EN ISO 4255:2025

SLOVENSKI STANDARD
01-september-2025
Fina keramika (sodobna keramika, sodobna tehnična keramika) - Mehanske
lastnosti keramičnih kompozitov pri visoki temperaturi - Ugotavljanje enoosnih
nateznih lastnosti cevi (ISO 4255:2025)
Fine ceramics (advanced ceramics, advanced technical ceramics) - Mechanical
properties of ceramic composites at high temperature - Determination of uniaxial tensile
properties of tubes (ISO 4255:2025)
Hochleistungskeramik - Mechanische Eigenschaften von keramischen
Verbundwerkstoffen bei hoher Temperatur - Bestimmung der uniaxialen
Zugeigenschaften von Rohren (ISO 4255:2025)
Céramiques techniques - Propriétés mécaniques des composites céramiques à haute
température - Détermination des propriétés en traction axiale de tubes (ISO 4255:2025)
Ta slovenski standard je istoveten z: EN ISO 4255:2025
ICS:
81.060.30 Sodobna keramika Advanced ceramics
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EN ISO 4255
EUROPEAN STANDARD
NORME EUROPÉENNE
July 2025
EUROPÄISCHE NORM
ICS 81.060.30
English Version
Fine ceramics (advanced ceramics, advanced technical
ceramics) - Mechanical properties of ceramic composites
at high temperature - Determination of uniaxial tensile
properties of tubes (ISO 4255:2025)
Céramiques techniques - Propriétés mécaniques des Hochleistungskeramik - Mechanische Eigenschaften
composites céramiques à haute température - von keramischen Verbundwerkstoffen bei hoher
Détermination des propriétés en traction axiale de Temperatur - Bestimmung der uniaxialen
tubes (ISO 4255:2025) Zugeigenschaften von Rohren (ISO 4255:2025)
This European Standard was approved by CEN on 7 February 2025.

CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this
European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references
concerning such national standards may be obtained on application to the CEN-CENELEC Management Centre or to any CEN
member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by
translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC Management
Centre has the same status as the official versions.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,
Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Türkiye and
United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2025 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 4255:2025 E
worldwide for CEN national Members.

Contents Page
European foreword . 3

European foreword
This document (EN ISO 4255:2025) has been prepared by Technical Committee ISO/TC 206 "Fine
ceramics " in collaboration with Technical Committee CEN/TC 184 “Advanced technical ceramics” the
secretariat of which is held by DIN.
This European Standard shall be given the status of a national standard, either by publication of an
identical text or by endorsement, at the latest by January 2026, and conflicting national standards shall
be withdrawn at the latest by January 2026.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CEN shall not be held responsible for identifying any or all such patent rights.
Any feedback and questions on this document should be directed to the users’ national standards
body/national committee. A complete listing of these bodies can be found on the CEN website.
According to the CEN-CENELEC Internal Regulations, the national standards organizations of the
following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria,
Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland,
Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Republic of
North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Türkiye and the
United Kingdom.
Endorsement notice
The text of ISO 4255:2025 has been approved by CEN as EN ISO 4255:2025 without any modification.

International
Standard
ISO 4255
First edition
Fine ceramics (advanced ceramics,
2025-07
advanced technical ceramics) —
Mechanical properties of ceramic
composites at high temperature
— Determination of axial tensile
properties of tubes
Céramiques techniques — Propriétés mécaniques des composites
céramiques à haute température — Détermination des propriétés
en traction axiale de tubes
Reference number
ISO 4255:2025(en) © ISO 2025
ISO 4255:2025(en)
© ISO 2025
All rights reserved. Unless otherwise specified, or required in the context of its implementation, 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 the address below
or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii
ISO 4255:2025(en)
Contents Page
Foreword .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 2
4 Principle . 4
5 Apparatus . 5
5.1 Testing machine . .5
5.2 Gripping system . .5
5.2.1 Test specimen gripping.5
5.2.2 Location and temperature of grips .5
5.2.3 Load train couplers .6
5.3 Test chamber and heating set-up .6
5.4 Heating apparatus .7
5.5 Strain measurement .7
5.5.1 General .7
5.5.2 Extensometers.7
5.5.3 Digital image correlation .8
5.6 Temperature measurement devices .8
5.7 Data recording system .8
5.8 Dimension-measuring devices .9
6 Tubular test specimen . 9
6.1 Specimen specifications .9
6.1.1 General .9
6.1.2 Dimension .9
6.1.3 Geometry commonly used .9
6.1.4 Tolerances and variability .11
6.2 Specimen preparation .11
6.2.1 General .11
6.2.2 As-fabricated .11
6.2.3 Application-matched machining .11
6.2.4 Customary practices . 12
6.2.5 Standard procedure . . . 12
6.3 End collars and alignment issue . 12
6.4 Test count and test specimens sampling .14
7 Test procedure . 14
7.1 Temperature considerations .14
7.1.1 General .14
7.1.2 Controlled temperature zone .14
7.1.3 Temperature measurement .14
7.2 Test set-up: other considerations .14
7.3 Testing technique . 15
7.3.1 Measurement of test specimen dimensions . 15
7.3.2 Instrumentation of the test specimen . 15
7.3.3 Specimen mounting . 15
7.3.4 Setting-up of strain measurement means . 15
7.3.5 Setting-up of inert atmosphere .16
7.3.6 Heating of test specimen and temperature control .16
7.3.7 Measurements .16
7.3.8 Post-test analyses .17
7.4 Test validity .17
8 Calculation of results . 17
8.1 Test specimen origin .17

iii
ISO 4255:2025(en)
8.2 Engineering axial tensile stress and strain .18
8.3 Tensile strength .18
8.4 Strain at maximum tensile force .19
8.5 Tensile modulus .19
8.5.1 Calculation of tensile modulus .19
8.5.2 Calculation of tensile elastic modulus with linear region . 20
8.5.3 Stress for materials with non-linear stress-strain curve . 20
8.6 Poisson’s ratio (optional) . 20
8.7 Statistics . 20
9 Test report .21
9.1 General .21
9.2 Testing information . .21
9.3 Test specimen and material .21
9.3.1 Tubular test specimen drawing or reference .21
9.3.2 Description of the test material .21
9.4 Equipment and test parameters .21
9.4.1 Testing machine type and configuration .21
9.4.2 Temperature and force measurement description .21
9.4.3 Test mode and test rate . 22
9.4.4 Strain measurement description . 22
9.5 Test results . 22
10 Uncertainties .22
Annex A (informative) Illustration of tensile modulus .23
Bibliography .26

iv
ISO 4255:2025(en)
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,
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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, the different approval criteria needed for the different types
of ISO document 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).
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent
rights in respect thereof. As of the date of publication of this document, ISO had not received notice of (a)
patent(s) which may be required to implement this document. However, implementers are cautioned that
this may not represent the latest information, which may be obtained from the patent database available at
www.iso.org/patents. ISO shall not be held responsible for identifying any or all such patent rights.
Any trade name used in this document is information given for the convenience of users and does not
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related to conformity assessment, as well as information about ISO's adherence to the World Trade
Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 206, Fine ceramics, in collaboration with
the European Committee for Standardization (CEN) Technical Committee CEN/TC 184, Advanced technical
ceramics, in accordance with the Agreement on technical cooperation between ISO and CEN (Vienna
Agreement).
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.

v
International Standard ISO 4255:2025(en)
Fine ceramics (advanced ceramics, advanced technical
ceramics) — Mechanical properties of ceramic composites at
high temperature — Determination of axial tensile properties
of tubes
1 Scope
This document specifies the conditions for determination of the axial tensile properties of ceramic matrix
composite (CMC) tubes with continuous fibre-reinforcement at elevated temperature in air, vacuum and
inert gas atmospheres. The applicability of this document is specific to tubular geometries because fibre
architecture and specimen geometry factors in composite tubes are distinctly different from those in flat
specimens.
This document provides information on the axial tensile properties and stress-strain response in
temperature, such as axial tensile strength, axial tensile strain at failure and elastic constants. The
information can be used for material development, control of manufacturing (quality insurance), material
comparison, characterization, reliability and design data generation for tubular components.
This document addresses, but is not restricted to, various suggested test piece fabrication methods.
This document is primarily applicable to ceramic matrix composite tubes with a continuous fibrous-
reinforcement: unidirectional (1D, filament winding and tape lay-up), bi-directional (2D, braid and weave)
and multi-directional (xD, with x > 2), tested along the tube axis.
2 Normative references
The 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, only the edition cited applies. For undated references,
the latest edition of the referenced document (including any amendments) applies.
ISO 3611, Geometrical product specifications (GPS) — Dimensional measuring equipment — Design and
metrological characteristics of micrometers for external measurements
ISO 7500-1, Metallic materials — Calibration and verification of static uniaxial testing machines — Part 1:
Tension/compression testing machines — Calibration and verification of the force-measuring system
ISO 9513, Metallic materials — Calibration of extensometer systems used in uniaxial testing
ISO 17161, Fine ceramics (advanced ceramics, advanced technical ceramics) — Ceramic composites —
Determination of the degree of misalignment in uniaxial mechanical tests
ISO 19634, Fine ceramics (advanced ceramics, advanced technical ceramics) — Ceramic composites — Notations
and symbols
ISO 20507, Fine ceramics (advanced ceramics, advanced technical ceramics) — Vocabulary
IEC 60584-1, Thermocouples — Part 1: EMF specifications and tolerances
ASTM E2208-02, Standard Guide for Evaluating Non-Contacting Optical Strain Measurement Systems

ISO 4255:2025(en)
3 Terms and definitions
For the purpose of this document, the terms and definitions given in ISO 19634 and ISO 20507 and the
following apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1
test temperature
T
temperature of the test piece at the centre of the gauge length
3.2
calibrated length
l
part of the test specimen that has uniform and minimum cross-section area
3.3
gauge length
L
initial distance between reference points on the test specimen in the calibrated length (3.2)
3.4
controlled temperature zone
part of the calibrated length (3.2) including the gauge length (3.3) where the temperature is controlled within
a range of 20 °C of the test temperature (3.1)
3.5
internal diameter
d
i
inner distance through the centre of the tube from one side to the other in the gauge length (3.3)
[SOURCE: ISO 21971:2019, 3.4]
3.6
external diameter
d
o
outer distance through the centre of the tube from one side to the other in the gauge length (3.3)
[SOURCE: ISO 21971:2019, 3.3]
3.7
wall thickness
h
half the difference between the external (3.6) and the internal diameters (3.5) in the gauge length (3.3)
[SOURCE: ISO 21971:2019, 3.5, modified — new formulation.]
3.8
initial cross-section area
S
o
cross-section area of the test specimen within the calibrated length (3.2) at room temperature before testing
3.9
effective cross-section area
S
o,eff
area corrected by a factor to account of the presence of a surface layer

ISO 4255:2025(en)
3.10
longitudinal deformation
A
dimensional variation in the gauge length (3.3) under a tensile force in the load direction
Note 1 to entry: The longitudinal deformation corresponding to the maximum tensile force is denoted as A
t,m.
3.11
axial tensile strain
ε
zz
relative change of the initial gauge length (3.3) in the axial (or longitudinal) direction defined as the ratio A/L
o
Note 1 to entry: The tensile strain corresponding to the maximum tensile force is denoted as ε
zz,t,m.
3.12
circumferential strain
ε
θθ
relative change of the initial gauge length (3.3) in the circumferential direction
3.13
uniaxial tensile force
F
force carried by the test specimen in the axial (or longitudinal) direction at any time during the tensile test
3.14
axial tensile stress
σ
zz
uniaxial tensile force (3.13) supported by the test specimen in the axial (or longitudinal) direction at any
time in the test divided by the initial cross-section area (3.8)
Note 1 to entry: The effective axial tensile stress corresponding to the uniaxial tensile force supported by the test
specimen in the axial (or longitudinal) direction at any time in the test divided by the effective cross-section area (3.9)
is denoted as σ .
zz,eff
3.15
maximum uniaxial tensile force
F
m
highest recorded uniaxial tensile force in a tensile test on the test specimen when tested to failure
3.16
axial tensile strength
σ
zz,m
ratio of the maximum uniaxial tensile force (3.15) to the initial cross-section area (3.8)
Note 1 to entry: The effective axial tensile strength corresponding to the ratio of the maximum uniaxial tensile force
(3.15) to the effective cross-section area (3.9) is denoted as σ .
zz,m,eff
3.17
tensile modulus
E
zz
slope of the initial linear part of the stress-strain curve at or near the origin
Note 1 to entry: The linear part may not exist or may not start at the origin. The different situations are then described
in the Annex A.
Note 2 to entry: The effective tensile modulus corresponding to the slope of the linear part of the stress-strain curve at
or near the origin when the effective axial tensile stress is used is denoted as E .
zz, eff
ISO 4255:2025(en)
3.18
Poisson’s ratio
ν
θz
negative ratio of circumferential strain (3.12) to axial tensile strain (3.11)
[SOURCE: ISO 20323:2018, 3.19, modified — the word ‘tensile’ has been added.]
3.19
coordinate system
system used to determine location in space
Note 1 to entry: Cylindrical coordinates are adopted in this document.
Note 2 to entry: The notations shown in Figure 1 apply for space representation.
Key
z axial
r radial
θ azimuthal (or orthoradial)
Figure 1 — Cylindrical coordinate system used for the CMC tubes
[SOURCE: ISO 20323:2018, 3.20, modified — azimuthal coordinate considered.]
4 Principle
A prepared tubular test specimen of specified dimensions is heated to the test temperature, then loaded in
monotonic uniaxial tension up to fracture. The test is performed at constant crosshead displacement rate,
or constant deformation rate (or constant loading rate). Both the applied force and resulting longitudinal
strain are measured and recorded simultaneously. The uniaxial tensile strength and strain are determined
from the maximum applied force while the various other axial tensile properties are determined from the
stress-strain response data.
When constant loading rate is used in the nonlinear region of the tensile curve, only the axial tensile strength
(3.16) can be obtained from the test. In this region, constant crosshead displacement rate or constant
deformation rate is recommended to obtain the complete curve
NOTE 1 The test duration is limited to reduce creep effects.
NOTE 2 Uniaxial tensile loading means that the force is applied parallel to the tube axis while monotonic refers to a
continuous non-stop test rate with no reversals from test initiation to final fracture.

ISO 4255:2025(en)
5 Apparatus
5.1 Testing machine
The test machine shall be equipped with a system for measuring the force applied to the tubular test
specimen conforming to grade 1 or better in accordance with ISO 7500-01.
This should prevail during actual test conditions of, e.g. gas pressure and temperature.
5.2 Gripping system
5.2.1 Test specimen gripping
Various types of gripping device may be used to transmit the measured force applied by the testing machine
to the tubular test specimen. It shall prevent the tubular test specimen from slipping.
The brittle nature of the ceramic matrix composites (CMCs) requires a uniform and continuous contact
between the grip components and the gripped section of the tubular test specimen in order to minimize
crack initiation and fracture in this area.
Gripping devices can be classified generally as those employing active grip interfaces and those employing
passive grip interfaces that include gripping system with adhesive bonding or through a pin-loaded fixture.
Examples, descriptions and designs for both the gripping types are discussed in ISO 20323 for testing
CMC at ambient temperature. For testing at elevated temperature, these must consider the heating and
environmental constraints with regard to the system employed.
5.2.2 Location and temperature of grips
Depending on the test machine configuration, the gripping system can be located inside or outside the
heated zone.
— Uncooled grips located inside the heated zone are referred to as “hot grips” and generally produce almost
no thermal gradient in the test specimen.
— Cooled grips located outside the heated zone are referred to as “cold grips” and generally induce a
steep thermal gradient in the test specimen. Grips located outside the heated zone surrounding the test
specimen may or may not employ cooling.
Figure 2 shows a schematic example to illustrate the principle a satisfactory gripping design with cooling
system for testing tubular CMC tubes at high temperature.
NOTE 1 The choice of gripping system will depend on material, on test specimen and on alignment requirements.
The expense of the cooling system for cold grips is balanced against maintaining alignment that remains consistent
from test to test and decreased degradation of the grip due to exposure to the high temperature-oxidizing environment.
NOTE 2 The hot grip technique is limited in temperature because of the nature and strength of the grips materials

ISO 4255:2025(en)
Key
1 tubular test specimen
2 upper cold grip device
3 thermal insulation panel
4 cooling system
5 window for extensometer
6 lower cold grip device
7 furnace
Figure 2 — Example of “cold grip” configuration for the determination of the axial properties of CMC
tubes at high temperature
5.2.3 Load train couplers
The load train couplers in conjunction with the type of gripping device play major roles in the alignment of
the load train and extraneous bending imposed in the tubular test specimen; they can be generally classified
as fixed and non-fixed, as discussed in ISO 20323.
If each system type can be used, the load train configuration shall ensure that the load indicated by the
load cell and the load experienced by the tubular test specimen are the same. The load train performance,
including both the alignment and force transmitting systems, shall not change because of heating.
The load train shall align the tubular test specimen axis with the direction of load application without
introduction bending or torsion in specimen.
The alignment shall be checked at room temperature and documented. The procedure described in ISO 17161
adapted to the tubular geometry of specimen should be applied.
−4
The maximum relative bending shall not exceed 5 % at an average strain of 5×10 .
5.3 Test chamber and heating set-up
The test chamber shall be as gas-tight as possible and shall allow proper control of the environment near the
tubular test specimen during the test.

ISO 4255:2025(en)
The installation shall be such that the variation of the load due to the variation of pressure is less than 1 % of
the scale of the load cell being used.
Where a gas atmosphere is used, it shall be chosen in accordance with the material to be tested and the test
temperature. The level of pressure shall be chosen depending on the material to be tested, on temperature,
on the type of gas, and on the type of extensometer.
Where a vacuum chamber is used, the level of vacuum shall not induce chemical and/or physical instabilities
of the test specimen material, and of extensometer rods, when applicable. Primary vacuum (typically 1 Pa
pressure or less) is recommended.
5.4 Heating apparatus
The set-up for heating shall be constructed in such a way that the temperature gradient within the gauge
length satisfy a maximum deviation of 20 °C from the test temperature.
Heating can be provided by indirect electrical resistance (heating elements), indirect induction through a
susceptor, or radian lamp, in which case the tubular test specimen is placed in ambient air at atmospheric
pressure, unless other environments are specifically applied and reported. Direct resistance heating does
not provide uniform heating of CMC tubular test specimen due to the constituent materials and is therefore
not acceptable
NOTE An example of calibration method of test temperature is described in ISO 14574.
5.5 Strain measurement
5.5.1 General
Strain should be locally measured in order to avoid having to take into account the compliance of the
machine. This may be by means of suitable extensometers, or digital image correlation (DIC). If Poisson’s
ratio is to be determined, the tubular test specimen shall be instrumented to measure strain in both axial
(or longitudinal) and circumferential directions.
NOTE Bonded resistance strain gauges are only used for the verification of the alignment on the test specimen at
room temperature. They cannot be used to determine the axial (or longitudinal) deformation during testing at high
temperature.
5.5.2 Extensometers
5.5.2.1 General
Extensometers used for tensile testing of CMC tubular test specimens shall be capable of continuously
recording the longitudinal strain at test temperature. The used of an extensometer with the greatest gauge
length are recommended with a minimum of 25 mm required.
Extensometers shall meet the requirements of class 1 or less (class 0,5) in accordance with ISO 9513. Types
of commonly used extensometers are described in 5.5.2.2 and 5.5.2.3.
5.5.2.2 Mechanical extensometer
For a mechanical (or contact) extensometer, the gauge length shall be the longitudinal distance between
the two locations, centrally located in the mid region of the axial direction of the gauge section where the
extensometer rods contact the test specimen. The selected attachment should cause no damage to the
specimen surface.
The rods may be exposed to temperatures higher than the test specimen temperature. Temperature
induced structural changes in the rod material shall not affect the accuracy of deformation measurement.
The material used for the rods shall be chemically compatible with the test specimen material at testing
temperature.
ISO 4255:2025(en)
Any extensometer contact forces shall not introduce bending greater than that allowed in 5.2.3.
Care should be taken to correct for changes in calibration of the extensometer that may occur as a result of
operating under conditions different from calibration. Verification may be done by measuring the tensile
modulus on a well-known material specimen.
Rod pressure onto the test specimen should be the minimum necessary to prevent slipping of the
extensometer rods.
5.5.2.3 Electro-optical extensometer
Electro-optical measurements in transmission require reference marks on the test specimen. For this
purpose, rods or flags shall be attached to the surface perpendicularly to its axis. The gauge length shall
be the longitudinal distance between the two reference marks. The material used for marks (and adhesive
if used) shall be compatible with the tubular test specimen material and durable at the test temperature
without altering the stress field in the specimen.
The use of integral flags as parts of the test specimen geometry is not recommended because of stress
concentration induced by such features.
Electro-optical extensometer is not recommended in the case where it is impossible to distinguish the
colours of the reference marks and the test specimen.
5.5.3 Digital image correlation
Digital image correlation (DIC) method can be used for non-contact strain-field measurement at high
temperature.
The general procedure to be followed for estimating the strain measurement shall be in accordance with
ASTM E2208-02 adapted for testing at high temperature.
This technique usually employs an optical filter to reduce the influence of radiation on the intensity of
captured images and to provide a correct signal-to-noise ratio of random patterns at elevated temperature.
In order to improve the measurement accuracy, the size of furnace window may be minimized.
In case of off-axis strain measurement, the use of a telecentric lens is required to overcome the curvature of
the tubular test specimen.
Full-field deformation output procedure and calibration data shall be annexed to the test report.
NOTE Guidelines for using the DIC method on CMC tubes are described in ISO 20323.
5.6 Temperature measurement devices
Temperature measurement shall be sufficiently sensitive and reliable to ensure that the temperature of the
tubular test specimen conforms with the limits specified in 7.1.2.
Either thermocouples conforming to IEC 60584-1 shall be used or, when thermocouples not conforming to
IEC 60584-1 or pyrometers are used, calibration data shall be annexed to the test report.
5.7 Data recording system
A calibrated recorder shall be used to record the applied tensile force and the gauge section elongation (or
strain) versus time. The use of a digital data recording system is recommended for ease of later data analysis.
Recording devices shall be accurate to within ±0,1 % for the entire testing system including readout unit and
shall have a minimum data acquisition rate of 10 Hz, with a response of 50 Hz deemed more than sufficient.
Crosshead displacement of the test machine may also be recorded but shall not define displacement or strain
in the gauge section, especially when self-aligning couplers are used in the load train.

ISO 4255:2025(en)
5.8 Dimension-measuring devices
Micrometres used for measuring the dimensions of the tubular test specimen shall be in accordance with
ISO 3611. The internal and external diameters of the tubular test specimen should be measured with an
accuracy of 0,02 mm or 1 % of the measured dimension, whichever is highe
...