1、BS ISO 15708-4:2017Non-destructive testing Radiation methods for computed tomographyPart 4: QualificationBSI Standards PublicationWB11885_BSI_StandardCovs_2013_AW.indd 1 15/05/2013 15:06BS ISO 15708-4:2017 BRITISH STANDARDNational forewordThis British Standard is the UK implementation of ISO 15708-4
2、:2017.The UK participation in its preparation was entrusted to Technical Committee WEE/46, Non-destructive testing.A list of organizations represented on this committee can be obtained on request to its secretary.This publication does not purport to include all the necessary provisions of a contract
3、. Users are responsible for its correct application. The British Standards Institution 2017.Published by BSI Standards Limited 2017ISBN 978 0 580 93363 9 ICS 19.100 Compliance with a British Standard cannot confer immunity from legal obligations.This British Standard was published under the authorit
4、y of the Standards Policy and Strategy Committee on 28 February 2017.Amendments/corrigenda issued since publicationDate T e x t a f f e c t e dBS ISO 15708-4:2017 ISO 2017Non-destructive testing Radiation methods for computed tomography Part 4: QualificationEssais non destructifs Mthodes par rayonne
5、ments pour la tomographie informatise Partie 4: QualificationINTERNATIONAL STANDARDISO15708-4First edition2017-02Reference numberISO 15708-4:2017(E)BS ISO 15708-4:2017ISO 15708-4:2017(E)ii ISO 2017 All rights reservedCOPYRIGHT PROTECTED DOCUMENT ISO 2017, Published in SwitzerlandAll rights reserved.
6、 Unless otherwise specified, no part of this publication may be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on the internet or an intranet, without prior written permission. Permission can be requested from either ISO at
7、the address below or ISOs member body in the country of the requester.ISO copyright officeCh. de Blandonnet 8 CP 401CH-1214 Vernier, Geneva, SwitzerlandTel. +41 22 749 01 11Fax +41 22 749 09 47copyrightiso.orgwww.iso.orgBS ISO 15708-4:2017ISO 15708-4:2017(E)Foreword iv1 Scope . 12 Normative referenc
8、es 13 Terms and definitions . 14 Qualification of the inspection . 14.1 General . 14.2 Qualification of defect testing 24.2.1 General 24.2.2 Quality feature . 24.2.3 Feature detectability/test system/system parameterisation . 24.2.4 Verification of suitability . 34.2.5 Consistency check . 34.2.6 Doc
9、umentation 44.3 Qualification of dimensional testing 44.3.1 General 44.3.2 Test and measurement task . 44.3.3 Dimensional testing/test system/system parameterisation . 44.3.4 Degree of accuracy . 54.3.5 Consistency check . 54.3.6 Documentation 55 Qualification of the CT system 65.1 General . 65.2 In
10、tegral overall system test 65.3 Checking the system components 65.3.1 General 65.3.2 Manipulation system 65.3.3 Image scale 65.3.4 Beam axis perpendicularity . 65.3.5 Tube focal spot . 75.3.6 Tube stability 75.3.7 Detector . 75.3.8 Reconstruction 75.3.9 Visualization 75.4 Documentation . 76 Example
11、of CT system resolution evaluation methods . 76.1 Pre-amble 76.2 Acquisition parameters . 86.3 Recommendations for creating reference objects 86.4 Density resolution measurement method. 96.4.1 General 96.4.2 High energy reference object 96.4.3 Low energy reference object . 96.4.4 Experimental measur
12、ements 9Bibliography .11 ISO 2017 All rights reserved iiiContents PageBS ISO 15708-4:2017ISO 15708-4:2017(E)ForewordISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The work of preparing International Standards is no
13、rmally carried out through ISO technical committees. Each member body interested in a subject for which a technical committee has been established has the right to be represented on that committee. International organizations, governmental and non-governmental, in liaison with ISO, also take part in
14、 the work. ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.The procedures used to develop this document and those intended for its further maintenance are described in the ISO/IEC Directives, Part 1. In particular t
15、he different approval criteria needed for the different types of ISO documents should be noted. This document was drafted in accordance with the editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).Attention is drawn to the possibility that some of the elements of this docu
16、ment may be the subject of patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of any patent rights identified during the development of the document will be in the Introduction and/or on the ISO list of patent declarations received (see www.iso.or
17、g/patents).Any trade name used in this document is information given for the convenience of users and does not constitute an endorsement.For an explanation on the meaning of ISO specific terms and expressions related to conformity assessment, as well as information about ISOs adherence to the World
18、Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT) see the following URL: www.iso.org/iso/foreword.htmlThis document was prepared by the European Committee for Standardization (CEN) (as EN 16016-4) and was adopted, under a special “fast-track procedure”, by Technical Commit
19、tee ISO/TC 135, Non-destructive testing, Subcommittee SC 5, Radiographic testing, in parallel with its approval by the national bodies of ISO. It takes into consideration developments in computed tomography (CT) and computational power over the preceding decade.A list of all parts in the ISO 15708 s
20、eries can be found on the ISO website.iv ISO 2017 All rights reservedBS ISO 15708-4:2017INTERNATIONAL STANDARD ISO 15708-4:2017(E)Non-destructive testing Radiation methods for computed tomography Part 4: Qualification1 ScopeThis document specifies guidelines for the qualification of the performance
21、of a CT system with respect to various inspection tasks.It is applicable to industrial imaging (i.e. non-medical applications) and gives a consistent set of CT performance parameter definitions, including how those performance parameters relate to CT system specifications. This document deals with c
22、omputed axial tomography and excludes other types of tomography such as translational tomography and tomosynthesis.2 Normative referencesThe following documents are referred to in the text in such a way that some or all of their content constitutes requirements of this document. For dated references
23、, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.ISO 15708-2, Non-destructive testing Radiation methods for computed tomography Part 2: Operation and interpretation3 Terms and definitionsFor the purposes of thi
24、s document, the terms and definitions given in ISO 15708-1 apply.ISO and IEC maintain terminological databases for use in standardization at the following addresses: IEC Electropedia: available at http:/www.electropedia.org/ ISO Online browsing platform: available at http:/www.iso.org/obp4 Qualifica
25、tion of the inspection4.1 GeneralCT is used in industry both for defect testing and dimensional testing and measurement. Since CT does not directly provide measurement of desired quantities such as, for example, pore size or wall thickness, these quantities must be derived from the X-ray linear atte
26、nuation data represented by the CT grey values. The detectability of features and the degree of accuracy required depend on the inspection task, the specification of the available test equipment and the analysis and evaluation methods used. When determination of such quantities is required, a specia
27、l task-specific qualification test of the CT system is required. The qualification measures are described in 4.2 and 4.3. The qualification should be carried out by trained personnel. The trained personnel shall be able to prove they have undergone training and qualification in digital industrial ra
28、diography or radioscopy. ISO 2017 All rights reserved 1BS ISO 15708-4:2017ISO 15708-4:2017(E)4.2 Qualification of defect testing4.2.1 GeneralUnder test qualification, the suitability of the CT inspection technique for measuring a quantity to the required precision should be verified. The following s
29、teps described are typical of those for the successful verification of the suitability of CT for industrial applications.4.2.2 Quality featureTypical quantities to be measured are the sizes of pores, cavities, cracks, inclusions, contaminants as well as studies of the material distribution and the a
30、ssembly and installation position of components. Because the test sample and the type, position and size of the features to be detected determine the properties of a CT system to be used, information such as the following should be known:a) test object:1) dimensions;2) weight;3) materials;4) path le
31、ngth to be X-rayed in the material;b) test feature:1) type;2) position;3) size;4) distribution, frequency;c) feature detectability:1) limiting defect;2) limiting feature.Since the feature detectability strongly influences the specification and therefore the cost of a CT system, special attention mus
32、t be taken when defining the sensitivity of the tests required. If, due to missing information, no limiting values for features are defined, it is recommended that the best possible sensitivity is used for the specific method and CT system and the attained feature detectability is verified using, fo
33、r example, destructive tests.4.2.3 Feature detectability/test system/system parameterisationThe usability of the CT system and the selection of system parameters are determined by the requirements for feature detectability. Typical variables are:a) spatial resolution:1) overall spatial resolution of
34、 the CT image;2) scan geometry;3) detector spatial resolution;2 ISO 2017 All rights reservedBS ISO 15708-4:2017ISO 15708-4:2017(E)4) focal spot size of radiation source;b) contrast resolution:1) overall contrast resolution of the CT image;2) detector settings;3) tube voltage;4) tube current;c) recon
35、struction/visualization:1) number of projections;2) CT grey value dynamic range of the reconstruction or visualization;3) CT image size in X, Y and Z axes.CT system set-up and image quality parameters are described in ISO 15708-2:2016, 4.1 and 5.1.4.2.4 Verification of suitability4.2.4.1 GeneralA re
36、liable statement on the defect detection sensitivity and the defect detectability of the CT system used in a test shall be made by stating the degree of accuracy of the test required (tolerance, degree of fluctuation). Several alternative procedures are described in the following.4.2.4.2 Reference s
37、amples with natural defectsIf a reference sample with a known defect is available, inspection of this sample is carried out and the detectability is stated after the test has been done.If a reference sample with unquantified defects is available, inspection of this part is carried out and the defect
38、 detectability is stated using a counter-check, using, for example, a destructive test after the CT scan has been done.4.2.4.3 Reference sample with synthetic defectIf the test feature can be simulated using a synthetic defect, for example, a hole, the defect detectability verification can take plac
39、e similar to the previous section.4.2.4.4 Reference sample without specificationsIf no specifications are available for the reference sample status and a counter-check is not possible, the test is carried out using the system sensitivity. Sample structures like, for example, wall thicknesses and ext
40、ernal dimensional measurements can be used for estimating the defect detectability. Alternatively, reference samples like, for example, wires or spheres of known dimensions can be used.4.2.5 Consistency checkThe CT scan requires several very complex process steps for which the error sources cannot a
41、lways be excluded. After the scan, the following can be used to trace the possible error sources: reconstruction: size, CT slice positions, possible artefacts ; CT image scale; ISO 2017 All rights reserved 3BS ISO 15708-4:2017ISO 15708-4:2017(E) sinogram (CT grey value and curve progress) or CT proj
42、ection sequence (comparison between projections, image quality of the projections, intensity changes); system status (error messages).Where errors occur, either they shall be corrected or their causes shall be eliminated and the test repeated.4.2.6 DocumentationIn the qualification report, the relev
43、ant parameters and results of the qualification steps are to be described and presented. The CT images are to be archived for a period which is to be agreed with the end-user. The test parameters are to be archived so that an identical test procedure is possible in the case of recurrent test parts a
44、nd features.4.3 Qualification of dimensional testing4.3.1 GeneralCT inspection provides information about the 3D structure of a sample from which surface and geometry data can be derived. Because these data are based on X-ray-physical absorption differences at the contour transitions, small differen
45、ces in measured values may arise compared to classical tactile or optical measuring procedures. In the following sections, those CT scan parameters which influence the results will be described, together with those process steps which affect the accuracy of the results.4.3.2 Test and measurement tas
46、kDimensional measurement tasks include the measurement of single dimensions in the test object, wall thickness measurements, surface extraction, volume extraction or nominal-actual comparisons. The required measurement precision is to be defined for every task and if necessary for different parts of
47、 the sample.4.3.3 Dimensional testing/test system/system parameterisationThe degree of accuracy attainable depends on the test object, the limitations of X-ray physics and the subsequent data handling. An initial estimation of the degree of accuracy of a CT-based dimensional measurement can take pla
48、ce with the following parameters:a) spatial resolution in the test object:1) dimensions;2) geometric magnification, voxel size;3) detector resolution;4) focal spot;b) X-ray penetration of test object:1) material;2) maximal wall thickness to be X-rayed;3) contrast resolution;c) 3D component data:1) o
49、riginal CT image voxel size;2) extraction steps and quality;4 ISO 2017 All rights reservedBS ISO 15708-4:2017ISO 15708-4:2017(E)3) further processing steps and quality;4) registration method.For this estimation, it must be noted that -physical X-ray effects (like scattered radiation and beam hardening) as well as artefacts due to the detector and reconstruction method can lead to strongly varying degrees of accuracy in different parts of the sample. For a known measuring point, the local- parameters should be used.The inspection task
