Metallic materials - Knoop hardness test - Part 1: Test method (ISO 4545-1:2017)

This document specifies the Knoop hardness test method for metallic materials for test forces from
0,009 807 N to 19,613 N.
The Knoop hardness test is specified in this document for lengths of indentation diagonals ≥0,020 mm.
Using this method to determine Knoop hardness from smaller indentations is outside the scope of this
document as results would suffer from large uncertainties due to the limitations of optical measurement
and imperfections in tip geometry. ISO 14577-1 allows the determination of hardness from smaller
indentations.
A periodic verification method is specified for routine checking of the testing machine in service by
the user.
Special considerations for Knoop testing of metallic coatings can be found in ISO 4516.

Metallische Werkstoffe - Härteprüfung nach Knoop - Teil 1: Prüfverfahren (ISO 4545-1:2017)

Dieses Dokument legt das Verfahren für die Härteprüfung nach Knoop an metallischen Werkstoffen für Prüfkräfte von 0,009 807 N bis 19,613 N fest.
In diesem Dokument ist die Härteprüfung nach Knoop festgelegt für Eindruckdiagonallängen ≥ 0,020 mm. Die Verwendung dieses Verfahrens zur Bestimmung der Knoop-Härte für kleinere Eindrücke gehört nicht zum Anwendungsbereich in diesem Dokument, weil die Resultate wegen Grenzen der optischen Messung und Unvollkommenheiten der Kegelgeometrie mit großer Unsicherheit behaftet wären. ISO 14577 1 erlaubt die Härte-Bestimmung von kleineren Eindrücken.
Eine periodische Überprüfung ist angegeben zur laufenden Kontrolle der Prüfmaschine in Betrieb durch den Anwender.
Besondere Überlegungen zur Prüfung metallischer Überzüge nach Knoop können ISO 4516 entnommen werden.

Matériaux métalliques - Essai de dureté Knoop - Partie 1 : Méthode d'essai (ISO 4545-1:2017)

ISO 4545-1:2017 spécifie la méthode d'essai de dureté Knoop pour les matériaux métalliques, pour des forces d'essai comprises entre 0,009 807 N et 19,613 N.
Le présent document spécifie l'essai de dureté Knoop pour les longueurs de diagonale d'empreinte ≥ 0,020 mm. L'utilisation de cette méthode pour déterminer la dureté Knoop d'empreintes plus petites ne fait pas partie du domaine d'application du présent document, car les résultats ainsi obtenus présenteraient des incertitudes élevées en raison des limitations du mesurage optique et des imperfections concernant la géométrie de la pointe. L'ISO 14577‑1 permet de déterminer la dureté des empreintes plus petites.
Une méthode de vérification périodique est spécifiée pour la vérification de routine, par l'utilisateur, de la machine d'essai utilisée.
Des considérations particulières pour les essais Knoop des revêtements métalliques sont disponibles dans l'ISO 4516.

Kovinski materiali - Preskus trdote po Knoopu - 1. del: Preskusna metoda (ISO 4545-1:2017)

Ta dokument določa metodo za preskus trdote po Knoopu za kovinske materiale s preskusnimi silami od 0,009 807 N do 19,613 N.
Preskus trdote po Knoopu je v tem dokumentu določen za dolžine diagonal zarez ≥ 0,020 mm. Uporaba te metode za določanje trdote po Knoopu na podlagi manjših zarez ne sodi v področje uporabe tega dokumenta, saj bi bili rezultati nezanesljivi zaradi negotovosti, povezane z omejitvami optičnega merjenja in nepravilnostmi geometrije konice. Določevanje trdote na podlagi manjših zarez omogoča standard ISO 14577-1.
Določena je tudi metoda za redno preverjanje pri rutinskem pregledovanju naprave za preskušanje, ki jo uporablja
uporabnik. Posebne zahteve za preskušanje kovinskih prevlek so navedene v standardu ISO 4516.

General Information

Status
Published
Public Enquiry End Date
09-Aug-2015
Publication Date
07-May-2018
Current Stage
6060 - National Implementation/Publication (Adopted Project)
Start Date
21-Mar-2018
Due Date
26-May-2018
Completion Date
08-May-2018

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SLOVENSKI STANDARD
SIST EN ISO 4545-1:2018
01-julij-2018
1DGRPHãþD
SIST EN ISO 4545-1:2006
Kovinski materiali - Preskus trdote po Knoopu - 1. del: Preskusna metoda (ISO
4545-1:2017)
Metallic materials - Knoop hardness test - Part 1: Test method (ISO 4545-1:2017)

Metallische Werkstoffe - Härteprüfung nach Knoop - Teil 1: Prüfverfahren (ISO 4545-

1:2017)

Matériaux métalliques - Essai de dureté Knoop - Partie 1 : Méthode d'essai (ISO 4545-

1:2017)
Ta slovenski standard je istoveten z: EN ISO 4545-1:2018
ICS:
77.040.10 Mehansko preskušanje kovin Mechanical testing of metals
SIST EN ISO 4545-1:2018 en

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

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SIST EN ISO 4545-1:2018
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SIST EN ISO 4545-1:2018
EN ISO 4545-1
EUROPEAN STANDARD
NORME EUROPÉENNE
March 2018
EUROPÄISCHE NORM
ICS 77.040.10 Supersedes EN ISO 4545-1:2005
English Version
Metallic materials - Knoop hardness test - Part 1: Test
method (ISO 4545-1:2017)

Matériaux métalliques - Essai de dureté Knoop - Partie Metallische Werkstoffe - Härteprüfung nach Knoop -

1: Méthode d'essai (ISO 4545-1:2017) Teil 1: Prüfverfahren (ISO 4545-1:2017)
This European Standard was approved by CEN on 30 November 2017.

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, Serbia, 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: Rue de la Science 23, B-1040 Brussels

© 2018 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 4545-1:2018 E

worldwide for CEN national Members.
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SIST EN ISO 4545-1:2018
EN ISO 4545-1:2018 (E)
Contents Page

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

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SIST EN ISO 4545-1:2018
EN ISO 4545-1:2018 (E)
European foreword

This document (EN ISO 4545-1:2018) 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 September 2018, and conflicting national standards

shall be withdrawn at the latest by September 2018.

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

patent rights. CEN shall not be held responsible for identifying any or all such patent rights.

This document supersedes EN ISO 4545-1:2005.

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, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland,

Turkey and the United Kingdom.
Endorsement notice

The text of ISO 4545-1:2017 has been approved by CEN as EN ISO 4545-1:2018 without any

modification.
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SIST EN ISO 4545-1:2018
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SIST EN ISO 4545-1:2018
INTERNATIONAL ISO
STANDARD 4545-1
Second edition
2017-12
Metallic materials — Knoop
hardness test —
Part 1:
Test method
Matériaux métalliques — Essai de dureté Knoop —
Partie 1: Méthode d'essai
Reference number
ISO 4545-1:2017(E)
ISO 2017
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SIST EN ISO 4545-1:2018
ISO 4545-1:2017(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2017, 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 2017 – All rights reserved
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SIST EN ISO 4545-1:2018
ISO 4545-1:2017(E)
Contents Page

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

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

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

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

4 Principle ........................................................................................................................................................................................................................ 1

5 Symbols and designations .......................................................................................................................................................................... 2

5.1 Symbols and designations used in this document ................................................................................................... 2

5.2 Designation of hardness number ............................................................................................................................................ 3

6 Testing machine .................................................................................................................................................................................................... 3

6.1 Testing machine ..................................................................................................................................................................................... 3

6.2 Indenter ......... ................................................................................................................................................................................................ 3

6.3 Diagonal measuring system ......................................................................................................................................................... 4

7 Test piece ...................................................................................................................................................................................................................... 4

7.1 Test Surface ................................................................................................................................................................................................ 4

7.2 Preparation ................................................................................................................................................................................................ 4

7.3 Thickness ..................................................................................................................................................................................................... 4

7.4 Support of unstable test pieces ................................................................................................................................................. 4

8 Procedure..................................................................................................................................................................................................................... 5

8.1 Test temperature ................................................................................................................................................................................... 5

8.2 Test force ...................................................................................................................................................................................................... 5

8.3 Periodic verification ........................................................................................................................................................................... 5

8.4 Test piece support ................................................................................................................................................................................ 5

8.5 Focus on test surface .......................................................................................................................................................................... 5

8.6 Test force application ........................................................................................................................................................................ 6

8.7 Prevention of the effect of shock or vibration .............................................................................................................. 6

8.8 Minimum distance between adjacent indentations ................................................................................................ 6

8.9 Measurement of diagonal length ............................................................................................................................................. 7

8.10 Calculation of hardness value .................................................................................................................................................... 7

9 Uncertainty of the results ............................................................................................................................................................................ 7

10 Test report ................................................................................................................................................................................................................... 7

Annex A (normative) Procedure for periodic checking of the testing machine, diagonal

measuring system and the indenter by the user ................................................................................................................. 9

Annex B (informative) Uncertainty of the measured hardness values ..........................................................................11

Annex C (informative) Knoop hardness measurement traceability .................................................................................18

Annex D (informative) CCM — Working group on hardness .....................................................................................................22

Annex E (informative) Adjustment of Köhler illumination systems .................................................................................23

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

© ISO 2017 – All rights reserved iii
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SIST EN ISO 4545-1:2018
ISO 4545-1:2017(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 voluntary nature of standards, 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.

This document was prepared by Technical Committee ISO/TC 164, Mechanical testing of metals,

Subcommittee SC 3, Hardness testing.

This second edition cancels and replaces the first edition (ISO 4545-1:2005), which has been technically

revised.
The main changes compared to the previous edition are as follows:
— all references have been removed of indentation diagonals <0,020 mm;
— the resolution requirements have been defined for the measuring system;

— the lower test force limit of the Knoop hardness test has been expanded to 0,009 807 N;

— the requirements for the periodic (weekly or daily) verifications of the testing machine have been

defined as normative, the maximum permissible bias value has been revised, and the requirements

for the maximum permissible error in measuring a reference indentation have been revised;

— the recommendations for inspection and monitoring of the indenter have been added (moved from

ISO 4545-2);

— the requirements have been revised for the approach velocity of the indenter prior to contact with

the sample surface;

— the timing requirements for the test force application and the duration at maximum test force are

revised to indicate target time values;

— Figure 3 has been added illustrating the requirements for the minimum distance between

indentations; the distances have been stated with respect to the indentation centres rather than

the indentation limits, but the requirements have not changed;

— the requirements have been added to the test report for reporting the test date and any hardness

conversion method used;
iv © ISO 2017 – All rights reserved
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SIST EN ISO 4545-1:2018
ISO 4545-1:2017(E)

— Annexes C, D and E have been added concerning Knoop hardness measurement traceability, the

CCM — Working group on hardness and adjustment of Köhler illumination systems, respectively.

A list of all parts in the ISO 4545 series can be found on the ISO website.
© ISO 2017 – All rights reserved v
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SIST EN ISO 4545-1:2018
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SIST EN ISO 4545-1:2018
INTERNATIONAL STANDARD ISO 4545-1:2017(E)
Metallic materials — Knoop hardness test —
Part 1:
Test method
1 Scope

This document specifies the Knoop hardness test method for metallic materials for test forces from

0,009 807 N to 19,613 N.

The Knoop hardness test is specified in this document for lengths of indentation diagonals ≥0,020 mm.

Using this method to determine Knoop hardness from smaller indentations is outside the scope of this

document as results would suffer from large uncertainties due to the limitations of optical measurement

and imperfections in tip geometry. ISO 14577-1 allows the determination of hardness from smaller

indentations.

A periodic verification method is specified for routine checking of the testing machine in service by

the user.

Special considerations for Knoop testing of metallic coatings can be found in ISO 4516.

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.

ISO 4545-2, Metallic materials — Knoop hardness test — Part 2: Verification and calibration of testing

machines

ISO 4545-3, Metallic materials — Knoop hardness test — Part 3: Calibration of reference blocks

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 Principle

A diamond indenter, in the form of a rhombic-based pyramid with angles, α and β, between opposite

edges respectively equal to 172,5° and 130° at the vertex, is forced into the surface of a test piece

followed by measurement of the long diagonal, d, of the indentation remaining in the surface after

removal of the test force, F (see Figures 1 and 2).
© ISO 2017 – All rights reserved 1
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SIST EN ISO 4545-1:2018
ISO 4545-1:2017(E)
Figure 1 — Principle of the test and indenter geometry
Figure 2 — Knoop indentation

The Knoop hardness is proportional to the quotient obtained by dividing the test force by the projected

area of the indentation, which is assumed to be a rhombic-based pyramid, and having at the vertex the

same angles as the indenter.

NOTE As applicable, this test document has adopted hardness test parameters as defined by the working

group on hardness (CCM-WGH) under the framework of the International Committee of Weights and Measures

(CIPM) Consultative Committee for Mass and Related Quantities (CCM) (see Annex D).

5 Symbols and designations
5.1 Symbols and designations used in this document
See Table 1 and Figures 1 and 2.
Table 1 — Symbols and designations
Symbol Designation
F Test force, in newtons (N)
d Length of the long diagonal, in millimetres
d Length of the short diagonal, in millimetres

α Angle between the opposite edges of the long diagonal at the vertex of the diamond pyramid

indenter (nominally 172,5°) (see Figure 1)

β Angle between the opposite edges of the short diagonal at the vertex of the diamond pyramid

(nominally 130°) (see Figure 1)

NOTE Standard acceleration due to gravity, g = 9,806 65 m/s , which is the conversion factor from kgf to N.

To reduce uncertainty, the Knoop hardness can be calculated using the actual indenter angles α and β.

2 © ISO 2017 – All rights reserved
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SIST EN ISO 4545-1:2018
ISO 4545-1:2017(E)
Table 1 (continued)
Symbol Designation
V Magnification of the measuring system

c Indenter constant, relating projected area of the indentation to the square of the length of the

long diagonal
tan
Indenter constant, c= , for nominal angles α and β, c is approximately 0,070 28
2tan
Test force (kgf)
Knoop hardness =
Projected area of indentation (mm )
1 Test force (N)

n Projected area of indentation (mm )
1 F

n cd
For the nominal indenter constant c ≈ 0,070 28,
Knoop hardness ≈×1,451

NOTE Standard acceleration due to gravity, g = 9,806 65 m/s , which is the conversion factor from kgf to N.

To reduce uncertainty, the Knoop hardness can be calculated using the actual indenter angles α and β.

5.2 Designation of hardness number
Knoop hardness, HK, is designated as shown in the following example.
640 HK 0,1 ⁄20
Duration of test force (20 s)
if not within the speciied range (10 s to 15 s)
Approximate kgf equivalent value of
applied test force where (0,1 kgf = 0,980 7 N)
Hardness symb ol
Knoop hardness valu e
6 Testing machine
6.1 Testing machine

The testing machine shall be capable of applying a predetermined force or forces within the desired

range of test forces, in accordance with ISO 4545-2.
6.2 Indenter

The indenter shall be a diamond in the shape of a rhombic-based pyramid, as specified in ISO 4545-2.

© ISO 2017 – All rights reserved 3
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SIST EN ISO 4545-1:2018
ISO 4545-1:2017(E)
6.3 Diagonal measuring system
The diagonal measuring system shall satisfy the requirements in ISO 4545-2.

Magnifications should be provided so that the diagonal can be enlarged to greater than 25 % but less

than 75 % of the maximum possible optical field of view. Many objective lenses are non-linear towards

the edge of the field of view.

NOTE A diagonal measuring system using a camera for measurement can use 100 % of the camera’s field of

view, provided it is designed to consider field of view limitations of the optical system.

The resolution required of the diagonal measuring system depends on the size of the smallest

indentation to be measured, and shall be in accordance with Table 2. In determining the resolution of

the measuring system, the resolution of the microscope optics, the digital resolution of the measuring

scale and the step-size of any stage movement, where applicable, should be taken into account.

Table 2 — Resolution of the measuring system
Diagonal length
Resolution of the measuring
system
0,020 ≤ d < 0,080 0,000 4 mm
0,080 ≤ d 0,5 % of d
7 Test piece
7.1 Test Surface

The test shall be carried out on a polished surface, which is smooth and even, free from oxide scale and

foreign matter and, in particular, free from lubricants, unless otherwise specified in product standards.

The finish of the surface shall permit accurate determination of the diagonal length of the indentation.

7.2 Preparation

Surface preparation shall be carried out in such a way as to prevent surface damage, or alteration of the

surface hardness due to excessive heating or cold-working.

Due to the small depth of Knoop hardness indentations, it is essential that special precautions be taken

during preparation. It is recommended to use a polishing/electropolishing technique that is adapted to

the material to be measured.
7.3 Thickness

The thickness of the test piece, or of the layer under test, shall be at least 1/3 times the length of the

diagonal length of the indentation. No deformation shall be visible at the back of the test piece after

the test.

NOTE The depth of the indentation is approximately 1/30 of the diagonal length (0,033 d).

7.4 Support of unstable test pieces

For a test piece of small cross-section or of irregular shape, either a dedicated support should be used

or it should be mounted in a similar manner to a metallographic micro-section in appropriate material

so that it is adequately supported and does not move during the force application.

4 © ISO 2017 – All rights reserved
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SIST EN ISO 4545-1:2018
ISO 4545-1:2017(E)
8 Procedure
8.1 Test temperature

The test is normally carried out at ambient temperature within the limits of 10 °C to 35 °C. If the test

is carried out at a temperature outside this range, it shall be noted in the test report. Tests carried out

under controlled conditions shall be made at a temperature of (23 ± 5) °C.
8.2 Test force

The test forces given in Table 3 are typical. Other test forces may be used. Test forces shall be chosen

that result in indentations with a long diagonal greater than 0,020 mm.
Table 3 — Typical test forces
Test force value, F
Hardness scale
N Approximate kgf equivalent
HK 0,001 0,009 807 0,001
HK 0,002 0,019 61 0,002
HK 0,005 0,049 03 0,005
HK 0,01 0,098 07 0,010
HK 0,02 0,196 1 0,020
HK 0,025 0,245 2 0,025
HK 0,05 0,490 3 0,050
HK 0,1 0,980 7 0,100
HK 0,2 1,961 0,200
HK 0,3 2,942 0,300
HK 0,5 4,903 0,500
HK 1 9,807 1,000
HK 2 19,613 2,000
Not an SI unit.
8.3 Periodic verification

The periodic verification defined in Annex A shall be performed within a week prior to use for each test

force used but is recommended on the day of use. The periodic verification is recommended whenever

the test force is changed. The periodic verification shall be done whenever the indenter is changed.

8.4 Test piece support

The test piece shall be placed on a rigid support. The support surfaces shall be clean and free from

foreign matter (scales, oil, dirt, etc.). It is important that the test piece lies firmly on the support so that

any displacement that affects the test result cannot occur during the test.
8.5 Focus on test surface

The diagonal measuring system microscope shall be focused so that the specimen surface and the

desired test location can be observed.

NOTE Some testing machines do not require that the microscope be focused on the specimen surface.

© ISO 2017 – All rights reserved 5
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Edge of test piece
SIST EN ISO 4545-1:2018
ISO 4545-1:2017(E)
8.6 Test force application

The indenter shall be brought into contact with the test surface and the test force shall be applied in a

direction perpendicular to the surface, without shock, vibration or overload, until the applied force

attains the specified value. The time from the initial application of the force until the full test force is

reached shall be 7 s .

NOTE 1 The requirements for the time durations are given with asymmetric limits. For example, 7 s

indicates that 7 s is the nominal time duration, with an acceptable range of not less than 2 s (calculated as 7 s – 5 s)

to not more than 8 s (calculated as 7 s + 1 s).
The indenter shall contact the test piece at a velocity of ≤0,070 mm/s.

The duration of the test force shall be 14 s, except for tests on materials whose time-dependent

properties would make this an unsuitable range. For these tests, this duration shall be specified as part

of the hardness designation (see 5.2).

NOTE 2 There is evidence that some materials are sensitive to the rate of straining which causes changes in

the value of the yield strength. The corresponding effect on the termination of the formation of an indentation

can make alterations in the hardness value.
8.7 Prevention of the effect of shock or vibration
[6]

Throughout the test, the testing machine shall be protected from shock or vibration .

8.8 Minimum distance between adjacent indentations

The minimum distance between adjacent indentations and the minimum distance between an

indentation and the edge of the test piece are shown in Figure 3.

The minimum distance between the edge of the test piece and the centre of any indentation oriented

parallel to the edge of the test piece shall be at least 3,5 times the length of the short diagonal of the

indentation. The minimum distance between the edge of the test piece and the centre of any indentation

oriented perpendicular to the edge of the test piece shall be at least equal to the length of the long

diagonal of the indentation.

The minimum distance between the centres of two adjacent indentations, oriented side-by-side,

shall be at least 3,5 times the length of the short diagonal. For indentations oriented end-to-end, the

minimum distance between the centres of two adjacent indents shall be at least twice the length of the

long diagonal. If two indentations differ in size, the minimum spacing shall be based on the diagonal of

the larger indentation.
Edge of test piece
3,5 d
2 dd
3,5 d
Figure 3 — Minimum distance for Knoop indentations
6 © ISO 2017 – All rights reserved
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SIST EN ISO 4545-1:2018
ISO 4545-1:2017(E)
8.9 Measurement of diagonal length
The
...

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