Source: https://guthlabs.ai/docs/instruments/marin-endurance-limit-modifiers/implementation/

instrument implementation / implementation-contract

# Marin Endurance Limit Modifiers implementation

A source-bound implementation contract for Marin Endurance Limit Modifiers; 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**: t7-022

**Effect**: Computation or source lookup only

## Input and validation requirements

A zero ultimate tensile strength produces the undefined expression 4.51·0^(-0.265) in the surface-finish factor. The instrument must reject this input; accepting it risks infinity, NaN, or an invalid corrected endurance limit.

## 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": {
    "Se_prime_MPa": 300,
    "surface_finish": "ground",
    "surface_factor_ka": 0.9,
    "size_description": "round specimen, 25 mm diameter",
    "size_factor_kb": 0.879,
    "load_type": "bending",
    "temperature_C": 20,
    "temperature_factor_kd": 1,
    "reliability_percent": 50,
    "reliability_factor_ke": 1
  },
  "expected_outputs": {
    "Se_MPa": 237.33
  },
  "reference_data": {
    "ka": {
      "value": 0.9,
      "source_convention": "Shigley Marin surface-finish factor convention; widely tabulated standard value for this test case"
    },
    "kb": {
      "value": 0.879,
      "source_convention": "Shigley Mechanical Engineering Design size-factor relation, evaluated for the stated round geometry; widely tabulated standard value"
    },
    "kc": {
      "value": 1,
      "source_convention": "Shigley Marin load-factor table, bending entry; widely tabulated standard value"
    },
    "kd": {
      "value": 1,
      "source_convention": "Shigley Marin temperature-factor table at the stated ordinary-temperature condition; widely tabulated standard value"
    },
    "ke": {
      "value": 1,
      "source_convention": "Shigley Marin reliability-factor table, 50% reliability entry; widely tabulated standard value"
    }
  },
  "working": "Se = ka·kb·kc·kd·ke·Se'\n= 0.900·0.879·1.000·1.000·1.000·300 MPa\n= 0.7911·300 MPa\n= 237.33 MPa."
}
````

## Other records

[01**Overview**](<https://guthlabs.ai/docs/instruments/marin-endurance-limit-modifiers/>)[02**Mechanism**](<https://guthlabs.ai/docs/instruments/marin-endurance-limit-modifiers/mechanism/>)[04**Qualification**](<https://guthlabs.ai/docs/instruments/marin-endurance-limit-modifiers/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-tranche7/tranche7-results.json`