tests: add the NAFEMS LE7 cylinder/sphere oracle case

The thin-walled cylinder with a hemispherical cap under internal
pressure as four axisymmetric quad8 blocks: axial stress on the outer
surface at D 25.283.

The NAFEMS target, 25.86, is the axisymmetric thin-shell solution; our
solid model converges to 25.27, the value ESRD reports for its converged
axisymmetric solid. So the NAFEMS quantity keeps a 1% tolerance and is
a known failure until there is an axisymmetric shell element, and a
second quantity checks the model against the solid reference (pass,
0.05%).

Part of #97.

docs/oracle.md

@@ -2,7 +2,7 @@
 
 Generated by `cargo xtask oracle` from [`tests/oracle/`](../tests/oracle/); the policy is [verification.md](verification.md). Every case is our own model, built with FieldCraft commands from the problem's published description, and compared with the reference value its `expected.json` cites, within the stated tolerance and for the stated reason. Accepted results are frozen in each case's `fixture.json`: a later change that moves one beyond its band (10⁻⁹ of its size) fails CI even while the reference still passes. No reference value was produced with a commercial product.
 
-**281 of 287 quantities pass** (6 known failure(s)) in 76 active cases: 62 theory, 14 published benchmark, 0 experiment; 8 pending cases wait for capabilities still being built.
+**282 of 289 quantities pass** (7 known failure(s)) in 77 active cases: 62 theory, 15 published benchmark, 0 experiment; 8 pending cases wait for capabilities still being built.
 
 ## Theory: closed-form solutions, patch tests and mesh invariants
 
@@ -297,6 +297,8 @@ Generated by `cargo xtask oracle` from [`tests/oracle/`](../tests/oracle/); the
 | [nafems-le2](../tests/oracle/nafems-le2/) | tangential stress at E, outer surface, load case 2 (pressure and edge traction) | 60 | 59.904 | -0.161% | 1% | pass | matches |
 | [nafems-le3](../tests/oracle/nafems-le3/) | radial displacement at A (10, 0, 0), m | 0.185 | 0.18418 | -0.446% | 2% | pass | matches |
 | [nafems-le5](../tests/oracle/nafems-le5/) | σ_xx at A (2.5, −1, −1), mid-surface of the lower flange at its free edge | -108 | -109.45 | -1.35% | 2% | pass | matches |
+| [nafems-le7](../tests/oracle/nafems-le7/) | axial stress σ_yy at D (1.0125, 1.4034), outer surface | 25.86 | 25.283 | -2.23% | 1% | known failure: the target is the axisymmetric thin-shell solution and FieldCraft has no axisymmetric shell element; our axisymmetric solid model converges to 25.27 (−2.3%), the value ESRD reports for its converged axisymmetric solid (quantity syy_D_solid) | — |
+| [nafems-le7](../tests/oracle/nafems-le7/) | axial stress σ_yy at D (1.0125, 1.4034), outer surface, against the converged solid model | 25.27 | 25.283 | 0.0496% | 1% | pass | matches |
 | [pinched-cylinder](../tests/oracle/pinched-cylinder/) | radial displacement under the load, mid-surface | -1.8248e-5 | -1.8038e-5 | 1.15% | 2% | pass | matches |
 | [scordelis-lo-roof-shell](../tests/oracle/scordelis-lo-roof-shell/) | vertical displacement at the midpoint of the free edge, mid-surface | -0.3024 | -0.29901 | 1.12% | 2% | pass | matches |
 | [scordelis-lo-roof-solid](../tests/oracle/scordelis-lo-roof-solid/) | vertical displacement at the midpoint of the free edge, mid-surface | -0.3024 | -0.3014 | 0.33% | 2% | pass | matches |
@@ -342,6 +344,7 @@ Generated by `cargo xtask oracle` from [`tests/oracle/`](../tests/oracle/); the
 - **[nafems-le2](../tests/oracle/nafems-le2/)** (benchmark): NAFEMS LE2 cylindrical shell bending patch test (MITC4 shells). Source: NAFEMS, The Standard NAFEMS Benchmarks, TNSB Rev. 3, October 1990, test LE2 (target: tangential stress 60 MPa on the outer surface at E, both load cases); the problem and target as reproduced in the Abaqus 2016 Benchmarks Guide, section 4.2.2 'LE2: Cylindrical shell bending patch test', and in the ESRD StressCheck Benchmarks Guide 'The Standard NAFEMS Benchmarks: Linear Elastic Tests' (2018), p. 8. Tolerances — stt_E_moment: the target is the exact thin-shell value (6M/t²) and the stress is uniform over the patch; the 8 × 8 flat facets tilt the element axes by ±1.875° from the hoop direction, which moves 0.1% of it into σ_zz, and 16 × 16 is within 0.03% (see README); stt_E_pressure: the target is the exact membrane value (pR/t) and the stress is uniform over the patch; as in load case 1 the facets' tilt and the pressure on flat facets keep 8 × 8 within 0.2%, 16 × 16 within 0.05% (see README)
 - **[nafems-le3](../tests/oracle/nafems-le3/)** (benchmark): NAFEMS LE3 hemispherical shell with point loads (MITC4 shells). Source: NAFEMS, The Standard NAFEMS Benchmarks, TNSB Rev. 3, October 1990, test LE3 (target: radial displacement 0.185 m at A); the problem and target as reproduced in the Abaqus 2016 Benchmarks Guide, section 4.2.3 'LE3: Hemispherical shell with point loads', and in the ESRD StressCheck Benchmarks Guide 'The Standard NAFEMS Benchmarks: Linear Elastic Tests' (2018), p. 12. Tolerances — ur_A: the target is published to three figures; the displacement under a point load on a shear-deformable shell keeps growing slowly as the mesh is refined (32 × 32 is 0.44% low, 64 × 64 0.16%; see README)
 - **[nafems-le5](../tests/oracle/nafems-le5/)** (benchmark): NAFEMS LE5 Z-section cantilever (hex20). Source: NAFEMS, The Standard NAFEMS Benchmarks, TNSB Rev. 3, October 1990, test LE5 (target: axial stress −108 MPa at A, mid-surface); the problem and target as reproduced in the Abaqus 2016 Benchmarks Guide, section 4.2.5 'LE5: Z-section cantilever', and in the ESRD StressCheck Benchmarks Guide 'The Standard NAFEMS Benchmarks: Linear Elastic Tests' (2018), p. 15. Tolerances — sxx_A: the target is published to three figures and comes from a thin-walled idealisation; a 3D solid model of the section converges about 1.5% beyond it (ours: −109.46 here, −109.60 on the next mesh; ESRD's p-version solid: −109.5, see README)
+- **[nafems-le7](../tests/oracle/nafems-le7/)** (benchmark): NAFEMS LE7 axisymmetric cylinder/sphere under pressure (axisymmetric quad8). Source: NAFEMS, The Standard NAFEMS Benchmarks, TNSB Rev. 3, October 1990, test LE7 (target: axial stress 25.86 MPa on the outer surface at D, R = 1.0125, Z = 1.4034), as reproduced in the ESRD StressCheck Benchmarks Guide 'The Standard NAFEMS Benchmarks: Linear Elastic Tests' (2018), p. 23, which also gives its converged axisymmetric solid result, 25.27 MPa (p. 24); the Abaqus 2016 Benchmarks Guide, section 4.2.7 'LE7: Axisymmetric cylinder/sphere under pressure', gives the target rounded to 25.9 MPa. Tolerances — syy_D: the target is published to four figures for the thin-shell model of the vessel, and a model of the same theory converges well within 1%; syy_D_solid: the same model idealisation (axisymmetric solid) as the reference, which ESRD reports converged to under 1% on two meshes; ours moves by 0.05% on the next refinement (see README)
 - **[nl-contact-patch](../tests/oracle/nl-contact-patch/)** (theory): Contact patch test: two blocks with non-matching meshes in uniaxial compression (implicit mortar contact). Source: The contact patch test: a contact discretisation must transmit a uniform pressure across a non-matching interface exactly; Taylor & Papadopoulos, On a patch test for contact problems in two dimensions, Nonlinear Computational Mechanics, Springer 1991, 690–702; Crisfield, Re-visiting the contact patch test, IJNME 48:435–449, 2000; passed by mortar methods: Puso & Laursen, CMAME 193:601–629, 2004. Uniaxial stress between frictionless symmetry planes is uniform in both blocks. Tolerances — small_lower_corner: small sliding is linear and its mortar integrals exact on these rectangular faces: a uniform stress is the discrete solution up to the convergence tolerance (10⁻¹⁰); small_lower_centre: as for the corner element; small_lower_base: as for the corner element; small_upper_top: as for the corner element; small_lateral: frictionless symmetry planes and a frictionless interface leave the blocks free to expand sideways; the non-matching interface must not hold them; small_pressure: the mortar multipliers are the nodal values of the contact pressure, uniform and equal to the stress across the interface; small_force: the pressure carries the whole load across the interface; finite_lower_corner: finite sliding is exact up to the geometric terms of the gaps the augmentation leaves (10⁻⁵ of the element thickness) and the default convergence tolerances; finite_lower_centre: as for the corner element; finite_lower_base: as for the corner element; finite_upper_top: as for the corner element; finite_lateral: frictionless symmetry planes and a frictionless interface leave the blocks free to expand sideways; the non-matching interface must not hold them; finite_pressure: the mortar multipliers are the nodal values of the contact pressure, uniform and equal to the stress across the interface; finite_force: the pressure carries the whole load across the interface; small_stress: the squeeze less the penetration the augmented Lagrangian leaves (up to 10⁻⁵ of the element thickness, a few 10⁻⁵ of the squeeze)
 - **[nl-contact-patch-axisymmetric](../tests/oracle/nl-contact-patch-axisymmetric/)** (theory): Contact patch test, axisymmetric: two rings with non-matching edges in axial compression (implicit mortar contact). Source: The contact patch test: a contact discretisation must transmit a uniform pressure across a non-matching interface exactly; Taylor & Papadopoulos, On a patch test for contact problems in two dimensions, Nonlinear Computational Mechanics, Springer 1991, 690–702; passed by 2D mortar methods: Yang, Laursen & Meng, IJNME 62:1183–1225, 2005. Uniaxial stress between frictionless supports is uniform in both blocks. Tolerances — small_lower_corner: small sliding is linear and its edge mortar integrals exact (degree-3 Gauss on the overlaps): the uniform stress is the discrete solution up to the convergence tolerance; small_lower_far: as for the corner element; small_lower_base: as for the corner element; small_upper_top: as for the corner element; small_lateral: a frictionless interface (and symmetry plane) leaves the blocks free to expand sideways; the non-matching interface must not hold them; small_pressure: the mortar multipliers are the nodal values of the contact pressure, uniform and equal to the stress across the interface; small_force: the pressure carries the whole load across the interface (both are totals over the circumference); finite_lower_corner: finite sliding is exact up to the geometric terms of the gaps the augmentation leaves (10⁻⁵ of the element thickness) and the default convergence tolerances; finite_lower_far: as for the corner element; finite_lower_base: as for the corner element; finite_upper_top: as for the corner element; finite_lateral: a frictionless interface (and symmetry plane) leaves the blocks free to expand sideways; the non-matching interface must not hold them; finite_pressure: the mortar multipliers are the nodal values of the contact pressure, uniform and equal to the stress across the interface; finite_force: the pressure carries the whole load across the interface (both are totals over the circumference); small_stress: the squeeze less the penetration the augmented Lagrangian leaves (up to 10⁻⁵ of the element thickness)
 - **[nl-contact-patch-plane-strain](../tests/oracle/nl-contact-patch-plane-strain/)** (theory): Contact patch test in plane strain: two blocks with non-matching edges in uniaxial compression (implicit mortar contact). Source: The contact patch test: a contact discretisation must transmit a uniform pressure across a non-matching interface exactly; Taylor & Papadopoulos, On a patch test for contact problems in two dimensions, Nonlinear Computational Mechanics, Springer 1991, 690–702; passed by 2D mortar methods: Yang, Laursen & Meng, IJNME 62:1183–1225, 2005. Uniaxial stress between frictionless supports is uniform in both blocks. Tolerances — small_lower_corner: small sliding is linear and its edge mortar integrals exact (degree-3 Gauss on the overlaps): the uniform stress is the discrete solution up to the convergence tolerance; small_lower_far: as for the corner element; small_lower_base: as for the corner element; small_upper_top: as for the corner element; small_lateral: a frictionless interface (and symmetry plane) leaves the blocks free to expand sideways; the non-matching interface must not hold them; small_pressure: the mortar multipliers are the nodal values of the contact pressure, uniform and equal to the stress across the interface; small_force: the pressure carries the whole load across the interface (both are totals over the thickness); finite_lower_corner: finite sliding is exact up to the geometric terms of the gaps the augmentation leaves (10⁻⁵ of the element thickness) and the default convergence tolerances; finite_lower_far: as for the corner element; finite_lower_base: as for the corner element; finite_upper_top: as for the corner element; finite_lateral: a frictionless interface (and symmetry plane) leaves the blocks free to expand sideways; the non-matching interface must not hold them; finite_pressure: the mortar multipliers are the nodal values of the contact pressure, uniform and equal to the stress across the interface; finite_force: the pressure carries the whole load across the interface (both are totals over the thickness); small_stress: the squeeze less the penetration the augmented Lagrangian leaves (up to 10⁻⁵ of the element thickness)