ASTM E1496-2005 Standard Test Method for Neutron Radiographic Dimensional Measurements《中子射线摄影尺寸测量的标准试验方法》.pdf

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1、Designation: E 1496 05Standard Test Method forNeutron Radiographic Dimensional Measurements1This standard is issued under the fixed designation E 1496; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A nu

2、mber in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method provides a technique for extractingquantitative dimensional information on an object from itsneutron radiograph. The te

3、chnique is based on the identifica-tion of changes in film density caused by material changeswhere a corresponding discontinuity in film density exists.Thistest method is designed to be used with neutron radiographsmade with a well-collimated beam. The film densities in thevicinity of the edge must

4、be in the linear portion of the densityversus exposure curve. The accuracy of this test method maybe affected adversely in installations with high-angular-divergence neutron beams or with large object-to-film dis-tances.1.2 This standard does not purport to address all of thesafety concerns, if any,

5、 associated 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:2E94 Guide for Radiographic ExaminationE 543 Practice

6、 for Agencies Performing NondestructiveTestingE 748 Practices for Thermal Neutron Radiography of Ma-terialsE 803 Method for Determining the L/D Ratio of NeutronRadiography BeamsE 1316 Terminology for Nondestructive Testing2.2 Other Documents:SNT-TC-1A Recommended Practice for NondestructiveTesting P

7、ersonnel Qualification and Certification3ANSI/ASNT CP-189 ASNT Standard for Qualification andCertification of Nondestructive Testing Personnel3NAS-410 Nondestructive Testing Personnel Qualificationand Certification43. Terminology3.1 DefinitionsDefinitions of the many terms relative toradiography (fo

8、r example, X, gamma, and neutron radiogra-phy) can be found in Terminology E 1316.3.2 Definitions of Terms Specific to This Standard:3.2.1 extremumthe point on the linear response portion ofthe curve of smoothed density versus location at which theslope is a maximum.3.2.2 extremum slope criterionthe

9、 criterion that specifiesthe edge of a discontinuity or an object, located at the spatialposition corresponding to the extremum as determined fromexamination of a radiograph.3.2.3 linear responsea radiographic response where thefilm density across an edge within an object is contained in thelinear p

10、art of the density versus exposure curve.3.2.4 traveling-stage microdensitometera densitometerwith a small aperture (typically between 10 to 25 m by 200 to300 m) that has the capability of scanning a radiograph in acontinuous or stepped manner and generating either a digital oran analog mapping of t

11、he film density of the radiograph as afunction of position.1This test method is under the jurisdiction of ASTM Committee E07 onNondestructive Testing and is the direct responsibility of Subcommittee E07.05 onRadiology (Neutron) Method.Current edition approved June 1, 2005. Published June 2005. Origi

12、nallyapproved in 1992. Last previous edition approved in 1997 as E 1496 - 97.2For 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 ont

13、he ASTM website.3Available from TheAmerican Society for Nondestructive Testing (ASNT), P.O.Box 28518, 1711 Arlingate Ln., Columbus, OH 43228-0518.4Available from Aerospace Industries Association of America, Inc. (AIA), 1250Eye St., NW, Washington, DC 20005.FIG. 1 Typical Microdensitometer Film Densi

14、ty Traces Associatedwith Three Rectangular Material Discontinuities: (a) Edge ofObject, (b) Thickness Variation, and (c) Dissimilar MaterialBoundary1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.4. Summary of Test Method4.1 All radi

15、ation used in radiography is attenuated in itspassage through an object according to its thickness andmagnitude of the material attenuation properties appropriate tothe type and energy of radiation. Additionally, significantspatial spreading occurs due to the system imperfections,nonsymmetric radiat

16、ion transport, and image formation pro-cess. Significant variations in the recorded radiation near edgesand material discontinuities therefore occur and manifestthemselves by film density variations in the radiograph, asillustrated in Fig. 1.4.2 A graph of detector response (film density) versusloca

17、tion across an interface is similar in form for manydifferent types of interface, provided that the detector respondslinearly to increased exposure over the entire region of interest.Typical radiographic responses are shown in Fig. 2 (a) and (b).4.3 Both theoretical and experimental studies in neutr

18、onradiography have established that under commonly encoun-tered high-quality linear-response radiographic conditions, theedge of an object corresponds to that point on the smoothedexperimentally obtained microdensitometer trace at which theslope is a maximum, as illustrated in Fig. 3. This point is

19、calledthe extremum, and the relationship between the spatial positionof the extremum and location of the edge is called theextremum slope criterion. These have been confirmed bycareful experimentation (1-3).55. Significance and Use5.1 Many requirements exist for accurate dimensional in-formation in

20、industrial quality control. Frequently, this infor-mation cannot be measured directly, may be very uncertain, oris expensive to obtain. If a radiograph of the object in questiondisplays a sufficient film density variation near the edge ofinterest, however, dimensional radiography methods may beappli

21、ed. This test method provides a technique for extractingquantitative dimensional information from the neutron radio-graph of an object. Guide E94and Practices E 748 are helpfulfor understanding the principles involved in obtaining a high-quality neutron radiograph.5.2 Dimensional radiography appears

22、 to be particularlyrelevant in determination of the following: (1) diameters ofspent radioactive fuel, (2) gap sizes in contact-circuit mecha-nisms of shielded components, and (3) prescribed spacingsbetween distinct materials.5.3 While this test method addresses dimensional measure-ments using neutr

23、on radiography, the methods and techniquesof dimensional radiography are also equally applicable tovarious types of radiography, such as x-ray, g-ray, and neutron.5.4 Afundamental assumption of this test method is that theuser will have access to a system that permits the attainment ofdata describin

24、g the density response of the radiograph. Al-though a system may include any digitization equipmentcapable of providing the spatial resolutions recommended in6.1.1, a typical system will include a high-resolution traveling-stage microdensitometer and a neutron radiograph of theobject.5.5 An object w

25、ith accurately known dimensions must beavailable to calibrate the equipment used to measure theradiographic response, that is, the traveling-stage microdensi-tometer (or other digitization system capable of spatial resolu-tion comparable to that of the detector).6. Basis of Application6.1 The follow

26、ing items are subject to contractual agree-ment between parties using or referencing this test method.6.1.1 Personnel QualificationIf specified in the contrac-tual agreement, personnel performing examinations in accor-dance with this test method shall be qualified in accordancewith a nationally or i

27、nternationally recognized NDT personnelqualification practice or standard such asANSI/ASNT CP-189,SNT-TC-1A, NAS-410, or a similar document and certified bythe employer or certifying agency, as applicable. The practice5The boldface numbers in parentheses refer to the list of references at the end of

28、this test method.FIG. 2 Typical Microdensitometer Traces of Film Density for (a)Rectangular Objects and (b) Cylindrical Objects; NotePlacements of Edges x+and xon the TracesFIG. 3 Depiction of Various Slopes on a SmoothedMicrodensitometer Trace; The Object Edge Coordinate, x+,Corresponds to the Extr

29、emum Slope Point on the TraceE1496052or standard used and its applicable revision shall be specified inthe contractual agreement between the using parties.6.1.2 Qualification of Nondestructive AgenciesIf speci-fied in the contractual agreement, NDT agencies shall bequalified and evaluated as describ

30、ed in Practice E 543. Theapplicable revision of Practice E 543 shall be specified in thecontractual agreement.6.1.3 Procedures and TechniquesThe procedures andtechniques to be utilized shall be as specified in the contractualagreement.7. Apparatus7.1 In addition to the instruments and facilities nor

31、mallyused in radiography (refer to Guide E94and Practices E 748),dimensional radiography relies critically on the use of ahigh-resolution traveling-stage (continuous or stepping) mi-crodensitometer or digitization system. The purpose of themicrodensitometer is to obtain a quantitative trace or digit

32、alsequence of the film density along a specified traverse of theradiograph. Two features are of particular importance:7.1.1 The aperture for light passing through the film must benarrow enough to respond accurately to the macroscopicproperties of the film density, but not so narrow as to introduceex

33、cessive microscopic film noise. An aperture width between10 and 20 m along the direction of the traverse, and between200 and 300 m in the perpendicular direction, is recom-mended for typical applications (4).7.1.2 It is required that the response of the microdensitom-eter be linear or that data exis

34、t to correct its nonlinearity. Suchdata can be obtained by scanning either a neutron radiograph ofan object with a known and uniform composition or calibratedfilm step wedges (see Section 8).8. Calibration of Microdensitometer8.1 No specific calibration procedures are provided becausethe calibration

35、 of each traveling-stage microdensitometer de-pends on its type and model. However, several general proce-dural steps are common to the calibration of all of themicrodensitometers used in this test method.8.2 A calibration procedure must exist that transforms thedimension scale on the strip-chart re

36、cord of the microdensito-meter trace, or pixel dimensions and intervals for a digitizeddata set, to the true physical dimension of a test object. Theprocedure should permit periodic checking.8.3 It is required that the density response of the microden-sitometer be linear or that data exist to correc

37、t its nonlinearity.8.3.1 Obtain a density trace from a neutron radiograph of anobject that covers the range from 0 to 4.0 density units.Calibrated film step wedges are commercially available andcan be used for this purpose.8.3.2 Check the microdensitometer data for a linear re-sponse between the obj

38、ect density and reported density values.8.3.3 If the density response is nonlinear, develop a correc-tion curve, table, or equation based on the object and responsedata.9. Procedure9.1 Obtain a neutron radiograph of the object under exami-nation.9.2 The dimensions of interest are deduced from the co

39、or-dinates of either individual edges of the object or edges ofmaterial discontinuities within the object. Hence, it is neces-sary to describe only the methodology of determining themaximum film density slope on a radiograph for an edge ofinterest, that is, the extremum.9.2.1 Identify the region for

40、 the traverse of interest from avisual examination of the radiograph.9.2.2 Obtain a high-quality continuous or digital microden-sitometer trace along the traverse, ensuring that the travelingstage is set for a speed or pixel dimension that scales the filmdensity variation in the vicinity of the edge

41、 adequately (refer to7.1.1).9.2.3 Determine the point on the smoothed microdensitom-eter trace at which the slope is maximum by either visual orcomputer-based means, and obtain the corresponding edgecoordinate x+from this, as shown in Fig. 3.9.2.3.1 Note that if visual methods do not permit a decisi

42、vedetermination of the extremum, algebraic-fitting and subse-quent analytic techniques must be used. Studies of knife-edgeshave shown that edge location is insensitive to the functionalform used in the smoothing technique (5-7).9.2.3.2 It is critical to ensure that the film densities obtainedexperim

43、entally in the vicinity of the edge are in the linearportion of the density versus exposure curve (see 4.2). This isparticularly important for curved edges where, as suggested inFig. 2 (b), the extremum slope coordinate corresponds to filmdensity close to the maximum density on the radiograph. (Ther

44、eason for this care is the potential interference with theedge-scattering distortion process (8).)9.2.4 Repeat the steps given in 9.2.1-9.2.3 for the compan-ion edge of interest to identify the edge coordinate x.10. Calculation10.1 The difference (x+x) corresponds to the separationof edges on the mi

45、crodensitometer trace, referred to as the tracespacing.10.2 Use the calibration curve, table, or equation developedin Section 8 to convert the trace spacing to the separationdimension of the edges.11. Precision and Bias611.1 PrecisionThe precision of this test method has beendetermined at several la

46、boratories.11.1.1 Test results obtained in the same laboratory (repeat-ability conditions) yielded errors averaging under 25 m.11.1.2 Test results obtained in different laboratories (repro-ducibility conditions) yielded errors that were always below100 m and averaged 25 m.11.2 BiasSystematic errors

47、might arise if adequate care isnot exercised in obtaining the extremum slope (see 9.2.3).11.3 General ConsiderationsThe above assumes a well-collimated neutron beam with an L/D ratio greater than 100, asdetermined using Method E 803, and divergence half-angleless than two degrees.6Supporting data ha

48、ve been filed atASTM headquarters and may be obtained byrequesting RR:E07-1001.E149605311.3.1 For installations in which the beam is highly diver-gent, or the object-film distance is sufficiently large to create apenumbra shadowing affect, further complications appear thatcan affect the precision, o

49、r bias, or both.11.3.2 Effects of the extended dimensions of the object andneutron radiographic facility can be taken into account if somedetails of the edge of the object are known. However, thesecorrections are not straightforward unless the geometry of theobject is simple.11.3.3 The precision and bias of any particular object shouldbe determined by multiple test measurements of an object thatare similar to the actual object in both geometry and compo-sition. It should be anticipated that variations in both precisionand bias will be greater than those stated in 1