SIST-TS CEN/TS 14425-5:2005
(Main)Advanced technical ceramics - Test methods for determination of fracture toughness of monolitic ceramics - Part 5: Single-edge vee-notch beam (SEVNB) method
Advanced technical ceramics - Test methods for determination of fracture toughness of monolitic ceramics - Part 5: Single-edge vee-notch beam (SEVNB) method
This part of CEN/TS 14425 describes a method for the determination of the fracture toughness of advanced technical ceramics. The procedure makes use of V-notched bars, which are loaded in 4-point bending until failure. It is applicable to ceramics with a grain size or major microstructural feature size larger than about 1 µm.
Hochleistungskeramik - Prüfverfahren zur Bestimmung der Bruchzähigkeit von monolithischer Keramik - Teil 5: Verfahren für Biegeproben mit V-Kerb (SEVNB-Verfahren)
Céramiques techniques avancées - Méthodes d'essai pour la détermination de la résistance a la fracture des céramiques monolithiques - Partie 5: Méthode du faisceau a entaille en V sur bord simple (SEVNB)
Sodobna tehnična keramika – Preskusne metode za ugotavljanje odpornosti monolitske keramike proti lomljenju – 5. del: Metoda upogibnega preskusa z V-zarezo (metoda SEVNB)
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Standards Content (Sample)
SLOVENSKI STANDARD
SIST-TS CEN/TS 14425-5:2005
01-januar-2005
6RGREQDWHKQLþQDNHUDPLND±3UHVNXVQHPHWRGH]DXJRWDYOMDQMHRGSRUQRVWL
PRQROLWVNHNHUDPLNHSURWLORPOMHQMX±GHO 0HWRGDXSRJLEQHJDSUHVNXVD]9
]DUH]R PHWRGD6(91%
Advanced technical ceramics - Test methods for determination of fracture toughness of
monolitic ceramics - Part 5: Single-edge vee-notch beam (SEVNB) method
Hochleistungskeramik - Prüfverfahren zur Bestimmung der Bruchzähigkeit von
monolithischer Keramik - Teil 5: Verfahren für Biegeproben mit V-Kerb (SEVNB-
Verfahren)
Céramiques techniques avancées - Méthodes d'essai pour la détermination de la
résistance a la fracture des céramiques monolithiques - Partie 5: Méthode du faisceau a
entaille en V sur bord simple (SEVNB)
Ta slovenski standard je istoveten z: CEN/TS 14425-5:2004
ICS:
81.060.30 Sodobna keramika Advanced ceramics
SIST-TS CEN/TS 14425-5:2005 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
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SIST-TS CEN/TS 14425-5:2005
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SIST-TS CEN/TS 14425-5:2005
TECHNICAL SPECIFICATION
CEN/TS 14425-5
SPÉCIFICATION TECHNIQUE
TECHNISCHE SPEZIFIKATION
August 2004
ICS 81.060.30
English version
Advanced technical ceramics - Test methods for determination
of fracture toughness of monolitic ceramics - Part 5: Single-edge
vee-notch beam (SEVNB) method
Céramiques techniques avancées - Méthodes d'essai pour Hochleistungskeramik - Prüfverfahren zur Bestimmung der
la détermination de la résistance à la fracture des Bruchzähigkeit von monolithischer Keramik - Teil 5:
céramiques monolithiques - Partie 5: Méthode du faisceau Verfahren für Biegeproben mit V-Kerb (SEVNB-Verfahren)
à entaille en V sur bord simple (SEVNB)
This Technical Specification (CEN/TS) was approved by CEN on 4 April 2004 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
© 2004 CEN All rights of exploitation in any form and by any means reserved Ref. No. CEN/TS 14425-5:2004: E
worldwide for CEN national Members.
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Contents Page
Foreword. 3
1 Scope. 4
2 Normative references . 4
3 Terms and definitions. 4
4 Principle . 4
5 Apparatus . 5
5.1 Razor blades. 5
5.2 Diamond paste . 5
5.3 Lubricant. 5
5.4 Test piece support . 5
5.5 Flexural strength test jig . 5
5.6 Mechanical testing machine . 6
5.7 Ultrasonic cleaning bath . 6
5.8 Micrometer. 6
5.9 Microscope . 6
5.10 Notch measuring device. 6
5.11 Drying oven . 6
5.12 Diamond slitting saw . 6
6 Test piece preparation. 7
6.1 Number of test pieces. 7
6.2 Test-piece dimensions . 7
6.3 Preparing the V-notch by hand. 7
6.4 Preparing the V-notches by machine (optional) . 10
7 Test procedure . 10
7.1 Determination of notch root radius. 10
7.2 Dimensions of test-piece. 11
7.3 Flexural strength test. 11
7.4 Measurement of notch depth. 12
7.5 Calculation of fracture toughness. 13
8 Precision and bias . 14
9 Test report . 14
Annex A (informative) Notch honing by machine . 16
Annex B (informative) Interlaboratory evaluation of the SEVNB fracture toughness test
procedures. 17
Bibliography . 19
2
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Foreword
This document (CEN/TS 14425-5:2004) has been prepared by Technical Committee CEN/TC 184
“Advanced technical ceramics”, the secretariat of which is held by BSI.
According to the CEN/CENELEC Internal Regulations, the national standards organizations of the
following countries are bound to announce this 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 the United Kingdom.
CEN/TS 14425 Advanced technical ceramics — Test methods for determination of fracture toughness
of monolithic ceramics consists of five parts:
Part 1: Guide to test method selection
Part 2: Single-edge pre-cracked beam (SEPB) method
Part 3: Chevron notched beam (CNB) (method
Part 4: Surface crack in flexure (SCF) method
Part 5: Single-edge V-notch beam (SEVNB) method
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1 Scope
This part of CEN/TS 14425 describes a method for the determination of the fracture toughness of
advanced technical ceramics. The procedure makes use of V-notched bars, which are loaded in 4-
point bending until failure. It is applicable to ceramics with a grain size or major microstructural feature
size larger than about 1 µm.
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 843-1, Advanced technical ceramics — Monolithic ceramics — Mechanical properties at room
temperature — Part 1: Determination of flexural strength
ENV 1006, Advanced technical ceramics — Monolithic ceramics — Guidance on the selection of test
pieces for the evaluation of properties
CEN/TS 14425-1, Advanced technical ceramics — Test methods for determination of fracture toughness
of monolithic ceramics - Part 1: Guide to test method selection
EN ISO 7500-1, Metallic materials - Verification of static uniaxial testing machines - Part 1:
Tension/compression testing machines (ISO 7500-1:1999)
EN ISO/IEC 17025, General requirements for the competence of testing and calibration laboratories
(ISO/IEC 17025:1999)
ISO 3611, Micrometer callipers for external measurement
3 Terms and definitions
For the purposes of this document, the terms and definitions given in CEN/TS 14425-1 apply.
4 Principle
This method of conducting a fracture toughness test is based on the preparation and fracture of bar
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 pre-cracked beam (SEPB)
method (prCEN/TS 14425-2) or the surface crack in flexure (SCF) method (prCEN/TS 14425-4). The
method has advantages 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 pre-cracking, and is
applicable to a wider range of materials outside the scope of these other methods.
4
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The method has been extensively researched (see Bibliography) and has been evaluated in
1) 2)
ESIS /VAMAS round robin testing, the results of which are summarised in Annex B. This
recommended practice is based upon the ESIS/VAMAS single edge V-notch beam (SEVNB) round
robin testing.
The method may have some limitations for materials with grain sizes of less than 1 µm, for which the
assumption that the notch approximates to a sharp crack may not be valid.
5 Apparatus
5.1 Razor blades
Standard razor blades, preferably with a support along one edge but alternatively inserted into a
suitable holder.
NOTE 1 Razor blades thinner than about 0,2 mm may not be stiff enough by themselves for this task. If the
razor blades are not stiff enough, it is recommended to glue or screw the blades between two steel plates leaving
only about 2 mm of edge showing. It is recommended to use a razor blade with a tip angle of 30°, or smaller.
NOTE 2 Although it is possible to machine the notches entirely by hand, the use of a simple device in which
the test pieces are mounted and in which a razor blade primed with diamond paste is moved in a reciprocating
motion across the mounted test-pieces has a distinct advantage as this provides controlled loading and
directional stability to the razor blade, and sharper notches can generally be produced. An example is shown in
Annex A.
5.2 Diamond paste
Metallographic diamond paste in a viscous organic carrier and of fine grain size, typically 1 µm to
3 µm.
5.3 Lubricant
Suitable lubricating oil for lubricating the razor blade.
5.4 Test piece support
A flat plate or other suitable device for mounting test pieces during notch honing.
5.5 Flexural strength test jig
A three-point or, preferably, four-point flexural strength test jig operating in accordance with the
requirements of EN 843-1. 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. 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 centres 40,0 mm ± 0,5 mm apart 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
1) ESIS = European Structural Integrity Society
2) VAMAS = Versailles Project on Advanced Materials and Standards
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rollers shall have a smooth burr-free surface finish with roughness less than 0,5 µm Ra, and shall
have a diameter uniform to ± 0,02 mm.
For four-point flexure, the two loading rollers are located at the quarter points, with an inner span of
20 mm ± 0,2 mm 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 single loading roller in three-point flexure shall be centrally located to within ± 0,2 mm. The
arrangement for loading shall ensure that equal forces are applied to the two loading rollers.
5.6 Mechanical testing machine
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 EN ISO 7500-1 and shall be
accurate to better than 1 %.
5.7 Ultrasonic cleaning bath
For cleaning the test pieces after notching, an ultrasonic bath suitable for insertion of a beaker or
other receptacle containing solvent.
5.8 Micrometer
A calibrated micrometer similar to 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 Microscope
An optical microscope with calibrated magnifications over the range 50x to 500x suitable for observing
the notch tip shape, and fitted with photomicrographic facilities.
5.10 Notch measuring device
A calibrated device for measuring depth of the sawn notch after fracture to an accuracy of 0,002 mm
or better.
NOTE This can be achieved by 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
Oven capable of maintaining (120 ± 5) °C for drying test-pieces after cleaning.
5.12 Diamond slitting saw
A diamond saw or slitting machine capable of preparing a shallow notch in a set of test-pieces of
depth approximately 0,5 mm and of width approximately 0,5 mm.
6
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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.
NOTE 1 If a machine is used for preparing the V-notches, it may not be necessary to employ the dummy test
pieces to protect a test set of five test pieces.
NOTE 2 Operators with no experience of preparing sharp V-notches used in this method are highly
recommended first to try out the technique and equipment with surplus test pieces.
6.2 Test-piece dimensions
Select materials for the test in accordance with the guidance given in ENV 1006. Prepare bar test-
pieces of rectangular cross section, preferably in accordance with the requirements for a size B test
piece, as defined in EN 843-1. Figure 1 shows the shape and main dimensions of test pieces
prepared in accordance with this standard.
NOTE 1 The chamfering requirements in EN 843-1 are not essential for the V-notch test and can be ignored.
NOTE 2 Size A test pieces can optionally be used.
L B
Size B Size A
L ≥ 45 mm L ≥ 25 mm
W = 4,0 mm ± 0,2 mm W = 2,5 mm ± 0,2 mm
B = 3,0 mm ± 0,2 mm B = 2,0 mm ± 0,2 mm
Figure 1 — Test piece dimensions in accordance with EN 843-1
6.3 Preparing the V-notch by hand
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 pencil line across the set of test pieces at the mid-point of
their length to indicate where the notch is to be prepared.
NOTE 1 It is recommended to avoid bending the test pieces while mounting on the holder.
7
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11
22
33
22
44
Key
1 Mounting plate
2 Dummy test pieces
3 Test pieces for testing
4 Pencil line as a guide for introducing a diamond sawn starter notch
Figure 2 — Mounting procedure for the set of test pieces
Mount the holder on a diamond saw. Saw a starter notch along the pencil line of width approximately
0,5 mm. The notch should have the same depth of about 0,5 mm over its entire length. Figure 3
shows a schematic arrangement for sawing. After sawing, clean the holder, test pieces and especially
the notch.
NOTE 2 The width of the
...
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