prEN 843-3

• Abstract:

  This document 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 flexural strength on the rate of loading.; The method is based on strength test procedures described in EN 843 1.; The applicability of this method is limited by specific requirements for a low scatter of the initial strength of the test pieces and an upper limit of the stress load rate for the data points considered.; This document is not applicable to test pieces with artificially introduced flaws or cracks.

• Status: Not Published
• Publication Date: 07-Sep-2027
• ICS: 81.060.30 - Advanced ceramics
• Technical Committee: CEN/TC 184 - Advanced technical ceramics
• Drafting Committee: CEN/TC 184/WG 3 - Monolithic ceramics
• Current Stage: 4060 - Closure of enquiry - Enquiry
• Start Date: 03-Sep-2026
• Due Date: 18-Nov-2025
• Completion Date: 03-Sep-2026
• Ref Project: oSIST prEN 843-3:2026 - 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

• Revises: EN 843-3:2005 - 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
• Effective Date: 18-Mar-2024

prEN 843-3 is a CEN draft European Standard for advanced technical ceramics. It specifies a room-temperature test method for determining subcritical crack growth parameters of monolithic ceramics from how mean flexural strength changes with loading rate in the temperature range 15 °C to 30 °C. The method is intended for laboratories and ceramic specialists who need to compare materials under controlled test conditions.

What does prEN 843-3 specify?

prEN 843-3 specifies a method for determining subcritical crack growth parameters of advanced monolithic technical ceramics by constant stressing rate flexural strength tests. The method is based on EN 843-1 and is limited by the need for low scatter in initial strength and an upper limit on the stress load rate used for data points.

prEN 843-3 applies only to test pieces without artificially introduced flaws or cracks. The document is organized into scope, normative references, terms and definitions, significance and use, apparatus, test pieces, test procedure, calculation, precision and interferences, test report, and an informative annex.

Annex	What it covers
Annex A	Derivation of the relationship used to determine subcritical crack growth parameters from constant stressing rate flexural strength tests

What are the key requirements of prEN 843-3?

The core of prEN 843-3 is to measure flexural strength at several loading rates, plot strength against stressing rate on log-log scales, and extract the subcritical crack growth parameters from the line fit. In practice, that means the test programme must control the loading rate, the environment, and the test piece quality closely enough that the trend can be interpreted reliably.

Test conditions and scope limits

Clause 1 restricts the method to 15 °C to 30 °C and excludes test pieces with artificial flaws or cracks. Clause 4 adds that the method characterizes susceptibility to subcritical crack growth, but use of the parameters for design and lifetime estimation is outside the document. For the reader, that means the test is for material comparison and characterization, not a design rule.

Apparatus and measurement control

Clause 5 requires an EN 843-1 test jig, either three-point or four-point flexure, with defined spans, controlled roller alignment, and environmental containment when testing outside ambient air. The test machine must cover a wide range of constant rates and meet EN ISO 7500-1 Grade 1 accuracy. This matters because the result depends on the actual stressing rate at failure, not just the nominal machine setting.

Test pieces and preparation

Clause 6 requires test pieces prepared to EN 843-1 and assigned one of four surface finish categories: I, II, III.1 or III.2. Dimensions, chamfering, and tolerances are prescribed, and at least 50 test pieces are needed, with 10 at each of five stressing rates. In practice, this ensures enough data to estimate the slope of the strength-rate relationship.

Test procedure

Clause 7 requires width and thickness measurements at several positions, verification of jig spans, control of temperature and humidity, and recording of peak force and force-displacement behavior. The ambient temperature must stay between 15 °C and 30 °C, and humidity must be recorded where relevant. If as-fired pieces are tested, width and thickness are re-measured at the fracture position for the calculation.

Calculation and data treatment

Clause 8 gives the formulas for nominal flexural strength in three-point and four-point flexure, and for deriving stressing rate from the loading record. The subcritical crack growth parameters are obtained from an unweighted least squares fit of log(fracture stress) versus log(stressing rate). For the reader, this means the result is a fitted parameter set, not a single direct measurement.

Precision and valid data

Clause 9 warns that uncertainty can be large, especially because the parameter n is often high and the stressing-rate range must be wide. Annex A adds a criterion for deciding whether a data point shows significant crack growth; if fewer than 90 % of points meet it, the derived values for B and n are only approximate. This is important when judging whether the test series is strong enough for comparison work.

What terms does prEN 843-3 define?

• Nominal flexural strength - the maximum nominal stress at failure in linear elastic bending.
• Three-point flexure - bending with support near the ends and a central load.
• Four-point flexure - bending with support near the ends and two equal loads placed symmetrically about the center.
• Subcritical crack growth - crack extension under stress that does not cause immediate failure.
• Subcritical crack growth parameters - parameters that describe the relation between crack velocity and stress intensity factor.
• Flexural strength - the strength value derived from failure in bending, used here as the measured response to different stressing rates.
• Stressing rate - the applied loading rate used to generate the strength-rate relationship.

Who uses prEN 843-3?

prEN 843-3 is used by testing laboratories, ceramic manufacturers, research groups, and quality teams working with advanced monolithic technical ceramics. They use it to compare materials, assess sensitivity to environment-dependent slow crack growth, and document flexural strength behavior under controlled loading rates. It also supports work where the test report must align with EN ISO/IEC 17025.

What changed in prEN 843-3 from the previous edition?

prEN 843-3 supersedes EN 843-3:2005. The European foreword states these changes: the scope was updated to clarify limits of the underlying mathematical-physical evaluation method, the normative references were updated, Annex A was updated with a criterion for valid data points, and the document was editorially revised.

Which standards are used with prEN 843-3?

• EN 843-1 - provides the flexural strength test procedures on which this method is based.
• EN ISO 3611 - specifies the micrometers used for dimensional measurement of test pieces.
• EN ISO 7500-1 - provides calibration and verification requirements for the force-measuring system of the test machine.
• EN ISO/IEC 17025 - sets the competence and reporting framework for testing and calibration laboratories.

What does the prEN 843-3 document contain?

prEN 843-3 contains the apparatus requirements, specimen preparation rules, test procedure, calculation method, precision discussion, and test report content. It also includes a table of test piece dimensions, equations for nominal flexural strength and stressing-rate evaluation, and a schematic log-log plot used to extract the slope and intercept. Annex A gives the derivation behind the method and the condition used to judge whether a data point reflects significant crack growth.

SLOVENSKI STANDARD
01-september-2026
Sodobna tehnična keramika - Monolitna keramika - Mehanske lastnosti pri sobni
temperaturi - 3. del: Ugotavljanje parametrov rasti podkritičnih razpok na podlagi
preskusov upogibne trdnosti s konstantno hitrostjo obremenjevanja
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 à température ambiante - Partie 3: Détermination des paramètres de
propagation sous-critique des fissures à partir des essais de résistance à la flexion
réalisés à vitesse de contrainte constante
Ta slovenski standard je istoveten z: prEN 843-3
ICS:
81.060.30 Sodobna keramika Advanced ceramics
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

DRAFT
EUROPEAN STANDARD
NORME EUROPÉENNE
EUROPÄISCHE NORM
June 2026
ICS 81.060.30 Will supersede EN 843-3:2005
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 Hochleistungskeramik - Mechanische Eigenschaften
mécaniques des céramiques monolithiques à monolithischer Keramik bei Raumtemperatur - Teil 3:
température ambiante - Partie 3: Détermination des Bestimmung der Parameter des unterkritischen
paramètres de propagation sous-critique des fissures à Risswachstums aus Biegefestigkeitsprüfungen mit
partir des essais de résistance à la flexion réalisés à konstanter Spannungsrate
vitesse de contrainte constante
This draft European Standard is submitted to CEN members for enquiry. It has been drawn up by the Technical Committee
CEN/TC 184.
If this draft becomes a European Standard, 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.

This draft European Standard was established by CEN 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-CENELEC
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, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Türkiye and
United Kingdom.
Recipients of this draft are invited to submit, with their comments, notification of any relevant patent rights of which they are
aware and to provide supporting documentation.

Warning : This document is not a European Standard. It is distributed for review and comments. It is subject to change without
notice and shall not be referred to as a European Standard.

EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2026 CEN All rights of exploitation in any form and by any means reserved Ref. No. prEN 843-3:2026 E
worldwide for CEN national Members.

Contents Page
European foreword . 3
1 Scope . 4
2 Normative references . 4
3 Terms and definitions . 4
4 Significance and use . 5
5 Test apparatus . 6
6 Test pieces . 7
7 Test procedure . 8
8 Calculation . 9
9 Precision and interferences . 10
10 Test report . 11
Annex A (informative) Derivation of relationship for determination of subcritical crack
growth parameters from constant stressing rate flexural strength tests . 13
Bibliography . 15

European foreword
This document (prEN 843-3:2026) has been prepared by Technical Committee CEN/TC 184 “Advanced
technical ceramics”, the secretariat of which is held by DIN.
This document is currently submitted to the CEN Enquiry.
This document will supersede EN 843-3:2005.
a) the scope has been updated to include a clarification on the limitations of the underlying
mathematical-physical evaluation method;
b) the normative references have been updated;
c) Annex A has been updated to include a criteria for valid data points;
d) the document has been editorially revised.
A list of all parts in the EN 843 series, published under the general title Advanced technical ceramics —
Mechanical properties of monolithic ceramics at room temperature, can be found on the CEN website.
1 Scope
This document 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 flexural strength on the rate of loading.
The method is based on strength test procedures described in EN 843-1.
The applicability of this method is limited by specific requirements for a low scatter of the initial strength
of the test pieces and an upper limit of the stress load rate for the data points considered.
This document is not applicable to test pieces with artificially introduced flaws or cracks.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements 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 3611, Geometrical product specifications (GPS) - Dimensional measuring equipment - Design and
metrological characteristics of micrometers for external measurements (ISO 3611:2023)
EN ISO 7500-1, Metallic materials - Calibration and verification of static uniaxial testing machines - Part 1:
Tension/compression testing machines - Calibration and verification of the force-measuring system
(ISO 7500-1)
EN ISO/IEC 17025, General requirements for the competence of testing and calibration laboratories
(ISO/IEC 17025)
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:

— ISO Online browsing platform: available at https://www.iso.org/obp/
— IEC Electropedia: available at https://www.electropedia.org/
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 test piece 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
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 can 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 can be found in [1].
The determination of subcritical crack growth parameters in accordance with this document allows the
characterization 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 can be given by:
n

K
I
vA= (1)

K
Ic
where
v is the velocity of the growing crack in metres per second;
A is a constant in metres per second;
K is the critical stress intensity factor developed at the crack tip by the applied stress in
I
1/2
Megapascals metres ;
K is critical stress intensity factor at the crack tip required to cause instantaneous crack
Ic
propagation.
NOTE 3 There are other algebraic representations of this relationship which are less convenient mathematically
but can 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 Formula (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 recognized that Formula (1)
implies a single simple relationship, but in practice it is possible that there are nonlinearities. There are
thought to be two principal causes of nonlinearity:
a) At low stress intensity factors it is possible that there is no subcritical crack growth. This is termed
the subcritical crack growth threshold, or “fatigue limit”.
b) At intermediate stress intensity factors, it is possible that the crack growth rate is limited by the rate
at which the environment can penetrate along the crack to control fracture at the tip. This results in
a 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
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 Formula (1) and the effect of stressing rate on strength is derived, yielding
the basic formula:

logσσlogB+ log (2)
f 0
n+1
where
B is a constant;
σ is the fracture strength of a test-piece in MPa;
f

σ is the stressing rate employed in MPa per second.
NOTE 5 Formula (2) 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 Weibull distribution.
f
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 can be used only to determine 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
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 can 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 Test apparatus
5.1 Test jig, in accordance with 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 shall be either
(20 ± 0,5) mm (span A) or (40 ± 0,5) mm (span B), and the loading shall be in either three-point flexure
or four-point flexure. In four-point flexure, the central loading span shall be either (10 ± 0,2) mm for span
A or (20 ± 0,2) mm for span B and shall be symmetrically positioned 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 (5.5) to the nearest 0,1 mm along the length of the test piece using a travelling
microscope or similar device (5.4).
The material from which the test 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 by increased friction.
For testing in water, it is recommended that the test jig be constructed from a material in accordance with
EN 843-1 that is stable against corrosion.
5.2 Environmental control facility. 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 testing in water, a simple water tank shall suffice. For controlled humidity or gaseous
environments, an environmental chamber and control system is required. For corrosive chemical
solutions, appropriate safety precautions shall be adopted for handling and containment.
NOTE Appropriate safety precautions can be found, e.g. in national or local regulations.
5.3 Test machine. The test jig (5.1) and environmental control facility (5.2) shall be assembled in a
suitable mechanical test machine that is 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 range of constant rates covering at least four orders of
-1 -1
magnitude within the range 100 N s and 0,005 N s .
If the available test machine does not offer pre-selected loading rates (load control), it is permissible to
employ cross-head displacement rate control. The actual test piece stressing rate is determined from the
tangent of the force/time record at the time of failure.
The test machine shall be equipped for recording the peak force applied to the
...