Optical fibres - Part 1-31: Measurement methods and test procedures - Tensile strength

This part of IEC 60793 provides values of the tensile strength under dynamic loading of optical fibre samples. The method tests individual lengths of uncabled and unbundled glass optical fibre. Sections of fibre are broken with controlled increasing stress or strain that is uniform over the entire fibre length and cross section. The stress or strain is increased at a nominally constant rate until breakage occurs. The distribution of the tensile strength values of a given fibre strongly depends on the sample length, loading velocity and environmental conditions. The test can be used for inspection where statistical data on fibre strength is required. Results are reported by means of statistical quality control distribution. Normally, the test is carried out after temperature and humidity conditioning of the sample. However, in some cases, it can be sufficient to measure the values at ambient temperature and humidity conditions. This method is applicable to categories A1, A2, and A3, and classes B and C optical fibres. The object of this document is to establish uniform requirements for the mechanical characteristic: tensile strength.

Lichtwellenleiter - Teil 1-31: Messmethoden und Prüfverfahren - Zugfestigkeit

Fibres optiques - Partie 1-31: Méthodes de mesure et procédures d’essai - Résistance à la traction

IEC 60793-1-31:2019 donne les valeurs de résistance à la traction des échantillons de fibre optique, soumis à une charge dynamique. Cette méthode soumet à essai des longueurs individuelles de fibre optique en verre, non câblées et non groupées en faisceau. Des sections de fibre sont rompues en les soumettant à une contrainte ou une déformation croissante et contrôlée, uniforme sur toute la longueur et la section transversale de la fibre. La contrainte ou la déformation augmente à une vitesse nominalement constante jusqu’à ce que la rupture se produise. La distribution des valeurs de résistance à la traction pour une fibre donnée dépend étroitement de la longueur des échantillons, de la vitesse d’application de la force et des conditions d’environnement. L’essai peut s’appliquer à titre d’examen lorsque des données statistiques sur la résistance des fibres sont exigées. Les résultats sont déclarés sous forme d’une distribution statistique de contrôle de qualité. Habituellement, l’essai est réalisé après un conditionnement en température et en humidité de l’échantillon. Cependant, dans certains cas, la mesure des valeurs à la température et à l’humidité ambiantes peut être suffisante. Cette méthode s’applique aux fibres optiques de catégories A1, A2 et A3, et de classes B et C. L’objet du présent document est de déterminer des exigences uniformes relatives à la caractéristique mécanique: la résistance à la traction. Cette troisième édition annule et remplace la deuxième édition parue en 2010. Cette édition constitue une révision technique. Cette édition inclut les modifications suivantes par rapport à l’édition précédente: a) correction des Formules (3b) et (4b) et renumérotation des formules. Mots clés : résistance à la traction des échantillons de fibre optique

Optična vlakna - 1-31. del: Metode merjenja in preskusni postopki - Natezna trdnost (IEC 60793-1-31:2019)

Ta del standarda IEC 60793 podaja vrednosti natezne trdnosti pri dinamični obremenitvi vzorcev optičnih vlaken. Metoda preskuša posamezne dolžine nevezanih in ločenih steklenih optičnih vlaken. Odseke vlaken se poskuša prelomiti z nadzorovano naraščajočo napetostjo ali obremenitvijo, ki je enakomerna po celotni dolžini in preseku vlaken. Napetost ali obremenitev se povečujeta pri nominalno konstantni hitrosti, dokler se vlakno ne zlomi.
Porazdelitev vrednosti natezne trdnosti določenega vlakna je zelo odvisna od dolžine vzorca, hitrosti obremenjevanja in okoljskih pogojev. Preskus je mogoče uporabiti v primerih, kjer so potrebni statistični podatki o trdnosti vlaken. Rezultati so opisani s pomočjo statistične porazdelitve v sklopu nadzora kakovosti. Običajno se preskus opravi po obdelavi vzorca pri izbrani temperaturi in vlažnosti. V nekaterih primerih pa je lahko dovolj, da se izmerijo vrednosti pri sobni temperaturi in vlažnosti.
Ta metoda se uporablja za kategorije optičnih vlaken A1, A2 in A3 ter razreda B in C. Cilj tega dokumenta je vzpostaviti enotne zahteve za mehansko lastnost – natezno trdnost.

General Information

Status
Published
Publication Date
04-Apr-2019
Current Stage
6060 - Document made available
Due Date
20-Aug-2019

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SLOVENSKI STANDARD
SIST EN IEC 60793-1-31:2019
01-junij-2019
Nadomešča:
SIST EN 60793-1-31:2010
Optična vlakna - 1-31. del: Metode merjenja in preskusni postopki - Natezna
trdnost (IEC 60793-1-31:2019)

Optical fibres - Part 1-31: Measurement methods and test procedures - Tensile strength

(IEC 60793-1-31:2019)

Lichtwellenleiter - Teil 1-31: Messmethoden und Prüfverfahren - Zugfestigkeit (IEC

60793-1-31:2019)

Fibres optiques - Partie 1-31 : Méthodes de mesure et procédures d’essai - Résistance à

la traction (IEC 60793-1-31:2019)
Ta slovenski standard je istoveten z: EN IEC 60793-1-31:2019
ICS:
33.180.10 (Optična) vlakna in kabli Fibres and cables
SIST EN IEC 60793-1-31:2019 en

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST EN IEC 60793-1-31:2019
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SIST EN IEC 60793-1-31:2019
EUROPEAN STANDARD EN IEC 60793-1-31
NORME EUROPÉENNE
EUROPÄISCHE NORM
April 2019
ICS 33.180.10 Supersedes EN 60793-1-31:2010
English Version
Optical fibres - Part 1-31: Measurement methods and test
procedures - Tensile strength
(IEC 60793-1-31:2019)

Fibres optiques - Partie 1-31: Méthodes de mesure et Lichtwellenleiter - Teil 1-31: Messmethoden und

procédures d'essai - Résistance à la traction Prüfverfahren - Zugfestigkeit
(IEC 60793-1-31:2019) (IEC 60793-1-31:2019)

This European Standard was approved by CENELEC on 2019-03-13. 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: Rue de la Science 23, B-1040 Brussels

© 2019 CENELEC All rights of exploitation in any form and by any means reserved worldwide for CENELEC Members.

Ref. No. EN IEC 60793-1-31:2019 E
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SIST EN IEC 60793-1-31:2019
EN IEC 60793-1-31:2019 (E)
European foreword

The text of document 86A/1908/FDIS, future edition 3 of IEC 60793-1-31, prepared by 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 IEC 60793-1-31:2019.
The following dates are fixed:

• latest date by which the document has to be implemented at national (dop) 2019-12-13

level by publication of an identical national standard or by endorsement

• latest date by which the national standards conflicting with the (dow) 2022-03-13

document have to be withdrawn
This document supersedes EN 60793-1-31:2010.

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 60793-1-31:2019 was approved by CENELEC as a

European Standard without any modification.

In the official version, for Bibliography, the following notes have to be added for the standards

indicated:
IEC 60793-1-21:2001 NOTE Harmonized as EN 60793-1-21:2002 (not modified)
IEC 60793-2-10:2017 NOTE Harmonized as EN 60793-2-10:2017 (not modified)
IEC 60793-2-20:2015 NOTE Harmonized as EN 60793-2-20:2016 (not modified)
IEC 60793-2-30:2015 NOTE Harmonized as EN 60793-2-30:2015 (not modified)
IEC 60793-2-40:2015 NOTE Harmonized as EN 60793-2-40:2016 (not modified)
IEC 60793-2-50:2015 NOTE Harmonized as EN 60793-2-50:2016 (not modified)
IEC 61649:2008 NOTE Harmonized as EN 61649:2008 (not modified)
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SIST EN IEC 60793-1-31:2019
EN IEC 60793-1-31:2019 (E)
Annex ZA
(normative)
Normative references to international publications
with their corresponding European publications

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.

NOTE 1 Where an International Publication has been modified by common modifications, indicated by (mod), the relevant

EN/HD applies.

NOTE 2 Up-to-date information on the latest versions of the European Standards listed in this annex is available here:

www.cenelec.eu.
Publication Year Title EN/HD Year
IEC 60793-1-20 - Optical fibres - Part 1-20: Measurement EN 60793-1-20 -
methods and test procedures - Fibre geometry
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SIST EN IEC 60793-1-31:2019
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SIST EN IEC 60793-1-31:2019
IEC 60793-1-31
Edition 3.0 2019-02
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Optical fibres –
Part 1-31: Measurement methods and test procedures –Tensile strength
Fibres optiques –
Partie 1-31: Méthodes de mesure et procédures d’essai –Résistance à la traction
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 33.180.10 ISBN 978-2-8322-6529-1

Warning! Make sure that you obtained this publication from an authorized distributor.

Attention! Veuillez vous assurer que vous avez obtenu cette publication via un distributeur agréé.

® Registered trademark of the International Electrotechnical Commission
Marque déposée de la Commission Electrotechnique Internationale
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SIST EN IEC 60793-1-31:2019
– 2 – IEC 60793-1-31:2019 © IEC 2019
CONTENTS

FOREWORD ........................................................................................................................... 4

INTRODUCTION ..................................................................................................................... 6

1 Scope .............................................................................................................................. 7

2 Normative references ...................................................................................................... 7

3 Terms and definitions ...................................................................................................... 7

4 Hazards ........................................................................................................................... 7

5 Apparatus ........................................................................................................................ 8

5.1 General ................................................................................................................... 8

5.2 Gripping the fibre at both ends ................................................................................ 8

5.3 Sample support ....................................................................................................... 8

5.4 Stretching the fibre ................................................................................................. 8

5.5 Measuring the force at failure .................................................................................. 9

5.6 Environmental control equipment ............................................................................ 9

6 Sample preparation ....................................................................................................... 10

6.1 Definition .............................................................................................................. 10

6.2 Sample size and gauge length .............................................................................. 10

6.3 Auxiliary measurements ........................................................................................ 11

6.4 Environment ......................................................................................................... 11

7 Procedure ...................................................................................................................... 11

7.1 Preliminary steps .................................................................................................. 11

7.2 Procedure for a single specimen ........................................................................... 11

7.3 Procedure for completing all samples for a given nominal strain rate .................... 12

8 Calculations ................................................................................................................... 12

8.1 Conversion of tensile load to failure stress ............................................................ 12

8.2 Preparation of a Weibull plot ................................................................................. 13

8.3 Computation of Weibull parameters ...................................................................... 13

9 Results .......................................................................................................................... 14

9.1 Details to be reported ........................................................................................... 14

9.2 Details to be recorded ........................................................................................... 15

10 Specification information ............................................................................................... 15

Annex A (informative) Typical testing apparatus of tensile strength under dynamic

loading .................................................................................................................................. 16

Annex B (informative) Guidelines on gripping the fibre ......................................................... 18

Annex C (informative) Guidelines on stress rate .................................................................. 22

Bibliography .......................................................................................................................... 24

Figure 1 – Bimodal tensile strength Weibull plot for a 20 m gauge length test set-up at

5 %/min strain rate ................................................................................................................ 10

Figure A.1 – Capstan design ................................................................................................. 16

Figure A.2 – Translation test apparatus ................................................................................ 16

Figure A.3 – Rotating capstan apparatus .............................................................................. 17

Figure A.4 – Rotating capstan apparatus for long lengths ..................................................... 17

Figure A.5 – Ganged rotating capstan tester ......................................................................... 17

Figure B.1 – Gradual slippage............................................................................................... 18

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IEC 60793-1-31:2019 © IEC 2019 – 3 –

Figure B.2 – Irregular slippage .............................................................................................. 18

Figure B.3 – Sawtooth slippage ............................................................................................ 19

Figure B.4 – Acceptable transfer function ............................................................................. 19

Figure B.5 – Typical capstan ................................................................................................. 20

Figure B.6 – Isostatic compression ....................................................................................... 20

Figure B.7 – Escargot wrap ................................................................................................... 21

Figure C.1 – System to control stress rate ............................................................................ 22

Figure C.2 – Time variation of load and loading speed .......................................................... 23

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SIST EN IEC 60793-1-31:2019
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INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
OPTICAL FIBRES –
Part 1-31: Measurement methods and test procedures –
Tensile strength
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 60793-1-31 has been prepared by subcommittee 86A: Fibres and

cables, of IEC technical committee 86: Fibre optics.

This third edition cancels and replaces the second edition published in 2010. This edition

constitutes a technical revision.

This edition includes the following significant technical changes with respect to the previous

edition:
a) correction of Formulae (3b) and (4b) and renumbering of formulae.
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SIST EN IEC 60793-1-31:2019
IEC 60793-1-31:2019 © IEC 2019 – 5 –
The text of this International Standard is based on the following documents:
FDIS Report on voting
86A/1908/FDIS 86A/1926/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 in 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.
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SIST EN IEC 60793-1-31:2019
– 6 – IEC 60793-1-31:2019 © IEC 2019
INTRODUCTION

Failure stress distributions can be used to predict fibre reliability in different conditions.

IEC TR 62048 shows mathematically how this can be done. To complete a given reliability

projection, the tests used to characterize a distribution are controlled for the following:

• population of fibre, for example coating, manufacturing period, diameter;
• gauge length, i.e. length of section that is tested;
• stress or strain rates;
• testing environment;
• preconditioning or aging treatments;
• sample size.

This method measures the strength of optical fibre at a specified constant strain rate. It is a

destructive test, and is not a substitute for proof-testing.

This method is used for those typical optical fibres for which the median fracture stress is

greater than 3,1 GPa (450 kpsi ) in 0,5 m gauge lengths at the highest specified strain rate of

25 %/min. For fibres with lower median fracture stress, the conditions herein have not

demonstrated sufficient precision.

Typical testing is conducted on "short lengths", up to 1 m, or on "long lengths", from 10 m to

20 m with sample size ranging from 15 to 30.

The test environment and any preconditioning or aging are critical to the outcome of this test.

There is no agreed upon model for extrapolating the results for one environment to another

environment. For failure stress at a given stress or strain rate, however, as the relative

humidity increases, failure stress decreases. Both increases and decreases in the measured

strength distribution parameters have been observed as the result of preconditioning at

elevated temperature and humidity for even a day or two.

This test is based on the theory of fracture mechanics of brittle materials and on the power-

law description of flaw growth (see IEC TR 62048). Although other theories have been

described elsewhere, the fracture mechanics based on power-law theory is the most generally

accepted.
A typical population consists of fibre that has not been deliberately damaged or

environmentally aged. A typical fibre has a nominal diameter of 125 mm, with a 250 mm or less

diameter acrylate coating. Default conditions are given for such typical populations. Non-

typical populations might include alternative coatings, environmentally aged fibre, or

deliberately damaged or abraded fibre. Guidance for non-typical populations is also provided.

__________
kpsi = kilopounds per square inch.
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IEC 60793-1-31:2019 © IEC 2019 – 7 –
OPTICAL FIBRES –
Part 1-31: Measurement methods and test procedures –
Tensile strength
1 Scope

This part of IEC 60793 provides values of the tensile strength under dynamic loading of

optical fibre samples. The method tests individual lengths of uncabled and unbundled glass

optical fibre. Sections of fibre are broken with controlled increasing stress or strain that is

uniform over the entire fibre length and cross section. The stress or strain is increased at a

nominally constant rate until breakage occurs.

The distribution of the tensile strength values of a given fibre strongly depends on the sample

length, loading velocity and environmental conditions. The test can be used for inspection

where statistical data on fibre strength is required. Results are reported by means of

statistical quality control distribution. Normally, the test is carried out after temperature and

humidity conditioning of the sample. However, in some cases, it can be sufficient to measure

the values at ambient temperature and humidity conditions.

This method is applicable to categories A1, A2, and A3, and classes B and C optical fibres.

The object of this document is to establish uniform requirements for the mechanical

characteristic: tensile strength.
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 60793-1-20, Optical fibres – Part 1-20: Measurement methods and test procedures –

Fibre geometry
3 Terms and definitions
No terms and definitions are listed in this document.

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 Hazards

This test involves stretching sections of optical fibre until breakage occurs. Upon breakage,

glass fragments can be distributed in the test area. Protective screens are recommended.

Safety glasses shall be worn at all times in the testing area.
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SIST EN IEC 60793-1-31:2019
– 8 – IEC 60793-1-31:2019 © IEC 2019
5 Apparatus
5.1 General

Clause 5 specifies the fundamental requirements of the equipment used for dynamic strength

testing. There are many configurations that can meet these requirements. Some examples are

presented in Annex A. The choice of a specific configuration will depend on such factors as

• the gauge length of a specimen,
• the stress or strain rate range,
• the environmental conditions, and
• the strength of the specimens.
5.2 Gripping the fibre at both ends

Grip the fibre to be tested at both ends and stretch it until failure occurs in the gauge length

section. The grip shall not allow the fibre to slip out prior to failure and shall minimize failure

at the grip.

Record a break that occurs at the grip, but do not use it in subsequent calculations. Since

fibre strain is increasing during the test, some slippage occurs at the grip. At higher stress

levels, associated with short gauge lengths, slippage can induce damage and cause gripping

failures that are difficult to ascertain. The frequency of such failures can often vary with stress

or strain rate. Careful inspection of the residual fibre pieces, or other means, is required to

prevent the possibility of including gripping failures in the analysis.

Use a capstan, typically covered with an elastomeric sheath, to grip the fibre (see Figure A.1).

Wrap a section of fibre that will not be tested around the capstan several times and secure

the fibre at the ends with, for example, an elastic band. Wrap the fibre with no crossovers.

The capstan surface shall be tough enough so that the fibre does not cut into it when fully

loaded. The amount of slippage and capstan failures depends on the interaction of the fibre

coating and the capstan surface material, thickness, and number of wraps. Careful preliminary

testing is required to confirm the choice of a capstan surface.

Design the diameter of the capstan and pulley so that the fibre does not break on the capstan

due to bend stress. For typical silica-clad fibres, the bend stresses shall not exceed

0,175 GPa.

EXAMPLE For a typical 125 µm cladding/250 µm coating silica fibre, the minimum capstan diameter is 50 mm.

A particular gripping implementation is given in Annex B.
5.3 Sample support

Attach the specimen to the two grips. The gauge length is the length of fibre between the axes

of the gripping capstans before it is stretched. To reduce the space required to perform the

test on long gauge lengths, one or more pulleys may be used to support the specimen (see

Figure A.4). The pulleys shall be designed, and their surfaces kept free of debris, so the fibre

is not damaged by them. The remainder of the fibre, away from pulleys and capstans, shall

not be touched.

When multiple fibres are tested simultaneously, as in Figure A.5, a baffle arrangement is

required to prevent a broken fibre from snapping into, or otherwise perturbing the other fibres

under test.
5.4 Stretching the fibre

Stretch the fibre at a fixed nominal strain rate until it breaks. The nominal strain rate is

expressed as the percent increase in length per minute, relative to the gauge length.

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IEC 60793-1-31:2019 © IEC 2019 – 9 –
There are two basic alternatives for stretching the fibre.

– Method A: Increase the separation between the gripping capstans by moving them apart at

a fixed rate of speed, with the starting separation equal to the gauge length (Figure A.2).

– Method B: Rotate a capstan at a fixed rate to take up the fibre and strain the section

between capstans (Figures A.3 to A.5). The rotation shall not result in crossovers on the

capstan.

Calibrate the strain rate to within ±10 % of the nominal strain rate. Some equipment

configurations are computer-controlled and allow dynamic control of the capstan motion to

produce a constant stress rate. A particular implementation of this is given in Annex C.

The strain rate shall be agreed between customer and supplier. A strain rate range of either

2,5 % to 5 % or 15 % to 25 % is typically used.
5.5 Measuring the force at failure

Measure the tensile load (force in tension) at failure for each specimen by a calibrated load

cell, to within ±1 % of the actual load. This can be done with a variety of methods:

• strip chart recorder;
• peak and hold meter;
• computer sampling.

Provide a means of measuring the tensile load as a function of time to determine the stress

rate. This is not required for each individual test, but shall be done occasionally.

Calibrate the load cell to within 0,5 % of the failure, or maximum load, for each range of

failure loads, while it is oriented in the same manner as when testing a fibre. Do this by

substituting a string attached to a known weight for the test specimen. For method B, a light,

low-friction pulley can be used in place of the capstan that is not attached to the load cell. The

string, with one end attached to the load cell capstan and the other end attached to a known

weight, shall duplicate the direction of a test specimen and be of a diameter comparable to

that of a test specimen. A minimum of three calibration weights, bracketing the typical failures,

is recommended.
5.6 Environmental control equipment

Measured failure stress and fatigue characteristics are known to vary with temperature and

humidity of the fibre, both of which shall be controlled during both preconditioning and test.

Many equipment configurations can be used to provide the required controls, including

controls on the entire room in which testing is conducted.
The following are the typical control requirements:
• temperature: 23 °C ± 2 °C;
• relative humidity: 50 % ± 5 %.

Alternative test environments, such as high non-precipitating humidity, can be achieved by

enclosing the test specimen and injecting water vapour into the enclosure. Figure A.5 shows a

ganged tester that includes an enclosure over a circulating water bath.
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6 Sample preparation
6.1 Definition

A sample is one or more fibres from a population. Each sample provides a result by cutting it

into smaller lengths called specimens. Testing results on these specimens are combined to

yield an overall result for the sample. The term "sample size" is used to indicate the number

of specimens tested in the rest of the document.
For ribbonized fibre, select t
...

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