ASTM E1815-2008 Standard Test Method for Classification of Film Systems for Industrial Radiography《工业放射摄影胶片系统分类用标准试验方法》.pdf

1、Designation: E 1815 08Standard Test Method forClassification of Film Systems for Industrial Radiography1This standard is issued under the fixed designation E 1815; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last re

2、vision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers a procedure for determinationof the performance of film systems used for industrial radiog-raphy. Thi

3、s test method establishes minimum requirements thatcorrespond to system classes.1.2 This test method is to be used only for direct exposure-type film exposed with lead intensifying screens. The perfor-mance of films exposed with fluorescent (light-emitting) inten-sifying screens cannot be determined

4、 accurately by this testmethod.1.3 The values stated in SI units are to be regarded asstandard. The values given in parentheses are for informationonly.1.4 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of thi

5、s 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:2E94 Guide for Radiographic ExaminationE 999 Guide for Controlling the Quality of Industrial Ra-diographic Film Processin

6、gE 1079 Practice for Calibration of Transmission Densitom-etersE 1316 Terminology for Nondestructive Examinations2.2 ANSI Standards:3IT2.40 Root Mean Square (rms) Granularity of Film (Im-ages on One Side Only) Method of Measuring2.3 ISO Standards:3ISO 5-2 Photography Density MeasurementsPart 2: Geo-

7、metric Conditions for Transmission DensityISO 5-3 Photography Density MeasurementsPart 3:Spectral ConditionsISO 7004 PhotographyIndustrial Radiographic Film, De-termination of ISO Speed and Average Gradient WhenExposed to X and Gamma RadiationISO 11699-1 Non-Destructive TestingIndustrial Radio-graph

8、ic FilmPart 1: Classification of Film Systems forIndustrial RadiographyISO 11699-2 Non-Destructive TestingIndustrial Radio-graphic FilmPart 2: Control of Film Processing byMeans of Reference Values2.4 DIN Standard:3EN 584-1 Non-Destructive TestingIndustrial Radio-graphic FilmClassification of Film S

9、ystems3. Terminology3.1 DefinitionsFor definitions of terms used in this testmethod, refer to Terminology E 1316.3.2 Definitions of Terms Specific to This Standard:3.2.1 characteristic curve, ncurve showing the relation-ship between the common logarithm of exposure logK, and theoptical density D.3.2

10、.2 diffuse densityquantitative measure of film blacken-ing (optical density) as determined by a densitometer. It is thesum of all transmitted and scattered light into the half spherebehind the film.3.2.3 film gradient Gthe slope of the characteristic curveat a specified optical density, D, and a mea

11、sure of the contrastof the film system.3.2.4 film systemthe film and associated film-processingrequirements in accordance with the criteria established by themanufacturers of the film and processing chemicals.3.2.5 film system classclassification taking into account oflimiting values given in Table

12、1.3.2.6 gradient/noise ratioratio of the gradient G and thegranularity sD. It relates directly to the signal/noise ratio. Allfurther parameters determining the signal, such as the modu-lation transfer function or the energy of the radiation, areconsidered to be constant.1This test method is under th

13、e jurisdiction of ASTM Committee E07 onNondestructive Testing and is the direct responsibility of Subcommittee E07.01 onRadiology (X and Gamma) Method.Current edition approved July 1, 2008. Published August 2008. Originallyapproved in 1996. Last previous edition approved in 2006 as E 1815 - 06.2For

14、referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3Available from American National Standards Institute (ANSI), 25 W

15、. 43rd St.,4th Floor, New York, NY 10036, http:/www.ansi.org.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.3.2.6.1 DiscussionThe limiting values given in this stan-dard are related to fixed radiation energies and specifiedscreens.3

16、.2.7 granularity, sDstochastic fluctuation in a radio-graphic image, superimposed on the image of the object andtypically caused by random, statistical groupings of individualsilver particles in processed film.3.2.8 ISO speed Sreciprocal value of the dose KSmea-sured in Gray, which results in a spec

17、ified diffuse opticaltransmission density D D0= 2 on the processed film, whereD0is the fog and base density:S 51KS(1)3.2.9 signal/noise ratioin industrial radiography the ratioof a local film density to the granularity sDat this density level.It is correlated to the gradient/noise ratio.3.2.10 specu

18、lar densityquantitative measure of filmblackening (optical density) when light passing the optics of amicrodensitometer transmits the film.4. Significance and Use4.1 This test method provides a relative means for classifi-cation of film systems used for industrial radiography. The filmsystem consist

19、s of the film and associated processing system(the type of processing and processing chemistry). Section 9describes specific parameters used for this test method. Ingeneral, the classification for hard X-rays, as described inSection 9, can be transferred to other radiation energies andmetallic scree

20、n types, as well as screens without films. Theusage of film system parameters outside the energy rangesspecified may result in changes to a film/system performanceclassification.4.1.1 The film performance is described by contrast andnoise parameters. The contrast is represented by gradient andthe no

21、ise by granularity.4.1.2 A film system is assigned a particular class if it meetsthe minimum performance parameters: for Gradient G atD D0= 2.0 and D D0= 4.0, and gradient/noise ratio atD D0= 2.0, and the maximum performance parameter:granularity sDat D = 2.0, and gradient/noise ratio atD D0= 2.0.4.

22、2 This test method describes how the parameters shall bemeasured and demonstrates how a classification table can beconstructed.4.3 Manufacturers of industrial radiographic film systemsand developer chemistry will be the users of this test method.The result is a classification table as shown by the e

23、xamplegiven in Table 2. Another table also includes speed data foruser information. Users of industrial radiographic film systemsmay also perform the tests and measurements outlined in thistest method, provided that the required test equipment is usedand the methodology is followed strictly.4.4 The

24、publication of classes for industrial radiographyfilm systems will enable specifying bodies and contractingparties to agree to particular system classes, which are capableof providing known image qualities. See 8.4.5 ISO 116991 and European standard EN 584-1 describethe same method for classificatio

25、n of film systems for industrialradiography, but its class definitions and number of classes donot align exactly with this test method. International users ofthese standards should be aware of these differences for theirparticular applications.NOTE 1ASTM research report E071005 contains documentatio

26、n ofTABLE 1 Limiting Values for Gradient, Gradient/Granularity Ratio, and GranularityASTMSystemClassMinimum Gradient G at MinimumGradient/GranularityRatio, G/sD,at D =2.0above DoMaximumGranularity,sD,atD =2.0above DoD =2.0above DoD =4.0above DoSpecial 4.5 7.5 300 0.018I 4.1 6.8 150 0.028II 3.8 6.4 1

27、20 0.032III 3.5 5.0 100 0.039W-A 3.8 5.7 135 0.027W-B 3.5 5.0 110 0.032W-C 4 and need careful calibration correction in the full range. Smalldeviations of the density values at D 4 have considerable influence to theaccuracy of the G at D D0= 4 value due to the properties of thepolynomial approximati

28、on procedure.7.2.3 The mean gradient values shall be determined with amaximum uncertainty of 65 % for the gradient at D = 2 abovefog and base (G2) at a confidence level of 95 % and 67 % forthe gradient at D = 4 above fog and base (G4) at a confidencelevel of 95 %.7.2.4 Measurement laboratories, whic

29、h certify film systems,shall participate in a proficiency test on a periodical basis. Anew film, exposed in accordance with this standard, shall beused in all participating laboratories and for each periodicaltest.7.3 Measurement of Granularity sD7.3.1 The granularity is measured by linear or circul

30、arscanning of a film of constant diffuse optical density with amicrodensitometer. Both emulsion layers shall be recorded;this means that the depth of focus of the microdensitometer hasto include both layers.7.3.2 The granularity value shall be determined in terms ofdiffuse density.7.3.3 If the optic

31、al density is measured as specular density,it shall be converted into diffuse optical density, using the plotof the curve of diffuse density versus specular density at themean density value of the granularity film specimen. Thediffuse density of each step shall be measured with thecalibrated densito

32、meter.7.3.4 Determine this curve using a film having a steppedseries of densities, which is prepared using the same type offilm, exposure, and processing techniques as used for thegranularity film specimen. The specimen film shall be scannedusing identical microdensitometer settings. A limited range

33、 ofdensities can typically be measured for a given microdensito-meter gain setting.7.3.5 The stepped series of densities shall lie within thatrange.7.3.6 The calibration shall be made from the diffuse vsspecular density plot with at least five values between diffusedensity 1.5 and 2.8 (including fog

34、 and base). The conversioncan be performed on basis of a linear regression analysis of thelog (diffuse density) vs. log(specular density) plot. The deter-mined coefficients shall be used for the conversion of thespecular density into diffuse density values.7.3.7 The conversion shall be performed bef

35、ore the numeri-cal determination of the standard deviation sD, which is ameasure of the granularity. sDis calculated by:sD51N 1(i 5 1NDi D!2(3)7.3.8 The diffuse optical density of the measured film shallbe above fog and base. The determined sDvalue shall becorrected on the basis of the diffuse mean

36、density above fogand base of this film. The corrected sD-value is calculated by:sDcorr5sD =2/D (4)7.3.9 As an alternative, three or more samples of the filmspecimen at different density levels, within the range from 1.80to 2.20, may be measured, and the granularity value at a diffusedensity of 2.00,

37、 above base plus fog, shall be taken from alinear regression analysis of the plot of granularity as afunction of the square root of diffuse density above fog andbase.7.3.10 The scanning length on the radiographic film shall beat least 116 mm. The diameter of a circular measuring apertureof the micro

38、densitometer shall be (100 6 5) m. A squareaperture of 88.6 m by 88.6 m has the same area as a circularone of 100 m diameter and is concerning the measuredgranularity equivalent to a circular one with 100 m diameter.7.3.11 The determined sD-corr-valueshall be corrected on thebasis of the real (measu

39、red) aperture diameter Ad(in m) of acircular aperture. The corrected sD-value is calculated by:sDcorra 5sDcorr Ad/100! (5)7.3.12 If a square aperture of the microdensitometer is used,the corrected sD-value is calculated by:sDcorrb 5sDcorr =4Aa/p 10000! (6)where Aais the aperture area in m2.7.3.13 Th

40、e scan path of the microdensitometer may belinear or circular. If circular, the radius of the path shall not beless than 16 mm. In either case, the total scan length shall notbe less than 116 mm.7.3.14 In order to limit the low frequency noise the data,measured with the microdensitometer, shall be f

41、iltered afterconversion to diffuse density with a highpass filter with acut-off spatial frequency of 0.1 line pairs per millimetre (3 dB).This shall be performed by subtraction of the measured scanE1815084values minus the smoothed measured scan values. The smooth-ing shall be performed by convolutio

42、n with a rectangularwindow function with a width of 6.0 mm (61 values with 0.1mm distance). The scanning step width shall be 100 m in thatcase. The first and last 30 data points of the scan shall not beused after filtering for the further calculation of sD. The filteris based on the following formul

43、a:Difilter5 Dimeas161(j 5 3030Di 1 jmeas(7)7.3.15 Due to the risks of errors in the measured data duringthe scan, resulting from artifacts in the film such as dust andother sources of distortion, the filtered scan shall be dividedinto n groups of 1.9 mm length (20 values with 0.1 mmdistance) and 0.1

44、 mm distance between groups. sDglshall bedetermined for each group, whereby at least 55 groups shall beused. The calculated sDglvalues are rearranged in dependenceon their size and the central value (this is the 28thvalue in caseof 55 groups) is the MEDIAN of all groups. The median valuesDMshall be

45、multiplied with 1.0179 to get the median unbiasedestimation sD.NOTE 3k is the number of consecutive observations within a groupand C is the critical value of the chi-square distribution for s = 0.5 withk 1 degrees of freedom. For the sDestimation the median value sDMshall be multiplied by sqrt(k 1)/

46、C). In case of 20 observations themedian value sDMshall be multiplied with 1.0179 for statistical correc-tion.NOTE 4An increased number of data points and groups yields a better(lower) uncertainty of the result. It is important not to modify the grouplength of 1.9 mm (plus 0.1 mm distance between gr

47、oups) and thestatistical correction if using 1.0179 as correction value.7.3.16 Subdivision of the scanned data in groups, determi-nation of sDgland median procedure have an inherent filtereffect which is equivalent to the described highpass filter ofscanned data. Therefore, the highpass filtering ma

48、y be omitted,if the MEDIAN procedure is applied. Differences in thedetermined granularity will be less than 61.5 %.7.3.17 At least six measurements shall be made on differentsamples to estimate the mean value of granularity. The deter-mined granularity mean value shall not exceed an uncertaintyof 61

49、0 % at a confidence level of 95 %.7.3.18 Measurement laboratories, which certify film sys-tems, shall participate in a proficiency test on a periodicalbasis. A new film, exposed in accordance with this standard,shall be used in all participating laboratories and for eachperiodical test.7.4 Measurement of ISO Speed SThe ISO Speed S isevaluated for an optical density, D = 2.0, above fog and base,Do. Use Table 3 for determination of the ISO speed.8. Limiting Values for Classification8.1 The film system classes