prEN ISO 14577-2
(Main)Metallic materials - Instrumented indentation test for hardness and materials parameters - Part 2: Verification and calibration of testing machines (ISO/DIS 14577-2:2024)
Metallic materials - Instrumented indentation test for hardness and materials parameters - Part 2: Verification and calibration of testing machines (ISO/DIS 14577-2:2024)
ISO 14577-2:2015 specifies the method of verification and calibration of testing machines for carrying out the instrumented indentation test in accordance with ISO 14577‑1:2015.
It describes a direct verification method for checking the main functions of the testing machine and an indirect verification method suitable for the determination of the repeatability of the testing machine. There is a requirement that the indirect method be used in addition to the direct method and for the periodic routine checking of the testing machine in service.
It is a requirement that the indirect method of verification of the testing machine be carried out independently for each test method.
ISO 14577-2:2015 is also applicable for transportable testing machines.
Metallische Werkstoffe - Instrumentierte Eindringprüfung zur Bestimmung der Härte und anderer Werkstoffparameter - Teil 2: Überprüfung und Kalibrierung der Prüfmaschinen (ISO/DIS 14577‑2:2024)
Matériaux métalliques - Essai de pénétration instrumenté pour la détermination de la dureté et de paramètres des matériaux - Partie 2: Vérification et étalonnage des machines d'essai (ISO/DIS 14577-2:2024)
L'ISO 14577-2:2015 spécifie la méthode de vérification et d'étalonnage des machines d'essai destinées à la réalisation de l'essai de pénétration instrumenté conformément à l'ISO 14577‑1:2015.
Elle décrit une méthode de vérification directe pour contrôler les fonctions principales de la machine d'essai et une méthode de vérification indirecte appropriée pour la détermination de la répétabilité de la machine d'essai. Il est exigé que la méthode indirecte soit utilisée en sus de la méthode directe et pour le contrôle de routine périodique de la machine d'essai en service.
Il est exigé que la méthode indirecte de vérification de la machine d'essai soit réalisée de façon indépendante pour chaque méthode d'essai.
L'ISO 14577-2:2015 est également applicable aux machines d'essai transportables.
Kovinski materiali - Instrumentirano vtiskanje pri preskušanju trdote in drugih lastnosti materialov - 2. del: Overjanje in kalibriranje preskuševalnih strojev (ISO/DIS 14577-2:2024)
General Information
Relations
Standards Content (Sample)
SLOVENSKI STANDARD
01-september-2024
Kovinski materiali - Instrumentirano vtiskanje pri preskušanju trdote in drugih
lastnosti materialov - 2. del: Overjanje in kalibriranje preskuševalnih strojev
(ISO/DIS 14577-2:2024)
Metallic materials - Instrumented indentation test for hardness and materials parameters
- Part 2: Verification and calibration of testing machines (ISO/DIS 14577-2:2024)
Metallische Werkstoffe - Instrumentierte Eindringprüfung zur Bestimmung der Härte und
anderer Werkstoffparameter - Teil 2: Überprüfung und Kalibrierung der Prüfmaschinen
(ISO/DIS 14577-2:2024)
Matériaux métalliques - Essai de pénétration instrumenté pour la détermination de la
dureté et de paramètres des matériaux - Partie 2: Vérification et étalonnage des
machines d'essai (ISO/DIS 14577-2:2024)
Ta slovenski standard je istoveten z: prEN ISO 14577-2
ICS:
77.040.10 Mehansko preskušanje kovin Mechanical testing of metals
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
DRAFT
International
Standard
ISO/DIS 14577-2
ISO/TC 164/SC 3
Metallic materials — Instrumented
Secretariat: DIN
indentation test for hardness and
Voting begins on:
materials parameters —
2024-08-02
Part 2:
Voting terminates on:
2024-10-25
Verification and calibration of
testing machines
Matériaux métalliques — Essai de pénétration instrumenté pour
la détermination de la dureté et de paramètres des matériaux —
Partie 2: Vérification et étalonnage des machines d'essai
ICS: 77.040.10
THIS DOCUMENT IS A DRAFT CIRCULATED
FOR COMMENTS AND APPROVAL. IT
IS THEREFORE SUBJECT TO CHANGE
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Reference number
ISO/DIS 14577-2:2024(en)
DRAFT
ISO/DIS 14577-2:2024(en)
International
Standard
ISO/DIS 14577-2
ISO/TC 164/SC 3
Metallic materials — Instrumented
Secretariat: DIN
indentation test for hardness and
Voting begins on:
materials parameters —
Part 2:
Voting terminates on:
Verification and calibration of
testing machines
Matériaux métalliques — Essai de pénétration instrumenté pour
la détermination de la dureté et de paramètres des matériaux —
Partie 2: Vérification et étalonnage des machines d'essai
ICS: 77.040.10
THIS DOCUMENT IS A DRAFT CIRCULATED
FOR COMMENTS AND APPROVAL. IT
IS THEREFORE SUBJECT TO CHANGE
AND MAY NOT BE REFERRED TO AS AN
INTERNATIONAL STANDARD UNTIL
PUBLISHED AS SUCH.
This document is circulated as received from the committee secretariat.
IN ADDITION TO THEIR EVALUATION AS
BEING ACCEPTABLE FOR INDUSTRIAL,
© ISO 2024
TECHNOLOGICAL, COMMERCIAL AND
USER PURPOSES, DRAFT INTERNATIONAL
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
STANDARDS MAY ON OCCASION HAVE TO
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Published in Switzerland Reference number
ISO/DIS 14577-2:2024(en)
ii
ISO/DIS 14577-2:2024(en)
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 General conditions . 1
3.1 Preparation .1
3.2 Functional installation .1
3.3 Indenter . . .2
3.4 Application of the test force .2
4 Direct verification and calibration . . 2
4.1 General .2
4.2 Calibration of the test force .2
4.3 Calibration of the displacement measuring device .3
4.4 Verification and calibration of the machine compliance .4
4.4.1 General .4
4.4.2 Procedure .4
4.5 Calibration and verification of the indenter .5
4.5.1 General .5
4.5.2 Vickers indenter .6
4.5.3 Berkovich, modified Berkovich, and corner cube indenters .7
4.5.4 Ball indenters .8
4.5.5 Spheroconical indenters .9
4.6 Verification of the indenter area function .10
4.6.1 General .10
4.6.2 Procedure .10
4.7 Verification of the testing cycle .11
5 Indirect verification .11
5.1 General .11
5.2 Procedure . 12
6 Intervals between calibrations and verifications .13
6.1 Direct verification and calibration . 13
6.2 Indirect verification .14
6.3 Routine checking .14
7 Verification report/Calibration certificate . 14
Annex A (informative) Example of an indenter holder .15
Annex B (normative) Procedures for determination of indenter area function .16
Annex C (informative) Examples for the documentation of the results of indirect verification .18
Annex D (normative) Machine compliance calibration procedure.20
Bibliography .24
iii
ISO/DIS 14577-2:2024(en)
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 3, Hardness testing.
This third edition cancels and replaces the second edition (ISO 14577-2:2015), which has been technically
revised.
ISO 14577 consists of the following parts, under the general title Metallic materials — Instrumented
indentation test for hardness and materials parameters:
— Part 1: Test method
— Part 2: Verification and calibration of testing machines
— Part 3: Calibration of reference blocks
— Part 4: Test method for metallic and non-metallic coatings
— Part 5: Linear elastic dynamic instrumented indentation testing (DIIT)
iv
ISO/DIS 14577-2:2024(en)
Introduction
Hardness has typically been defined as the resistance of a material to permanent penetration by another
harder material. The results obtained when performing Rockwell, Vickers, and Brinell tests are determined
after the test force has been removed. Therefore, the effect of elastic deformation under the indenter has
been ignored.
ISO 14577 (all parts) has been prepared to enable the user to evaluate the indentation of materials by
considering both the force and displacement during plastic and elastic deformation. By monitoring the
complete cycle of increasing and removal of the test force, hardness values equivalent to traditional hardness
values can be determined. More significantly, additional properties of the material, such as its indentation
modulus and elasto-plastic hardness, can also be determined. All these values can be calculated without the
need to measure the indent optically. Furthermore, by a variety of techniques, the instrumented indentation
test allows to record hardness and modulus depth profiles within a, probably complex, indentation cycle.
ISO 14577 (all parts) has been written to allow a wide variety of post test data analysis.
v
DRAFT International Standard ISO/DIS 14577-2:2024(en)
Metallic materials — Instrumented indentation test for
hardness and materials parameters —
Part 2:
Verification and calibration of testing machines
1 Scope
This part of ISO 14577 specifies the method of verification and calibration of testing machines for carrying
out the instrumented indentation test in accordance with ISO 14577-1.
It describes a direct verification method for checking the main functions of the testing machine and an
indirect verification method suitable for the determination of the repeatability of the testing machine. There
is a requirement that the indirect method be used in addition to the direct method and for the periodic
routine checking of the testing machine in service.
It is a requirement that the indirect method of verification of the testing machine be carried out independently
for each test method.
This part of ISO 14577 is also applicable for transportable testing machines.
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 376, Metallic materials — Calibration of force-proving instruments used for the verification of uniaxial
testing machines
ISO 3878, Hardmetals — Vickers hardness test
ISO 14577-1, Metallic materials — Instrumented indentation test for hardness and materials parameters —
Part 1: Test method
ISO 14577-3, Metallic materials — Instrumented indentation test for hardness and materials parameters —
Part 3: Calibration of reference blocks
3 General conditions
3.1 Preparation
The machine shall be designed in such a way that it can be verified.
Before verification and calibration of the testing machine, it shall be checked to ensure that the conditions
laid down in 3.2 to 3.4 are met.
3.2 Functional installation
The testing machine shall be configured to operate in compliance with and shall be installed in an
environment that meets the requirements of this part of ISO 14577, ISO 14577-1, and, where applicable,
ISO/DIS 14577-2:2024(en)
ISO 14577-3. The testing machine shall be protected from vibrations. For testing in the micro and nano
ranges, the testing machine shall also be protected from air currents and temperature fluctuations (see 7.1.
in ISO 14577-1).
The influence of environment on the data, i.e. the noise floor, shall be estimated by performing a low force
(e.g. equivalent to the usual initial contact force) indentation on a CRM and analysing the displacement
over time. The force variability is the indent stiffness (obtained from force removal curve) multiplied by
the standard deviation of the displacement once any background drift in mean displacement has been
subtracted. These uncertainties shall then be included in the total combined uncertainty tests as calculated
in Clause 8 and Annex H in ISO 14577-1, clause 4.
3.3 Indenter
In order to get repeatable measurements of the force/indentation depth data set, the indenter holder shall
be firmly mounted into the testing machine.
The indenter holder should be designed in such a way that its contribution to the overall compliance is
minimized (see Annex A).
3.4 Application of the test force
The test force shall be applied and removed without shock or vibration that can significantly affect the test
results. It shall be possible to verify the process of increasing, holding, and removal of the test force.
4 Direct verification and calibration
4.1 General
4.1.1 Direct verification and calibration shall be carried out at the temperature of use, which is typically
held at a stable value over the time of measurement in the range 10 °C to 35 °C, but preferably in the range
(23 ± 5) °C. If a range of operating temperatures is required, then direct calibration and verification should
be carried out at suitable points over that temperature range to determine the calibration validity as
a function of temperature. If necessary, a calibration correction function or a set of calibrations valid at
specific operating temperatures can be determined.
4.1.2 The instruments used for direct calibration and verification shall be traceable to National Standards
as far as available.
4.1.3 Direct verification and calibration involves
a) calibration of the test force,
b) calibration of the displacement measuring device,
c) verification and calibration of the machine compliance,
d) verification of the indenter,
e) calibration and verification of the indenter area function, if the indentation depth is less than 6 µm, and
f) verification of the test cycle.
4.2 Calibration of the test force
4.2.1 Each range of force used shall be calibrated over the whole force range for both application
and removal of the test force. A minimum of 16 evenly distributed points in the test force range shall be
calibrated, i.e. 16 during application and 16 during removal of the test force. The procedure shall be repeated
ISO/DIS 14577-2:2024(en)
at least three times and the average calibration value shall be used. The maximum difference in calibration
values shall not exceed half of the tolerances given in Table 1.
4.2.2 The test force shall be measured by a traceable method, for example, the following:
a) measuring by means of an elastic proving-device in accordance with class 1, or better of, ISO 376;
b) balancing against a force, accurate to within ±0,2 % applied by means of calibrated masses with
mechanical advantage;
c) electronic balance with a suitable accuracy of 0,1 % of the minimum calibrated test force or 10 µg
(0,1 µN) for the nano range.
For each measured point used for calibration, the difference between the measured and the nominal test
force shall be within the tolerances given in Table 1.
Table 1 — Tolerances for test forces
Range of the test force Tolerances
F
N %
F ≥ 2 1,0
0,001 ≤ F < 2 1,0
a
F < 0,001 2,5
a
For the nano range, a tolerance of 1 % is strongly recommended.
4.3 Calibration of the displacement measuring device
4.3.1 The resolution required for the displacement measuring device of the testing machine depends on
the size of the smallest indentation depth being measured. For the micro range, this value is by definition
h = 0,2 µm; for the macro range it is typically larger than 2 µm.
The scale of the displacement measuring device shall be graduated to permit a resolution of indentation
depth measurement in accordance with Table 2.
4.3.2 The displacement measuring device of the testing machine shall be calibrated for every range used
by means of a suitable method and a corresponding system. The device shall be calibrated at a minimum of
16 points in each direction evenly distributed throughout its indentation displacement range. The procedure
shall be repeated three times.
Some testing machines have a long-stroke displacement measuring device where the location of the
indentation range of the displacement measuring device varies to suit the sample. For these types of
machines, it shall be verified that the calibration is valid in accordance with table 2 for all of the used
measurement positions in the travel range.
The following methods are recommended for the measurement of the relative displacement of the indenter:
laser interference method, inductive method, capacitive method, and piezotranslator method.
For each measured point used for calibration, the difference between the measured and the nominal
displacement shall be within the tolerances given in Table 2.
ISO/DIS 14577-2:2024(en)
Table 2 — Resolution and tolerances of the displacement measuring device
Resolution of the displacement meas-
Range of application uring device Tolerances
nm
Macro ≤100 1 % of h
Micro ≤10 1 % of h
a
Nano ≤1 2 nm
a
For the nano range, a tolerance of <1 % of h (displacement of the measuring device) is strongly recommended.
4.3.3 Changes in temperature are commonly a dominant source of displacement drift. To minimize
thermally induced displacement drift, the temperature of the instrument shall be maintained such that the
displacement drift rate remains constant over the time period of one calibration cycle. The drift rate shall
be measured during, immediately before, or immediately after each calibration cycle, e.g. by monitoring
displacement during a suitable hold period. The displacement calibration data shall be corrected for thermal
drift and the product of variation in drift rate and the duration of one calibration cycle shall be less than
the tolerance given in Table 2. The drift rate uncertainty shall be included in the displacement calibration
uncertainty calculation.
4.4 Verification and calibration of the machine compliance
4.4.1 General
See Annex D and ISO 14577-1, Annex C.
This verification and calibration shall be carried out after the test force and the displacement measuring
system have been calibrated in accordance with 4.2 and 4.3.
4.4.2 Procedure
The calibration and verification of machine compliance is carried out by the measurement of indentation
modulus at a minimum of five different test forces. Method 3 as described in Annex D is recommended. In
all cases, a suitable Certified Reference Material (CRM) shall be mounted into the instrumented indentation
test system in the same way as future test samples will be mounted. This is to ensure that the CRM provides
a faithful reproduction of each particular total machine compliance.
The compliance of the testing machine can be affected by the particular construction and mounting of an
indenter and also the method used to mount a sample. For instance, mounting in plastics (e.g. PVC) can
introduce an extra compliance into the measurement loop. The verification and calibration of machine
compliance should be performed using the indenter that will be used for subsequent measurements.
For contact depths, h > 6 µm, it is not necessary to take into account the real contact area function. For the
c
verification and calibration of the machine compliance, a reference material with certified indentation
modulus, independent from the indentation depth, shall be used. A material with a high ratio of EH/
IT IT
(such as tungsten) is recommended. The range for the test force is defined by the minimum test force that
correlates to 6 µm contact depth and the maximum possible test force of the testing machine. Large
indentation depths have the advantage that errors in the area function are likely to be smaller; however,
care shall be taken that the test is not biased by pile-up in the reference material. The measured compliance
of the indentation shall then be compared with the calculated compliance for the indentation using the
certified value of modulus. To recalibrate machine compliance, the product of the applied force and the
detected difference in machine compliance is applied to the displacement data to refine the estimate of
contact depth and, therefore, the machine compliance estimate at each force. This process is iterated until
self-consistent values of machine compliance and contact depth are reached.
For indentation depths, <6 µm, the method above shall be applied, except that the actual area of contact,
as calculated from the calibrated indenter area function, shall be used to calculate the contact compliance
using the certified modulus of the CRM.
ISO/DIS 14577-2:2024(en)
In many nano and micro range instruments, the machine compliance value is independent of force. However,
if this is not the case, then a machine compliance function can be determined using the above procedure
but a wider range of forces. The range for the test forces is defined by the indentation depths, >0,5 µm, and
the maximum test force of the testing machine or the maximum test force for which no unusual test piece
response (e.g. pile-up of metals or cracking of ceramics or glasses) occurs.
If the machine compliance is recalibrated, then an indirect validation shall be performed before use.
The calibration procedures detailed in Annex D require the use of reference materials (see ISO 14577-3)
that shall be isotropic and homogeneous. It is assumed that the indentation modulus and Poisson’s ratio are
independent of the indentation depth.
4.5 Calibration and verification of the indenter
4.5.1 General
The indenter used for the indentation test shall be calibrated. Evidence that the indenter complies with
the requirements of this part of ISO 14577 shall be fulfilled by a calibration certificate from a qualified
calibration laboratory and evidence from the most recent indirect verification that the indenter area
function has not changed. The latter shall be provided using the verification methods described in Annex B
and suitable certified reference materials. All specified indenter geometry parameters shall be measured
and incorporated into the calibration certificate.
The indenter shall meet the following requirements:
— The material shall be homogeneous and fully dense;
— The elastic modulus and Poisson ratio of the indenter material shall be known;
— The indenter shall be significantly harder than the sample material. The indenter should have a higher
elastic modulus than the sample material.
If the angle of the indenter deviates from the nominal value for an ideal geometry of the indenter, the average
of certified angles for that indenter should be used in all applicable calculations at contact depths h > 6 µm.
c
NOTE An error of 0,2° in the Vickers angle of 136° (2α) results in a 1 % systematic error in area.
Indenters for use in the nano range and in the micro range shall have their area function calibrated over
the relevant indentation depth ranges of use. The indenter performance shall be verified periodically (see
Clause 6).
Where non-diamond indenters are used, the values of elastic modulus and Poisson ratio shall be obtained
and used instead of the diamond values in the appropriate analyses.
The angle for pyramidal and conical indenters shall be measured within the indentation depth ranges given
in Table 3 and illustrated in Figure 1.
Table 3 — Values for the measuring ranges for the angle of pyramidal and conical indenters
Dimensions in micrometres
Indentation depth Macro range Micro range
h 6 0,2
Specified max. indenta-
h 200
tion depth
ISO/DIS 14577-2:2024(en)
Figure 1 — Illustration of measuring ranges given in Table 3
4.5.2 Vickers indenter
4.5.2.1 The four faces of the right square-based diamond pyramid shall be smooth and free from surface
defects and contaminants that significantly alter the area function. For notes on cleaning of the indenter
surface, see also ISO 14577-1, Annex D.
The surface roughness of the indenter has a similar effect on measurement uncertainty as test piece
roughness. When testing in the nano range, the indenter surface finish should be taken into consideration.
4.5.2.2 The angle between the opposite faces of the vertex of the diamond pyramid shall be 136° ± 0,3°
(see Figure 2) (α = 68,0° ± 0,2°).
The angle shall be measured in the range between h and h (see Table 3 and Figure 1). The geometry and
1 2
finish of the indenter shall be controlled over the whole calibrated indentation depth range, i.e. from the
indenter tip, h , to the maximum calibrated indentation depth, h .
0 2
4.5.2.3 The angle between the axis of the diamond pyramid and the axis of the indenter holder (normal to
the seating surface) shall not exceed 0,5°.
4.5.2.4 The four faces shall meet at a point. The maximum permissible length of the line of conjunction
between opposite faces is given in Table 4 (see also Figure 3).
4.5.2.5 The radius of the tip of the indenter shall not exceed 0,5 µm for the micro range (see Figure 4).
4.5.2.6 The verification of the shape of the indenter shall be carried out using microscopes or other
suitable devices. If the indenter is used for testing in the micro or nano range, a verification by a closed loop
controlled atomic-force-microscope (AFM) is recommended.
NOTE An area function derived by indentation in a certified reference material has high uncertainty in the nano range.
Table 4 — Maximum permissible length of the line of conjunction
Range of the contact depth Maximum permissible length
of the line of conjunction
µm µm
h > 30 1
c
a
30 ≥ h > 6 0,5
c
b
h ≤ 6 ≤ 0,5
c
a
This can be assumed to have been achieved when there is no detectable conjunction when the indenter is verified by an
optical microscope at 400 × magnification.
b
This shall be included when the correction of the shape of the indenter is taken into account; see ISO 14577-1, C.2.
ISO/DIS 14577-2:2024(en)
Figure 2 — Angle of the Vickers diamond pyramid
Key
a line of conjunction
Figure 3 — Line of conjunction on the tip of the indenter — Schematic
Figure 4 — Radius of the tip of the indenter
4.5.3 Berkovich, modified Berkovich, and corner cube indenters
4.5.3.1 In practice, there are two types of Berkovich pyramidal diamond indenters in common use. The
Berkovich indenter (see Reference [5]) is designed to have the same surface area as a Vickers indenter at any
given indentation depth. The modified Berkovich indenter (see Reference [11]) is designed to have the same
projected area as the Vickers indenter at any given indentation depth.
ISO/DIS 14577-2:2024(en)
4.5.3.2 The three faces of the triangular based diamond pyramid shall be smooth and free from surface
defects and from contaminations that significantly alter the area function. For notes on cleaning of the
surface, see also ISO 14577-1, Annex D.
The surface roughness of the indenter has a similar effect on measurement uncertainty as does test piece
roughness. When testing in the nano range, the indenter surface finish should be taken into consideration.
4.5.3.3 The radius of the tip of the indenter shall not exceed 0,5 µm for the micro range and shall not
exceed 0,2 µm for the nano range (see Figure 4).
4.5.3.4 The angle between the axis of the diamond pyramid and the three faces is designated α. The angle
between edges of the triangular base of the diamond pyramid shall be 60° ± 0,3° (see Figure 5).
a
α = 65,03° ± 0,30° for Berkovich indenter.
α = 65,27° ± 0,30° for modified Berkovich indenter.
α = 35,26° ± 0,30° for corner cube indenters.
Figure 5 — Angle of the Berkovich and corner cube indenters
NOTE The most common Berkovich geometry in use is the modified Berkovich indenter. This is often for
convenience referred to as a “Berkovich” indenter.
4.5.3.5 The verification of the shape of the indenter shall be carried out using microscopes or suitable
devices. If the indenter is used for testing in the micro and nano range, a measurement by a closed-loop
controlled atomic-force-microscope (AFM) is recommended.
NOTE An area function derived by indentation in a certified reference material has high uncertainty in the nano range.
4.5.4 Ball indenters
The balls shall have a certified geometry. Batch certification methods are sufficient. The certificate shall
show the diameter of the average value of at least three measured points of different positions. If any value
differs from the permissible values of the nominal diameter (see Table 5), the ball (and/or the batch) shall
not be used as an indenter.
ISO/DIS 14577-2:2024(en)
Table 5 — Tolerances for ball indenters
Dimensions in millimetres
Ball diameter Tolerance
10 ±0,005
5 ±0,004
2,5 ±0,003
1 ±0,003
0,5 ±0,003
4.5.5 Spheroconical indenters
The characteristics of spheroconical indenters shall be as given in Table 6 (see also Figure 6).
Table 6 — Tolerances for spheroconical indenters
Feature Tolerance
R ≤ 50 µm ±0,25 R
av av
a
500 µm > R > 50 µm ±0,1 R
av av
Cone included angle, 2α
a
120° ±5°
90° ±5°
60° ±5°
Cone flank angle, α
60° ±5°
45° ±2,5°
30° ±2,5°
NOTE Centreline of cone to centreline of mount is within 0,01 mm.
a
Rockwell diamond indenters (see ISO 6508-2) fulfil this requirement.
The instantaneous radius of curvature, R(h), of the spherical cap at any indentation depth, h, measured from
the point of first contact shall not vary by more than a factor of two from the average radius, R , as given by
av
the condition in Formula (1):
0,5 ≤ |R(h)/R | ≤ 2 (1)
av
Indenters with a spherical tipped cone shape are useful for many applications. These indenters are normally
made from diamond but can also be made from other materials, e.g. ruby, sapphire, or hardmetal (WC-Co
cemented carbide). They are intended to indent only with the spherical tip. If Hertzian contact mechanics
are being used to interpret the indentation response, the value used for the indenter radius is critical. It is,
therefore, recommended that the shape of each indenter be determined directly by a suitable measurement
system, or indirectly by indentation into a certified reference material.
Surface roughness, Ra, should be minimized. Roughness causes an uncertainty in the actual area of contact
and in the definition of the first contact point of the indenter with the test piece. Asperities have radii of
contact vastly different from the average radius of the spherical cap and, therefore, behave very differently.
If possible, the Ra of the diamond surface should be less than 1/20 of the usual indentation depth for an
indenter.
NOTE Geometry suggests that the depth of the spherical cap, h , on a cone of included angle, 2α, and radius, R , is
s av
given by Formula (2):
h = R [1 − sin(α)] (2)
s av
In practice, there is a gradual transition from spherical cap to cone geometry that is hard to specify. Given this and the
uncertainties in R and α allowed (see Table 6), caution should be exercised whenever the depth exceeds 0,5 h .
av s
ISO/DIS 14577-2:2024(en)
a
α angle between the axis of the cone and its face.
h depth of the spherical cap.
s
h local depth.
R(h) local radius.
R radius of the spherical cap.
av
Figure 6 — Representation of the features of spheroconical indenters
4.6 Verification of the indenter area function
4.6.1 General
See ISO 14577-1, Annex C.
4.6.2 Procedure
Procedures for the determination of indenter area function are given in Annex B.
The direct verification of the indenter area function consists of a comparison of the measured indenter
area function with a documented indenter area function determined for the newly certified and calibrated
indenter.
NOTE The indenter area function and machine compliance correction can be determined simultaneously using an
iterative procedure and multiple reference materials (see Reference [8]).
When the area function is used for the measurement of a reference material and the modulus result deviates
more than 5 % from the specified reference value, the area function shall be recalibrated.
ISO/DIS 14577-2:2024(en)
A pyramidal indenter should no longer be used in the nano- or micro-ranges when the tip radius significantly
exceeds the respective values given in 4.5.2 and 4.5.3. In the macro range the indenter should be discarded
when the face angle significantly deviates from the respective values given in 4.5.2 and 4.5.3.
A ball or spherical indenter shall be discarded when the calibrated tip radius deviates more than 3 times the
specified tip radius tolerances in table 5 and 6.
4.7 Verification of the testing cycle
The testing cycle (application of the test force, holding of the maximum test force, and removal of the test
force) shall be measured with a tolerance of 0,1 s. The duration of each part of the testing cycle during the
experiment shall meet the requirements of ISO 14577-1.
5 Indirect verification
5.1 General
Indirect verification should be carried out at the temperature of use by means of reference blocks calibrated
in accordance with ISO 14577-3, or within the temperature at for which the calibration of the reference
blocks is valid, typically (23 ± 5) °C. Indirect verification using a reference material shall be made to ensure
the direct verification is valid and that no damage or contamination has occurred to the indenter tip.
Before measuring on the reference block, it is recommended to inspect and clean the indenter first using
the procedure recommended in ISO 14577-1, Annex D. If the results of these initial indentations indicate
the presence of contamination or damage, then the indenter should be cleaned again before further trial
indentations are made. If after further cleaning, indentation into the reference material still indicates the
presence of contamination or damage, then inspection with an optical microscope at a magnification of
400x is recommended. Detection of sub-microscopic damage or contamination is possible using appropriate
microscopy of indents or the indenter. Where damage is detected, the indenter shall be replaced.
For an indirect validation decision tree, see Figure 7. The procedures for the determination of the machine
compliance, C , and the area function, A (h ), calibration/verification shall be implemented before a new
F p c
indenter is used. If, after applying the currently valid correction for machine compliance and indentation
area function (obtained using a variable epsilon and a radial displacement correction, ISO 14577-1, Annex I),
a measured value from a reference block deviates from the certified value of the test piece by more than the
maximum permissible amount of the limits specified in Table 7 (see Note 2) and repetition of the procedure
using a newly verified and certified indenter and valid machine compliance correction corresponding to
that indenter) also fails to reproduce the certified value, the testing machine shall be serviced and a full,
direct calibration be performed.
NOTE 1 The use of control charts is a sensitive way to determine changes in performances before a control limit is
breached (see Annex C).
ISO/DIS 14577-2:2024(en)
Figure 7 — Flow chart of decisions and actions to be taken for indirect verification
NOTE 2 A reference indenter is a calibrated indenter used infrequently and only for checking the instrument and
test indenter performance through indirect validation comparison.
5.2 Procedure
5.2.1 The indirect verification shall be carried out at two or more test forces that are an order of
magnitude different or at least span the range of indentation forces or depths being measured. For tests with
indentation depths <6 µm, this provides some verification of the contact area function. Indirect verification
ISO/DIS 14577-2:2024(en)
should be carried out on at least two reference blocks (CRMs) whose certified values differ significantly, e.g.
by a factor of two.
For the indirect verification in the nano
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