SIST EN 820-1:2004

SLOVENSKI STANDARD
SIST EN 820-1:2004
01-januar-2004
1DGRPHãþD
SIST ENV 820-1:2000
Advanced technical ceramics - Methods of testing monolithic ceramics -
Thermonechanical properties - Part 1: Determination of flexural strength at
elevated temperatures
Advanced technical ceramics - Methods of testing monolithic ceramics -
Thermonechanical properties - Part 1: Determination of flexural strength at elevated
temperatures
Hochleistungskeramik - Monolithische Keramik - Thermomechanische Eigenschaften -
Teil 1: Bestimmung der Biegefestigkeit bei erhöhten Temperaturen
Céramiques techniques avancées - Méthode d'essai des céramiques monolithiques -
Propriétés thermodynamiques - Partie 1: détermnation de la résistance a la flexion a
températures élevées
Ta slovenski standard je istoveten z: EN 820-1:2002
ICS:
81.060.30 Sodobna keramika Advanced ceramics
SIST EN 820-1:2004 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST EN 820-1:2004

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SIST EN 820-1:2004
EUROPEAN STANDARD
EN 820-1
NORME EUROPÉENNE
EUROPÄISCHE NORM
October 2002
ICS 81.060.30 Supersedes ENV 820-1:1993
English version
Advanced technical ceramics - Methods of testing monolithic
ceramics - Thermonechanical properties - Part 1: Determination
of flexural strength at elevated temperatures
Céramiques techniques avancées - Méthode d'essai des Hochleistungskeramik - Monolithische Keramik -
céramiques monolithiques - Propriétés thermodynamiques Thermomechanische Eigenschaften - Teil 1: Bestimmung
- Détermination de la résistance à la flexion à températures der Biegefestigkeit bei erhöhten Temperaturen
élevées
This European Standard was approved by CEN on 8 August 2002.
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 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 Management Centre has the same status as the official
versions.
CEN members are the national standards bodies of Austria, Belgium, Czech Republic, Denmark, Finland, France, Germany, Greece,
Iceland, Ireland, Italy, Luxembourg, Malta, Netherlands, Norway, Portugal, 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
© 2002 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN 820-1:2002 E
worldwide for CEN national Members.

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SIST EN 820-1:2004
EN 820-1:2002 (E)
Contents
page
Foreword.3
1 Scope .4
2 Normative references .4
3 Terms and definitions.4
4 Apparatus .5
4.1 General.5
4.2 Test jig.5
4.3 Heating device.6
4.4 Test machine .6
4.5 Linear measuring devices.6
4.6 Drying oven .7
5 Test pieces.7
6 Test temperatures and number of tests .7
7 Test procedure .7
8 Calculations.8
9 Accuracy and references .9
10 Test report .10
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SIST EN 820-1:2004
EN 820-1:2002 (E)
Foreword
This document EN 820-1:2002 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 April 2003, and conflicting national standards shall be withdrawn at the latest by
April 2003.
This document supersedes ENV 820-1:1993.
This document has been prepared under a mandate given to CEN by the European Commission and the European
Free Trade Association.
EN 820 'Advanced technical ceramics – Methods of testing monolithic ceramics – Thermomechanical properties'
consists of three Parts:
 Part 1 : Determination of flexural strength at elevated temperatures
 Part 2 : Determination of self-loaded deformation
 Part 3 : Determination resistance to thermal shock by water quenching
According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following
countries are bound to implement this European Standard: Austria, Belgium, Czech Republic, Denmark, Finland,
France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Malta, Netherlands, Norway, Portugal, Spain,
Sweden, Switzerland and the United Kingdom.
3

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SIST EN 820-1:2004
EN 820-1:2002 (E)
1 Scope
This Part of this European Standard specifies a method of determining the three-point or four-point flexural strength of
advanced monolithic technical ceramics at elevated temperatures as agreed between parties to the test. The test can
be performed in any appropriate atmosphere.
2 Normative references
This European Standard incorporates by dated or undated reference, provisions from other publications. These
normative references are cited at the appropriate places in the text, and in the publications listed hereafter. For dated
references, subsequent amendments to or revisions of any of these publications apply to this European Standard only
when incorporated in it by amendment or revision. For undated references the latest edition of the publication referred
to applies (including amendments).
EN 843-1, Advanced technical ceramics – Monolithic ceramics – Mechanical tests at room temperature – Part 1:
Determination of flexural strength.
ENV 843-5, Advanced technical ceramics – Monolithic ceramics – Mechanical tests at room temperature – Part 5:
Statistical analysis of fracture data.
EN 10002-2, Metallic materials – Tensile testing – Part 2: Verification of the force measuring system of the tensile
testing machine.
EN ISO 17025, General requirements for the competence of testing and calibration laboratories.
IEC 60584, Thermocouples - Part 1: Reference tables.
IEC 60584, Thermocouples - Part 2: Tolerances.
ISO 3611, Micrometer callipers for external measurement.
3 Terms and definitions
For the purposes of this European Standard, the following terms and definitions apply.
3.1
nominal flexural strength
maximum nominal stress at the instant of failure supported by the material when loaded in elastic bending
NOTE It is recognised that flexural strength tests on ceramics at elevated temperature may reveal inelastic behaviour in
the material. Under such conditions, the nominal flexural strength calculated in accordance with this standard is not strictly a
valid result, since it tends to overestimate the true surface stress in the test piece. This method requires that the
load/displacement relationship for each test piece at each temperature is inspected, and the validity of the result determined.
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 load
is applied
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SIST EN 820-1:2004
EN 820-1:2002 (E)
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 points symmetrically disposed about the centre of the supported span
3.4
inelastic deformation
for the purposes of the test, the deformation of a test specimen under load which is not entirely elastic and reversible on
removal of the load
3.5
subcritical crack growth
extension of existing cracks or flaws under a stress which does not produce instant failure
NOTE This effect can be due to the intrinsic crack propagation of the material, additionally influenced by the environment.
4 Apparatus
4.1 General
The test is carried out in a similar manner to that prescribed in EN 843-1 for testing at room temperature, with the
exceptions that the test jig shall be constructed from materials which are capable of remaining linearly elastic at the
temperature of testing, and that a means of heating the test jig and test piece to the test temperature is required.
4.2 Test jig
The test jig shall be of a design that allows full articulation for alignment of the support and loading rollers on the
surfaces of the test piece, and in which the rollers are capable of rolling to minimise friction between the rollers and the
test piece.
NOTE 1 It is recognised that –practical limitations can restrict the design of the test jig, and oxidation effects can restrict its
function. In such cases, alternatives may be employed, but deviations from the function specified above should be reported in
the report (see clause 10, d)).
The outer span of the test jig shall be either 20,0 mm ± 0,5 mm (span A) or 40,0 mm ± 0,5 mm (span B). For three-point
flexure the loading roller shall be centralised relative to the span to within 0,2 mm. For four-point flexure, the inner span
shall be 10,0 ± 0,2 mm (span A) or 20,0 mm ± 0,2 mm (span B). The inner rollers shall be symmetrically positioned
relative to the outer rollers to better than 0,2 mm.
NOTE 2 This represents a relaxation of centralisation requirements compared with room temperature testing (requirement
0,1 mm, see EN 843-1) because it can become relatively more difficult to set up test jigs inside furnaces.
Measurements of the positions of the rollers shall be made with a travelling microscope (4.5.2).
The rollers shall be made from a material which is capable of remaining linearly elastic up to the maximum temperature
of the series of tests. For tests to 400 °C, hardened steel rollers as in EN 843-1 shall suffice. For higher temperatures it
is recommended that the test jig is constructed from fine-grained strong refractory ceramic materials.
NOTE 3 For temperatures up to 1 400 °C, high-purity high-alumina ceramic materials can be used. For temperatures up to 1
°
500 °C in air or up to 1700 C in neutral atmospheres, sintered silicon carbide is recommended.
Consideration should be given to any potential reaction between the test material and the rollers at the maximum test
temperature, and the choice of roller material shall be made such that reactions are minimised. In particular, non-oxide
ceramic materials may tend to oxidise, and the oxide then may react with the loading rollers. Rollers shall be
maintained with a clean smooth burr-free surface for all tests. They shall be inspected before any test to ensure they
are undamaged, and are capable of rolling freely in the jig at the start of the test. If necessary, rollers should be
replaced to maintain correct jig function. Similarly, reactions between the main ceramic components of the test jig shall
be minimized by appropriate choice of material.
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SIST EN 820-1:2004
EN 820-1:2002 (E)
NOTE 4 At very high temperatures, the progressive oxidation of non-oxide jig components can lead to the development of
frictional effects due to inability of the rollers to roll freely. Such effects can lead to uncertainties in nominal flexural strength of
up to 5%. It is not possible to quantify this effect, which is likely to be time, temperature and material dependent. Jig components
can be found to have welded together on cooling to room temperature. They should be gently separated and cleaned before re-
use.
The load shall be applied to the test jig through solid or hollow columns which are loaded by the test machine. These
columns shall be of a material which remains linearly elastic to the maximum testing temperature.
NOTE 5 To ascertain this, the columns of the test jig can be brought into contact at the appropriate test temperature with or
without the jig in place. A load equivalent to that estimated to be needed to fracture test pieces is applied, and the apparent load
displacement relationship is examined for evidence of non-linearity with increasing load (see clause 8).
4.3 Heating device
The test jig shall be contained within a furnace or suitable heating device of design appropriate to the maximum
temperature for the tests, and capable of reaching the maximum testing temperature within 3 h.
NOTE 1 The use of very fast heating rates is not recommended because of risk of fracture of ceramic components in the test
jig or columns.
The temperature control system used with the furnace shall be capable of controlling to within ± 5 °C using a suitable
thermocouple. The temperature of the test piece shall be recorded using a second thermocouple manufactured in
accordance with the manufacturing tolerances stated in IEC 60584-2, allowing the use of reference tables in IEC
60584-1 or, alternatively, calibrated in a manner traceable to the International temperature scale ITS-90. The tip of the
thermocouple shall be close to but not touching the test piece. It shall previously have been determined that the
temperature of the test piece shall not vary by more than ± 5 °C over its length after a 15 minute hold time at the
required testing temperature.
NOTE 2 For use in an air atmosphere, the furnace can most conveniently be of a split design allowing access to the test jig
in the position for testing. For a controlled atmosphere, a similar arrangement may be used with the test jig surrounded by a
gas-tight work-tube, or alternatively, a sealed atmosphere furnace may be employed. The flow con
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