SWBPIPE · The open manual
Part VI · VerificationVI–E13

Part VI

Verification

E. Algorithm and software checks  ·  Lift-off and a gap at one tip

A frame member is fixed at its root. Tip forces are 10.0 N along x and 1.0 N along y. A lift-off support in x starts in contact. A gap of 0.0002 mm in y starts open. Can one support release while the other closes in the same iteration, then settle?

This page preserves a recorded benchmark and its expected values. The dated run below is not a new run of the current product.

These recorded transitions and free-degree residuals do not establish general equilibrium or convergence for other models.

Support state check. The recorded test exercises nonlinear support state or assembled-loop behavior in its benchmark crate. It does not exercise desktop authoring.

Tip lift-off in x releases while a transverse 0.0002 mm gap in y closes. Both change state first, then retain state on the second iteration. x y Fx Fy x โ†’ y โ†‘ z OUT OF THE PAGE (โŠ™) SUPPORTS x: LIFT-OFF ยท y: GAP (+) LOADS AT THE TIP
Fig. VI–E13.—Lift-off and a gap at one tip

1.Inputs.

Illustrative values, taken from no standard and chosen so the arithmetic can be followed by hand. Most do not describe a real pipe; read them in any consistent set of units.

QuantitySymbolValue
Tip axial forceFx10.0 N
Tip transverse forceFy1.0 N
Lift-off support—Ux
Gap support—Uy
Gap clearancec0.0002 mm
Initial lift-off state—active (in contact)
Initial gap state—inactive (open)

2.Method.

On the first iteration the lift-off support releases and the gap closes. On the second iteration neither changes, so the loop has converged. This is the one-way-and-gap arrangement with the one-way support replaced by a lift-off support.

The reference for this group records the expected support states, changed-support counts and final residuals. It does not work out displacements or reactions, so none are tabulated here.

3.Results.

Expected outcome (the reference gives states, counts and residuals, not displacements or reactions)
QuantityExpected
Changed supports, iteration 12
Final changed-support count0
Iteration count2
Free-DOF force residual0.0 N
Free-DOF moment residual0.0 N·mm
Final free-DOF work residual0.0 N·mm
Final lift-off stateinactive (released)
Final gap stateactive (closed)
Convergedtrue
Diagnosticnone

The case record describes these checks:

  • The solve converges in exactly 2 iterations: 2 supports change state on the first iteration and none on the last.
  • Final states match the reference: lift-off support released, gap closed. No diagnostics are raised.
  • At the final iteration the out-of-balance force, moment and work at the free degrees of freedom are all exactly 0.0.
  • The changes in displacement, rotation and reaction over the last iteration stay inside the recorded envelope for this group.

What it shows. Compares final support states, the iteration count, and force balance. It does not compare movements or reactions with a hand calculation.

Path exercised. The benchmark calls the solver’s components directly: elements, loads, frame solver and stress recovery. It does not go through the program’s own model-to-solve path.

Agreement. The loop counts as converged only when no support changes state between iterations. The changed-support count must reach exactly 0 within at most 4 iterations, with no relative or absolute allowance. At the final iteration, out-of-balance force, moment and work at free degrees of freedom must be 0.0. Changes in displacement, rotation and reaction over the last iteration must stay inside the recorded envelope. Long values are shown here to seven significant figures; the tests compare the full values in the record.

4.Recorded command.

This command belongs to the archived source at 462f66975d36cd10d5b8455193ada9517d28d353. Use a checkout of that exact revision. This edition did not run the command. The recorded result does not establish current product support.

git checkout --detach 462f66975d36cd10d5b8455193ada9517d28d353
cd projects/chirality-piping
cargo test --manifest-path validation/benchmarks/nonlinear/Cargo.toml multisupport_acceptance_inventory_uses_narrow_dec_046_policy

Hand calculation: validation/hand_calcs/nonlinear/assembled_multi_support_gap_lift_off_acceptance.md. Test record, with the recorded run of 2026-07-10: nl-assembled-multi-dof-gap-lift-off-accepted-original.md.

Contents · Part VI · The program: swbpipe.com · MIT licence