EN ISO 148-2:2008

SLOVENSKI STANDARD
01-april-2009
1DGRPHãþD
SIST EN 10045-2:1996
SIST EN 10045-2:1996/AC1:1997
Kovinski materiali - Udarni preskus po Charpyju - 2. del: Preverjanje preskusnih
naprav (ISO 148-2:2008)
Metallic materials - Charpy pendulum impact test - Part 2: Verification of testing
machines (ISO 148-2:2008)
Metallische Werkstoffe - Kerbschlagbiegeversuch nach Charpy - Teil 2: Prüfung der
Prüfmaschinen (Pendelschlagwerke) (ISO 148-2:2008)
Matériaux métalliques - Essai de flexion par choc sur éprouvette Charpy - Partie 2:
Vérification des machines d'essai (mouton-pendule) (ISO 148-2:2008)
Ta slovenski standard je istoveten z: EN ISO 148-2:2008
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.

EUROPEAN STANDARD
EN ISO 148-2
NORME EUROPÉENNE
EUROPÄISCHE NORM
December 2008
ICS 77.040.10
English Version
Metallic materials - Charpy pendulum impact test - Part 2:
Verification of testing machines (ISO 148-2:2008)
Matériaux métalliques - Essai de flexion par choc sur Metallische Werkstoffe - Kerbschlagbiegeversuch nach
éprouvette Charpy - Partie 2: Vérification des machines Charpy - Teil 2: Prüfung der Prüfmaschinen
d'essai (mouton-pendule) (ISO 148-2:2008) (Pendelschlagwerke) (ISO 148-2:2008)
This European Standard was approved by CEN on 19 November 2008.
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 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 Management Centre has the same status as the
official versions.
CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Cyprus, Czech Republic, Denmark, Estonia, Finland,
France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal,
Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
Management Centre: Avenue Marnix 17, B-1000 Brussels
© 2008 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 148-2:2008: E
worldwide for CEN national Members.

Contents Page
Foreword .3

Foreword
This document (EN ISO 148-2:2008) has been prepared by Technical Committee ISO/TC 164 "Mechanical
testing of metals" in collaboration with Technical Committee ECISS/TC 1 "Steel - Mechanical testing" 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 June 2009, and conflicting national standards shall be withdrawn at
the latest by June 2009.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. CEN [and/or CENELEC] shall not be held responsible for identifying any or all such patent rights.
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, Cyprus, Czech
Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia,
Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain,
Sweden, Switzerland and the United Kingdom.
Endorsement notice
The text of ISO 148-2:2008 has been approved by CEN as a EN ISO 148-2:2008 without any modification.

INTERNATIONAL ISO
STANDARD 148-2
Second edition
2008-12-15
Metallic materials — Charpy pendulum
impact test —
Part 2:
Verification of testing machines
Matériaux métalliques — Essai de flexion par choc sur éprouvette
Charpy —
Partie 2: Vérification des machines d'essai (mouton-pendule)

Reference number
ISO 148-2:2008(E)
©
ISO 2008
ISO 148-2:2008(E)
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ii © ISO 2008 – All rights reserved

ISO 148-2:2008(E)
Contents Page
Foreword. iv
Introduction . v
1 Scope . 1
2 Normative references . 2
3 Terms and definitions. 2
3.1 Definitions pertaining to the machine . 2
3.2 Definitions pertaining to energy. 3
3.3 Definitions pertaining to test pieces. 4
4 Symbols and abbreviated terms . 4
5 Testing machine. 6
6 Direct verification. 6
6.1 General. 6
6.2 Foundation/installation . 6
6.3 Machine framework . 6
6.4 Pendulum. 7
6.5 Anvil and supports . 11
6.6 Indicating equipment. 11
7 Indirect verification by use of reference test pieces. 12
7.1 Reference test pieces used . 12
7.2 Absorbed energy levels . 12
7.3 Requirements for reference test pieces . 12
7.4 Limited direct verification . 12
7.5 Bias and repeatability. 13
8 Frequency of verification . 13
9 Verification report. 14
9.1 General. 14
9.2 Direct verification. 14
9.3 Indirect verification. 14
10 Uncertainty . 14
Annex A (informative) Measurement uncertainty of the result of the indirect verification of a
Charpy pendulum impact machine. 21
Annex B (informative) Measurement uncertainty of the results of the direct verification of a
Charpy pendulum impact testing machine . 25
Annex C (informative) Direct method of verifying the geometric properties of pendulum impact
testing machines using a jig. 31
Bibliography . 38

ISO 148-2:2008(E)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies
(ISO member bodies). The work of preparing International Standards is normally carried out through ISO
technical committees. Each member body interested in a subject for which a technical committee has been
established has the right to be represented on that committee. International organizations, governmental and
non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the
International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
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.
ISO 148-2 was prepared by Technical Committee ISO/TC 164, Mechanical testing of metals, Subcommittee
SC 4, Toughness testing — Fracture (F), Pendulum (P), Tear (T).
This second edition cancels and replaces the first edition (ISO 148-2:1998), which has been technically
revised.
ISO 148 consists of the following parts, under the general title Metallic materials — Charpy pendulum impact
test:
⎯ Part 1: Test method
⎯ Part 2: Verification of testing machines
⎯ Part 3: Preparation and characterization of Charpy V-notch test pieces for indirect verification of
pendulum impact machines
iv © ISO 2008 – All rights reserved

ISO 148-2:2008(E)
Introduction
The suitability of a pendulum impact testing machine for acceptance testing of metallic materials has usually
been based on a calibration of its scale and verification of compliance with specified dimensions, such as the
shape and spacing of the anvils supporting the specimen. The scale calibration is commonly verified by
measuring the mass of the pendulum and its elevation at various scale readings. This procedure for
evaluation of machines had the distinct advantage of requiring only measurements of quantities that could be
traced to national standards. The objective nature of these traceable measurements minimized the necessity
for arbitration regarding the suitability of the machines for material acceptance tests.
However, sometimes two machines that had been evaluated by the direct-verification procedures described
above, and which met all dimensional requirements, were found to give significantly different impact values
when testing test pieces of the same material. This difference was commercially important when values
obtained using one machine met the material specification, while the values obtained using the other machine
did not. To avoid such disagreements, some purchasers of materials added the requirement that all pendulum
impact testing machines used for acceptance testing of material sold to them must be indirectly verified by
testing reference test pieces supplied by them. A machine was considered acceptable only if the values
obtained using the machine agreed, within specified limits, with the value furnished with the reference test
pieces.
INTERNATIONAL STANDARD ISO 148-2:2008(E)

Metallic materials — Charpy pendulum impact test —
Part 2:
Verification of testing machines
1 Scope
This part of ISO 148 covers the verification of the constructional elements of pendulum-type impact testing
machines. It is applicable to machines with 2 mm or 8 mm strikers used for pendulum impact tests carried out,
for instance, in accordance with ISO 148-1.
It can analogously be applied to pendulum impact testing machines of various capacities and of different
design.
Impact machines used for industrial, general or research laboratory testing of metallic materials in accordance
with this part of ISO 148 are referred to as industrial machines. Those with more stringent requirements are
referred to as reference machines. Specifications for the verification of reference machines are found in
ISO 148-3.
This part of ISO 148 describes two methods of verification.
a) The direct method, which is static in nature, involves measurement of the critical parts of the machine to
ensure that it meets the requirements of this part of ISO 148. Instruments used for the verification and
calibration are traceable to national standards. Direct methods are used when a machine is being
installed or repaired, or if the indirect method gives a non-conforming result.
b) The indirect method, which is dynamic in nature, uses reference test pieces to verify points on the
measuring scale.
A pendulum impact testing machine is not in compliance with this part of ISO 148 until it has been verified by
both the direct and indirect methods and meets the requirements of Clauses 6 and 7.
The requirements for the reference test pieces are found in ISO 148-3.
This part of ISO 148 takes into account the total energy absorbed in fracturing the test piece using an indirect
method. This total absorbed energy consists of
⎯ the energy needed to break the test piece itself, and
⎯ the internal energy losses of the pendulum impact testing machine performing the first half-cycle swing
from the initial position.
NOTE Internal energy losses are due to
⎯ air resistance, friction of the bearings of the rotation axis and of the indicating pointer of the pendulum which can
be determined by the direct method (see 6.4.5), and
⎯ shock of the foundation, vibration of the frame and pendulum for which no suitable measuring methods and
apparatus have been developed.
ISO 148-2:2008(E)
2 Normative references
The following referenced documents 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 148-1, Metallic materials — Charpy pendulum impact test — Part 1: Test method
ISO 148-3, Metallic materials — Charpy pendulum impact test — Part 3: Preparation and characterization of
Charpy V-notch test pieces for indirect verification of pendulum impact machines
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
anvil
portion of the machine that serves to properly position the test piece for impact with respect to the striker and
the test piece supports, and supports the test piece under the force of the strike
3.1.2
base
that part of the framework of the machine located below the horizontal plane of the supports
3.1.3
centre of percussion
that point in a body at which, on striking a blow, the percussive action is the same as if the whole mass of the
body were concentrated at the point
NOTE When a simple pendulum delivers a blow along a horizontal line passing through the centre of percussion,
there is no resulting horizontal reaction at the axis of rotation.
See Figure 4.
3.1.4
centre of strike
that point on the striking edge of the pendulum at which, in the free hanging position of the pendulum, the
vertical edge of the striker meets the upper horizontal plane of a test piece of half standard height (i.e. 5 mm)
or equivalent gauge bar resting on the test piece supports
See Figure 4.
3.1.5
industrial machine
pendulum impact machine used for industrial, general, or most research-laboratory testing of metallic
materials
NOTE 1 These machines are not used to establish reference values.
NOTE 2 Industrial machines are verified using the procedures described in this part of ISO 148.
3.1.6
reference machine
pendulum impact testing machine used to determine certified values for batches of reference test pieces
2 © ISO 2008 – All rights reserved

ISO 148-2:2008(E)
3.1.7
striker
portion of the pendulum that contacts the test piece
NOTE The edge that actually contacts the test piece has a radius of 2 mm (the 2 mm striker) or a radius of 8 mm (the
8 mm striker).
See Figure 2.
3.1.8
test piece supports
portion of the machine that serves to properly position the test piece for impact with respect to the centre of
percussion of the pendulum, the striker and the anvils
See Figures 2 and 3.
3.2 Definitions pertaining to energy
3.2.1
total absorbed energy
K
T
total absorbed energy required to break a test piece with a pendulum impact testing machine, which is not
corrected for any losses of energy
NOTE 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 (see 6.3).
3.2.2
initial potential energy
potential energy
K
P
difference between the potential energy of the pendulum hammer prior to its release for the impact test, and
the potential energy of the pendulum hammer at the position of impact, as determined by direct verification
NOTE See 6.4.2.
3.2.3
absorbed energy
K
energy required to break a test piece with a pendulum impact testing machine, after correction for friction
NOTE The letter V or U is used to indicate the notch geometry, that is KV or KU. The number 2 or 8 is used as a
subscript to indicate striker radius, for example KV .
3.2.4
calculated energy
K
calc
energy calculated from values of angle, length, and force measured during direct verification
3.2.5
nominal initial potential energy
nominal energy
K
N
energy assigned by the manufacturer of the pendulum impact testing machine
3.2.6
indicated absorbed energy
K
S
energy indicated by the display/dial of the testing machine, which may or may not need to be corrected for
friction to determine absorbed energy, K
ISO 148-2:2008(E)
3.2.7
reference absorbed energy
K
R
certified value of absorbed energy assigned to the test pieces used to verify the performance of pendulum
impact machines
3.3 Definitions pertaining to test pieces
3.3.1
height
distance between the notched face and the opposite face
3.3.2
width
dimension perpendicular to the height that is parallel to the notch
3.3.3
length
largest dimension perpendicular to the notch
3.3.4
reference test piece
impact test piece used to verify the suitability of pendulum impact testing machines by comparing the
indicated absorbed energy measured by that machine to the reference absorbed energy associated with the
test pieces
NOTE Reference test pieces are prepared in accordance with ISO 148-3.
4 Symbols and abbreviated terms
For the purposes of this document, the symbols and abbreviated terms given in Table 1 are applicable.
Table 1 — Symbols/abbreviated terms and their designations and units
Symbol/
abbreviated Unit Designation
a
term
B J Bias of the pendulum impact machine as determined through indirect verification
V
b J Repeatability
F N Force exerted by the pendulum when measured at a distance of l
F N Force exerted by the pendulum due to gravity
g
g Acceleration due to gravity
m/s
GUM — Guide to the expression of uncertainty in measurement
h m Height of fall of pendulum
H m Height of rise of pendulum
ISO — International Organization for Standardization
KV J Absorbed energy as measured in accordance with ISO 148 on a V-notched sample
KV J Certified KV value of the reference material used in the indirect verification
R
KV J Mean KV value of the reference test pieces tested for indirect verification
V
K J Nominal initial potential energy (nominal energy)
N
K J Initial potential energy (potential energy)
P
K J Reference absorbed energy of a set of Charpy reference test pieces
R
4 © ISO 2008 – All rights reserved

ISO 148-2:2008(E)
Table 1 (continued)
Symbol/
abbreviated Unit Designation
a
term
Absorbed energy (expressed as KV , KV , KU , KU , to identify specific notch
2 8 2 8
K J
geometries and striker radii)
K J Total absorbed energy
T
K J Indicated absorbed energy
S
K J Calculated energy
calc
Indicated absorbed energy or angle of rise when the machine is operated in the normal
K or b J or degree
1 1
manner without a test piece in position
Indicated absorbed energy or angle of rise when the machine is operated in the normal
K or b J or degree
2 2
manner without a test piece in position and without resetting the indication mechanism
Indicated absorbed energy or angle of rise after 11 half swings when the machine is
K or b J or degree operated in the normal manner without a test piece in position and without resetting the
3 3
indication mechanism
Distance to centre of test piece (centre of striker) from the axis of rotation (length of
l m
pendulum)
l m Distance to the centre of percussion from the axis of rotation
l m Distance to the point of application of the force F from the axis of rotation
M N·m Moment equal to the product Fl
Number of reference samples tested for the indirect verification of a pendulum impact
n —
V
testing machine
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 swing b
b
r J Resolution of the pendulum scale
RM — Reference material
s J Standard deviation of the KV values obtained on n reference samples
V V
S J Bias in the scale mechanism
t s Period of the pendulum
T s Total time for 100 swings of the pendulum
T s Maximum value of T
max
T s Minimum value of T
min
uK()V J Standard uncertainty of KV
V
V
u(B ) J Standard uncertainty contribution from bias

V
u(F) J Standard uncertainty of the measured force, F
u(F ) J Standard uncertainty of the force transducer
std
u(r) J Standard uncertainty contribution from resolution
Standard uncertainty of the certified value of the reference material used for the
u J
RM
indirect verification
u J Standard uncertainty of the indirect verification result
V
a degree Angle of fall of the pendulum
b degree Angle of rise of the pendulum
ν — Degrees of freedom corresponding to u(B )
B V
ν — Degrees of freedom corresponding to u
V V
ν — Degrees of freedom corresponding to u
RM RM
a
See Figure 4.
ISO 148-2:2008(E)
5 Testing machine
A pendulum impact testing machine consists of the following parts (see Figures 1 to 3):
a) foundation/installation;
b) machine framework — the structure supporting the pendulum, excluding the foundation;
c) pendulum, including the hammer;
d) anvils and supports (see Figures 2 and 3);
e) indicating equipment for the absorbed energy (e.g. scale and friction pointer or electronic readout device).
6 Direct verification
6.1 General
Direct verification of the machine involves the inspection of the following items:
a) foundation/installation;
b) machine framework;
c) pendulum, including the hammer and the striker;
d) anvils and supports;
e) indicating equipment.
6.2 Foundation/installation
6.2.1 The foundation to which the machine is fixed and the method(s) of fixing the machine to the
foundation are of utmost importance.
6.2.2 Inspection of the machine foundation can usually not be made once the machine has been installed;
thus, documentation made at the time of installation shall be produced to provide assurance that the mass of
the foundation is not less than 40 times that of the pendulum.
6.2.3 Inspection of the installed machine shall consist of the following:
a) ensuring that the bolts are torqued to the value specified by the machine manufacturer. The torque value
shall be noted in the document provided by the manufacturer of the machine (see 6.2.1). If other
mounting arrangements are used or selected by an end user, equivalency shall be demonstrated;
b) ensuring that the machine is not subject to external vibrations transmitted through the foundation at the
time of the impact test.
NOTE This can be accomplished, for example, by placing a small container of water on any convenient location on
the machine framework. The absence of ripples on the water surface indicates that this requirement has been met.
6.3 Machine framework
6.3.1 Inspection of the machine framework (see Figure 1) shall consist of determining the following items:
a) free position of the pendulum;
b) location of the pendulum in relation to the supports;
c) transverse and radial play of the pendulum bearings;
d) clearance between the hammer and the framework.
6 © ISO 2008 – All rights reserved

ISO 148-2:2008(E)
Machines manufactured after the original publication date of this part of ISO 148 shall have a reference plane
from which measurements can be made. Annex C, based on EN 10045-2, is provided for information.
6.3.2 The axis of rotation of the pendulum shall be parallel to the reference plane to within 2/1 000. This
shall be certified by the manufacturer.
6.3.3 The machine shall be installed so that the reference plane is horizontal to within 2/1 000.
For pendulum impact testing machines without a reference plane, the axis of rotation shall be established to
be horizontal to within 4/1 000 directly or a reference plane shall be established from which the horizontality of
the axis of rotation can be verified as described above.
6.3.4 When hanging free, the pendulum shall hang so that the striking edge is within 0,5 mm of the position
where it would just touch the test specimen.
NOTE This condition can be determined using a gauge in the form of a bar, approximately 55 mm in length and of
rectangular section, 9,5 mm in height and approximately 10 mm in width (see Figure 3). The distance between the striker
and the bar is then measured.
6.3.5 The plane of the swing of the pendulum shall be 90° ± 0,1° to the axis of rotation.
6.3.6 The striker shall make contact over the full width of the test piece.
NOTE One method of verifying this is as follows.
A test piece having dimensions of 55 mm ¥ 10 mm ¥ 10 mm is tightly wrapped in thin paper (e.g. by means of
adhesive tape), and the test piece is placed in the test-piece supports. Similarly, the striker edge is tightly
wrapped in carbon paper with the carbon side outermost (i.e. not facing the striker). From its position of
equilibrium, the pendulum is raised a few degrees, released so that it contacts the test piece, and prevented
from contacting the test piece a second time. The mark made by the carbon paper on the paper covering the
test piece should extend completely across the paper. This test may be performed concurrently with that of
checking the angle of contact between the striker and the test piece (see 6.4.8).
6.3.7 The pendulum shall be located so that the centre of the striker and the centre of the gap between the
anvils are coincident to within 0,5 mm.
6.3.8 Axial play in the pendulum bearings shall not exceed 0,25 mm measured at the striker under a
transverse force of approximately 4 % of the effective weight of the pendulum, F [see Figure 4 b)], applied at
g
the centre of strike.
6.3.9 Radial play of the shaft in the pendulum bearings shall not exceed 0,08 mm when a force of
150  ± 10 N is applied at a distance l perpendicular to the plane of swing of the pendulum.
NOTE The radial play can be measured, for example, by a dial gauge mounted on the machine frame at the bearing
housing in order to indicate movement at the end of the shaft (in the bearings) when a force of about 150 N is applied to
the pendulum perpendicularly to the plane of the swing.
6.3.10 For new machines, it is recommended that the mass of the base of the machine framework be at least
12 times that of the pendulum.
NOTE The base of the machine is that portion of the framework located below the plane(s) of the supports.
6.4 Pendulum
6.4.1 The verification of the pendulum (including striker) shall consist of determining the following quantities:
a) potential energy, K ;
P
b) error in the indicated absorbed energy, K ;
S
c) velocity of the pendulum at instant of impact;
d) energy absorbed by friction;
ISO 148-2:2008(E)
e) position of centre of percussion (i.e. distance from centre of percussion to axis of rotation);
f) striker radius;
g) angle between the line of contact of the striker and the horizontal axis of the test piece.
6.4.2 The potential energy, K , shall not differ from the nominal energy, K , by more than ± 1 %. The
P N
potential energy, K , shall be determined as follows.
P
The moment of the pendulum is determined by supporting the pendulum at a chosen distance, l , from the
axis of rotation by means of a knife edge on a balance or dynamometer in such a manner that the line through
the axis of rotation that joins the centre of gravity of the pendulum is horizontal within 15/1 000 [see
Figure 4 a)].
The force, F, and the length, l , shall each be determined to an accuracy of ± 0,2 %. The moment, M, is the
product of F ¥ l .
NOTE Length l can be equal to length l.
The angle of fall, a, shall be measured to an accuracy of ± 0,2°; this angle can be greater than 90°.
The potential energy, K , is then calculated by Equation (1):
P
K = M(1 - cosa) (1)
P
6.4.3 The graduation marks on the scale corresponding approximately to values of absorbed energy of 0 %,
10 %, 20 %, 30 %, 50 % and 80 % of the nominal energy shall be verified.
For each of these graduation marks, the pendulum shall be supported so that the graduation mark is indicated
by the pointer, and the angle of rise, b, then determined to ± 0,2°. The calculated energy is given by
Equation (2):
K = M(cosb - cosa) (2)
calc
NOTE 1 The degree of inaccuracy of measurement of l , F and b, as specified, yields a mean total error of
measurement of K of approximately ± 0,3 % of the full-scale value.
calc
The difference between the indicated absorbed energy, K , and the calculated energy from the measured
S
values shall not be greater than ± 1 % of the energy reading or ± 0,5 % of the nominal energy, K . In each
N
case, the greater value is permitted, i.e.:
K − K
calc S
¥ 100 < 1 % at between 80 % and 50 % of the nominal energy, K (3)
N
K
S
−
K K
calc S
¥ 100 < 0,5 % at less than 50 % of the nominal energy, K (4)
N
K
N
NOTE 2 Attention is drawn to the fact that the accuracy of the absorbed energy reading varies inversely to its value,
and this is important when K is small in comparison with K .
N
NOTE 3 For machines with scales and readout devices that are corrected for energy losses, K will need to be
calc
corrected in order to compare the results properly.
Absorbed energy values greater than 80 % of the potential energy are inaccurate and should be reported as
approximate.
NOTE 4 This requirement serves to ensure that all tests are conducted at strain rates that vary by less than a factor of
2. The strain rate is a function of the velocity of the pendulum while the striker is in contact with the specimen; for a
pendulum impact testing machine, the velocity decreases as the fracture progresses. The change in the velocity of the
pendulum can be calculated by first determining the velocity at impact using Equation (5) and, after impact, by using the
same formula except that the cosine of b is substituted for the cosine of a (see Figure 4).
8 © ISO 2008 – All rights reserved

ISO 148-2:2008(E)
6.4.4 The velocity at impact shall be determined for instance from Equation (5):
V 2(gl1 −cosα) (5)
=
where g may be taken as 9,81 m/s (to save measurement at the site of each testing machine).
The velocity at impact shall be 5 m/s to 5,5 m/s; however, for machines manufactured prior to 1998, any value
within the range of 4,3 m/s to 7 m/s is permissible and the value shall be stated in the report.
6.4.5 The energy absorbed by friction includes, but is not limited to, air resistance, bearing friction and the
friction of the indicating pointer. These losses shall be estimated as follows.
6.4.5.1 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, b , or energy reading, K , noted as indicated by the
1 1
pointer. A second test is then carried out without resetting the indication pointer and the new angle of rise, b ,
or energy reading, K , noted. Thus, the loss due to friction in the indicating pointer during the rise is equal to
p = M(cosb - cosb ) (6)
1 2
when the scale is graduated in degrees, or
p = K - K (7)
1 2
when the scale is graduated in energy units.
The values of b and b or of K and K shall be the mean values of four determinations.
1 2 1 2
6.4.5.2 Determination of the losses caused by bearing friction and air resistance for one half swing is
performed as follows.
After determining b or K in accordance with 6.4.5.1, the pendulum is put into its initial position. Without
2 2
resetting the indicating mechanism, release the pendulum without shock and vibration and permit it to swing
10 half swings. After the pendulum starts its 11th half swing, move the indicating mechanism to about 5 % of
the scale-range capacity and record the value as b or K . The losses by bearing friction and air resistance for
3 3
one half swing are equal to
p′ = 1/10 M(cosb - cosb ) (8)
3 2
when the scale is graduated in degrees, or
p′ = 1/10 (K - K ) (9)
3 2
when the scale is graduated in energy units.
NOTE If it is required to take into account these losses in an actual test giving an angle of rise, b, the quantity
β α + β
′
pp=+p (10)
β
β α + β
1 2
can be subtracted from the value of the absorbed energy.
Because b and b are nearly equal to a, for practical purposes, it can be reduced to an approximate equation for p as
1 2 b
follows:
β α + β
′
pp=+p (11)
β
α 2α
ISO 148-2:2008(E)
For machines graduated in energy units, the value of b can be calculated as follows:
b = arccos[1 - 1/M(K - K )] (12)
P T
6.4.5.3 The total friction loss p + p′, so measured, shall not exceed 0,5 % of the nominal energy, K . If it
N
does, and it is not possible to bring the friction loss within the tolerance by reducing the pointer friction, the
bearings shall be cleaned or replaced.
6.4.6 The distance from the centre of percussion to the axis of rotation, l , is derived from the period (time
of swing) of the pendulum, and it shall be 0,995 l ± 0,005 l. The accuracy of the calculated value of l shall be
± 0,5 mm.
The distance can be determined by swinging the pendulum through an angle not exceeding 5°, and
measuring the time, t, of a complete swing in seconds.
l is derived from Equation (13):
g ⋅t
l = (13)
4 π
where
g is taken as equal to 9,81 m/s ; however, if the local acceleration of gravity is known or is believed to
be significantly different from 9,81 m/s , the local acceleration of gravity shall be used;
p is taken as equal to 9,87.
Therefore, in metres, l = 0,248 5t .
The value of t shall be determined to within 0,1 %.
NOTE With a pendulum having a period of approximately 2 s, this accuracy may be achieved as follows. Determine
the time, T, of 100 complete swings, three times. An accurate measure of t is the average of the three T' divided by 100,
s
provided the quantity (T - T ), which represents the repeatability, is not more than 0,2 s.
max min
6.4.7 The dimensions of the striker shall be checked. Either of two types of striker may be used, the 2 mm
striker or the 8 mm striker. The values for the radius of curvature and the angle of the tip for both types are
shown in Table 3.
The maximum width of that portion of the striker passing between the anvils shall be at least 10 mm but not
greater than 18 mm.
NOTE 1 An example of a method of verifying the geometry of the striker is to make a replica for examination.
NOTE 2 Tests carried out with the 2 mm and 8 mm strikers usually give different results.
6.4.8 The angle between the line of contact of the striker and the horizontal axis of the test piece shall be
90° ± 2° (see 6.3.6).
6.4.9 The mechanism for releasing the pendulum from its initial position shall operate freely and permit
release of the pendulum without initial impulse, retardation or side vibration.
6.4.10 If the machine has a brake mechanism, means shall be provided to prevent the brake from being
accidentally engaged. In addition, there shall be provision to disengage the brake mechanism, for example
during the measurement of period and friction losses.
6.4.11 Machines with automated lifting devices shall be constructed so that direct verification can be
performed.
10 © ISO 2008 – All rights reserved

ISO 148-2:2008(E)
6.5 Anvil and supports
6.5.1 Inspection of the anvils and supports should consist of determining the following items (see Figures 2
and 3 and Table 3):
a) configuration of the supports;
b) configuration of the anvils;
c) distance between the anvils;
d) taper of the anvils;
e) radius of the anvils;
f) clearance for the broken test piece to exit the machine.
6.5.2 The planes containing the support surfaces shall be parallel and the distance between them shall not
exceed 0,1 mm. Supports shall be such that the axis of the test piece is parallel to the axis of rotation of the
pendulum within 3/1 000.
6.5.3 The planes containing the anvils shall be parallel and the distance between them shall not exceed
0,1 mm. The two planes containing the supports and the anvils shall be 90° ± 0,1° relative to each other.
Additional requirements for the configuration of the anvils are given in Table 3.
6.5.4 Sufficient clearance shall be provided to ensure that fractured test pieces are free to leave the
machine with a minimum of interference and not rebound into the hammer before the pendulum completes its
swing. No part of the pendulum that passes between the anvils shall exceed 18 mm in width.
Hammers are often of one of two basic designs (see Figure 1). When using the C-type hammer, the broken
test pieces will not rebound into the hammer if the clearance at each end of the test piece is greater than
13 mm. If end stops are used to locate test pieces, they shall be retracted prior to the instant of impact. When
using the U-type hammer, means shall be provided to prevent the broken test pieces from rebounding into the
hammer. In most machines using U-type hammers, shrouds (see Figure 3) should be designed and installed
with the following requirements:
a) a thickness of approximately 1,5 mm;
b) a minimum hardness of 45 HRC;
c) a radius of at least 1,5 mm at the underside corners;
d) a position in which the clearance between them and the hammer overhang does not exceed 1,5 mm.
In machines where the opening within the hammer permits a clearance between the ends of the test piece
(resting in position ready to test) and the shrouds of at least 13 mm, the requirements of a) and d) need not
apply.
6.6 Indicating equipment
6.6.1 The verification of the analogue indicating equipment shall consist of the following examinations:
a) examination of the scale graduations;
b) examination of the indicating pointer.
The scale shall be graduated in units of angle or of energy.
The thickness of the graduation marks on the scale shall
...