1、Designation: D813 07 (Reapproved 2014)Standard Test Method forRubber DeteriorationCrack Growth1This standard is issued under the fixed designation D813; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A n
2、umber in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.This standard has been approved for use by agencies of the U.S. Department of Defense.1. Scope1.1 This test method covers the determination of crack
3、growth of vulcanized rubber when subjected to repeatedbending strain or flexing. It is particularly applicable to tests ofsynthetic rubber compounds which resist the initiation ofcracking due to flexing when tested by Method B of TestMethods D430. Cracking initiated in these materials by smallcuts o
4、r tears in service, may rapidly increase in size andprogress to complete failure even though the material isextremely resistant to the original flexing-fatigue cracking.Because of this characteristic of synthetic compounds, particu-larly those of the SBR type, this test method in which thespecimens
5、are first artificially punctured in the flex area shouldbe used in evaluating the fatigue-cracking properties of thisclass of material.1.2 The values stated in SI units are to be regarded as thestandard. The values given in parentheses are for informationonly.1.3 This standard does not purport to ad
6、dress all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D430 Test Me
7、thods for Rubber DeteriorationDynamicFatigueD1349 Practice for RubberStandard Temperatures forTestingD3182 Practice for RubberMaterials, Equipment, and Pro-cedures for Mixing Standard Compounds and PreparingStandard Vulcanized SheetsD3767 Practice for RubberMeasurement of DimensionsD4483 Practice fo
8、r Evaluating Precision for Test MethodStandards in the Rubber and Carbon Black ManufacturingIndustries3. Summary of Test Method3.1 A molded test specimen with a pierced groove isrepeatedly flexed on a DeMattia type machine with the flexing(bending) axis parallel to the groove. The cut length ismeasu
9、red at frequent intervals to determine the cut growth rate.The cut is initiated by a specially shaped piercing tool.4. Significance and Use4.1 The test gives an estimate of the ability of a rubbervulcanizate to resist crack growth of a pierced specimen whensubjected to bending or flexing.4.2 No exac
10、t correlation between these test results andservice is implied due to the varied nature of service condi-tions.5. Interference5.1 Presence of significant concentrations of ozone willaffect test results. Care should be taken that ambient ozoneconcentrations do not exceed 1 pphm.6. Apparatus6.1 DeMatt
11、ia Flexing MachineThe essential features ofthe apparatus, one design of which is shown in Fig. 1, are asfollows:6.1.1 The machine has an adjustable stationary head ormember provided with suitable grips for holding one end of thetest specimens in a fixed position and a similar reciprocatingmember for
12、 holding the other end of each of the specimens.6.1.2 The reciprocating member is so mounted that itsmotion is straight in the direction of and in the same plane asthe center line between the grips. The travel of the movingmember shall be adjustable and shall be obtained by means ofa connecting rod
13、and eccentric having a minimum length ratioof 10 to 1.6.1.3 The eccentric shall be driven by a motor operating atconstant speed under load and giving 5 6 0.1 Hz (300 610 cpm). Provision shall be made for a maximum travel of themoving grips of 100 mm (4 in.).1This test method is under the jurisdictio
14、n of ASTM Committee D11 on Rubberand is the direct responsibility of Subcommittee D11.15 on Degradation Tests.Current edition approved May 1, 2014. Published May 2014. Originallyapproved in 1944. Last previous edition approved in 2007 as D813 07. DOI:10.1520/D0813-07R14.2For referenced ASTM standard
15、s, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19
16、428-2959. United States16.1.4 The machine may be designed so that all the speci-mens are mounted on a single bar and all are flexed at the sametime. A double bar may also be used in which case thosespecimens mounted on one bar are being flexed while those onthe other bar are being straightened. Such
17、 an arrangementimproves the smoothness of operation.6.2 MoldA mold for curing individual test specimens isrequired, preferably of a multiple cavity design and havingadequate overflow cavities. The cavity plate shall have aminimum thickness of about 20 mm (0.750 in.) and the coverplate a minimum thic
18、kness of 14.5 mm (0.575 in.). Refer toPractice D3182.NOTE 1The curing of wide samples from which specimens may be cutmay be provided for by increasing the width of the cavity and maintainingall other dimensions.6.3 Measuring Scale of suitable length, graduated in milli-metres (or 0.01 in.) for measu
19、ring the length of cut growth.6.4 Micrometer, to measure the thickness of the test speci-men as specified in Practice D3767, Procedure A2.7. Test Specimens7.1 The test specimens shall consist of molded or cut strips,conforming to the shape and dimensions given in Fig. 2. Theyshall have a smooth surf
20、ace and be free of surface irregularitiesand defects in the groove and adjacent area. The thickness shallbe measured in the area adjacent to the groove and results shallbe compared only between specimens having a thickness of 6.46 0.1 mm (0.250 6 0.005 in.).7.2 Test specimens shall be conditioned in
21、 accordance withSection 13.NOTE 2The thickness of a test specimen cured from a tread typecompound consisting of 100 parts rubber and 50 parts of IRB Number 6black, and the necessary curative materials and using the mold shown inFig. 3, will conform to the thickness of 6.4 mm (0.250 in.) specified in
22、 Fig.FIG. 1 DeMattia Tester with a Double Row of Specimens Mounted for Flex-Cracking TestD813 07 (2014)22. Preparation of the uncured specimens, on the basis of a constant volumeplus an approximate overflow of 10 %, provides assurance of well-moldedspecimens of uniform thickness.7.3 Compounds differ
23、ing in stiffness may be expected todeviate from the thickness of 6.4 mm (0.250 in.) as obtainedwith the standard compound referred to above. Extreme casesresulting in thickness outside the tolerances may requireadditional study. It is recommended that a new averagethickness be determined for such co
24、mpounds, based on aminimum of ten specimens, and the allowable tolerance thenbe applied to this revised thickness measurement. The report ofthe data should then include such deviations from the control.8. Number of Test Specimens8.1 At least three specimens of each sample or compoundshall be tested
25、and the median value reported. It is desirable,when possible, to test a set of control specimens of knowncrack-growth resistance with each set of test specimens.9. Preparation of Specimens9.1 Each test specimen shall be prepared by piercing thebottom of the groove at a point equidistant from the sid
26、es. Thetool shall be maintained perpendicular to both the traverse andlongitudinal axes and the cut accomplished by a single inser-tion and withdrawal of the tool. The dimension H (of Fig. 4)ofthe tool shall be parallel and centered with the longitudinal axisof the groove. The leading cutting edge o
27、f the tool shallcompletely penetrate the specimen and project through thespecimen a minimum of 3.2 mm (0.125 in.). Lubrication withwater containing a suitable wetting agent may be used. Thepiercing tool shall be a spear-type instrument conforming to thedimensions given in Fig. 4. It is imperative th
28、at the tool is sharpand maintained to the correct dimensions, or test results will beaffected. It is recommended that the piercing tool be held in asuitable apparatus3that will maintain the tip in a perpendicularplane to the specimen and allow it to be pierced in onecontinuous motion.3The sole sourc
29、e of supply of the piercing tool and apparatus known to thecommittee at this time is CCSI, 221 Beaver St., Akron, OH 44304. If you are awareof alternative suppliers, please provide this information to ASTM InternationalHeadquarters. Your comments will receive careful consideration at a meeting of th
30、eresponsible technical committee,1which you may attend.AB C D Emmin.15067532.39 0.030.094 0.0016.35 0.130.250 0.005251FIG. 2 Test Specimen with Circular GrooveABCmmin.6.45 0.030.254 0.0014.78 0.0510.188 0.0022.39 0.030.094 0.001FIG. 3 Test Specimen Moldmm (in.)A 2.62 (0.103)B 44.5 04 (1.75 0.015)C 3
31、.8 0.4 (0.150 0.015)D 10.3 0.1 (0.400 0.005)E 0.38 + 0.05 0.00 (0.015 + 0.002 0.000)F 1.00 + 0.05 0.00 (0.041 + 0.002 0.000)G 0.3 + 0.05 0.00 (0.015 + 0.002 0.000)H 2.03 + 0.05 0.00 (0.080 + 0.002 0.000)I 25 rad (1.0 rad)J 58.42 (2.300)FIG. 4 Piercing ToolD813 07 (2014)310. Clamping Specimens in Mac
32、hine10.1 One end of the specimen shall be clamped in thestationary grip and the other in the movable grip, care beingtaken to see that the longitudinal axis of the specimen isparallel to the direction of motion.10.2 The circular groove of the clamped specimens shall belocated symmetrically, midway b
33、etween the clamps. The speci-mens may be mounted on the machine most conveniently byholding them properly spaced in parallel positions in a specialrack. The distance between the outer edges of the side bars ofthe rack shall be equal to the space between the jaws of thetesting machine when positioned
34、 for holding the specimenswithout tension. The specimens can be mounted on the testingmachine by bringing the jaws into contact with the mountingrack and tightening the clamps on the projecting ends of thespecimens.10.3 The specimens shall not be closer than 3 mm(0.125 in.) when mounted in the machi
35、ne. The free length (notin tension) of the specimen between the clamps shall be75.9 + 0.3 or 0.0 mm (2.99 + 0.01 or 0.00 in.).10.4 The circular groove shall be so restrained that it willbecome the outer surface of the bent specimen.11. Adjustment of Machine11.1 The positions of the stationary and mo
36、vable gripsrelative to each other and the length of the eccentric arm andconnecting rod shall be adjusted so that during each stroke ofthe machine the grips approach each other to a distance of 19.06 0.1 mm (0.750 6 0.005 in.) and separate to a distance of75.9 + 0.3 or 0.0 mm (2.99 + 0.01 or 0.00 in
37、.).11.2 Parallelism of the grips must be maintained at all timesand can only be assured by periodic checks.11.3 Machines operating within enclosures may be subjectto conditions resulting in different rates of cracking fordifferent positions in the grips. Correlation between all posi-tions should be
38、determined for each machine, using a standardcontrol compound, and corrections made when necessary.12. Procedure12.1 After adjustments of the apparatus and specimens havebeen completed, start the machine and record the time. At theend of any period of operation, calculate the number of flexingcycles
39、 by multiplying the observed time in minutes by themachine rate of 5 Hz (300 cpm). This shall also be checked bymeans of a counter on the machine.12.2 Since the rate of crack growth is important, takefrequent readings early in the test. Stop the machine after 1000,3000, and 5000 cycle periods, obser
40、ve the specimens, andmeasure the length of the developed crack to the nearest0.3 mm (0.01 in.) with an accurate scale, preferably metric.12.3 For improved precision, make the observation with theaid of a low-powered reticulated magnifying glass while thegrips are separated 65.0 mm (2.56 in.).12.4 Co
41、ntinue the test with readings at regular intervalsuntil a crack at least 12.5 mm (0.5 in.) in length is developed.Continuation to break may be desirable when testing agedspecimens or when operating at elevated temperatures. Theinitial cut produced by the puncturing spear shown in Fig. 4 is2 6 0.1 mm
42、 (0.08 + 0.002 0.000 in.) in width.13. Temperature of Test13.1 The standard temperature for testing shall be 23 6 2C(73.4 6 3.6F). Specimens shall be conditioned for at least12 h prior to testing. Controlled temperatures outside thestandard range are acceptable and often desirable. Special noteof su
43、ch temperatures shall appear in the report.NOTE 3The standard test temperature herein specified is that pre-scribed for the Standard Laboratory Atmosphere in Practice D1349. Anychanges or revisions hereafter in Practice D1349 relating to the standardtest temperature shall be considered effective at
44、once for this procedure.14. Report14.1 The molded dimensionsA, C, D, and E (as specified inFig. 2) of the test specimen shall be reported.14.1.1 The dimensions shall be obtained in accordance withPractice D3767 except that the dimensions shall be obtainedusinga2mmspherical radius contact foot.14.2 T
45、he crack growth data may be reported in any one ofthree ways, as follows:14.2.1 As the number of cycles required to reach a specifiedcrack length; for example, from 2 mm to 20 mm (0.080 to0.80 in.);14.2.2 As the average rate of crack growth over the entiretest period;14.2.3 As the rate of cracking i
46、n millimetres per kilocycleduring a portion of the test, for example:(a)2to4mm,(b)4to8mm,or(c)8to12mm.15. Precision and Bias415.1 This precision and bias section has been prepared inaccordance with Practice D4483. Please refer to this practicefor terminology and other statistical calculation details
47、.15.2 Two precision evaluation programs have been con-ducted for this test method.15.2.1 Program 1 was conducted in 1985 with five differentlaboratories testing four different compounds on two separatedays. The measured parameter is the flexlife in kilocycles to acrack length of 12.5 mm. A test resu
48、lt is defined as the mean(average) of the flexlife for two different test specimens.15.2.2 Program 2 was conducted in 1993 using a revisedprocedure as stipulated in the latest edition of this test method.In this program five different laboratories tested three com-pounds on two separate days. Two me
49、asured parameters wereevaluated for this program:(1) the flexlife in kilocycles to 300 % crack growth, and(2) the flexlife (in kc) to 600 % crack growth.A test result for either parameter is the mean (average) ofthree specimens.4Supporting data have been filed at ASTM International Headquarters and maybe obtained by requesting Research Report RR:D11-1041.D813 07 (2014)415.3 The precision results in this precision and bias sectiongive an estimate of the precision of this test method with thematerials (rubbers,
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