per source type; only U is blocking and UR is warning-only | Requirements `058-064` | Reference Model; Reference Verification; Physics Evaluation | approved-with-downstream-decision |
|
||||
| `065-068` | Exact S4/S4R reference-case inventory and row validity | reference | User declaration; ADR-019 | must | Read-only inventory and source-row/component precheck | Four declared paths exist; required rows are unique, finite and deterministically mapped | Requirements `058-063` | Reference Model; Reference Verification | approved |
|
||||
| `069-071` | S4/S4R coverage and displacement-only comparison | reference | User approval | must | HDF5-to-CSV comparison | Declared S4/S4R cases; only U blocks and UR only warns | Requirements `058-064` | Reference Verification; Physics Evaluation | approved |
|
||||
| `072` | Reference solver/artifact immutability | governance | User/project policy; ADR-010 | must | Process audit and Git diff | No unapproved execution or artifact mutation | Exact zero mutations | All downstream agents | approved |
|
||||
|
||||
## Open Questions and Required Downstream Decisions
|
||||
|
||||
No additional user scope decision is pending. The following technical values must remain visible
|
||||
and be approved by their named downstream owners before Implementation Planning:
|
||||
|
||||
1. Research and Numerical Review shall define a dimensionally consistent drilling reference stiffness, dimensionless coefficient range and nominal value.
|
||||
2. Numerical Review shall approve the maximum drilling-to-physical strain-energy warning ratio and the displacement/resultant sensitivity criterion for coefficient variation.
|
||||
3. Research and Numerical Review shall define the smooth-patch director angle criterion and scale-aware degenerate/Jacobian thresholds without an arbitrary `max(1, ...)` clamp.
|
||||
4. Reference Model and Numerical Review shall define MITC4 U component absolute floors and relative coefficients in the approved mixed-tolerance form.
|
||||
5. Reference Model and Numerical Review shall define the nonblocking UR large-error threshold and reporting severity.
|
||||
6. Formulation shall fix quadrature, tying-point interpolation, shear correction, local axes, sign conventions and recovery locations consistent with this baseline.
|
||||
7. `reference/shell/` shall be re-inventoried when visible. Until then its exact filenames, units, provenance and CSV schema are not established evidence.
|
||||
8. Separate `S4` end-to-end evidence remains required even if the declared `S4R` candidate is valid.
|
||||
9. The existing formulation draft's 5-DOF-only and no-drilling statements conflict with this approved baseline and shall be revised during the Formulation gate, not patched silently during implementation.
|
||||
No user or numerical calibration decision remains before Implementation Planning. Formulation
|
||||
shall retain exact quadrature, tying interpolation, local-axis, sign and recovery definitions.
|
||||
Future geometric-nonlinear execution remains separately unauthorized even though its residual
|
||||
and tangent derivation may remain in the formulation document.
|
||||
|
||||
## Downstream Handoff
|
||||
|
||||
### Research Agent
|
||||
|
||||
- Establish source-backed MITC4 linear kinematics, tying, quadrature, shear correction and benchmark applicability.
|
||||
- Research dimensionally consistent 6-DOF drilling stabilization alternatives and sensitivity/energy criteria; distinguish the thesis's printed `10^-3 min(Kii)` rule from a FESA-approved scale-aware rule.
|
||||
- Research nodal-director generation, smooth-patch angle handling and distorted/warped geometry limits.
|
||||
- Identify nodal-load-compatible flat, locking, distorted and curved-shell benchmark families.
|
||||
- Record the thesis drilling rule and the approved dimensional restriction to positive physical rotational diagonals; do not reopen coefficient calibration.
|
||||
- Preserve nodal-director and geometry evidence as implementation guidance without creating `NR-O03`/`NR-O04` calibration gates.
|
||||
|
||||
### Formulation Agent
|
||||
|
||||
- Revise `docs/formulations/mitc4-shell-formulation.md` to align with global 6-DOF input/output and a physical 5-DOF MITC4 kernel plus numerical drilling embedding.
|
||||
- Keep current-product equations strictly linear static; retain geometric-nonlinear residual/tangent only as clearly separated future formulation.
|
||||
- Define local frames, transformations, generalized component order, quadrature/tying, stress/resultant recovery, energy split and consistent units/signs.
|
||||
- Define local frames, transformations, generalized component order, quadrature/tying, stress/resultant recovery and consistent units/signs.
|
||||
- Do not introduce distributed-load product support or make `S4R` select reduced integration.
|
||||
|
||||
### Numerical Review Agent
|
||||
|
||||
- Independently review the revised formulation for rigid modes, rank, symmetry, invariance, locking, distortion, Jacobian/director validation and drilling contamination.
|
||||
- Approve every downstream numerical threshold listed above before Implementation Planning.
|
||||
- Require coefficient sensitivity and artificial-energy evidence rather than accepting a small coefficient by assertion.
|
||||
- Independently review the revised formulation for dimensions, rigid modes, rank, symmetry, invariance, Jacobian/director handling and separation of fixed drilling stabilization from physical recovery.
|
||||
- Treat drilling calibration/energy-ratio checks and `NR-O03`/`NR-O04` as removed scope, not missing evidence.
|
||||
|
||||
### I/O Definition Agent
|
||||
|
||||
- Define the exact Abaqus keyword/data subset for `S4`, `S4R`, single-layer `*SHELL SECTION`, material, BC and CLOAD semantics.
|
||||
- Define source identity, auto-director metadata, unsupported-drilling-load projection, diagnostics and exact HDF5 dataset/row schemas.
|
||||
- Define source identity, auto-director data, unsupported-drilling-load projection, diagnostics and exact HDF5 dataset/row schemas without drilling-specific result datasets.
|
||||
- Preserve source element type separately from FESA formulation and define bottom/middle/top stress location identity.
|
||||
|
||||
### Reference Model Agent
|
||||
|
||||
- Re-inventory the user-declared `reference/shell/` candidate read-only and report exact files, S4R identity, provenance, units, step/frame and CSV row schema or `needs-reference-artifacts`.
|
||||
- Do not rename or repair noncanonical files; propose an explicit legacy alias only if retaining them is justified.
|
||||
- Prepare coverage for both S4 and S4R, flat/thin/thick/distorted/curved response and the approved displacement-only blocking comparison.
|
||||
- Propose evidence-backed U tolerance coefficients/floors and UR warning thresholds for Numerical Review approval.
|
||||
- Record the exact existing S4 and S4R input/displacement CSV paths from Requirements 065-066 and keep them read-only.
|
||||
- Define only the HDF5-to-CSV source-node/component projection and the already approved B33 mixed tolerance; do not add bundle administration or portfolio gates.
|
||||
|
||||
### Implementation Planning Agent
|
||||
|
||||
- Do not start until Research, revised Formulation, Numerical Review, I/O and Reference Model contracts have resolved every named downstream decision.
|
||||
- Do not start until Research, revised Formulation, Numerical Review, I/O and lightweight Reference Model inventory are mutually consistent.
|
||||
- Trace every `must` requirement to RED/GREEN/VERIFY tests and preserve current solver ownership, deterministic assembly and failure-atomic HDF5 boundaries.
|
||||
- Include independent tests for source-type mapping, auto directors, drilling rank/energy/sensitivity, all recovery quantities, schema failures and U-versus-UR comparison behavior.
|
||||
- Use the project Harness skill to propose self-contained implementation Steps for user approval, then write only the approved phase-planning files; do not execute Harness without a separate explicit request.
|
||||
- Include tests for source-type mapping, auto directors, fixed drilling rank/separation, required recovery quantities, row failures and U-versus-UR comparison behavior; exclude coefficient sweeps, drilling energy and `NR-O03`/`NR-O04`.
|
||||
|
||||
@@ -4,12 +4,12 @@
|
||||
|
||||
- feature_id: `linear-static-mitc4-shell`
|
||||
- source_requirement: `docs/requirements/linear-static-mitc4-shell.md`
|
||||
- status: `research-complete-awaiting-approval`
|
||||
- status: `approved`
|
||||
- owner_agent: `research-agent`
|
||||
- date: `2026-08-11`
|
||||
- date: `2026-08-12`
|
||||
- product_scope: small-displacement, small-rotation, single-step linear static analysis
|
||||
- evidence_route: local papers in `docs/reference-papers/MITC4/`, the configured FEM wiki, original peer-reviewed papers, and official Abaqus documentation
|
||||
- reference_inventory_state: `reference/shell/` was not observable during this research; no filename, schema, provenance, unit, or result value is asserted for that user-declared candidate
|
||||
- reference_inventory_state: existing read-only S4 case at `reference/shell/` and S4R case at `reference/shellR/`; exact comparison paths are fixed by the approved requirements
|
||||
- source_policy: each external claim below is assigned a reliability tier; FESA decisions are labeled `Project contract`, and derived recommendations are labeled `Inference` or `Research recommendation`
|
||||
|
||||
This brief supplies evidence to the Formulation, Numerical Review, I/O Definition, and
|
||||
@@ -22,10 +22,10 @@ formulation-equivalent to Abaqus S4 or S4R.
|
||||
1. What kinematics and degrees of freedom define the original four-node continuum-mechanics-based MITC4 element in the linear regime?
|
||||
2. How are the transverse shear components tied, and what evidence supports the quadrature and homogeneous-isotropic section behavior?
|
||||
3. How can the physical five-DOF kernel be exposed through six global rotational components without treating drilling rotation as a physical MITC4 strain?
|
||||
4. Which drilling-stiffness scales are dimensionally defensible, and which coefficient, sensitivity, and artificial-energy decisions remain unsupported?
|
||||
4. What evidence and dimensional restriction support the approved fixed drilling stabilization without turning it into a physical strain or load channel?
|
||||
5. What evidence supports connectivity-derived thickness directions, nodal-normal smoothing, local tangent frames, and geometry rejection?
|
||||
6. What may and may not be inferred when Abaqus S4 and S4R input types are both mapped to one FESA MITC4 formulation?
|
||||
7. Which patch, locking, distortion, curved-shell, and source-solver benchmarks fit the approved nodal-load-only scope?
|
||||
7. Which element-level checks and the declared S4/S4R source-solver cases fit the approved implementation scope?
|
||||
|
||||
## Source Reliability Tiers
|
||||
|
||||
@@ -87,20 +87,20 @@ navigation aid. No key numerical decision relies on them.
|
||||
- **F-12 — Verified transformation, Tier 2 (S3):** The nodal rotation projection can be written `[alpha,beta,gamma]^T = [t1^T;t2^T;n^T] theta_global`, followed by `K_global=T^T K_local T`. An orthonormal right-handed frame preserves virtual work and strain energy.
|
||||
- **F-12A — Kinematic inference requiring explicit review:** A physical rigid rotation of a five-DOF director shell is represented by rigid midsurface translations plus the tangent-plane change of each director; the director-parallel drilling coordinate is a gauge and can be zero. A rigid-mode test must construct those director changes explicitly. Blindly assigning the full spatial rotation vector, including its normal projection, to every six-DOF shell rotation would excite the numerical penalty and test a different quantity.
|
||||
- **F-13 — Verified thesis implementation, Tier 2 (S3):** The thesis fills each otherwise zero local drilling diagonal with `d=10^-3 min(Kii)`. It does not provide a dimensional restriction on which diagonals enter the minimum.
|
||||
- **F-14 — Dimensional inference:** Translational stiffness diagonals have units `force/length`, while rotational stiffness diagonals have units `force*length`. Taking a minimum across all of them is not unit invariant and can change meaning under a length-unit conversion. The unqualified S3 rule is therefore not acceptable as the FESA rule and is already prohibited by P1.
|
||||
- **F-14 — Dimensional inference and approved restriction:** Translational stiffness diagonals have units `force/length`, while rotational stiffness diagonals have units `force*length`. Taking a minimum across all of them is not unit invariant. P1 therefore applies the thesis coefficient only to finite strictly positive physical director-tangent rotational diagonals, all of which have `force*length` units.
|
||||
- **F-15 — Verified precedent, Tier 1 (S9):** Abaqus states that a small drill penalty is proportional to transverse shear stiffness. Its small-strain shell theory presents a rotational constraint scale of the family `G h A_node / (1 + q A_node/h^2)`, multiplied by a small dimensionless factor, with `q=2.5e-5`. The base quantity has units `force*length` and transitions toward a thickness-cubed scale for thin shells. Abaqus says the small factor was selected numerically but does not disclose a general FESA-ready value.
|
||||
- **F-16 — Research recommendation:** Carry at least two dimensionally compatible candidates into Numerical Review: (A) the S9 transverse-shear/area transition family and (B) the isotropic bending rigidity `D_iso=E t^3/[12(1-nu^2)]`. A statistic formed only from the physical rotational block is a third implementation-dependent comparator. Do not silently choose among them in code.
|
||||
- **F-17 — Research recommendation with explicit evidence limit:** `10^-3` may be used only as the center of a logarithmic sensitivity experiment because S3 supplies that order of magnitude; it is not an approved nominal coefficient. Numerical Review must examine lower and higher orders, equation rank/conditioning, physical `U/N/M/Q` sensitivity, and separate drilling energy before fixing a nominal value and range.
|
||||
- **F-18 — Verified evidence gap, Tier 1 (S13):** Abaqus exposes artificial strain energy associated with singular-mode and drill constraints but gives no drill-specific acceptable percentage. Guidance for kinetic energy or dynamic hourglass energy is not transferable to this static drilling penalty. A numerical `E_drill/E_physical` warning limit remains a blocking Numerical Review decision.
|
||||
- **F-16 — Historical alternatives, not current gates:** A transverse-shear/area transition scale and `D_iso=E t^3/[12(1-nu^2)]` are dimensionally compatible alternatives. The project has instead approved the implementation-local statistic `k_ref=min(R+)`, where `R+` contains only positive physical rotational diagonals; no comparison among these alternatives is required in this feature.
|
||||
- **F-17 — Approved project decision with evidence limit:** P1 fixes `k_d=10^-3 k_ref` and `K_drill_local=k_d I4`. The `10^-3` value is a project choice informed by S3, not a claim of universal optimality or Abaqus equivalence. Coefficient sweeps, plateau/conditioning calibration, and response-sensitivity studies are outside the approved implementation gate.
|
||||
- **F-18 — Scope consequence:** S13 supplies no drill-specific acceptable artificial-energy percentage. P1 therefore defines no `E_drill/E_physical` threshold and requires no drilling stiffness, ratio, or energy result dataset. This absence is an explicit scope decision, not missing numerical evidence.
|
||||
- **F-19 — Verified boundary, Tier 1 (S7/S8):** MITC4/D and independent-rotation membrane formulations give drilling rotation physical/variational content. FESA's approved diagonal regularization is not MITC4/D, must not carry a director-parallel applied moment, and does not justify intersecting-shell, sharp-fold, hinge, or shell–beam drilling transfer.
|
||||
|
||||
### Initial director, tangent frame, and geometry evidence
|
||||
|
||||
- **F-20 — Verified precedent, Tier 1 (S10):** Abaqus computes normals from adjacent shell midsurfaces and uses order-independent grouping; its default averaging heuristic requires all normals in a smooth group to remain within 20 degrees. The manual warns that a coarse mesh can create a false fold or smooth a real fold.
|
||||
- **F-21 — Project contract, informed by F-20:** FESA uses one deterministic area-weighted unit director at a smooth shared node and fails discontinuous/opposed incident directions, requiring duplicated source nodes at a physical fold. It does not adopt Abaqus's ability to retain multiple normals at one source node.
|
||||
- **F-22 — Research recommendation:** Use 20 degrees as the first Numerical Review candidate for the maximum incident-normal deviation in a smooth patch, not as a proven theorem. Because it becomes a hard FESA rejection rather than an Abaqus grouping choice, it must be tested against curved benchmark mesh densities and documented as a mesh-resolution limit before approval.
|
||||
- **F-22 — Evidence limit and project decision:** The 20-degree value is an Abaqus modeling heuristic, not a universal MITC4 constant. P1 does not adopt or calibrate a smooth-patch angle in this feature; `NR-O03` is removed. Supported inputs still require finite nonzero, consistently oriented incident normals.
|
||||
- **F-23 — Research recommendation:** Build each tangent frame by selecting the global basis least aligned with the unit director, projecting or crossing it into the tangent plane, normalizing, and forming the second tangent by a cross product. This avoids the near-parallel fixed-axis singularity seen in simpler source examples and is deterministic, but the exact sign/axis rule belongs in Formulation.
|
||||
- **F-24 — Research recommendation:** Geometry acceptance should use dimensionless or geometry-scaled measures, such as positive Jacobian at every Gauss and tying location, `J_min/J_max`, and `J/L_char^2`; it must not use `max(1,geometry_scale)`. No reviewed source establishes a universal numerical cutoff for all valid warped shells, so the constants remain a Numerical Review decision supported by distortion sweeps.
|
||||
- **F-24 — Evidence limit and project decision:** No reviewed source establishes a universal distortion/warp cutoff. P1 therefore requires only the formulation/I/O finite, nonzero-area, topology, and positive-Jacobian predicates and removes `NR-O04`; a distortion/warp threshold sweep is not an implementation-readiness gate.
|
||||
|
||||
### Abaqus S4/S4R mapping and comparison meaning
|
||||
|
||||
@@ -115,9 +115,9 @@ navigation aid. No key numerical decision relies on them.
|
||||
|
||||
## Candidate Benchmarks
|
||||
|
||||
Exact acceptance tolerances are intentionally not assigned here. Published values are
|
||||
source targets whose geometry, units, boundary conditions, and loading must be reproduced
|
||||
and independently checked before becoming a Reference Model contract.
|
||||
This catalog records useful future evidence, not the minimum implementation-completion
|
||||
portfolio. The approved blocking source-solver cases are only the existing S4 and S4R
|
||||
input/displacement pairs named in P1. Published values below do not create additional gates.
|
||||
|
||||
| benchmark_id | source/evidence | configuration and target quantities | verifies | does not verify / adaptation limit |
|
||||
| --- | --- | --- | --- | --- |
|
||||
@@ -131,8 +131,8 @@ and independently checked before becoming a Reference Model contract.
|
||||
| `MITC4-PINCHED-CYLINDER` | S1/S3/S12 | thin cylinder with end diaphragms and concentrated pinching load; radial displacement and mesh convergence. S12 cites `1.825e-5`; S3 uses `L=600`, `R=300`, `t=3`, `E=3e6`, `nu=0.3`, `P=1` and reports `1.8248e-5` | nodal-load-compatible inextensional bending, complex membrane response, curvature, convergence, regular/irregular mesh sensitivity | one response point cannot certify stresses or drilling; diaphragm semantics must fit approved BCs without rigid elements |
|
||||
| `MITC4-NAFEMS-LE3` | S12 | radius-10 hemispherical shell, `t=0.04`, `E=68.25 GPa`, `nu=0.3`, opposite radial `2 kN` point loads; target `Ux(A)=185 mm`; S4 and S4R official cases exist | positive Gaussian curvature, point load, symmetry, automatic directors, S4/S4R source-label coverage candidate | official decks use explicit nodal normals and shorthand symmetry/perturbation semantics; FESA adaptation and mesh refinement are required, and the target is not a tolerance |
|
||||
| `MITC4-SCORDELIS-LO` | S1/S2/S4/S5 | quarter cylindrical roof, mesh convergence of free-edge displacement and preferably field/resultant evidence | mixed-dominated shell behavior and classical convergence comparison | original dead-weight loading is outside P1; only a documented deterministic equivalent nodal CLOAD version may enter FESA product tests |
|
||||
| `MITC4-DIRECTOR-GEOMETRY` | S10 plus P1 | connectivity reversal, smooth curved patches around the candidate angle, opposed normals, duplicated-node fold, valid warp, bow-tie, inversion, degeneracy, and Gauss/tying Jacobian sweeps | deterministic director generation and fail-closed geometry policy | physical shell accuracy |
|
||||
| `MITC4-DRILL-SENSITIVITY` | S3/S9/S13 plus inference | dimensionally compatible scale candidates; logarithmic coefficient sweep around the S3 order; unconstrained rank, constrained solve, `U/N/M/Q`, condition evidence, `E_physical`, and `E_drill` | regularization sufficiency and physical contamination risk | no source supplies an automatic passing coefficient or energy ratio |
|
||||
| `MITC4-DIRECTOR-GEOMETRY` | S10 plus P1 | connectivity reversal, opposed normals, bow-tie, inversion, degeneracy, and Gauss/tying Jacobian checks | deterministic director generation and fail-closed basic geometry policy | `NR-O03`/`NR-O04` calibration and physical shell accuracy |
|
||||
| `MITC4-DRILL-FIXED` | S3 plus P1 | exact positive physical-rotational-diagonal selection, fixed `10^-3` factor, free-element rank, symmetry, and physical-recovery exclusion | implementation of the approved numerical regularization | coefficient optimality, sensitivity plateau, or energy ratio |
|
||||
| `MITC4-S4-S4R-SAME-PATH` | S11 plus P1 | identical supported model written once as S4 and once as S4R; FESA HDF5 numeric rows equal while source metadata differs | approved semantic mapping and deterministic internal path | Abaqus S4/S4R equivalence; their reference displacements are expected to differ on finite meshes |
|
||||
|
||||
The local S3 hemispherical example with target displacement `0.0924` and its reported
|
||||
@@ -143,10 +143,10 @@ problems must not be mixed.
|
||||
## Verification Relevance
|
||||
|
||||
- **Element code verification:** rigid modes, stiffness symmetry, tangent-frame orthonormality, transformation-energy invariance, quadrature cross-checks, individual tying values, and patch fields isolate algebraic mistakes before a source-solver comparison.
|
||||
- **Locking and convergence:** thin/thick cantilevers, pinched cylinder, LE3, and optional Scordelis–Lo must be run as mesh/thickness sequences. Underpredicted displacement on a single thin mesh is evidence of possible locking, not a complete diagnosis.
|
||||
- **Locking and convergence:** thin/thick cantilevers, pinched cylinder, LE3, and Scordelis–Lo remain useful future studies. They are not additional completion gates for the approved two-case implementation scope.
|
||||
- **Geometry verification:** tests must evaluate every formulation-required Gauss and tying location, not only the element center. Director smoothing and Jacobian quality are separate checks; a smooth director cannot rescue a self-intersecting or inverted mapping.
|
||||
- **Drilling verification:** rank success alone is insufficient. Numerical Review must compare physical outputs across the coefficient sweep and examine separate artificial energy. Drilling stabilization must remain absent from `E/N/M/Q/stress` recovery.
|
||||
- **Reference comparison:** a valid S4 and S4R artifact portfolio can test source mapping and global displacement. It cannot prove formulation identity. Schema, node/component identity, units, and finite values fail before P1's mixed displacement tolerance is evaluated.
|
||||
- **Drilling verification:** verify the fixed formula, dimensional family, symmetry, positivity, four-mode regularization, and absence from physical `E/N/M/Q/stress` recovery. Sensitivity and artificial-energy evidence are excluded.
|
||||
- **Reference comparison:** the declared S4 and S4R cases test source mapping and global displacement. They cannot prove formulation identity. Missing, extra, duplicate, nonfinite, or source-node/component-mismatched required rows fail before P1's mixed displacement tolerance is evaluated.
|
||||
- **Physics sanity:** force and global moment balance, symmetry, displacement direction, reaction sign, positive physical energy, free residual, and consistency of recovered resultants remain mandatory even when all reference displacement rows pass.
|
||||
- **Validation boundary:** the identified sources provide analytical, benchmark, and source-solver verification. No experimental dataset was established for the approved homogeneous linear-static feature; physical validation remains N/A unless separately added.
|
||||
|
||||
@@ -172,72 +172,65 @@ problems must not be mixed.
|
||||
2. Use a single documented `2x2` midsurface integration path for source S4 and S4R, subject to independent Formulation derivation and Numerical Review rank/patch checks.
|
||||
3. Use homogeneous-isotropic plane-stress resultants with `5/6` transverse-shear correction as the formulation candidate, and recover linear in-plane stress at `-t/2,0,+t/2`.
|
||||
4. Project global rotations with deterministic right-handed nodal frames and keep drilling stiffness and energy algebraically separate from all physical shell results.
|
||||
5. Reject the unqualified `10^-3 min(all Kii)` rule. Compare the dimensionally compatible F-16 candidates before selecting a scale.
|
||||
6. Treat 20 degrees as a documented smooth-normal candidate requiring mesh/benchmark calibration, not as a self-justifying universal threshold.
|
||||
7. Make pinched cylinder and NAFEMS LE3 the preferred nodal-load-compatible curved tests; retain Scordelis–Lo only as a documented equivalent-nodal-load auxiliary case.
|
||||
5. Apply `10^-3` only to the minimum finite positive physical director-tangent rotational diagonal and use the resulting scalar uniformly for the four local drilling coordinates.
|
||||
6. Do not adopt a calibrated smooth-normal angle or distortion/warp threshold in this feature; retain finite, orientation, topology and positive-Jacobian validation.
|
||||
7. Keep pinched cylinder, NAFEMS LE3 and Scordelis–Lo as optional future evidence rather than implementation-completion requirements.
|
||||
|
||||
### Blocking numerical decisions before Implementation Planning
|
||||
### Closed decisions and nonblocking evidence limits
|
||||
|
||||
1. **Drilling reference scale:** choose between or formally combine the F-16 candidates after unit-rescaling, thickness, mesh-size, rank, and conditioning studies.
|
||||
2. **Drilling coefficient:** define the tested logarithmic range and nominal dimensionless value. S3 supports only considering `10^-3` as an experiment center, not approving it.
|
||||
3. **Drilling acceptance:** define physical displacement/resultant sensitivity and an `E_drill/E_physical` warning rule. If physical energy is zero or near zero, the ratio must not be hidden by an arbitrary denominator clamp; the two energies need explicit classification.
|
||||
4. **Director angle:** approve the hard smooth-patch criterion after checking representative curved mesh densities. The consequence of rejection versus mesh refinement must be documented.
|
||||
5. **Geometry scale:** approve dimensionless Jacobian/warp measures and constants at Gauss and tying locations. No universal source value was identified.
|
||||
6. **Reference tolerances:** P1 assigns U floors/coefficients and UR warning thresholds to Reference Model and Numerical Review; this Research brief supplies no invented values.
|
||||
7. **Artifact inventory:** re-inventory `reference/shell/` read-only when it becomes visible. Until then the user-declared S4R candidate provides no auditable benchmark evidence, and separate S4 evidence is still required.
|
||||
1. **Drilling:** P1 fixes the positive physical-rotational-diagonal scale and `10^-3` factor. Alternative-family comparison, coefficient sweep, conditioning plateau and artificial-energy threshold are not required.
|
||||
2. **Director/geometry:** `NR-O03` and `NR-O04` are removed. The absence of a calibrated smooth angle or distortion/warp cutoff is not missing evidence.
|
||||
3. **Reference tolerance:** P1 reuses the B33 formula `1e-9 + 1e-6*reference_scale_c`; U exceedance fails and UR exceedance only warns.
|
||||
4. **Reference cases:** the existing `reference/shell/` S4 and `reference/shellR/` S4R input/displacement pairs are the complete required inventory. Administrative bundle metadata and an expanded portfolio are not gates.
|
||||
|
||||
These issues do not require a new user scope choice, but Items 1–5 must be closed by
|
||||
Numerical Review before implementation planning can truthfully claim a complete numerical
|
||||
contract.
|
||||
No research-owned numerical decision remains blocking for Implementation Planning.
|
||||
|
||||
## Requirement Traceability
|
||||
|
||||
| requirement area | research evidence | downstream result |
|
||||
| --- | --- | --- |
|
||||
| `006-010` material/section | F-09–F-11 | homogeneous isotropic plane-stress and section recovery candidate; exact I/O remains downstream |
|
||||
| `011-016` director/geometry | F-20–F-24, `MITC4-DIRECTOR-GEOMETRY` | 20-degree and scale-aware geometry candidates; constants remain blocking Numerical Review decisions |
|
||||
| `031-038` 5-to-6 DOF/drilling | F-12–F-19, `MITC4-DRILL-SENSITIVITY` | dimensional rejection of mixed diagonals; scale/coefficient/energy decisions carried forward |
|
||||
| `011-016` director/geometry | F-20–F-24, `MITC4-DIRECTOR-GEOMETRY` | basic deterministic validity rules; `NR-O03`/`NR-O04` calibration removed |
|
||||
| `031-038` 5-to-6 DOF/drilling | F-12–F-19, `MITC4-DRILL-FIXED` | fixed dimensionally compatible rotational-diagonal rule; calibration and energy output excluded |
|
||||
| `037` S4/S4R common path | F-25–F-27, `MITC4-S4-S4R-SAME-PATH` | source mapping supported only as a FESA product decision, never an Abaqus formulation claim |
|
||||
| `039-048` shell outputs | F-09–F-11/F-18 | physical/drilling energy split and bottom/mid/top stress-location evidence |
|
||||
| `049-057` element verification | F-28/F-29 and Candidate Benchmarks | invariant, patch, locking, distortion, curved, drilling, equilibrium, and energy portfolio |
|
||||
| `058-064` U/UR tolerance | F-25–F-27 | displacement comparison is meaningful but numerical tolerance/UR warning values remain with Reference Model/Numerical Review |
|
||||
| `065-072` reference artifacts | S11/S12 and current inventory state | official public S4/S4R candidates identified; local user artifact remains `needs-reference-artifacts` and immutable |
|
||||
| `039-048` shell outputs | F-09–F-11/F-18 | physical shell output and bottom/mid/top stress locations; no drilling-specific dataset |
|
||||
| `049-057` element verification | F-28/F-29 and Candidate Benchmarks | required invariant/patch/fixed-drill checks; broader portfolio remains optional |
|
||||
| `058-064` U/UR tolerance | F-25–F-27 plus P1 | exact B33 mixed tolerance; U blocking and UR warning-only |
|
||||
| `065-072` reference artifacts | S11/S12 and current inventory state | exact existing S4/S4R paths, source-row/component mapping, and immutability |
|
||||
|
||||
## Downstream Handoff
|
||||
|
||||
### Formulation Agent
|
||||
|
||||
- Re-derive the exact bilinear geometry, physical `20x20` kernel, local component order, edge-midpoint shear tying, `B` matrices, plane-stress section matrices, `2x2` quadrature, and bottom/middle/top recovery from S1/S2 rather than copying OCR text blindly.
|
||||
- Revise the existing formulation draft to expose global six-DOF input/output while keeping only two tangent rotations in physical strains. Define `T`, signs, frame construction, physical/drilling energy split, and all units explicitly.
|
||||
- Revise the existing formulation draft to expose global six-DOF input/output while keeping only two tangent rotations in physical strains. Define `T`, signs, frame construction, the fixed drilling embedding, and all units explicitly.
|
||||
- Keep any geometric-nonlinear residual/tangent material in a clearly marked future-only section; it is not part of the approved executable analysis.
|
||||
- Present drilling scales as candidates pending Numerical Review, not as an implementation default.
|
||||
- State the approved fixed drilling rule exactly and do not reintroduce candidate sweeps or drilling-specific recovery.
|
||||
|
||||
### Numerical Review Agent
|
||||
|
||||
- Independently check six physical rigid modes, non-rigid rank, symmetry, transform energy, patch consistency, and every Gauss/tying Jacobian.
|
||||
- Resolve all seven blocking decisions above. Require consistent-unit rescaling and thickness/mesh sweeps for drilling, not only a successful factorization.
|
||||
- Confirm the fixed drilling rule's dimensions, symmetry, positivity and physical-recovery separation without reopening coefficient calibration.
|
||||
- Audit the original MITC4 distortion/membrane-locking limitation and set convergence expectations that do not imply MITC4+ behavior.
|
||||
- Approve benchmark mesh densities compatible with the hard director-angle policy.
|
||||
- Treat `NR-O03`/`NR-O04` and expanded benchmark portfolios as removed/nonblocking scope.
|
||||
|
||||
### I/O Definition Agent
|
||||
|
||||
- Preserve source S4/S4R identity separately from `FESA-MITC4`, while mapping both to one quadrature/kernel path.
|
||||
- Define automatic director metadata, the exact unsupported-drilling-load projection rule, and fail-closed diagnostics for folds, normals, Jacobians, section/material data, and excluded loads.
|
||||
- Define automatic director data, the exact unsupported-drilling-load projection rule, and fail-closed diagnostics for normals, topology, Jacobians, section/material data, and excluded loads without calibrated `theta_smooth`.
|
||||
- Distinguish Gauss, tying, and section positions in HDF5 identities; do not average mismatched result locations.
|
||||
|
||||
### Reference Model Agent
|
||||
|
||||
- Prefer pinched-cylinder and NAFEMS LE3 adaptations for curved nodal-load coverage, and explain every change from the published model needed to fit the approved FESA keyword subset.
|
||||
- Provide at least one S4 and one S4R model, but never use their different Abaqus algorithms to select different FESA kernels.
|
||||
- Re-inventory `reference/shell/` without creating, renaming, repairing, or normalizing artifacts. Establish provenance, units, node/component identity, and supported semantics before using any row.
|
||||
- Propose U mixed-tolerance values and nonblocking UR warning thresholds from actual artifact scales and mesh/convergence evidence for Numerical Review approval.
|
||||
- Record the exact existing S4 and S4R input/displacement paths without creating, renaming, repairing, or normalizing artifacts.
|
||||
- Define deterministic HDF5-to-CSV source-node/component mapping and the fixed B33 tolerance; do not require provenance, naming policy, README/metadata, duplicated model descriptions, or an expanded portfolio.
|
||||
|
||||
### Implementation Planning Agent
|
||||
|
||||
- Do not start until revised Formulation, Numerical Review, I/O, and Reference Model contracts close the blocking decisions.
|
||||
- Translate every selected benchmark and negative geometry case into TDD `RED -> GREEN -> VERIFY` work while preserving the project linear-static lifecycle and deterministic assembly/output rules.
|
||||
- Start after revised Formulation, Numerical Review, I/O, and lightweight Reference Model inventory are mutually consistent.
|
||||
- Use the project Harness skill to draft self-contained RED/GREEN/VERIFY Steps, obtain user approval before writing `phases/` planning files, and never run the executor without a separate explicit request.
|
||||
|
||||
### Coordinator Agent
|
||||
|
||||
- Treat Research as evidence-complete once this brief is approved, but track drilling scale/coefficient/energy, director/Jacobian constants, U/UR tolerance, and missing reference artifacts as downstream blockers.
|
||||
- Treat Research as approved and do not track removed drilling calibration, `NR-O03`/`NR-O04`, tolerance calibration, bundle administration, or portfolio expansion as downstream blockers.
|
||||
- Reopen Requirements only if physical drilling loads, fold/intersection coupling, explicit normals, distributed loads, MITC4+, or nonlinear execution is proposed.
|
||||
|
||||
Reference in New Issue
Block a user