SIST EN 843-3:2005
(Main)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
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
This European Standard specifies a method for the determination of subcritical crack growth parameters of advanced monolithic technical ceramics in the temperature range 15 °C to 30 °C by measuring the dependence of mean fracture strength on the rate of loading. The method is based on strength test procedures described in EN 843-1. This European Standard is not applicable to test pieces with artificially introduced flaws or cracks.
Hochleistungskeramik - Mechanische Eigenschaften monolithischer Keramik bei Raumtemperatur - Teil 3: Bestimmung der Parameter des unterkritischen Risswachstums aus Biegefestigkeitsprüfungen mit konstanter Spannungsrate
Diese Europäische Norm legt ein Verfahren zur Bestimmung von Parametern des unterkritischen
Risswachstums für monolithische keramische Hochleistungswerkstoffe im Temperaturbereich von 15 °C bis
30 °C durch Messung der Abhängigkeit der mittleren Bruchfestigkeit von der Beanspruchungsrate fest. Dieses
Verfahren basiert auf den Festigkeitsprüfverfahren, die in EN 843-1 festgelegt sind. Diese Europäische Norm
gilt nicht für Probekörper mit künstlich eingebrachten Defekten oder Rissen.
Céramiques techniques avancées - Propriétés mécaniques des céramiques monolithiques a température ambiante - Partie 3: Détermination des parametres de propagation sous-critique des fissures a partir des essais de résistance a la flexion réalisés a vitesse de contrainte constante
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
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Standards Content (Sample)
SLOVENSKI STANDARD
SIST EN 843-3:2005
01-november-2005
1DGRPHãþD
SIST ENV 843-3:2000
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
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
Hochleistungskeramik - Mechanische Eigenschaften monolithischer Keramik bei
Raumtemperatur - Teil 3: Bestimmung der Parameter des unterkritischen
Risswachstums aus Biegefestigkeitsprüfungen mit konstanter Spannungsrate
Céramiques techniques avancées - Propriétés mécaniques des céramiques
monolithiques a température ambiante - Partie 3: Détermination des parametres de
propagation sous-critique des fissures a partir des essais de résistance a la flexion
réalisés a vitesse de contrainte constante
Ta slovenski standard je istoveten z: EN 843-3:2005
ICS:
81.060.30 Sodobna keramika Advanced ceramics
SIST EN 843-3:2005 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
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SIST EN 843-3:2005
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SIST EN 843-3:2005
EUROPEAN STANDARD EN 843-3
NORME EUROPÉENNE
EUROPÄISCHE NORM
June 2005
ICS 81.060.30 Supersedes ENV 843-3:1996
English version
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
Céramiques techniques avancées - Propriétés mécaniques Hochleistungskeramik - Mechanische Eigenschaften
des céramiques monolithiques à température ambiante - monolithischer Keramik bei Raumtemperatur - Teil 3:
Partie 3: Détermination des paramètres de propagation Bestimmung der Parameter des unterkritischen
sous-critique des fissures à partir des essais de résistance Risswachstums aus Biegefestigkeitsprüfungen mit
à la flexion réalisés à vitesse de contrainte constante konstanter Spannungsrate
This European Standard was approved by CEN on 14 April 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 843-3:2005: E
worldwide for CEN national Members.
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SIST EN 843-3:2005
EN 843-3:2005 (E)
Contents Page
Foreword. 3
1 Scope. 4
2 Normative references. 4
3 Terms and definitions . 4
4 Significance and use. 5
5 Apparatus. 6
5.1 Test jig. 6
5.2 Environmental control. 7
5.3 Test machine. 7
5.4 Linear measuring devices. 7
5.5 Drying oven. 7
5.6 Humidity measuring device . 8
6 Test pieces. 8
7 Test procedure. 8
8 Calculation . 9
9 Precision and interferences. 10
10 Report. 11
Annex A (informative) Derivation of relationship for determination of subcritical crack
growth parameters from constant stressing rate flexural strength tests . 13
Bibliography . 14
2
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SIST EN 843-3:2005
EN 843-3:2005 (E)
Foreword
This document (EN 843-3:2005) 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 2005, and conflicting national standards
shall be withdrawn at the latest by December 2005.
EN 843 ‘Advanced technical ceramics – Mechanical properties of monolithic ceramics at room
temperature’ consists of 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: Guide for fractographic examination.
This document supersedes ENV843-3:1996.
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.
3
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SIST EN 843-3:2005
EN 843-3:2005 (E)
1 Scope
This European Standard specifies a method for the determination of subcritical crack growth parameters
of advanced monolithic technical ceramics in the temperature range 15 °C to 30 °C by measuring the
dependence of mean fracture strength on the rate of loading. The method is based on strength test
procedures described in EN 843-1. This European Standard is not applicable to test pieces with artificially
introduced flaws or cracks.
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 — Mechanical properties of monolithic ceramics at room
temperature — Part 1: Determination of flexural strength
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 17025:1999)
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 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 linear elastic
bending
3.2
three-point flexure
means of bending a beam test piece whereby the testpiece is supported on bearings near its ends and a
central load 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
equally loaded at two positions symmetrically disposed about the centre of the supported span
3.4
subcritical crack growth
extension of existing cracks or flaws under a stress which does not produce instant failure
4
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SIST EN 843-3:2005
EN 843-3:2005 (E)
3.5
subcritical crack growth parameters
parameters describing the relationship between crack velocity and stress intensity factor
4 Significance and use
Subcritical crack growth can occur in brittle solids at stress levels below that required to cause
instantaneous failure. This effect may be caused by the testing environment, or by the intrinsic crack
propagation behaviour of the material. The phenomenon leads to a decay of remaining strength in a
manner determined by the loading history of the component or test piece.
NOTE 1 A review of subcritical crack growth may be found in [1].
The determination of subcritical crack growth parameters in accordance with this document allows the
characterisation of the susceptibility of the material to subcritical crack growth, and thus its ability to
support continued mechanical loading. Using these parameters it is possible to compare materials for
susceptibility to loss of strength under load in particular environments, and to estimate the lifetime of a
component used under similar loading and environmental conditions.
NOTE 2 The use of these parameters in design and lifetime estimation is not within the scope of this
document.
The relationship between the stress intensity factor at the tip of a crack or flaw and the velocity of the
subcritically growing crack may be given by:
n
K
I
v= A (1)
0
K
Ic
where
v is the velocity of the growing crack in metres per second;
A is a constant in metres per second;
0
K is the critical stress intensity factor developed at the crack tip by the applied stress in
I
1/2
Megapascals metres ;
K = critical stress intensity factor at the crack tip required to cause instantaneous crack propagatio.
Ic
NOTE 3 There are other algebraic representations of this relationship which are less convenient
mathematically, but may be physically more realistic in practice. See, e.g. [2] and [3]. [2] considers that
practical data cannot reliably distinguish between various relationships. The mathematical analysis in this
document therefore does not cover such alternative relationships.
In Equation (1), the value of n at room temperature is normally high, typically in the range fifteen to
several hundred. At the lower end of this range, materials are very susceptible to subcritical crack growth,
while at the upper end the phenomenon becomes insignificant. It should be recognised that Equation (1)
implies a single simple relationship, but in practice there may be non-linearities. There are thought to be
two principal causes of non-linearity:
a) At low stress intensity factors there may be no subcritical crack growth. This is termed the
subcritical crack growth threshold, or "fatigue limit".
b) At intermediate stress intensity factors, the crack growth rate may be limited by the rate at which
the environment can penetrate along the crack to control fracture at the tip. This results in a
5
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EN 843-3:2005 (E)
plateau effect, which is maintained to K levels at which crack growth can occur in the absence of
I
an environmental effect.
It should be noted that n and A are often functions of the environmental conditions employed. In
0
particular, many ceramics show marked subcritical crack growth in humid air or in water, and much less
marked effects in dry or inert conditions. The test environment shall be defined and controlled for
reproducible results.
In this document, the parameter n and a parameter B , which is related to A , are determined from the
0 0
effect of stressing rate on flexural strength.
NOTE 4 The term "dynamic fatigue" is frequently used to describe such tests, but tends to be
misunderstood. Its use is discouraged.
Annex A shows how the mathematical formulation of the relationship between the subcritical crack
growth parameters based on Equation (1) and the effect of stressing rate on strength is derived, yielding
the basic formula:
1
logσ = logB + logσ& (2)
f 0
n+1
where
σ is the nominal fracture strength of a test-piece in MPa;
f
B is the constant;
0
&
σ is the stressing rate employed in MPa per second.
NOTE 5 This equation is strictly correct only if a consistent failure probability at each loading rate is
employed, e.g. P = 0,5, which is calculable from a test piece population of ≥ 30 via, for example, fitting a
f
Weibull distribution. If a smaller number of tests is used, as in this test method, the potential uncertainty is
likely to be greater.
NOTE 6 This test method may be used only to measure B . Calculation of A requires knowledge of other
0 0
material parameters not determined by this test method.
The subcritical crack growth parameters are determined by employing several different stressing rates,
&
plotting a graph of log σ versus log σ , and calculating the slope (1/(n+1)) and the intercept (log B ).
f 0
NOTE 7 If the test material is to be exposed to an environment in which severely corrosive processes are
likely to occur, loss of strength with increasing exposure time may override true subcritical crack growth
behaviour. If such an eventuality is suspected, it is recommended that a test is performed in which additional
test pieces are exposed to the corrosive environment without stressing for a duration similar to that required
for the slowest testing anticipated in the test series, and are subsequently strength tested to compare
residual short-term strength with short-term strength before corrosion.
5 Apparatus
5.1 Test jig
The test jig shall be in accordance with the provisions described in EN 843-1, with the force being applied
to the test piece through parallel self-aligning freely rotating loading rollers of adequate hardness. The
test jig span may be either 20 mm ± 0,5 mm (span A) or 40 mm ± 0,5 mm (span B), and the loading may
be in either three-point flexure or four-point flexure. In four-point flexure, the central loading span may be
either 10 mm ± 0,2 mm for span A or 20 mm ± 0,2 mm for span B, and shall be symmetrically positioned
6
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EN 843-3:2005 (E)
to within 0,1 mm with respect to the outer support span. The spans and distances between load and
support rollers shall be measured with a travelling microscope to the nearest 0,1 mm along the length of
the test-piece using a travelling microscope or similar device (5.4.2).
The material from which the jig is constructed shall be compatible with the environment to be used for the
tests, and shall not corrode in such a way as to impair its self-aligning and friction-free capability.
NOTE For tests in water, it is recommended that the test jig be constructed from stainless steel that does
not suffer badly from crevice corrosion, e.g. 316 grade. The rollers may conveniently be machined from hard
ceramics such as alumina, dense silicon nitride or silicon carbide.
5.2 Environmental control
If the tests are to be performed in any environment other than ambient air, an appropriate containment
facility shall be constructed to allow the test conditions to be controlled. For tests in water, a simple water
tank shall suffice. For controlled hum
...
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