{
  "$schema": "https://json-schema.org/draft/2020-12/schema",
  "$id": "https://scischema.org/schemas/materials/fatigue-testing/1.0.0/master-schema.json",
  "version": "1.0.0",
  "title": "Fatigue Testing of Metallic Materials",
  "description": "Master schema representing the fatigue testing process for metallic materials, capturing inputs, parameters, equipment, and outputs.",
  "type": "object",
  "properties": {
    "material": {
      "type": "object",
      "description": "Details of the metallic material being tested.",
      "properties": {
        "alloyDesignation": {
          "type": "string",
          "description": "Standard designation of the alloy (e.g., AISI 4140, Al 2024-T3, Ti-6Al-4V)."
        },
        "chemicalComposition": {
          "type": "object",
          "description": "Chemical composition of the material in weight percentage. Keys are element symbols, values are percentages. Optional, as standard alloys are sufficiently identified by alloyDesignation.",
          "unevaluatedProperties": {
            "type": "number",
            "minimum": 0,
            "maximum": 100
          }
        },
        "heatTreatmentCondition": {
          "type": "string",
          "description": "Heat treatment condition of the material (e.g., Q&T, T3, mill-annealed, solution-annealed)."
        }
      },
      "required": [
        "alloyDesignation",
        "heatTreatmentCondition"
      ]
    },
    "specimenGeometry": {
      "type": "object",
      "description": "Physical dimensions and shape of the test specimen, conforming to standards such as ASTM E466 or ISO 1099.",
      "properties": {
        "shape": {
          "type": "string",
          "enum": [
            "cylindrical",
            "flat",
            "hourglass"
          ],
          "description": "Geometric shape of the specimen."
        },
        "notchCondition": {
          "type": "string",
          "enum": [
            "notched",
            "unnotched"
          ],
          "description": "Whether the specimen is notched or unnotched."
        },
        "gaugeLength": {
          "type": "number",
          "minimum": 0,
          "description": "Gauge length of the specimen in millimeters (mm)."
        },
        "crossSectionalArea": {
          "type": "number",
          "minimum": 0,
          "description": "Cross-sectional area of the specimen in square millimeters (mm²)."
        }
      },
      "required": [
        "shape",
        "notchCondition",
        "gaugeLength",
        "crossSectionalArea"
      ]
    },
    "loadingType": {
      "type": "string",
      "enum": [
        "axial",
        "rotatingBending",
        "planeBending",
        "torsion",
        "multiaxial"
      ],
      "description": "Mode of mechanical loading applied during the test."
    },
    "loadingParameters": {
      "type": "object",
      "description": "Parameters defining the loading conditions applied during testing. One of stressAmplitude or strainAmplitude applies depending on the test control type.",
      "properties": {
        "stressAmplitude": {
          "type": "number",
          "minimum": 0,
          "description": "Stress amplitude (σ_a) in megapascals (MPa) for stress-controlled (HCF) tests."
        },
        "strainAmplitude": {
          "type": "number",
          "minimum": 0,
          "description": "Strain amplitude (ε_a) in mm/mm (dimensionless) for strain-controlled (LCF) tests."
        },
        "stressRatio": {
          "type": "number",
          "minimum": -1,
          "maximum": 1,
          "description": "Ratio of minimum to maximum applied stress (R = σ_min / σ_max), defining loading asymmetry. Common values: R = -1 (fully reversed), R = 0 (zero-to-tension), R = 0.1."
        },
        "loadingFrequency": {
          "type": "number",
          "minimum": 0,
          "description": "Number of load cycles applied per second (Hz). Ranges from <1 Hz for LCF to 20-60 Hz for conventional HCF, up to 20 kHz for ultrasonic VHCF testing."
        }
      },
      "required": [
        "stressRatio",
        "loadingFrequency"
      ]
    },
    "testEnvironment": {
      "type": "object",
      "description": "Environmental conditions during the test that may influence crack initiation and propagation.",
      "properties": {
        "temperature": {
          "type": "number",
          "description": "Test temperature in degrees Celsius (°C)."
        },
        "atmosphere": {
          "type": "string",
          "enum": [
            "air",
            "vacuum",
            "inertGas"
          ],
          "description": "Type of atmosphere during the test."
        },
        "medium": {
          "type": "string",
          "description": "Surrounding medium (e.g., ambient, NaCl solution). Especially relevant for corrosion fatigue."
        }
      },
      "required": [
        "temperature",
        "atmosphere"
      ]
    },
    "equipment": {
      "type": "object",
      "description": "Details of the testing equipment and standards used.",
      "properties": {
        "testingMachine": {
          "type": "object",
          "description": "Equipment used to apply cyclic loads",
          "properties": {
            "type": {
              "type": "string",
              "enum": [
                "servoHydraulic",
                "electromechanical",
                "resonance",
                "rotatingBending",
                "ultrasonic"
              ],
              "description": "Type of fatigue testing machine."
            }
          },
          "required": [
            "type"
          ]
        },
        "testingStandard": {
          "type": "string",
          "description": "Normative procedure followed during testing (e.g., ASTM E466, ASTM E606, ISO 1099, DIN 50100, JIS Z 2273)."
        }
      },
      "required": [
        "testingMachine",
        "testingStandard"
      ]
    },
    "outputs": {
      "type": "object",
      "description": "Results and outputs from the fatigue test.",
      "properties": {
        "numberOfCyclesToFailure": {
          "type": "integer",
          "minimum": 0,
          "description": "Total number of load cycles endured before failure (N_f). For runout specimens, this equals the predefined cycle limit."
        },
        "failureCriterion": {
          "type": "string",
          "description": "Criterion used to define failure (e.g., complete separation, stiffness drop, specified crack length)."
        },
        "sNCurve": {
          "type": "object",
          "description": "Parameters of the S-N (Wöhler) curve derived from the test campaign.",
          "properties": {
            "basquinEquation": {
              "type": "object",
              "description": "Basquin equation parameters for stress-controlled (HCF) tests: σ_a = σ'_f * (N_f)^b.",
              "properties": {
                "fatigueStrengthCoefficient": {
                  "type": "number",
                  "description": "Fatigue strength coefficient (σ'_f) in megapascals (MPa)."
                },
                "fatigueStrengthExponent": {
                  "type": "number",
                  "description": "Fatigue strength exponent (b), dimensionless. Typically negative."
                }
              }
            },
            "coffinMansonParameters": {
              "type": "object",
              "description": "Coffin-Manson parameters for strain-controlled (LCF) tests: ε_p = ε'_f * (N_f)^c.",
              "properties": {
                "fatigueDuctilityCoefficient": {
                  "type": "number",
                  "description": "Fatigue ductility coefficient (ε'_f), dimensionless."
                },
                "fatigueDuctilityExponent": {
                  "type": "number",
                  "description": "Fatigue ductility exponent (c), dimensionless. Typically negative."
                }
              }
            },
            "fatigueLimit": {
              "type": "number",
              "description": "Fatigue limit or endurance limit in megapascals (MPa). Applicable to materials that exhibit a true fatigue limit (e.g., ferrous alloys)."
            }
          }
        },
        "failureMode": {
          "type": "object",
          "description": "Details of the failure mode and fracture characteristics, typically documented via SEM fractography.",
          "properties": {
            "initiationSite": {
              "type": "string",
              "enum": [
                "surface",
                "subsurface",
                "inclusion",
                "defect"
              ],
              "description": "Location where the fatigue crack initiated."
            },
            "failureClassification": {
              "type": "string",
              "enum": [
                "surface-initiated",
                "interior-initiated"
              ],
              "description": "Classification of failure initiation mechanism."
            },
            "fractureSurfaceCharacteristics": {
              "type": "string",
              "description": "Description of the fracture surface (e.g., striations, beach marks, river patterns, dimples)."
            }
          },
          "required": [
            "initiationSite"
          ]
        }
      },
      "required": [
        "numberOfCyclesToFailure",
        "failureMode"
      ]
    }
  },
  "required": [
    "material",
    "specimenGeometry",
    "loadingType",
    "loadingParameters",
    "outputs"
  ],
  "unevaluatedProperties": false
}