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1、INTERNATIONAL STANDARD IS0 34-2 First edition 1996-l 2-15 Rubber, vulcanized or thermoplastic - Determination of tear strength - Part 2: Small (Delft) test pieces Caoutchouc vulcanisb ou thermoplastique - D W is the measured width of the blade for cutting the slit. 5.3 Number At least three and pref
2、erably six pieces shall be tested. Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/22/2007 20:42:00 MDTNo reproduction or networking permitted without license from IHS -,-,- IS0 34-2:199
3、6(E) Q IS0 5.4 Time interval between vulcanization and testing The time between vulcanization and testing shall be in accordance with IS0 471. 6 Temperature of test The test is normally carried out at a standard laboratory temperature of 23 “C f 2 “C or 27 “C f 2 “C, as specified in IS0 471. If the
4、test is to be carried out at a temperature other than a standard laboratory temperature, condition the test piece, immediately prior to testing, for a period sufficient to reach substantial temperature equilibrium at the test temperature. Keep this period as short as possible in order to avoid agein
5、g the rubber (see IS0 33831. Use the same temperature throughout any one test, as well as any series of tests intended to be comparable. 7 Procedure Mount the test piece in the testing machine so that the free length between the points of contact of the grips on the test piece is 30 mm, i.e. so that
6、 each grip is 15 mm from the slit. Stretch the test piece in the machine. Do not interrupt the stretching before the test piece has torn completely through. Note the maximum force reached during tearing. 8 Expression of results The tearing force depends on the thickness of the test piece and the wid
7、th of the rubber torn, and the result is therefore expressed as the force necessary to tear a test piece of standard width and thickness. This value, the tear strength Fo, in newtons, is given by the equation 8F Fo =b 3 where 8 is the product of the nominal values of b3 (4 mm) and d (2 mm); F is the
8、 force, in newtons, required to tear the test piece; b3 is the actual width, in millimetres, of the rubber torn in the test piece (see 5.2); d is the actual thickness, in millimetres, of the test piece. Arrange the results in order of increasing value and take as the result the average of the two me
9、dian values if the number of test pieces is even, or the median value if the number of test pieces is odd. If only three test pieces are tested, give the individual results. 9 Precision 9.1 General The calculations to determine the repeatability and reproducibility were performed in accordance with
10、ISOflR 9272. Consult this for precision concepts and nomenclature. Annex A gives guidance on the use of repeatability and reproducibility results. Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Re
11、sale, 04/22/2007 20:42:00 MDTNo reproduction or networking permitted without license from IHS -,-,- Q IS0 IS0 34-2:1996(E) 9.2 Precision details 9.2.1 An interlaboratory test programme (ITP) was organized in 1989 by the Laboratoire de Recherches et de Controle du Caoutchouc et des Plastiques (LRCCP)
12、. Test pieces prepared by LRCCP from cured sheets of three compounds A, 6 and C (the same as were used for the ITP for IS0 34-l 1 were sent out to all participating laboratories. Details of these compounds are outlined in annex B. In each laboratory, the following operations were carried out on each
13、 of the two testing days a week apart: thickness measurement, measurement of the total width outside the slit (methods 1 and 2) and, finally, tear strength measurement. For each set of measurements, two types of test piece were used: direction 1 test pieces, cut with the mill grain at 90” to the dir
14、ection of elongation; direction 2 test pieces, cut with the mill grain parallel to the direction of elongation. Five laboratories participated in the testing of test pieces whose width outside the slit was measured using method 1, seven in the testing of test pieces whose width outside the slit was
15、measured using method 2. 9.2.2 The precision determined is a type 1 precision; no mixing or curing of the test compounds was done in the participating laboratories. 9.3 Precision results The precision results for all tests are given in table 1. See annex A for guidance on using precision results. Fo
16、r comments see annex C. The symbols used in table 1 are as follows: r = repeatability, measurement units (r) = repeatability, as percentage of material average R = reproducibility, measurement units (R) = reproducibility, as percentage of material average Pooled (I-) and (R) values are calculated on
17、 the basis of pooled r and R and overall material average values. 10 Test report The test report shall include the following particulars: a) a reference to this part of IS0 34; b) all details necessary for identification of the sample tested; cl the method of measurement of the total width outside t
18、he slit; d) the tear strength, calculated in accordance with clause 8; e) the temperature of test; f) the direction of the grain in the test piece; g) the date of vulcanization, if known, and the date of testing. 7 Copyright International Organization for Standardization Provided by IHS under licens
19、e with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/22/2007 20:42:00 MDTNo reproduction or networking permitted without license from IHS -,-,- IS0 34-2: 1996(E) IS0 Table 1 - Precision results for “Delft” tear strength (N) Material Average Width outside slit measured using m
20、ethod 1 Direction 1 (mill grain perpendicular) Compound A 36.7 Compound B 32.0 Compound C 129,8 Pooled values 66,2 Direction 2 (mill grain parallel) Compound A 36,8 Compound B 31,4 Compound C 132,l Pooled values 66.8 Width outside slit measured using method 2 Direction 1 (mill grain perpendicular) C
21、ompound A 40,o Compound B 37,4 Compound C 157,0 Pooled values 78.1 Direction 2 (mill grain parallel) Compound A 40,4 Compawd B 37,2 Compound C 163.9 Pooled values 8.2.5 Within-laboratory Between-laboratory r b-1 R (RI 4.37 II,9 12.9 35.1 5,62 17,6 II,2 34.9 38.9 30,o 62,5 48,2 22.8 34,5 37.4 56.6 I,
22、68 4,57 9,96 27.1 3,99 12,7 6,96 22,2 25.8 19.5 44,5 33,7 15.6 23,4 24,3 36.3 4.73 II,8 17.2 43.2 2,37 6.23 19,0 50,8 38,5 24,5 67.7 43.2 23.6 30,2 37.2 47,7 6.73 16,7 12.3 30,7 3,69 9.a 17.0 45,6 24,Q 14,6 , 80,6 49.2 14,5 : f7,6 50,7 61,4 8 Copyright International Organization for Standardization
23、Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/22/2007 20:42:00 MDTNo reproduction or networking permitted without license from IHS -,-,- Q IS0 Annex A (informative) 1s0 34-2: 1996(E) Guidance for using precision results A.1 The general proce
24、dure for using precision results is as follows, with the symbol 1.q -x2 1 designating a positive difference in any two measurement values (i.e. without regard to sign). A.2 Enter the appropriate precision table (for whatever test parameter is being considered) at an average value (of the measured pa
25、rameter) nearest to the “test” data average under consideration. This line will give the applicable, r, (r), R or (RI for use in the decision process. A.3 With these r and (I-), values, the following general repeatability statements may be used to make decisions. A.3.1 For an absolute difference: Th
26、e difference 1x1 -x2 1 between two test (value) averages, found on nominally identical material samples under normal and correct operation of the test procedure, will exceed the tabulated repeatability r on average not more than once in twenty cases. A.3.2 For a percentage difference between two tes
27、t (value) averages: The percentage difference x,-x2( /(x1 +x2px100 between two test values, found on nominally identical material samples under normal and correct operation of the test procedure, will exceed the tabulated repeatability r on average not more than once in twenty cases. A.4 With these
28、R and (RI values, the following general reproducibility statements may be used to make decisions. A.4.1 For an absolute difference: The absolute difference IX, -x21 between two independently measured test (value) averages, found in two laboratories using normal and correct test procedures on nominal
29、ly identical material samples, will exceed the tabulated reproducibility R not more than once in twenty cases. A.4.2 For a percentage difference between two test (value) averages: The percentage difference 0x1 - 4 / (Xl + x2)/2 x 100 between two independently measured test (value) averages, found in
30、 two laboratories using normal and correct test procedures on nominally identical material samples, will exceed the tabulated reproducibility (RI not more than once in twenty cases. Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Technica
31、l Standards 1/9972545001 Not for Resale, 04/22/2007 20:42:00 MDTNo reproduction or networking permitted without license from IHS -,-,- IS0 3 the values of (r) and (R) however, which are equivalent to a coefficient of variation, do not change appreciably, while the tear strength increases by a factor
32、 of approximately four. There appears to be no consistent difference in the influence of the two methods for measuring the width outside the slit, i.e. method 1 and method 2, except with parallel mill grain testing. Here the reproducibility (R) is almost two times higher for method 2. Parallel-grain
33、 test pieces appear to be more precise (i.e. give a lower r and RI for method 1, in both within-laboratory and between-laboratory testing. For method 2, there appears to be a similar advantage with parallel-grain test pieces for within-laboratory testing, i.e. lower r and (r), but the opposite is fo
34、und for between-laboratory testing. Method 2 gives higher average tear values than method 1. The grain direction has no significant influence on the magnitude of the tear strength. Table C.l lists the results obtained in a previous ITP conducted in 1987 for IS0 34-l. The IS0 34-2 ITP made use of the
35、 same three compound formulations as the IS0 34-l programme. Thus a comparison of the precision of the two IS0 test methods is possible. This is done in table Cl. Expressed on a relative basis since the measurement units are different in the two test methods, the precision obtained with the Delft te
36、st piece is, overall, better than that obtained with the trouser test piece. This superiority can be seen for both (r) and (RI with only some minor exceptions. This is perhaps not surprising since the Delft test piece is effectively a tensile test piece with a very large “flaw”. Table C.l - Comparis
37、on of IS0 34-1 and IS0 34-2 tear strengths Material IS0 34-1 IS0 34-2 Average (i-1 (R) Average (4 (R) Trouser test piece (mill grain perpendicular) Compound A 3,68 24.7 35.0 36,7 II,9 35.1 Compound B 7,67 25.5 30,8 32.0 17,6 34.9 Compound C 22,8 38,0 60,7 129,8 30.0 48.2 Trouser test piece (mill gra
38、in parallel) Compound A 4,81 48.3 54.3 36.8 4.57 27.1 Compound B 8.34 35.0 35,0 31.4 12.7 22.2 Compound C 27.3 42,5 49,6 132,l 19.5 33,7 Die B (angle) test piece with notch (mill grain perpendicular) Compound A 13,2 29,4 35,7 36.7 II,9 35,l Compound B 14,7 40.8 40,8 32,0 17.6 34.9 Compound C 62,l 49
39、,6 60,9 129,8 30,o 48,2 Die C (crescent) test piece with notch (mill grain perpendicular) Compound A 29.9 22.8 103.7 36,7 11.9 35,l Compound B 31.1 15,l 94,6 32,0 17.6 34,9 Compound C 124.0 23,5 38,0 129.8 30,o 48.2 NOTES 1 For both sets of tests (IS0 34-l and IS0 34-2), the comparison is made on a
40、common mill grain basis (either perpendicular or parallel). 2 The results for IS0 34-2 were obtained using test pieces in which the width outside the slit was measured by method 1. 11 Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Techni
41、cal Standards 1/9972545001 Not for Resale, 04/22/2007 20:42:00 MDTNo reproduction or networking permitted without license from IHS -,-,- IS0 34-2:1996(E) ICS 83.060 Descriptors: rubber, vulcanized rubber, thermoplastic rubber, tests, mechanIcal tests, tear tests, determination, tear strength, Price based on 11 pages Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/22/2007 20:42:00 MDTNo reproduction or networking permitted without license from IHS -,-,-