prEN ISO 23146

SLOVENSKI STANDARD
01-marec-2026
Fina keramika (sodobna keramika, sodobna tehnična keramika) - Preskusne
metode za ugotavljanje odpornosti monolitske keramike proti lomljenju - Metoda
upogibnega preskusa z V-zarezo (metoda SEVNB) (ISO/DIS 23146:2025)
Fine ceramics (advanced ceramics, advanced technical ceramics) - Test methods for
fracture toughness of monolithic ceramics - Single-edge V-notch beam (SEVNB) method
(ISO/DIS 23146:2025)
Hochleistungskeramik - Prüfverfahren zur Bestimmung der Bruchzähigkeit
monolithischer Keramik - Verfahren für Biegeproben mit V-Kerb (SEVNB-Verfahren)
(ISO/DIS 23146:2025)
Céramiques techniques - Méthodes d'essai pour la détermination de la ténacité à la
rupture des céramiques monolithiques - Méthode sur éprouvette à entaille en V sur une
seule face (Méthode SEVNB) (ISO/DIS 23146:2025)
Ta slovenski standard je istoveten z: prEN ISO 23146
ICS:
81.060.30 Sodobna keramika Advanced ceramics
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

DRAFT
International
Standard
ISO/DIS 23146
ISO/TC 206
Fine ceramics (advanced ceramics,
Secretariat: JISC
advanced technical ceramics) —
Voting begins on:
Test methods for fracture toughness
2025-12-15
of monolithic ceramics — Single-
Voting terminates on:
edge V-notch beam (SEVNB) method
2026-03-09
Céramiques techniques — Méthodes d'essai pour la
détermination de la ténacité à la rupture des céramiques
monolithiques — Méthode sur éprouvette à entaille en V sur une
seule face (Méthode SEVNB)
ICS: 81.060.30
THIS DOCUMENT IS A DRAFT CIRCULATED
FOR COMMENTS AND APPROVAL. IT
IS THEREFORE SUBJECT TO CHANGE
AND MAY NOT BE REFERRED TO AS AN
INTERNATIONAL STANDARD UNTIL
PUBLISHED AS SUCH.
This document is circulated as received from the committee secretariat.
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NOTIFICATION OF ANY RELEVANT PATENT
RIGHTS OF WHICH THEY ARE AWARE AND TO
PROVIDE SUPPORTING DOCUMENTATION.
Reference number
ISO/DIS 23146:2025(en)
DRAFT
ISO/DIS 23146:2025(en)
International
Standard
ISO/DIS 23146
ISO/TC 206
Fine ceramics (advanced ceramics,
Secretariat: JISC
advanced technical ceramics) —
Voting begins on:
Test methods for fracture toughness
of monolithic ceramics — Single-
Voting terminates on:
edge V-notch beam (SEVNB) method
Céramiques techniques — Méthodes d'essai pour la
détermination de la ténacité à la rupture des céramiques
monolithiques — Méthode sur éprouvette à entaille en V sur une
seule face (Méthode SEVNB)
ICS: 81.060.30
THIS DOCUMENT IS A DRAFT CIRCULATED
FOR COMMENTS AND APPROVAL. IT
IS THEREFORE SUBJECT TO CHANGE
AND MAY NOT BE REFERRED TO AS AN
INTERNATIONAL STANDARD UNTIL
PUBLISHED AS SUCH.
This document is circulated as received from the committee secretariat.
IN ADDITION TO THEIR EVALUATION AS
BEING ACCEPTABLE FOR INDUSTRIAL,
© ISO 2025
TECHNOLOGICAL, COMMERCIAL AND
USER PURPOSES, DRAFT INTERNATIONAL
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
STANDARDS MAY ON OCCASION HAVE TO
ISO/CEN PARALLEL PROCESSING
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
BE CONSIDERED IN THE LIGHT OF THEIR
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POTENTIAL TO BECOME STANDARDS TO
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or ISO’s member body in the country of the requester.
NATIONAL REGULATIONS.
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TO SUBMIT, WITH THEIR COMMENTS,
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NOTIFICATION OF ANY RELEVANT PATENT
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Website: www.iso.org
Published in Switzerland Reference number
ISO/DIS 23146:2025(en)
ii
ISO/DIS 23146:2025(en)
Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 2
5 Apparatus . 3
6 Test piece preparation . 4
6.1 Number of test pieces .4
6.2 Test piece dimensions .4
6.3 Test piece preparation .4
6.3.1 General .4
6.3.2 U-notch sawing .5
6.3.3 V-notch honing by machine .6
6.3.4 V-notch honing by hand (optional) .7
6.3.5 Examination of V-notch depth and geometry .8
6.4 Determination of V-notch root width .9
7 Test procedure .10
7.1 Dimensions of test piece .10
7.2 Flexural strength test .10
7.3 Measurement of notch depth .11
7.4 Calculation of fracture toughness . 12
8 Precision and bias .13
9 Test report . 14
Annex A (informative) Interlaboratory evaluation of the SEVNB fracture toughness test
procedures .15
Annex B (informative) Corrections for effective crack length greater than notch depth . 17
Bibliography .18

iii
ISO/DIS 23146:2025(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,
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.
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 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).
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/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
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and expressions
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 [or Project Committee] ISO/TC 206, Fine Ceramics.
This third edition cancels and replaces the second edition (ISO 23146:2012), which has been technically
revised.
The main changes are as follows:
— In Clause 1, three-point bending is added in the scope. The grain size limitation for larger than about 1 μm
is deleted. The scope of application of the document is added. The second paragraph of ISO 23146:2012
is deleted;
— In Clause 2, the normative references ISO 3611 and ISO 7500-1 are updated with the new versions;
— In Clause 3, the terms and definitions 3.1 advanced ceramic, 3.2 monolithic ceramic, 3.3 stress intensity
factor, 3.4 fracture toughness and 3.5 fracture toughness K are added;
Ic, SEVNB
— In Clause 4, the third paragraph of ISO 23146:2012 is deleted;
— In Subclause 5.1, the thickness and the tip angle of the razor blade is added;
— In Subclause 5.9, added the scanning electron microscope and increase the magnifications from “50 × to
1 000 × ” to “100 × to 1 000 × or higher”;
— In Subclause 6.3, add the Subclauses 6.3.1, 6.3.2 and 6.3.3 and their titles; The notch preparation is
divided into U-notch (starter notch) sawing and V-notch honing. Add the recommended V-notch honing
method by machining in 6.3.1. Move the whole Annex A of ISO 23146:2012 to the text of 6.3.3. Change the
V-notch by hand to be optional;
— In Subclause 6.3.2, change starter notch width from ≤ 0,5 mm to ≤ 0,3 mm;
— In Subclause 6.4, add the V-notch root width requirement for test piece with fine grain size: The notch
width should be the same as the major microstructural feature size of the test piece; For the test piece
with an average size of <1,0 μm, the V-notch root width shall be < 7 μm; For the test piece with an average
size between 1,0 μm and 2,0 μm, the V-notch root width shall be less than 10 μm;

iv
ISO/DIS 23146:2025(en)
— In Subclause 7.2, add the recommended displacement rate range of 0,5 mm/min.
3/2
— In Subclause 7.4, correct the error in Formula (9) for S /W = 7,5 by adding the multiplier (1-α) . In
Formula (9) the coefficient of α is corrected from 13,771 4 to 13,711. For three-point flexure, add the Y*
Formulae (8, 10, 11, and 12) for different ratio of support span to the test piece depth (S /W = 8, 7, 6, and
5, respectively). Add the Formula (13) for S /W = 4.
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
DRAFT International Standard ISO/DIS 23146:2025(en)
Fine ceramics (advanced ceramics, advanced technical
ceramics) — Test methods for fracture toughness of monolithic
ceramics — Single-edge V-notch beam (SEVNB) method
1 Scope
This document specifies a method for the determination of the fracture toughness of advanced ceramics by
the single-edge V-notch beam (SEVNB) method. The procedure makes use of SEVNB test pieces, which are
loaded in three-point or four-point bending until failure. This method is applicable to monolithic ceramics
and whisker- or particulate-reinforced ceramics that are regarded as macroscopically homogeneous.
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 14704, Fine ceramics (advanced ceramics, advanced technical ceramics) — Test method for flexural strength
of monolithic ceramics at room temperature
ISO 15732, Fine ceramics (advanced ceramics, advanced technical ceramics) — Test method for fracture
toughness of monolithic ceramics at room temperature by single edge precracked beam (SEPB) method
3 Terms and definitions
For the purposes of this document, the terms, definitions and symbols given in ISO 15732 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
advanced ceramic
advanced technical ceramic
fine ceramic
highly engineered, high performance, predominately non-metallic, inorganic, ceramic material having
specific functional attributes
[SOURCE: ISO 20507:2022, 3.1]
ISO/DIS 23146:2025(en)
3.2
monolithic ceramic
fine ceramic which has undergone consolidation through sintering to obtain a microstructure consisting
predominantly of ceramic grains of one or more phases which are homogeneously distributed on a scale
which is small compared to the dimensions of the part
Note 1 to entry: Ceramic parts with low or moderate porosity are include, whereas ceramic matrix composites with
ceramic filaments are excluded.
Note 2 to entry: A secondary phase can also be non-ceramic.
[SOURCE: ISO 20507:2022, 3.1.51]
3.3
stress intensity factor
K
I
magnitude of the elastic stress field singularity at the tip of a crack subjected to opening mode (Mode I)
displacement
[SOURCE: ISO 20507:2022, 3.1.1]
3.4
fracture toughness
K
Ic
the critical stress intensity factor, Mode I, for fracture. It is a measure of the resistance to rapid crack
extension in brittle materials
3.5
fracture toughness K
Ic, SEVNB
K
Ic, SEVNB
the measured fracture toughness by the SENVB method
4 Principle
This method of conducting a fracture toughness test is based on the preparation and fracture of advanced
ceramics (including monolithic ceramics and whisker- or particulate-reinforced ceramics that are regarded
as macroscopically homogeneous) test pieces in which a sharp-tipped notch is machined. Using the technique
of a reciprocating razor blade and diamond paste, a narrow notch can be honed into a test piece using either
a manual method or a simple machine. Under well-controlled conditions, a notch-tip radius in the range of
1 µm to 20 µm can be prepared depending on the grain size of the test material. For many materials, this is
a close approximation to a sharp crack, and the method has been found to give fracture toughness values
very close to those of other methods such as the single-edge precracked beam method (ISO 15732) or the
[2]
surface crack in flexure method (ISO 18756 ), provided that a sharp crack forms at the root of the notch
either during its preparation or during the subsequent fracture sequence. The method has the advantage of
simplicity of notch production compared with using a sharp-tipped diamond saw or a diamond impregnated
wire in which the tip radius is normally greater than 50 µm. The method is often easier to undertake
compared with other methods of precracking and can be applied to a wider range of materials outside the
scope of these methods.
The method has been extensively researched (see the Bibliography) and has been evaluated in an ESIS
(European Structural Integrity Society)/VAMAS (Versailles Agreement on Advanced Materials and
Standards) round robin, the results of which are summarized in Annex A. This recommended practice is
based upon the ESIS/VAMAS SEVNB round robin.
The method is complementary to other methods of measuring fracture toughness described in ISO 15732
[1] [3]
(single-edge precracked beam method), ISO 18756 (surface crack in flexure method), and ISO 24370
(chevron notch method).
ISO/DIS 23146:2025(en)
5 Apparatus
The usual laboratory apparatus and, in particular, the following shall be used.
5.1 Ordinary razor blades. The thickness of ordinary razor blades shall be less than 0,2 mm. The razor
blades tip angle of 30° or smaller is preferable.
5.2 Metallographic diamond paste, in a viscous organic carrier and of fine grain size, typically 1 µm to 3 µm.
5.3 Lubricant, a light lubricating oil for lubricating the razor blade, e.g. clock oil.
5.4 Test piece support, consisting of a flat plate or other suitable device for mounting test pieces during
notch honing.
5.5 Flexural-strength test fixture, preferably a four-point flexural-strength test fixture operating in
accordance with the requirements of ISO 14704, i.e. either 1/4-point flexure (preferred) or 1/3-point flexure.
Alternatively, a three-point flexural-strength test jig may also be used, but the alignment of the V-notch with
the central loading roller is more critical.
The test piece is supported on two bearing edges perpendicular to its length. The outer-support bearing
edges shall be parallel rollers of diameter 5,0 mm ± 0,2 mm and shall be capable of rolling outward on flat
support surfaces. Preferably, one of the rollers shall additionally be capable of rotating about an axis parallel
to the length of the test piece such that torsional loading is minimised. The two rollers shall be positioned
initially with their axes parallel to within 1°. The separation of the centres of the rollers in their starting
positions shall be measured to the nearest 0,1 mm with a travelling microscope. The rollers shall be made
from hardened steel or other hard material with a hardness greater than 40 HRC (Rockwell C-scale). The
rollers shall have a smooth burr-free surface finish with roughness, Ra, less than 0,5 µm and shall have a
diameter uniform to ±0,02 mm.
For four-point flexure, the two loading rollers are located at the 1/4-points (or 1/3-points), with an inner
span of 20 mm ± 0,2 mm (or 10 mm ± 0,2 mm for 1/3-point flexure) and are free to roll inwards. The rollers
are free to rotate separately about an axis parallel to the length of the test piece to allow alignment. For
three-point flexure, the single loading roller, which need not rotate, shall be positioned centrally between
the outer-support rollers. The distances between the rollers shall be measured to the nearest ±0,1 mm
along the length of the specimen perpendicular to the direction of loading, using a travelling microscope or
other suitable device. The loading rollers in four-point flexure shall be symmetrically positioned to within
±0,1 mm. The arrangement for loading shall ensure that equal forces are applied to the two loading rollers.
The single loading roller in three-point flexure shall be centrally located to within ±0,2 mm.
5.6 Mechanical testing machine, capable of applying a force at a constant rate of displacement or
constant loading rate to the test piece in the flexural-strength test jig and of recording the force at which the
test piece fractures. The force measuring device shall be in accordance with ISO 7500-1 and shall have an
accuracy of 1 % or better.
NOTE The test facility can, with advantage, be equipped with a capability for recording the force/displacement
behaviour of the test piece, ideally a sensitive system directly contacting the test piece. Provided that the load train
stiffness is sufficient, machine displacement recording can be adequate.
5.7 Ultrasonic cleaning bath, for cleaning the test pieces after notching, suitable for insertion of a beaker
or other receptacle containing solvent.
5.8 Calibrated micrometer, similar to the one in accordance with ISO 3611, but capable of being read to a
precision of 0,002 mm using a vernier or electronic readout.
5.9 Optical microscope or scanning electron microscope (SEM), with calibrated magnifications
over the range 100 × to 1 000 × or higher, suitable for observing the notch-tip shape, and fitted with
photomicrographic facilities.
ISO/DIS 23146:2025(en)
5.10 Notch-measuring device, a calibrated device for measuring the depth of the V-notch after fracture
with a reading precision of 0,002 mm.
NOTE This can be achieved by the use of an appropriate travelling microscope, or a conventional metallurgical
microscope with calibrated stage movement, or a microscope with a calibrated micrometer eyepiece.
5.11 Drying oven, capable of maintaining 120 °C ± 5 °C for drying test pieces after cleaning.
5.12 Diamond slitting saw or slitting machine, capable of preparing a U-notch in a set of test pieces of
width no more than 0,3 mm and depth of about 0,5 mm. See 6.3 for guidance.
6 Test piece preparation
6.1 Number of test pieces
At least seven test pieces shall be prepared for notching, of which five are required for testing and two are
dummy test pieces for protecting the others during notch preparation.
Operators with no experience of preparing the sharp V-notches used in this method are highly recommended
to try out the technique and equipment first with surplus test pieces.
6.2 Test piece dimensions
Prepare beam test pieces of rectangular cross-section, preferably in accordance with the requirements of
ISO 14704. Figure 1 shows the shape and main dimensions of the test pieces prepared in accordance with
ISO 14704.
NOTE 1 The chamfering or rounding requirements in ISO 14704 are not essential for the V-notch test, and can be
ignored.
NOTE 2 Other sizes of test pieces, e.g. (2,0 × 2,5 × > 25,0 mm), can optionally be used with appropriately sized
flexural-strength fixtures.
Key
L > 45 mm (1/4-point flexure) or > 35 mm (1/3-point flexure)
W 4,0 mm ± 0,2 mm
B 3,0 mm ± 0,2 mm
Figure 1 — Test piece dimensions in accordance with ISO 14704
6.3 Test piece preparation
6.3.1 General
Test piece preparation contains starter notch (U-notch) sawing and the following V-notch honing. The
V-notch should be machined rather than manually honed. Although manual processing is possible, machine-

ISO/DIS 23146:2025(en)
based honing offers a distinct advantage by providing controlled loading and directional stability to the
razor blade, resulting in sharper and more consistent notches.
NOTE 1 By commencing the notching directly on the flat test-piece surfaces using a razor blade and medium grit size
diamond paste, typically 10 µm, it is possible to avoid saw-notching the test pieces first. When the notch is deep enough,
the notch tip is sharpened using a new blade and fine grit paste, after cleaning out the medium grit from the notch.
6.3.2 U-notch sawing
Mount the test pieces side by side on the test piece support using an appropriate temporary adhesive, as in
Figure 2. Mount test pieces and dummies as close together as possible. Ensure that the top surfaces of the
test pieces are level. Draw a
...