SIST EN 60793-1-33:2018

SLOVENSKI STANDARD
01-januar-2018
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SIST EN 60793-1-33:2004
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Optical fibres - Part 1-33: Measurement methods and test procedures - Stress corrosion
susceptibility (IEC 60793-1-33:2017)
Lichtwellenleiter - Teil 1-33: Messmethoden und Prüfverfahren -
Spannungskorrosionsempfindlichkeit (IEC 60793-1-33:2017)
Fibres optiques - Partie 1-33: Méthodes de mesure et procédures d'essai - Résistance à
la corrosion sous contrainte (IEC 60793-1-33:2017)
Ta slovenski standard je istoveten z: EN 60793-1-33:2017
ICS:
33.180.10 2SWLþQDYODNQDLQNDEOL Fibres and cables
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EUROPEAN STANDARD EN 60793-1-33

NORME EUROPÉENNE
EUROPÄISCHE NORM
November 2017
ICS 33.180.10 Supersedes EN 60793-1-33:2002
English Version
Optical fibres - Part 1-33: Measurement methods and test
procedures - Stress corrosion susceptibility
(IEC 60793-1-33:2017)
Fibres optiques - Partie 1-33: Méthodes de mesure et Lichtwellenleiter - Teil 1-33: Messmethoden und
procédures d'essai - Résistance à la corrosion sous Prüfverfahren - Spannungskorrosionsempfindlichkeit
contrainte (IEC 60793-1-33:2017)
(IEC 60793-1-33:2017)
This European Standard was approved by CENELEC on 2017-09-20. CENELEC 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.
Up-to-date lists and bibliographical references concerning such national standards may be obtained on application to the CEN-CENELEC
Management Centre or to any CENELEC member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by translation
under the responsibility of a CENELEC member into its own language and notified to the CEN-CENELEC Management Centre has the
same status as the official versions.
CENELEC members are the national electrotechnical committees of Austria, Belgium, Bulgaria, Croatia, Cyprus, the Czech Republic,
Denmark, Estonia, Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia,
Lithuania, Luxembourg, Malta, the Netherlands, Norway, Poland, Portugal, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden,
Switzerland, Turkey and the United Kingdom.

European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung
CEN-CENELEC Management Centre: Avenue Marnix 17, B-1000 Brussels
© 2017 CENELEC All rights of exploitation in any form and by any means reserved worldwide for CENELEC Members.
Ref. No. EN 60793-1-33:2017 E
European foreword
The text of document 86A/1803/FDIS, future edition 1 of IEC 60793-1-33:2017, prepared by
IEC/SC 86A "Fibres and cables", of IEC/TC 86 "Fibre optics" was submitted to the IEC-CENELEC
parallel vote and approved by CENELEC as EN 60793-1-33:2017.
The following dates are fixed:

• latest date by which this document has (dop) 2018-06-20
to be implemented at national level by
publication of an identical national
standard or by endorsement
• latest date by which the national (dow) 2020-09-20
standards conflicting with this
document have to be withdrawn
This document supersedes EN 60793-1-33:2002.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CENELEC shall not be held responsible for identifying any or all such patent rights.

Endorsement notice
The text of the International Standard IEC 60793-1-33:2017 was approved by CENELEC as a
European Standard without any modification.
IEC 60793-1-33 ®
Edition 2.0 2017-08
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Optical fibres –
Part 1-33: Measurement methods and test procedures – Stress corrosion

susceptibility
Fibres optiques –
Partie 1-33: Méthodes de mesures et procédures d'essai – Résistance à la

corrosion sous contrainte
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 33.180.10 ISBN 978-2-8322-4736-5

– 2 – IEC 60793-1-33:2017 © IEC 2017
CONTENTS
FOREWORD . 5
INTRODUCTION . 7
1 Scope . 8
2 Normative references . 8
3 Terms and definitions . 8
4 Overview of test methods . 9
5 Reference test methods . 9
6 Apparatus . 9
7 Sampling and specimens . 9
7.1 General . 9
7.2 Specimen length . 9
7.3 Specimen preparation and conditioning . 9
8 Procedure . 10
9 Calculations . 10
10 Results . 10
11 Specification information . 11
Annex A (normative) Dynamic n value, n , by axial tension . 12
d
A.1 General . 12
A.2 Apparatus . 12
A.2.1 General . 12
A.2.2 Support of the specimen . 13
A.2.3 Stressing application . 14
A.2.4 Fracture force measurement . 14
A.2.5 Strain rate control . 14
A.2.6 Stress rate characterization . 15
A.3 Test sample . 15
A.3.1 Sample size . 15
A.3.2 Sample size (optional) . 15
A.4 Procedure . 15
A.5 Calculations . 16
A.5.1 Fracture stress . 16
A.5.2 Fracture stress at a given strain rate . 16
A.5.3 Dynamic (tension) stress corrosion susceptibility parameter, n . 17
d
A.6 Results . 17
Annex B (normative) Dynamic n value, n , by two-point bending . 19
d
B.1 General . 19
B.2 Apparatus . 19
B.2.1 General . 19
B.2.2 Stepper motor control . 19
B.2.3 Stepper motor-driven movable platen . 19
B.2.4 Stationary platen . 19
B.2.5 Platen velocity . 19
B.2.6 Fibre fracture detecting system . 19
B.3 Test sample . 20
B.4 Procedure . 20

IEC 60793-1-33:2017 © IEC 2017 – 3 –
B.5 Calculations . 21
B.5.1 Fracture stress . 21
B.5.2 Dynamic (two-point bending) stress corrosion susceptibility parameter,
n . 21
d
B.5.3 Results . 22
Annex C (normative) Static n value, n , by axial tension . 24
s
C.1 General . 24
C.2 Apparatus . 24
C.2.1 General . 24
C.2.2 Gripping the fibre at both ends. 24
C.2.3 Stressing the fibre . 24
C.2.4 Measuring time to fracture . 24
C.3 Test sample . 24
C.4 Procedure . 24
C.5 Calculations . 25
C.5.1 Fracture stress . 25
C.5.2 Static (tension) stress corrosion susceptibility parameter, n . 25
s
C.5.3 Simple median . 25
C.6 Results . 25
Annex D (normative) Static n value, n , by two-point bending . 27
s
D.1 General . 27
D.2 Apparatus . 27
D.2.1 Test equipment . 27
D.2.2 Fibre fracture detection . 27
D.3 Test sample . 27
D.4 Procedure . 27
D.5 Calculations . 27
D.5.1 Fracture stress . 27
D.5.2 Static (two-point bending) stress corrosion susceptibility parameter, n . 28
s
D.6 Results . 28
Annex E (normative) Static n value, n , by uniform bending . 29
s
E.1 General . 29
E.2 Apparatus . 29
E.2.1 General . 29
E.2.2 Support of the sample . 29
E.2.3 Stressing the fibre . 29
E.2.4 Measuring time to fracture . 29
E.3 Test sample . 29
E.4 Procedure . 29
E.5 Calculations . 30
E.5.1 Fracture stress . 30
E.5.2 Static (uniform bending) stress corrosion susceptibility parameter, n . 30
s
E.6 Results . 30
Annex F (informative) Considerations for dynamic stress corrosion susceptibility
parameter calculations . 31
F.1 Specimen size and sample size . 31
F.1.1 Specimen size . 31
F.1.2 Sample size . 31

– 4 – IEC 60793-1-33:2017 © IEC 2017
F.2 Numeric algorithm for calculation of dynamic stress corrosion susceptibility
parameter, n . 32
d
F.3 Complete method to calculate fracture stress . 33
Annex G (informative) Considerations for static stress corrosion susceptibility
parameter calculations . 35
G.1 Homologous method . 35
G.2 Maximum likelihood estimate . 35
Annex H (informative) Considerations on stress corrosion susceptibility parameter test
methods . 36
H.1 General . 36
H.2 Crack growth . 36
H.3 Types of stress corrosion susceptibility test methods . 37
H.4 Comparison of n value obtained with different methods . 37
H.5 Conclusion . 38
Bibliography . 40

Figure A.1 – Schematic of translation test apparatus . 12
Figure A.2 – Schematic of rotational test apparatus . 13
Figure A.3 – Schematic of rotational test apparatus with load cell . 13
Figure A.4 – Representation of dynamic fatigue graph . 18
Figure B.1 – Schematic of two-point bending unit. 22
Figure B.2 – Schematic of possible dynamic fatigue (two-point bending) apparatus . 23
Figure B.3 – Schematic of dynamic fatigue data . 23
Figure C.1 – Schematic of possible static fatigue (tension) apparatus . 26
Figure D.1 – Possible test equipment schematic . 28
Figure E.1 – Schematic of possible static fatigue (uniform bending) apparatus . 30
Figure H.1 – COST 218 round robin results of fracture strength versus "effective" time-
to-fracture for dynamic and static axial tension, dynamic and static two-point bending
and static mandrel test methods . 38
Figure H.2 – COST 218 round robin results of fracture strength versus "effective" time-
to-fracture for dynamic and static axial tension, dynamic and static two-point bending
and static mandrel test methods . 39

Table F.1 – 95 % confidence interval for n . 32
d
IEC 60793-1-33:2017 © IEC 2017 – 5 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
OPTICAL FIBRES –
Part 1-33: Measurement methods and test procedures –
Stress corrosion susceptibility

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
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in the subject dealt with may participate in this preparatory work. International, governmental and non-
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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
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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 60793-1-33 has been prepared by subcommittee 86A: Fibres and
cables, of IEC technical committee 86: Fibre optics.
This second edition cancels and replaces the first edition published in 2001. It constitutes a
technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
a) removal of RTM;
b) changes to scope.
– 6 – IEC 60793-1-33:2017 © IEC 2017
The text of this International Standard is based on the following documents:
FDIS Report on voting
86A/1803/FDIS 86A/1824/RVD
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.
A list of all parts of the IEC 60793 series, published under the general title Optical fibres, can
be found on the IEC website.
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.
IEC 60793-1-33:2017 © IEC 2017 – 7 –
INTRODUCTION
Annexes A, B, C, D, and E form an integral part of this document.
Annexes F, G, and H are for information only.

– 8 – IEC 60793-1-33:2017 © IEC 2017
OPTICAL FIBRES –
Part 1-33: Measurement methods and test procedures –
Stress corrosion susceptibility

1 Scope
This part of IEC 60793 contains descriptions of the five main test methods for the
determination of stress corrosion susceptibility parameters.
The object of this document is to establish uniform requirements for the mechanical
characteristic of stress corrosion susceptibility for silica-based fibres. Dynamic fatigue and
static fatigue tests are used to determine the (dynamic) n value and (static) n value of stress
d s
corrosion susceptibility parameters. Currently, only the n -value is assessed against
d
specification. Measured values greater than 18 per this procedure reflect the n -value of
d
silica, which is approximately 20. Higher values will not translate to demonstrable enhanced
fatigue resistance.
Silica fibre mechanical tests determine the fracture stress and fatigue properties under
conditions that model the practical applications as closely as possible. The following test
methods are used for determining stress corrosion susceptibility:
– A: Dynamic n value by axial tension;
d
– B: Dynamic n value by two-point bending;
d
– C: Static n value by axial tension;
s
– D: Static n value by two-point bending;
s
– E: Static n value by uniform bending.
s
These methods are appropriate for category A1, A2 and A3 multimode, class B single-mode
fibres and class C intraconnecting single-mode fibres.
These tests provide values of the stress corrosion parameter, n, that can be used for reliability
calculations according to IEC TR 62048 [18] .
Information common to all methods is contained in Clauses 1 to 10, and information pertaining
to each individual test method appears in Annexes A, B, C, D, and E.
Annexes F and G offer considerations for dynamic and static stress corrosion susceptibility
parameter calculations, respectively; Annex H offers considerations on the different stress
corrosion susceptibility parameter test methods.
2 Normative references
There are no normative references in this document.
3 Terms and definitions
No terms and definitions are listed in this document.
___________
Numbers in square brackets refer to the Bibliography.

IEC 60793-1-33:2017 © IEC 2017 – 9 –
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
4 Overview of test methods
The following test methods are available:
– Dynamic n value by axial tension, see Annex A.
d
– Dynamic n value by two-point bending, see Annex B.
d
– Static n value by axial tension, see Annex C.
s
– Static n value by two-point bending, see Annex D.
s
– Static n value by uniform bending, see Annex E.
s
5 Reference test methods
At the time of this revision, no agreement could be reached in maintaining method A only as
RTM in using it with some fibres equipped with modern coatings. Method A or B should be
used to resolve disputes because they may be completed in a duration practical for dispute
resolution.
6 Apparatus
See Annexes A, B, C, D, and E for each of the layout drawings and other equipment
requirements for each of the methods.
7 Sampling and specimens
7.1 General
These measurements are statistical in nature. A number of specimens or samples from a
common population are tested, each under several conditions.
Failure stress or time statistics for various sampling groups are used to calculate the stress
corrosion susceptibility parameters.
7.2 Specimen length
Specimen length is contingent on the test procedure used. See Annexes A, B, C, D, and E for
the length required for each test method. For tensile tests, the length ranges from 0,5 m to at
most 5 m. For two-point bending tests, the actual length tested is less than 1 cm and for
uniform bending tests, about 1 m.
7.3 Specimen preparation and conditioning
All of the test methods shall be performed under constant environmental conditions. Unless
otherwise specified in the detail specification, the nominal temperature shall be in the range of
20 °C to 23 °C with a tolerance of ±2 °C for the duration of the test. Unless otherwise
specified in the detail specification, the nominal relative humidity (RH) shall be in the range of
40 % to 60 % with a tolerance of ±5 % for the duration of the test.
Unless otherwise specified, all specimens shall be pre-conditioned in the test environment for
a minimum period of 12 h.
– 10 – IEC 60793-1-33:2017 © IEC 2017
A method for extrapolating such stress corrosion susceptibility parameters to service
environments different from the default environment specified above has not been developed.
It has been observed that the value of n produced by these tests can change after even brief
exposure of the fibre to elevated temperature and humidity. A guide for the use of these
methods is documented in IEC TR 62048 [18].
The observed value of stress corrosion susceptibility parameter, n, may differ between fatigue
test methods, if not performed in the same effective measuring time and effective glass area
under test (see Annex H). Care should be taken in the choice of test method. This should be
agreed between the customer and supplier.
8 Procedure
See Annexes A, B, C, D, and E for the individual test methods.
Each of several samples (consisting of a number of specimens) is exposed to one of a
number of stress conditions. For static fatigue tests, a constant stress is applied from sample
to sample and time to failure is measured. For dynamic fatigue tests, the stress rate is varied
from sample to sample, and the failure stress is measured.
The following is an overview of the procedures common to all methods:
– complete pre-conditioning;
– divide the specimens into sample groups;
– apply the specified stress conditions to each sample group;
– measure time or stress at failure;
– complete calculations.
9 Calculations
The calculations for each individual test method are found in Annexes A, B, C, D, and E.
10 Results
The following information shall be reported with each test:
– fibre identification;
– test date;
– stress corrosion susceptibility parameter;
– test method.
The following information shall be provided upon request:
– specific information as required by the test method;
– relative humidity and ambient temperature;
– any special pre-conditioning.
Clauses A.5, B.5, C.5, D.5, and E.5 have results that apply to each specific method.

IEC 60793-1-33:2017 © IEC 2017 – 11 –
11 Specification information
The detail specification shall specify the following information:
– information to be reported;
– any deviations to the procedure that apply;
– failure or acceptance criteria.

– 12 – IEC 60793-1-33:2017 © IEC 2017
Annex A
(normative)
Dynamic n value, n , by axial tension
d
A.1 General
This method is designed for determining the dynamic stress corrosion susceptibility parameter
(dynamic n value, n ) of optical silica-based fibre at specified constant strain rates.
d
This method is intended only to be used for those optical fibres of which the median fracture
stress is greater than 3 GPa at the highest specified strain rate. For fibres with median
fracture stress less than 3 GPa, the conditions herein have not demonstrated sufficient
precision.
This method is intended to test fatigue behaviour of fibres by varying the strain rate. The test
is applicable to fibres and strain rates for which the logarithm of fracture stress versus the
logarithm of strain rate behaviour is linear.
A.2 Apparatus
A.2.1 General
Clause A.2 describes the fundamental requirements of the equipment used for dynamic
fracture stress testing. There are several configurations that meet these requirements.
Examples are presented in Figures A.1 to A.3. Unless otherwise specified in the detail
specification, use a gauge length of 500 mm for tensile test specimens.
To load cell
Load cell
Capstan diameter
(50 mm minimum)
Fibre holders
(capstans)
Fibre
Speed-control
device
Variable drive
Motor
To cross head
IEC
Figure A.1 – Schematic of translation test apparatus
Gauge length
(50 mm minimum)
IEC 60793-1-33:2017 © IEC 2017 – 13 –

Fibre
Non-rotating capstan
Rotating capstan with rotating sensor

IEC
Figure A.2 – Schematic of rotational test apparatus
Load cell
Fibre
Vertical non-rotating
capstan
Rotating capstan
IEC
Figure A.3 – Schematic of rotational test apparatus with load cell
A.2.2 Support of the specimen
Grip the fibre length to be tested at both ends and subject the fibre to tension until fracture
occurs in the gauge length section of the fibre. Minimize the fibre fracture at the grip – a
sensitive aspect of this method – by providing a surface friction that prevents excessive
slippage.
Do not include breaks that occur at the grip in the sample or use them in the calculations.
Use a capstan, optionally covered with an elastomeric sheath, to grip the fibre. Wrap a
section of the fibre that will not be tested around the capstan several times and secure it at
the end with, for example, an elastic band or masking tape. Apply sufficient fibre length at the
grip in order to avoid slippage inside the coating (coating type depending aspect [19]). Wrap
the fibre with no crossovers. The gauge length is the length of fibre between the axes of the
gripping capstans before it is stretched.

– 14 – IEC 60793-1-33:2017 © IEC 2017
Use a capstan and pulley diameter so that the fibre is not subjected to a bending stress that
causes the fibre to break on the capstan. For typical silica-based fibres, the bending stresses
shall not exceed 175 MPa when the fibre is wrapped as shown in Figures A.1 to A.3 or
traverses a pulley. For example in case of 125 µm cladding diameter silica fibre (200 µm and
250 µm coating diameter), the minimum capstan diameter is then 50 mm. Provide a capstan
surface tough enough that the fibre does not cut into it when fully loaded. This condition can
be determined by pre-testing.
A.2.3 Stressing application
Elongate the fibre at a fixed strain rate until it breaks. The rate of elongation is expressed as
percentage per minute, relative to the gauge length. Two examples are given:
a) increase the separation between the gripping capstans by moving one or both of the
capstans at a fixed rate of speed, with the starting separation equal to the gauge length
(Figure A.1); or
b) rotate one or both of the gripping capstans, to take up the fibre under test (see
Figures A.2 and A.3).
The strain rate is the change in length between the two locations, in per cent, divided by the
time.
If method b) is used, ensure that the fibre on the capstan does not cross over itself as it is
wrapped.
If fibres are tested simultaneously, protect each fibre from adjacent fibres so that whiplash at
fracture does not damage other fibres under test.
A.2.4 Fracture force measurement
Measure the tensile stress during the test and at fracture for each test fibre by a load cell,
calibrated to within 0,5 % (0,005) of the fracture or maximum load, for each range of fracture
stress. Calibrate the load cell while oriented in the same manner as when testing the fibre
under load. For method b), use a light, low-friction pulley (or pulleys) in place of the non-
rotating capstan (see Figure A.2), or the rotating capstan (see Figure A.3), when calibrating
load cells with a string and calibration weight.
Use a string, attached at one end to the load-measuring device (or its capstan), to duplicate
the direction of an actual test fibre with a thickness or diameter comparable to that of a test
fibre. A minimum of three calibration weights are recommended for load cell calibration which
bracket the typical fracture or maximum load (50 % below maximum, maximum and 50 %
above maximum).
The response time of the load-measuring system shall be sufficient to report the fracture
stress within 1 % of the actual value.
NOTE Frictional effects from the pulleys can lead to substantial errors in the load cell calibration of rotating
capstan testers for horizontally mounted fibre.
A.2.5 Strain rate control
Determine the setting for the speed control unit by trial in order to meet the specified strain
rates. Express the strain rate as a percentage of gauge length per unit time. Unless otherwise
specified in the detail specification, the maximum strain rate shall be equal to or less than
100 %/min. Select the actual maximum strain rate by taking into account aspects of the test
method such as equipment considerations and material properties of the samples. In addition
to the maximum rate, use three additional strain rates, each reduced sequentially by roughly a
power of 10 from the maximum.
IEC 60793-1-33:2017 © IEC 2017 – 15 –
It is possible to minimize test duration by using a faster strain rate in conjunction with a
reduced load. For example, if a strain rate of 0,025 %/min is specified, test some specimens
at the next fastest rate (0,25 %/min) to establish a range of fracture stress. Then pre-load to a
level equal to or less than 80 % of the lowest fracture stress found for the initial trial
specimens at the next fastest rate.
A.2.6 Stress rate characterization
The stress rate may vary with fibre type, equipment, breaking stress, fibre slippage, and strain

rate. Characterize the stress rate, , at each strain rate used in the fatigue calculation
σ
a
according to:
0,2 × σ
f
σ = (A.1)
a
t(σ ) − t(0,8 × σ )
f f
where
σ is the fracture stress;
f
t(σ ) is the time to fracture;
f
t(0,8 x σ ) is the time at 80 % of the fracture stress.
f
A.3 Test sample
A.3.1 Sample size
Because of the variability of test results, test a minimum of 15 specimens for each strain rate,
and drop the lowest breaking fracture stress data point for each strain rate. Alternatively, if

the standard error of estimate of slope σ vs. is 0,0017 or greater (as explained in
σ
f a
Clause F.2), test a minimum of 30 specimens for each strain rate and drop the lowest two
breaking fracture stress data points for each strain rate.
A.3.2 Sample size (optional)
As explained in A.3.1, additional specimens may be required for some applications in which
the confidence interval on the estimate of the dynamic (tension) stress corrosion susceptibility
parameter, n , needs to be known. Refer to Table F.1 for various sample sizes, depending
d
upon the expected dynamic Weibull slope, m . Appropriate use of the algorithm in Clause F.2
d
is restricted to tests in which the same sample size is specified for each strain rate.
A.4 Procedure
This procedure describes how to obtain fibre fracture stress on a given sample set tested at a
given strain rate. Calculations of population statistics are presented in Clause F.2.
1) Set and record the gauge length (see A.2.3).
2) Set and record the strain rate (see A.2.5).
3) If method a) of A.2.3 is used, return the gripping capstans to the gauge length separation.
4) Load the test specimen in the grips, one end at a time. The tangent point of the fibre shall
be in the same location as that for the load calibrations. Guide each specimen so that the
fibre makes at least the required number of turns around the capstan without crossing
over itself.
5) If necessary, re-set the load-measuring system.
6) Start the motor to stress the fibre. Record the stress vs. time until the fibre breaks. Stop
the motor.
7) Repeat steps 3) through 6) for all fibres in the sample set.

– 16 – IEC 60793-1-33:2017 © IEC 2017
σ , for each break. Use Equation (A.2).
8) Calculate the fibre fracture stress,
f

9) Calculate the stress rate, . Use Equation (A.1).
σ
a
10) Complete the required population statistic calculations. Use Equations (A.3) to (A.6).
A.5 Calculations
A.5.1 Fracture stress
The following method can be used to calculate the fracture stress, σ , when the coating
f
contribution is negligible (less than 5 %), such as on common 125 µm diameter fibre with a
coated diameter of 250 µm (polymer coating):
σ = T / A (A.2)
f g
where
T is the force (tension) experienced by the composite specimen at fracture;
A is the nominal cross-sectional area of the glass fibre.
g
A more complete method is given in Clause F.3 for use when the coating contribution is
important.
A.5.2 Fracture stress at a given strain rate
The following steps are required to form a Weibull plot characterizing the population.
a) Sort the fracture stresses from minimum to maximum. Assign a rank, k, to each. Rank is
the order, for example first is the weakest, second is the next weakest, etc. Assign a
different rank to each break, even if several breaks have the same fracture stress.
b) Calculate the cumulative probability of failure, F , for each break:
k
F = (k – 0,5)/N,  k = 1, 2, . N (A.3)
k
where
N is the sample size.
c) Graph ln [–ln (1 – F )] vs ln (σ ) to form the Weibull plot.
k f
d) Label the plot with the required information.
e) For a given gauge length and diameter, the dynamic fatigue Weibull plot is associated
with the following cumulative probability function:
md
F = 1 – exp [–(σ /σ ) ] (A.4)
k f o
Let k(P) = P×N + 0,5 define a rank associated with a given probability, P.
th
If k(P) is an integer, let σ (P) = σ (P), the fracture stress of the k(P) rank. If k(P) is not
f fk
an integer, let k be the integer just below k(P) and k = k + 1.
1 2 1
1/2
Then, let σ (P) = (σ σ .
× )
f fk1 fk2
The median fracture stress is σ (0,5). The Weibull slope is:
f
2,46
(A.5)
m =
d
ln [σ (0,85)]− ln [σ (0,15)]
f f
The Weibull parameter is:
IEC 60793-1-33:2017 © IEC 2017 – 17 –
 
0,3665
σ = exp + ln[σ (0,5)]
  (A.6)
o f
m
 d 
Graph the Weibull plot for each stress rate, and determine the median fracture stress σ (0,5)
f
for each stress rate.
A.5.3 Dynamic (tension) stress corrosion susceptibility parameter, n
d
The median fracture stress σ (0,5) as defined in A.5.2, will generally vary with constant stress
...