IEC 61631:2020
(Main)Test method for the mechanical strength of cores made of magnetic oxides
Test method for the mechanical strength of cores made of magnetic oxides
IEC 61631:2020 specifies a test method for the mechanical strength of cores made of magnetic oxides. This test method is suitable for most of the E-cores, ETD-cores, I-cores and ring-cores but other core types such as U-cores could be tested according to a derived method agreed by the parties concerned. This document is also applicable to the mechanical strength measurement of magnetic powder cores. This edition includes the following significant technical changes with respect to the previous edition:
- the phrase: "This document is also applicable to the mechanical strength measurement of magnetic powder cores" has been added in the scope;
- IEC 61246 has been replaced by IEC 63093-8; EN 1002-2 has been replaced by ISO 7500-1; ISO 4677-1 and ISO 4677-2 have been withdrawn;
- dimensions D and F in Figure A.1 and Table A.1 have been changed to be consistent with Figure 1 of IEC 63093-8:2018;
- addition of the content of ring-cores test;
- addition of Annex B;
- the location of the jig is amended in Figure 3;
- in Figure 5, the roller bars are moved to the edge of the I-core, aligned with the core.
Méthode d'essai pour la résistance mécanique des noyaux en oxydes magnétiques
IEC 61631:2020 spécifie une méthode d'essai pour la résistance mécanique des noyaux en oxydes magnétiques. Cette méthode d'essai est adaptée à la plupart des noyaux E, noyaux ETD, noyaux I et noyaux toriques, mais d'autres types de noyaux tels que les noyaux en U peuvent être soumis aux essais selon une méthode dérivée convenue par les parties concernées. Le présent document est également applicable au mesurage de la résistance mécanique des noyaux en poudre magnétique.
Cette édition inclut les modifications techniques majeures suivantes par rapport à l'édition précédente:
la phrase "Le présent document est également applicable au mesurage de la résistance mécanique des noyaux en poudre magnétique" a été ajoutée au domaine d’application;
l’IEC 61246 a été remplacée par l’IEC 63093-8; l’EN 1002-2 a été remplacée par l’ISO 7500-1; l’ISO 4677-1 et l’ISO 4677-2 ont été supprimées;
les dimensions D et F dans la Figure A.1 et le Tableau A.1 ont été modifiées pour se conformer à la Figure 1 de l’IEC 63093-8:2018;
ajout du contenu de l’essai des noyaux toriques;
ajout de l’Annexe B;
l’emplacement du gabarit est modifié dans la Figure 3;
dans la Figure 5, les barres de roulement sont déplacées au bord du noyau I, alignées avec le noyau.
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IEC 61631 ®
Edition 2.0 2020-05
REDLINE VERSION
INTERNATIONAL
STANDARD
colour
inside
Test method for the mechanical strength of cores made of magnetic oxides
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IEC 61631 ®
Edition 2.0 2020-05
REDLINE VERSION
INTERNATIONAL
STANDARD
colour
inside
Test method for the mechanical strength of cores made of magnetic oxides
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 29.100.10 ISBN 978-2-8322-8343-1
– 2 – IEC 61631:2020 RLV © IEC 2020
CONTENTS
FOREWORD . 3
INTRODUCTION . 2
1 Scope . 6
2 Normative references . 6
3 Terms and definitions . 6
4 Apparatus . 7
4.1 Test core support and loading wedge . 7
4.2 Testing device . 7
4.3 Humidity measuring device . 7
5 Test cores . 7
5.1 General . 7
5.2 Number of test cores . 7
5.3 Precautions . 7
6 Testing . 8
6.1 Test conditions . 8
6.2 Test procedures . 8
6.2.1 General . 8
6.2.2 Test of E-cores . 8
6.2.3 I-test Test of I-cores . 10
6.2.4 Test of ring-cores . 11
Annex A (normative) Standard dimensions of E-cores and their support
for strength test . 13
A.1 Introduction General . 13
A.2 Designation . 13
A.3 Test core support . 13
Annex B (normative) Standard dimensions of ring-cores and methods for strength test . 16
B.1 General . 16
B.2 Selection of mechanical strength test method for ring-core . 16
Bibliography . 17
Figure 1 – E test . 9
Figure 2 – W test . 9
Figure 3 – T test . 10
Figure 4 – M test . 10
Figure 5 – I test . 11
Figure 6 – Stretching method . 11
Figure 7 –Shearing method . 12
Figure 8 – Pressure method . 12
Figure A.1 – Designation of E-core . 13
Figure B.1 – Dimensions of ring-core . 16
Table A.1 – Test core support . 14
Table B.1 – Ring-core dimension designations . 16
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
TEST METHOD FOR THE MECHANICAL STRENGTH
OF CORES MADE OF MAGNETIC OXIDES
FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
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8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
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9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of
patent rights. IEC shall not be held responsible for identifying any or all such patent rights.
This redline version of the official IEC Standard allows the user to identify the changes
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– 4 – IEC 61631:2020 RLV © IEC 2020
International Standard IEC 61631 has been prepared by IEC technical committee 51:
Magnetic components, ferrite and magnetic powder materials.
This second edition cancels and replaces the first edition published in 2001. This edition
constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
a) the phrase: "This document is also applicable to the mechanical strength measurement of
magnetic powder cores" has been added in the scope;
b) IEC 61246 has been replaced by IEC 63093-8; EN 1002-2 has been replaced by
ISO 7500-1; ISO 4677-1 and ISO 4677-2 have been withdrawn;
c) dimensions D and F in Figure A.1 and Table A.1 have been changed to be consistent with
Figure 1 of IEC 63093-8:2018;
d) addition of the content of ring-cores test;
e) addition of Annex B;
f) the location of the jig is amended in Figure 3;
g) in Figure 5, the roller bars are moved to the edge of the I-core, aligned with the core.
The text of this International Standard is based on the following documents:
CDV Report on voting
51/1312/CDV 51/1333/RVC
Full information on the voting for the approval of this International Standard can be found in
the report on voting indicated in the above table.
This document has been drafted in accordance with the ISO/IEC Directives, Part 2.
The committee has decided that the contents of this document will remain unchanged until the
stability date indicated on the IEC website under "http://webstore.iec.ch" in the data related to
the specific document. At this date, the document will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
IMPORTANT – The 'colour inside' logo on the cover page of this publication indicates
that it contains colours which are considered to be useful for the correct
understanding of its contents. Users should therefore print this document using a
colour printer.
INTRODUCTION
The method specified in this document is intended to be used for obtaining agreements
between parties for material development, quality checking, characterization and data
acquisition purposes. The method places closely defined restrictions on the arrangement of
the test-piece and the function of the test apparatus, including the test-jigs, in order to
minimize the errors that can arise as a consequence of the test method.
All other factors are required to be stated in the test report in order to be allowed for in the
comparison of the behavior of the magnetic oxide cores. It is not possible to rigorously
standardize particular surface finishes, since it is difficult to control all the mechanical factors.
But, it is absolutely essential to mention the state of the surface in the report should be
mentioned, as surface defects can have a large effect on mechanical strength in certain types
of tests (see Clause 6). The extrapolation of mechanical strength data to other geometries,
multi-axial stressing, other rates of stressing or other environmental conditions, should be
viewed with caution. The origin of a fracture in a mechanical test piece can be a valuable
guide to the nature and position of strength-limiting defects (such as pores, large grains and
impurity concentration).
The results of strength tests are influenced by a combination of the following factors: the
microstructure of the material, the surface finishing procedure applied to the test cores, the
size and shape of the test cores, the mechanical parameters of the testing apparatus, the rate
of load application and the relative humidity of the ambient atmosphere. Because of the
ceramic nature of magnetic oxide cores, a considerable range of results is usually obtained
from a number of nominally identical test cores. Thus test results need to be are interpreted
with caution.
– 6 – IEC 61631:2020 RLV © IEC 2020
TEST METHOD FOR THE MECHANICAL STRENGTH
OF CORES MADE OF MAGNETIC OXIDES
1 Scope
This document specifies a test method for the mechanical strength of cores made of magnetic
oxides. This test method is suitable for most of the E-cores, ETD-cores, I-cores and ring-
cores but other core types such as U-cores could be tested according to a derived method
agreed by the parties concerned. This document is also applicable to the mechanical strength
measurement of magnetic powder cores.
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.
IEC 61246:1994, Magnetic oxide cores (E-cores) of rectangular cross-section and associated
parts – Dimensions
EN 10002-2:1992, Tensile testing of metallic materials – Part 2: Verification of the force
measuring system of the tensile testing machine
ISO 4677-1:1985, Atmospheres for conditioning and testing – Determination of relative humidity –
Part 1: Aspirated psychrometer method
ISO 4677-2:1985, Atmospheres for conditioning and testing – Determination of relative humidity –
Part 2: Whirling psychrometer method
ISO 7500-2, Metallic materials – Verification of static uniaxial testing machines – Part 2:
Tension creep testing machines – Verification of the applied force
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following
addresses:
• IEC Electropedia: available at http://www.electropedia.org/
• ISO Online browsing platform: available at http://www.iso.org/obp
3.1
mechanical strength
maximum recorded force at the instant of fracture of a magnetic oxide core when it is loaded
in with the bending stress
4 Apparatus
4.1 Test core support and loading wedge
Test cores shall be supported on free moving roller bars or on a flat support depending on
their size (see 6.2). The loading wedge, the roller bars and the stretch bar or the flat support
shall be made of hardened steel with a hardness of 40 HRC (HRC is Rockwell hardness) to
60 HRC. The loading wedge and the roller bars shall have a radius of 2 mm. The radius of the
contact part of the stretching rod head and the measured core is 2 mm. The loading wedge
and the stretch bar shall be connected to a device for measuring and recording the load
applied.
4.2 Testing device
The testing device shall be a mechanical testing machine capable of applying a force to the
loading wedge high enough to break the test core. The machine shall be capable of applying
the force at a constant loading rate. The machine shall be equipped with a device for
recording the peak load applied to the test core. The accuracy of the machine shall be in
accordance with EN 10002-2, Grade 1 (accuracy 1 % of the indicated load). The force
calibration of the machine shall be checked in accordance with EN 10002-2 ISO 7500-2.
4.3 Humidity measuring device
A humidity measuring device shall be as specified in ISO 4677-1 or ISO 4677-2 and shall be
capable of measuring relative humidity to an accuracy of ±2 %.
A humidity measuring device, such as, but not limited to, an aspirated psychrometer or
whirling psychrometer that is capable of measuring relative humidity to an accuracy of ±2 %
shall be used.
5 Test cores
5.1 General
The test cores shall be selected as agreed between the parties concerned. They may be
machined to the specified dimensions, because any machined surface plays an important role
in the mechanical strength (see the Introduction).
5.2 Number of test cores
For material development, characterization or quality checking, the minimum number of test
cores shall be five pieces. For statistical evaluation of strength data (for example, Weibull
parameters), the minimum number shall be thirty.
NOTE For comparison of data for different materials, it is important that the number of
specimens is high enough to obtain results with sufficient statistical confidence. Since the
confidence limits, in general, depend on the number of test results and their dispersion, the
number of test specimens should be decided on the basis of statistical considerations.
5.3 Precautions
The prepared test cores should be handled with care to avoid introduction of additional
damage. Test cores should be kept separately at all times, and should be wrapped
individually for transport.
– 8 – IEC 61631:2020 RLV © IEC 2020
6 Testing
6.1 Test conditions
The test shall be carried out at an ambient temperature between 15 °C and 35 °C. The
temperature shall not vary by more than 3 °C during the course of a test series. The relative
humidity shall be between 45 % and 85 % and shall not vary by more than 10 % during the
course of a test series.
6.2 Test procedures
6.2.1 General
The test core shall be arranged in the test apparatus in accordance with 6.2.2.2, 6.2.2.3,
6.2.2.4, 6.2.2.5, 6.2.3, 6.2.4.2.2, 6.2.4.2.3 or 6.2.4.2.4 as applicable (see Figure 1 to Figure
58). For standard dimensions of E-cores and their support for strength test see Annex A.
The E test and W test can be used for material-related purposes, while the M test and T test
can be used for process-related purposes. The I-test test of I-cores is only recommended for
flat-shaped test cores such as antenna rods. The test method of stretching, shearing and
pressure is only applicable to ring-cores. A preloading force of 5 N to 25 N shall be applied
because the upper and lower faces of the test cores are never absolutely parallel. The test
force shall then be applied at a loading rate of between 5 mm/min and 20 mm/min until the
test core fractures. The load at the instant of fracture shall be recorded. The fractured
fragments shall be identified and preserved for later fractographic examination.
6.2.2 Test of E-cores
6.2.2.1 Dimensions
The specifications and dimensions of E-cores are according to IEC 63093-8.
6.2.2.2 E test
For test core sizes equal to or larger than E13, the test core shall be placed on roller bars as
shown in Figure 1. For test core sizes less than E13, the test core shall be placed on a flat
support as shown in Figure 1. The load shall be applied through the loading wedge, and the
load at the instant of fracture recorded.
Dimensions in millimeters
Figure 1 – E test
6.2.2.3 W test
For test core sizes equal to or larger than E13, the test core shall be placed on roller bars as
shown in Figure 2. For test core sizes less than E13, the test core shall be placed on a flat
support as shown in Figure 2. The load shall be applied through the loading wedge, and the
load at the instant of fracture recorded.
Dimensions in millimeters
Figure 2 – W test
– 10 – IEC 61631:2020 RLV © IEC 2020
6.2.2.4 T test
The test core shall be placed as shown in Figure 3. For test core sizes equal to or larger than
E32, the load shall be applied to the core legs from the roller bars as shown in Figure 3. For
test core sizes less than E32, the load shall be applied through jigs, which shall be agreed
between the parties concerned, and the load at the instant of fracture recorded.
Dimensions in millimeters
Figure 3 – T test
6.2.2.5 M test
For test core sizes equal to or larger than E13, the test core shall be placed on roller bars as
shown in Figure 4. For test core sizes less than E13, the test core shall be placed on a flat
support as shown in Figure 4. The load shall be applied through the loading wedge, and the
load at the instant of fracture recorded.
Dimensions in millimeters
Figure 4 – M test
6.2.3 I-test Test of I-cores
For test core sizes equal to or larger than I13, the test core shall be placed on roller bars as
shown in Figure 5. For test core sizes less than I13, the test core shall be placed on a flat
support as shown in Figure 5. The load shall be applied through the loading wedge, and the
load at the instant of fracture recorded.
Dimensions in millimeters
Figure 5 – I test
6.2.4 Test of ring-cores
6.2.4.1 Dimensions
The specifications and dimensions of ring-cores are according to IEC 63093-12. For standard
dimensions of ring-cores and methods for strength test see Annex B.
6.2.4.2 Ring test
6.2.4.2.1 General
There are three methods for testing the strength of ring-cores. The method shall be selected
as agreed between the parties concerned. The load shall be applied through the loading
wedge, and the load at the instant of fracture shall be recorded.
6.2.4.2.2 Stretching method
For the stretching method, see Figure 6.
Dimensions in millimeters
Figure 6 – Stretching method
– 12 – IEC 61631:2020 RLV © IEC 2020
6.2.4.2.3 Shearing method
For the shearing method, see Figure 7.
Dimensions in millimeters
Figure 7 –Shearing method
6.2.4.2.4 Pressure method
For the pressure method, see Figure 8.
Figure 8 – Pressure method
Annex A
(normative)
Standard dimensions of E-cores and their support for strength test
A.1 Introduction General
Annex A gives standard dimensions of E-cores specified in IEC 61246 IEC 63093-8 and the
type of core support for mechanical strength testing. The nominal dimensions of L and H are
calculated from the nominal values of (B and F D) and (A and E) respectively and are rounded
off to the first decimal place.
A.2 Designation
For the designation of an E-core, see Figure A.1.
Figure A.1 – Designation of E-core
A.3 Test core support
The type of test core support is described in Table A.1.
– 14 – IEC 61631:2020 RLV © IEC 2020
Table A.1 – Test core support
Parameter Core size
E5.3/2 E6.3/2 E8/2 E8.8/2 E10/3 E13/4 E16/5 E20/6 E25/7 E32/9 E42/15 E42/20 E55/21 E55/25 E65/27
A Max. 5,30 6,30 8,15 9,40 10,20 13,10 16,70 20,80 25,80 32,90 43,00 43,00 56,20 56,20 66,50
Min. 5,20 6,05 7,85 8,60 9,80 12,20 15,50 19,40 24,30 31,30 41,30 41,30 54,10 54,10 63,80
B Max. 2,70 2,90 4,05 4,10 5,00 6,50 8,20 10,20 12,80 16,40 21,20 21,20 27,80 27,80 32,80
Min. 2,60 2,80 3,95 3,90 4,88 6,30 7,90 9,80 12,30 15,80 20,80 20,80 27,20 27,20 32,20
C Max. 2,00 2,00 2,40 2,00 3,00 3,70 4,70 5,90 7,50 9,50 15,20 20,00 21,00 25,00 27,40
Min. 1,90 1,90 2,30 1,80 2,88 3,40 4,30 5,40 6,90 8,80 14,70 19,20 20,40 24,20 26,60
D Max. 1,40 1,40 2,40 2,02 3,00 3,70 4,70 5,90 7,50 9,50 12,20 12,20 17,20 17,20 20,00
Min. 1,30 1,30 2,30 1,78 2,88 3,40 4,40 5,50 7,00 8,90 11,70 11,70 16,70 16,70 19,30
E Max. 4,00 3,80 5,80 5,33 7,30 9,50 11,90 14,70 18,30 23,70 30,70 30,70 38,70 38,70 45,70
Min. 3,90 3,60 5,60 5,07 7,00 8,90 11,30 14,10 17,50 22,70 29,50 29,50 37,50 37,50 44,20
F Max. 2,10 1,95 2,90 2,35 3,62 4,80 6,10 7,40 9,20 11,80 15,50 15,50 19,30 19,30 23,00
Min. 2,00 1,85 2,80 2,03 3,50 4,50 5,70 7,00 8,70 11,20 14,80 14,80 18,50 18,50 22,20
L Nom. 0,3 0,5 0,6 0,9 0,7 0,9 1,1 1,4 1,8 2,3 2,9 2,9 4,3 4,3 5,0
H Nom. 0,3 0,6 0,6 1,0 0,7 0,9 1,1 1,4 1,8 2,2 3,0 3,0 4,3 4,3 5,0
1 3
E-mode a a a a a R R R R R R R R R R
Test core M-mode a a a a a R R R R R R R R R R
support
W-mode a a a a a R R R R R R R R R R
T-mode b b b b b b b b b R R R R R R
a: Flat support used.
b: Jigs used, which shall be agreed between the parties concerned.
R: Roller bars used.
The tolerance
...
IEC 61631 ®
Edition 2.0 2020-05
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Test method for the mechanical strength of cores made of magnetic oxides
Méthode d'essai pour la résistance mécanique des noyaux en oxydes
magnétiques
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About the IEC
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International Standards for all electrical, electronic and related technologies.
About IEC publications
The technical content of IEC publications is kept under constant review by the IEC. Please make sure that you have the
latest edition, a corrigendum or an amendment might have been published.
IEC publications search - webstore.iec.ch/advsearchform Electropedia - www.electropedia.org
The advanced search enables to find IEC publications by a The world's leading online dictionary on electrotechnology,
variety of criteria (reference number, text, technical containing more than 22 000 terminological entries in English
committee,…). It also gives information on projects, replaced and French, with equivalent terms in 16 additional languages.
and withdrawn publications. Also known as the International Electrotechnical Vocabulary
(IEV) online.
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once a month by email. French extracted from the Terms and Definitions clause of
IEC publications issued since 2002. Some entries have been
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IEC 61631 ®
Edition 2.0 2020-05
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Test method for the mechanical strength of cores made of magnetic oxides
Méthode d'essai pour la résistance mécanique des noyaux en oxydes
magnétiques
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 29.100.10 ISBN 978-2-8322-9051-4
– 2 – IEC 61631:2020 © IEC 2020
CONTENTS
FOREWORD . 3
INTRODUCTION . 5
1 Scope . 6
2 Normative references . 6
3 Terms and definitions . 6
4 Apparatus . 6
4.1 Test core support and loading wedge . 6
4.2 Testing device . 7
4.3 Humidity measuring device . 7
5 Test cores . 7
5.1 General . 7
5.2 Number of test cores . 7
5.3 Precautions . 7
6 Testing . 7
6.1 Test conditions . 7
6.2 Test procedures . 7
6.2.1 General . 7
6.2.2 Test of E-cores . 8
6.2.3 Test of I-cores . 10
6.2.4 Test of ring-cores . 10
Annex A (normative) Standard dimensions of E-cores and their support
for strength test . 13
A.1 General . 13
A.2 Designation . 13
A.3 Test core support . 13
Annex B (normative) Standard dimensions of ring-cores and methods for strength test . 15
B.1 General . 15
B.2 Selection of mechanical strength test method for ring-core . 15
Bibliography . 16
Figure 1 – E test . 8
Figure 2 – W test . 9
Figure 3 – T test . 9
Figure 4 – M test . 10
Figure 5 – I test . 10
Figure 6 – Stretching method . 11
Figure 7 – Shearing method . 12
Figure 8 – Pressure method . 12
Figure A.1 – Designation of E-core . 13
Figure B.1 – Dimensions of ring-core . 15
Table A.1 – Test core support . 14
Table B.1 – Ring-core dimension designations . 15
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
TEST METHOD FOR THE MECHANICAL STRENGTH
OF CORES MADE OF MAGNETIC OXIDES
FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of 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, IEC publishes International Standards, Technical Specifications,
Technical Reports, Publicly Available Specifications (PAS) and Guides (hereafter referred to as "IEC
Publication(s)"). 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. 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 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 IEC National Committees.
3) IEC Publications have the form of recommendations for international use and are accepted by IEC National
Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC
Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any
misinterpretation by any end user.
4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications
transparently to the maximum extent possible in their national and regional publications. Any divergence
between any IEC Publication and the corresponding national or regional publication shall be clearly indicated in
the latter.
5) IEC itself does not provide any attestation of conformity. Independent certification bodies provide conformity
assessment services and, in some areas, access to IEC marks of conformity. IEC is not responsible for any
services carried out by independent certification bodies.
6) All users should ensure that they have the latest edition of this publication.
7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and
members of its technical committees and IEC National Committees for any personal injury, property damage or
other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and
expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC
Publications.
8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
indispensable for the correct application of this publication.
9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of
patent rights. IEC shall not be held responsible for identifying any or all such patent rights.
International Standard IEC 61631 has been prepared by IEC technical committee 51:
Magnetic components, ferrite and magnetic powder materials.
This second edition cancels and replaces the first edition published in 2001. This edition
constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
a) the phrase: "This document is also applicable to the mechanical strength measurement of
magnetic powder cores" has been added in the scope;
b) IEC 61246 has been replaced by IEC 63093-8; EN 1002-2 has been replaced by
ISO 7500-1; ISO 4677-1 and ISO 4677-2 have been withdrawn;
c) dimensions D and F in Figure A.1 and Table A.1 have been changed to be consistent with
Figure 1 of IEC 63093-8:2018;
d) addition of the content of ring-cores test;
e) addition of Annex B;
– 4 – IEC 61631:2020 © IEC 2020
f) the location of the jig is amended in Figure 3;
g) in Figure 5, the roller bars are moved to the edge of the I-core, aligned with the core.
The text of this International Standard is based on the following documents:
CDV Report on voting
51/1312/CDV 51/1333/RVC
Full information on the voting for the approval of this International Standard can be found in
the report on voting indicated in the above table.
This document has been drafted in accordance with the ISO/IEC Directives, Part 2.
The committee has decided that the contents of this document will remain unchanged until the
stability date indicated on the IEC website under "http://webstore.iec.ch" in the data related to
the specific document. At this date, the document will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
INTRODUCTION
The method specified in this document is intended to be used for obtaining agreements
between parties for material development, quality checking, characterization and data
acquisition purposes. The method places closely defined restrictions on the arrangement of
the test-piece and the function of the test apparatus, including the test-jigs, in order to
minimize the errors that can arise as a consequence of the test method.
All other factors are stated in the test report for comparison of the behavior of the magnetic
oxide cores. It is not possible to rigorously standardize particular surface finishes, since it is
difficult to control all the mechanical factors. But the state of the surface in the report should
be mentioned, as surface defects can have a large effect on mechanical strength in certain
types of tests (see Clause 6). The extrapolation of mechanical strength data to other
geometries, multi-axial stressing, other rates of stressing or other environmental conditions,
should be viewed with caution. The origin of a fracture in a mechanical test piece can be a
valuable guide to the nature and position of strength-limiting defects (such as pores, large
grains and impurity concentration).
The results of strength tests are influenced by a combination of the following factors: the
microstructure of the material, the surface finishing procedure applied to the test cores, the
size and shape of the test cores, the mechanical parameters of the testing apparatus, the rate
of load application and the relative humidity of the ambient atmosphere. Because of the
ceramic nature of magnetic oxide cores, a considerable range of results is usually obtained
from a number of nominally identical test cores. Thus test results are interpreted with caution.
– 6 – IEC 61631:2020 © IEC 2020
TEST METHOD FOR THE MECHANICAL STRENGTH
OF CORES MADE OF MAGNETIC OXIDES
1 Scope
This document specifies a test method for the mechanical strength of cores made of magnetic
oxides. This test method is suitable for most of the E-cores, ETD-cores, I-cores and ring-
cores but other core types such as U-cores could be tested according to a derived method
agreed by the parties concerned. This document is also applicable to the mechanical strength
measurement of magnetic powder cores.
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.
ISO 7500-2, Metallic materials – Verification of static uniaxial testing machines – Part 2:
Tension creep testing machines – Verification of the applied force
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following
addresses:
• IEC Electropedia: available at http://www.electropedia.org/
• ISO Online browsing platform: available at http://www.iso.org/obp
3.1
mechanical strength
maximum recorded force at the instant of fracture of a magnetic oxide core when it is loaded
with the bending stress
4 Apparatus
4.1 Test core support and loading wedge
Test cores shall be supported on free moving roller bars or on a flat support depending on
their size (see 6.2). The loading wedge, the roller bars and the stretch bar or the flat support
shall be made of hardened steel with a hardness of 40 HRC (HRC is Rockwell hardness) to
60 HRC. The loading wedge and the roller bars shall have a radius of 2 mm. The radius of the
contact part of the stretching rod head and the measured core is 2 mm. The loading wedge
and the stretch bar shall be connected to a device for measuring and recording the load
applied.
4.2 Testing device
The testing device shall be a mechanical testing machine capable of applying a force to the
loading wedge high enough to break the test core. The machine shall be capable of applying
the force at a constant loading rate. The machine shall be equipped with a device for
recording the peak load applied to the test core. The accuracy of the machine shall be 1 % of
the indicated load. The force calibration of the machine shall be checked in accordance with
ISO 7500-2.
4.3 Humidity measuring device
A humidity measuring device, such as, but not limited to, an aspirated psychrometer or
whirling psychrometer that is capable of measuring relative humidity to an accuracy of ±2 %
shall be used.
5 Test cores
5.1 General
The test cores shall be selected as agreed between the parties concerned. They may be
machined to the specified dimensions, because any machined surface plays an important role
in the mechanical strength (see the Introduction).
5.2 Number of test cores
For material development, characterization or quality checking, the minimum number of test
cores shall be five pieces. For statistical evaluation of strength data (for example, Weibull
parameters), the minimum number shall be thirty.
For comparison of data for different materials, it is important that the number of specimens is
high enough to obtain results with sufficient statistical confidence. Since the confidence limits,
in general, depend on the number of test results and their dispersion, the number of test
specimens should be decided on the basis of statistical considerations.
5.3 Precautions
The prepared test cores should be handled with care to avoid introduction of additional
damage. Test cores should be kept separately at all times, and should be wrapped
individually for transport.
6 Testing
6.1 Test conditions
The test shall be carried out at an ambient temperature between 15 °C and 35 °C. The
temperature shall not vary by more than 3 °C during the course of a test series. The relative
humidity shall be between 45 % and 85 % and shall not vary by more than 10 % during the
course of a test series.
6.2 Test procedures
6.2.1 General
The test core shall be arranged in the test apparatus in accordance with 6.2.2.2, 6.2.2.3,
6.2.2.4, 6.2.2.5, 6.2.3, 6.2.4.2.2, 6.2.4.2.3 or 6.2.4.2.4 as applicable (see Figure 1 to Figure 8).
For standard dimensions of E-cores and their support for strength test see Annex A.
– 8 – IEC 61631:2020 © IEC 2020
The E test and W test can be used for material-related purposes, while the M test and T test
can be used for process-related purposes. The test of I-cores is only recommended for flat-
shaped test cores such as antenna rods. The test method of stretching, shearing and
pressure is only applicable to ring-cores. A preloading force of 5 N to 25 N shall be applied
because the upper and lower faces of the test cores are never absolutely parallel. The test
force shall then be applied at a loading rate of between 5 mm/min and 20 mm/min until the
test core fractures. The load at the instant of fracture shall be recorded. The fractured
fragments shall be identified and preserved for later fractographic examination.
6.2.2 Test of E-cores
6.2.2.1 Dimensions
The specifications and dimensions of E-cores are according to IEC 63093-8.
6.2.2.2 E test
For test core sizes equal to or larger than E13, the test core shall be placed on roller bars as
shown in Figure 1. For test core sizes less than E13, the test core shall be placed on a flat
support as shown in Figure 1. The load shall be applied through the loading wedge, and the
load at the instant of fracture recorded.
Dimensions in millimeters
Figure 1 – E test
6.2.2.3 W test
For test core sizes equal to or larger than E13, the test core shall be placed on roller bars as
shown in Figure 2. For test core sizes less than E13, the test core shall be placed on a flat
support as shown in Figure 2. The load shall be applied through the loading wedge, and the
load at the instant of fracture recorded.
Dimensions in millimeters
Figure 2 – W test
6.2.2.4 T test
The test core shall be placed as shown in Figure 3. For test core sizes equal to or larger than
E32, the load shall be applied to the core legs from the roller bars as shown in Figure 3. For
test core sizes less than E32, the load shall be applied through jigs, which shall be agreed
between the parties concerned, and the load at the instant of fracture recorded.
Dimensions in millimeters
Figure 3 – T test
6.2.2.5 M test
For test core sizes equal to or larger than E13, the test core shall be placed on roller bars as
shown in Figure 4. For test core sizes less than E13, the test core shall be placed on a flat
support as shown in Figure 4. The load shall be applied through the loading wedge, and the
load at the instant of fracture recorded.
– 10 – IEC 61631:2020 © IEC 2020
Dimensions in millimeters
Figure 4 – M test
6.2.3 Test of I-cores
For test core sizes equal to or larger than I13, the test core shall be placed on roller bars as
shown in Figure 5. For test core sizes less than I13, the test core shall be placed on a flat
support as shown in Figure 5. The load shall be applied through the loading wedge, and the
load at the instant of fracture recorded.
Dimensions in millimeters
Figure 5 – I test
6.2.4 Test of ring-cores
6.2.4.1 Dimensions
The specifications and dimensions of ring-cores are according to IEC 63093-12. For standard
dimensions of ring-cores and methods for strength test see Annex B.
6.2.4.2 Ring test
6.2.4.2.1 General
There are three methods for testing the strength of ring-cores. The method shall be selected
as agreed between the parties concerned. The load shall be applied through the loading
wedge, and the load at the instant of fracture shall be recorded.
6.2.4.2.2 Stretching method
For the stretching method, see Figure 6.
Dimensions in millimeters
Figure 6 – Stretching method
6.2.4.2.3 Shearing method
For the shearing method, see Figure 7.
– 12 – IEC 61631:2020 © IEC 2020
Dimensions in millimeters
Figure 7 – Shearing method
6.2.4.2.4 Pressure method
For the pressure method, see Figure 8.
Figure 8 – Pressure method
Annex A
(normative)
Standard dimensions of E-cores and their support for strength test
A.1 General
Annex A gives standard dimensions of E-cores specified in IEC 63093-8 and the type of core
support for mechanical strength testing. The nominal dimensions of L and H are calculated
from the nominal values of (B and D) and (A and E) respectively and are rounded off to the
first decimal place.
A.2 Designation
For the designation of an E-core, see Figure A.1.
Figure A.1 – Designation of E-core
A.3 Test core support
The type of test core support is described in Table A.1.
– 14 – IEC 61631:2020 © IEC 2020
Table A.1 – Test core support
Dimensions in millimeters
Core size
Parameter
E5,3/2 E6,3/2 E8/2 E8,8/2 E10/3 E13/4 E16/5 E20/6 E25/7 E32/9 E42/15 E42/20 E55/21 E55/25 E65/27
Max. 5,35 6,30 8,15 9,40 10,20 13,10 16,70 20,80 25,80 32,90 43,00 43,00 56,20 56,20 66,50
A
Min. 5,15 6,05 7,85 8,60 9,80 12,20 15,50 19,40 24,30 31,30 41,30 41,30 54,10 54,10 63,80
Max. 2,73 2,90 4,05 4,15 5,00 6,50 8,20 10,20 12,80 16,40 21,20 21,20 27,80 27,80 32,80
B
Min. 2,57 2,80 3,95 3,85 4,88 6,30 7,90 9,80 12,30 15,80 20,80 20,80 27,20 27,20 32,20
Max. 2,00 2,00 2,40 2,02 3,00 3,70 4,70 5,90 7,50 9,50 15,20 20,00 21,00 25,00 27,40
C
Min. 1,90 1,90 2,30 1,78 2,88 3,40 4,30 5,40 6,90 8,80 14,70 19,20 20,40 24,20 26,60
Max. 1,92 2,05 2,95 2,40 3,62 4,80 6,10 7,40 9,20 11,80 15,50 15,50 19,30 19,30 23,00
D
Min. 2,08 1,85 2,85 2,03 3,50 4,50 5,70 7,00 8,70 11,20 14,80 14,80 18,50 18,50 22,20
Max. 4,00 3,80 5,80 5,33 7,30 9,50 11,90 14,70 18,30 23,70 30,70 30,70 38,70 38,70 45,70
E
Min. 3,80 3,60 5,60 5,07 7,00 8,90 11,30 14,10 17,50 22,70 29,50 29,50 37,50 37,50 44,20
Max. 1,40 1,40 2,40 2,02 3,00 3,70 4,70 5,90 7,50 9,50 12,20 12,20 17,20 17,20 20,00
F
Min. 1,30 1,30 2,30 1,78 2,88 3,40 4,40 5,50 7,00 8,90 11,70 11,70 16,70 16,70 19,30
d
L Nom. 0,3 0,5 0,6 0,9 0,7 0,9 1,1 1,4 1,8 2,3 2,9 2,9 4,3 4,3 5,0
d
H Nom. 0,3 0,6 0,6 1,0 0,7 0,9 1,1 1,4 1,8 2,2 3,0 3,0 4,3 4,3 5,0
a c
E-mode A a a a a R R R R R R R R R R
M-mode a a a a a R R R R R R R R R R
Test core support
W-mode a a a a a R R R R R R R R R R
b
T-mode B b b b b b b b b R R R R R R
a
Flat support is used.
b
Ji
...
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