SIST EN ISO 4651:2000

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.DFLMVNHSchaumstoffe aus Kautschuk und Kunststoffen - Bestimmung der Stoßabsorption (ISO 4651:1988)Caoutchoucs et plastiques alvéolaires - Détermination de la capacité d'amortissement dynamique (ISO 4651:1988)Cellular rubbers and plastics - Determination of dynamic cushioning performance (ISO 4651:1988)83.100Penjeni polimeriCellular materialsICS:Ta slovenski standard je istoveten z:EN ISO 4651:1995SIST EN ISO 4651:2000en01-maj-2000SIST EN ISO 4651:2000SLOVENSKI
STANDARD



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



INTERNATIONAL STANDARD 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 Caoutchoucs et plastiques aMo/aires - Determination de Ia capacife d’amortissemen t dynamique ISO 4651 Second edition 1988-12-01 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



INTERNATIONAL STANDARD ISO 4651 : 1988 (El Cellular rubbers and plastics - Determination of dynamic cushioning Performance 1 Scope This International Standard specifies the procedure for deter- 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 piece. The test described is intended primarily for quality assurance; in addition, however, since this type of test is also used to obtain design data, notes are given in annex A to assist in the latter respect. The method is applicable solely to materials used in packaging. 2 Normative references The following Standards contain provisions which, through 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 agreements based on this International Standard are encouraged 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. ISO 291 : 1977, Plastics - Standard atmospheres for con- ditioning and testing. ISO 471 : 1983, Rubber - Standard temperatures, humidities and times for the conditioning and testing of test pieces. ISO 845 : 1977, CelMar rubbers and plastics - Determination of apparent density. ISO 1923 : 1981, Cellular plastics and rubbers - Determination o f linear dimensions. ISO 2231 : 1973, Fabric coated with rubber or plastics - Stan- dard atmospheres for conditioning and testing. ISO 3205 : 1976, Preferred fest temperatures. 3 Definitions For the purposes of this International Standard, the following definitions apply. 3.1 static stress, OST: The total mass of the hammer and any additional masses multiplied by the gravitational accelera- tion g, divided by the original area of the test piece. 3.2 peak deceleration, a: The maximum deceleration of the drop hammer during the impact on the test piece. In the Inter- national System of Units (SI), this is expressed in metres per second per second (m/s*). 3.3 displacement curve : The curve describing the displace- ment of the impacted surface of the test piece as a function of time during the impact. (See annex A.) 3.4 dynamic stress: The decelerating forte exerted by the material upon the drop hammer divided by the original area of the test piece. 3.5 deceleration forte: The mass of the drop hammer multiplied by its instantaneous deceleration. 3.6 strain: Displacement expressed as a percentage of the original thickness. 3.7 dynamic compression diagram: The curve describing the relation between the dynamic stress (decelerating forte per unit area) and the strain (displacement/thickness) in the cushioning material during impact. The slope of this curve at a specified strain (dynamic compressibility) may be used as a characteristic constant for the given Speed of impact and the thickness of the test piece. (See annex A.) 3.8 cushioning diagram: The diagram indicating both the peak deceleration a and the maximum value AL,,, of the displacement of the impact surface as a function of the static stress OST for the test pieces of the concerned materials having given thickness L,. (See annex A.) 3.9 corrected value of peak deceleration, a,: The value 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 measured peak deceleration by the original thickness divided by the Standard reference thickness. 3.10 equivalent drop height, h: That drop height which, in conditions of free fall in vacuo under Standard gravitational acceleration, would result in the same impact velocity of the hammer as was obtained during the test. 1 SIST EN ISO 4651:2000



ISO 4651 : 1988 (El The equivalent drop height, in metres, is given by the equation : V2 h - = Q” v is the hammer ; impact veloci ty, in metres Per second, of the g” is the Standard acceleration of free fall, i.e. 9,806 65 m/s*. 4 Apparatus 4.1 General The apparatus shall consist of a flat-based drop hammer, hav- ing a surface larger than the test piece, and an anvil of mass at least 100 times that of the drop hammer and whose face is parallel to the base of the drop hammer. Two basic types of dynamic testing equipment are in use (see figures 1 and 2). They are the guided vertical drop tester, in which the hammer drops between vertical guides on to the test piece which rests on the anvil, and the pendulum tester. The guided vertical drop tester is preferred for high deceleration tests and/or high static Stresses. The pendulum test is suitable for relatively low deceleration or low static Stresses. The hammer shall be fitted with a means of recording the peak value of deceleration on impact, with an accuracy of & 5 %, preferably by means of recording the deceleration time pulse on impact. Means shall also be available for measuring the velocity of the hammer, with an accuracy of + 5 %, immediately Prior to impact. Suitable facilities such as a digital timer capable of recording the time of fall over 25 mm shall also be available for measuring the velocity of the hammer Prior to impact with an 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. A transducer complying with the requirements of 4.2.1 shall be mounted centrally on the hammer in such a way that distortion of the transducer is avoided. The cable carrying the Signal from the impact transducer shall be mounted in such a way as to avoid excessive flexing at the transducer coupling. The mass of the hammer shall be adjustable in the range of static stress required; alternatively, several hammers may be used. Where hammers are adjusted by means of added masses it is recommended that these be added to the top surface of the hammer. lt is important that both hammer and anvil be sufficiently rigid so that undesirable vibrations are not recorded in the deceleration- time curve. The natura1 frequency of Vibration of the hammer shall be as high as practicable, preferably above 1 000 Hz. Prior to testing, the velocity of the hammer at impact shall be checked; the velocity shall be at least 95 % of the equivalent free fall velocity. The equivalent free fall velocity shall be calculated using the equation v=Jm where v is the final free fall velocity, in metres per second; g” is the Standard acceleration of free fall, i.e. 9,806 65 m/s*; h is the measured the test piece. heig ht, in metres, of the hammer above CAUTION - It is essential that the drop hammer 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. 4.2 Recording equipment The means of recording the deceleration-time pulses shall con- sist of a transducer, means of amplification, and recorder. Transducers generally are either piezoelectric or strain gauge types. The selection of specific recording equipment is op- tional. However, all recording equipment (including both transducer and recorders) shall have a frequency response ade- quate to measure the peak deceleration to an accuracy of + 5 %. The deceleration-time pulse obtained is usually a tran- - sient pulse approximating, on flexible foams, to a sinusoidal half-wavelength (half-sine) at low cushion displacements and becoming triangular or even spire-like, as illustrated in figure 3, for impacts producing high cushion displacements. On rigid foams, which crush on compression, the acceleration-time pulse may approximate to a steeply rising initial section, fol- lowed by a constant (or approximately constant) level before decreasing. The range of frequency response needed to measure these transient pulses is wider than might be an- ticipated. lt is important, therefore, that the following re- quirements should be borne in mind in respect of the main elements of the recording equipment. 4.2.1 Transducers Generally, these are either the piezoelectric or of the strain gauge type. Piezoelectric decelerometers have little inherent damping and, if the frequency of resonance is too low, they tan be caused to resonate by the decelerating pulse, so pro- ducing overshoot errors. In general, these may be avoided by ensuring that the natura1 period of Vibration of the transducer is less than 1/20 of the duration T of the deceleration pulse. However, for half-sine pulses or for pulses with a rapid initial rise, it is sufficient that the natura1 period of Vibration is less than l/lO of the pulse duration or 1/6 of the rise time of the pulse respectively. Strain gauge or inductive decelerometers have higher inherent damping (between 0,4 and 0,7 of critical). To obtain an accuracy of better than 5 % in the measurement of peak decel- eration, the decelerometer shall have a natura1 period of vibra- tion of less than 1/3 of the pulse duration for half-sine or triangular pulses. For pulses with a rapid initial rise, the natura1 period shall be less than 1/6 of the rise time. A piezoelectric transducer of the annular shear type whose reactive elements are isolated from the mounting with a top connection is recom- mended. 2 SIST EN ISO 4651:2000



ISO 4651 : 1988 (E) Piezoelectric decelerometers do not respond to sustained Signals and the low-frequency response depends on the suc- ceeding patt of the amplifier System. If the next Stage is a cathode follower, the time-constant of the input circuit of the cathode follower, combined with that of the transducer, con- 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, the corresponding value shall be 20 T. If the following Stage is a Charge amplifier, then the response to 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. These figures, for the frequency at which the response to con- tinuous sine-waves is reduced by 5 %, tan be used also for any amplifying System where a.c. coupling is employed. 4.2.2 Recorders The high-frequency response of cathode ray oscilloscopes is usually adequate. For galvanometer oscillographs, high- frequency response may be limited, and, as these devices are usually damped to 0,4 to 0,7 of critical, the galvanometer oscillograph should have a natura1 period of Vibration of less than 1/3 of the pulse duration for half-sine or triangular pulses. Oscilloscopes, and other recorders using a.c. amplifiers, tan have inadequate low-frequency response, and the considera- tio
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