1、Designation: E242 15Standard Reference Radiographs forAppearances of Radiographic Images as Certain Parametersare Changed1This standard is issued under the fixed designation E242; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the
2、 year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope*1.1 This document describes the appearance of a radio-graphic image where fundamental components of image qual-i
3、ty are changed, that is, variables such as whether an X-ray orgamma ray source was used, the characteristics of the radio-graphic film (gradient, granularity, and developing conditions)and intensifying screens, and specimen thickness (the geo-metrical configuration of the radiographic set-up and foc
4、al spotsize both affect image quality but are not considered in thereference radiographs).1.2 The X-ray film systems used in obtaining the illustrativedata were as follows: Very Fine Grain (comparable to class I ofTest Method E1815) and Fine Grain (comparable to class II ofTest Method E1815).1.3 The
5、se reference radiographs2consist of four compositeillustrations3and show how such factors as radiation energy,specimen thickness, and film properties affect the radiographicimage. The reference radiograph films are an adjunct to thisdocument and must be purchased separately from ASTM ifneeded.1.4 Th
6、e values stated in inch-pound units are to be regardedas standard. The values given in parentheses are mathematicalconversions to SI units that are provided for information onlyand are not considered standard.1.5 This standard does not purport to address all of thesafety concerns, if any, associated
7、 with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:4E94 Guide for Radiographic ExaminationE746 Practice for Determi
8、ning Relative Image Quality Re-sponse of Industrial Radiographic Imaging SystemsE1316 Terminology for Nondestructive ExaminationsE1735 Test Method for Determining Relative Image Qualityof Industrial Radiographic Film Exposed to X-Radiationfrom4to25MeVE1815 Test Method for Classification of Film Syst
9、ems forIndustrial Radiography2.2 ASTM Adjuncts:Reference Radiographs for Appearances of RadiographicImages as Certain Parameters Are Changed33. Terminology3.1 Definitions: For definitions of terms used in thisdocument, see Terminology E1316, Section D.4. Significance and Use4.1 A key consideration w
10、ith any radiographic system is itscontrast resolution and spatial resolution capability (that is,sensitivity). The degree of obtainable sensitivity with a givensystem is dependent upon several radiographic parameters suchas source energy level, film system class, type and thickness ofintensifying sc
11、reens, and material thickness radiographed.These reference radiographs permit the user to estimate thedegree of sensitivity change that may be obtained when theseparameters are varied from a specific technique. This standardmay also be used in conjunction with Test Method E1815 orwith Practice E746
12、or Test Method E1735 to provide a basis fordeveloping data for evaluation of a users specific system. Thisdata may assist a user in determining appropriate parametersfor obtaining desired degrees of radiographic system sensitiv-ity.1These reference radiographs are under the jurisdiction of ASTM Comm
13、itteeE07 on Nondestructive Testing and is the direct responsibility of SubcommitteeE07.02 on Reference Radiological Images.Current edition approved June 1, 2015. Published June 2015. Originallyapproved in 1964. Last previous edition approved in 2010 as E242 - 01 (2010). DOI:10.1520/E0242-15.2For ASM
14、E Boiler and Pressure Code applications see related ReferenceRadiographs SE-242 in the Code.3Available from ASTM Headquarters. Order RRE0242.4For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volu
15、me information, refer to the standards Document Summary page onthe ASTM website.*A Summary of Changes section appears at the end of this standardCopyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States15. Factors Affecting Radiographic Appeara
16、nce5.1 The final interpretation of the radiograph is greatlyaffected by the appearance of a discontinuity. A poor techniquecan minimize the radiographic appearance of a discontinuityand conversely the optimum technique can emphasize thisappearance. The appearance of a radiographic image is affectedm
17、ainly by:5.1.1 X-ray or gamma ray energy.5.1.2 Section thickness,5.1.3 Unsharpness,5.1.4 Film and screen combinations, and5.1.5 Film system class.5.2 An equation that considers most of the above factors(excluding unsharpness) is:x 5cd12 d2!/G#kx11! (1)where:x = thickness of discontinuity,c = constan
18、t,d1d2= minimum density change perceptible by eye,G = film gradient, = linear absorption coefficient (effective),k = scattering coefficient, andx = section thickness.The minimum density change, perceptible by eye, dependson the film system class used, the geometric unsharpness, andthe attenuation by
19、 the material. The thickness-dependent con-trast sensitivity, CS, in % (equivalent penetrameter sensitivity)of section thickness for 2T hole plate IQIs is described asfollows:CS% thickness5 PT x! 3 DUg! Geff!12(2)where:PT = constant perception threshold for human operators,D= film granularity,Ug = g
20、eometric unsharpness, andeff= /(kx+1).NOTE 1Gradient over granularity (G/D) increases by a factor of threefrom film class III to Special Class (see Test Method E1815). The contrastsensitivity improves by 1.7.As the above equations show, the minimum thickness ofdetectable discontinuity (x or CS) is:5
21、.2.1 A function of X-ray energy and scatter,5.2.2 A function of section thickness,5.2.3 An inverse function of film gradient and attenuationcoefficient, and5.2.4 A function of the film system class and geometricunsharpness.5.3 These reference radiographs do not consider the effectsof unsharpness oth
22、er than due to specimen thickness.6. Radiographic Illustrations6.1 A series of 36 radiographs, each on 10-in. by 12-in.254-mm by 305-mm film, were taken of a 12-in. by 12-in.305-mm by 305-mm welded steel plate which containeddiscontinuities in the weld. These were taken to illustrate thedifferences
23、in appearance of the radiographic image whentechniques for taking radiographs are varied by changing thefactors listed in Section 5. Technique data for each radiographis in Table 1. A 2-in. by 2-in. 51-mm by 51-mm area, whichincludes the identical image of the discontinuities in the weld,was selecte
24、d and cut out from each 10-in. by 12-in. 254-mmby 305-mm radiograph and arranged so as to make fourcomposite illustrations identified as Figures 1 through 4. TheseTABLE 1 Technique DataNOTE 1No radiographic geometry or focal spot size information is available.SourceLead ScreensComposite Illustration
25、Film NotesABC DSteel ThicknessFront, in. Back, in.1in.25 mm2in.51 mm4in.102 mm6in.152 mm150 kVp 0.005 0.005 x . . . Fine grain14 in. lead mask250 kVp 0.005 0.005 . x . . Fine grain14 in. lead mask1 MeVH0.0300.0300.0050.0100.0100.005x.xx.xx.x.x.Very fine grainFine grainFine grain.2 MeVH0.0300.0050.01
26、00.005xxxxxxxxVery fine grainFine grain.10 MeV 0.040 0.010 x x x x Fine grain .15 MeV 0.030 0.010 x x x x Very fine grain .Iridium 192H0.0050.0100.0100.010x.x.x.Fine grainFine grain.Cobalt-60 (212 Ci)H0.0050.0100.0100.010x.x.x.Fine grainFine grain.Cobalt-60 (1000 Ci) 0.010 0.010 . . x x Fine grain 0
27、.080 in. lead filterRadium-226 (250 mg) 0.010 0.010 x x x . Fine grain .E242 152composite illustrations are an abridged version of the original36 radiographs and serve as the reference radiographs for thisdocument. Following are brief descriptions of these figures.6.1.1 Figure 1Composite Illustratio
28、n A consists of cutouts from the 10 radiographs taken of the 1-in. 25-mm thickwelded steel plate.6.1.2 Figure 2Composite Illustration B consists of cutouts from the 10 radiographs taken of the welded steel plate,built up to 2 in. 51 mm in thickness.6.1.3 Figure 3Composite Illustration C consists of
29、cutouts from the 10 radiographs taken of the welded steel plate,built up to 4 in. 102 mm in thickness.6.1.4 Figure 4Composite Illustration D consists of cutouts from the 6 radiographs taken of the welded steel plate,built up to 6 in. 152 mm in thickness.6.2 The radiographic appearance of discontinui
30、ties in 1, 2,4, and 6-in. 25-mm, 51-mm, 102-mm, and 152-mm thicksteel is shown in the series of composite radiographs. (Theseare full-scale reproductions of the same selected area from allthe reference radiographs.) All composite sets of radiographsshow the change in radiographic appearance in the s
31、pecifiedthickness of steel plate as the parameters of X-ray or gammaray energy and film systems or both are changed.6.3 Film DeteriorationRadiographic films are subject towear and tear from handling and use. The extent to which theimage deteriorates over time is a function of storageconditions, care
32、 in handling and amount of use. Referenceradiograph films are no exception and may exhibit a loss inimage quality over time. The radiographs should therefore beperiodically examined for signs of wear and tear, includingscratches, abrasions, stains, and so forth. Any reference radio-graphs which show
33、 signs of excessive wear and tear whichcould influence the interpretation and use of the radiographsshould be replaced.7. Use of the Reference Radiographs7.1 As radiation energy increases, the radiographic appear-ance of a given discontinuity becomes less distinct because ofthe greater penetration o
34、f the radiation; that is, because ofdecreasing subject contrast. The reference radiographs permit acomparison of the radiographic appearance of the weld, atparticular thickness over a range of X-ray or gamma rayenergies.7.2 Another condition that affects radiographic appearanceis the specimen thickn
35、ess for a given X-ray or gamma rayenergy. As the thickness of examined material is increased, adiscontinuity becomes less distinct in the radiographic image.This is due to two predominant factors:7.2.1 Focal spot size and the distances between focal spotand object and object and film produce unsharp
36、ness on thefilm.7.2.2 Scattered radiation within the material, which reducesthe radiographic contrast.7.2.3 The above processes are a function of material thick-ness and X-ray or gamma ray energy. This effect is illustratedin this document by the composite set of radiographs.8. Film and Screens8.1 T
37、he X-ray film systems used in obtaining the illustrativedata were as follows: Very Fine Grain (comparable to class I ofTest Method E1815) and Fine Grain (comparable to class II ofTest Method E1815). Comparisons of these two film systemsare illustrated in the composite radiographs and within Table 1.
38、8.2 Several different lead foil screen combinations wereused. The specific combination of lead foil screens for eachradiograph is noted in Table 1.9. Conclusions and Summary9.1 For a constant specimen thickness, the radiographicappearance of the discontinuities changes as the X-ray orgamma ray energ
39、y is varied.9.2 As the section thickness of specimen increases, theradiographic appearance of the discontinuities becomes lessdistinct, the radiation energy remaining constant.9.3 All other factors remaining constant, as the film ischanged from very fine grain (class I of Test Method E1815)tofine gr
40、ain (class II of Test Method E1815), the radiographicappearance of the discontinuities becomes less distinct.9.4 For specimens of uniform thickness, these data revealthat the most distinct radiographic appearance of the disconti-nuities occurs when the finest grain film and the lowest X-rayor gamma
41、ray energy is used, consistent with a given specimenthickness and practical exposure time.10. Keywords10.1 film systems; discontinuities; gamma rays; referenceradiographs; steel; unsharpness; welds; x-rayE242 153EXPLANATORY NOTESNOTE 1Total unsharpness factors such as source size, source-filmdistanc
42、e, screens, film graininess, etc., must be considered in establishingtechniques (Guide E94).NOTE 2It is not the intent of this document to limit the usefulness ofany source of radiation. The radiographs included in this document areillustrative and not intended to be either inclusive or conclusive.A
43、PPENDIX(Nonmandatory Information)X1. ADDITIONAL TECHNICAL INFORMATIONX1.1 Radiation source was centered over a drilled hole incenter of specimen (as seen in the 10 in. by 12 in. 254 mm by305 mm full-size reproduction). In 1 MV and 2 MVradiography, the radiation was projected towards the specimenthro
44、ugh the target, using a transmitted beam.X1.2 Radiographic exposure was such that the film densityin the radiograph at the center of a line connecting the imageof two drilled holes in the plate was between 1.90 and 2.10.X1.3 All films were developed using procedures recom-mended in Guide E94.X1.4 Go
45、od contact between film and screens was main-tained.SUMMARY OF CHANGESCommittee E07 has identified the location of selected changes to this standard since the last issue (E242) thatmay impact the use of this standard.(1) Added references.(2) Ensured SI units are included.(3) Made clear that radiogra
46、phic sensitivity is a function ofcontrast and spatial resolution.(4) Added discussion of radiographic geometry and focal spotsize affecting unsharpness.(5) Added film class and characteristics (gradient, granularity,and developing conditions) to Scope.(6) Added Eq. 2 and discussion.ASTM Internationa
47、l takes no position respecting the validity of any patent rights asserted in connection with any item mentionedin this standard. Users of this standard are expressly advised that determination of the validity of any such patent rights, and the riskof infringement of such rights, are entirely their o
48、wn responsibility.This standard is subject to revision at any time by the responsible technical committee and must be reviewed every five years andif not revised, either reapproved or withdrawn. Your comments are invited either for revision of this standard or for additional standardsand should be a
49、ddressed to ASTM International Headquarters. Your comments will receive careful consideration at a meeting of theresponsible technical committee, which you may attend. If you feel that your comments have not received a fair hearing you shouldmake your views known to the ASTM Committee on Standards, at the address shown below.This standard is copyrighted by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959,United States. Individual reprints (single or multiple copies) of
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