prEN ISO 148-1
(Main)Metallic materials - Charpy pendulum impact test - Part 1: Test method (ISO/DIS 148-1:2025)
Metallic materials - Charpy pendulum impact test - Part 1: Test method (ISO/DIS 148-1:2025)
ISO 148-1:2016 specifies the Charpy (V-notch and U-notch) pendulum impact test method for determining the energy absorbed in an impact test of metallic materials. This part of ISO 148 does not cover instrumented impact testing, which is specified in ISO 14556.
Annexes B and C are based on ASTM E23 and are used with the permission of ASTM International, 100 Barr Harbor Drive, P.O. Box C700, West Conshohocken, PA 19428-2959, USA.
Metallische Werkstoffe - Kerbschlagbiegeversuch nach Charpy - Teil 1: Prüfverfahren (ISO/DIS 148‑1:2025)
Matériaux métalliques - Essai de flexion par choc sur éprouvette Charpy - Partie 1: Méthode d'essai (ISO/DIS 148-1:2025)
ISO 148-1:2016 spécifie la méthode d'essai de flexion par choc sur éprouvette Charpy (avec entaille en V et avec entaille en U) pour déterminer l'énergie absorbée lors d'un essai de flexion par choc des matériaux métalliques. La présente partie de l'ISO 148 ne couvre pas l'essai de flexion par choc instrumenté, qui est spécifié dans l'ISO 14556.
Les Annexes B et C sont fondées sur l'ASTM E23 et sont utilisées avec la permission de ASTM International, 100 Barr Harbor Drive, P.O. Box C700, West Conshohocken, PA 19428-2959, États-Unis.
Kovinski materiali - Udarni preskus po Charpyju - 1. del: Preskusna metoda (ISO/DIS 148-1:2025)
General Information
Relations
Standards Content (Sample)
SLOVENSKI STANDARD
01-december-2025
Kovinski materiali - Udarni preskus po Charpyju - 1. del: Preskusna metoda
(ISO/DIS 148-1:2025)
Metallic materials - Charpy pendulum impact test - Part 1: Test method (ISO/DIS 148-
1:2025)
Metallische Werkstoffe - Kerbschlagbiegeversuch nach Charpy - Teil 1: Prüfverfahren
(ISO/DIS 148-1:2025)
Matériaux métalliques - Essai de flexion par choc sur éprouvette Charpy - Partie 1:
Méthode d'essai (ISO/DIS 148-1:2025)
Ta slovenski standard je istoveten z: prEN ISO 148-1
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 148-1
ISO/TC 164/SC 4
Metallic materials — Charpy
Secretariat: ANSI
pendulum impact test —
Voting begins on:
Part 1: 2025-10-28
Test method
Voting terminates on:
2026-01-20
Matériaux métalliques — Essai de flexion par choc sur éprouvette
Charpy —
Partie 1: Méthode 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 has not been edited by the ISO Central Secretariat.
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STANDARDS MAY ON OCCASION HAVE TO
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Reference number
ISO/DIS 148-1:2025(en)
DRAFT
ISO/DIS 148-1:2025(en)
International
Standard
ISO/DIS 148-1
ISO/TC 164/SC 4
Metallic materials — Charpy
Secretariat: ANSI
pendulum impact test —
Voting begins on:
Part 1:
Test method
Voting terminates on:
Matériaux métalliques — Essai de flexion par choc sur éprouvette
Charpy —
Partie 1: Méthode 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 has not been edited by the ISO Central Secretariat.
IN ADDITION TO THEIR EVALUATION AS
BEING ACCEPTABLE FOR INDUSTRIAL,
© ISO 2025
TECHNOLOGICAL, COMMERCIAL AND
USER PURPOSES, DRAFT INTERNATIONAL
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Published in Switzerland Reference number
ISO/DIS 148-1:2025(en)
ii
ISO/DIS 148-1:2025(en)
Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
3.1 Definitions pertaining to the machine .1
3.2 Definitions pertaining to energy .1
3.3 Definitions pertaining to test piece .2
4 Symbols and abbreviated terms. 2
5 Principles of the test . 3
6 Test pieces . 4
6.1 General .4
6.2 Notch geometry .4
6.2.1 V-notch . .4
6.2.2 U-notch .4
6.3 Tolerance of the test pieces .5
6.4 Preparation of the test pieces .5
6.5 Marking of the test pieces .5
7 Test equipment . 5
7.1 General .5
7.2 Installation and verification .5
7.3 Striker .5
7.4 Verification of temperature measuring system .5
8 Test procedure . 5
8.1 General .5
8.2 Friction measurement .5
8.3 Determination of absorbed energy K .7
8.4 Test temperature .7
8.5 Test piece transfer .7
8.6 Exceeding machine capacity .8
8.7 Incomplete fracture .8
8.8 Test piece jamming .8
8.9 Post-fracture inspection .8
9 Test report . 9
9.1 Mandatory information .9
9.2 Optional information .9
Annex A (informative) Self-centring tongs .13
Annex B (informative) Lateral expansion. 14
Annex C (informative) Shear Fracture Appearance .18
Annex D (informative) Absorbed energy vs. temperature curve and transition temperature .21
Annex E (informative) Measurement uncertainty of an absorbed energy value, K .23
Bibliography .29
iii
ISO/DIS 148-1:2025(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 World Trade Organization (WTO) principles in the
Technical Barriers to Trade (TBT) see the following URL: www.iso.org/iso/foreword.html.
The committee responsible for this document is ISO/TC 164, Mechanical testing of metals, Subcommittee
SC 4, Fatigue, fracture and toughness testing.
This fourth edition cancels and replaces the third edition (ISO 148-1:2016), which has been technically
revised.
ISO 148 consists of the following parts, under the general title Metallic materials — Charpy pendulum impact test:
— Part 1: Test method
— Part 2: Verification of testing machines
— Part 3: Preparation and characterization of Charpy V-notch test pieces for indirect verification of pendulum
impact machines
— Part 4: Testing of miniature Charpy test pieces (in preparation).
iv
DRAFT International Standard ISO/DIS 148-1:2025(en)
Metallic materials — Charpy pendulum impact test —
Part 1:
Test method
1 Scope
This part of ISO 148 specifies the Charpy (V-notch and U-notch) pendulum impact test method for
determining the energy absorbed in an impact test of metallic materials. This part of ISO 148 does not cover
[1]
instrumented impact testing, which is specified in ISO 14556 .
[2]
Annexes B and C are based on ASTM E23 and are used with the permission of ASTM International, 100
Barr Harbor Drive, P.O. Box C700, West Conshohocken, PA 19428-2959, USA.
2 Normative references
The following referenced documents, in whole or in part, are normatively referenced in this document and
are indispensable for the application of this document. For dated references, only the edition cited applies.
For undated references, the latest edition of the referenced document (including any amendments) applies.
ISO 148-2, Metallic materials — Charpy pendulum impact test — Part 2: Verification of testing machines
ISO 286-1, Geometrical product specifications (GPS) — ISO code system for tolerances on linear sizes — Part 1:
Basis of tolerances, deviations and fits
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1 Definitions pertaining to the machine
3.1.1
pendulum impact testing machine
testing machine equipped with a swinging hammer (pendulum) that is used to perform impact tests on
Charpy test pieces
Note 1 to entry: For the sake of simplicity, the term “machine” is often used in this document to generically indicate a
pendulum impact testing machine.
3.2 Definitions pertaining to energy
3.2.1
initial potential energy
potential energy
K
p
potential energy of the machine hammer prior to its release for the impact test, as determined by direct
verification
ISO/DIS 148-1:2025(en)
3.2.2
absorbed energy
K
energy required to break a test piece with a pendulum impact testing machine, after correction for friction
Note 1 to entry: The subscript V or U is used to indicate the notch geometry, that is: K or K . The number 2 or 8 is used
V U
as a subscript to indicate the radius of the striker, for example K .
V2
3.2.3
nominal initial potential energy
nominal energy
K
N
energy assigned by the manufacturer of the pendulum impact testing machine
3.2.4
total absorbed energy
K
T
total absorbed energy spent to break a test piece with a pendulum impact testing machine, which is not
corrected for any losses of energy
Note 1 to entry: It is equal to the difference in the potential energy from the starting position of the pendulum to the
end of the first half swing during which the test piece is broken.
3.3 Definitions pertaining to test piece
3.3.1
width
W
distance between the notched face and the opposite face
Note 1 to entry: See Figure 1.
Note 2 to entry: Prior to 2016, the distance between the notched face and the opposite face was specified as “height”.
Changing this dimension to “width” made this part of ISO 148 consistent with the terminology used in other ISO
fracture standards.
3.3.2
thickness
B
dimension perpendicular to the width and parallel to the notch
Note 1 to entry: See Figure 1.
Note 2 to entry: Prior to 2016, the dimension perpendicular to the width that is parallel to the notch was specified as
“width”. Changing this dimension to “thickness” made this part of ISO 148 consistent with the terminology used in
other ISO fracture standards.
3.3.3
length
L
largest dimension perpendicular to the notch
Note 1 to entry: See Figure 1.
4 Symbols and abbreviated terms
The symbols and designations applicable to this part of ISO 148 are indicated in Tables 1 and 2, and are
illustrated in Figure 2.
ISO/DIS 148-1:2025(en)
Table 1 — Symbols/abbreviated terms and their designations and units
Symbol Unit Designation
B mm thickness of test piece
α ° angle of fall of the pendulum
β ° angle of rise when the machine is operated without a test piece in position
β ° angle of rise when the machine is operated without a test piece in position and without
resetting the indication mechanism
th
β ° angle of rise recorded after the pendulum starts its 11 half swing and the indicating
mechanism has been moved to about 5 % of the scale-range capacity
[3]
GUM̶guide to the expression of uncertainty in measurement
L mm length of test piece
l m distance to the point of application of the force F from the axis of rotation
LE mm lateral expansion
K J absorbed energy (expressed as K , K , K , K , to identify specific notch geometries
V2 V8 U2 U8
and the radius of the striking edge)
K J indicated absorbed energy when the machine is operated without a test piece in posi-
tion
K J indicated absorbed energy when the machine is operated without a test piece in posi-
tion and without resetting the indication mechanism
th
K J indicated absorbed energy after the pendulum starts its 11 half swing and the indicat-
ing mechanism has been moved to about 5 % of the scale-range capacity
K J nominal initial potential energy assigned by the manufacturer
N
K J initial potential energy (potential energy)
p
K J total absorbed energy
T
K J absorbed energy for a V-notch test piece using a 2 mm striker
V2
K J absorbed energy for a V-notch test piece using an 8 mm striker
V8
K J absorbed energy for a U-notch test piece using a 2 mm striker
U2
K J absorbed energy for a U-notch test piece using an 8 mm striker
U8
M N·m moment equal to the product F·l
p J absorbed energy loss caused by pointer friction
p′ J absorbed energy loss caused by bearing friction and air resistance
p J correction of absorbed energy losses for an angle of rise β
β
SFA % shear fracture appearance
T °C transition temperature
t
W mm width of test piece
transition temperature defined at a specific value of absorbed energy;
T °C
t27
for example, 27 J
transition temperature defined at a particular percentage of the absorbed energy of the
T °C
t50 %US
upper shelf; for example, 50 %
transition temperature defined at a particular proportion of shear fracture;
T °C
t50 %SFA
for example, 50 %
transition temperature defined at a particular amount of lateral expansion;
T °C
t0,9
for example, 0,9 mm
5 Principles of the test
This test consists of breaking a notched test piece with a single blow from a swinging pendulum, under
the conditions defined in Clauses 6, 7 and 8. The notch in the test piece has a specified geometry and is
located in the middle between two supports, opposite to the location which is impacted in the test. The
ISO/DIS 148-1:2025(en)
energy absorbed in the impact test, the lateral expansion and the shear fracture appearance are normally
determined.
Because the Charpy test results of many metallic materials vary with temperature, tests shall be carried out
at a specified temperature. When this temperature is other than ambient, the test piece shall be heated or
cooled to that temperature, under controlled conditions.
The Charpy pendulum impact test is often used in routine, high-throughput pass/fail acceptance tests in
industrial settings. For these tests, it may not be important whether the test sample is completely broken,
partially broken, or simply plastically deformed and dragged through the anvils. In research, design, or
academic settings, the measured energy values are studied in more detail, in which case it can be highly
relevant whether the sample is broken or not.
It is important to note that not all Charpy test results can be directly compared. For example, the test can
be performed with hammers having strikers with different radii, or with different test piece configurations.
[4]
Tests performed with different strikers can give different results , and test results obtained from test
pieces having different notch configurations or cross section dimensions can also be different. This is why
not only the adherence to ISO 148 but also a clear and complete reporting of the type of instrument, the test
piece configuration and the details of the broken test pieces are crucial for comparability of results.
6 Test pieces
6.1 General
The standard test piece shall be 55 mm long and of square section, with 10 mm sides. In the centre of the
length, there shall be either a V-notch or a U-notch, as described in 6.2.1 and 6.2.2, respectively.
If the standard test piece cannot be obtained from the material, one of the subsize test pieces, having a
thickness of 7,5 mm, 5 mm or 2,5 mm (see Figure 2 and Table 2), shall be used, if not otherwise specified.
NOTE 1 For low energies (20 J or less), shims can be used to better position subsize test pieces relative to the centre
of strike in order to avoid excess energy absorption by the pendulum. For high energies (100 J or more), this might not be
as important. Shims can be placed on or under the test piece supports, with the result that the mid-thickness of the test
piece shall be 5 mm above the 10 mm supports. Shims can be temporarily fixed to the supports using tape or other means.
NOTE 2 Direct comparison of results is only of significance when made between test pieces of the same form and
[5]
dimensions .
When a heat-treated material is being evaluated, the test piece shall be finish-machined and notched after
the final heat treatment, unless it can be demonstrated that machining before heat treatment does not affect
test results.
6.2 Notch geometry
The notch shall be carefully prepared so that the root radius of the notch is free of machining marks which
could affect the absorbed energy.
The plane of symmetry of the notch shall be perpendicular to the longitudinal axis of the test piece
(see Figure 2).
6.2.1 V-notch
The V-notch shall have an included angle of 45° and a root radius of 0,25 mm; the ligament shall be 8 mm
[see Figure 2 a) and Table 2].
6.2.2 U-notch
The U-notch shall have a root radius of 1 mm and the ligament shall be 5 mm (unless otherwise instructed
by the customer or in product specifications) [see Figure 2 b) and Table 2].
ISO/DIS 148-1:2025(en)
6.3 Tolerance of the test pieces
The tolerances on the specified test piece and notch dimensions are shown in Figure 2 and Table 2.
6.4 Preparation of the test pieces
Preparation shall be executed in such a way that any alteration of the test piece, for example due to heating
or cold working, is minimized.
6.5 Marking of the test pieces
The test piece may be marked on any face not in contact with supports, anvils or striker and at a position
where plastic deformation and surface discontinuities caused by marking do not affect the absorbed energy
(see 8.8).
7 Test equipment
7.1 General
The measurements of the instrument and test piece details shall be traceable to national or international
standards. Equipment used for measurements shall be calibrated within prescribed intervals.
7.2 Installation and verification
The testing machine shall be installed and verified in accordance with ISO 148-2.
7.3 Striker
The striker geometry shall be specified as being either the 2 mm striker or the 8 mm striker. The radius of
the striking edge shall be shown as a subscript with the following designations: K or K and K or K .
V2 V8 U2 U8
Reference shall be made to the product specification for striker geometry guidance.
[4]
NOTE Tests carried out with 2 mm and 8 mm strikers can give different results .
7.4 Verification of temperature measuring system
It shall be demonstrated that the system used for measuring temperature has been verified at the test
temperature other than ambient or for a range containing the test temperature. Corrections shall be
applied for any known systematic errors, but with no consideration of the uncertainty of the temperature
measurement equipment.
8 Test procedure
8.1 General
The test piece shall lie squarely against the anvils of the testing machine, with the plane of symmetry of the
notch within 0,5 mm of the mid-plane between the anvils. It shall be struck by the striker in the plane of
symmetry of the notch and on the side opposite the notch (see Figure 1).
8.2 Friction measurement
The energy absorbed by friction shall be checked on every testing day prior to the first test. The friction
losses may be estimated as explained below, but other methods may also be applied.
NOTE The energy absorbed by friction includes, but is not limited to, air resistance, bearing friction and the
friction of the indicating pointer. Increases in friction on a machine can influence the measure of absorbed energy.
ISO/DIS 148-1:2025(en)
8.2.1 To determine the loss caused by pointer friction the machine is operated in the normal manner, but
without a test piece in position, and the angle of rise, β , or energy reading, K , is noted. A second test is then
1 1
carried out without resetting the indication pointer and the new angle of rise, β , or energy reading, K , is
2 2
noted. Thus, the loss due to friction in the indicating pointer during the rise is equal to
pM=−()coscββos (1)
when the scale is graduated in degrees, or
pK=−K (2)
when the scale is graduated in energy units.
NOTE 1 For machines without a pointer, this friction measurement is not necessary. In this case, β = β .
2 1
NOTE 2 The angles of rise β , β , and β are measured with respect to the vertical direction.
1 2 3
8.2.2 The procedure to determine the losses caused by bearing friction and air resistance for one half
swing is as follows.
After determining β or K , the pendulum is returned to its initial position. Without resetting the indicating
2 2
mechanism, release the pendulum without shock and vibration and permit it to swing 10 half swings. After
th
the pendulum starts its 11 half swing, move the indicating mechanism to about 5 % of the scale-range
capacity and record the value as β or K . The losses by bearing friction and air resistance for one half swing
3 3
are equal to
Mcos ββ−cos
()
′
p = (3)
when the scale is graduated in degrees, or
KK−
′
p = (4)
when the scale is graduated in energy units.
The number of swings can be changed at the discretion of machine users, and p' shall be corrected on account
of the applied number of swings.
NOTE 1 If it is required to take into account these losses in an actual test giving an angle of rise, β, the quantity can
be subtracted from the value of the absorbed energy.
β αβ+
pp=+ p′ (5)
β
β αβ+
Because β and β are nearly equal to α, the angle of fall, for practical purposes Formula (5) can be reduced to:
1 2
β αβ+
pp=+ p′ (6)
β
β 2α
For machines graduated in energy units, the value of β can be calculated as follows:
KK−
PT
β =−arccos 1 (7)
M
The total friction loss, p + p′, so measured, shall not exceed 0,5 % of the nominal energy, K . If it does, and it
N
is not possible to bring the friction loss within the tolerance by reducing the pointer friction, the bearings
shall be cleaned or replaced.
ISO/DIS 148-1:2025(en)
8.3 Determination of absorbed energy K
After measuring the total friction losses according to 8.2, the absorbed energy K is calculated as:
KM=−coscβαos −p (8)
()
β
when the scale is graduated in degrees, or
KK=− pp+ ′ (9)
()
T
when the scale is graduated in energy units.
8.4 Test temperature
8.4.1 Unless otherwise specified, tests shall be carried out at 23 °C ± 5 °C (ambient temperature). If a
temperature is specified, the test piece shall be conditioned to a temperature within ±2 °C.
8.4.2 For conditioning (heating or cooling) using a liquid medium, the test piece shall be positioned in a
container on a grid that is at least 25 mm above the bottom of the container and covered by at least 25 mm
of liquid, and be at least 10 mm from the sides of the container. The medium shall be constantly agitated
and brought to the specified temperature by any convenient method. The device used to measure the
temperature of the medium should be placed in the centre of the group of test pieces. The temperature of the
liquid medium shall be held at the specified temperature within ±2 °C and the test piece shall be maintained
in the medium for at least 5 min before the test piece is transferred to the impact position.
NOTE When a liquid medium is near its boiling point, evaporative cooling can dramatically lower the temperature
[6]
of the test piece during the interval between removal from the liquid and fracture .
8.4.3 For conditioning (heating or cooling) using a gaseous medium, the test piece shall be positioned in a
chamber at least 50 mm from the nearest surface. Individual test pieces shall be separated by at least 10 mm.
The medium shall be constantly circulated and brought to the specified temperature by any convenient
method. The device used to measure the temperature of the medium should be placed in the centre of the
group of test pieces. The temperature of the gaseous medium shall be held at the specified temperature
within ±2 °C and the test piece shall be maintained in the medium for at least 30 min before the test piece is
transferred to the impact position.
8.4.4 Other methods for heating or cooling are allowed, if the other pertinent requirements of 8.4.1, 8.4.2
and 8.4.3 are fulfilled.
8.5 Test piece transfer
When testing is performed at other than ambient temperature, not more than 5 s shall elapse between the
time the test piece is removed from the heating or cooling medium and the time it is impacted by the striker.
An exception is made if the difference between the ambient or instrument temperature and the test piece
temperature is less than 25 °C, in which case the time for test piece transfer shall be less than 10 s.
The maximum transfer times specified above only apply to standard test pieces. In the case of sub-size test
pieces, transfer times shall be appropriately minimized on account of the smaller size. It may be necessary
to establish a relationship between test piece temperature and transfer time for the specific test piece size
used. For the smallest sizes, in-situ cooling or heating techniques, where the test piece is conditioned at the
impact location, are recommended.
The transfer device shall be designed and used in such a way that the temperature of the test piece is
maintained within the permitted temperature range.
The parts of the device in contact with the test piece during transfer from the medium to the machine shall
be conditioned with the test pieces.
ISO/DIS 148-1:2025(en)
Care should be taken to ensure that the device used to centre the test piece on the anvils does not cause
the fractured ends of low-energy, high-strength test pieces to rebound off the device into the pendulum.
This pendulum/test piece interaction results in erroneously high indicated energy. It has been shown that
clearance between the end of a test piece in the test position and the centring device, or a fixed portion of
the machine, shall be equal to or greater than 13 mm to avoid the ends of the test pieces rebounding into the
pendulum during the test.
NOTE Self-centring tongs, similar to those shown in Annex A for V-notched test pieces, are often used to transfer
the test piece from the temperature-conditioning medium to the proper test position. Tongs of this nature eliminate
potential clearance problems due to interference between the fractured test piece halves and a fixed centring device.
8.6 Exceeding machine capacity
The absorbed energy, K, should not exceed 80 % of the initial potential energy, K . If the absorbed energy
p
exceeds this value, the absorbed energy shall be reported as approximate and it shall be noted in the test
report as exceeding 80 % of the machine capacity.
NOTE Ideally, an impact test would be conducted at a constant impact velocity. In a pendulum-type test, the
velocity decreases as the fracture progresses. For test pieces with impact energies approaching the capacity of the
machine, the velocity of the pendulum unduly decreases during fracture and test results may be affected.
8.7 Incomplete fracture
Test pieces do not always break into two pieces during the test.
For material acceptance testing, it is not required to report information concerning incomplete fracture.
For tests, other than material acceptance testing, it is required that incomplete fracture be reported.
NOTE 1 In the case where individual test pieces are not identified within test records, the group can be identified
as broken or unbroken.
NOTE 2 A test piece that is not fully separated in two half test pieces upon impact can be considered broken if the
two halves can be separated by pushing the hinged halves together without the aid of mechanical tools and without
fatiguing the test piece.
NOTE 3 A material acceptance test is a test which is used to assess a minimum acceptance requirement.
8.8 Test piece jamming
If a test piece jams in the machine, the results shall be disregarded and the machine thoroughly checked for
damage that would affect its state of calibration.
NOTE Jamming occurs when a broken test piece is caught between moving and non-moving parts of the testing
machine. It can result in significant energy absorption. Jamming can be differentiated from secondary strike marks,
because jamming is associated with a pair of opposing marks on the test piece.
8.9 Post-fracture inspection
If post-fracture inspection shows that any portion of the test piece identification marking is in a portion of
the test piece which is visibly deformed, the test result might not be representative of the material and this
shall be noted in the test report.
ISO/DIS 148-1:2025(en)
9 Test report
9.1 Mandatory information
The test report shall contain the following information or, when agreed by the customer, it shall be possible
to retrieve this information based on a traceable coding of the test report by the test laboratory:
a) reference to this part of ISO 148, i.e. ISO 148-1;
b) identification of the test piece;
c) size of the test piece, if other than the standard test piece;
d) temperature of the test or the conditioning temperature of the test pieces;
e) absorbed energy, K , K , K , or K , as appropriate;
V2 V8 U2 U8
f) whether the test piece, or the majority of test pieces in a group of test pieces were broken (not required
for material acceptance tests);
g) any abnormalities that could have affected the test.
9.2 Optional information
The test report may optionally include, in addition to the information in 9.1:
[7]
a) test piece orientation (see ISO 3785 );
b) initial potential energy of the testing machine, in joules;
c) lateral expansion (see Annex B);
d) shear fracture appearance (see Annex C);
e) absorbed energy/temperature curve (see D.1);
f) lateral expansion/temperature curve;
g) shear fracture appearance/temperature curve;
h) transition temperature(s) and the criteria used for its (their) determination (see D.2);
i) number of test pieces which were not completely broken in the test;
j) date (month and year) of the most recent full direct and indirect verifications;
k) measurement uncertainty of the absorbed energy (see Annex E).
ISO/DIS 148-1:2025(en)
Key
1 anvil
2 standardized test piece
3 test piece supports
4 shroud (optional – see NOTE below)
5 width of test piece, W
6 length of test piece, L
7 thickness of test piece, B
8 centre of strike
9 direction of pendulum swing
NOTE Shrouds can be used in U-type machines to prevent broken test pieces from rebounding against the
pendulum and causing jamming.
Figure 1 — Test piece terminology showing configuration of test piece supports and anvils
of a pendulum impact testing machine
ISO/DIS 148-1:2025(en)
a) V-notch geometry
b) U-notch geometry
NOTE For the symbols L, W, B and the numbers 1 to 5, refer to Table 2.
Figure 2 — Charpy pendulum impact test piece
ISO/DIS 148-1:2025(en)
Table 2 — Tolerances on specified test piece dimensions
V-notch test piece U-notch test piece
Symbol
Machining tolerance Machining tolerance
Designation or
Nominal Nominal
Tolerance Tolerance
number
dimension dimension
a a
class class
Length of test piece L 55 mm ±0,60 mm js15 55 mm ±0,60 mm js15
Width of test piece W 10 mm ±0,075 mm js12 10 mm ±0,11 mm js13
c
Thickness of test B 10 mm ±0,11 mm js13 10 mm ±0,11 mm js13
piece
— standard test 10 mm ±0,11 mm js13 10 mm ±0,11 mm js13
piece 7,5 mm ±0,11 mm js13 7,5 mm ±0,11 mm —
— subsize test piece 5 mm ±0,06 mm js12 5 mm ±0,06 mm —
— subsize test piece 2,5 mm ±0,05 mm js12 — — —
— subsize test piece
Angle of notch 1 45° ±2° — — — —
Ligament 2 8 mm ±0,075 mm js12 5 mm ±0,09 mm js13
Notch root radius 3 0,25 mm ±0,025 mm — 1 mm ±0,07 mm js12
d d
Notch position 4 27,5 mm ±0,42 mm js15 27,5 mm ±0,42 mm js15
(centering)
Angle between notch 90° ±2° — 90° ±2° —
length and longitudi-
nal axis of test piece
Angle between adja- 5 90° ±2° — 90° ±2° —
cent longitudinal faces
of test piece
Surface roughness on Ra < 2 μm < 2 μm
notched and opposite
b
surfaces
a
In accordance with ISO 286-1.
b
The test pieces shall have a surface roughness better than Ra 2 µm on the notched surface and on the opposite surface, while
surface roughness shall be better than 4 µm on the remaining surfaces (except for the test piece ends).
c
If another thickness (2 mm or 3 mm) is specified, the corresponding tolerances shall also be specified.
d
For machines with automatic centring of the test piece, it is recommended that the tolerance be taken as ±0,165 mm instead
of ±0,42 mm.
ISO/DIS 148-1:2025(en)
Annex A
(informative)
Self-centring tongs
Tongs similar to the example shown in Figure A.1 are often used to transfer the test piece and properly
position it in the pendulum impact testing machine.
Dimensions in millimetres
Test piece thickness A B
10 1,60 to 1,70 1,52 to 1,65
7,5 1,17 to 1,25 1,10 to 1,23
5 0,74 to 0,80 0,69 to 0,81
2,5 0,35 to 0,40 0,32 to 0,45
a
Steel pieces silver soldered to tongs parallel to each other.
Figure A.1 — Centring tongs for Charpy V-notch test pieces
ISO/DIS 148-1:2025(en)
Annex B
(informative)
Lateral expansion
B.1 General
A measure of the ability of the material to resist fracture when subjected to triaxial stresses, such as those
at the root of the notch in a Charpy test piece, is the amount of deformation that occurs at this location. The
deformation in this case is contraction. Because of the difficulties in measuring this deformation, even after
fracture, the expansion that occurs at the opposite end of the fracture plane is customarily measured and
used as a proxy for the contraction. Lateral expansion measurements can be required based on agreement
between manufacturer and customer.
B.2 Procedure
The method of measuring lateral expansion should take into account the fact that the fracture plane seldom
bisects the point of maximum expansion on both sides of a test piece. One half of a broken test piece might
include the maximum expansion for both sides, one side only, or neither. The techniques used should
therefore provide an expansion value, equal to the sum of the higher of the two values obtained for each
side, by measuring the two halves separately or together. The amount of expansion on each side of each half
shall be measured relative to the plane defined by the undeformed portion of the side of the test piece (see
Figure B.1). Contact and non-contact methods can be used for these measurements.
Lateral expansion may be measured by using a gauge similar to that shown in Figures B.2 and B.3. First,
check the sides perpendicular to the notch to ensure that no burrs were formed on these sides during impact
testing; if such burrs exist, they shall be removed, for example by rubbing with an emery cloth, making sure
that the protrusions to be measured are not rubbed during the removal of the burr. Next, place the half-
test pieces, together or separately, so that the surfaces originally opposite the notch are facing one another.
Take one or both half-test pieces (see Figure B.1) and press firmly against the reference supports, with the
protrusions against the gauge anvil. Note the reading, and th
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