Metallic materials - Charpy V-notch pendulum impact test - Instrumented test method (ISO 14556:2015)

ISO 14556:2015 specifies a method of instrumented Charpy V-notch pendulum impact testing on metallic materials and the requirements concerning the measurement and recording equipment.
With respect to the Charpy pendulum impact test described in ISO 148‑1, this test provides further information on the fracture behaviour of the product under impact testing conditions.
General information about instrumented impact testing can be found in Reference [1] to Reference [5].

Metallische Werkstoffe - Kerbschlagbiegeversuch nach Charpy (V-Kerb) - Instrumentiertes Prüfverfahren (ISO 14556:2015)

In dieser Internationalen Norm sind der instrumentierte Kerbschlagbiegeversuch nach Charpy (V Kerb) für metallische Werkstoffe sowie Anforderungen an die Mess  und Aufzeichnungseinrichtungen festgelegt.
In Bezug auf den in ISO 148 1 beschriebenen Kerbschlagbiegeversuch nach Charpy ermöglicht der hier beschriebene Versuch weitergehende Aussagen über das Bruchverhalten des untersuchten Erzeugnisses unter schlagartigen Beanspruchungsbedingungen.
Allgemeine Angaben zum instrumentierten Kerbschlagbiegeversuch können den Literaturhinweisen [1 bis 5] entnommen werden.

Matériaux métalliques - Essai de flexion par choc sur éprouvette Charpy à entaille en V - Méthode d’essai instrumenté (ISO 14556:2015)

ISO 14456:2015 spécifie une méthode d'essai instrumenté de flexion par choc sur éprouvette Charpy à entaille en V pour les produits métalliques ainsi que les prescriptions concernant le dispositif de mesure et d'enregistrement.
Par rapport à l'essai de flexion par choc sur éprouvette Charpy décrit dans la norme ISO 148‑1, le présent essai fournit des informations supplémentaires sur le comportement à la rupture du produit soumis à des conditions d'essai de choc.
Des informations à caractère général sur la méthode d'essai instrumenté de flexion par choc peuvent être trouvées dans les références[1] à [5].

Kovinski materiali - Udarni preskus žilavosti po Charpyju (V-zareza) - Instrumentirana preskusna metoda (ISO 14556:2015)

Ta mednarodni standard določa metodo instrumentiranega udarnega preskusa žilavosti po Charpyju (V-zareza) na kovinskih materialih ter zahteve glede opreme za merjenje in beleženje.
Glede na udarni preskus po Charpyju, opisan v ISO 148-1, ta preskus zagotavlja dodatne informacije o obnašanju razpokanja izdelka pod pogoji udarnega preskušanja.
Splošne informacije o instrumentiranem udarnem preskušanju so navedene v referencah [1] do [5].

General Information

Status
Withdrawn
Publication Date
30-Jan-2016
Withdrawal Date
29-Apr-2016
Current Stage
6060 - Definitive text made available (DAV) - Publishing
Start Date
07-Oct-2015
Completion Date
07-Oct-2015

Relations

Buy Standard

Standard
EN ISO 14556:2016
English language
27 pages
sale 10% off
Preview
sale 10% off
Preview
e-Library read for
1 day

Standards Content (Sample)

SLOVENSKI STANDARD
SIST EN ISO 14556:2016
01-januar-2016
1DGRPHãþD
SIST EN ISO 14556:2001
SIST EN ISO 14556:2001/A1:2007
Kovinski materiali - Udarni preskus žilavosti po Charpyju (V-zareza) -
Instrumentirana preskusna metoda (ISO 14556:2015)

Metallic materials - Charpy V-notch pendulum impact test - Instrumented test method

(ISO 14556:2015)
Metallische Werkstoffe - Kerbschlagbiegeversuch nach Charpy (V Kerb) -
Instrumentiertes Prüfverfahren (ISO 14556:2015)

Matériaux métalliques - Essai de flexion par choc sur éprouvette Charpy à entaille en V -

Méthode d'essai instrumenté (ISO 14556:2015)
Ta slovenski standard je istoveten z: EN ISO 14556:2015
ICS:
77.040.10 Mehansko preskušanje kovin Mechanical testing of metals
SIST EN ISO 14556:2016 en,fr,de

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

---------------------- Page: 1 ----------------------
SIST EN ISO 14556:2016
---------------------- Page: 2 ----------------------
SIST EN ISO 14556:2016
EN ISO 14556
EUROPEAN STANDARD
NORME EUROPÉENNE
October 2015
EUROPÄISCHE NORM
ICS 77.040.10 Supersedes EN ISO 14556:2000
English Version
Metallic materials - Charpy V-notch pendulum impact test
- Instrumented test method (ISO 14556:2015)

Matériaux métalliques - Essai de flexion par choc sur Metallische Werkstoffe - Kerbschlagbiegeversuch nach

éprouvette Charpy à entaille en V - Méthode d'essai Charpy (V-Kerb) - Instrumentiertes Prüfverfahren (ISO

instrumenté (ISO 14556:2015) 14556:2015)
This European Standard was approved by CEN on 3 July 2015.

CEN 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 CEN

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 CEN member into its own language and notified to the CEN-CENELEC Management

Centre has the same status as the official versions.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,

Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania,

Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and

United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
CEN-CENELEC Management Centre: Avenue Marnix 17, B-1000 Brussels

© 2015 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 14556:2015 E

worldwide for CEN national Members.
---------------------- Page: 3 ----------------------
SIST EN ISO 14556:2016
EN ISO 14556:2015 (E)
Contents Page

European foreword ....................................................................................................................................................... 3

---------------------- Page: 4 ----------------------
SIST EN ISO 14556:2016
EN ISO 14556:2015 (E)
European foreword

This document (EN ISO 14556:2015) has been prepared by Technical Committee ISO/TC 164

“Mechanical testing of metals” in collaboration with Technical Committee ECISS/TC 101 “Test methods

for steel (other than chemical analysis)” the secretariat of which is held by AFNOR.

This European Standard shall be given the status of a national standard, either by publication of an

identical text or by endorsement, at the latest by April 2016, and conflicting national standards shall be

withdrawn at the latest by April 2016.

Attention is drawn to the possibility that some of the elements of this document may be the subject of

patent rights. CEN [and/or CENELEC] shall not be held responsible for identifying any or all such patent

rights.
This document supersedes EN ISO 14556:2000.

According to the CEN-CENELEC Internal Regulations, the national standards organizations of the

following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria,

Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, Former Yugoslav Republic of Macedonia,

France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta,

Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland,

Turkey and the United Kingdom.
Endorsement notice

The text of ISO 14556:2015 has been approved by CEN as EN ISO 14556:2015 without any modification.

---------------------- Page: 5 ----------------------
SIST EN ISO 14556:2016
---------------------- Page: 6 ----------------------
SIST EN ISO 14556:2016
INTERNATIONAL ISO
STANDARD 14556
Second edition
2015-09-01
Metallic materials — Charpy
V-notch pendulum impact test —
Instrumented test method
Matériaux métalliques — Essai de flexion par choc sur éprouvette
Charpy à entaille en V — Méthode d’essai instrumenté
Reference number
ISO 14556:2015(E)
ISO 2015
---------------------- Page: 7 ----------------------
SIST EN ISO 14556:2016
ISO 14556:2015(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2015, Published in Switzerland

All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized otherwise in any form

or by any means, electronic or mechanical, including photocopying, or posting on the internet or an intranet, without prior

written permission. Permission can be requested from either ISO at the address below or ISO’s member body in the country of

the requester.
ISO copyright office
Ch. de Blandonnet 8 • CP 401
CH-1214 Vernier, Geneva, Switzerland
Tel. +41 22 749 01 11
Fax +41 22 749 09 47
copyright@iso.org
www.iso.org
ii © ISO 2015 – All rights reserved
---------------------- Page: 8 ----------------------
SIST EN ISO 14556:2016
ISO 14556:2015(E)
Contents Page

Foreword ........................................................................................................................................................................................................................................iv

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ...................................................................................................................................................................................... 1

3 Terms and definitions ..................................................................................................................................................................................... 1

3.1 Characteristic values of force...................................................................................................................................................... 1

3.2 Characteristic values of displacement ................................................................................................................................ 2

3.3 Characteristic values of impact energy .............................................................................................................................. 2

4 Symbols and abbreviated terms ........................................................................................................................................................... 2

5 Principle ........................................................................................................................................................................................................................ 3

6 Apparatus ..................................................................................................................................................................................................................... 4

7 Test piece ...................................................................................................................................................................................................................... 6

8 Test procedure ........................................................................................................................................................................................................ 6

9 Expression of results ........................................................................................................................................................................................ 6

9.1 General ........................................................................................................................................................................................................... 6

9.2 Evaluation of the force-displacement curve .................................................................................................................. 7

9.3 Determination of the characteristic values of force ................................................................................................ 7

9.4 Determination of the characteristic values of displacement ........................................................................... 7

9.5 Determination of the characteristic values of impact energy ........................................................................ 9

10 Test report ................................................................................................................................................................................................................... 9

Annex A (informative) Designs of instrumented strikers ..........................................................................................................11

Annex B (informative) Example of support block for the calibration of a 2 mm striker ...........................12

Annex C (informative) Formulae for the estimation of the proportion of ductile fracture surface 13

Annex D (normative) Instrumented Charpy V-notch pendulum impact testing of miniature

test pieces .................................................................................................................................................................................................................14

Bibliography .............................................................................................................................................................................................................................20

© ISO 2015 – All rights reserved iii
---------------------- Page: 9 ----------------------
SIST EN ISO 14556:2016
ISO 14556:2015(E)
Foreword

ISO (the International Organization for Standardization) is a worldwide federation of national standards

bodies (ISO member bodies). The work of preparing International Standards is normally carried out

through ISO technical committees. Each member body interested in a subject for which a technical

committee has been established has the right to be represented on that committee. International

organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.

ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of

electrotechnical standardization.

The procedures used to develop this document and those intended for its further maintenance are

described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the

different types of ISO documents should be noted. This document was drafted in accordance with the

editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).

Attention is drawn to the possibility that some of the elements of this document may be the subject of

patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of

any patent rights identified during the development of the document will be in the Introduction and/or

on the ISO list of patent declarations received (see www.iso.org/patents).

Any trade name used in this document is information given for the convenience of users and does not

constitute an endorsement.

For an explanation on the meaning of ISO specific terms and expressions related to conformity

assessment, as well as information about ISO’s adherence to the WTO principles in the Technical

Barriers to Trade (TBT) see the following URL: Foreword - Supplementary information

The committee responsible for this document is ISO/TC 164, Mechanical testing of metals, Subcommittee

SC 4, Toughness testing.

This second edition cancels and replaces the first edition (ISO 14556:2000), which has been

technically revised.
iv © ISO 2015 – All rights reserved
---------------------- Page: 10 ----------------------
SIST EN ISO 14556:2016
INTERNATIONAL STANDARD ISO 14556:2015(E)
Metallic materials — Charpy V-notch pendulum impact test
— Instrumented test method
1 Scope

This International Standard specifies a method of instrumented Charpy V-notch pendulum impact testing

on metallic materials and the requirements concerning the measurement and recording equipment.

With respect to the Charpy pendulum impact test described in ISO 148-1, this test provides further

information on the fracture behaviour of the product under impact testing conditions.

General information about instrumented impact testing can be found in Reference [1] to Reference [5].

2 Normative references

The following documents, in whole or in part, are normatively referenced in this document and are

indispensable for its application. For dated references, only the edition cited applies. For undated

references, the latest edition of the referenced document (including any amendments) applies.

ISO 148-1, Metallic materials — Charpy pendulum impact test — Part 1: Test method.

ISO 148-2, Metallic materials — Charpy pendulum impact test — Part 2: Verification of testing machines.

3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1 Characteristic values of force
3.1.1
general yield force

force at the transition point from the linearly increasing part to the curved increasing part of the force-

displacement curve

Note 1 to entry: It represents a first approximation of the force at which yielding has occurred across the entire

test piece ligament (see 9.3).
3.1.2
maximum force
maximum force in the course of the force-displacement curve
3.1.3
unstable crack initiation force

force at the beginning of the steep drop in the force-displacement curve (unstable crack initiation)

3.1.4
crack arrest force
force at the end (arrest) of unstable crack propagation
© ISO 2015 – All rights reserved 1
---------------------- Page: 11 ----------------------
SIST EN ISO 14556:2016
ISO 14556:2015(E)
3.2 Characteristic values of displacement
3.2.1
general yield displacement
displacement corresponding to the general yield force, F
3.2.2
displacement at maximum force
displacement corresponding to the maximum force, F
3.2.3
crack initiation displacement
displacement corresponding to the force at unstable crack initiation, F
3.2.4
crack arrest displacement

displacement corresponding to the force at the end (arrest) of unstable crack propagation, F

3.2.5
total displacement
displacement at the end of the force-displacement curve
3.3 Characteristic values of impact energy
3.3.1
energy at maximum force
partial impact energy from s = 0 to s = s
3.3.2
unstable crack initiation energy
partial impact energy from s = 0 to s = s
3.3.3
crack arrest energy
partial impact energy from s =0 to s = s
3.3.4
total impact energy
energy absorbed by the test piece during the test

Note 1 to entry: Calculated from the area under the force-displacement curve from s =0 to s = s .

4 Symbols and abbreviated terms

For the purposes of this document, the symbols and abbreviations given in Table 1 are applicable (see

also Figure 2 and Figure 3).
2 © ISO 2015 – All rights reserved
---------------------- Page: 12 ----------------------
SIST EN ISO 14556:2016
ISO 14556:2015(E)
Table 1 — Symbols and designations
Symbol Designation Unit
f Output frequency limit Hz
F Force N
F Crack arrest force N
F General yield force N
F Unstable crack initiation force N
F Maximum force N
g Acceleration due to gravity m/s
h Height of fall of the centre of strike of the pendulum (see ISO 148-2) m
KV Absorbed energy as defined in ISO 148-1 J

m Effective mass of the pendulum corresponding to its effective weight (see ISO 148-2) kg

s Displacement m
s Crack arrest displacement m
s General yield displacement m
s Displacement at unstable crack initiation m
s Displacement at maximum force m
s Total displacement m
t Time s
t Time at the beginning of deformation of the test piece s
t Signal rise time s
v Initial striker impact velocity m/s
v Striker impact velocity at time t m/s
W Crack arrest energy J
W Energy at unstable crack initiation J
W Energy at maximum force J
W Total impact energy J
5 Principle

5.1 This test consists of measuring the impact force, in relation to the test piece bending displacement,

during an impact test carried out in accordance with ISO 148-1. The area under the force-displacement

curve is a measure of the energy absorbed by the test piece.

5.2 Force-displacement curves for different steel products and different temperatures can be quite

different, even though the areas under the curves and the absorbed energies are identical. If the force-

displacement curves are divided into characteristic parts, various phases of the test can be deduced

which provide considerable information about the behaviour of the test piece at impact loading rates.

NOTE The force-displacement curve cannot be used in strength calculations of structures. It is not possible

to directly determine the lowest permissible operating temperature for a material in a construction.

© ISO 2015 – All rights reserved 3
---------------------- Page: 13 ----------------------
SIST EN ISO 14556:2016
ISO 14556:2015(E)
6 Apparatus
6.1 Testing machine

A pendulum impact testing machine, in accordance with ISO 148-2, and instrumented to determine the

force-time or force-displacement curve shall be used.

Comparisons between the total impact energy, W , from the instrumentation and the absorbed energy

indicated by the machine dial or encoder, KV, shall be made.

NOTE 1 The instrumentation and the machine dial or encoder measure similar but different quantities.

Differences are to be expected (see Reference[6]).

If deviations between KV and W exceed ±5 J, the following should be investigated:

a) friction of the machine;
b) calibration of the measuring system;
c) software used.
6.2 Instrumentation and calibration
6.2.1 Traceable measurement

The equipment used for all calibration measurements shall be traceable to national or international

standards of measurement.
6.2.2 Force measurement

Force measurement is usually achieved by using two active electric resistance strain gauges attached

to the standard striker to form a force transducer. Suitable designs are shown in Annex A.

A full bridge circuit is made by two equally stressed (active) strain gauges bonded to opposite sides of

the striker and by two compensating (passive) strain gauges, or by substitute resistors. Compensating

strain gauges shall not be attached to any part of the testing machine which experiences impact or

vibration effects.

NOTE 1 Alternately, any other instrumentation to form a force transducer, which meets the required

performance levels, may be used.

The force measuring system (instrumented striker, amplifier, recording system) shall have a response

of at least 100 kHz, which corresponds to a rise time, t, of no more than 3,5 µs.

A simple dynamic assessment of the force measuring chain can be performed by measuring the

value of the first inertia peak. By experience, the dynamics of the measuring chain can be considered

satisfactory if a steel V-notch test piece shows an initial peak greater than 8 kN when using an impact

velocity between 5 m/s and 5,5 m/s. This is valid if the centres of the active strain gauges are 11 mm to

15 mm away from the striker contact point.

The instrumentation of the striker shall be adequate to give the required nominal force range. The

instrumented striker shall be designed to minimize its sensitivity to non-symmetric loading.

NOTE 2 Experience shows that with the V-notch test piece, nominal impact forces up to 40 kN can occur for

most steel types.
6.2.3 Calibration

Calibration of the recorder and measuring system may be performed statically in accordance with the

accuracy requirements given below and in 6.2.4.
4 © ISO 2015 – All rights reserved
---------------------- Page: 14 ----------------------
SIST EN ISO 14556:2016
ISO 14556:2015(E)

It is recommended that the force calibration be performed with the striker built into the hammer assembly.

Force is applied to the striker through a special load frame equipped with a calibrated load cell and

using a special support block in the position of the test piece.

This support block shall have a high stiffness. The contact conditions shall be approximately equal to

those of the test and give reproducible results.

NOTE 1 An example of the support block for the calibration of a 2 mm striker is given in Annex B.

The static linearity and hysteresis error of the built-in, instrumented striker, including all parts of the

measurement system up to the recording apparatus (printer, plotter, etc.), shall be within ±2 % of the

recorded force, between 50 % and 100 % of the nominal force range, and within ±1 % of the full scale

force value between 10 % and 50 % of the nominal force range (see Figure 1).

For the instrumented striker alone, it is recommended that the accuracy be ±1 % of the recorded value

between 10 % and 100 % of the nominal range.
Key
X recorded value as percentage of nominal range
Y absolute error as percentage of nominal range

Figure 1 — Maximum permissible error of recorded values within the nominal force range

6.2.4 Displacement measurement
Displacement is normally determined from force-time measurements. See Clause 9.

Displacement can also be determined by non-contacting measurement of the displacement of the striker,

relative to the anvil, using optical, inductive, or capacitive methods. The signal transfer characteristics

of the displacement measurement system shall correspond to that of the force measuring system in

order to make the two recording systems synchronous.

The displacement measuring system shall be designed for nominal values up to 30 mm; linearity errors

in the measuring system shall yield measured values to within ±2 % in the range 1 mm to 30 mm. A

© ISO 2015 – All rights reserved 5
---------------------- Page: 15 ----------------------
SIST EN ISO 14556:2016
ISO 14556:2015(E)

dynamic calibration of the displacement system can be achieved by releasing the pendulum without a

test piece in place, when the velocity is determined by:
vg= 2 h (1)
0 n

The velocity signal registered when the pendulum passes through the lowest position shall correspond

to velocity v .

It is recommended that displacements between 0 mm and 1 mm be determined from time measurements

and the striker impact velocity, using double numerical integration as described in 9.1.

6.2.5 Recording apparatus

Recording of the dynamic signals is preferably achieved by digital storage recorders, with output of the

test results to an X-Y printer or plotter. In order to meet the accuracies required in 6.2.3 and 6.2.4 with

digital measurement and recording systems, at least an 8 bit analogue-digital converter, with a sampling

rate of 250 kHz (4 µs), is required; however, 12 bit and 1 MHz are recommended. A minimum storage

capacity of 2 000 data points is required for each signal over an 8 ms time period, if the recording is

to be adequate; however, 8 000 data points are recommended. For signals less than 8 ms, the required

storage capacity may be reduced in proportion.

When values are determined from force-displacement graphs, sufficient precision is achieved by

producing graphs at least 100 mm high by 100 mm wide.
6.2.6 Calibration interval

It is recommended that calibration of the instrumentation be performed at intervals not exceeding 12

months, or whenever the pendulum impact machine or instrumentation has undergone dismantling,

moving, repair, or adjustment. In the case of striker replacement, it is recommended that a calibration

be performed, unless it can be demonstrated that it is not necessary.
7 Test piece
The test piece is a Charpy V-notch test piece, in accordance with ISO 148-1.
8 Test procedure

Perform the Charpy V-notch pendulum impact test in accordance with ISO 148-1. In addition, determine

and evaluate the force-displacement curve with respect to various characteristic deformation and

fracture stages.
9 Expression of results
9.1 General

If the displacement is not directly measured, calculate the force-displacement curve as follows. The

force-time relationship measured on the striker is proportional to the acceleration characteristic. Given

an assumed rigid pendulum of effective mass m, the initial impact velocity v , and the time t following

the beginning of the deformation at t , the test piece bending displacement is calculated by double

numerical integration using:
vt()=−v Ft()dt (2)
6 © ISO 2015 – All rights reserved
---------------------- Page: 16 ----------------------
SIST EN ISO 14556:2016
ISO 14556:2015(E)
st()= vt()dt (3)
9.2 Evaluation of the force-displacement curve

Characteristic force-displacement curves of various types are shown in Figure 2, in order to simplify

evaluation and reporting. These can be classified in the following categories:
— Type A and B (lower shelf);
— Type C, D, and E (transition);
— Type F (upper shelf).

With force-displacement curves of Type A, only unstable crack propagation occurs. For Types B, C, D,

and E, various amounts of stable and unstable crack propagation can occur. With Type F curves, only

stable crack propagation occurs.

Determine the type of force-displacement curve by comparison with the schematic representations

given in Figure 2 (column 2). With force-displacement curves of Type A, only F can be evaluated. With

curves of Type B, only F and F can be evaluated.
iu a

In the following sections, the evaluation of the force-displacement curve is explained. It should be noted

that vibrations are superimposed on the force-displacement signal, which arise from force interaction

between the instrumented striker and the test piece. Generally, a fitted curve through the oscillations,

as shown in Figure 3, yields reliable characteristic values.
9.3 Determination of the characteristic values of force

Determine the general yield force, F , as the force at the intersection between the linear elastic part

of the force-displacement curve, discarding the initial inertia peak, and the fitted curve through the

oscillations of the force-displacement curve following the onset of yield of the entire ligament (Figure 2,

force-displacement curves of Type C to Type F).

Determine the maximum force, F , as the maximum value of the fitted curve through the oscillations.

Determine the unstable crack initiation force, F , as the force at the intersection between the fitted

curve through the oscillations, after the occurrence of general yield, and the steeply dropping part of

the force-displacement curve. If the steep drop coincides with the maximum recorded force, then F =

F (force-displacement curves of Types C or D).

Determine the crack arrest force, F , as the force at the intersection between the steep drop of the

force-displacement curve and the fitted curve through the oscillations of the subsequent part of the

force-displacement curve (force-displacement curves of Type D or Type E).
9.4 Determination of the characteristic values of displacement

The characteristic values of displacement given in 3.2 are the abscissa values of the characteristic

values of force determined according to 9.3, (see Figure 2).

NOTE 1 The general yield displacement, s , can only be approximately determined using common measuring

apparatus. Consequently, s is not generally used.

NOTE 2 Due to the steep drop in the force-displacement curve between F and F , it is generally the case

iu a
that s ≈ s .
iu a

The total displacement, s , is only determined if the test piece becomes completely fractured during

the test and the force-displacement curve up to the fracture of the test piece is available. In such a case,

the fitted curve through the oscillations of the force-displacement curve approaches asymptotically

© ISO 2015 – All rights reserved 7
---------------------- Page: 17 ----------------------
SIST EN ISO 14556:2016
ISO 14556:2015(E)

the force F = 0. The total displacement, s , is given as the abscissa value of the fitted curve through the

oscillations corresponding to F = 0.

NOTE 3 If the force does not return to the baseline (i.e. F = 0) within the testing time selected but approaches

asymptotically a value F > 0, the total displacement, s , may be defined as the abscissa value of the fitted curve

through the oscillations corresponding to F = 0,02 F .
Key
1 type o
...

Questions, Comments and Discussion

Ask us and Technical Secretary will try to provide an answer. You can facilitate discussion about the standard in here.