IEC 61631:2001

INTERNATIONAL IEC
STANDARD
First edition
2001-06
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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INTERNATIONAL IEC
STANDARD
First edition
2001-06
Test method for the mechanical strength
of cores made of magnetic oxides
Méthode d'essai pour la résistance mécanique
des noyaux en oxydes magnétiques

 IEC 2001  Copyright - all rights reserved
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– 2 – 61631  IEC:2001(E)
CONTENTS
FOREWORD . 3

INTRODUCTION .4

1 Scope . 5

2 Normative references . 5

3 Definitions. 5

4 Apparatus . 5
4.1 Test core support and loading wedge . 5
4.2 Testing device. 6
4.3 Humidity measuring device. 6
5 Test cores. 6
5.1 Number of test-cores. 6
5.2 Precautions. 6
6 Testing. 6
6.1 Test conditions. 6
6.2 Test procedures . 6
Annex A (normative) Standard E core dimensions and its support for strength test . 10

61631  IEC:2001(E) – 3 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION

___________
TEST METHOD FOR THE MECHANICAL STRENGTH

OF CORES MADE OF MAGNETIC OXIDES

FOREWORD
1) The IEC (International Electrotechnical Commission) is a worldwide organization for standardization
comprising all national electrotechnical committee (IEC National Committee). 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 responsible for identifying any or all such patent rights.
International Standard IEC 61631 has been prepared by technical committee 51: Magnetic
components and ferrite materials.
The text of this standard is based on the following documents:
FDIS Report on voting
51/599/FDIS 51/610/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.
The committee has decided that the contents of this publication will remain unchanged until
2005. At this date, the publication will be
• reconfirmed;
• withdrawn;
• replaced by a revised edition, or
• amended.
A bilingual version of this publication may be issued at a later date.

– 4 – 61631  IEC:2001(E)
INTRODUCTION
The method specified in this standard 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, 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, to multi-axial stressing, to
other rates of stressing or to 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 micro-
structure 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 interpreted with caution.

61631  IEC:2001(E) – 5 –
TEST METHOD FOR THE MECHANICAL STRENGTH

OF CORES MADE OF MAGNETIC OXIDES

1 Scope
This International Standard 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 and

I-cores but other core types such as U-cores could be tested according to a derived method
agreed by the parties concerned.
2 Normative references
The following normative documents contain provisions which, through reference in this text,
constitute provisions of this International Standard. For dated references, subsequent
amendments to, or revisions of, any of these publications do not apply. However, parties to
agreements based on this International Standard 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 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
3 Definitions
For the purpose of this International Standard, the following definition applies.

3.1
mechanical strength
the maximum recorded force at the instant of fracture of a magnetic oxide core when it is
loaded in bending
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 and the roller bars or the flat support shall be made of
hardened steel with a hardness of 40 HRC to 60 HRC. The loading wedge and the roller bars
shall have a radius of 2 mm. The loading wedge shall be connected to a device for measuring
and recording the load applied.

– 6 – 61631  IEC:2001(E)
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). Force calibration of the machine

shall be checked in accordance with EN 10002-2.

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 %.
5 Test cores
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 Introduction).
5.1 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 (e.g. Weibull parameters),
the minimum number shall be 30.
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.
5.2 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, 6.2.3, 6.2.4,
6.2.5 or 6.2.6 as applicable (see figures 1 to 5).
The E-test and W-test can be used
...