Source: https://guthlabs.ai/docs/instruments/torsion-of-circular-shafts/implementation/

instrument implementation / implementation-contract

# Torsion of Circular Shafts implementation

A source-bound implementation contract for Torsion of Circular Shafts; deployment and executable qualification remain separate.

Status: **VERIFIED_CLEAN**Lifecycle: **implementation-contract**

## Binding contract

This record describes what an executable surface must bind and validate. It does not claim that a public calculator, package, or production route is deployed.

**Record owner**: Guth Instruments

**Lifecycle**: verified-clean

**Evidence ID**: t4-058

**Effect**: Computation or source lookup only

## Input and validation requirements

A hollow shaft with do=di produces J=0 and therefore undefined shear stress and angle of twist through division by zero; the instrument must reject the zero-wall-thickness input. A separate convention hazard is the possible radius-versus-diameter misinterpretation, which changes the calculated stress by a factor of 8 and twist by a factor of 16.

## Required corrections

No binding erratum is attached to this unique-name record. Implementers must still preserve the declared units, domain, and failure behavior.

## Inspectable interface fixture

The sample below is evidence for interface and validation tests, not a production implementation.

````
{
  "inputs": {
    "shaft_type": "solid",
    "T_Nmm": 2000000,
    "d_mm": 40,
    "L_mm": 1000,
    "G_N_per_mm2": 80000
  },
  "expected_outputs": {
    "J_mm4": 251327.4123,
    "taumax_N_per_mm2": 159.1549,
    "theta_rad": 0.09947184
  },
  "working": "d⁴ = 40⁴ = 2,560,000 mm⁴. J = πd⁴/32 = π(2,560,000)/32 = 80,000π = 251,327.4123 mm⁴. Outer radius r = d/2 = 20 mm. τmax = Tr/J = (2,000,000)(20)/251,327.4123 = 40,000,000/251,327.4123 = 159.1549 N/mm². θ = TL/(GJ) = (2,000,000)(1,000)/[(80,000)(251,327.4123)] = 2,000,000,000/20,106,192,984 = 0.09947184 rad."
}
````

## Other records

[01**Overview**](<https://guthlabs.ai/docs/instruments/torsion-of-circular-shafts/>)[02**Mechanism**](<https://guthlabs.ai/docs/instruments/torsion-of-circular-shafts/mechanism/>)[04**Qualification**](<https://guthlabs.ai/docs/instruments/torsion-of-circular-shafts/qualification/>)

## Sources and evidence

These pointers bind the page to evidence. They do not grant authority or collapse verification into deployment.

- `VERIFIED_LEDGER.json`

- `evidence-tranche4/tranche4-results.json`