SIST EN ISO 15732:2005
(Main)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 (ISO 15732:2003)
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 (ISO 15732:2003)
ISO 15732:2003 describes a test method for the determination of fracture toughness of monolithic ceramic materials at room temperature by the Single-Edge-Precracked-Beam (SEPB) method.
This International Standard is intended for use with monolithic ceramics and whisker- or particulate-reinforced ceramics which are regarded as macroscopically homogeneous. It does not include continuous-fiber-reinforced ceramic composites.
ISO 15732:2003 is for material development, material comparison, quality assurance, characterization, reliability and design data generation.
Fracture toughness values determined with other test methods cannot be interchanged with KIpb as defined in this International Standard, and may not be interchangeable with each other.
Hochleistungskeramik - Prüfverfahren zur Bestimmung der Bruchzähigkeit monolithischer Keramik bei Raumtemperatur an einseitig gekerbten Biegeproben (SEPB-Verfahren) (ISO 15732:2003)
Diese Internationale Norm legt ein Prüfverfahren zur Bestimmung der Bruchzähigkeit monolithischer
keramischer Werkstoffe fest, das bei Raumtemperatur an einseitig gekerbten Biegeproben (SEPB-Verfahren)
durchgeführt wird.
Diese Internationale Norm ist für die Anwendung auf monolithische Keramiken und durch Whisker oder
Teilchen verstärkte Keramiken vorgesehen, die makroskopisch als homogen angesehen werden. Keramische
Verbundwerkstoffe mit Endlosfaserverstärkung werden nicht erfasst.
Die vorliegende Internationale Norm ist zur Entwicklung dieser keramischen Werkstoffe, für Vergleiche
zwischen keramischen Werkstoffen, zur Qualitätssicherung, für Beschreibungen, für die Zuverlässigkeit und
die Gestaltung der ermittelten Daten anwendbar.
Bruchzähigkeitswerte, die nach anderen Prüfverfahren bestimmt werden, können nicht gegen den in dieser
Internationalen Norm definierten Bruchzähigkeitswert K lpb ausgetauscht werden, und es kann sein, dass sie
überhaupt nicht miteinander austauschbar sind.
Die in dieser Internationalen Norm angegebenen Werte entsprechen dem Internationalen
Einheitensystem (SI).
Céramiques techniques - Méthode d'essai de ténacité a la rupture des céramiques monolithiques a température ambiante sur éprouvette préfissurée sur une seule face (méthode SEPB) (ISO 15732:2003)
L'ISO 15732:2003 décrit une méthode d'essai pour la détermination de la ténacité à la rupture des matériaux céramiques monolithiques à température ambiante sur éprouvette préfissurée sur une seule face (méthode SEPB).
La présente Norme internationale est destinée à être utilisée avec les céramiques monolithiques et les céramiques à renfort de trichite ou de particules qui sont considérées comme macroscopiquement homogènes. Elle ne traite pas des composites en céramiques renforcés de fibres continues.
L'ISO 15732:2003 est applicable au développement et à la comparaison de matériaux, à l'assurance qualité, à la caractérisation, à la fiabilité et à la génération de données de fabrication.
Les valeurs de la ténacité à la rupture déterminées à l'aide d'autres méthodes d'essai ne peuvent être utilisées à la place de la valeur KIpb telle que définie dans la présente Norme internationale et ne sont pas interchangeables.
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 (ISO 15732:2003)
General Information
Standards Content (Sample)
SLOVENSKI STANDARD
SIST EN ISO 15732:2005
01-november-2005
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 (ISO 15732:2003)
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 (ISO 15732:2003)
Hochleistungskeramik - Prüfverfahren zur Bestimmung der Bruchzähigkeit
monolithischer Keramik bei Raumtemperatur an einseitig gekerbten Biegeproben (SEPB-
Verfahren) (ISO 15732:2003)
Céramiques techniques - Méthode d'essai de ténacité a la rupture des céramiques
monolithiques a température ambiante sur éprouvette préfissurée sur une seule face
(méthode SEPB) (ISO 15732:2003)
Ta slovenski standard je istoveten z: EN ISO 15732:2005
ICS:
81.060.30 Sodobna keramika Advanced ceramics
SIST EN ISO 15732:2005 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
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SIST EN ISO 15732:2005
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SIST EN ISO 15732:2005
EUROPEAN STANDARD
EN ISO 15732
NORME EUROPÉENNE
EUROPÄISCHE NORM
June 2005
ICS 81.060.30
English version
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 (ISO 15732:2003)
Céramiques techniques - Méthode d'essai de ténacité à la Hochleistungskeramik - Prüfverfahren zur Bestimmung der
rupture des céramiques monolithiques à température Bruchzähigkeit monolithischer Keramik bei
ambiante sur éprouvette préfissurée sur une seule face Raumtemperatur an einseitig gekerbten Biegeproben
(méthode SEPB) (ISO 15732:2003) (SEPB-Verfahren) (ISO 15732:2003)
This European Standard was approved by CEN on 2 June 2005.
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 Central Secretariat 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 Central Secretariat has the same status as the official
versions.
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. EN ISO 15732:2005: E
worldwide for CEN national Members.
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SIST EN ISO 15732:2005
EN ISO 15732:2005 (E)
Foreword
The text of ISO 15732:2003 has been prepared by Technical Committee ISO/TC 206 "Fine
ceramics" of the International Organization for Standardization (ISO) and has been taken over as
EN ISO 15732:2005 by Technical Committee CEN/TC 184 "Advanced technical ceramics", the
secretariat of which is held by BSI.
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 December 2005, and conflicting national
standards shall be withdrawn at the latest by December 2005.
This document is part of a series:
CEN/TS 14425-1 Advanced technical ceramics — Test methods for determination of fracture
toughness of monolithic ceramics — Part 1: Guide to test method selection
CEN/TS 14425-3 Advanced technical ceramics — Test methods for determination of fracture
toughness of monolithic ceramics — Part 3: Chevron notched beam (CNB) method
CEN/TS 14425-5 Advanced technical ceramics — Test methods for determination of fracture
toughness of monolithic ceramics — Part 5: Single-edge V-notch beam (SEVNB) method
EN 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
EN ISO 18756 Fine ceramics (advanced ceramics, advanced technical ceramics) —
Determination of fracture toughness of monolithic ceramics at room temperature by the surface
crack in flexure (SCF) method
According to the CEN/CENELEC Internal Regulations, the national standards organizations of the
following countries are bound to implement this European Standard: 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.
Endorsement notice
The text of ISO 15732:2003 has been approved by CEN as EN ISO 15732:2005 without any
modifications.
2
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SIST EN ISO 15732:2005
INTERNATIONAL ISO
STANDARD 15732
First edition
2003-09-01
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
Céramiques techniques — Méthode d'essai de ténacité à la rupture des
céramiques monolithiques à température ambiante sur éprouvette
préfissurée sur une seule face (méthode SEPB)
Reference number
ISO 15732:2003(E)
©
ISO 2003
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SIST EN ISO 15732:2005
ISO 15732:2003(E)
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ii © ISO 2003 — All rights reserved
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SIST EN ISO 15732:2005
ISO 15732:2003(E)
Contents Page
Foreword. iv
1 Scope. 1
2 Normative references . 1
3 Terms and definitions. 2
4 Symbols and designations. 3
5 Principle . 3
6 Apparatus. 4
7 Test specimens . 7
8 Test methods. 8
9 Evaluation of validity of measured value . 13
10 Calculation. 14
11 Test report. 15
Annex A (informative) Precracking fixture. 16
Annex B (informative) Recommended procedures in SEPB method. 18
Bibliography . 21
© ISO 2003 — All rights reserved iii
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SIST EN ISO 15732:2005
ISO 15732:2003(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.
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 15732 was prepared by Technical Committee ISO/TC 206, Fine ceramics.
iv © ISO 2003 — All rights reserved
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SIST EN ISO 15732:2005
INTERNATIONAL STANDARD ISO 15732:2003(E)
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
1 Scope
This International Standard describes a test method for the determination of fracture toughness of monolithic
ceramic materials at room temperature by the Single Edge Precracked Beam (SEPB) method.
This International Standard is intended for use with monolithic ceramics and whisker- or particulate-reinforced
ceramics which are regarded as macroscopically homogeneous. It does not include continuous-fiber-
reinforced ceramic composites.
This International Standard is for material development, material comparison, quality assurance,
characterization, reliability and design data generation.
Fracture toughness values determined with other test methods cannot be interchanged with K as defined in
Ipb
this International Standard, and may not be interchangeable with each other.
Values expressed in this International Standard are in accordance with the International System of Units (SI).
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.
ISO 1101:1983, Technical drawings — Geometrical tolerancing — Tolerancing of form, orientation, location
and run-out — Generalities, definitions, symbols, indications on drawings
ISO 3312:1987, Sintered metal materials and hardmetals — Determination of Young modulus
ISO 4287:1997, Geometrical Product Specifications (GPS) — Surface texture: Profile method — Terms,
definitions and surface texture parameters
ISO 6507-1:1997, Metallic materials — Vickers hardness test — Part 1: Test method
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SIST EN ISO 15732:2005
ISO 15732:2003(E)
3 Terms and definitions
For the purpose of this document, the following terms and definitions apply.
3.1
stress intensity factor
K
I
magnitude of the elastic stress field singularity at the tip of a crack subjected to opening mode displacement
NOTE It is a function of applied force and test specimen size, geometry and crack length, and has the dimensions of
−3/2
force times length .
3.2
fracture toughness
generic term for the magnitude of resistance to crack extension
3.3
fracture toughness value
K
Ipb
fracture toughness value measured by the SEPB method
NOTE This represents the measured stress intensity factor corresponding to the extension resistance of a straight-
through pop-in crack formed via bridge loading of a Vickers indent or a saw notch. The measurement is performed in
accordance with the operational procedure described in Clauses 5 and 10 and satisfies all the validity requirements.
3.4
precrack
crack induced artificially into a specimen, primarily so as to measure the fracture toughness
3.5
precrack front line
line to indicate the position of the tip of the precrack
3.6
pop-in
phenomenon where a crack arrests after sudden and unstable growth giving rise to an acoustic signature
3.7
three-point bending
loading configuration where a beam specimen is loaded at a location midway between two support pins
3.8
four-point bending
loading configuration where a beam specimen is symmetrically loaded at two locations that are situated one
quarter of the overall span away from the outer two support pins
3.9
compliance
reciprocal of the gradient of the load versus deflection curve
NOTE Accordingly, as the crack extends, the increase of deflection results in an increase of compliance.
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SIST EN ISO 15732:2005
ISO 15732:2003(E)
4 Symbols and designations
The symbols used throughout this International Standard and their designations are given in Table 1.
Table 1 — Symbols and designations
Symbol Unit Designation References
b
mm Width of central groove in anvil A.2.3, Fig. A.1
d mm Thickness of specimen 7.1, Fig. 3
d mm Distance between supporting roller pins in bend test fixture (lower 6.4, Fig. 2
1
span)
d mm Distance between loading roller pins in four-point bend test fixture 6.4, Fig. 2
2
(upper span)
1/2
K Critical stress intensity factor measured by the SEPB method Clause 10, Eqs. 7 and 10
Ipb MPa⋅m
l mm Length of precrack 8.7.3, Fig. 6, Eq. 2
∆l mm Stable crack growth length 8.7.4, Fig. 6, Eq. 3
L mm Length of specimen 7.1, Fig. 3
L mm Length of bottom surface of specimen positioning groove of anvil A.2.3, Fig. A.1
a
(including the width, b, of central groove)
L mm Length of lower surface of loading plate A.2.3, Fig. A.1
p
P
N Maximum load during fracture of specimen 8.5.3, Fig. 5
f
w mm Width (depth) of specimen 7.1, Fig. 3
1 Compliance change 8.6, Eq. 1
λ∆l / λl
5 Principle
This method is to obtain the fracture toughness value, K , from the precrack length, specimen dimensions
Ipb
and distance between the bending supports by measuring the fracture load of specimen according to the
three or four-point bending fracture test of a single-edge-precracked beam specimen. A straight-through pop-
in precrack is induced in the specimen via bridge loading of a Vickers indent or a saw notch. Generally, this
test is carried out under conditions of ambient temperature and environment.
© ISO 2003 — All rights reserved 3
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SIST EN ISO 15732:2005
ISO 15732:2003(E)
6 Apparatus
6.1 Precracking fixture
An appropriate apparatus is required to induce a pop-in precrack in the specimen in such a way that the crack
front is approximately parallel to the specimen surface.
An example of the basic components of the bridge compression precracking fixture are a loading plate with a
ball seat, an anvil with a central groove and a specimen-positioning groove, and a loading ball as shown in
Figure 1. The shapes of the loading plate and the anvil to be used are symmetric from right to left, and from
front to rear, and have depth exceeding at least three times the thickness of the specimen, d. The horizontal
distance between the centre of the loading ball and the centre of the anvil is less than 0,1 mm.
NOTE Annex A contains recommendations for the typical design of a suitable bridge compression fixture that has
been found to work satisfactorily for most types of ceramic materials.
Key 5 lower loading plate; e.g., of silicon nitride with mirror
polished lower surface (joined to upper loading plate)
1 compression load
6 specimen
2 loading ball
7 central groove
3 loading plate
8 specimen positioning groove
4 upper loading plate; e.g., of hardened steel with ball
seat 9 anvil; e.g., of hardened steel (HV 10 > 5 GPa)
Figure 1 — Example of bridge compression precracking fixture
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SIST EN ISO 15732:2005
ISO 15732:2003(E)
6.2 Precrack introduction loading apparatus
The loading apparatus shall be capable of smoothly applying the compression load to the fixture. High load
accuracy is not required.
6.3 Bend testing machine
A material testing machine capable of maintaining the cross-head-speed constant shall be used. The
accuracy of load measurement shall be ± 1 % over the entire range of load.
The rigidity of the entire testing system, including the bending test fixture specified in 6.4, shall be 3 MN/m or
more against the load applied to the bending test fixture.
The rigidity of the entire testing system, including the testing machine, loading rods and bending test fixture,
should be evaluated in accordance with Annex B.
6.4 Bend test fixture
The general features of the bend test fixtures are illustrated in Figure 2. The bend test fixture shall be
symmetrical about the centre line shown and have a depth exceeding at least three times the thickness, d, of
the specimen to be used. The fixture is designed to minimize frictional effects by allowing the support roller to
roll apart slightly as the specimen is loaded, thus permitting rolling contact and avoiding frictional wedging of
the specimen.
The roller pins are placed in the positioning grooves of the support member and of the loading member as
shown in Figure 2. The rollers shall be parallel to each other to within 0,015 mm over a length equal to the
specimen thickness, d. Other types of fixtures are acceptable, however, roller pins shall be free to roll. The
length of each roller pin shall be equal to at least three times the specimen thickness. Materials composing
the parts of the roller pins to be used shall have a modulus of elasticity not less than 196 GPa, as defined in
ISO 3312 and a hardness of not less than 5 GPa Vickers (HV10) as defined in ISO 6507-1, and made of a
material free from plastic deformation and risk of fracture. The radius of curvature of rollers and the distance
between the rollers shall be as shown in Figure 2. The surface roughness of the rollers, Ra, as defined in
ISO 4287 shall be not more than 0,4 µm.
6.5 Compliance change measuring device
At the time of the bend test, the relation between the deflection of the test specimen and the load shall be
measured by using the deflection meter which can measure the load point deflection between the centre of
two supporting roller pins of the bend test fixtures and the centre of loading roller pin(s). The deflection
measuring device shall have a resolution greater than 0,001 mm, and shall be calibrated to read within
0,001 mm of the true displacement. Measurements of displacement shall be made to a precision of 0,001 mm.
6.6 Measuring instruments
Three fundamental measurements are necessary for the calculation of K namely, the width, w, the
Ipb,
thickness, d, and the precrack length, l.
Measuring devices such as micrometers or other devices having an accuracy of at least 0,01 mm shall be
used for measuring the linear dimensions.
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SIST EN ISO 15732:2005
ISO 15732:2003(E)
Key 4 specimen (I or II)
1 loading ball 5 precrack
2 loading member 6 supporting roller pins
3 loading roller pin 7 support member
a) Three-point bend test fixture
Key 4 specimen (II or III)
1 loading ball 5 precrack
2 loading member 6 supporting roller pins
3 loading roller pins 7 support member
b) Four-point bend test fixture
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SIST EN ISO 15732:2005
ISO 15732:2003(E)
Dimensions in millimetres
Diameters of
d (lower span) d (upper span)
Bending mode Specimen
1 2
roller pins
3-point bend I 4,0 to 5,0 16 ± 0,2 –
3-point bend II 4,0 to 5,0 30 ± 0,3 –
4-point bend II 4,0 to 5,0 30 ± 0,3 10 ± 0,2
4-point bend III 4,0 to 5,0 40 ± 0,4 20 ± 0,2
Figure 2 — Bend test fixtures
7 Test specimens
7.1 Shape and dimensions of specimen, and chamfering of edge
The shape of the specimens shall be that of a rectangular beam and its dimensions shall be as shown in
Figure 3. Sampling position and orientation of specimen removal from raw material shall be recorded.
The opposing faces of the specimen shall be parallel to each other and the faces shall intersect
perpendicularly. The maximum variation in parallelism and perpendicularity shall not exceed 0,01 mm as
defined in ISO 1101.
Further, the four long edges of each specimen shall be chamfered uniformly at 45° ± 5°.The chamfered edge
length shall be 0,12 mm ± 0,03 mm, as shown in Figure 3 (hereafter, a specimen of 18 mm or more in length
is referred to as “specimen I”, a specimen of 36 mm or more in length, as “specimen II”, and a specimen of
45 mm or more in length, as “specimen III”).
Dimensions in millimetres
Specimen Total length, L Width, w Thickness, d Chamfering, C
W 18
I
4 ± 0,1 3 ± 0,1 0,12 ± 0,03
W 36
II 4 ± 0,1 3 ± 0,1 0,12 ± 0,03
W 45
III 4 ± 0,1 3 ± 0,1 0,12 ± 0,03
Figure 3 — Dimensions of specimen
7.2 Surface roughness of upper and lower surfaces and both side surfaces of specimen
The surface roughness of the four surfaces of the specimen, Ra, as defined in ISO 4287 excluding both end
surfaces in the length direction shall be not more than 0,2 µm.
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SIST EN ISO 15732:2005
ISO 15732:2003(E)
7.3 Number of specimens
The number of specimens shall be not less than five pieces. All specimens shall comply with the specification
given in 9.1.
8 Test methods
8.1 Measurement of thickness and width of specimen
The measurement of thickness and width of specimen shall be carried out using a micrometer or other device
accurate to the nearest 0,01 mm.
8.2 Introduction of precrack starter
8.2.1 General
As the precrack generating start point, a Vickers indentation (or Knoop indentation) or notch near the middle
of the d × L surface of the specimen in a direction within 2° of the normal direction to the w × L surface shall
be induced according to the schematic diagram in Figure 4. The recommended conditions for introduction of
the precrack starter are given in 8.2.2 and 8.2.3.
NOTE The position of the precrack starter in the lengthwise direction is not specified, but the positioning is important
for precrack introduction (see Annex B).
8.2.2 The use of Vickers indentation (or Knoop indentation)
8.2.2.1 Position of indentation
One point shall be at the middle of the d × L plane of the specimen. Additional points shall be placed
symmetrically on both sides of the first indent.
8.2.2.2 Direction of indentation
The diagonal line of the Vickers indentation (or major axis of Knoop indentation) shall intersect
perpendicularly the lengthwise direction of specimen.
8.2.2.3 Indentation load
Select an indentation force adequate to produce straight cracks from the corners of the indentation without
causing extensive ancillary damage.
An indentation force of 98 N (or 100 N) is adequate to induce a starter crack in most materials. If this force
produces excessive damage, e.g. in relative soft or brittle materials, use a lower force. If precracking using an
indentation prepared using a force of 98 N (or 100 N) is unreliable, increase the number of adjoining
indentations across the specimen width rather than increasing the force. However, where introduction of a
precrack is impossible, the notch method may be used.
8.2.3 The use of a straight-through saw notch
8.2.3.1 Width of notch
The width of the notch shall be not more than 0,1 mm. The shape of the tip of the notch is not specified.
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SIST EN ISO 15732:2005
ISO 15732:2003(E)
8.2.3.2 Depth of notch
The depth of the notch shall not exceed 0,6 mm and be 0,4 mm ± 0,2 mm.
NOTE If a notch depth exceeding 0,6 mm is used, stable crack growth, instead of pop-in, may occur from the notch
tip during precrack introduction. Fracture toughness values measured from the stably grown precrack might be greater
than the fracture toughness measured under this procedure.
Dimensions in millimetres
Key
1 specimen
2 Vickers (or Knoop) indentation(s)
3 notch
Figure 4 — Introduction of Vickers indentation or notch
8.3 Introduction of precrack
8.3.1 Arrange the specimen with the previously induced precrack starter, between the loading plate of the
precrack inducing fixture and the anvil as shown in Figure 1. Introduce an unstably grown pop-in crack. The
d × L surface contacts with the loading plate and the specimen positioning groove of the anvil. The procedure
is given in 8.3.2 to 8.3.5.
NOTE A recommended precracking fixture is shown in detail in the Annex A. A recommended procedure for precrack
introduction is shown in detail in the Annex B.
8.3.2 Sufficiently clean the specimen, the bottom surface of specimen positioning groove of the precracking
anvil and the lower surface of loading plate by wiping off any oil and stains using acetone. Place the specimen
in the specimen positioning groove of the anvil as shown in Figure 1, taking care to arrange the specimen so
that the lengthwise direction of the specimen intersects perpendicularly the central groove of the anvil, and the
precrack starter positions in the range of ± 0,1 mm from the centre of the central groove.
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SIST EN ISO 15732:2005
ISO 15732:2003(E)
8.3.3 Place the loading plate on the specimen, making sure that the specimen does not slide. The loading
plate and the anvil shall be arranged symmetrically.
8.3.4 Using the loading ball and anvil, increase the compression load vertically to the loading plate. Stop
loading immediately after the pop-in sound is detected, because an excessive compression load may damage
the fixtures and cause uneven development of precrack. The speed at which to apply a compression load is
recommended to be in the range 300 N/s to 1 000 N/s.
NOTE 1 For materials with a rising R-curve the measured fracture toughness value might be artificially high if stable
crack growth occurs after pop-in.
NOTE 2 Sonic sensors, e.g. an acoustic emission sensor or a stethoscope, are useful for detecting the pop-in during
precracking. See Annex B.
8.3.5 Remove the specimen from the fixture and confirm that the precrack has been induced on both side
surfaces. If the precrack is difficult to locate, a dye penetrant, e.g. oil based paint mixed with acetone, may be
used to improve visibility. If a dye penetrant is used, the following bend test shall be carried out after complete
drying of the dye penetrant.
8.4 Test atmosphere
The bend test is carried out under conditions of ambient temperature and environment. If susceptibility to
environmental degradation, such as slow crack growth during the bend test, is a concern, environmental
effects shall be evaluated by measuring both the compliance change and the stable crack growth length
specified in 8.6 and 8.7.
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