1、 Reference number ISO 24999:2008(E) ISO 2008INTERNATIONAL STANDARD ISO 24999 First edition 2008-07-01 Flexible cellular polymeric materials Determination of fatigue by a constant-strain procedure Matriaux polymres alvolaires souples Dtermination de la fatigue par un procd de dformation constante ISO
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5、n below. COPYRIGHT PROTECTED DOCUMENT ISO 2008 All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from either ISO at the
6、address below or ISOs member body in the country of the requester. ISO copyright office Case postale 56 CH-1211 Geneva 20 Tel. + 41 22 749 01 11 Fax + 41 22 749 09 47 E-mail copyrightiso.org Web www.iso.org Published in Switzerland ii ISO 2008 All rights reservedISO 24999:2008(E) ISO 2008 All rights
7、 reserved iii Contents Page Foreword iv 1 Scope . 1 2 Normative references . 1 3 Principle. 1 4 Apparatus 1 5 Test pieces 2 6 Procedure 3 7 Expression of results . 3 8 Precision 4 9 Test report . 4 Annex A (informative) Precision . 5 Bibliography . 6 ISO 24999:2008(E) iv ISO 2008 All rights reserved
8、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 t
9、echnical 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
10、 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 circulate
11、d 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
12、for identifying any or all such patent rights. ISO 24999 was prepared by Technical Committee ISO/TC 45, Rubber and rubber products, Subcommittee SC 4, Products (other than hoses). INTERNATIONAL STANDARD ISO 24999:2008(E) ISO 2008 All rights reserved 1 Flexible cellular polymeric materials Determinat
13、ion of fatigue by a constant-strain procedure WARNING Persons using this International Standard should be familiar with normal laboratory practice. This standard does not purport to address all of the safety problems, if any, associated with its use. It is the responsibility of the user to establish
14、 appropriate safety and health practices and to ensure compliance with any national regulatory conditions. 1 Scope This International Standard specifies a method for determining the loss in thickness of flexible cellular materials when compressed repetitively to a fixed level of strain. It is partic
15、ularly useful for quality control in the manufacture of flexible polymeric cellular materials. Another procedure already exists as ISO 3385: this measures the fatigue characteristics of flexible polymeric cellular materials by constant-stress loading of the specimen rather than constant strain. It f
16、orms the basis of a material classification system in ISO 5999. These two fatigue procedures are complementary to each other and can both be useful in the prediction of end-use performance. The procedure and equipment used in this International Standard allow testing of a large number of test pieces
17、 at any one time, whereas ISO 3385 only allows testing of one test piece at a time under the compression device. 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 referen
18、ces, the latest edition of the referenced document (including any amendments) applies. ISO 1923, Cellular plastics and rubbers Determination of linear dimensions 3 Principle Constant strain is repetitively applied to the whole surface of the test piece, then the final thickness of the test piece is
19、measured. 4 Apparatus The test machine to be used shall be a compression type having the following structure and functions. The machine shall have two square flat plates, operating in parallel, the sizes of which are at least 10 mm greater than the sides of the test piece. Either the upper or lower
20、of the plates shall oscillate in the vertical direction to create compression of the test piece. The spacing between the plates shall be adjustable. ISO 24999:2008(E) 2 ISO 2008 All rights reservedThe lower plate shall be suitably vented with holes approximately 6 mm in diameter at approximately 20
21、mm pitch in order to allow air to escape from the test piece during compression. A typical design of such a compression mechanism is shown in Figure 1. Key 1 cam device 2 test piece 3 top plate 4 bottom plate 5 air-vent hole 6 motor Figure 1 An example of a constant-strain test machine 5 Test pieces
22、 5.1 Shape and dimensions Test pieces shall be in the form of a parallelepiped not less than 50 mm long and wide and not less than 20 mm thick. Several test pieces of differing density and/or indentation hardness can be tested simultaneously, provided that individual thicknesses are within 3 mm of e
23、ach other. 5.2 Samples showing orientation If the products show an orientation of the cellular structure, the direction in which the pressure is to be applied shall be agreed upon between the interested parties. Normally, this will correspond to the direction of applied compression in the finished p
24、roduct. ISO 24999:2008(E) ISO 2008 All rights reserved 3 5.3 Number Three test pieces shall be tested. 5.4 Conditioning Materials shall not be tested less than 72 h after manufacture unless it can be demonstrated that the mean results obtained at either 16 h or 48 h after manufacture do not differ b
25、y more than 10 % from those obtained after 72 h, in which case testing is permitted at 16 h or 48 h, respectively. Prior to the test, the test pieces shall be conditioned, uncompressed and otherwise undistorted, for at least 16 h in one of the following atmospheres as given in ISO 23549: (23 2) C, (
26、50 5) % relative humidity; (27 2) C, (65 5) % relative humidity. This conditioning period can form the final part of or, in the case of testing 16 h after manufacture, the whole of the period following manufacture. In the case of quality-control tests, test pieces can be taken a shorter time (down t
27、o a minimum of 12 h) after manufacture and testing carried out after conditioning for a shorter period (down to a minimum of 6 h) in one of the atmospheres specified above. 6 Procedure Measure, in accordance with ISO 1923, the thickness, d 1 , at the centre of each test piece to the nearest 0,1 mm w
28、ithout causing any deformation in the shape of the foam. After the measurement, place the test piece on the lower plate. When several test pieces are to be tested simultaneously, ensure that they are sufficiently far apart for there to be no contact between them during compression. Compress the test
29、 pieces for 80 000 cycles at a frequency of (60 5) cycles per minute with the machine stroke adjusted to apply 50 % compression of the original thickness, d 1 , to the thinnest of the test pieces. The compression plate shall be set to thickness d 1for the decompression process. On completion of the
30、test, remove the test pieces and allow them to recover for 30 min 5 min in the conditioning atmosphere (see 5.4) before re-measuring the thickness, d 2 , at the same position as before, to the nearest 0,1 mm. 7 Expression of results The percentage loss in thickness, d, is given by the equation: 12 1
31、 100 dd d d = where d 1is the original thickness, expressed in millimetres; d 2is the final thickness, expressed in millimetres. Express the result as the median of the values obtained for the three test pieces. ISO 24999:2008(E) 4 ISO 2008 All rights reserved8 Precision See Annex A. 9 Test report T
32、he test report shall include the following information: a) a reference to this International Standard; b) a description of the material tested; c) the conditioning used; d) the size and shape of the test pieces; e) the predominant orientation of the cellular structure, if any; f) the median percenta
33、ge thickness loss after compression; g) the date of the test. ISO 24999:2008(E) ISO 2008 All rights reserved 5 Annex A (informative) Precision A.1 General The precision of the method specified in this International Standard was determined in an interlaboratory test programme (ITP) in accordance with
34、 ISO/TR 9272. The precision results as determined by this ITP should not be used for acceptance or rejection of any group of materials without documentation that the results of this precision evaluation are actually applicable to the particular group of materials tested. A.2 Details Seven laboratori
35、es participated in the ITP. Three types of flexible polyurethane foam of different densities were used. Two test pieces of each type of foam were prepared and the loss in thickness determined in accordance with the method specified in this International Standard. The interval for repeatability (with
36、in- laboratory precision) was 7 days. A.3 Precision results A.3.1 The precision results are given in Table A.1. A.3.2 Repeatability: The repeatability, or local-domain precision, of this test method has been established as the values given in Table A.1 for each repeatability parameter listed in the
37、table. Test results obtained in a particular laboratory (by the proper use of this International Standard) that differ by more than the tabulated values of r, in measurement units, and (r), in percent, should be considered suspect, i.e. to have come from different populations, and to suggest that so
38、me appropriate investigative action be taken. A.3.3 Reproducibility: The reproducibility, or global-domain precision, for this test method has been established as the values given in Table A.1 for each reproducibility parameter listed in the table. The test results obtained in different laboratories
39、 (by the proper use of this International Standard) that differ by more than the tabulated values of R, in measurement units, and (R), in percent, should be considered suspect, i.e. to have come from different populations, and to suggest that some appropriate investigative action be taken. Table A.1
40、 Precision results Within laboratory Between laboratories Type of sample according to hardness Mean loss in thickness % s rr ( r) s RR ( R) Softa5,71 0,105 0,297 5,201 0,406 1,15 20,140 Mediumb4,18 0,308 0,872 20,861 0,253 0,72 17,225 Hardc1,55 0,154 0,434 28,000 0,185 0,52 33,548 aLow-hardness type
41、 (density 14 kg/m 3 ). bMedium-hardness type (density 20 kg/m 3 ). cHigh-hardness type (density 35 kg/m 3 ). ISO 24999:2008(E) 6 ISO 2008 All rights reservedBibliography 1 ISO 3385, Flexible cellular polymeric materials Determination of fatigue by constant-load pounding 2 ISO 5999, Flexible cellular
42、 polymeric materials Polyurethane foam for load-bearing applications excluding carpet underlay Specification 3 ISO/TR 9272, Rubber and rubber products Determination of precision for test method standards 4 ISO 23529, Rubber General procedures for preparing and conditioning test pieces for physical test methods ISO 24999:2008(E) ICS 83.100 Price based on 6 pages ISO 2008 All rights reserved
