EN ISO 148-1:2016

Metallic materials - Charpy pendulum impact test - Part 1: Test method (ISO 148-1:2016)

ISO 148-1:2016 specifies the Charpy (V-notch and U-notch) pendulum impact test method for determining the energy absorbed in an impact test of metallic materials. This part of ISO 148 does not cover instrumented impact testing, which is specified in ISO 14556.
Annexes B and C are based on ASTM E23 and are used with the permission of ASTM International, 100 Barr Harbor Drive, P.O. Box C700, West Conshohocken, PA 19428-2959, USA.

Metallische Werkstoffe - Kerbschlagbiegeversuch nach Charpy - Teil 1: Prüfverfahren (ISO 148-1:2016)

Dieser Teil von ISO 148 gilt für Kerbschlagbiegeversuche nach Charpy (V  und U Kerb) für metallische Werk¬stoffe zur Bestimmung der verbrauchten Schlag¬energie. Dieser Teil von ISO 148 gilt nicht für den instrumentierten Kerbschlagbiegeversuch, der in ISO 14556 fest¬gelegt ist.

Matériaux métalliques - Essai de flexion par choc sur éprouvette Charpy - Partie 1: Méthode d'essai (ISO 148-1:2016)

ISO 148-1:2016 spécifie la méthode d'essai de flexion par choc sur éprouvette Charpy (avec entaille en V et avec entaille en U) pour déterminer l'énergie absorbée lors d'un essai de flexion par choc des matériaux métalliques. La présente partie de l'ISO 148 ne couvre pas l'essai de flexion par choc instrumenté, qui est spécifié dans l'ISO 14556.
Les Annexes B et C sont fondées sur l'ASTM E23 et sont utilisées avec la permission de ASTM International, 100 Barr Harbor Drive, P.O. Box C700, West Conshohocken, PA 19428-2959, États-Unis.

Kovinski materiali - Udarni preskus po Charpyju - 1. del: Preskusna metoda (ISO 148-1:2016)

Ta del standarda ISO 148 določa preskusno metodo udarnega preskusa po Charpyju (V-zareza in U-zareza) za določanje energije, ki se absorbira pri udarnih preskusih kovinskih materialov. Ta del standarda ISO 148 ne zajema instrumentiranega udarnega preskušanja, ki je podano v standardu ISO 14556.
Dodatka B in C temeljita na standardu ASTM E23 in se uporabljata z dovoljenjem organizacije ASTM.

General Information

• Status: Withdrawn
• Publication Date: 27-Feb-2017
• Withdrawal Date: 30-May-2017
• ICS: 77.040.10 - Mechanical testing of metals
• Technical Committee: ECISS/TC 101 - Test methods for steel (other than chemical analysis)
• Drafting Committee: ECISS/TC 101 - Test methods for steel (other than chemical analysis)
• Current Stage: 6060 - Definitive text made available (DAV) - Publishing
• Start Date: 23-Nov-2016
• Completion Date: 23-Nov-2016
• Ref Project: SIST EN ISO 148-1:2017 - Metallic materials - Charpy pendulum impact test - Part 1: Test method (ISO 148-1:2016)

Relations

• Replaces: EN ISO 148-1:2010 - Metallic materials - Charpy pendulum impact test - Part 1: Test method (ISO 148-1:2009)
• Effective Date: 28-Aug-2013

Standards Content (Sample)

SLOVENSKI STANDARD
SIST EN ISO 148-1:2017
01-februar-2017
1DGRPHãþD
SIST EN ISO 148-1:2010
Kovinski materiali - Udarni preskus po Charpyju - 1. del: Preskusna metoda (ISO
148-1:2016)

Metallic materials - Charpy pendulum impact test - Part 1: Test method (ISO 148-1:2016)

Metallische Werkstoffe - Kerbschlagbiegeversuch nach Charpy - Teil 1: Prüfverfahren

(ISO 148-1:2016)

Matériaux métalliques - Essai de flexion par choc sur éprouvette Charpy - Partie 1:

Méthode d'essai (ISO 148-1:2016)
Ta slovenski standard je istoveten z: EN ISO 148-1:2016
ICS:
77.040.10 Mehansko preskušanje kovin Mechanical testing of metals
SIST EN ISO 148-1:2017 en,fr,de

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

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SIST EN ISO 148-1:2017
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SIST EN ISO 148-1:2017
EN ISO 148-1
EUROPEAN STANDARD
NORME EUROPÉENNE
November 2016
EUROPÄISCHE NORM
ICS 77.040.10 Supersedes EN ISO 148-1:2010
English Version
Metallic materials - Charpy pendulum impact test - Part 1:
Test method (ISO 148-1:2016)

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

éprouvette Charpy - Partie 1: Méthode d'essai (ISO Charpy - Teil 1: Prüfverfahren (ISO 148-1:2016)

148-1:2016)
This European Standard was approved by CEN on 20 August 2016.

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

© 2016 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 148-1:2016 E

worldwide for CEN national Members.
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SIST EN ISO 148-1:2017
EN ISO 148-1:2016 (E)
Contents Page

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

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SIST EN ISO 148-1:2017
EN ISO 148-1:2016 (E)
European foreword

This document (EN ISO 148-1:2016) 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 May 2017, and conflicting national standards shall be

withdrawn at the latest by May 2017.

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 148-1:2010.

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 148-1:2016 has been approved by CEN as EN ISO 148-1:2016 without any modification.

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SIST EN ISO 148-1:2017
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SIST EN ISO 148-1:2017
INTERNATIONAL ISO
STANDARD 148-1
Third edition
2016-10-15
Metallic materials — Charpy
pendulum impact test —
Part 1:
Test method
Matériaux métalliques — Essai de flexion par choc sur éprouvette
Charpy —
Partie 1: Méthode d’essai
Reference number
ISO 148-1:2016(E)
ISO 2016
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SIST EN ISO 148-1:2017
ISO 148-1:2016(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2016, 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. [phone]
Fax [phone]
[e-mail]
www.iso.org
ii © ISO 2016 – All rights reserved
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SIST EN ISO 148-1:2017
ISO 148-1:2016(E)
Contents Page

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

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

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

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

3.1 Definitions pertaining to energy .............................................................................................................................................. 1

3.2 Definitions pertaining to test piece ....................................................................................................................................... 2

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

5 Principles of the test ......................................................................................................................................................................................... 3

6 Test pieces ................................................................................................................................................................................................................... 3

6.1 General ........................................................................................................................................................................................................... 3

6.2 Notch geometry ...................................................................................................................................................................................... 4

6.2.1 V-notch ...................................................................................................................................................................................... 4

6.2.2 U-notch ..................................................................................................................................................................................... 4

6.3 Tolerance of the test pieces .......................................................................................................................................................... 4

6.4 Preparation of the test pieces..................................................................................................................................................... 4

6.5 Marking of the test pieces .............................................................................................................................................................. 4

7 Test equipment....................................................................................................................................................................................................... 4

7.1 General ........................................................................................................................................................................................................... 4

7.2 Installation and verification ........................................................................................................................................................ 5

7.3 Striker ............................................................................................................................................................................................................. 5

8 Test procedure ........................................................................................................................................................................................................ 5

8.1 General ........................................................................................................................................................................................................... 5

8.2 Friction measurement ...................................................................................................................................................................... 5

8.3 Test temperature ................................................................................................................................................................................... 6

8.4 Specimen transfer ................................................................................................................................................................................ 7

8.5 Exceeding machine capacity ....................................................................................................................................................... 7

8.6 Incomplete fracture ............................................................................................................................................................................ 7

8.7 Test piece jamming .............................................................................................................................................................................. 8

8.8 Post-fracture inspection.................................................................................................................................................................. 8

9 Test report ................................................................................................................................................................................................................... 8

9.1 Mandatory information ................................................................................................................................................................... 8

9.2 Optional information ......................................................................................................................................................................... 8

Annex A (informative) Self-centring tongs ..................................................................................................................................................12

Annex B (informative) Lateral expansion.....................................................................................................................................................13

Annex C (informative) Fracture appearance .............................................................................................................................................16

Annex D (informative) Absorbed energy vs. temperature curve and the transition temperature ...19

Annex E (informative) Measurement uncertainty of an absorbed energy value, K ..........................................21

Bibliography .............................................................................................................................................................................................................................29

© ISO 2016 – All rights reserved iii
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SIST EN ISO 148-1:2017
ISO 148-1:2016(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 World Trade Organization (WTO) principles in the

Technical Barriers to Trade (TBT) see the following URL: www.iso.org/iso/foreword.html.

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

SC 4, Toughness testing — Fracture (F), Pendulum (P), Tear (T).

This third edition cancels and replaces the second edition (ISO 148-1:2009), which has been technically

revised.

ISO 148 consists of the following parts, under the general title Metallic materials — Charpy pendulum

impact test:
— Part 1: Test method
— Part 2: Verification of testing machines

— Part 3: Preparation and characterization of Charpy V-notch test pieces for indirect verification of

pendulum impact machines
iv © ISO 2016 – All rights reserved
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SIST EN ISO 148-1:2017
INTERNATIONAL STANDARD ISO 148-1:2016(E)
Metallic materials — Charpy pendulum impact test —
Part 1:
Test method
1 Scope

This part of ISO 148 specifies the Charpy (V-notch and U-notch) pendulum impact test method for

determining the energy absorbed in an impact test of metallic materials. This part of ISO 148 does not

cover instrumented impact testing, which is specified in ISO 14556.

Annexes B and C are based on ASTM E23 and are used with the permission of ASTM International, 100

Barr Harbor Drive, P.O. Box C700, West Conshohocken, PA 19428-2959, USA.
2 Normative references

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

and are indispensable for the application of this document. For dated references, only the edition

cited applies. For undated references, the latest edition of the referenced document (including any

amendments) applies.

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

ISO 286-1, Geometrical product specifications (GPS) — ISO code system for tolerances on linear sizes —

Part 1: Basis of tolerances, deviations and fits
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1 Definitions pertaining to energy
3.1.1
initial potential energy
potential energy

potential energy of the pendulum hammer prior to its release for the impact test, as determined by

direct verification
3.1.2
absorbed energy

energy required to break a test piece with a pendulum impact testing machine, after correction for

friction

Note 1 to entry: The letter V or U is used to indicate the notch geometry, that is: KV or KU. The number 2 or 8 is

used as a subscript to indicate the radius of the striker, for example KV .
3.1.3
nominal initial potential energy
nominal energy
energy assigned by the manufacturer of the pendulum impact testing machine
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SIST EN ISO 148-1:2017
ISO 148-1:2016(E)
3.2 Definitions pertaining to test piece
3.2.1
width
distance between the notched face and the opposite face
Note 1 to entry: See Figure 1.

Note 2 to entry: In previous versions of the ISO 148 series (prior to 2016), the distance between the notched face

and the opposite face was specified as “height”. Changing this dimension to “width” makes this part of ISO 148

consistent with the terminology used in other ISO fracture standards.
3.2.2
thickness
dimension perpendicular to the width and parallel to the notch
Note 1 to entry: See Figure 1.

Note 2 to entry: In previous versions of the ISO 148 series (prior to 2016), the dimension perpendicular to the

width that is parallel to the notch was specified as “width”. Changing this dimension to “thickness” makes this

part of ISO 148 consistent with the terminology used in other ISO fracture standards.

3.2.3
length
largest dimension perpendicular to the notch
Note 1 to entry: See Figure 1.
4 Symbols and abbreviated terms

The symbols and designations applicable to this part of ISO 148 are indicated in Tables 1 and 2, and are

illustrated in Figure 2.
Table 1 — Symbols and their unit and designation
Symbol Unit Designation
B mm thickness of test piece
α ° angle of fall of the pendulum

β J or ° angle of rise when the machine is operated in the normal manner without a test

piece in position

β J or ° angle of rise when the machine is operated in the normal manner without a test

piece in position and without resetting the indication mechanism
L mm length of test piece
LE mm lateral expansion

K J absorbed energy (expressed as KV , KV , KU , KU , to identify specific notch geome-

2 8 2 8
tries and the radius of the striking edge)

K J or ° indicated absorbed energy when the machine is operated in the normal manner

without a test piece in position

K J or ° indicated absorbed energy when the machine is operated in the normal manner

without a test piece in position and without resetting the indication mechanism
K J or ° nominal initial potential energy
K J initial potential energy (potential energy)
KV J absorbed energy for a V-notch test piece using a 2 mm striker
2 © ISO 2016 – All rights reserved
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SIST EN ISO 148-1:2017
ISO 148-1:2016(E)
Table 1 (continued)
Symbol Unit Designation
KV J absorbed energy for a V-notch test piece using a 8 mm striker
KU J absorbed energy for a U-notch test piece using a 2 mm striker
KU J absorbed energy for a U-notch test piece using an 8 mm striker
M N·m moment equal to the product F·l
p J absorbed energy loss caused by pointer friction
p’ J absorbed energy loss caused by bearing friction and air resistance
p J correction of absorbed energy losses for an angle of rise β
SFA % shear fracture appearance
T °C transition temperature
W mm width of test piece
transition temperature defined at a specific value of absorbed energy;
T °C
t27
for example, 27 J

transition temperature defined at a particular percentage of the absorbed energy of

T °C
t50 %US
the upper shelf; for example, 50 %
transition temperature defined at a particular proportion of shear fracture;
T °C
t50 %SFA
for example, 50 %
transition temperature defined at a particular amount of lateral expansion;
T °C
t0,9
for example, 0,9 mm
5 Principles of the test

This test consists of breaking a notched test piece with a single blow from a swinging pendulum, under

the conditions defined in Clauses 6, 7 and 8. The notch in the test piece has a specified geometry and

is located in the middle between two supports, opposite to the location which is impacted in the test.

The energy absorbed in the impact test, the lateral expansion and the shear fracture appearance are

normally determined.

Because the impact values of many metallic materials vary with temperature, tests shall be carried out

at a specified temperature. When this temperature is other than ambient, the test piece shall be heated

or cooled to that temperature, under controlled conditions.

The Charpy pendulum impact test is often used in routine, high-throughput pass/fail acceptance tests

in industrial settings. For these tests, it may not be important whether the test sample is completely

broken, partially broken, or simply plastically deformed and dragged through the anvils. In research,

design, or academic settings, the measured energy values are studied in more detail, in which case it

can be highly relevant whether the sample is broken or not.

It is important to note that not all Charpy pendulum impact test results can be directly compared. For

example, the test can be performed with hammers having strikers with different radii, or with different

[7]

test piece shapes. Tests performed with different strikers can give different results, and test results

obtained with differently shaped test pieces can as well. This is why not only the adherence to ISO 148

but also a clear and complete reporting of the type of instrument, the test piece and the details of the

post-test test pieces are crucial for comparability of results.
6 Test pieces
6.1 General

The standard test piece shall be 55 mm long and of square section, with 10 mm sides. In the centre of

the length, there shall be either a V-notch or a U-notch, as described in 6.2.1 and 6.2.2, respectively.

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SIST EN ISO 148-1:2017
ISO 148-1:2016(E)

If the standard test piece cannot be obtained from the material, one of the subsize test pieces, having a

thickness of 7,5 mm, 5 mm or 2,5 mm (see Figure 2 and Table 2), shall be used, if not otherwise specified.

NOTE 1 Direct comparison of results is only of significance when made between test pieces of the same form

and dimensions.

NOTE 2 For low energies, the use of shims to better position subsize test pieces relative to the centre of

strike is important to avoid excess energy absorption by the pendulum. For high energies, this might not be as

important. Shims can be placed on or under the test piece supports, with the result that the mid-thickness of

the specimen is 5 mm above the 10 mm supports. Shims can be temporarily fixed to the supports using tape or

another means.

When a heat-treated material is being evaluated, the test piece shall be finish-machined and notched

after the final heat treatment, unless it can be demonstrated that machining before heat treatment does

not affect test results.
6.2 Notch geometry

The notch shall be carefully prepared so that the root radius of the notch is free of machining marks

which could affect the absorbed energy.

The plane of symmetry of the notch shall be perpendicular to the longitudinal axis of the test piece

(see Figure 2).
6.2.1 V-notch

The V-notch shall have an included angle of 45°, a depth of 2 mm and a root radius of 0,25 mm

[see Figure 2 a) and Table 2].
6.2.2 U-notch

The U-notch shall have a depth of 5 mm (unless otherwise specified) and a root radius of 1 mm

[see Figure 2 b) and Table 2].
6.3 Tolerance of the test pieces

The tolerances on the specified test piece and notch dimensions are shown in Figure 2 and Table 2.

6.4 Preparation of the test pieces

Preparation shall be executed in such a way that any alteration of the test piece, for example due to

heating or cold working, is minimized.
6.5 Marking of the test pieces

The test piece may be marked on any face not in contact with supports, anvils or striker and at a position

where plastic deformation and surface discontinuities caused by marking do not affect the absorbed

energy (see 8.8).
7 Test equipment
7.1 General

The measurements of the instrument and test piece details shall be traceable to national or international

standards. Equipment used for measurements shall be calibrated within suitable intervals.

4 © ISO 2016 – All rights reserved
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SIST EN ISO 148-1:2017
ISO 148-1:2016(E)
7.2 Installation and verification

The testing machine shall be installed and verified in accordance with ISO 148-2.

7.3 Striker

The striker geometry shall be specified as being either the 2 mm striker or the 8 mm striker. It is

recommended that the radius on the striker be shown as a subscript as follows: KV or KV and KU or

2 8 2
KU .

Reference shall be made to the product specification for striker geometry guidance.

[7]
NOTE Tests carried out with 2 mm and 8 mm strikers can give different results.
8 Test procedure
8.1 General

The test piece shall lie squarely against the anvils of the testing machine, with the plane of symmetry

of the notch within 0,5 mm of the mid-plane between the anvils. It shall be struck by the striker in the

plane of symmetry of the notch and on the side opposite the notch (see Figure 1).

8.2 Friction measurement

The energy absorbed by friction shall be checked on every testing day prior to the first test. The friction

losses may be estimated as explained below, but other methods may also be applied.

NOTE The energy absorbed by friction includes, but is not limited to, air resistance, bearing friction and the

friction of the indicating pointer. Increases in friction on a machine can influence the measure of absorbed energy.

8.2.1 To determine the loss caused by pointer friction the machine is operated in the normal manner,

but without a test piece in position, and the angle of rise, β , or energy reading, K , is noted. A second

1 1

test is then carried out without resetting the indication pointer and the new angle of rise, β , or energy

reading, K , is noted. Thus, the loss due to friction in the indicating pointer during the rise is equal to

p = M(cos β − cos β) (1)
1 2
when the scale is graduated in degrees, or
p = K − K (2)
1 2
when the scale is graduated in energy units.
NOTE For machines without a pointer, this friction measurement is not necessary.

8.2.2 The procedure to determine the losses caused by bearing friction and air resistance for one half

swing is as follows.

After determining β or K , the pendulum is returned to its initial position. Without resetting the

2 2

indicating mechanism, release the pendulum without shock and vibration and permit it to swing 10

half swings. After the pendulum starts its 11th half swing, move the indicating mechanism to about

© ISO 2016 – All rights reserved 5
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SIST EN ISO 148-1:2017
ISO 148-1:2016(E)

5 % of the scale-range capacity and record the value as β or K . The losses by bearing friction and air

3 3
resistance for one half swing are equal to
p′ = 1/10 M(cos β − cos β) (3)
3 2
when the scale is graduated in degrees, or
p′ = 1/10 (K − K) (4)
3 2
when the scale is graduated in energy units.

The number of swings can be changed at the discretion of machine users, and p’ should be corrected on

account of the applied number of swings.

NOTE 1 If it is required to take into account these losses in an actual test giving an angle of rise, β, the quantity

can be subtracted from the value of the absorbed energy.
αβ+
pp=+ p (5)
β αβ+
1 2

Because β and β are nearly equal to α, the angle of fall, for practical purposes Formula (5) can be

1 2
reduced to:
αβ+
pp=+ p (6)
α 2α

For machines graduated in energy units, the value of β can be calculated as follows:

β = arccos[1 − 1/M(K − K)] (7)
P T

The total friction loss, p + p′, so measured, shall not exceed 0,5 % of the nominal energy, K . If it does,

and it is not possible to bring the friction loss within the tolerance by reducing the

...