EN ISO 14577-1:2026

SLOVENSKI STANDARD
01-oktober-2026
Nadomešča:
SIST EN ISO 14577-1:2015
Kovinski materiali - Instrumentirano vtiskanje pri preskušanju trdote in drugih
lastnosti materialov - 1. del: Preskusna metoda (ISO 14577-1:2026)
Metallic materials - Instrumented indentation test for hardness and materials parameters
- Part 1: Test method (ISO 14577-1:2026)
Metallische Werkstoffe - Instrumentierte Eindringprüfung zur Bestimmung der Härte und
anderer Werkstoffparameter - Teil 1: Prüfverfahren (ISO 14577-1:2026)
Matériaux métalliques - Essai de pénétration instrumenté pour la détermination de la
dureté et de paramètres des matériaux - Partie 1: Méthode d'essai (ISO 14577-1:2026)
Ta slovenski standard je istoveten z: EN ISO 14577-1:2026
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.

EN ISO 14577-1
EUROPEAN STANDARD
NORME EUROPÉENNE
June 2026
EUROPÄISCHE NORM
ICS 77.040.10 Supersedes EN ISO 14577-1:2015
English Version
Metallic materials - Instrumented indentation test for
hardness and materials parameters - Part 1: Test method
(ISO 14577-1:2026)
Matériaux métalliques - Essai de pénétration Metallische Werkstoffe - Instrumentierte
instrumenté pour la détermination de la dureté et de Eindringprüfung zur Bestimmung der Härte und
paramètres des matériaux - Partie 1: Méthode d'essai anderer Werkstoffparameter - Teil 1: Prüfverfahren
(ISO 14577-1:2026) (ISO 14577-1:2026)
This European Standard was approved by CEN on 13 May 2026.

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, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,
Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Türkiye 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
© 2026 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 14577-1:2026 E
worldwide for CEN national Members.

Contents Page
European foreword . 3

European foreword
This document (EN ISO 14577-1:2026) has been prepared by Technical Committee ISO/TC 164
"Mechanical testing of metals" in collaboration with Technical Committee CEN/TC 459/SC 1 “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 December 2026, and conflicting national standards
shall be withdrawn at the latest by December 2026.
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 14577-1:2015.
Any feedback and questions on this document should be directed to the users’ national standards
body/national committee. A complete listing of these bodies can be found on the CEN website.
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, France, Germany, Greece, Hungary, Iceland,
Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Republic of
North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Türkiye and the
United Kingdom.
Endorsement notice
The text of ISO 14577-1:2026 has been approved by CEN as EN ISO 14577-1:2026 without any
modification.
International
Standard
ISO 14577-1
Third edition
Metallic materials — Instrumented
2026-06
indentation test for hardness and
materials parameters —
Part 1:
Test method
Matériaux métalliques — Essai de pénétration instrumenté pour
la détermination de la dureté et de paramètres des matériaux —
Partie 1: Méthode d'essai
Reference number
ISO 14577-1:2026(en) © ISO 2026

ISO 14577-1:2026(en)
© ISO 2026
All rights reserved. Unless otherwise specified, or required in the context of its implementation, 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
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii
ISO 14577-1:2026(en)
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 2
4 Symbols and designations . 2
5 Principle . 4
6 Testing machine. 5
7 Test piece . 5
8 Procedure . 6
9 Uncertainty of the results . 9
10 Test report . 10
Annex A (normative) Materials parameters determined from the force/indentation depth data
set .12
Annex B (informative) Types of control use for the indentation process .25
Annex C (normative) Machine compliance and indenter area function .26
Annex D (informative) Notes on diamond indenters .28
Annex E (normative) Influence of the test piece surface roughness on the accuracy of the results.29
Annex F (informative) Correlation of indentation hardness H to Vickers hardness .30
IT
Annex G (normative) Determination of drift and minimizing creep influence .32
Annex H (informative) Estimation of uncertainty of the calculated values of hardness and
materials parameters .34
Annex I (normative) Calculation of radial displacement correction .39
Bibliography .43

iii
ISO 14577-1:2026(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 document 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).
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent
rights in respect thereof. As of the date of publication of this document, ISO had not received notice of (a)
patent(s) which may be required to implement this document. However, implementers are cautioned that
this may not represent the latest information, which may be obtained from the patent database available at
www.iso.org/patents. ISO shall not be held responsible for identifying any or all such patent rights.
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of 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 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, in collaboration with the European Committee for Standardization (CEN) Technical
Committee CEN/TC 459/SC1, Test methods for steel (other than chemical analysis), in accordance with the
Agreement on technical cooperation between ISO and CEN (Vienna Agreement).
This third edition cancels and replaces the second edition (ISO 14577-1:2015), which has been technically
revised.
The main changes are as follows:
— Better specification of the approach speed of the tip.
— Addition of a loading method with constant strain rate.
— Change of order of hardness definitions: first H then HM.
IT
— Better proposals for cleaning the tip.
— Differentiation between contact area under load and in unloaded state.
— Complete reformulation of normative Annex I for radial displacement correction.
A list of all parts in the ISO 14577 series can be found on the ISO website.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.

iv
ISO 14577-1:2026(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.
Although the indentation modulus (E ) value obtained in this test method is not directly equivalent to
IT
Young’s modulus or the orientation specific elastic modulus of the material indented, E is, however,
IT
equivalent to the isotropic Hill average of the elastic plane strain modulus of the material when there is no
pile up and no residual stress.
ISO 14577 (all parts) has been written to allow a wide variety of post-test data analysis.
Part 1 of ISO 14577 specifies the method of indentation test for determination of instrumented indentation
hardness and material properties.

v
International Standard ISO 14577-1:2026(en)
Metallic materials — Instrumented indentation test for
hardness and materials parameters —
Part 1:
Test method
1 Scope
This document specifies the method of instrumented indentation test for determination of hardness and
other materials parameters for the following three ranges:
— macro range: 2 N ≤ F ≤ 30 kN;
— micro range: 2 N > F; h > 0,2 µm;
— nano range: h ≤ 0,2 µm.
For the nano range, the mechanical deformation strongly depends on the real shape of indenter tip and the
calculated material parameters are significantly influenced by the contact area function of the indenter used
in the testing machine. Therefore, careful calibration of both instrument and indenter shape is required
in order to achieve an acceptable reproducibility of the materials parameters determined with different
machines.
The macro and micro ranges are distinguished by the test forces in relation to the indentation depth.
Attention is drawn to the fact that the micro range has an upper limit given by the test force (2 N) and a
lower limit given by the indentation depth of 0,2 µm.
The determination of hardness and other material parameters is given in the normative Annex A.
At high contact pressures, damage to the indenter is possible. For test pieces with very high hardness
and modulus of elasticity, permanent indenter deformation can occur and can be detected using suitable
reference materials. Indentations that result in damage or permanent deformation of the indenter are
excluded from the scope of this test method.
This test method can also be applied to thin metallic and non-metallic coatings and non-metallic materials.
In this case, it is recommended that the specifications in the relevant standards be taken into account (see
also 7.3 and ISO 14577-4).
The analysis methods of this standard assume that materials behave like ideal materials. Any deviation
(internal stress, pile-up, sink-in, densification, phase transitions, cracks) will result in additional
uncertainties. This becomes especially important if comparisons shall be done to material parameters,
obtained with other methods.
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 14577-2:2026, Metallic materials — Instrumented indentation test for hardness and materials parameters
— Part 2: Verification and calibration of testing machines

ISO 14577-1:2026(en)
ISO/IEC Guide 98-3:2008, Uncertainty of measurement — Part 3: Guide to the expression of uncertainty in
me a s ur ement (GUM: 1995)
3 Terms and definitions
No terms and definitions are listed in this document.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
4 Symbols and designations
For the purposes of this document, the symbols and designations in Table 1 shall be applied (see also Figure 1
and Figure 2).
Table 1 — Symbols and designations
Symbol Designation Unit
A (h ) Projected area of contact under load of the indenter at distance h from the tip mm
p c c
Projected area of contact in unloaded state of the indenter at distance h from the mm
c
A (h )
p,UL c
tip
A (h) Surface area of the indenter at distance h from the tip in unloaded state mm
s
C Indentation creep %
IT
Total measured compliance of the contact (dh/dF tangent to the force removal nm/mN
C
T
curve at maximum test force)
C Machine compliance nm/mN
F
C Compliance of the contact after correction for machine compliance nm/mN
S
E Indentation modulus of the test piece GPa
IT
Reduced plane strain modulus of the contact (combination of test piece and in- GPa
E
r
denter plane strain moduli)
F Test force N
F Maximum test force N
max
h Indentation depth under applied test force mm
h Contact depth of the indenter with the test piece at F mm
c max
h Maximum indentation depth at F mm
max max
h Permanent indentation depth after removal of the test force mm
p
Point of intersection of the tangent c to curve b at F with the indentation mm
max
h
r
depth-axis as identified on Figure 1
H Indentation hardness GPa
IT
HM Martens hardness GPa
Martens hardness, determined from the slope of the increasing GPa
HM
s
force/indentation depth curve
GPa
HM
Martens hardness, determined from the first derivative of h vs F
diff
ν Poisson’s ratio of the test piece
s
r Radius of spherical indenter mm
R Indentation relaxation %
IT
NOTE 1 To avoid very long numbers, the use of multiples or sub-multiples of the units can be used.
2 2
NOTE 2 The continued use of the unit N/mm is allowed. 1 MPa = 1 N/mm .

ISO 14577-1:2026(en)
TTabablele 1 1 ((ccoonnttiinnueuedd))
Symbol Designation Unit
W Elastic reverse deformation work of indentation N⋅m
elast
W Total mechanical work of indentation N⋅m
total
Cone semi-angle or angle of facet to the indentation axis for pyramidal °
α
indenters
Maximum angle between the contact surface and the indenter for calculation of °
θ
radial displacement
η Ratio W /W %
IT elast total
NOTE 1 To avoid very long numbers, the use of multiples or sub-multiples of the units can be used.
2 2
NOTE 2 The continued use of the unit N/mm is allowed. 1 MPa = 1 N/mm .

a
Application of the test force.
b
Removal of the test force.
c
Tangent to curve b at F .
max
Figure 1 — Schematic representation of the test procedure

ISO 14577-1:2026(en)
Key
a
Indenter.
b
Surface of residual plastic indentation in a test piece that has a “perfectly plastic” response.
c
Surface of test piece at maximum indentation depth and test force.
θ maximum angle between the test piece surface and the indenter
Figure 2 — Schematic representation of the cross section of indentation
in the case of material “sink-in”
5 Principle
Continuous recording of the force and the depth of indentation permits the determination of hardness
and material properties (see Figure 1 and Figure 2). The measured values of hardness and other material
parameters shall be determined in accordance with Annex A. An indenter consisting of a material harder
than the material under test shall be used (i.e. the indenter shall not permanently deform and shall not be
damaged as a result of indentation). For hardness testing the following shapes and materials can be used:
a) indenter shaped as an orthogonal pyramid with a square base and with an angle α = 68° between the
axis of the diamond pyramid and one of the faces (Vickers pyramid; see Figure A.1);
b) pyramid with triangular base (e.g. modified Berkovich pyramid with an angle α = 65,27° between the
axis of the diamond pyramid and one of the faces; see Figure A.1);
c) ball indenter (especially for the determination of the elastic behaviour of materials);
d) spherical tipped conical indenter.
This document does not preclude the use of other indenter geometries; however, care should be taken when
interpreting the results obtained with such indenters. Diamond is the preferred material but other materials
like sapphire may also be used for example to avoid chemical reaction between the indenter and the test
piece, provided the above mechanical requirements of the indenter are met.
For indentation modulus testing, the indenter geometries for hardness testing are strongly recommended
but, in principle, any geometry indenter may be used provided that the area function is known and the area
function is monotonically increasing with indentation depth.
NOTE Due to the crystal structure of diamond, indenters that are intended to be spherical are often polyhedrons
and do not have an ideal spherical shape.
The test procedure can either be force-controlled or displacement-controlled. The test force, F, the
corresponding indentation depth, h, and time are recorded during the whole test procedure. The result of
the test is the data set of the test force and the relevant indentation depths as a function of time (see Figure 1
and Annex B).
For a reproducible determination of the force and corresponding indentation depth, the zero point for the
force/indentation depth measurement shall be assigned individually for each test (see 7.3).

ISO 14577-1:2026(en)
Where time-dependent effects are being measured
— using the force-controlled method, the test force is kept constant over a specified period and the change
of the indentation depth is measured as a function of the holding time of the test force (see Figures A.3
and B.1), and
— using the indentation depth-controlled method, the indentation depth is kept constant over a specified
period and the change of the test force is measured as a function of the holding time of the indentation
depth (see Figures A.4 and B.2).
The two kinds of control mentioned give essentially different results in the segment b of the curves in
Figure B.1 a) and Figure B.2 b) or in Figure B.1 b) and Figure B.2 a).
6 Testing machine
6.1 The testing machine shall have the capability of applying predetermined test forces or displacements
within the required scope and shall fulfil the requirements of ISO 14577-2.
6.2 The testing machine shall have the capability of measuring and reporting applied force, indentation
displacement and time throughout the testing cycle.
6.3 The testing machine shall have the capability of compensating for the machine compliance and of
utilizing the appropriate indenter area function according to Annex C and ISO 14577-2:2026, 5.5 and 5.6.
6.4 Indenters for use with testing machines can have various shapes, as specified in ISO 14577-2 (for
further information on indenters, see Annex D).
6.5 The testing machine shall operate at a temperature within the permissible range specified in 7.1 and
shall maintain its calibration within the limits specified in ISO 14577-2:2026, Clause 5.
7 Test piece
7.1 The test shall be carried out on a region of the test surface that allows the determination of the force/
indentation depth curve for the respective indentation range within the required uncertainty. The contact
area shall be free of fluids or lubricants except where this is essential for the performance of the test, in
which case, this shall be described in detail in the test report. Care shall be taken that extraneous matter
(e.g. dust particles) is not incorporated into the contact.
Generally, provided the surface is free from obvious surface contamination, cleaning procedures should be
avoided. If cleaning is required, it shall be limited to the following methods to minimize damage:
— application of a dry, oil-free, filtered gas stream;
— application of a subliming particle stream of CO (but keeping the surface temperature above the dew
point);
— rinsing with a solvent (which is chemically inert to the test piece) and then setting it to dry.
If these methods fail and the surface is sufficiently robust, wipe the surface with a lint-free tissue soaked in
solvent to remove trapped dust particles, after which, the surface shall be rinsed in a solvent as above.
Ultrasonic methods are known to create or increase damage to surfaces and coatings and should only be
used with caution.
Surface finish has a significant influence on the test results that depends upon the relative size of the
indentation depth, h, with respect to the arithmetic mean deviation roughness, Ra. The relative size of these
parameters shall conform to the limits given in Annex E.

ISO 14577-1:2026(en)
The test piece surface shall be normal to the test force direction. The angle difference between test surface
normal and indenter axis shall be less than 1°. The effect of surface tilt should be included in the uncertainty
calculation.
The sample should be free from magnetism. Test pieces capable of becoming magnetised should be checked
for magnetism and demagnetised before testing, if possible. Precautions should be taken to avoid the effect
of magnetism on the measuring system.
7.2 If necessary, preparation of the test surface shall be carried out in such a way that any alteration of the
surface hardness and/or surface residual stress (e.g. due to heat or cold-working) is minimized.
Due to the small indentation depths in the micro and nano range, special precautions shall be taken during
the test piece preparation. When polishing is needed, a polishing process that is suitable for the particular
materials shall be used.
Electropolishing is a recommended preparation method that can remove a work hardened surface layer.
However, care should be taken that the surface roughness does not exceed the limits given in this standard.
7.3 The test piece thickness shall be large enough (or indentation depth small enough) such that the test
result is not influenced by the test piece support. For hardness and modulus measurements, the test piece
thickness shall be at least 10 times the indentation depth or 3 times the indentation diameter (see 8.7),
whichever is greater. For modulus measurements a sample thickness larger than 30 times the indentation
depth is recommended. For measurements of thinner samples, it is recommended to follow the analysis
described in ISO 14577-4 for coatings.
When testing coatings, the coating thickness should be considered as the test piece thickness. For testing
thin samples or coatings, see ISO 14577-4 for better testing procedures.
NOTE The above are empirically based limits based on hardness testing. The effect of test piece thickness on the
elastic modulus result is not the same as the effect on the hardness result. The exact limits of influence of support on
test piece depend on the geometry of the indenter used and the materials properties of the test piece and support.
8 Procedure
8.1 The temperature of the test shall be recorded. Tests shall be performed within ±10 °C of the
temperature of the instrument calibration.
The temperature stability during a test is more important than the actual test temperature. Any calibration
correction applied shall be reported along with the additional calibration uncertainty. It is recommended
that tests, particularly in the nano and micro ranges, be performed in controlled conditions, in the range
(23 ± 5) °C and (45 ± 10) % relative humidity.
The individual tests, however, shall be carried out at stable temperature conditions because of the
requirement of high depth measuring accuracy. This means that:
— the test pieces shall have reached the ambient temperature before testing,
— the testing machine shall have reached a stable working temperature (operating manual should be
consulted),
— the ambient, instrument, and test temperature shall be within the range for which the machine calibration
is valid, and
— other external influences causing temperature changes during individual test have been controlled.
To minimize thermally induced displacement drift, the temperature of the testing machine shall be
adequately maintained over the time period of one testing cycle, or a displacement drift shall be measured
and corrected. A decision tree to assist in estimating the drift during the experiment is shown in Figure 3.
If the drift rate is significant, the displacement data shall be corrected by measuring the drift rate during
a hold at an applied force as close to zero force as is practicable or during a hold at a suitable place in the

ISO 14577-1:2026(en)
force removal curve in accordance with Annex G and ISO 14577-2:2026, 5.3.3). In all cases where the drift
rate would influence the maximum indentation depth by more than 1 % within the total indentation cycle
time, the drift rate shall be corrected (see tolerances in ISO 14577-2:2026, Table 2 and 5.3.3). If a contact in
the fully elastic regime can be obtained, a hold at initial contact is preferred. In this way, material influences
(creep, visco-plasticity, cracking) can be minimized. When the measurement is significantly longer than
the hold period for thermal drift measurement it is recommended to measure the thermal drift before and
after the experiment and to correct the displacement using the average of the two drift rates. The difference
between the two drift rates is an estimate of the drift rate uncertainty. The uncertainty due to the drift, or
in the drift correction used, shall be reported.
To determine the drift of surface referenced instruments, contact between the reference indenter and the
sample surface shall be elastic. This may be determined by calculation.
NOTE The significance of a particular drift rate upon the measurement depends upon the range of the indentation
and the type of application.
Figure 3 — Decision tree to assist in estimating thermal drift using a constant force hold period
8.2 The test piece shall be firmly supported such that there is no significant change in the testing machine
compliance. The test piece shall either be placed on a support that is rigid in the direction of indentation or
be fixed in a suitable test piece holder. The contact surfaces between test piece support and test piece holder
shall be free from extraneous matter, which can increase the compliance (reduce the stiffness) of the test
piece support.
If the sample is supported by materials or mounting methods other than those used when determining the
machine compliance, then the different elastic response of these materials and mounting methods can cause
additional compliance. A certified reference material, mounted in the same way as the sample, should be

ISO 14577-1:2026(en)
used to check if the mounting method affects the frame compliance. A mounting problem is indicated if the
measured modulus differs from the certified value and changes with the applied force.
8.3 The zero point for the measurement of the force/indentation depth curve shall be assigned individually
to each test data set by one of the following methods. It represents the first touch of the indenter with the
test piece surface. The uncertainty in the zero-point shall be reported. The uncertainty in the assigned zero
point should not exceed 1 % of maximum indentation depth for the macro and micro ranges. The zero point
uncertainty for the nano range can exceed 1 %, in which case the value shall be estimated.
a) Method 1: The zero-point is calculated by extrapolation of a fitted function to the force-application
curve (see curve a in Figure 1); a power law fit with the exponent as a fitting parameter constrained to
be 1 ≤ m ≤ 2 is recommended. The fit shall be applied to values within the range from the first recorded
data point to not more than 5 % of the maximum indentation depth. The fitted data shall not contain a
change in indentation response such as the onset of plastic yielding. It is recommended that data are
recorded during approach (before contact) so that they can be used for zero point determination. The
uncertainty of the calculated zero point results from the fit parameters, the fitting function and the
length of extrapolation. The uncertainty is calculated as the standard error of the intercept of the fit
function at zero force with the depth axes.
NOTE 1 The first part of the indentation curve can be affected by vibration or other noise.
b) Method 2: The zero-point is the touch point determined from the first increase of either the test force
or the contact stiffness. At this touch point, the step size in force or displacement shall be small enough
such that the zero point uncertainty is less than the limit required.
−4
NOTE 2 Typical small force steps values for the macro range are 10 F and for the micro and nano range
max
less than 5 µN.
8.4 The testing cycle can be either force-controlled or displacement-controlled. The controlled parameters
can vary either continuously or step by step. A full description of all parts of the testing cycle shall be stated
in the report, including the following:
a) nature of the control (i.e. force or displacement control and whether a stepped or continuous change in
the controlled parameters);
b) maximum force (or displacement);
c) force application (or displacement) function;
d) length and position of each hold period;
e) data logging frequency (or number of data points).
NOTE An example cycle for nano and micro ranges is the following: force application time, 30 s; hold at F , 30 s;
max
force removal 10 s. A 60 s hold period to measure thermal drift can also be required (see Annex G).
The time taken for a test can influence the results obtained. In order to obtain comparable test results the
time taken for the test shall be recorded and reported.
8.5 The test force shall be applied, without shock or vibration that can significantly affect the test results,
until either the applied test force or the indentation displacement attains the specified value. Force and
displacement shall be recorded at the time intervals stated in the report.
During the determination of the touch point of the indenter with the test piece, the approach speed of the
indenter shall be sufficiently low in order that the mechanical properties of the surface are not changed by
the impact. For macro range indentations, it should not exceed 2 µm/s. The approach speed immediately
before contact divided by the acquisition rate of the displacement signal should not be larger than 1 nm in
the nano and 5 nm in the micro range. It is recommended that the approach speed and the acquisition rate is
recorded and reported.
ISO 14577-1:2026(en)
Force/indentation depth/time data sets are directly comparable only if the same indenter and test cycle
(profile) is used. The test profile shall be specified in terms of either applied test force or indentation
displacement as a function of time. The three most common single cycles are:
a) constant applied test force rate
b) constant indentation displacement rate.
c) constant strain rate.
More complex multi cycle procedures like load-partial unload cycles may also be used to get information at
different test forces in one measurement position.
Using more complex multi cycle procedures, like load-partial unload cycles in an indentation that increases
incrementally in force to obtain many unloading curves referenced to the same zero point, it is possible to
get information about contact compliance at different test forces at a single test site.
The rate of applied test force removal is subject to the requirements that: a sufficient number of data points
for any subsequent analysis are recorded during applied test force removal, and that the total creep and any
residual creep rate is within acceptable limits (see Annex G).
If the drift rate is significant (see 8.1 and Annex G), the depth data shall be corrected by use of the measured
drift rate.
8.6 Throughout the test, the testing machine shall be protected from shock and vibration, air movements
and variations in temperature, which can significantly influence the test result.
8.7 It is important that the test results are not affected by the presence of an interface, free surface or by
any plastic deformation introduced by a previous indentation in a series. The effect of any of these depends
on the indenter geometry and the materials properties of the test piece. Indentations shall be at least three
times their indentation diameter away from interfaces or free surfaces and the minimum distance between
indentations shall be at least five times the largest indentation diameter. For modulus measurements a
distance from the sample edge of at least 20 times the indentation diameter is recommended.
The indentation diameter is the in-plane diameter at the surface of the test piece of the circular impression
of an indent created by a spherical indenter. For non-circular impressions, the indentation diameter is the
diameter of the smallest circle capable of enclosing the indentation. Occasional cracking can occur at the
corners of the indentation. When this occurs, the indentation diameter should enclose the crack.
The minimum distances specified between indentations or between an indentation and the edge of the
sample are best applicable to ceramic materials and metals such as iron and its alloys. For softer or very
brittle materials, it is recommended that separations of at least 10 indentation diameters be used.
If in doubt, it is recommended that the values from the first indentation are compared with those from
subsequent indentations in a series. If there is a significant difference in a nominally homogeneous sample,
the indentations might be too close and the distance should be increased. A factor of two increases in
separation is suggested.
It can be desirable to measure thin coatings in cross-section (e.g. to avoid problems due to surface roughness).
In this case, there might not be enough coating thickness to meet the minimum spacing requirements as
specified above. Smaller spacing can be used if there is experimental evidence that this does not significantly
influence the force/indentation depth/time data sets with respect to correctly spaced indentations on
similar test pieces with thicker coatings.
9 Uncertainty of the results
A complete evaluation of the uncertainty shall be carried out in accordance with ISO/IEC Guide 98-3. A
detailed description of the method of evaluation of uncertainty is given in Annex H.

ISO 14577-1:2026(en)
The approach calculates a combined uncertainty from individual contributions. These can be grouped into
random and systematic uncertainties. Individual parameters can contribute one or both types of uncertainty
to the total measurement uncertainty. For example, the uncertainty in measured displacement can have
a random component due to the resolution of the scale used and vibrational noise, etc., plus a systematic
component due to the displacement sensor calibration uncertainty. The following sources of uncertainty
shall be considered:
— zero point assignation;
— measurement of force and displacement (i.e. noise floor, including effects of ambient vibrations and
magnetic field strength changes etc.);
— fitting of the force-removal curve;
— thermal drift rate;
— contact area due to surface roughness;
— force, displacement calibration;
— testing machine compliance;
— indenter area function calibration values;
— calibration drift due to uncertainty in temperature of testing machine and time since last calibration;
— tilt of test surface.
It might not always be possible to individually quantify all of the identified contributions to the random
uncertainty. In this case, an estimate of standard uncertainty can be obtained from the statistical analysis
of repeated indentations. Care should be taken that systematic standard uncertainties that can contribute to
the random standard uncertaint
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