ASTM E1814-14(2022)
(Practice)Standard Practice for Computed Tomographic (CT) Examination of Castings
Standard Practice for Computed Tomographic (CT) Examination of Castings
SIGNIFICANCE AND USE
4.1 CT may be performed on an object when it is in the as-cast, intermediate, or final machined condition. A CT examination can be used as a design tool to improve wax forms and moldings, establish process parameters, randomly check process control, perform final quality control (QC) examination for the acceptance or rejection of parts, and analyze failures and extend component lifetimes.
4.2 The most common applications of CT for castings are for the following: locating and characterizing discontinuities, such as porosity, inclusions, cracks, and shrink; measuring as-cast part dimensions for comparison with design dimensions; and extracting dimensional measurements for reverse engineering.
4.3 The extent to which a CT image reproduces an object or a feature within an object is dictated largely by the competing influences of spatial resolution, contrast discrimination, the specific geometry and material of the object itself, and artifacts of the imaging system. Operating parameters strike an overall balance between image quality, examination time, and cost.
4.4 Artifacts are often the limiting factor in CT image quality. (See Practice E1570 for an in-depth discussion of artifacts.) Artifacts are reproducible features in an image that are not related to actual features in the object. Artifacts can be considered correlated noise because they form repeatable fixed patterns under given conditions yet carry no object information. For castings, it is imperative to recognize what is and is not an artifact since an artifact can obscure or masquerade as a discontinuity. Artifacts are most prevalent in castings with long straight edges or complex geometries, or both.
SCOPE
1.1 This practice covers a uniform procedure for the examination of castings by the computed tomography (CT) technique. The requirements expressed in this practice are intended to control the quality of the nondestructive examination by CT and are not intended for controlling the acceptability or quality of the castings. This practice implicitly suggests the use of penetrating radiation, specifically X rays and gamma rays.
1.2 This practice provides a uniform procedure for a CT examination of castings for one or more of the following purposes:
1.2.1 Examining for discontinuities, such as porosity, inclusions, cracks, and shrink;
1.2.2 Performing metrological measurements and determining dimensional conformance; and
1.2.3 Determining reverse engineering data, that is, creating computer-aided design (CAD) data files.
1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.
1.4 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
General Information
Relations
Standards Content (Sample)
This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: E1814 − 14 (Reapproved 2022)
Standard Practice for
Computed Tomographic (CT) Examination of Castings
This standard is issued under the fixed designation E1814; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope* E1316 Terminology for Nondestructive Examinations
E1441 Guide for Computed Tomography (CT)
1.1 This practice covers a uniform procedure for the exami-
E1570 Practice for Fan Beam Computed Tomographic (CT)
nation of castings by the computed tomography (CT) tech-
Examination
nique.The requirements expressed in this practice are intended
E1672 Guide for Computed Tomography (CT) System Se-
to control the quality of the nondestructive examination by CT
lection
and are not intended for controlling the acceptability or quality
E1695 Test Method for Measurement of Computed Tomog-
of the castings. This practice implicitly suggests the use of
raphy (CT) System Performance
penetrating radiation, specifically X rays and gamma rays.
E1935 Test Method for Calibrating and Measuring CT
1.2 This practice provides a uniform procedure for a CT
Density
examination of castings for one or more of the following
E2339 Practice for Digital Imaging and Communication in
purposes:
Nondestructive Evaluation (DICONDE)
1.2.1 Examining for discontinuities, such as porosity,
E2767 Practice for Digital Imaging and Communication in
inclusions, cracks, and shrink;
Nondestructive Evaluation (DICONDE) for X-ray Com-
1.2.2 Performing metrological measurements and determin-
puted Tomography (CT) Test Methods
ing dimensional conformance; and 3
2.2 ASNT Documents:
1.2.3 Determining reverse engineering data, that is, creating
SNT-TC-1A Recommended Practice for Personnel Qualifi-
computer-aided design (CAD) data files.
cation and Certification in Nondestructive Testing
1.3 This standard does not purport to address all of the
ANSI/ASNT CP-189 Standard for Personnel Qualification
safety concerns, if any, associated with its use. It is the
and Certification of Nondestructive Testing Personnel
responsibility of the user of this standard to establish appro-
2.3 Military Standards:
priate safety, health, and environmental practices and deter-
NAS 410 Certification and Qualification of Nondestructive
mine the applicability of regulatory limitations prior to use.
Test Personnel
1.4 This international standard was developed in accor-
3. Terminology
dance with internationally recognized principles on standard-
ization established in the Decision on Principles for the
3.1 Definitions—Definitions of terms applicable to this
Development of International Standards, Guides and Recom-
practice may be found in Terminology E1316 and Guide
mendations issued by the World Trade Organization Technical
E1441.
Barriers to Trade (TBT) Committee.
3.2 Definitions of Terms Specific to This Standard:
3.2.1 fixturing—the mounting hardware used to place the
2. Referenced Documents
object in the CT system.
2.1 ASTM Standards:
3.2.2 scan plan—scan locations and the system configura-
E543 Specification for Agencies Performing Nondestructive
tion parameters for a specific part examination.
Testing
4. Significance and Use
4.1 CT may be performed on an object when it is in the
This practice is under the jurisdiction of ASTM Committee E07 on Nonde-
as-cast, intermediate, or final machined condition. A CT
structive Testing and is the direct responsibility of Subcommittee E07.01 on
examinationcanbeusedasadesigntooltoimprovewaxforms
Radiology (X and Gamma) Method.
Current edition approved July 1, 2022. Published July 2022. Originally approved
in 1996. Last previous edition approved in 2014 as E1814 – 14. DOI: 10.1520/
E1814-14R22. AvailablefromAmericanSocietyforNondestructiveTesting(ASNT),P.O.Box
For referenced ASTM standards, visit the ASTM website, www.astm.org, or 28518, 1711 Arlingate Ln., Columbus, OH 43228-0518, http://www.asnt.org.
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM Available from Standardization Documents Order Desk, DODSSP, Bldg. 4,
Standards volume information, refer to the standard’s Document Summary page on Section D, 700 Robbins Ave., Philadelphia, PA 19111-5098, http://
the ASTM website. assist.daps.dla.mil.
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E1814 − 14 (2022)
and moldings, establish process parameters, randomly check 5.1.7 Records—Records requirements shall be specified in
process control, perform final quality control (QC) examina- accordance with Section 10.
tion for the acceptance or rejection of parts, and analyze
6. Apparatus
failures and extend component lifetimes.
6.1 The success of the CT application depends on the
4.2 The most common applications of CT for castings are
overall system configuration and the selection of appropriate
for the following: locating and characterizing discontinuities,
subsystem components. Guidance on the selection of sub-
such as porosity, inclusions, cracks, and shrink; measuring
system components and the overall system configuration is
as-cast part dimensions for comparison with design dimen-
provided in Guide E1672. Guidance on the initial system
sions; and extracting dimensional measurements for reverse
performance evaluation for baseline and periodic system per-
engineering.
formance check of the CT system is provided in Test Method
4.3 The extent to which a CTimage reproduces an object or
E1695. Guidance on calibrating and measuring CT density
a feature within an object is dictated largely by the competing
measurements is provided in Test Method E1935. The suitabil-
influences of spatial resolution, contrast discrimination, the
ityoftheCTsystemshallbedemonstratedbyattainmentofthe
specific geometry and material of the object itself, and artifacts
required image quality and compliance with all other require-
of the imaging system. Operating parameters strike an overall
ments stipulated herein.
balance between image quality, examination time, and cost.
6.2 Computer/Image Processing Software—Image process-
4.4 Artifacts are often the limiting factor in CT image
ing software may be used for image enhancement operations
quality. (See Practice E1570 for an in-depth discussion of
thatwillfacilitatedimensionalmeasurementsanddiscontinuity
artifacts.) Artifacts are reproducible features in an image that
detection or characterization.
are not related to actual features in the object.Artifacts can be
6.2.1 Dimensional measurements, with tolerance, can be
considered correlated noise because they form repeatable fixed
obtained from the CT image. There is a degree of blurring in
patterns under given conditions yet carry no object informa-
the CT image that makes sharp boundaries indistinct. A
tion. For castings, it is imperative to recognize what is and is
common approach for on-screen dimensional measurements is
not an artifact since an artifact can obscure or masquerade as a
to generate a density profile along a straight line between the
discontinuity.Artifacts are most prevalent in castings with long
points in the image representing the distance to be measured.
straight edges or complex geometries, or both.
The end points of the measurement are generally taken to be
5. Basis of Application the density profile values located at the half maximum value
point on each slope. This is called the full-width-at-half-
5.1 The following items shall be agreed upon between the
maximum (FWHM) method. This method or various other
purchaser and the supplier and specified in the contract or job
techniques, that is, the area under the curve or determining
order:
contours for CAD output, can be generalized for wall
5.1.1 Nondestructive Testing Agency Evaluation—The use
thickness, hole diameter, and crack width measurements.
of a nondestructive testing (NDT) agency, as defined in
6.2.2 Each dimensional measurement technique has its own
Practice E543. If a systematic assessment of the capability of
precision, and for its determination, the creation of the CT
the agency is specified, a documented procedure, such as that
image must be understood thoroughly. A point-like object will
described in Practice E543, should be used as the basis for
not appear in an image as a sharp point. Instead, the “true”
evaluation.
image will be convolved with a Gaussian distribution-like
5.1.2 Personnel Qualifications—All CT examination per-
function called the point spread function (PSF). Therefore,
sonnel shall be qualified and certified in accordance with a
when looking at a density profile along a line in a CT image,
written procedure conforming to ANSI/ASNT CP-189, SNT-
an abrupt density change (that is, from material to air) will not
TC-1A, NAS 410, or a similar document. The written proce-
appear as a step but as a curve. See Guide E1441 and Sections
dureshallincludetrainingthataddressesCTissuesspecifically.
5, 8, and 9 for further discussion.
5.1.3 GeneralRequirements—Generalrequirementsshallbe
6.2.3 Some tools require the availability of an object that
specified in accordance with Section 8:(1) written procedure,
can be scanned and then dissected (destructive evaluation) for
8.1; and (2) CT system validation measurements, 8.3.
comparison with actual dimensional measurements.
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