Marin Endurance Limit Modifiers mechanism

Model scope

The algorithm is a standard Shigley-method estimate, but the specification is not sufficiently explicit to receive an unconditional PASS. The exact unresolved ambiguities are: the units of Se', Sut, and geometry; the method and table edition used to derive ka and kb; the load convention for kc; the temperature scale and valid range for kd; and the reliability-table convention for ke. The output should be labeled as an estimated fully reversed endurance limit, not a universally valid fatigue strength.

• The stated formula Se = ka·kb·kc·kd·ke·Se' is the standard Marin-factor correction for a fully reversed endurance limit, provided every factor is dimensionless and applicable to the material, geometry, loading, temperature, and reliability conditions.
• The specification does not define how ka is obtained from surface finish and ultimate tensile strength, although Shigley normally uses finish-specific equations or tables involving Sut.
• The specification does not define the geometry and dimensional range needed for kb; Shigley size factors depend on specimen type, diameter or equivalent diameter, and often have piecewise validity ranges.
• The specification does not define the applicable load-factor convention for kc, especially for combined bending, axial, and torsional loading.
• Temperature-factor kd and reliability-factor ke require defined temperature and reliability conventions and valid table ranges.

Units and conventions

• Se' and Se are assumed to use the same stress unit; the vectors use MPa.
• ka, kb, kc, kd, and ke are dimensionless.
• Temperature must be explicitly identified as Celsius or Fahrenheit because Shigley temperature-factor tables commonly use Fahrenheit-based ranges.
• The reference factors below are already selected from the stated Shigley Marin-factor convention; if the instrument derives them from raw inputs, Sut, geometry, load case, temperature scale, and table edition must be supplied.
• Reliability percentages are interpreted as the reliability entries in the conventional Shigley Marin reliability-factor table.

Inspectable vector

One of 4 source-bound review vectors:

{
  "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."
}

Failure boundary

BREAK_CLAIMED · SELF_FLAGGED

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.

Other records

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
• BOUNDARY_HAZARD_CATALOG.json