EN 843-1:2006

SLOVENSKI STANDARD
01-maj-2007
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SIST EN 843-1:2000
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Advanced technical ceramics - Mechanical properties of monolithic ceramics at room
temperature - Part 1: Determination of flexural strength
Hochleistungskeramik - Mechanische Eigenschaften monolithischer Keramik bei
Raumtemperatur - Teil 1: Bestimmung der Biegefestigkeit
Céramiques techniques avancées - Propriétés mécaniques des céramiques
monolithiques a température ambiante - Partie 1: Détermination de la résistance en
flexion
Ta slovenski standard je istoveten z: EN 843-1:2006
ICS:
81.060.30 Sodobna keramika Advanced ceramics
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EUROPEAN STANDARD
EN 843-1
NORME EUROPÉENNE
EUROPÄISCHE NORM
December 2006
ICS 81.060.30 Supersedes EN 843-1:1995
English Version
Advanced technical ceramics - Mechanical properties of
monolithic ceramics at room temperature - Part 1: Determination
of flexural strength
Céramiques techniques avancées - Propriétés mécaniques Hochleistungskeramik - Mechanische Eigenschaften
des céramiques monolithiques à température ambiante - monolithischer Keramik bei Raumtemperatur - Teil 1:
Partie 1: Détermination de la résistance en flexion Bestimmung der Biegefestigkeit
This European Standard was approved by CEN on 11 November 2006.
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, Romania,
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
© 2006 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN 843-1:2006: E
worldwide for CEN national Members.

Contents Page
Foreword.3
1 Scope.4
2 Normative references.4
3 Terms and definitions .5
4 Significance and use .5
5 Apparatus.6
5.1 Test jig.6
5.2 Test machine.8
5.3 Micrometer or alternative calibrated device .8
5.4 Travelling microscope.8
5.5 Humidity measuring device .9
6 Test pieces.9
6.1 General.9
6.2 Dimensions and tolerances .9
6.3 Surface finish.10
6.4 Number of test pieces .13
6.5 Precautions.13
7 Procedure.13
8 Calculations.14
9 Test report.15
Annex A (informative) Typical fracture patterns in ceramic test pieces .17
Bibliography .20

Foreword
This document (EN 843-1:2006) has been prepared 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 June 2007, and conflicting national standards shall be withdrawn at
the latest by June 2007.
This document supersedes EN 843-1:1995.
EN 843 Advanced technical ceramics — Mechanical properties of monolithic ceramics at room temperature
comprises six parts:
Part 1: Determination of flexural strength
Part 2: Determination of Young’s modulus, shear modulus and Poisson’s ratio
Part 3: Determination of subcritical crack growth parameters from constant stressing rate flexural strength
tests
Part 4: Vickers, Knoop and Rockwell superficial hardness
Part 5: Statistical analysis
Part 6: Guidance for fractographic investigation
At the time of publication of this Revision of Part 1, Part 6 was available as a Technical Specification.
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, Romania, Slovakia, Slovenia, Spain, Sweden,
Switzerland and United Kingdom.
1 Scope
This part of EN 843 specifies methods for determining the nominal flexural strength of advanced monolithic
technical ceramic materials at ambient temperature. The available loading geometries are three- and four-point
flexure, using rectangular section test pieces of two prescribed geometries: 20 mm support span (A) and 40 mm
support span (B).
NOTE This part of EN 843 differs from ISO 14704 (see Bibliography) in respect of span A (not included in the ISO
version), the absence of the 30 mm span option, and the required use of a fully articulating test jig.
The test applies to materials with grain size less than 200 µm.
The test prescribes four categories of surface finish applied to the test pieces:
I: as-fired or annealed after machining;
II: standard finishing by grinding;
III: standard finishing by lapping/polishing;
IV: machined using agreed grinding procedures and material removal rates.
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 623-4, Advanced technical ceramics — Monolithic ceramics — General and textural properties — Part 4:
Determination of surface roughness
EN 843-5, Advanced technical ceramics — Mechanical properties of monolithic ceramics at room temperature
— Part 5: Statistical analysis
EN ISO 7500-1, Metallic materials — Verification of static uniaxial testing machines — Part 1:
Tension/compression testing machines — Verification and calibration of the force-measuring system (ISO
7500-1:2004)
EN ISO/IEC 17025, General requirements for the competence of testing and calibration laboratories (ISO/IEC
17025:2005)
ISO 3611, Micrometer callipers for external measurement
ISO 4677-1, Atmospheres for conditioning and testing — Determination of relative humidity —
Part 1: Aspirated psychrometer method
ISO 4677-2, Atmospheres for conditioning and testing — Determination of relative humidity —
Part 2: Whirling psychrometer method
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
nominal flexural strength
maximum nominal stress supported by the material at the instant of failure when loaded in linear elastic bending
3.2
three-point flexure
means of bending a beam test piece whereby the test piece is supported on bearings near its ends and a central
force is applied
3.3
four-point flexure
means of bending a beam test piece whereby the test piece is supported on bearings near its ends and is
loaded equally at two positions symmetrically disposed about the centre of the supported span
3.4
quarter-point flexure
four-point flexure (3.3) wherein the loading bearings are each one-quarter of the support span from the
support bearings
4 Significance and use
This test is intended to be used for material development, quality control, characterization and design data
acquisition purposes. The strength level determined by the test is calculated on the basis of linear elastic bending
of a thin beam on the assumption that the material being tested is elastically homogeneous and isotropic, and
shows linear (Hookean) stress-strain behaviour.
The result obtained from a strength test is determined by a large number of factors associated with the
microstructure of the material, the surface finishing procedure applied in preparation of the test pieces, the size
and shape of the test piece, the mechanical function of the testing apparatus, the rate of load application and the
relative humidity of the ambient atmosphere. As a consequence of the brittle nature of ceramics, there is usually a
considerable range of results obtained from a number of nominally identical test pieces. These factors combined
mean that caution in the interpretation of test results is required. For many purposes, and as described in this
European Standard, the results of strength tests may be described in terms of a mean value and a standard
deviation. Further statistical evaluation of results is required for design data acquisition, and may be desirable for
other purposes (see EN 843-5).
This method places closely defined restrictions on the size and shape of the test piece and on the function of the
test apparatus in order to minimize the errors that can arise as a consequence of the test method.
NOTE The basis for the choice of dimensions and tolerances of test pieces and of the requirements of the test-jig
may be found in reference [4].
All other test factors are required to be stated in the test report (see Clause 9) in order to allow inter-comparison of
material behaviours. It is not possible to rigorously standardize particular surface finishes, since these are not
absolutely controllable in mechanical terms. The inclusion of a standard grinding procedure (see 6.3) as one of
the surface finish options in this method is intended to provide a means of obtaining a minimum amount of
residual grinding damage in the test material.
The extrapolation of flexural strength data to other geometries of stressing, to multiaxial stressing, to other rates of
stressing or to other environments should be viewed with caution.
The origin of fracture in a flexural test can be a valuable guide to the nature and position of strength-limiting
defects. Fractography of test pieces is highly recommended. In particular, the test may identify fracture origins as
being edge defects (caused by edge preparation), surface defects (caused by surface preparation), or internal
defects (caused by manufacturing inhomogeneities such as pores, large grains, impurity concentrations etc.). Not
all advanced monolithic technical ceramics are amenable to clear fractography.
5 Apparatus
5.1 Test jig
The test jig shall be capable of either three-point or four-point flexure and functioning as specified below in order
to minimize misalignments, twist and frictional forces applied to the test piece.
NOTE 1 The precise test jig design is not specified, only the function.
Schematic arrangements of the test jig function are shown in Figure 1 a) for three-point flexure, and Figure 1 b) for
four-point flexure.
The test piece shall be supported on two bearing edges perpendicular to its length. The outer support bearing
edges shall be parallel rollers of diameter approximately 1,5 times the test piece thickness. Diameters of between
2,2 mm and 2,5 mm (for span A - see 6.2) or between 4,5 mm and 5,0 mm (for span B - see 6.2) are
recommended. The rollers 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 minimized. The two rollers shall be positioned initially with their centres 20 mm ± 0,5 mm apart (span A) or
40 mm ± 0,5 mm apart (span B) with their axes parallel to 0,2 mm over their lengths (≥ 12 mm). See Figure 2.
For three-point flexure, a third roller shall be located at the mid-point between and parallel to the two support
rollers (Figures 2 a) and 2 c)). This roller shall have the same diameter as the support rollers and shall be similarly
free to rotate about an axis parallel to the length of the test piece. Its position relative to the midpoint between the
support rollers shall be better than 0,2 mm, measured to the nearest 0,1 mm in a direction parallel to the length of
the test piece using the travelling microscope or other suitable device (see 5.4).
For four-point flexure, two loading rollers shall be located at the quarter points (see 3.4), i.e. with inner spans
10 mm ± 0,2 mm (outer span A) or 20 mm ± 0,2 mm (outer span B), and shall be free to roll inwards (Figures 2 b)
and 2 d)). As with the three-point apparatus, the two rollers shall also be free to rotate separately about an axis
parallel to the length of the test piece to allow alignment. The loading rollers shall be symmetrically positioned to
within ± 0,1 mm. The distances between the centres of the support rollers and adjacent loading rollers shall be
measured to the nearest 0,1 mm along the length of the test piece perpendicular to the direction of loading, using
the travelling microscope or other suitable device (see 5.4). The arrangement for loading shall ensure that equal
forces are applied to the two loading rollers.
The separation of the centres of the rollers in their starting positions shall be measured to the nearest 0,1 mm with
the travelling microscope (see 5.3.2) or other suitable device. The rollers shall be made from hardened steel or
other hard material with a hardness greater than 40 HRC (Rockwell C-scale) for strengths less than 1,4 GPa and
not less than 46 HRC for strengths greater than 1,4 GPa. The rollers shall have a smooth burr-free surface finish
with roughness less than 0,5 µm R and shall have diameter uniform to ± 0,015 mm.
a
NOTE 2 The accurate and repeatable lateral positioning of the rollers can best be achieved by ensuring that in the
unloaded position, the support rollers are in lateral contact with stops which allow them to roll outwards on their support
planes towards the ends of the test piece, and the inner loading rollers (four-point flexure) are in contact with stops which
allow rolling inwards towards the middle of the test piece. The rotation of the rollers is thus unhindered when the test force
is applied.
F
F/2
1 2
F/2
a) three-point bend jig
F/2
F/2
F/2
F/2
b) four-point bend jig
Key
1  rolling but non-articulating support roller 2  articulating loading roller
3  rolling and articulating support roller 4  rolling and articulating loading roller
Figure 1 — Schematic diagrams of function of test jigs indicating the articulation and rotation required
for the rollers
Dimension in millimetres
Size A
10 ± 0,2
L L
L L
1 2
±
20,0 ± 0,2 20,0 0,2
a)  Three-point flexure                      b)  Four-point flexure
Size B
L
L
±
20 0,2
1 2
L L
1 2
40 ± 0,5 ±
40 0,5
c)  Three-point flexure                      d)     Four-point flexure
L = L ± 0,2                          L = L ± 0,1
1 2 1 2
Figure 2 — Test span dimensions and tolerances
5.2 Test machine
The test machine shall be capable of applying a force to the loading roller (three-point flexure) or equally to the
two loading rollers (four-point flexure) in order to stress the test piece. The machine shall be capable of applying
the force at a constant loading or displacement rate. The test machine shall be equipped for recording the peak
load applied to the test piece. The accuracy of the test machine shall be in accordance with EN ISO 7500-1,
Grade 1 (accuracy 1 % of indicated load).
5.3 Micrometer or alternative calibrated device
A micrometer conforming to ISO 3611 and with a resolution 0,002 mm, or an alternative calibrated device
measuring to this resolution, shall be used for the measurement of test piece dimensions.
5.4 Travelling microscope
A travelling microscope or other suitable device accurate to 0,05 mm shall be used for the measurement of
distance between loading rollers.
5.5 Humidity measuring device
A humidity measuring device accurate to ± 5 % RH, for example one conforming to ISO 4677-1 or ISO 4677-2
shall be used.
6 Test pieces
6.1 General
The test pieces shall be selected and prepared according to agreement between the parties. They may either be
specially processed to, or close to, the final required dimensions specified below, or may be machined from larger
blocks or components.
NOTE 1 On occasion it may be desirable to test piece geometries that fall outside the scope of this method. In such a
case, although the test method may not be cited, it is still advisable to follow the guidelines given in this European
Standard concerning jig function to minimise errors of measurement.
NOTE 2 The strength of many types of advanced monolithic technical ceramics is strongly influenced by the machining
procedure adopted in the preparation of the test pieces. Low strengths may be caused by grinding with coarse diamond
grit sizes, and conversely, very high strengths may be obtained if care in polishing is taken. Some materials, especially
those
...