SIST-TS CEN ISO/TS 21432:2005

SLOVENSKI STANDARD
SIST-TS CEN ISO/TS 21432:2005
01-november-2005
Neporušitveno preskušanje – Standardizirane preskusne metode za ugotavljanje
zaostalih napetosti z uklonom nevtronskih žarkov (ISO 21432:2005)
Non-destructive testing - Standards test method for determining residual stresses by
neutron diffraction (ISO 21432:2005)
Zerstörungsfreie Prüfung - Standardprüfverfahren zur Bestimmung von
Eigenspannungen durch Neutronenbeugung (ISO/TS 21432:2005)
Essais non destructifs - Méthode normalisée de détermination des contraintes
résiduelles par diffraction de neutrons (ISO 21432:2005)
Ta slovenski standard je istoveten z: CEN ISO/TS 21432:2005
ICS:
19.100 Neporušitveno preskušanje Non-destructive testing
SIST-TS CEN ISO/TS 21432:2005 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST-TS CEN ISO/TS 21432:2005

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SIST-TS CEN ISO/TS 21432:2005
TECHNICAL SPECIFICATION
CEN ISO/TS 21432
SPÉCIFICATION TECHNIQUE
TECHNISCHE SPEZIFIKATION
July 2005
ICS 19.100

English Version
Non-destructive testing - Standards test method for determining
residual stresses by neutron diffraction (ISO 21432:2005)
Essais non destructifs - Méthode normalisée de Zerstörungsfreie Prüfung - Standardprüfverfahren zur
détermination des contraintes résiduelles par diffraction de Bestimmung von Eigenspannungen durch
neutrons (ISO 21432:2005) Neutronenbeugung (ISO 21432:2005)
This Technical Specification (CEN/TS) was approved by CEN on 26 March 2005 for provisional application.
The period of validity of this CEN/TS is limited initially to three years. After two years the members of CEN will be requested to submit their
comments, particularly on the question whether the CEN/TS can be converted into a European Standard.
CEN members are required to announce the existence of this CEN/TS in the same way as for an EN and to make the CEN/TS available
promptly at national level in an appropriate form. It is permissible to keep conflicting national standards in force (in parallel to the CEN/TS)
until the final decision about the possible conversion of the CEN/TS into an EN is reached.
CEN members are the national standards bodies of Austria, Belgium, Cyprus, Czech Republic, Denmark, Estonia, Finland, France,
Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Slovakia,
Slovenia, Spain, Sweden, Switzerland and United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
Management Centre: rue de Stassart, 36  B-1050 Brussels
© 2005 CEN All rights of exploitation in any form and by any means reserved Ref. No. CEN ISO/TS 21432:2005: E
worldwide for CEN national Members.

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SIST-TS CEN ISO/TS 21432:2005

CEN ISO/TS 21432:2005 (E)





Foreword


This document (CEN ISO/TS 21432:2005) has been prepared by Technical Committee CEN/TC
138 "Non-destructive testing", the secretariat of which is held by AFNOR, in collaboration with
Technical Committee ISO/TC 135 "Non-destructive testing”.

According to the CEN/CENELEC Internal Regulations, the national standards organizations of
the following countries are bound to announce this CEN Technical Specification: Austria,
Belgium, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece,
Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,
Poland, Portugal, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom.


2

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SIST-TS CEN ISO/TS 21432:2005


TECHNICAL ISO/TS
SPECIFICATION 21432
First edition
2005-07-15

Non-destructive testing — Standard test
method for determining residual stresses
by neutron diffraction
Essais non destructifs — Méthode normalisée de détermination des
contraintes résiduelles par diffraction de neutrons




Reference number
ISO/TS 21432:2005(E)
©
ISO 2005

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SIST-TS CEN ISO/TS 21432:2005
ISO/TS 21432:2005(E)
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ii © ISO 2005 – All rights reserved

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SIST-TS CEN ISO/TS 21432:2005
ISO/TS 21432:2005(E)
Contents Page
Foreword. v
Introduction . vi
1 Scope . 1
2 Normative references . 1
3 Terms and definitions. 2
4 Symbols and abbreviated terms . 5
4.1 Symbols . 5
4.2 Subscripts . 6
4.3 Abbreviated terms . 7
5 Summary of method . 7
5.1 Preamble. 7
5.2 Outline of principle — Bragg’s law . 7
5.3 Neutron sources . 7
5.4 Strain measurement . 7
5.5 Neutron diffractometers. 8
5.6 Stress determination . 9
6 Preparations for measurements. 12
6.1 Preamble. 12
6.2 Alignment and calibration of the instrument . 12
6.3 Choice of diffraction conditions. 12
6.3.1 Monochromatic instruments . 12
6.3.2 TOF instruments . 15
6.4 Positioning procedures. 15
6.5 Gauge volumes . 15
6.6 Determination of a strain free or reference lattice spacing. 16
7 Material characterization. 18
7.1 Preamble. 18
7.2 Composition . 18
7.3 Thermal/mechanical history . 18
7.4 Phases and crystal structures. 18
7.5 Homogeneity . 18
7.6 Microstructure. 18
7.7 Texture . 18
8 Recording requirements and measurement procedure. 19
8.1 Preamble. 19
8.2 Recording requirements . 19
8.2.1 General information — instrument . 19
8.2.2 General information — specimen . 20
8.2.3 Specific information required for each strain measurement . 20
8.3 Specimen co-ordinates . 21
8.4 Positioning of the specimen. 21
8.5 Measurement directions . 21
8.6 Number and location of measuring positions . 21
8.7 Gauge volume . 21
8.8 Gauge volume centroid considerations . 21
8.9 Temperature . 22
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SIST-TS CEN ISO/TS 21432:2005
ISO/TS 21432:2005(E)
9 Calculation of stress. 22
9.1 Preamble . 22
9.2 Normal stress determinations . 22
9.3 Stress state determinations. 23
2
9.3.1 The sin ψ method . 23
9.4 Choice of elasticity constants . 23
9.5 Data analysis . 24
9.5.1 Peak fitting function. 24
9.5.2 Background function . 24
9.5.3 Peak to background ratio . 24
9.5.4 Distorted peak profiles . 24
10 Reliability of results . 25
11 Reporting . 25
11.1 Preamble . 25
11.2 Strain or stress values. 25
11.2.1 Stress free or reference lattice spacing. 26
11.2.2 Conversion of strain to stress . 26
11.2.3 Elasticity constants . 26
11.2.4 Positioning. 26
11.3 Neutron source and instrument. 26
11.4 General measurement procedures. 26
11.5 Specimens/materials properties. 26
11.6 Original data . 27
Annex A (informative) Measurement procedures. 28
Annex B (informative) Determination of uncertainties in a measurand. 36
Bibliography . 39

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SIST-TS CEN ISO/TS 21432:2005
ISO/TS 21432:2005(E)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies
(ISO member bodies). The work of preparing International Standards is normally 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 the work. ISO collaborates closely with the
International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
In other circumstances, particularly when there is an urgent market requirement for such documents, a
technical committee may decide to publish other types of normative document:
— an ISO Publicly Available Specification (ISO/PAS) represents an agreement between technical experts in
an ISO working group and is accepted for publication if it is approved by more than 50 % of the members
of the parent committee casting a vote;
— an ISO Technical Specification (ISO/TS) represents an agreement between the members of a technical
committee and is accepted for publication if it is approved by 2/3 of the members of the committee casting
a vote.
An ISO/PAS or ISO/TS is reviewed after three years with a view to deciding whether it should be confirmed for
a further three years, revised to become an International Standard, or withdrawn. In the case of a confirmed
ISO/PAS or ISO/TS, it is reviewed again after six years at which time it has to be either transposed into an
International Standard or withdrawn.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. ISO shall not be held responsible for identifying any or all such patent rights.
ISO/TS 21432 was prepared by the European Committee for Standardization (CEN) Technical Committee
CEN/TC 138, Non-destructive testing, in collaboration with Technical Committee ISO/TC 135, Non-destructive
testing, Subcommittee SC 5, Radiation methods, in accordance with the Agreement on technical cooperation
between ISO and CEN (Vienna Agreement).

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SIST-TS CEN ISO/TS 21432:2005
ISO/TS 21432:2005(E)
Introduction
Neutron diffraction is a non-destructive method that can be employed for determining residual stresses in
crystalline materials. It can also be used for establishing applied stresses. The procedure can be employed for
determining stresses within the interior of materials and adjacent to surfaces. It requires specimens or
engineering components to be transported to a neutron source. Measurements of elastic strain are obtained
which are then converted to stress. The purpose of this document is to provide the technical specification for
reliably determining stresses that are relevant to engineering applications.
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SIST-TS CEN ISO/TS 21432:2005
TECHNICAL SPECIFICATION ISO/TS 21432:2005(E)

Non-destructive testing — Standard test method for
determining residual stresses by neutron diffraction
WARNING — This Technical Specification does not purport to address the safety concerns, if any,
associated with its use. It is the responsibility of the user of this Technical Specification to establish
appropriate safety and health practices and determine the applicability of regulatory limitations prior
to use.
1 Scope
This Technical Specification gives the standard test method for determining residual stresses in polycrystalline
materials by neutron diffraction. It is applicable to homogeneous and inhomogeneous materials and to test
pieces containing distinct phases.
The principles of the neutron diffraction technique are outlined. Advice is provided on the diffracting lattice
planes on which measurements should be made for different categories of materials. Guidance is provided
about the directions in which the measurements should be obtained and of the volume of material, which
should be examined, in relation to material grain size and the stress state envisaged, when making
measurements.
Procedures are described for accurately positioning and aligning test pieces in a neutron beam and for
precisely defining the volume of material that is sampled when individual measurements are being made.
The precautions needed for calibrating neutron diffraction instruments are described. Techniques for obtaining
a stress free reference are presented.
The methods of making individual elastic strain measurements by neutron diffraction are described in detail.
Procedures for analysing the results and for determining their statistical relevance are presented. Advice is
provided on how to determine reliable estimates of residual (or applied) stress from the strain data and of how
to estimate the uncertainty in the results.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated
references, only the edition cited applies. For undated references, the latest edition of the referenced
document (including any amendments) applies.
EN 13925-3, Non-destructive testing — X-ray diffraction from polycrystalline and amorphous materials —
1)
Part 3: Instruments

1) To be published.
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SIST-TS CEN ISO/TS 21432:2005
ISO/TS 21432:2005(E)
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
absorption
neutron capture by an atomic nucleus
NOTE Tables of nuclear capture cross sections can be found under e.g. http://www.webelements.com and links.
3.2
alignment
adjustment of position and orientation of the specimen and all components of the instrument such that reliable
strain measurements by neutron diffraction can be performed at the desired location in the specimen
3.3
anisotropy
dependence of material properties on orientation
3.4
attenuation
reduction of neutron intensity
NOTE Attenuation can be calculated by using the so called “total neutron cross section”, which comprises absorption
and different nuclear scattering processes. The attenuation length is the distance within the material for which the primary
neutron intensity is reduced by 1/e.
3.5
background
intensity considered not belonging to the diffraction signal
NOTE Background dependence on scattering angle or time-of-flight is not uncommon and can have an influence on
the peak position resulting from data analysis.
3.6
beam defining optics
arrangement of devices used to determine the properties of a neutron beam such as the wavelength and
intensity distributions, divergence and shape
NOTE These include devices such as apertures, slits, collimators, monochromators and mirrors.
3.7
Bragg edge
sudden change in neutron intensity as a function of wavelength or diffraction angle corresponding to
λ=2d where h′k′l′ indicates a diffracting lattice plane
h′ k′ l′
3.8
Bragg peak
intensity distribution of the diffracted beam for a specific hkl lattice plane
3.9
peak height
maximum intensity of the Bragg peak above the background
3.10
peak function
analytical expression to describe the shape of the diffraction line
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SIST-TS CEN ISO/TS 21432:2005
ISO/TS 21432:2005(E)
3.11
peak position
single value describing the position of a Bragg peak
NOTE The peak position is the determining quantity to calculate strain.
3.12
diffraction
scattering based on interference phenomena
3.13
diffraction elasticity constants
elasticity constants associated with individual (hkl) lattice planes for a polycrystalline material
NOTE They are often called elastic constants and can be denoted as E (diffraction elastic modulus) and ν
hkl hkl
(diffraction Poisson’s ratio).
3.14
diffraction pattern
distribution of scattered neutrons over the available range of wavelengths or times of flight and/or scattering
angles
3.15
full width at half maximum
FWHM
width of the diffraction line at half the maximum height above the background
3.16
full pattern analysis
determination of crystallographic structure and/or microstructure from a measured diffraction pattern of a
polycrystalline material
NOTE In general the full pattern analysis is termed after the method used (e.g. Rietveld refinement) See also single
peak analysis.
3.17
gauge volume
volume from which diffraction data are obtained
NOTE This volume is determined by the intersection of the incident and diffracted neutron beams.
3.18
lattice parameters
linear and angular dimensions of the crystallographic unit cell
NOTE Most engineering materials have either cubic or hexagonal crystal structures. Hence the lattice parameters
usually only refer to the lengths of the unit cell edges.
3.19
lattice spacing
d-spacing
spacing between adjacent crystallographic lattice planes
3.20
macrostress
type I stress
mean stress in a volume containing a large number of grains
NOTE Also called stress of type I.
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SIST-TS CEN ISO/TS 21432:2005
ISO/TS 21432:2005(E)
3.21
microstress
mean stress deviation in a restricted volume from the macrostress level
NOTE There are two classes of microstress:
⎯ the mean deviation from the macrostress determined over a grain or phase dimension (also called type II);
⎯ the mean deviation from the type II stress determined over a volume of several atomic dimensions (also called
type III).
3.22
monochromatic instrument
neutron instrument employing a narrow band of neutron energies (wavelengths)
3.23
monochromatic neutron beam
neutron beam with narrow band of neutron energies (wavelengths)
3.24
orientation distribution function
quantitative description of the crystallographic texture
NOTE The orientation distribution function is necessary to calculate the elasticity constants of textured materials.
3.25
polychromatic neutron beam
neutron beam containing a continuous range of neutron energies (wavelengths)
3.26
reference point
centroid of the instrumental gauge volume
NOTE See 6.5.
3.27
reproducibility
closeness of the agreement between the results of measurements of the same measurand carried out under
changed conditions of measurements
[VIM: 1993]
NOTE 1 A valid statement of reproducibility requires specification of the conditions changed. These can include
principle of measurements, method of measurements, observer, measuring instrument, reference standard, location,
conditions of use and time.
NOTE 2 Reproducibility can be expressed quantitatively in terms of the dispersion characteristics of the results.
NOTE 3 Results are here usually understood to be corrected results.
3.28
scattering
coherent scattering
scattering of neutrons from ordered scattering centres producing constructive and destructive interference of
the particle waves
3.29
incoherent scattering
scattering of neutrons in an uncorrelated way
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SIST-TS CEN ISO/TS 21432:2005
ISO/TS 21432:2005(E)
3.30
single peak analysis
statistical procedure to determine the characteristics of a peak and the background from the measured
diffraction data
3.31
texture
preferred orientation of crystallites (crystallographic texture) or reinforcements (morphological texture) within a
specimen
3.32
through surface scan
procedure to determine the position of a specimen surface or interface
NOTE Sometimes also termed surface scan or intensity scan while its result is often called an entering curve.
3.33
time-of-flight
time needed by a neutron of a given speed (i.e. energy or wavelength) to cover the distance from a defined
starting point to the detector
3.34
uncertainty of measurement
parameter, associated with the result of a measurement, that characterises the dispersion of the values that
could reasonably be attributed to the measurand
[VIM: 1993]
NOTE 1 The parameter may be, for example, a standard deviation (or a given multiple of it), or the half-width of an
interval having a stated level of confidence.
NO
...