1、Rubber, vulcanized Determination of tension fatigueCaoutchouc vulcanis Dtermination de la fatigue en traction ISO 2011Reference numberISO 6943:2011(E)Third edition2011-10-01ISO6943INTERNATIONAL STANDARDISO 6943:2011(E)COPYRIGHT PROTECTED DOCUMENT ISO 2011All rights reserved. Unless otherwise specifi
2、ed, 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 address below or ISOs member body in the country of the requester.ISO copyright officeCase p
3、ostale 56 CH-1211 Geneva 20Tel. + 41 22 749 01 11Fax + 41 22 749 09 47E-mail copyrightiso.orgWeb www.iso.orgPublished in Switzerlandii ISO 2011 All rights reservedISO 6943:2011(E)Contents PageForeword iv1 Scope 12 Normative references .13 Terms and definitions .24 Principle .25 Apparatus 25.1 Fatigu
4、e-testing machine 25.2 Dies and cutters .25.3 Marker .35.4 Marking substance 35.5 Measuring instruments 36 Calibration .37 Test piece .37.1 Dimensions .37.2 Number of test pieces 57.3 Storage and conditioning 58 Test conditions .58.1 Test strains 58.2 Test frequency 68.3 Test temperature 68.4 Test a
5、tmosphere 69 Procedure 69.1 Marking of dumb-bell test pieces 69.2 Measurement of test pieces .69.3 Insertion of test pieces in the fatigue-testing machine .79.4 Determination of fatigue life .89.5 Measurement of set and maximum strain after cycling 89.6 Measurement of maximum stress and maximum stra
6、in energy density .810 Expression of results .910.1 Calculation of fatigue life 910.2 Calculation of set .1010.3 Calculation of maximum strain 1010.4 Calculation of maximum stress .1110.5 Calculation of strain energy density 1111 Test report .11Annex A (informative) Explanatory notes.13Annex B (norm
7、ative) Calibration schedule16Bibliography .18 ISO 2011 All rights reserved iiiForewordISO (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
8、 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 cl
9、osely 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. Draf
10、t 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 docume
11、nt may be the subject of patent rights. ISO shall not be held responsible for identifying any or all such patent rights.ISO 6943 was prepared by Technical Committee ISO/TC 45, Rubber and rubber products, Subcommittee SC 2, Testing and analysis.This third edition cancels and replaces the second editi
12、on (ISO 6943:2007), which has been revised primarily to include a calibration schedule for the apparatus used (see Annex B).ISO 6943:2011(E)iv ISO 2011 All rights reservedINTERNATIONAL STANDARD ISO 6943:2011(E)Rubber, vulcanized Determination of tension fatigueWARNING Persons using this Internationa
13、l 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 appropriate safety and health practices and to ensure compliance with any national r
14、egulatory conditions.IMPORTANT Certain procedures specified in this International Standard might involve the use or generation of substances, or the generation of waste, that could constitute a local environmental hazard. Reference should be made to appropriate documentation on safe handling and dis
15、posal after use.1 ScopeThis International Standard describes a method for the determination of the resistance of vulcanized rubbers to fatigue under repeated tensile deformations, the test piece size and frequency of cycling being such that there is little or no temperature rise. Under these conditi
16、ons, failure results from the growth of a crack that ultimately severs the test piece.The method is restricted to repeated deformations in which the test piece is relaxed to zero strain for part of each cycle. Analogous fatigue processes can occur under repeated deformations which do not pass throug
17、h zero strain and also, in certain rubbers, under static deformation, but this International Standard does not apply to these conditions.The method is believed to be suitable for rubbers that have reasonably stable stress-strain properties, at least after a period of cycling, and that do not show un
18、due stress softening or set, or highly viscous behaviour. Materials that do not meet these criteria might present considerable difficulties from the points of view of both experiment and interpretation. For example, for a rubber that develops a large amount of set during the fatigue test, the test s
19、train will be ill-defined and the fatigue life is likely to differ markedly under constant maximum load and constant maximum extension conditions; how the results for such a rubber should be interpreted, or compared with those for other rubbers, has not been established by basic work. As a general g
20、uide, a rubber for which the set determined in accordance with 9.5 and 10.2 exceeds 10 % is likely to fall into this category. For this reason, the method is not considered suitable for most thermoplastic elastomers.Similar considerations apply with regard to other changes in elasticity behaviour du
21、ring testing.A distinction should be made between this fatigue test and the flexometer tests described in the various parts of ISO 4666, where fatigue breakdown occurs under the simultaneous action of stress and temperature.Advantages over the De Mattia flex cracking and cut growth test (see ISO 132
22、) include the following. The test yields quantitative results which do not depend on operator interpretation and which can be recorded automatically. The initial deformation is clearly defined and can readily be varied to suit different applications.Great caution is necessary in attempting to relate
23、 standard test results to service performance since the comparative fatigue resistance of different vulcanizates can vary according to the test conditions used and to the basis by which the results are compared. Guidance on the selection of test conditions and on the interpretation of results is giv
24、en in Annex A.2 Normative referencesThe 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 18899:2004
25、, Rubber Guide to the calibration of test equipmentISO 23529, Rubber General procedures for preparing and conditioning test pieces for physical test methods ISO 2011 All rights reserved 13 Terms and definitionsFor the purposes of this document, the following terms and definitions apply.3.1fatigue li
26、fenumber of cycles required to break a test piece repeatedly deformed to a prescribed tensile strain3.2tension fatiguefracture, through crack growth, of a component or test piece subjected to a repeated tensile deformation4 PrincipleDumb-bell or ring test pieces are repeatedly deformed in simple ext
27、ension until they fail by breaking. The test pieces are relaxed to zero strain for part of each cycle. The number of deformation cycles to failure, defined as the fatigue life, is determined as a function of the maximum strain and, if required, as a function of the maximum stress or strain energy de
28、nsity imposed during the test.5 Apparatus5.1 Fatigue-testing machineThe fatigue-testing machine shall provide a reciprocating motion at a frequency which shall normally be within the range 1 Hz to 5 Hz.For testing dumb-bell test pieces, the machine shall be provided with clamps that grip the test pi
29、ece sufficiently firmly to prevent slippage, irrespective of the magnitude of the strain applied.For testing ring test pieces, each station on the machine shall be provided with two pairs of rollers, one pair fixed to the body of the machine and the other to the reciprocating part. To minimize frict
30、ion, the rollers shall be fabricated from stainless or chromium-plated steel, well polished and fitted with free-running ball races. The roller arrangement shall be such that the test pieces are held securely in place over the rollers throughout the test.The stroke of the machine and the position of
31、 the fixed clamps or rollers shall be adjustable to provide a range of test strains. In all cases, the test piece shall be relaxed to zero strain for part of each cycle.The fixed clamps or rollers should preferably be fitted with contacts or other means of operating counters to register the number o
32、f cycles to failure of each test piece.If it is required to determine the maximum stress of the cycle, manual or automatic means for measurement of the load shall be provided. Stress-strain properties and strain energy density under test conditions can be determined for rings if automatic equipment
33、for force-extension measurement is provided.Alternatively, and for dumb-bell test pieces, stress-strain properties can be determined separately using a conventional tensile-testing machine.5.2 Dies and cuttersAll dies and cutters used shall be made and maintained in accordance with ISO 23529.Since f
34、atigue life is sensitive to flaw size, it is essential that the dies or cutters used for the preparation of test pieces be carefully maintained so that the cutting edges are sharp and free from nicks. Regular control tests, using an established rubber, shall be made to check sharpness. Any oil shall
35、 be removed from the cutter after sharpening.ISO 6943:2011(E)2 ISO 2011 All rights reserved5.3 MarkerIf a marker is used for marking the reference lines on dumb-bell test pieces, it shall have two parallel edges. These shall be ground smooth and true, 0,05 mm to 0,10 mm wide at the edge and bevelled
36、 at an angle of not more than 15.The marking implement shall not damage the rubber surface.5.4 Marking substanceThe marking substance shall have no deleterious effect on rubber and shall be of contrasting colour.5.5 Measuring instrumentsThe instrument for measuring the thickness of dumb-bell test pi
37、eces (and the axial thickness of ring test pieces) shall be in accordance with ISO 23529, consisting essentially of a micrometer dial gauge having a circular foot which does not extend beyond the surface of the rubber where the measurement is being taken, and applying a pressure of (22 5) kPa for a
38、rubber with hardness equal to or higher than 35 IRHD.Vernier calipers, a travelling microscope or other suitable means shall be provided for the measurement of other test piece dimensions. A graduated cone is recommended for the measurement of the internal diameter and internal circumference of ring
39、 test pieces.6 CalibrationThe requirements for calibration of the test apparatus are given in Annex B.7 Test piece7.1 Dimensions7.1.1 GeneralStandard test pieces shall be dumb-bells or rings having dimensions within the limits prescribed in 7.1.2 and 7.1.3. Any test piece showing irregularities or i
40、mperfections shall not be used.7.1.2 Dumb-bell test pieceDumb-bell test pieces and the dies with which they are cut out shall be as shown in Figure 1. The dies shall have the dimensions given in Table 1. The reference length (the distance between the marked reference lines) shall be 25 mm for the ty
41、pe 1 test piece and 20 mm for the type 1A and type 2 test pieces. This length shall be equidistant from the ends of the central parallel-sided part of the test piece. The tabs may have beaded ends for location purposes.The thickness of dumb-bells shall be (1,5 0,2) mm. In any one dumb-bell, the thic
42、kness of the narrow part shall nowhere deviate by more than 2 % from the mean. If results from two sets of dumb-bells are being compared, the mean thicknesses of the sets shall be within 10 % of one another.Fatigue life depends on test piece thickness and it has been shown that, at a thickness of 1,
43、5 mm, the life is least sensitive to change in this dimension. If required, an alternative thickness of (2,0 0,2) mm may be used provided it is recorded in the test report, but it might lead to different results.Dumb-bells shall be cut from sheet by punching with a die using a single stroke of a pre
44、ss. The rubber shall be supported on a sheet of slightly yielding material (for example cardboard or polyethylene) on a flat rigid surface; the region of the supporting sheet beneath the die shall be free from cuts or other imperfections. Care shall be taken to ensure that the rubber is isotropic an
45、d free from built-in stresses (failure to meet either of these requirements can cause very marked variations in fatigue life); in cases where there is any doubt, check stress-strain and fatigue tests shall be carried out using test pieces cut in different directions or from different ISO 6943:2011(E
46、) ISO 2011 All rights reserved 3locations in a sheet. Any sheet showing such imperfections shall be discarded unless anisotropy or “grain” effects are being investigated, when their extent and direction shall be specified and recorded in the test report.a) Test pieceb) DieKey1 reference linesA to F
47、see Table 1Figure 1 Shape of dumb-bell test pieces and dieTable 1 Die dimensions for dumb-bell test pieces see Figure 1 b)Dimensions in millimetresDimension Type 1 Type 1A Type 2A Overall length, min. 115 100 75B Width of ends 25 1 25 1 12,5 1C Length of narrow parallel-sided portion 33 2 21 1 25 1D
48、 Width of narrow parallel-sided portiona6,2 0,2 5 0,1 4 0,1E Small radius 14 1 11 1 8 0,5F Large radius 25 2 25 2 12,5 1aThe variation within any one die shall not exceed 0,05 mm.NOTE The dies are identical to those specified for type 1, type 1A and type 2 dumb-bell test pieces in ISO 37 for the det
49、ermination of tensile stress-strain properties.ISO 6943:2011(E)4 ISO 2011 All rights reserved7.1.3 Ring test pieceThe standard ring test piece shall have a nominal internal diameter of 44,6 mm and an external diameter of 52,6 mm, giving a nominal radial width of 4 mm; the radial width shall nowhere deviate from the mean by more than 0,2 mm. The axial thickness shall be (1,5 0,2) mm and on any one ring the thickness shall deviate from the mean by no more than 2 %.NOTE With respect to the internal
