SIST EN 843-8:2010

SLOVENSKI STANDARD
SIST EN 843-8:2010
01-september-2010
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Advanced technical ceramics - Mechanical properties of monolithic ceramics at room
temperature - Part 8: Guidelines for conducting proof tests
Hochleistungskeramik - Mechanische Eigenschaften monolithischer Keramik bei
Raumtemperatur - Teil 8: Leitlinien zur Durchführung von Prüfungen der
Gebrauchsfähigkeit
Céramiques techniques avancées - Propriétés mécaniques des céramiques
monolithiques à température ambiante - Partie 8: Lignes directrices de conduite
d'épreuves
Ta slovenski standard je istoveten z: EN 843-8:2010
ICS:
81.060.30 Sodobna keramika Advanced ceramics
SIST EN 843-8:2010 en,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST EN 843-8:2010

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SIST EN 843-8:2010


EUROPEAN STANDARD
EN 843-8

NORME EUROPÉENNE

EUROPÄISCHE NORM
June 2010
ICS 81.060.30
English Version
Advanced technical ceramics - Mechanical properties of
monolithic ceramics at room temperature - Part 8: Guidelines for
conducting proof tests
Céramiques techniques avancées - Propriétés mécaniques Hochleistungskeramik - Mechanische Eigenschaften
des céramiques monolithiques à température ambiante - monolithischer Keramik bei Raumtemperatur - Teil 8:
Partie 8: Lignes directrices de conduite d'épreuves Leitlinien zur Durchführung von Überlast-Prüfungen
This European Standard was approved by CEN on 13 May 2010.

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 CEN 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 CEN Management Centre has the same status as the
official versions.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, 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: Avenue Marnix 17, B-1000 Brussels
© 2010 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN 843-8:2010: E
worldwide for CEN national Members.

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SIST EN 843-8:2010
EN 843-8:2010 (E)
Contents Page
Foreword .3
1 Scope .4
2 Normative references .4
3 Terms and definitions .4
4 Principle .5
5 Main considerations .5
6 Design of proof-test equipment .6
7 Test operation .7
8 Report .7
Annex A (informative) Basis of proof-testing .9
A.1 Short-term strength .9
A.2 Long-term effects.9
A.3 Defining the need to proof-test . 10
Bibliography . 11

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SIST EN 843-8:2010
EN 843-8:2010 (E)
Foreword
This document (EN 843-8:2010) 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 December 2010, and conflicting national standards shall be withdrawn
at the latest by December 2010.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. CEN [and/or CENELEC] shall not be held responsible for identifying any or all such patent rights.
EN 843, Advanced technical ceramics ― Mechanical properties of monolithic ceramics at room temperature,
consists of the following nine 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
 Part 7: C-ring tests
 Part 8: Guidelines for conducting proof tests
 FprCEN/TS 843-9, Advanced technical ceramics ― Mechanical properties of monolithic ceramics at room
temperature ― Part 9: Method of test for edge-chip resistance
According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following
countries are bound to implement this European Standard: Austria, Belgium, Bulgaria, Croatia, 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 the United Kingdom.
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SIST EN 843-8:2010
EN 843-8:2010 (E)
1 Scope
This European Standard describes requirements and methods for proof testing of advanced technical ceramic
components. It provides general guidance concerning the design of the test and the methodology for the selection
of loading conditions.
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 843-3, Advanced technical ceramics ― Mechanical properties of monolithic ceramics at room
temperature ― Part 3: Determination of subcritical crack growth parameters from constant stressing rate
flexural strength tests
EN 843-5, Advanced technical ceramics ― Mechanical properties of monolithic ceramics at room
temperature ― Part 5: Statistical analysis
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/IEC 17025, General requirements for the competence of testing and calibration laboratories
(ISO/IEC 17025:2005)
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
delayed failure
fracture of an item after an extended period under stress
3.2
item under test
component to be subjected to the proof test
3.3
proof test
short-term test designed to investigate the mechanical or thermo-mechanical potential of a component,
removing by fracture those components which do not meet specified levels
3.4
proof-test ratio
ratio of the stress to be applied in a short-term proof test to the expected long-term service stress within an
item under test
NOTE "Item under test", see 3.2.
3.5
sub-critical crack growth
extension of existing cracks or flaws under a stress which does not produce instant failure
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SIST EN 843-8:2010
EN 843-8:2010 (E)
4 Principle
Since advanced technical ceramic components can contain microstructural inhomogeneities and mechanical
damage which are difficult to detect by non-destructive observations (dye tests, ultrasonics, etc.), an individual
component can have insufficient strength to perform adequately in a particular application. The objective of
mechanical or thermo-mechanical proof testing is to determine whether an individual item has adequate
mechanical properties before being placed into service. The principle is to apply a short-term stressing
operation to the item under test, the level of stress in which exceeds the expected service conditions. Items
which fail in this test, are removed from the population, providing a guarantee of a minimum life in the
survivors. The stressing can be directly mechanical, or as a result of thermal stress, such as in a thermal
shock test.
This guarantee is valid only for the conditions and state of the test piece item under test directly after the proof
test. Any change in the material, the geometry or structure of the item after the proof test (e.g. mechanical,
thermal, oxidative, corrosive, wear or other damage) can change the strength and can shorten the minimum
life of the item.
5 Main considerations
The short-term fracture stress of an advanced technical ceramic component is determined by the most highly
stressed microstructural inhomogeneity or discontinuity, and is therefore determined by the method of
manufacture and surface finishing. In general, it is not possible to predict with any certainty the forces that can
be applied to a component without risking failure. For some applications where premature failure carries with it
considerable costs, it can be beneficial to take steps to minimise the risks by removing from the population of
items those individuals which are most at risk from failure.
Additionally, many types of advanced technical ceramic suffer from the slow growth of small cracks under
maintained stress, with a consequent loss of the remaining strength. This thermally activated process may be
accelerated by the presence of water, or by a corroding environment, which can react with the crystalline or
amorphous bonding at the tip of crack. Thus if a component is held under stress for a prolonged period, it can
weaken with time and lead to delayed failure. The tendency of a material to behave in this way can be
detected, for example, by undertaking strength tests at different stressing rates (see EN 843-3) or by statically
stressing the material until failure occurs. Generally, the effect is most marked in silicate glasses, and in glass-
phase containing oxide ceramic materials. It is less marked in purely crystalline oxide ceramics, and least
marked in non-oxide ceramics.
The principle of the proof-test (see Annex A) is to stress the item to such a level as will probe the item to
determine the presence of features that would result in low strength. The stress distribution should ideally
match that seen in the application of the item, and should be applied smoothly and quickly, and then removed
in a similar manner such that the strength of the surviving items is not reduced by non-catastrophic crack
growth. There are several philosophies that can be adopted:
a) Select a stress level which pragmatically removes a certain fraction of the population, by a few percent,
providing a guaranteed minimum strength for the remainder.
b) Select a stress level which is a factor of typically two or three times the expected stress level in service,
providing a greater assurance that it will survive in service.
c) Numerically determine the over-stress level factor from the fracture mechanical behaviour of the material,
specifically the critical stress intensity factor (see CEN/TS 14425-1) and the sub-critical crack growth
characteristics (see EN 843-3), combined with Weibull parameters (see EN 843-5) to provide stress-
volume or stress-area predictions of the risk of failure. This method, while scientifically rigorous, is time-
consuming and effective only if the fracture mechanical data that can be acquired are applicable to the
item in every respect.
NOTE Components may be produced and finished in ways which are not equivalent to the conditions employed for
manufacturing, and testing test pieces of closely defined geometry, and thus may vary in density, mic
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