EN ISO 489:1999

SLOVENSKI STANDARD
SIST EN ISO 4651:2000
01-maj-2000
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Cellular rubbers and plastics - Determination of dynamic cushioning performance (ISO
4651:1988)
Schaumstoffe aus Kautschuk und Kunststoffen - Bestimmung der Stoßabsorption (ISO
4651:1988)
Caoutchoucs et plastiques alvéolaires - Détermination de la capacité d'amortissement
dynamique (ISO 4651:1988)
Ta slovenski standard je istoveten z: EN ISO 4651:1995
ICS:
83.100 Penjeni polimeri Cellular materials
SIST EN ISO 4651:2000 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

SIST EN ISO 4651:2000
SIST EN ISO 4651:2000
SIST EN ISO 4651:2000
SIST EN ISO 4651:2000
SIST EN ISO 4651:2000
SIST EN ISO 4651:2000
ISO
INTERNATIONAL STANDARD
Second edition
1988-12-01
INTERNATIONAL ORGANIZATION FOR STANDARDIZATION
ORGANISATION INTERNATIONALE DE NORMALISATION
’ MEXAYHAPOAHAR OPI-AHM3A~MR I-IO CTAHfiAPTM3AL/MM
Cellular rubbers and plastics - Determination of
dynamic cushioning Performance
Determination de Ia capacife d’amortissemen t
Caoutchoucs et plastiques aMo/aires -
dynamique
Reference number
ISO 4651 : 1988 (E)
SIST EN ISO 4651:2000
ISO 4651 : 1988 (El
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. Esch 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, govern-
mental 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.
Draft International Standards adopted by the technical committees are circulated to
the member bodies for approval before their acceptance as International Standards by
the ISO Council. They are approved in accordance with ISO procedures requiring at
least 75 % approval by the member bodies voting.
International Standard ISO 4651 was prepared by Technical Committee ISO/TC 45,
Rubber and rubber products.
This second edition cancels and replaces the first edition (ISO 4651 : 1979), sub-clauses
3.1, 7.1, 7.2.1, 7.2.2, 8.2 and 9.2 of which have been technically revised.
Annex A of this International Standard is for information only.
0 International Organkation for Standardkation, 1988
Printed in Switzerland
SIST EN ISO 4651:2000
ISO 4651 : 1988 (El
INTERNATIONAL STANDARD
Cellular rubbers and plastics - Determination of
dynamic cushioning Performance
3.2 peak deceleration, a: The maximum deceleration of the
1 Scope
drop hammer during the impact on the test piece. In the Inter-
national System of Units (SI), this is expressed in metres per
This International Standard specifies the procedure for deter-
second per second (m/s*).
mining the dynamic cushioning Performance of cellular rubber
materials and rigid and flexible cellular plastics, by measuring
the peak deceleration of a mass when it is dropped on a test
3.3 displacement curve : The curve describing the displace-
piece. The test described is intended primarily for quality
ment of the impacted surface of the test piece as a function of
assurance; in addition, however, since this type of test is also
time during the impact. (See annex A.)
used to obtain design data, notes are given in annex A to assist
in the latter respect.
3.4 dynamic stress: The decelerating forte exerted by the
The method is applicable solely to materials used in packaging.
material upon the drop hammer divided by the original area of
the test piece.
2 Normative references
3.5 deceleration forte: The mass of the drop hammer
The following Standards contain provisions which, through
multiplied by its instantaneous deceleration.
reference in this text, constitute provisions of this International
Standard. At the time of publication, the editions indicated
were valid. All Standards are subject to revision, and Parties to
3.6 strain: Displacement expressed as a percentage of the
agreements based on this International Standard are encouraged
original thickness.
to investigate the possibility of applying the most recent
editions of the Standards listed below. Members of IEC and ISO
maintain registers of currently valid International Standards.
3.7 dynamic compression diagram: The curve describing
the relation between the dynamic stress (decelerating forte per
Standard atmospheres for con-
ISO 291 : 1977, Plastics -
unit area) and the strain (displacement/thickness) in the
ditioning and testing.
cushioning material during impact. The slope of this curve at a
specified strain (dynamic compressibility) may be used as a
ISO 471 : 1983, Rubber - Standard temperatures, humidities
characteristic constant for the given Speed of impact and the
and times for the conditioning and testing of test pieces.
thickness of the test piece. (See annex A.)
ISO 845 : 1977, CelMar rubbers and plastics - Determination
of apparent density.
3.8 cushioning diagram: The diagram indicating both the
peak deceleration a and the maximum value AL,,, of the
ISO 1923 : 1981, Cellular plastics and rubbers - Determination
displacement of the impact surface as a function of the static
o f linear dimensions.
stress OST for the test pieces of the concerned materials having
given thickness L,. (See annex A.)
ISO 2231 : 1973, Fabric coated with rubber or plastics - Stan-
dard atmospheres for conditioning and testing.
3.9 corrected value of peak deceleration, a,: The value
ISO 3205 : 1976, Preferred fest temperatures.
of the peak deceleration after correction for any small deviation
of the test piece original thickness from the Standard reference
thickness of 50 mm. This is obtained by multiplying the
3 Definitions
measured peak deceleration by the original thickness divided by
the Standard reference thickness.
For the purposes of this International Standard, the following
definitions apply.
3.10 equivalent drop height, h: That drop height which, in
conditions of free fall in vacuo under Standard gravitational
3.1 static stress, OST: The total mass of the hammer and
acceleration, would result in the same impact velocity of the
any additional masses multiplied by the gravitational accelera-
hammer as was obtained during the test.
tion g, divided by the original area of the test piece.
SIST EN ISO 4651:2000
ISO 4651 : 1988 (El
where
The equivalent drop height, in metres, is given by the equation :
V2
v is the final free fall velocity, in metres per second;
h -
= Q”
is the Standard acceleration of free fall, i.e.
g”
9,806 65 m/s*;
v is the impact veloci ty, in metres second, of the
Per
h is the measured heig ht, in metres, of the hammer above
hammer ;
the test piece.
is the Standard acceleration of free fall, i.e.
g”
CAUTION - It is essential that the drop hammer
9,806 65 m/s*.
mechanism is such that the safety of the Operator is
assured when test pieces are placed on the anvil, and
some form of safety interlock is recommended.
4 Apparatus
4.1 General
4.2 Recording equipment
The apparatus shall consist of a flat-based drop hammer, hav-
The means of recording the deceleration-time pulses shall con-
ing a surface larger than the test piece, and an anvil of mass at
sist of a transducer, means of amplification, and recorder.
least 100 times that of the drop hammer and whose face is
Transducers generally are either piezoelectric or strain gauge
parallel to the base of the drop hammer. Two basic types of
types. The selection of specific recording equipment is op-
dynamic testing equipment are in use (see figures 1 and 2).
tional. However, all recording equipment (including both
They are the guided vertical drop tester, in which the hammer
transducer and recorders) shall have a frequency response ade-
drops between vertical guides on to the test piece which rests
quate to measure the peak deceleration to an accuracy of
on the anvil, and the pendulum tester.
+ - 5 %. The deceleration-time pulse obtained is usually a tran-
sient pulse approximating, on flexible foams, to a sinusoidal
The guided vertical drop tester is preferred for high deceleration
half-wavelength (half-sine) at low cushion displacements and
tests and/or high static Stresses. The pendulum test is suitable
becoming triangular or even spire-like, as illustrated in figure 3,
for relatively low deceleration or low static Stresses.
for impacts producing high cushion displacements. On rigid
The hammer shall be fitted with a means of recording the peak
foams, which crush on compression, the acceleration-time
value of deceleration on impact, with an accuracy of & 5 %,
pulse may approximate to a steeply rising initial section, fol-
preferably by means of recording the deceleration time pulse on
lowed by a constant (or approximately constant) level before
impact. Means shall also be available for measuring the velocity
decreasing. The range of frequency response needed to
of the hammer, with an accuracy of + 5 %, immediately Prior
measure these transient pulses is wider than might be an-
to impact. Suitable facilities such as a digital timer capable of
ticipated. lt is important, therefore, that the following re-
recording the time of fall over 25 mm shall also be available for
quirements should be borne in mind in respect of the main
measuring the velocity of the hammer Prior to impact with an
elements of the recording equipment.
accuracy of + 1 %. The measurement shall be completed,
before impact, at a Point on the path of the hammer which is
within 5 mm of its positon at initial impact.
4.2.1 Transducers
A transducer complying with the requirements of 4.2.1 shall be
Generally, these are either the piezoelectric or of the strain
mounted centrally on the hammer in such a way that distortion
gauge type. Piezoelectric decelerometers have little inherent
of the transducer is avoided. The cable carrying the Signal from
damping and, if the frequency of resonance is too low, they
the impact transducer shall be mounted in such a way as to
tan be caused to resonate by the decelerating pulse, so pro-
avoid excessive flexing at the transducer coupling.
ducing overshoot errors. In general, these may be avoided by
ensuring that the natura1 period of Vibration of the transducer is
The mass of the hammer shall be adjustable in the range of
less than 1/20 of the duration T of the deceleration pulse.
static stress required; alternatively, several hammers may be
However, for half-sine pulses or for pulses with a rapid initial
used. Where hammers are adjusted by means of added masses
rise, it is sufficient that the natura1 period of Vibration is less
it is recommended that these be added to the top surface of the
than l/lO of the pulse duration or 1/6 of the rise time of the
hammer.
pulse respectively.
lt is important that both hammer and anvil be sufficiently rigid so
Strain gauge or inductive decelerometers have higher inherent
that undesirable vibrations are not recorded in the deceleration-
damping (between 0,4 and 0,7 of critical). To obtain an
time curve. The natura1 frequency of Vibration of the hammer
accuracy of better than 5 % in the measurement of peak decel-
shall be as high as practicable, preferably above 1 000 Hz.
eration, the decelerometer shall have a natura1 period of vibra-
Prior to testing, the velocity of the hammer at impact shall be
tion of less than 1/3 of the pulse duration for half-sine or
checked; the velocity shall be at least 95 % of the equivalent
triangular pulses. For pulses with a rapid initial rise, the natura1
free fall velocity. The equivalent free fall velocity shall be
period shall be less than 1/6 of the rise time. A piezoelectric
calculated using the equation
transducer of the annular shear type whose reactive elements
are isolated from the mounting with a top connection is recom-
mended.
v=Jm
SIST EN ISO 4651:2000
ISO 4651 : 1988 (E)
The differente in the mean thickness between the test pieces in
Piezoelectric decelerometers do not respond to sustained
a set of ten shall not be greater than 2 mm. The dimensions
Signals and the low-frequency response depends on the suc-
shall be measured in accordance with ISO 1923. The thickness
ceeding patt of the amplifier System. If the next Stage is a
of the test piece may be achieved by plying up not more than
cathode follower, the time-constant of the input circuit of the
two sheets not less than 20 mm thick and of the same orienta-
cathode follower, combined with that of the transducer, con-
tion with respect to any known direction of anisotropy.
trols low-frequency response. To record peak decelerations to
within 5 % on half-sine pulses, the time-constant shall be at
least seven times the pulse duration T. For Square-type pulses,
5.2 Uniformity
the corresponding value shall be 20 T.
The density of each test piece shall not vary by more than
If the following Stage is a Charge amplifier, then the response to
+ 1
0 % from the average density of a set of 10 test pieces.
continuous sine-waves shall not be reduced by more than 5 %
at a frequency of 1/22 Tfor 5 % errors on half-sine pulses. The
corresponding frequency for Square pulses is 1/50 T.
5.3 Orientation during testing
These figures, for the frequency at which the response to con-
Test pieces tut from finished articles shall be tested so that the
tinuous sine-waves is reduced by 5 %, tan be used also for any
direction of dynamic stress corresponds with that of the
amplifying System where a.c. coupling is employed.
dynamic stress to which the material is subjected in the finished
article. If this is not possible, the relation of the direction of the
principal dynamic stress in the finished article to that of the test
4.2.2 Recorders
direction shall be stated in the report.
The high-frequency response of cathode ray oscilloscopes is
For galvanometer oscillographs, high-
usually adequate.
5.4 Number
frequency response may be limited, and, as these devices
...