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1、hternational Standard (! 6943 0 $a=, 4 INTERNATIONAL ORGANIZATION FOR STANDARDIZATION.MEYHAPOAHAR OPrAHMBALbiR IlO CTAHPTH3AWlMRGANlSATlON INTERNATIONALE DE NORMALISATION Rubber, vulcanized - Determination of tension fatigue Caoutchouc vulcanis - Oktermination de la fatigue en traction First edition
2、 - 1964-12-15 UDC 667.663 : 620.176.3 Ref. No. lSO.6943-1964 (EI Descriptors : rubber, vulcanized rubber, tests, fatigue tests, tension tests, determination, fatigue life. Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standard
3、s 1/9972545001 Not for Resale, 04/22/2007 21:33:50 MDTNo reproduction or networking permitted without license from IHS -,-,- Foreword IS0 (the international Organization for Standardization) is a worldwide federation of national standards bodies (IS0 member bodies). The work of preparing internation
4、al Standards is normally carried out through IS0 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, govern- mental and non-governmental, in liaison with IS
5、O, also take part in the work. Draft international Standards adopted by the technical committees are circulated to the member bodies for approval before their acceptance as international Standards by the IS0 Council. They are approved in accordance with IS0 procedures requiring at least 75 % approva
6、l by the member bodies voting, International Standard IS0 5943 was prepared by Technical Committee ISO/TC 45, Rubber and rubber products. 0 International Organization for Standardization, 1984 0 Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=
7、NASA Technical Standards 1/9972545001 Not for Resale, 04/22/2007 21:33:50 MDTNo reproduction or networking permitted without license from IHS -,-,- INTERNATIONAL STANDARD IS0 6943-1964 (E) Rubber, vulcanized - Determination of tension fatigue 1 Scope and field of application This International Stand
8、ard describes a method for the deter- mination of the resistance of vulcanized rubbers to fatigue under repeated tensile deformations, the test piece size and fre- quency of cycling being such that there is little or no temperature rise. Under these conditions, failure results from the growth of a c
9、rack 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 defor- mations which do not pass through zero strain and also, in cer- tain rub
10、bers, 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 undue stress softening or set, or highl
11、y viscous behaviour. Materials that do not meet these criteria may 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 strain will be ill-defined and the fatig
12、ue life is likely to differ markedly under constant maximum load and constant maximum extension conditions; how the results for such a rub- ber should be interpreted, or compared with those for other rubbers, has not been established by basic work. As a general guide, a rubber for which the set dete
13、rmined in accordance with 8.5 and 9.2 exceeds 10 % is likely to fall into this category. Similar considerations apply with regard to other changes in elasticity behaviour during test. A distinction should be made between this fatigue test and the flexometer tests described in IS0 455611 to 3, where
14、fatigue breakdown occurs under the simultaneous action of stress and temperature. Advantages over the de Mattia flex cracking and cut growth tests (see IS0 132 and IS0 133) include the following. The test yields quantitative results which do not depend on operator in- terpretation and which can be r
15、ecorded automati- cally. The initial deformation is clearly defined and can readily be varied to suit different applications. Great caution is necessary in attempting to relate standard test results to service performance since the comparative fatigue resistance of different vulcanizates can vary ac
16、cording 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 given in the annex. 2 References IS0 37, Rubber, vulcanized - Determination of tensile stress- strain properties. IS0 132, Vulc
17、anized rubbers - Determination of resistance to flex cracking (De Mattia type machine). IS0 133, Rubber, vulcanized - Determination of crackgrowth (De Mama). IS0 471, Rubber - Standard temperatures, humidities and times for the conditioning and testing of test pieces. IS0 1826, Rubber, vulcanized -
18、Time-interval between vulcanization and testing - Specification. IS0 4648, Rubber, vulcanized - Determination of dimensions of test pieces and products for test purposes. IS0 4661, Rubber - Preparation of test pieces. IS0 4666, Rubber, vulcanized - Determination of temperature rise and resistance to
19、 fatigue in flexometer testing - Part I: Basic principles. Part 2: Rotary flexometer. Part 3: Compression flexometer. 3 Definitions For the purpose of this International Standard the following definitions apply. 3.1 fatigue life: The number of cycles required to break a test piece repeatedly deforme
20、d to a prescribed tensile strain. 3.2 tension fatigue: Fracture, through crack growth, of a component or test piece subjected to a repeated tensile defor- mation. 4 Principle Dumb-bell or ring test pieces are repeatedly deformed in simple extension until they fail by breaking. The test pieces are re
21、laxed 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 density imposed during the test. 1 Copyright International O
22、rganization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/22/2007 21:33:50 MDTNo reproduction or networking permitted without license from IHS -,-,- IS0 6943-1964 (E) 5 Apparatus 5.4 Marking substance The marking substanc
23、e shall have no deleterious effect on rub- ber and shall be of contrasting colour. 5.1 Fatigue testing machine The fatigue testing machine shall provide a reciprocating motion at a frequency which shall normally be within the range 1 to 5 Hz. For testing dumb-bell test pieces, the machine shall be p
24、ro- vided with clamps that grip the test piece 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
25、to the reciprocating part. To minimize friction, the rollers shall be fabricated from stainless or chromium plated steel, well polished and fitted with free run- ning ball races. The roller arrangement shall be such that the test pieces are held securely in place over the rollers throughout the test
26、. The stroke of the machine and the position of 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 con- tacts or other mea
27、ns of operating counters to register the number of 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 c
28、an be determined for rings if automatic equipment for force-extension measurement is provided. Alternatively, and for dumb-bell test pieces, stress-strain prop- erties can be separately determined using a conventional tensile testing machine. 5.2 Dies and cutters All dies and cutters used shall be m
29、ade and maintained in ac- cordance with IS0 4661. Since fatigue 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 establishe
30、d rub- ber, should be made to check sharpness. Any oil shall be removed from the cutter after sharpening. 5.3 Marker If 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 to 0,lO mm wide at the edge
31、and bevelled at an angle of not more than 15O. The marking implement shall not damage the rubber surface. 5.5 Measuring instruments The instrument for measuring the thickness of dumb-bell test pieces (and the axial thickness of ring test pieces) shall be in ac- cordance with IS0 4648, consisting ess
32、entially 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 f 5 kPal). Vernier calipers, travelling microscope or other suitable means shall be provided for the measurement of ot
33、her test piece dimensions. A calibrated cone is recommended for the measurement of the internal diameter and internal cir- cumference of ring test pieces. 6 Test piece 5.1 Dimensions Standard test pieces shall be dumb-bells or rings having dimen- sions within the limits prescribed below. Any test pi
34、ece show- ing irregularities or imperfections shall not be used. 6.1.1 Dumb-bell test piece Dumb-bell test pieces and the dies with which they are cut shall be as shown in figure 1. The dies shall have the dimensions given in table I. The reference length (the distance between the marked reference l
35、ines) shall be 25 mm for the type 1 test piece and 20 mm for the type 2 test piece. 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 pur- poses. NOTE - The dies are identical to those specified for type 1
36、and type 2 dumb-bell test pieces in IS0 37 for the determination of tensile stress- strain properties. The preferred thickness for both types of dumb-bell shall be I,5 the region of the sup- porting sheet beneath the die shall be free from cuts or other imperfections. Care should be taken to ensure
37、that the rubber is isotropic and 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 should be carried out using test pieces cut in dif- ferent directions
38、 or from different locations on 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. 6.1.2 Ring test piece The standard ring test piece shall h
39、ave a nominal internal diameter of 44,6 mm and external diameter of 52,6 mm giving a nominal radial width of 4 mm; the radial width shall nowhere deviate by more than 0,2 mm. The axial thickness shall be 1,5 IL 0,2 mm and on any one ring the thickness shall deviate from the mean by no more than 2 %.
40、 NOTE - With respect to the internal and external diameters and the tolerance on radial width, the standard ring test piece is identical to the normal-size ring test piece specified in IS0 37. Alternative axial thicknesses and radial widths may be used, provided that they are recorded in the test re
41、port, These alternatives include an axial thickness of 2,0 f 0.2 mm and the use of a ring of 2,0 rt: 0,2 mm radial width and 3.0 I!Z 0,2 mm axial thickness, the lat- ter being cut from 3 mm thick sheet or divided into two from 6 mm thick sheet. Note that a change in dimensions may change the stress
42、distribution within the cross-section of the deformed test piece and therefore may lead to different results. Comparisons should only be made between test pieces having the same dimensions. Rings shall be produced from a sheet by either die-stamping or cutting with revolving knives; in the latter ca
43、se, water may be used as a lubricant but contact should be minimized and the rubber allowed to dry thoroughly prior to test. A substrate shall be used, as for dumb-bells, and similar care should be taken to ensure that the sheet is isotropic and homogeneous. 6.2 Number of test pieces The number of t
44、est pieces required for the determination of fatigue life at each test strain depends on the purpose of the test and on the inherent variability of the materials being examined. At least five test pieces shall be tested in the case of routine quality control measurements on materials that are alread
45、y well characterized, For other purposes and particularly for rubbers that show large variability more test pieces may be required to obtain a representative result (see 9.1). Additional test pieces may be required for the determination of stress, strain energy density, and set developed during cycl
46、ing. 6.3 Storage and conditioning For all test purposes the minimum time between vulcanization and testing shall be 16 h in accordance with IS0 1826: the maximum time shall be 4 weeks unless special circumstances (such as investigation of ageing effects) otherwise dictate. Test sheets and test piece
47、s shall be stored in the dark at stan- dard laboratory temperature (see IS0 471). They shall not, at any time, be allowed to come into contact with test sheets and test pieces of a different composition. This is necessary in order to prevent additives which may affect fatigue life, such as an- tioxi
48、dants, from migrating from one vulcanizate into adjacent vulcanizates. For tests at standard laboratory temperature, test pieces shall be conditioned at this temperature for a minimum of 3 h (in ac- cordance with IS0 471) immediately before testing. For tests at other temperatures, test pieces shall
49、 be conditioned at the test temperature immediately before testing for sufficient period to reach temperature equilibrium. For tests intended to be comparable, the duration and temperature of storage, and the duration and temperature of conditioning shall be the same. 7 Test conditions 7.1 Test strains The choice and number of test strains will depend on the par- ticular project or application. For test pieces relaxed to zero strain, the test strain is the ini