prEN 820-5

Advanced technical ceramics - Thermomechanical properties of monolithic ceramics - Part 5: Determination of elastic moduli at elevated temperatures

This part of EN 820 describes methods for determining the elastic moduli, specifically Young's modulus, shear modulus and Poisson's ratio, of advanced monolithic technical ceramics at temperatures above room temperature. The standard prescribes three alternative methods for determining some or all of these three parameters:
A   the determination of Young's modulus by static flexure of a thin beam in three- or four-point bending.
B   the determination of Young's modulus by forced longitudinal resonance, or Young's modulus, shear modulus and Poisson's ratio by forced flexural and torsional resonance, of a thin beam.
C   the determination of Young's modulus from the fundamental natural frequency of a struck bar (impulse excitation method).
This part of EN 820 extends the above-defined room-temperature methods described in EN 843-2 to elevated temperatures. All the test methods assume the use of homogeneous test pieces of linear elastic materials. The test assumes that the test piece has isotropic elastic properties. At high porosity levels all of the methods can become inappropriate. The maximum grain size (see EN 623-3), excluding deliberately added whiskers, should be less than 10 % of the minimum dimension of the test piece.
NOTE 1   Method C in EN 843-2 based on ultrasonic time of flight measurement has not been incorporated into this part of EN 820. Although the method is feasible to apply, it is specialised, and outside the capabilities of most laboratories. There are also severe restrictions on test piece geometries and methods of achieving pulse transmission. For these reasons this method has not been included in EN 820-5.
NOTE 2   The upper temperature limit for this test depends on the properties of the test pieces, and can be limited by softening within the timescale of the test. In addition, for method A there can be limits defined by the choice of test jig construction materials.

Hochleistungskeramik - Thermomechanische Eigenschaften monolithischer Keramik - Teil 5: Bestimmung der elastischen Moduln bei erhöhten Temperaturen

Céramiques techniques avancées - Méthodes d'essai des céramiques monolithiques - Propriétés thermomécaniques - Partie 5: Détermination des modules élastiques à températures élevées

Sodobna tehnična keramika - Termomehanske lastnosti monolitske keramike - 5. del: Ugotavljanje elastičnih modulov pri povišanih temperaturah

Ta del standarda EN 820 opisuje metode za določanje elastičnih modulov, natančneje Youngovega modula, strižnega modula in Poissonovega razmerja, naprednih monolitnih tehničnih keramik pri temperaturah nad sobno temperaturo. Standard predpisuje tri alternativne metode za določanje nekaterih ali vseh teh treh parametrov:
A   določanje Youngovega modula z uporabo statičnega upogiba tankega nosilca v tritočkovnem ali štiritočkovnem upogibu.
B   določanje Youngovega modula z uporabo prisilne vzdolžne resonance, ali Youngovega modula, strižnega modula in Poissonovega razmerja z uporabo prisilne upogibne in torzijske resonance tankega nosilca.
C   določanje Youngovega modula iz osnovne naravne frekvence udarjenega droga (metoda vzbujanja z impulzom).
Ta del standarda EN 820 razširja zgoraj opredeljene metode pri sobni temperaturi, opisane v EN 843-2, na povišane temperature. Vse preskusne metode predvidevajo uporabo homogenih preskusnih kosov iz linearno elastičnih materialov. Preskus predvideva, da ima preskusni kos izotropne elastične lastnosti. Pri visokih ravneh poroznosti lahko vse metode postanejo neprimerne. Največja velikost zrn (glej EN 623-3), brez namerno dodanih vlaken (whiskers), mora biti manjša od 10 % najmanjše dimenzije preskusnega kosa.
OPOMBA 1   Metoda C v EN 843-2, ki temelji na ultrazvočnem merjenju časa preleta, ni bila vključena v ta del standarda EN 820. Čeprav je metoda izvedljiva, je specializirana in presega zmogljivosti večine laboratorijev. Obstajajo tudi resne omejitve glede geometrij preskusnih kosov in metod za doseganje prenosa impulza. Zaradi teh razlogov ta metoda ni bila vključena v EN 820-5.
OPOMBA 2   Zgornja temperaturna meja za ta preskus je odvisna od lastnosti preskusnih kosov in je lahko omejena z mehčanjem v časovnem okviru preskusa. Poleg tega lahko za metodo A obstajajo omejitve, določene z izbiro materialov za konstrukcijo preskusnega pripomočka.

General Information

• Status: Not Published
• Publication Date: 26-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: 4020 - Submission to enquiry - Enquiry
• Start Date: 21-May-2026
• Due Date: 11-May-2026
• Completion Date: 21-May-2026
• Ref Project: oSIST prEN 820-5:2026 - Advanced technical ceramics - Thermomechanical properties of monolithic ceramics - Part 5: Determination of elastic moduli at elevated temperatures

Relations

• Revises: EN 820-5:2009 - Advanced technical ceramics - Thermomechanical properties of monolithic ceramics - Part 5: Determination of elastic moduli at elevated temperatures
• Effective Date: 18-Jun-2025

Overview

prEN 820-5: Advanced technical ceramics - Thermomechanical properties of monolithic ceramics - Part 5: Determination of elastic moduli at elevated temperatures sets out standardized methods for measuring the elastic properties of advanced monolithic technical ceramics beyond room temperature. Developed by CEN (European Committee for Standardization), this standard is crucial for industries that rely on accurate characterization of ceramics used in high-temperature environments. It provides details on methods for the determination of Young’s modulus, shear modulus, and Poisson’s ratio using procedures adapted specifically for operation at elevated temperatures.

Key Topics

• High-Temperature Elastic Properties: This standard focuses on how to accurately measure elastic moduli - including Young's modulus, shear modulus, and Poisson’s ratio - for advanced technical ceramics when exposed to temperatures above ambient conditions.
• Test Methods: Three principal methods are prescribed:
  • Method A: Determination of Young’s modulus through static flexure (three- or four-point bending).
  • Method B: Determination by forced resonance (longitudinal, flexural, and torsional) to obtain Young's modulus, shear modulus, and Poisson’s ratio.
  • Method C: Impulse excitation method to determine Young’s modulus using the natural frequency of a struck bar.
• Sample and Measurement Conditions: Assumes homogeneous, isotropic, and linear elastic test pieces. Test piece preparation, grain size limits, and considerations for high-porosity ceramics are detailed to ensure validity of results.
• Temperature Considerations: The upper test temperature limit is dictated by material properties and the resilience of test setup materials, making careful temperature control and monitoring critical.

Applications

The methodologies outlined in prEN 820-5 serve several high-value applications:

• Quality Control: Ensuring the reliability and consistency of advanced ceramics used in high-stress, high-temperature environments such as aerospace, automotive, electronics, and energy sectors.
• Material R&D: Supporting research and development by equipping labs with reliable procedures to characterize new ceramic compositions or treatments under realistic service conditions.
• Engineering Design: Supplying critical mechanical data needed for finite element modeling and simulation of structural ceramic components at elevated temperatures.
• Performance Assessment: Facilitating the comparison and selection of materials based on well-defined and reproducible measurements of mechanical properties under operating conditions.

Related Standards

For practitioners implementing prEN 820-5, the following standards provide complementary procedures and definitions:

• EN 820-1: Methods for testing flexural strength of ceramics at elevated temperatures.
• EN 843-1 / EN 843-2: Procedures for determining mechanical properties of monolithic ceramics at room temperature.
• EN 60584-1: Specifications for thermocouples, ensuring accurate temperature measurement during testing.
• EN ISO 13383-1: Microstructural characterization of advanced ceramics, specifying grain size measurement.
• EN ISO 463, EN ISO 3611, EN ISO 7500-1, EN ISO 13385-1: Standards covering dimensional measurement tools and calibration of testing machines.

Practical Value

The adoption of prEN 820-5 enables laboratories and manufacturing sites to perform internationally recognized tests for the thermomechanical properties of ceramics, supporting product development, certification, and market acceptance. By standardizing the measurement of elastic moduli at high temperatures, this document helps ensure consistency, comparability, and repeatability of results across Europe and internationally. This, in turn, reduces technical barriers to trade and supports innovation in the field of advanced ceramics for demanding applications.

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Keywords: advanced technical ceramics, elastic modulus, Young’s modulus, shear modulus, Poisson’s ratio, thermomechanical testing, elevated temperature, monolithic ceramics, CEN standard, material characterization, prEN 820-5, resonance method, impulse excitation, static flexure, ceramic testing.

Standards Content (Sample)

SLOVENSKI STANDARD
01-julij-2026
Sodobna tehnična keramika - Termomehanske lastnosti monolitske keramike - 5.
del: Ugotavljanje elastičnih modulov pri povišanih temperaturah
Advanced technical ceramics - Thermomechanical properties of monolithic ceramics -
Part 5: Determination of elastic moduli at elevated temperatures
Hochleistungskeramik - Thermomechanische Eigenschaften monolithischer Keramik -
Teil 5: Bestimmung der elastischen Moduln bei erhöhten Temperaturen
Céramiques techniques avancées - Méthodes d'essai des céramiques monolithiques -
Propriétés thermomécaniques - Partie 5: Détermination des modules élastiques à
températures élevées
Ta slovenski standard je istoveten z: prEN 820-5
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
May 2026
ICS 81.060.30 Will supersede EN 820-5:2009
English Version
Advanced technical ceramics - Thermomechanical
properties of monolithic ceramics - Part 5: Determination
of elastic moduli at elevated temperatures
Céramiques techniques avancées - Méthodes d'essai Hochleistungskeramik - Thermomechanische
des céramiques monolithiques - Propriétés Eigenschaften monolithischer Keramik - Teil 5:
thermomécaniques - Partie 5: Détermination des Bestimmung der elastischen Moduln bei erhöhten
modules élastiques à températures élevées Temperaturen
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 NORMALISATIO N

EUROPÄISCHES KOMITEE FÜR NORMUN G

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 820-5:2026 E
worldwide for CEN national Members.

Contents Page
European foreword . 4
1 Scope . 5
2 Normative references . 5
3 Terms and definitions . 6
4 Method A: Static flexure method . 6
4.1 Principle . 6
4.2 Apparatus . 7
4.3 Preparation of test pieces . 9
4.4 Procedure . 10
4.5 Calculations . 10
4.5.1 From crosshead displacement (Method A.1) . 10
4.5.2 From transducer displacement measurements (Method A.2) . 12
4.6 Accuracy and interferences . 12
5 Method B: Resonance method . 13
5.1 Principle . 13
5.2 Apparatus . 13
5.3 Preparation of test pieces . 16
5.3.1 General. 16
5.3.2 Flexural resonance . 16
5.3.3 Torsional resonance . 16
5.3.4 Longitudinal resonance . 17
5.3.5 Number of test pieces . 17
5.4 Procedure . 17
5.4.1 General. 17
5.4.2 Flexural resonance . 17
5.4.3 Torsional resonance . 18
5.4.4 Longitudinal resonance . 18
5.5 Calculations . 18
5.5.1 Flexural resonance . 18
5.5.2 Torsional resonance . 19
5.5.3 Calculate Poisson's ratio, ν, from the formula: . 19
5.5.4 Longitudinal resonance . 20
5.6 Accuracy and interferences . 20
6 Method C: Impulse excitation method . 21
6.1 Principle . 21
6.2 Apparatus . 21
6.3 Preparation of test pieces . 24
6.4 Procedure . 24
6.5 Calculations . 24
6.6 Accuracy and interferences . 25
7 Report . 25
7.1 General. 25
7.2 Method A . 25
7.3 Method B . 26
7.4 Method C . 26
Annex A (informative) Young’s modulus correction for edge treatments of rectangular cross
section test piece . 27
A.1 General . 27
A.2 Principle . 27
A.3 Procedure . 27
Annex B (informative) Simultaneous determination of Young’s and shear modulus at
elevated temperatures using the impact excitation method . 29
B.1 Principle . 29
B.2 Test-piece . 29
B.3 Test set-up . 29
B.4 Measurement procedure . 29
B.5 Calculations . 30
Bibliography . 31

European foreword
This document (prEN 820-5:2026) 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 820-5:2009.
This document includes the following main significant technical changes with respect to
EN 820-5:2009:
a) update of the normative references;
b) revised Formula (8) and Formula (9) for the calculation of the dynamic shear modulus of a
rectangular prism in the resonance method (Method B) and impulse excitation method (Method C);
c) addition of Formula (10) for the calculation of the dynamic shear modulus of a cylindrical rod in
torsional resonance in 5.5.2.2;
d) addition of a new Annex A addressing the Young’s modulus correction for edge treatments of
rectangular cross section test piece;
e) addition of a new Annex B addressing the simultaneous determination of Young’s and shear modulus
at elevated temperatures using the impact excitation method;
f) editorial revision.
A list of all parts in the EN 820 series, published under the general title Advanced technical ceramics —
Thermomechanical properties of monolithic ceramics, can be found on the CEN website.
1 Scope
This document specifies methods for the determination of the elastic moduli, specifically Young's
modulus, shear modulus and Poisson's ratio, of advanced monolithic technical ceramics at temperatures
above room temperature. The document specifies three alternative methods for determining some or all
of these three parameters:
a) Method A - the determination of Young’s modulus by static flexure of a thin beam in three- or four-
point bending;
b) Method B - the determination of Young's modulus by forced longitudinal resonance, or Young's
modulus, shear modulus and Poisson's ratio by forced flexural and torsional resonance, of a thin
beam;
c) Method C - the determination of Young's modulus from the fundamental natural frequency of a struck
bar (impulse excitation method).
This part of EN 820 extends the above-defined room-temperature methods described in EN 843-2 to
elevated temperatures. All the test methods assume the use of homogeneous test pieces of linear elastic
materials. The test assumes that the test piece has isotropic elastic properties. At high porosity levels all
of the methods can become inappropriate. The maximum grain size measured in accordance with
EN ISO 13383-1, excluding deliberately added whiskers, is less than 10 % of the minimum dimension of
the test piece.
NOTE 1 Method C in EN 843-2 based on ultrasonic time of flight measurement has not been incorporated into
this part of EN 820. Although the method is feasible to apply, it is specialized, and outside the capabilities of most
laboratories. There are also severe restrictions on test piece geometries and methods of achieving pulse
transmission. For these reasons this method has not been included in EN 820-5.
NOTE 2 The upper temperature limit for this test depends on the properties of the test pieces, and can be limited
by softening within the timescale of the test. In addition, for method A there can be limits defined by the choice of
test jig construction materials.
NOTE 3 It is possible that Methods B and Method C are not appropriate for materials with significant levels of
porosity (i.e. > 15 %) which cause damping and an inability to detect resonances or natural frequencies,
respectively.
NOTE 4 This method does not provide for the effects of thermal expansion, i.e. the measurements are based on
room temperature dimensions. Depending upon the use to which the data are put, it can be necessary to make a
further correction by multiplying each dimensional factor in the relevant formulae by a factor (1 + α ΔT) where α
is the mean linear expansion coefficient over the temperature interval ΔT from room temperature.
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 820-1, Advanced technical ceramics - Methods of testing monolithic ceramics - Thermonechanical
properties - Part 1: Determination of flexural strength at elevated temperatures
EN 843-1, Advanced technical ceramics - Mechanical properties of monolithic ceramics at room
temperature - Part 1: Determination of flexural strength
EN 60584-1, Thermocouples - Part 1: EMF specifications and tolerances (IEC 60584-1)
EN ISO 463, Geometrical Product Specifications (GPS) - Dimensional measuring equipment - Design and
metrological characteristics of mechanical dial gauges (ISO 463)
EN ISO 3611, Geometrical product specifications (GPS) - Dimensional measuring equipment - Design and
metrological characteristics of micrometers for external measurements (ISO 3611)
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 13383-1, Fine ceramics (advanced ceramics, advanced technical ceramics) - Microstructural
characterization - Part 1: Determination of grain size and size distribution (ISO 13383-1)
EN ISO 13385-1, Geometrical product specifications (GPS) - Dimensional measuring equipment - Part 1:
Design and metrological characteristics of callipers (ISO 13385-1)
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
Young’s modulus
stress required in a material to produce unit strain in uniaxial extension or compression
3.2
shear modulus
shear stress required in a material to produce unit angular distortion
3.3
Poisson’s ratio
negative value of the ratio of lateral strain to longitudinal strain in an elastic body stressed longitudinally
3.4
static elastic moduli
elastic moduli determined in an isothermal condition by stressing statically or quasi-statically
3.5
dynamic elastic moduli
elastic moduli determined non-quasi-statically, i.e. under quasi-adiabatic conditions, such as in the
resonant or impulse excitation methods
4 Method A: Static flexure method
4.1 Principle
Using three- or four-point bending of a thin beam test piece, the elastic distortion is measured, from which
Young’s modulus can be calculated according to thin-beam formulae.
4.2 Apparatus
4.2.1 Test jig, in accordance with that described in EN 820-1 for flexural strength testing at elevated
temperatures in terms of its function, i.e. the support and loading rollers shall be free to roll, and to
articulate to ensure axial and even loading as described in EN 843-1. The test jig shall be made of
materials which do not interact with the test piece, and which remain essentially elastic at the maximum
test temperature. A typical arrangement is shown in Figure 1.
NOTE 1 Articulation is not essential for carefully machined flat and parallel-faced test pieces.
The outer span of the test jig shall be 40 mm or greater.
NOTE 2 If the displacement is to be measured by Method A.1 (see 4.2.5), a span of up to 100 mm, or a span to
thickness ratio in excess of 20, is recommended to obtain large displacements and to ensure that the compliance of
the machine is a small correction if displacement is recorded as a machine cross-head movement.
The test jig may be either for three-point or four-point flexure. The latter method is required if
displacement is determined by differential transducer.
4.2.2 Test machine, capable of applying a force to the test jig at a constant displacement rate. The test
machine shall be equipped for recording the load applied to the test jig at any point in time. The accuracy
of the test machine shall be in accordance with EN ISO 7500-1, Grade 1 (1 % of indicated load), and shall
be capable of recording to a sensitivity of better than 0,1 % of the maximum load employed. The
calibration shall have been checked within the previous year.
4.2.3 Thermal enclosure and control system, surrounding the test piece, capable of achieving the
maximum desired temperature and maintaining it to ± 2 °C for test temperatures up to 1 000 °C,
and ± 4 °C at higher temperatures.
The system can operate with an air or inert atmosphere, or with a vacuum inside the thermal enclosure.
Especially with regard to use in vacuum, efforts should be made to ensure that the force applied at the
test piece is correctly recorded by the load cell outside the enclosure, taking account of friction or elastic
resistances in seals or bellows systems.
4.2.4 Thermocouple, conforming to EN 60584-1 for measuring the test piece temperature. The
thermocouple shall be in close proximity to but shall not touch the test piece.
4.2.5 Displacement measuring device, for recording the displacement of the loaded test piece by one
of two methods, Method A.1 or Method A.2:
− Method A.1
Recording the apparent displacements of the test machine as the test piece is loaded in the test jig,
and again with the test piece replaced by a ceramic bar at least 15 mm thick with flat and parallel
faces to within 0,05 mm. The difference between these displacements is equivalent to the
displacement of the test piece in the test jig. The displacement recording device (chart recorder,
digital indicator, etc.) shall be calibrated by comparing machine cross-head displacement with the
movement indicated on a dial gauge contacting the cross-head, or other suitable calibrated
displacement measuring device. The dial gauge shall be in accordance with EN ISO 463, or the
alternative device otherwise certified as accurate to 0,01 mm.
The parts of the load train subjected to elevated temperatures shall be made of materials which
remain elastic at the maximum test temperature.
− Method A.2
Recording the displacement of the test piece directly using a transducer extensometer contacting at
least two defined points on the surface of the test piece between the support loading rollers in three-
point or four-point bending. The defined points shall preferably be:
a) for four-point bending: the centre of the span and one or both loading rollers (see for example
Figure 1, right);
b) for three-point bending: the centre of the span and one or both support rollers (see for example
Figure 1, left).
NOTE The formulae given in 4.5 assume these preferred positions. Other displacement detection
positions require alternative formulations.
The transducer shall be capable of detecting movements with an accuracy of 0,001 mm, shall have
output linear to 1 % over the expected displacement range in making this test and its sensitivity shall
be calibrated to an accuracy of 0,1 %.
The extensometer parts subjected to elevated temperatures shall remain elastic to the maximum test
temperature, and their tips shall not interact with the test piece (see also EN 820-1).
4.2.6 Micrometer, in accordance with EN ISO 3611, but capable of recording to 0,002 mm, or other
device of equivalent accuracy, for measuring the dimensions of the test piece.
4.2.7 Dial gauge, in accordance with EN ISO 463 or other calibrated displacement measuring device,
capable of recording to 0,01 mm.
Key
1 ceramic push-rod 8 ceramic support tube
2 ceramic half-sphere 9 ceramic rods detecting deflection
3 ceramic loading block 10 base plate
4 loading rollers (freely rolling) 11 adjusting screw
5 test piece 12 suspension springs
6 support rollers (freely rolling) 13 displacement
7 ceramic support block 14 ceramic support tube
Figure 1 — Typical arrangement for making quasistatic flexural modulus measurement at high
temperatures based on (left) three-point flexure with detection at the centre and (right) four-
point flexure and detection at the centre and opposite the loading rollers
4.3 Preparation of test pieces
Test pieces shall be rectangular section bars selected and prepared by agreement between parties. They
may be directly prepared close to final dimensions or machined from larger blocks. This test measures
Young's modulus parallel to the length of the test piece. If the test material is likely to be elastically
anisotropic, care shall be taken in selection of the test piece orientation and in the interpretation of the
test results. The maximum grain size measured in accordance with EN ISO 13383-1, excluding
deliberately added whiskers, shall be less than 10 % of the minimum dimension of the test piece.
The length of the test pieces shall be at least 10 mm longer than the test-jig span. The width of the test
piece shall be in the range 4 mm to 10 mm. For Method A.1, the thickness of the test piece shall be in the
range 0,8 mm to 1,5 mm. For Method A.2, the test piece may be up to 3 mm thick but preferably should
be in the range 1 mm to 2 mm thick. The test pieces shall be machined to final dimensions. They shall be
flat and parallel-faced to better than ± 0,5 % of thickness on the faces to be placed on the loading rollers
of the test jig. They shall similarly be machined flat and parallel-faced to better than ± 0,5 % of width on
the side faces. For Method A.1 they shall not be chamfered. For Method A.2 they may be chamfered as
specified in EN 843-1.
At least three test pieces shall be prepared.
4.4 Procedure
Measure the width and thickness of the test pieces at least three positions along its length to the nearest
0,002 mm with the micrometer and take the average figure.
Insert a test piece in the test-jig and centralize it in accordance with the requirements of EN 843-1. Select
a maximum force to be applied to the test piece which will avoid fracture.
The upper level of force may be estimated by employing the strength calculation as specified in EN 843-1
and inserting a stress level of no more than 0,5 sf, where sf is the mean fracture stress expected at the
test temperature.
Heat the thermal enclosure to the required test temperature and allow the temperature to stabilize such
that the thermocouple recording test piece temperature varies by no more than 2 °C in a 15 min-period
up to 1 000 °C, and by no more than 4 °C at higher temperatures.
Apply a steadily increasing force to the test jig at a constant test machine cross-head displacement rate
in the range 0,001 mm/min to 0,5 mm/min. Record the load and displacement (either cross-head
displacement, or transducer displacement output) continuously. When the maximum selected force is
achieved, reverse the direction of the machine and reduce the load to zero. Repeat the cycle at least twice
more to the same peak load, or until repeatable results are obtained. Repeat the test on each test piece. If
the machine displacement is to be employed (Method A.1) or if the transducer method is employed using
a support roller as one of the defined points (Method A.2), replace the test piece with the thick parallel-
sided steel (for use to 300 °C) or ceramic bar and repeat the loading cycles to the same peak load,
recording load and displacement.
The use of both loading and unloading cycles is required in order to take into account machine hysteresis
in Method A.1, transducer hysteresis in MethodA.2.
4.5 Calculations
4.5.1 From crosshead displacement (Method A.1)
Inspect the recordings of load and displacement for the test piece and the thick steel or ceramic bar for
uniformity and linearity. Select a region of the recordings from a minimum load of not less than 10 % of
peak load or 0,2 N, whichever is the greater, to a maximum load of not more than 90 % of the peak load
applied. The same load range shall be selected for each loading cycle on the test piece and the thick bar.
The region of the recordings selected should avoid strong nonlinearities at low load which may include
irreproducible effects of machine movement and test piece alignment, and also the effects of cross-head
reversal near peak load.
If the force - displacement traces show evidence of a reduction of stiffness at upper load levels, this can
be taken as evidence of plastic softening. At this temperature and any higher test temperature, the results
of the test should be deemed invalid.
Calculate or measure the displacement recorded over the selected load range for each loading and
unloading cycle for the test piece and for the thick bar. Calculate the average displacement in each
direction. If the displacement of the first cycle is more than 2 % different from that of the second or
subsequent cycle, ignore the first cycle when computing the average.
NOTE 1 It is possible that the first cycle shows a different response to subsequent cycles as the test piece beds
down into the test jig and the machine movement stabilizes.
Calculate Young’s modulus according to Formula (1) and Formula (2):
For displacement of loading points in three-point bending:
F − F l
( )
(1)
E=
4 bh d − d
( )
cs
For displacement of loading points in four-point bending:
23 F −+ Fd d d
( ) ( )
2 1 1 1 2
E= (2)
bh d − d
( )
cs
where
E is the Young’s modulus expressed in pascals (Pa);
F1 is the lower load level selected from recordings, expressed in newtons (N);
F is the upper load level selected from recordings, expressed in newtons (N);
l is the test jig outer span, expressed in metres (m);
d is the test jig inner roller to outer roller spacing in four-point bending, expressed in metres
(m);
d is the one half of the test jig inner span in four-point bending, expressed in metres (m);
b is the test piece width, expressed in metres (m);
h is the test piece thickness, expressed in metres (m);
d is the displacement recorded for the test piece in the jig over the load interval F to F
c 1 2
expressed in metres (m);
ds is the displacement recorded for the thick bar in the jig over the load interval F1 to F2
expressed in metres (m).
NOTE 2 For the case of quarter-point bending, d = d , and Formulae (2) reduces to:
1 2
F − F l
( )
E=
8 bh d − d
( )
cs
Calculate the average Young's modulus figures for the loading and unloading curves. If these values differ
by more than 2 %, repeat the tests. If they differ by less than 2 %, take the overall average as the
determined value from the test.
4.5.2 From transducer displacement measurements (Method A.2)
Use the procedure defined in 4.5.1 to obtain displacements for a defined load range. If one of the defined
points for the transducer contact in three-point bending is the support roller, calculate the displacement
recorded for the thick bar. Subtract the mean value of the thick bar displacement from the mean specimen
displacement over the same load range for both loading and unloading.
If the force-displacement traces show evidence of a reduction of stiffness at upper load levels, this can be
taken as evidence of plastic softening. At this temperature and any higher test temperature, the results of
the test should be deemed invalid.
For three-point bending using defined points at the span centre and under one or both support rollers,
calculate Young’s modulus using Formula (1).
For four-point bending using defined points at the span centre and under one or both loading rollers,
calculate Young’s modulus from Formula (3):
3 F − F dd
( )
2 1 12
E= (3)
bh d
t
where
d is the transducer displacement recorded between the test piece centre and the inner loading
t
point in four-point bending over the selected load range, expressed in metres (m).
NOTE For the case of quarter-point bending, d = d , and Formula (4) reduces to:
1 2
3 F − F l
( )
E=
64 bh d
t
Calculate the average Young's modulus figures for the loading and unloading parts of the cycles. If these
values differ by more than 2 %, repeat the tests. If they differ by less than 2 %, take the overall average
as the determined value from the test.
4.6 Accuracy and interferences
A simple analysis based on the flexure formula can be used to show that the principal sources of error are
in measuring the force range (F – F ), the thickness of the test piece b, and the deflection d or (d - d ). In
2 1 t c s
contrast, measurement of temperature, test span and test piece width play only a minor role. The
following analysis is based on the conditions specified for this method, but the overall error is dependent
on the choice of equipment, the accuracy of calibration, and the repeatability of mechanical contact
between the system and the test piece. Assuming that the accuracy of recording the force is limited
to ± 1 % by the calibration accuracy of the load cell in the test machine, the noise in the output, and any
reading error if a chart recorder is used, the error in (F – F ) is likely to be of the order ± 2 %. The error
2 1
in measuring the thickness of the test piece using a micrometer as specified above is probably ± 0,01 mm,
allowing also for test piece roughness, flatness and parallelism, or typically ± 1 % of the recommended
thickness. The error in measuring the deflection depends not only on the linearity and accuracy of
calibration of the crosshead movement or displacement transducer, but also on the repeatability of
contact of the test piece with the measuring system and the minimization of friction effects. Assuming
that the test is made to a maximum force equivalent to approximately half the fracture force of a test piece
which fails at a strain of 0,1 %, it can be shown that the test piece deflection in three-point bending, d, is
given by:

l
−5

d ≤ 7× 10 (4)

h

For a test span l of 40 mm and a typical value for the recommended thickness for the crosshead
displacement method of 1 mm, d = 0,11 mm. The calibration accuracy for the displacement measurement
shall therefore be 1 % or better for the error in displacement to play a negligible role in the overall errors.
This should be achieved if the conditions on calibration of deflection given in 4.2.5 are upheld. The
repeatability aspects are not readily quantifiable but may be minimized by ensuring repeatability of
recorded displacements in load cycling, and similarity of values in loading and unloading. The overall
error of measurement is thus likely to be typically ± 5 % when the force, thickness and displacement
contributions are appropriately summed. The error can in principle be reduced by (1) lengthening the
test piece span, (2) improving the force calibration over the range used for the test and the recording of
force, (3) employing a higher quality displacement transducer or cross-head movement measuring
device.
Interferences that can arise in undertaking this test include (1) irreversible deformation of the test piece
and/or load train during load cycling, (2) undetected movements of the test piece within the loading and
displacement recording system, (3) oxidation of non-oxide ceramic materials during the course of the
test. In each case the effects tend to increase with increasing test temperature. The influence of these
interferences can be minimized by taking appropriate actions in the design of the test facility, specifically
in the materials used for the parts to be subject to elevated temperatures, the design of the loading jig for
the test piece, and the test atmosphere. Inelastic deformation within the test piece may be detected either
by permanent offsets over a loading cycle, or by a softening with increasing force. Results obtained under
such conditions should be noted in the report and may have little value.
5 Method B: Resonance method
5.1 Principle
A beam test piece is excited mechanically or electromechanically to vibrate at a given frequency, and the
magnitude of the vibration is determined by a detector. The peak response is obtained at the resonant
frequency, either the fundamental or an overtone. The test is performed to excite either longitudinal or
flexural and torsional vibration. Young's modulus may be determined from longitudinal resonance, and
Young's modulus, shear modulus and Poisson's ratio may be determined from the flexural and torsional
resonant frequencies, together with the test piece dimensions and mass.
5.2 Apparatus
5.2.1 General
There are various techniques that may be used to determine the resonant frequency of the test piece as
described in EN 843-2. The preferred technique for flexural and torsional resonance for use at raised
temperatures is to suspend the test piece from two hangers made from a suitable vibration conducting
material, such as thin wires or fibre bundles. One hanger is suspended from a vibration source, and the
other from a detector. In this way, the test piece may be enclosed in a thermal enclosure to permit the
temperature to be raised, while the vibrator and detector remain outside the heated enclosure. For
longitudinal resonance, the test piece needs to be supported centrally and the vibration excited and
detected axially using push rods.
5.2.2 Driving electronics, consisting typically of a variable frequency oscillator and a record player
cartridge assembly, loudspeaker cone, or other suitable transducer. It is recommended that the oscillator
is equipped with a digital frequency display. It shall have sufficient power to drive high-modulus ceramic
test pieces through the transducer in the frequency range 100 Hz to 100 kHz, with a flat response curve
(i.e. no resonances of its own). The stability and accuracy of the digital display shall be checked against a
standard frequency, preferably from a transfer standard source or certified frequency counter.
5.2.3 Detecting electronics, consisting of a record player cartridge assembly or other suitable
transducer, a linear voltage amplifier for the range 100 Hz to 100 kHz, and a voltmeter, ammeter or
oscilloscope. The detector shall generate a voltage proportional to the amplitude of vibration, the velocity,
or the acceleration of the test piece.
The oscilloscope is recommended for identifying resonant conditions.
5.2.4 Test piece support. The test piece support shall permit the test piece to vibrate in the desired
mode and without being restricted by the detecting transducers.
For flexural or torsional vibration, the hanger system recommended in 5.2.1 may be constructed of
appropriate materials which are not expected to interact with the test piece at the maximum test
temperature.
Suitable materials include platinum or tungsten (inert atmospheres only) wire, or ceramic fibres or
filaments, such as aluminosilicate or sapphire.
For the flexural mode, the hangers shall be placed near to but not at the nodal points (at about 0,224 of
the test piece length from each end) of the test piece (see 5.4.1) vibrating in its fundamental mode. The
vibrating mass of the suspension system should be negligible compared with the mass of the test piece.
For the torsional mode, the hangers shall be positioned near the ends of the test piece, but over opposite
sides (see Figure 2b).
For longitudinal vibration, the test piece shall be supported near its centre using a support which does
not interact chemically with the test piece at the maximum test temperature, and which permits free axial
vibration. The pushrods exciting and detecting resonance shall be of materials which do not interact with
the test piece and which remain elastic in character at the maximum test temperature.
5.2.5 Thermal enclosure and control system, surrounding the test piece, capable of achieving the
maximum desired temperature and maintaining it to ± 2 °C for test temperatures up to 1 000 °C,
and ± 4 °C at higher temperatures.
The system can operate with an air or inert atmosphere, or with a vacuum inside the thermal enclosure.
Especially with regard to use in vacuum, efforts should be made to ensure that the applied and recorded
vibrations are adequately transmitted through the enclosure without modification.
Measurements in vacuum may result in larger deviations between the test piece temperature and the
temperature at the control thermocouple. This difference in temperature shall be determined in a
preliminary test. If necessary, a corresponding correction value for the temperature of the control
thermocouple shall be used
5.2.6 Thermocouple, conforming to EN 60584-1 for measuring the test piece temperature. The
thermocouple shall be in close proximity to but shall not touch the test piece.
5.2.7 Laboratory balance, capable of weighing the test piece to the nearest 1 mg.
5.2.8 Micrometer, conforming to EN ISO 3611, but capable of recording to the nearest 0,002 mm or
similar device of equivalent accuracy for measuring the dimensions of the test piece.
5.2.9 Vernier callipers, conforming to EN ISO 13385-1, but capable of recording to the nearest
0,01 mm or similar device of equivalent accuracy for measuring the dimensions of the test piece.
5.2.10 Oven, for drying test pieces at (120 ± 10) °C.
5.2.11 Desiccator, for storage of dried test pieces.

a)
b)
c)
Key
1 driver b width of the test piece
2 detector d diameter of th etest piece
3 nodal positions h thickness of the test piece
L overall length of the test piece
Figure 2 — Flexural (a), torsional (b) and longitudinal (c) resonance test pieces with dimensions
and support, driving and detecting positions indicated
5.3 Preparation of test pieces
5.3.1 General
The test pieces shall be rectangular prisms in accordance with 5.3.2.1, 5.3.3.1 and 5.3.4.1, or circular cross
section rods in accordance with 5.3.2.2, 5.3.3.2 and 5.3.4.2.
The edges of rectangular section test pieces shall not be chamfered. However, if the chipping of the test
pieces from the edges affects the results, the edges may be chamfered, but the amount of the chamfering
shall be as small as possible. Annex A provides a method to correct the calculation of Young’s modulus
for an edge chamfered test piece or test piece with rounded edges.
This test method measures Young’s modulus parallel to the length of the test piece and shear modulus as
an aggregate of different directions. If the test material is likely to be elastically anisotropic, care shall be
taken in the selection of test piece orientations and in the interpretation of the test results.
The maximum grain size measured in accordance with EN ISO 13383-1, excluding deliberately added
whiskers, shall be less than 10 % of the minimum dimension of the test piece.
This test method is not satisfactory for test pieces that have major discontinuities, such as large cracks
(surface or internal) or internal voids.
The surface of the test piece shall be smooth and flat. The surface shall be finished using a fine grind
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