{
  "schema": "bounded-graphical-fatigue-curve/v1",
  "id": "c09-finite-cycle-fatigue",
  "basis": {
    "construction": "full-penetration butt-welded carbon steel",
    "environment": "atmospheric noncorrosive",
    "geometric_concentration": "no significant geometric stress concentration",
    "temperature": "room-temperature comparison; historical endurance temperature discussion does not establish finite-cycle temperature correction",
    "quantity": "total cyclic stress range, ksi",
    "curve_role": "historical design relation containing design margin; not observed failure-life law"
  },
  "finite_region": {
    "N_min": 50000,
    "N_max": 10000000,
    "transition_cycle_count": "approximately 10^7; not an exact knee value",
    "points": [
      {
        "N": 50000,
        "approximate_stress_range_ksi": 41,
        "graphic_read_band_ksi": [
          39,
          44
        ]
      },
      {
        "N": 100000,
        "approximate_stress_range_ksi": 34,
        "graphic_read_band_ksi": [
          32,
          36.5
        ]
      },
      {
        "N": 200000,
        "approximate_stress_range_ksi": 28,
        "graphic_read_band_ksi": [
          26,
          30
        ]
      },
      {
        "N": 500000,
        "approximate_stress_range_ksi": 21.5,
        "graphic_read_band_ksi": [
          20,
          23
        ]
      },
      {
        "N": 1000000,
        "approximate_stress_range_ksi": 18,
        "graphic_read_band_ksi": [
          16.5,
          19
        ]
      },
      {
        "N": 2000000,
        "approximate_stress_range_ksi": 14.5,
        "graphic_read_band_ksi": [
          13.5,
          16
        ]
      },
      {
        "N": 5000000,
        "approximate_stress_range_ksi": 11.5,
        "graphic_read_band_ksi": [
          10.5,
          12.5
        ]
      },
      {
        "N": 10000000,
        "approximate_stress_range_ksi": 9.5,
        "graphic_read_band_ksi": [
          8.5,
          10.5
        ]
      }
    ],
    "precision": "coarse graph-derived values; band covers source line/tick thickness and calibration/scan distortion, not statistical confidence",
    "interpolation": "log N and log stress between adjacent points; lower/upper bands interpolated separately; no extrapolation"
  },
  "endurance": {
    "stress_range_ksi": 9.0,
    "basis": "separately specified text value; transition near 10^7 shown schematically"
  },
  "stress_conventions": {
    "symmetric_fully_reversed": "range=2*amplitude",
    "local_detail": "compatible factor and local stress basis required; no automatic transfer to concentrated/branch/threaded details"
  },
  "spot_observation": "factor2 specified for design endurance limits; no separately qualified halved finite-cycle curve",
  "history": "N=f*t at constant frequency; distinct stress levels require compatible cumulative-damage method",
  "excluded_claims": [
    "failure cycle",
    "repair deadline",
    "current code compliance",
    "corrosive or elevated-temperature finite-cycle adequacy"
  ]
}