EN 60672-2:2000

SLOVENSKI STANDARD
01-marec-2001
1DGRPHãþD
SIST HD 426.2 S1:1998
Ceramic and glass insulating materials - Part 2: Methods of test (IEC 60672-2:1999)
Ceramic and glass insulating materials -- Part 2: Methods of test
Keramik- und Glasisolierstoffe -- Teil 2: Prüfverfahren
Matériaux isolants à base de céramique ou de verre -- Partie 2: Méthodes d'essai
Ta slovenski standard je istoveten z: EN 60672-2:2000
ICS:
29.035.30 .HUDPLþQLLQVWHNOHQL Ceramic and glass insulating
L]RODFLMVNLPDWHULDOL materials
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

INTERNATIONAL IEC
STANDARD 60672-2
Second edition
1999-12
Ceramic and glass insulating materials –
Part 2:
Methods of test
 IEC 1999 Copyright - all rights reserved
No part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical,
including photocopying and microfilm, without permission in writing from the publisher.
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International Electrotechnical Commission
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60672-2 © IEC:1999 – 3 –
CONTENTS
Page
FOREWORD . 7
Clause
1 Scope . 11
2 Normative references. 11
3 General notes on tests. 13
4 Dye penetration test (liquid absorption). 17
5 Bulk density and open (apparent) porosity . 19
6 Flexural strength. 25
7 Modulus of elasticity . 33
8 Mean coefficient of linear thermal expansion. 41
9 Specific heat capacity . 45
10 Thermal conductivity . 47
11 Resistance to thermal shock . 49
12 Glass transition temperature (for glass materials only). 53
13 Electric strength.55
14 Withstand voltage . 61
15 Relative permittivity, temperature coefficient of permittivity and dissipation factor . 63
16 Volume resistivity. 67
Annex A (normative) Standard temperature conditions for testing. 85
Bibliography . 87
Figure 1 – Apparatus for applying high pressure to dye solution contained
in a metal container. 71
Figure 2 – Function of mechanical testing jigs and symbols for strength tests . 73
Figure 3 – Shape, symbols and dimensions of flexural strength test pieces . 75
Figure 4 – Deflection parameters and method of determination of deflections
for Young's modulus determination. 77
Figure 5 – Graphical construction for determination of transition temperature T of glasses . 79
g
Figure 6 – Test piece for electrical strength and withstand voltage tests, method B. 81
Figure 7 – Electrode arrangement for electric strength measurement, method A . 83

60672-2 © IEC:1999 – 5 –
Page
Table 1 – Characteristics and minimum number of test pieces for each test . 15
Table 2 – Density of distilled water. 23
Table 3 – Dimensions of test pieces and flexural strength test jig
for various groups of ceramic materials . 29
Table 4 – Dimensions of test pieces for method B (see also figure 6) . 57
Table 5 – Values of k for various values of thickness of test pieces. 59
Table A.1 – Standard temperature conditions for testing . 85

60672-2 © IEC:1999 – 7 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
–––––––––––––
CERAMIC AND GLASS INSULATING MATERIALS –
Part 2: Methods of test
FOREWORD
1) The IEC (International Electrotechnical Commission) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of the IEC is to promote
international co-operation on all questions concerning standardization in the electrical and electronic fields. To
this end and in addition to other activities, the IEC publishes International Standards. Their preparation is
entrusted to technical committees; any IEC National Committee interested in the subject dealt with may
participate in this preparatory work. International, governmental and non-governmental organizations liaising
with the IEC also participate in this preparation. The IEC collaborates closely with the International
Organization for Standardization (ISO) in accordance with conditions determined by agreement between the
two organizations.
2) The formal decisions or agreements of the IEC on technical matters express, as nearly as possible, an
international consensus of opinion on the relevant subjects since each technical committee has representation
from all interested National Committees.
3) The documents produced have the form of recommendations for international use and are published in the form
of standards, technical specifications, technical reports or guides and they are accepted by the National
Committees in that sense.
4) In order to promote international unification, IEC National Committees undertake to apply IEC International
Standards transparently to the maximum extent possible in their national and regional standards. Any
divergence between the IEC Standard and the corresponding national or regional standard shall be clearly
indicated in the latter.
5) The IEC provides no marking procedure to indicate its approval and cannot be rendered responsible for any
equipment declared to be in conformity with one of its standards.
6) Attention is drawn to the possibility that some of the elements of this International Standard may be the subject
of patent rights. The IEC shall not be held responsible for identifying any or all such patent rights.
International Standard IEC 60672-2 has been prepared by subcommittee 15C: Specifications,
of IEC technical committee 15: Insulating materials.
This second edition cancels and replaces the first edition published in 1980 and constitutes a
technical revision. In redrafting this standard, the intention has been to improve the
instructions in the test methods so that the document becomes more usable in the testing
laboratory. Some of the ambiguities of test conditions have been removed, particularly for
mechanical testing for which the recent development of improved understanding of significant
factors in testing has allowed a better definition of requirements and a restriction of the range
of previously optional test piece sizes.
The text of this standard is based on the following documents:
FDIS Report on voting
15C/1049/FDIS 15C/1069/RVD
Full information on the voting for the approval of this standard can be found in the report on
voting indicated in the above table.
This publication has been drafted in accordance with the ISO/IEC Directives, Part 3.

60672-2 © IEC:1999 – 9 –
IEC 60672 consists of the following parts under the general title Ceramic and glass insulating
materials:
Part 1:1995, Definitions and classification;
Part 2:1999, Methods of test;
Part 3:1997, Specifications for individual materials.
Annex A forms an integral part of this standard.
The committee has decided that this publication remains valid until 2008. At this date, in
accordance with the committee’s decision, the publication will be
reconfirmed;
withdrawn;
replaced by a revised edition, or
amended.
60672-2 © IEC:1999 – 11 –
CERAMIC AND GLASS INSULATING MATERIALS –
Part 2: Methods of test
1 Scope
This part of IEC 60672 is applicable to ceramic, glass and glass-ceramic materials to be used
for electrical insulation purposes. This standard specifies methods of test. It is intended to
provide test results typical of the material from which the test pieces are processed. Since, in
the majority of cases, ceramic components for insulating purposes are of rather different size
and shape to test pieces, the results of such tests provide only a guide to the actual
properties of components. The limitations imposed by the method of forming and processing
are discussed where relevant.
2 Normative references
The following normative documents contain provisions which, through reference in this text,
constitute provisions of this part of IEC 60672. For dated references, subsequent
amendments to, or revisions of, any of these publications do not apply. However, parties to
agreements based on this part of IEC 60672 are encouraged to investigate the possibility of
applying the most recent editions of the normative documents indicated below. For undated
references, the latest edition of the normative document referred to applies. Members of ISO
and IEC maintain registers of currently valid International Standards.
IEC 60093:1980, Methods of test for volume resistivity and surface resistivity of solid
electrical insulating materials
IEC 60212:1971, Standard conditions for use prior to and during the testing of solid electrical
insulating materials
IEC 60243-1:1998, Electric strength of insulating materials – Test methods – Part 1: Tests at
power frequencies
IEC 60250:1969, Recommended methods for the determination of the permittivity and
dielectric dissipation factor of electrical insulating materials at power, audio and radio
frequencies, including metre wavelengths
IEC 60345:1971, Method of test for electrical resistance and resistivity of insulating materials
at elevated temperatures
IEC 60672-1:1995, Ceramic and glass insulating materials – Part 1: Definitions and
classification
IEC 60672-3:1997, Ceramic and glass insulating materials – Part 3: Specifications for
individual materials
IEC 61006:1991, Methods of test for the determination of the glass transition temperature of
electrical insulating materials

60672-2 © IEC:1999 – 13 –
ISO/DIS 463, Geometrical product specifications (GPS) – Dimensional measuring instruments –
1)
Dial gauges – Design and metrological requirements (Revision of ISO/R 463:1965)
ISO 758:1976, Liquid chemical products for industrial use – Determination of density at 20 °C
ISO 3534-1:1993, Statistics – Vocabulary and symbols – Part 1: Probability and general
statistical terms
ISO 3611:1978, Micrometer callipers for external measurement
ISO 6906:1984, Vernier callipers reading to 0,02 mm
ISO 7884-8:1987, Glass – Viscosity and viscometric fixed points – Part 8: Determination of
(dilatometric) transformation temperature
3 General notes on tests
3.1 Test pieces
Test pieces shall be processed under conditions closely similar to those normally employed
for the manufacture of components, and in sufficient numbers to be representative of those
conditions. It is emphasized that results from the test pieces are affected by the method of
forming and, in many cases, by the method of surface finishing; methods used should, as far
as possible, be those used in the production of items. For each test result reported, the
method of manufacture of the test piece shall be specified. All numerical values determined
according to these test methods apply only to the test pieces prescribed. They cannot be
extended to test pieces and ceramic products of other shapes and dimensions nor of other
types of manufacture. The minimum number of test pieces for each test is given in table 1.
NOTE For thermally toughened glass test pieces, the thermally pre-stressed state of glass depends on the
following factors:
– thermal expansion below and above the transition range (see IEC 61006);
– viscosity/temperature relation;
– thermal diffusivity, i.e. thermal conductivity (specific heat capacity × bulk density);
– elastic properties;
– starting temperature of cooling;
– heat transfer coefficient;
– thickness and form of glass product.
As a result of the last factor, test pieces from the same glass but of different shape and thickness have different
tempering levels, although they are tempered under the same conditions. Consequently, it is impossible to have a
special test piece which represents the properties of toughened glass items of other shapes and thickness.
Therefore, physical properties of thermally tempered glass items which show corresponding dependence on the
tempering state can be determined only on the item itself, and it is recommended that this procedure is adopted
whenever possible. This applies to properties such as flexural strength, resistance to thermal shock, volume
resistivity and dissipation factor.
––––––––––
1)
To be published.
60672-2 © IEC:1999 – 15 –
Table 1 – Characteristics and minimum number of test pieces for each test
Clause Test Number of Shape and dimensions
test pieces
4 Dye penetration test 3 Fragments or small components; see 4.2
5 Bulk density/ 3 Fragments or small components;
open porosity see 5.2, note
6 Flexural strength 10 See table 3
7 Modulus of elasticity 3 Bar-shaped, preferably with a support
span-to-thickness ratio > 50; see 7.3
8 Mean coefficient of linear 2 Appropriate to the apparatus used
thermal expansion
9 Specific heat capacity 2 Appropriate to the apparatus used
10 Thermal conductivity 2 Appropriate to the apparatus used;
see 10.2
11 Thermal shock 30
Rods 10 mm diameter × 120 mm long
12 Glass transition temperature 2 Appropriate to the apparatus used
(T , for glass only)
g
13 Electric strength 10 Discs as described in 13.3
14 Withstand voltage 10 Discs as described in 13.3
15 Relative permittivity/ 3 Discs in accordance with IEC 60250,
dissipation factor as described in clause 15
16 Volume resistivity 2 Discs in accordance with IEC 60345,
as described in clause 16
3.2 Presentation of results
The test report shall include the following:
a) name of testing establishment;
b) a reference to this standard;
c) date of test;
d) identification of the item, test piece or test material (type, manufacturer, shaping process,
batch number, date of manufacture, etc., as appropriate);
e) the test performed;
f) the preparation, shape and dimensions of the test pieces and the number tested (see
table 1 for the minimum number for each test);
g) details relevant to the test or tests undertaken (see requirements listed under each test
method);
h) individual results from each test piece;
i) the arithmetic mean value of the individual results, and the standard deviation.
3.3 Evaluation against a minimum specification
For the purpose of assessing whether a material has satisfactory properties compared with
the minimum specification laid down in IEC 60672-3, the mean value of the specified number
of determinations shall be compared with the maximum or minimum value required in
IEC 60672-3, or with the range of values permitted.

60672-2 © IEC:1999 – 17 –
4 Dye penetration test (liquid absorption)
NOTE 1 This test is intended to detect the presence of continuous interconnected porosity or microcracks which
would render the material unsatisfactory from the high-voltage dielectric breakdown point of view. The test is not
applicable to glass materials with the exception of sintered glass products. The test is also not intended as a
routine inspection test for minor cracks or pores in small components, for which alternative less stringent tests, for
example a liquid dye vacuum test, may be appropriate.
NOTE 2 For dark-coloured materials, the dye chosen should be such as to give contrast with the natural colour of
the material. Fluorescent dyes may be appropriate, but only if used as described in 4.4.
4.1 Test apparatus
The test apparatus shall include a pressure vessel capable of withstanding a pressure of
at least 30 MPa, a high-pressure pump and a pressure gauge. Test pieces are immersed in
dye solution which either directly fills the pressure vessel, or is contained in a metal container
inside the pressure vessel to which pressure can be transmitted by the pressurizing
hydraulic oil through a rubber bung or piston (see figure 1). An oven capable of maintaining
120 °C ± 5 °C is required for test piece conditioning.
Test pieces
4.2
Fragments of ceramic shall be used. No more than 25 % of the total surface area may be
glazed or have an "as-fired" skin. The test shall be made on fragments from at least three
separate components or test pieces.
4.3 Dye
The dye solution shall be prepared containing typically 1 g to 3 g of dye in 1 l of ethyl alcohol
or methylated spirits, or other suitable solvent.
NOTE 1 Suitable non-toxic dyes include xanthan/triaryl methane mixtures.
NOTE 2 Due regard should be paid to health hazards and environmental implications of using and disposing of
organic dyes and solvents.
4.4 Method of test
The test pieces shall be free from oil or dirt of any type, and shall be washed if necessary.
The test pieces shall be dried at 120 °C ± 5 °C for a period of not less than 3 h prior to the
test, and are then broken into fragments of appropriate size.
The test pieces shall be immersed in the dye solution, which is either directly in the pressure
vessel, or in the metal container sealed with the rubber seal or piston which is then placed in
the pressurising vessel. The system shall be pressurized to not less than 15 MPa, and for a
time period such that the product of pressure in megapascals (MPa) and time in hours (h) is
not less than 180. After the appropriate time, the fragments shall be taken from the system,
washed in water, dried and broken. The freshly broken surfaces shall be examined, using
normal vision for any sign of penetration of the dyestuff. These surfaces shall show no
penetration. Penetration of dye into small cracks, produced when initially preparing fragments,
shall not be taken into consideration.

60672-2 © IEC:1999 – 19 –
4.5 Test report
In addition to the information required under items a) to i) in 3.2, the test report shall contain
the following:
a) the pressure, in MPa, and the time under pressure, in h;
b) the size, shape and number of test pieces and the fragments produced therefrom;
c) whether or not penetration of dye was observed on any freshly fractured surface of
fragment.
5 Bulk density and open (apparent) porosity
NOTE 1 These methods are not appropriate for the determination of open porosity levels of less than 0,5 % by
volume, since reliable numerical results cannot be obtained. The existence of such porosity levels can be more
reliably determined using the dye test described in clause 4.
NOTE 2 These tests are appropriate for the determination of the bulk characteristics of materials. It should be
noted that as-fired skins on ceramic components may be impervious, even if bulk material may have some open
porosity.
NOTE 3 The use of liquid immersion media other than distilled water is permissible provided that the density of
–3
the liquid is measured to ±0,001 Mg.m at the temperature of the weighings of the immersed test piece. Suitable
liquids include paraffin, butyl alcohol and other organic liquids of low volatility.
NOTE 4 By agreement, other methods, for example gas pyknometry, may be used, but the results may not be
comparable to those produced by the methods described below.
5.1 Test apparatus
The following apparatus is required for this test:
a) a hydrostatic balance (a balance suitable for determining the apparent mass of a test
piece suspended in a liquid) capable of weighing to an accuracy of ±0,01 g;
b) a thin, de-greased metallic suspension wire of diameter not exceeding 0,20 mm;
c) either:
method A: a gas-tight vessel (bell jar or desiccator) connected to a suitable vacuum pump,
and which is provided with suitable means for measuring the pressure and for admitting
liquid, or
method B: a vessel for containing boiling water and equipped with non-corrodable wide-
mesh netting to support the test piece(s) positioned at least 10 mm above the base of the
vessel;
NOTE Method B is not recommended if inflammable organic liquids are to be used owing to potential safety
hazards.
d) an oven for drying test pieces;
e) a lint-free cloth for removing excess liquid from test pieces;
f) a supply of demineralized or freshly distilled water, or other suitable liquid (see note 3
above).
60672-2 © IEC:1999 – 21 –
5.2 Test pieces
At least three determinations shall be made. If an open porosity determination is required,
each test shall employ at least three fragments of ceramic material with a total mass of
between 50 g and 80 g. No more than 25 % of the surface may be either glazed or have an
"as-fired" skin. The fragments shall be clean and degreased. Any chips liable to become
detached during the test and any loose dust shall be removed by brushing before the test.
NOTE If density determinations are required on individual, small components weighing less than 50 g each,
the method cited here may be used provided that the accuracy of weighing is ±0,001 g for test pieces of greater
than 3 g mass, or ±0,0001 g for test pieces of 1 g to 3 g mass. For components of mass less than 1 g the methods
described below are not adequate, and several components should be tested together to make a larger mass.
Individual components should not have a mass of less than 0,1 g.
5.3 Method of test
Dry the test piece fragments in the oven at 120 °C ± 5 °C for at least 2 h and until constant
mass m is achieved.
o
Method A: Place the test piece fragments in a suitable container inside the vacuum vessel.
Close the vessel and evacuate it to a pressure of less than 3 kPa and maintain this for at
least 5 min. Isolate the vessel from the vacuum pump and observe any steady rise in
pressure. If a rise to greater than 4 kPa occurs in less than 5 min, the test piece is continuing
to out-gas. Reconnect the vacuum pump and continue evacuating until there is no significant
change in a 5 min period on isolation of the vacuum vessel. Admit freshly boiled distilled
water at 23 °C ± 2 °C to the test piece in the container until the test piece is covered, and
continue evacuation for a further period of at least 5 min. After this period, isolate the vacuum
pump and admit air to the vessel, and remove the test piece in its container of water. For low-
porosity materials, allow to stand in distilled water for at least 6 h.
Method B: Place the test piece fragments in the vessel and cover with distilled water. Heat to
boiling point and boil for at least 30 min; then allow to cool to room temperature while still
immersed, and stand in distilled water for at least 6 h.
NOTE Method A and method B may not give exactly equivalent results for open-porosity determination, method B
being considered to be less effective in removing entrained air from the test pieces.
Whichever method is used, weigh the test piece fragments in distilled water, using a thin,
clean metal suspension wire (m ). Remove the test pieces and replace in the distilled water.
w
Weigh the suspension wire submerged to the same depth as when used for weighing the
immersed test pieces (m ). Record the temperature of the water (T) to the nearest 0,1 °C.
s
Remove the test piece fragments from the water, wipe each with the damp lint-free cloth to
remove surface water only, and reweigh in air (m ).
h
60672-2 © IEC:1999 – 23 –
5.4 Calculation of results
Calculate the bulk density (ρ ) and open (apparent) porosity (p ) as follows:
a a
m × ρ m − m
o w h o
ρ = p = × 100 (1)
a a
m − m + m m − m + m
h w s h w s
where
–3
ρ is the bulk density, in Mg⋅m ;
a
p is the open (apparent) porosity, in vol %;
a
m is the mass of the dry test piece, in g;
o
m is the apparent mass of the test piece and suspension wire immersed in water, in g;
w
m is the apparent mass of the suspension wire immersed to same level in water, in g;
s
m is the mass of the soaked test piece in air, in g;
h
–3
ρ is the density of water or other immersion liquid at the test temperature T, in Mg⋅m .
w
The density of distilled water at temperature T is given in table 2. If a liquid other than distilled
water is used, its density shall be determined following the procedure laid down in ISO 758 at
the same temperature as used for the test piece density determination.
Table 2 – Density of distilled water
Temperature Density
o
–3
C ρ , Mg⋅m
w
18 0,99860
19 0,99841
20 0,99820
21 0,99799
22 0,99777
23 0,99754
24 0,99730
25 0,99704
26 0,99678
5.5 Test report
In addition to the information required under items a) to i) in 3.2, the test report shall include
the following:
a) the method used (method A or method B);
b) the immersion liquid used, if not distilled water;
c) the temperature at which the density determination was made, in °C;
–3
d) the density of the immersion liquid at the test temperature, in Mg⋅m ;
e) the time taken to complete the soaking of the test piece, in h;
–3 –3
f) the individual values of bulk density, in Mg⋅m (rounded to the nearest 0,01 Mg⋅m ), and
open porosity, in % (rounded to the nearest 0,1 %), determined on each test piece.

60672-2 © IEC:1999 – 25 –
6 Flexural strength
NOTE The fracture strength determined from a flexural test depends upon many factors including test piece size
and cross-sectional geometry, surface finish, stressing rate, humidity of the environment, test jig geometry and
mode of operation. The result of such a test gives a guide to the general strength properties of the material, but
cannot be used directly as a figure for design purposes. It can be used as a quality-control check, and for a broad
intercomparison of different materials, provided that relevant test parameters, such as those given above, are kept
constant.
6.1 Test apparatus
The apparatus required for this test includes the following:
a) mechanical testing machine capable of applying a force to a test piece at a constant
loading rate or cross-head movement rate, and of recording peak force applied with an
accuracy of ±1 %;
*
NOTE ISO 7500-1 [2] provides information on the requirements for linearity and resolution of force recording in
mechanical testing machines when used under tensile force, procedures which may be applied also to the
compression mode, such as typically encountered in flexural strength testing.
b) a specimen loading jig of geometry and dimensions appropriate to the test being
performed (see 6.2 and table 3);
c) a micrometer in accordance with ISO 3611 capable of measuring dimensions of test
pieces to an accuracy of ±0,01 mm;
d) a travelling microscope, vernier callipers in accordance with ISO 6906, or other suitable
device for measuring spacing of centres of test piece support and loading rods to an
accuracy of ±0,05 mm.
6.2 Loading jigs
Method A – three-point bend
The test jig or fixture consists of two parallel test piece support rods upon which the test piece
is laid, and one loading rod to apply a force to the test piece, midway between the support
rods. The support rods shall be free to rotate about an axis parallel to their lengths in order to
minimize friction effects, and one of the support rods shall be free to rotate about an
orthogonal axis parallel to the length of the test piece in order to permit alignment. The
loading rod shall have a similar axis of rotation in order to achieve uniform loading across the
test piece. The diameter of the support and loading rods and the distance between the
centres of the support rods (the span) shall be as defined in table 3, and the surface shall be
maintained in a polished, burr-free condition. The force is applied orthogonally to the plane of
the test piece and/or support rods. A typical jig arrangement is shown in figure 2.
Method B – four-point bend
The test jig comprises two supports as in method A, with identical specification. Two loading
rods spaced with their centres half the support span distance apart (see 6.4.1 c)) are placed
symmetrically to within ±0,2 mm between the support rods, and force is applied orthogonally
to the test piece. The two loading rods shall be free to rotate about an axis parallel to their
lengths, and shall also be capable of separately rotating about an axis parallel to the length of
the test piece. In this way, full alignment of loading and support rods may be achieved.
––––––––––
*
Figures in square brackets refer to the bibliography.

60672-2 © IEC:1999 – 27 –
NOTE The rotation of support or loading rods about an axis parallel to the test piece length is not required for
testing round or flattened, circular test pieces. For test piece surfaces machined flat and parallel-faced, this
rotation is not essential for the support rollers, nor for the loading rollers of method B, but there should still be
relative rotation between the loading roller(s) and the support rollers.
6.3 Test pieces
Test pieces shall be prepared in the sizes given in table 3 and figure 3 according to their
classification (see IEC 60672-1). The method of preparation of ceramic material should be
appropriate to the expected manufacturing method used for components, for example
isostatically pressed or extruded. Any surface preparation technique such as grinding,
abrasion, milling, etc., should be noted.
NOTE 1 The test piece and jig dimensions given in table 3 may, by agreement between customer and supplier, be
modified to suit particular circumstances. The support span to test piece-depth ratio should not be less than 10:1
for use of the equations in 6.5. Full details of the test procedure should be given in any test report. This standard is
permitted to be cited only if all other aspects of procedure conform to the requirements for this test.
For glass and glass-ceramic materials, an abraded surface shall be used, prepared using
falling sand, the quantity, flow rate and fall height of which are to be specified in the test
report.
NOTE 2 The fracture strength of many ceramics, especially fine-grained ones, and of glasses and glass-ceramics
is strongly influenced by the surface condition since the surface is subjected to the highest stress in a flexure test.
The surface treatment used for test pieces should be comparable with that used for manufactured components.
The minimum number of test pieces for each test shall be 10.
NOTE 3 If required, a larger number of test pieces may be tested in order to obtain statistical information, for
example a Weibull modulus. If such is the case, it is recommended that a minimum of 30 test pieces is tested.
6.4 Method of test
The support rod span, and, in the case of method B, the loading roller span as well, shall be
measured to the nearest 0,1 mm. The test piece cross-sectional dimensions shall be
measured with a micrometer to the nearest 0,02 mm. In the case of nominally round cross-
section test pieces, measure the maximum and minimum diameters at three positions and
calculate the arithmetic mean. For flattened circular and rectangular section bars, measure
the widths and thicknesses at a minimum of three positions near the centre of the test piece,
and calculate the arithmetic mean. Place the test piece centrally across the support rollers
and the loading roller (method A) centrally or the pair of loading rollers (method B)
symmetrically to within ±0,2 mm. If not already done, place the test jig in the test machine.
Apply an increasing force to the loading roller (method A) or equally to the two rollers
–1 –1
(method B) at a rate between 20 N⋅s and 50 N⋅s , either directly selected, or indirectly by
choice of an appropriate machine cross-head displacement rate, and continue until the test
piece fractures. Record the peak force to an accuracy of 1 %. Repeat the test on each test
piece of the batch.
60672-2 © IEC:1999 – 29 –
Table 3 – Dimensions of test pieces and flexural strength test jig for various groups
of ceramic materials
Test piece dimensions Jig size
mm mm
Method
Group Sub-group
Length Rod Flattened Rectan- Support Roller
A or B
diameter circular gular span diameter
L d
h × b h × b
C 100 All except C 111 120 10 – – A 100 10
C 111 120 – 10 × 8 10 × 10 A 100 10
C 200 All 120 10 10 × 8 10 × 10 A 100 10
C 300 All 50 5 – 3 × 4 A 40 5
C 400 All 120 10 10 × 8 10 × 10 A 100 10
C 500 All 120 10 10 × 8 10 × 10 A 100 10
C 600 All 120 10 10 × 8 10 × 10 A 100 10
C 700 All 50 5 – 3 × 4 A or B 40 5
C 800 C 810 50 5 – 3 × 4 A or B 40 5
C 820 120 10 – 10 × 10 A 100 10
C 900 All 50 5 – 3 × 4 A or B 40 5
GC Both 50 5 – 3 × 4 A or B 40 5
GM Both 50 5 – 3 × 4B 40 5
G All 120 10 –– B 100 10
6.4.1 Other requirements
a) Flattened circular test pieces shall be pressed in the 10 mm direction, and shall be tested
with the direction of load application in this same direction.
b) Rectangular- or square-section test pieces shall have their long edges either chamfered
with a 45° plane or rounded with an edge radius. Dimensions of the chamfers and
roundings are given in figure 3, and shall be prepared by grinding or polishing parallel to
the length of the test piece.
c) The inner to outer span ratio for method B shall be 1:2. Tolerances on span dimensions
shall be ±2 % of the values given in table 3.
d) Size tolerances on test piece cross-section dimensions are as follows:
– diameter: ±5 %, uniform along test piece length to ±2 %;
– width b or thickness h: ±5 % of the dimension in table 3. The test piece surfaces shall
be flat and parallel to within ±0,02 mm.
e) The minimum strength levels of this standard specified in IEC 60672-3 relate to
determinations by method A, three-point flexure, except where only method B is permitted
in table 3. Four-point flexure test results (method B) are typically 10 % to 20 % lower than
three-point flexure test results.

60672-2 © IEC:1999 – 31 –
6.5 Calculation of results
The value of σ , the flexural strength, of each test piece is calculated using the appropriate
f
equation as follows:
Method A – three-point bend:
a) circular cross-section:
8 × F × I
σ = (2)
f
π × d
b) flattened circular cross-section:
8 × F × I
σ = (3)
f
π × b × h
c) rectangular cross-section:
× ×
3 F I
σ = (4)
f
2 × b × h
Method B – four-point bend:
a) circular cross-section:
16 × F × a
σ = (5)
f
π × d
b) flattened circular cross-section:
16 × F × a
σ = (6)
f
π × b × h
c) rectangular cross-section:
3 × F × a
σ = (7)
f
b × h
where
σ is the flexural strength, in MPa;
f
F is the total force applied to the test piece at fracture, in N;
l is the distance between support points, in mm;
a is the distance between a support point and an adjacent loading point in method B, in mm;
d is the diameter of round section test piece, in mm;
b is the width of flattened circular or rectangular test piece, in mm;
h is the thickness of test piece (in direction of loading), in mm.
6.6 Test report
In addition to the information required under items a) to i) in 3.2, the test report shall contain:
a) the test method used (A or B) and, if the test jig is not in accordance with the requirements
of table 3 (see clause 6.3, note 1), the jig size, in mm;
–1
b) the stressing rate used, in MPa⋅s , determined from the slope of the force/time
characteristics;
60672-2 © IEC:1999 – 33 –
c) any relevant details concerning the test pieces, such as manufacturing details, surface
finishing method, etc.;
d) the number of test pieces tested;
e) the individual strength results σ , in MPa;
f
f) the mean strength results and the standard deviation (ISO 3534-1), in MPa;
g) where relevant, details of any statistical procedure employed to analyse the data, and the
results therefrom, for example Weibull modulus.
7 Modulus of elasticity
NOTE 1 The test procedure described below is for determination of Young's modulus by static bending.
Alternative methods, which may also be used to obtain shear modulus and Poisson's ratio, are impact excitation,
resonant bar and velocity of sound techniques. These other methods may be used by mutual agreement, but are
outside the scope of this standard, which may not be referred to in the test report.
NOTE 2 The test procedure assumes that the test pieces are homogeneous and isotropic linearly elastic
materials. At high porosity levels, the methods may be inappropriate.
7.1 Definitions
7.1.1 Young's modulus
The stress required in a material to produce unit uniaxial strain in tension or compression,
often referred to as elastic modulus.
7.1.2 Static elastic modulus
Young's modulus determined in an isothermal condition by stressing statically or
quasistatically.
7.1.3 Dynamic elastic modulus
Elastic modulus determined non-quasistatically, i.e. under adiabatic conditions, such as in the
impact excitation, resonance or velocity of sound methods.
7.2 Test apparatus
The test apparatus required for this test comprises:
a) A mechanical testing machine capable of applying a force to a test piece at a constant
loading rate or constant cross-head movement rate, and of recording the force with an
accuracy of 0,1 % and with a resolution of better than 0,1 N.
NOTE 1 ISO 7500-1 [2] provides information on the requirements for linearity and resolution of force recording in
mechanical testing machines when used under tensile force, procedures which may also be applied to the
compression mode, such as typically encountered in flexural modulus testing.
b) A flexural test jig similar to that employed for flexural strength testing, either three-point
bending or four-point bending (see 6.2). The support and loading rollers of the test jig
shall be free to roll and to articulate to ensure axial and even loading. Either three or four-
point bending may be used, but four-point bending is required if strain gauges are
employed.
NOTE 2 Articulation may not be required for carefully machined flat and parallel-faced test pieces.

60672-2 © IEC:1999 – 35 –
The flexural displacement may be measured by one of two methods:
Method (a)
A linear displacement transducer measuring the differential displacement between two (or
three) defined points on the bent test piece between the support rollers. For four-point
bending, the defined points shall be the centre of span and opposite one (or both) loading
points (see figure 4). For three-point bending, the defined points shall be the centre of the
span and at one (or both) support rollers. If a dial gauge is used, this shall be accurate
to 0,001 mm in accordance with ISO 463. Any other device shall be accurate to 0,001 mm,
shall have an output linear with displacement to better than 0,01 %, and shall be calibrated to
an accuracy of 0,1 %.
Method (b)
From the apparent cross-head displacement of a mechanical testing machine over a given
loading and unloading range suitably corrected for machine compliance (see figure 4).
Machine compliance shall be determined by replacing the test piece with a steel or ceramic
bar at least 15 mm thick and repeating the measurement. The displacement recording device,
for example a chart recorder, shall be calibrated by comparing the recorded cross-head
displacement with the actual crosshead movement determined, using a dial gauge in
accordance with ISO 463 or other linear displacement transducer accurate to 0,001 mm, with
output linear to 0,01 % and calibrated to an accuracy of 0,1 %.
NOTE 3 Method (b) above can be inaccurate if the machine and testing jig are not adequately and reproducibly
–1
stiff when applying a force to the test piece. A machine compliance of not more than 0,01 mm·kN should be
employed. In addition, with this method, the force displacement traces may be neither straight nor equal in loading
and unloading, as indicated schematically in the lower part of figure 4.
Alternatively, the surface strain induced by bending may be determined as follows:
Method (c)
Using one or more strain gauges mounted on the surface of the test piece. Four-point bending
only shall be used. The gauge shall be mounted between the loading points on the tensile
side (or on both sides) at the mid-point of the span, and shall not be longer than the span of
the loading rollers. The strain gauge(s) and the associated bridge circuit shall have an
–5
accuracy of better than 0,1 % and shall be capable of resolving a strain of less than 10 .
7.3 Test pieces
The preferred test piece shape is a thin flat strip with a support span to thickness ratio of > 50
and a width to thickness ratio of > 4.
NOTE Thicker test pieces such as those described in table 3 may lead to unsatisfactory errors of measurement,
unless the strain gauge method is used. Round section test pieces should have a support span to diameter ratio
of >40, but should not be used in conjunction with strain gauges.

60672-2 © IEC:1999 – 37 –
Test pieces of lengths at least 5 mm greater than the test span shall be machined flat and
parallel-faced to better than ±1 % of the h and b dimensions or, in the case of round bars, to
better than ±1 % of the diameter, d. Rectangular section bars shall not be edge-chamfered.
For the strain gauge method, bars shall be flat and parallel-faced to within ±1 % thickness. At
least three test pieces of each material shall be made.
7.4 Test method
Measure the test piece dimensions b and h at several points to the nearest 0,01 mm, and take
the mean value. Place each test piece in turn in the test jig, as for strength testing. Apply
a force progressively using a constant cross-head displacement rate, which may be in the
–1 –1
range 0,001 mm⋅min to 0,5 mm⋅min . Record the displacement or strain according to the
method
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