Goodman / Soderberg Fatigue Diagram implementation

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

t6-064

Effect

Computation or source lookup only

Input and validation requirements

The zero-stress input makes the direct safety-factor calculation divide by zero, and the convention probe shows that interpreting compressive mean stress as signed versus as a magnitude changes the result from 4 to 4/3.

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": {
    "method": "Goodman",
    "sigma_a": 120,
    "sigma_m": 80,
    "Se": 240,
    "Su": 600,
    "units": "MPa"
  },
  "expected_outputs": {
    "safety_factor": 1.578947368,
    "operating_point": {
      "sigma_m": 80,
      "sigma_a": 120,
      "units": "MPa"
    },
    "sampled_failure_line_points": [
      {
        "sigma_m": 0,
        "sigma_a": 240
      },
      {
        "sigma_m": 80,
        "sigma_a": 208
      },
      {
        "sigma_m": 600,
        "sigma_a": 0
      }
    ],
    "key_curve_features": {
      "sigma_a_intercept": 240,
      "sigma_m_intercept": 600,
      "roots": [
        {
          "sigma_m": 600,
          "sigma_a": 0
        }
      ],
      "extrema": [],
      "asymptotes": []
    }
  },
  "working": "Goodman denominator = sigma_a/Se + sigma_m/Su = 120/240 + 80/600 = 0.5 + 0.133333333333 = 0.633333333333. Therefore SF = 1/0.633333333333 = 1.578947368. Failure-line samples: at sigma_m = 0, sigma_a = 240*(1 - 0/600) = 240 MPa; at sigma_m = 80, sigma_a = 240*(1 - 80/600) = 240*(0.866666666667) = 208 MPa; at sigma_m = 600, sigma_a = 240*(1 - 1) = 0 MPa."
}

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-tranche6/tranche6-results.json