Imposed displacement on a spring — SWBPIPE verification

Part VI · VerificationVI–B4

Part VI

Verification

B. Elements and loads · Imposed displacement on a spring

A linear spring of stiffness 150.0 N/m has a prescribed displacement of 0.04 m. What reaction does the spring develop?

The case also tests boundary preparation. The spring and imposed displacement must remain separate entries of the correct kinds. No frame system is solved.

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

This benchmark prepares separate spring and displacement entries and compares their product. It does not solve a spring with base motion.

Software boundary check. The recorded test exercises a benchmark crate. It does not exercise the desktop product route.

Read with

This case checks a prepared spring boundary. Model document 0.4.0 supports explicit motions on already rigidly restrained degrees of freedom. It refuses spring base motion and device preload/reference laws (Status).

Fig. VI–B4.—Imposed displacement on a spring

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.

Quantity	Symbol	Value
Spring stiffness	k	150.0 N/m
Imposed displacement	u	0.04 m

2.Method.

For a linear spring the reaction is stiffness times displacement.

R = ku = 150.0 × 0.04 = 6.0 N(1)

3.Results.

Spring reaction
Quantity	Expected
Spring reaction magnitude	6.0 N

The case record describes these checks:

Boundary preparation accepts the spring and the imposed displacement without blocking.
Exactly one spring and one imposed displacement are recorded.
The prepared stiffness times the prepared displacement matches the reference reaction.

What it shows. Checks the loads or boundary conditions prepared for the solver against a hand calculation. No system is solved.

Path exercised. Boundary preparation and the k*u reference calculation only. No frame system is solved.

Agreement. Each computed value must match the reference within an absolute difference of 1.0 × 10⁻⁹ in the case’s own units. Counts and structural outcomes must match exactly. 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/mechanics/Cargo.toml imposed_displacement_fixture_prepares_support_boundary

Hand calculation: validation/hand_calcs/mechanics/imposed_displacement_spring.md. Test record, with the recorded run of 2026-07-10: mech-imposed-displacement-spring.md.