ashfordeOU Radiographic Inspection (manufacturing-quality/ndt/radiographic-inspection)
Use when the task is executing industrial radiography (RT) on an aerospace part: computing the setup geometry (geometric unsharpness), selecting and reading the image quality indicator (IQI) penetrameter, setting the exposure time for X-ray or gamma-ray sources, judging the processed film density, and classifying the discontinuities that the radiograph reveals.
Domain quick reference
- Geometric unsharpness: Ug = F * ODD / SOD, with F the effective focal spot size, SOD the source-to-object distance, and ODD the object-to-detector distance, all in mm. Example: a 3 mm focal spot at 500 mm SOD with 30 mm ODD gives Ug = 3 * 30 / 500 = 0.18 mm. A finer focal spot and a longer source distance reduce unsharpness; a typical limit for fine-detail work is 0.25 mm. X-ray tubes can have small focal spots (fractions of a mm), while gamma-ray isotopes such as Ir-192 and Co-60 have larger effective focal spots, so gamma setups trade more unsharpness for portability.
- Exposure time by the inverse-square law: t2 = t1 * (d2 / d1)^2, with t1 the exposure time measured or charted at reference distance d1 and t2 the time needed at distance d2. Doubling the source-to-film distance quadruples the required time; halving it quarters the time. Example: 4 min at 900 mm becomes 1 min at 450 mm.
- IQI (penetrameter) sensitivity: sensitivity percent = visible_thickness / part_thickness * 100, where visible_thickness is the thinnest IQI feature (hole or step) visible on the radiograph and part_thickness is the section thickness examined. Typical aerospace acceptance requires 2 percent or better; the penetrameter is placed on the source side of the part.
- Film density: optical density of the processed film, typically judged against a 2.0 to 4.0 band (density below the band is underexposed and too light, above it is overexposed and too dark). The governing specification may set a narrower range; the 2.0 to 4.0 band is common practice, not a universal requirement.
- Discontinuities on the radiograph: porosity appears as round or globular voids (often clustered), cracks as sharp, narrow, elongated lines, inclusions as compact foreign material (metallic inclusions appear brighter on the film), and slag as flat, planar, or angular nonmetallic residue, typically in weld context.
- AS9100 clause 8.5.1.3 frames NDT as a special process: radiography is performed to an approved written procedure by qualified, certified personnel, with calibrated equipment and recorded results, before the part is accepted or released.
Workflow
- Define the inspection geometry: the effective focal spot F, the source-to-object distance SOD, and the object-to-detector distance ODD. Compute the geometric unsharpness with geometric_unsharpness(F, SOD, ODD) and confirm it is at or below the required limit (default 0.25 mm for fine detail); rework the geometry otherwise.
- Select the IQI penetrameter for the section thickness, place it on the source side, and determine the sensitivity with iqi_sensitivity_percent(visible_thickness, part_thickness); confirm the sensitivity meets the acceptance requirement (typically 2 percent or better).
- Establish the baseline exposure (chart or prior technique) at its reference distance and recompute for the actual source-to-film distance with exposure_time(base_time, distance, reference_distance) using the inverse-square law.
- Expose and process the film, then check the density with density_verdict(film_density) against the 2.0 to 4.0 band; reshoot if the density is out of band.
- Read the radiograph and classify each indication with discontinuity_class(geometry_descriptor) as porosity, crack, inclusion, or slag, then disposition against the approved acceptance criteria.
- Combine the checks with rt_setup_verdict(unsharpness, sensitivity, density); a failing check means the technique or the exposure must be reworked and the part reshoot before acceptance.
Pitfalls
- Zero source-to-object distance: Ug = F * ODD / SOD is undefined at SOD = 0; the module raises ValueError instead of dividing by zero.
- Ignoring the object-to-detector distance: film held far off the part inflates unsharpness; keep the detector as close to the object as the geometry allows.
- Scaling exposure linearly with distance: the inverse-square law is quadratic, so doubling distance needs 4x the time, not 2x.
- IQI on the wrong side or wrong size: the penetrameter goes on the source side and its feature sizes must match the section thickness, or the sensitivity reading is meaningless.
- Judging the image without the density check: a radiograph can show a clear image while the film density is outside the band, which fails the technique requirements.
- Confusing film density with material density: the density verdict here is the optical density of the processed film, not the density of the part material.
- Misclassifying indications: porosity is round and globular, cracks are sharp and elongated; reading a crack as porosity changes the disposition from reject to accept.
- Verbatim clause text: AS9100 is proprietary; this skill paraphrases the special-process framing and references the standard only.
Behavior contract (gate 3)
The inspection math is exercised by the gate 3 contract test: scripts/test_radiographic_inspection.py against scripts/radiographic_inspection.py (stdlib unittest, offline). Run: python3 scripts/test_radiographic_inspection.py
Compliance
- Standards referenced, not reproduced: AS9100 clause 8.5.1.3 frames NDT as a special process requiring controlled procedures, qualified personnel, and records; the formulas and technique practice above are common RT methodology, summary-only per standards-map.yaml.
- compliance: STANDARDS-REF, gated: false.