Slide 1

Nondestructive testing (NDT) Liquid / Dye penetrant testMagnetic particle testEddy current testRadiographyUltrasonic testAcoustic emission test

Also called NDE / NDI: purpose to detect & assess flaws in a component without affecting its usefulness. 1Radiation sourceX ray Deceleration of high energy electron (eV)Gamma rayRadioactive elements

Continuous spectrum, white radiation, bremsstrahlung (German term means: braking rays)Characteristic radiationIlUnlike X-ray gamma rays are emitted as discrete energy levels

Effect of parallel & divergent beamDivergent beam responsible for un-sharpnessProjection radiography setup

Fully dark region: umbraPartially dark region: penumbraUn-sharpness: min separation distance that can be resolvedFactors affecting un-sharpness of radiographGeometrical un-sharpness (Ug)Scattering un-sharpness (Us)Movement un-sharpness (Um)Inherent or film un-sharpness (Uf)Film processing un-sharpnessUm is negligible if film & object are stationary. Us depends on absorption coefficient.

Geometric un-sharpness (Ug)ABCABCOxDensityUgsab

7RadiographyDSTest pieceFilmX Ray SourceDirect beam forms image. Scattered rays fog the film.ID = Image forming radiationIS = Non image forming radiationIntensity of the beam forming the image of the defect = ID + ISBuild up factor= (ID + IS) / ID8Experimental setup to estimate build up factor

Narrow beam: no contribution from IS. Broad beam: records both IS & ID. Build up factor = (1 + IS/ID)Effect of beam geometry & thickness on exposure

The difference in exposure for the same thickness between narrow beam & broad beam is a measure of build up factorEffect of radiation & thickness on build up factor

Radiographic film: AgBr

D= Photographic densityIi = Incident beam intensityIt = transmitted beam intensityE = ExposureI = Beam intensityt = timeDLog10 EfDmax ~10-15Fog level ~ 0.2

Contrast2Radiography: G = f(D)GD0417Fine grain filmMedium grain filmS: speed a measure of exposure giving reasonable darkening . No internationally accepted standard of specifying film speed

SummaryFactors affecting quality of radiographMain diff between x-ray & gamma rayProjection setupGeometrical un-sharpnessBuild up factor (scattering)Film characteristic