1、Designation: D4482 11 (Reapproved 2017)Standard Test Method forRubber PropertyExtension Cycling Fatigue1This standard is issued under the fixed designation D4482; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last rev
2、ision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers the determination of fatigue lifeof rubber compounds undergoing a tensile-strain cycle. Duringpart of
3、the cycle, the strain is relaxed to a zero value. Thespecimens are tested without intentionally initiated flaws, cuts,or cracks. Failure is indicated by a complete rupture of the testspecimen.1.2 No exact correlation between these test results andservice is given or implied. This is due to the varie
4、d nature ofservice conditions. These test procedures do yield data that canbe used for the comparative evaluation of rubber compoundsfor their ability to resist (dynamic) extension cycling fatigue.1.3 The values stated in SI units are to be regarded asstandard. The values given in parentheses are fo
5、r informationonly.1.4 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety, health, and environmental practices and deter-mine the applicability of regulatory limita
6、tions prior to use.1.5 This international standard was developed in accor-dance with internationally recognized principles on standard-ization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recom-mendations issued by the World Trade Organization T
7、echnicalBarriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:2D3182 Practice for RubberMaterials, Equipment, and Pro-cedures for Mixing Standard Compounds and PreparingStandard Vulcanized SheetsD3767 Practice for RubberMeasurement of DimensionsD4483 Practice for Evaluating Pre
8、cision for Test MethodStandards in the Rubber and Carbon Black ManufacturingIndustries2.2 British Standard:BS5324 Guide to Application of Statistics to Rubber Test-ing33. Terminology3.1 Definitions of Terms Specific to This Standard:3.1.1 extension ratiothe ratio of the extended length of aspecimen,
9、 L, to the unextended length, Lo, calculated asfollows: 5LLo(1)3.1.2 fatigue life (sample)the geometric mean or medianvalue of the number of cycles required to cause failure for anumber of specimens of the sample.3.1.3 fatigue life (specimen)the total number of cyclesrequired to cause failure of a s
10、pecimen, defined as a completerupture or separation of the specimen.3.1.4 strain energythe energy per unit of volume requiredto deform the specimen to the specified strain. It is measuredby the area under a stress-strain curve and expressed in kJ/m3(see Annex A1).4. Summary of Test Method4.1 The dum
11、bbell test specimens are cyclically strained at afixed frequency and a series of fixed maximum extension ratiossuch that little or no temperature rise is induced. This cyclicalstraining action is called flexing. As a result of the flexing,cracks usually initiated by a naturally occurring flaw, grow
12、andultimately cause failure which is defined as complete rupture ofthe test specimen. The number of cycles to failure (fatigue life)is recorded.4.2 Fatigue, as used in this test method, implies a rupturefailure mechanism that results from the growth of flaws in thespecimen. Fatigue does not refer to
13、 the drastic alteration of thephysical-chemical rubber structure characteristic of high fre-quency flexing tests that give rise to a substantial temperatureincrease.1This test method is under the jurisdiction of ASTM Committee D11 on Rubberand Rubber-like Materials and is the direct responsibility o
14、f Subcommittee D11.15on Degradation Tests.Current edition approved Oct. 1, 2017. Published December 2017. Originallyapproved in 1985. Last previous edition approved in 2011 as D4482 11. DOI:10.1520/D4482-11R17.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Custo
15、mer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3Available from British Standards Institute, 2 Park St., London W1A 2BF,United Kingdom.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700
16、, West Conshohocken, PA 19428-2959. United StatesThis international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recommendations issued by the Wor
17、ld Trade Organization Technical Barriers to Trade (TBT) Committee.14.3 Fatigue life may be determined at each of a number ofdifferent extension ratios and the log (fatigue life) plotted as afunction of either extension-ratio or log (strain energy). Asingle extension-ratio or log (strain energy) may
18、be used forlimited comparisons of rubber vulcanizates having similarstress-strain properties and the same polymer system (seeAnnex A1).5. Significance and Use5.1 This test method covers one procedure for determiningfatigue life at various extension-ratios. The strain cycle ischaracteristic of the ty
19、pe of test apparatus specified. Experi-ence in fatigue testing shows that fatigue life may have a wide,non-normal distribution and, therefore, a large standard devia-tion that is compound dependent. Natural rubber, for example,has shown a narrower distribution than many synthetic rubbers.A large num
20、ber of specimens may, therefore, be required toyield the desired precision. Comparison of different rubbercompounds should be made with due consideration to thestandard deviation for each (see 7.1).5.2 Fatigue data, as generated in this test method, giveprimarily an estimate of the crack initation b
21、ehavior of a rubbervulcanizate and only a very approximate measure of the crackpropagation rate. The information obtained may be useful inpredicting the flex-life performance of a compound in activeservice; however, the user should be aware that in actual use,products are subjected to many other fat
22、igue factors notmeasured in this test method.6. Apparatus6.1 Fatigue Tester, consisting of framework capable ofcontaining two or more sets of multi-place specimen racks orcrossheads that hold specimens in a vertical position, side-by-side, in suitable grips. A crosshead or rack set is comprised ofon
23、e stationary bar to which grips are attached and onemoveable bar that is cycled by a cam at 1.7 6 0.17 Hz (100 610 cpm). Specimens are mounted in the grips, one specimen ineach set of upper and lower grips.6.1.1 The fatigue tester shall be capable of nominal speci-men extension ratios of 1.6 to 2.4.
24、 The extension ratio iscontrolled by the use of a cam attached to a rotating drive shaft.The eccentricity of the cam imports the characteristic straincycle to the specimen. Each cycle consists of:6.1.1.1 Increasing strain for one quarter of the cycle time,6.1.1.2 Decreasing strain for one quarter of
25、 the cycle time,and6.1.1.3 Zero imposed strain for one half of the cycle time.6.1.2 The specimen grips shall not cause premature failureoutside the restricted portion of the test specimen. This isachieved by using a dumbbell test specimen with a thickbeaded edge molded at each end of the specimen. T
26、hisspecimen is placed into grips that loosely hold it at the bead butimpose no compressive stress on it (see Fig. 1).6.2 Mold, sheets, to be used to cut specimens, can bevulcanized in a single cavity compression mold of two piececonstruction with a hard chrome finish (see Fig. 1). The cavityis 254 m
27、m (10 in.) by 78.54 mm, and has a 6.35-mm (0.25-in.)diameter bead along each lengthwise edge. Cutting guidesshould be included at 14.3 mm (0.56 in.) intervals along thebeaded edges.6.3 Press, as described in accordance with Practice D3182.6.4 Specimen CutterThe cutting die shall conform to Fig.2. Th
28、e inside faces of the reduced section shall be polished andperpendicular to the plane formed by the cutting edges for adepth of at least 5 mm (0.2 in.).6.5 Vernier CalipersCalipers capable of making measure-ments in accordance with Practice D3767, with a minimumrange of 15 mm (0.6 in.), and precisio
29、n of 0.05 mm (0.002 in.).6.6 Stress-Strain Measuring ApparatusEither of two typesmay be used:6.6.1 A machine in which the actual extension is measuredat a given dead-weight force. A stand enables masses to besuspended from the specimen. A set of masses that includes atleast one 50, one 100, two 200,
30、 two 500, and one 1000-g massshall be available.6.6.2 Alternatively, a tensile testing machine may be usedthat is capable of extending the specimen at a rate of50.0 mm min (2.0 in./min). It should automatically measureelongation to an accuracy of 65 % of the specimens originallength.6.7 MicrometerTh
31、e micrometer or thickness gauge shallconform to the specifications in Practice D3767.6.8 Bench Marker, with two parallel straight marking sur-faces ground smooth in the same plane. The surfaces shall bebetween 0.05 and 0.08-mm (0.002 and 0.003-in.) wide and23-mm (0.9-in.) long. The angle between the
32、 marking surfacesand sides shall be at least 75. The distance between themarking centers shall be 25 6 0.50 mm (0.984 6 0.020 in.).7. Sampling7.1 Sampling shall be done in a way that justifies theconclusions drawn from any particular test program in declar-ing one compound to be superior to another.
33、 In fatigue-lifemeasurement, a sampling variance that includes mix andcuring variance components shall be used.8. Specimen Preparation8.1 Compounds shall be prepared in accordance with Prac-tice D3182 and vulcanized in the specified mold with themilling-grain direction parallel to the beaded edge.8.
34、2 The molded sheet shall be conditioned in an unstrainedstate for at least 24 h at test temperature before testing.8.3 Specimens shall be cut with the die cutter at right anglesto the beaded edge. The die cutter shall be sharp and free fromnicks and oil prior to cutting. Support the sheets on a suit
35、ablecutting surface (cardboard, linoleum, etc.) covered with a thinplastic film to prevent inclusions. Cut the sheets with a single,smooth stroke.8.4 Discard specimens having obvious flaws. Before testing,physically randomize the specimens from all sheets of the samecompound.D4482 11 (2017)29. Condi
36、tioning9.1 Test TemperatureIt is suggested that the test tempera-ture be 23 6 2C.NOTE 1It is recommended that the laboratory room housing thefatigue tester be free of any ozone-generating equipment.10. Procedure10.1 Fatigue Tester:10.1.1 Install the proper cam that will give the desiredextension rat
37、io.NOTE 2If previous knowledge about fatigue life of a particularFIG. 1 Single-Cavity Compression MoldD4482 11 (2017)3compound is not available, an initial extension-ratio of 2.0 is often used.10.1.2 Adjust the distance between the flat, inner surface ofthe grips to 6 cm. A gauge block 6 cm long is
38、convenient forthis adjustment.10.1.3 If permanent set and extension-ratio measurementsare desired, place two bench marks approximately 25 mm aparton the reduced section of two specimens of each sample. Placethe marks perpendicular to the longitudinal axis and equidistantfrom the center of the specim
39、en. This distance is designated Li.10.1.4 Manually set the cam position to the minimumcrosshead separation. Mount the specimens randomly in thegrips.10.1.5 Start the fatigue tester.10.1.6 At 1000 cycles stop the tester and manually adjustthe drive mechanism to produce minimum crosshead separa-tion.N
40、OTE 3If the tester is using two sets of crossheads, follow theinstructions starting with 10.1.6 for one bank of specimens at a time.10.1.7 For each specimen, one at a time, use the gripadjustment to increase the distance between the grips until thespecimen is under a slight tension, then relieve the
41、 tension untila slight bow is just perceptable in the specimen. The specimenhas now been adjusted for permanent set.10.1.8 For specimens requiring permanent setmeasurements, measure the distance between the bench marksand record as Loto the closest 61 mm. Calculate thepermanent set using the Li meas
42、urement from 10.1.3.Permanent set, % 5 SLo2 LiLiD100! (2)NOTE 4Repeatability may be improved if the specimen is not adjustedfor permanent set.10.1.9 For those specimens requiring a strain ratio measure-ment: After the specimens have rested at zero strain for at least3 min, manually adjust the drive
43、mechanism until the speci-mens are at maximum extension. Measure the distance be-tween the bench marks and record as L to the closest 61.0 mm.Compute the extension ratio, . 5LLo(3)10.1.10 Restart the tester, readjust the permanent set at10 000 additional cycles, and then each 24 h, thereafter.10.1.1
44、1 At the end of the test, record the total cycles foreach specimen, note and record the number of failures.Terminate the test when all specimens have failed or anarbitrary number of cycles have been obtained, or an arbitrarynumber of specimens remain intact.10.1.12 Repeat steps 10.1.1 through 10.1.1
45、1 for each de-sired extension ratio.10.2 Strain Energy Determination:10.2.1 If strain energy comparisons are necessary, deter-mine stress-strain properties using either the method in 10.2.2,the Manual Machine Method, or 10.2.3, the Tensile TestingMachine Method. This is optional for single extension
46、 ratiotests.10.2.2 Manual Machine MethodMeasure the specimenwidth and thickness with the micrometer. Stretch the specimen30 times to the maximum extension used in testing. Placebench marks just short of the end of the straight, reducedsection of the specimen at maximum strain and then release tozero
47、 strain. Measure the unextended length with verniercalipers. Place sufficient force on the specimen to obtain anextension ratio of approximately 1.2 within 1 min. Increase theforce at 1 min intervals to achieve a maximum extension ratioof 2.5. Measure the extended length 0.5 min after each force isa
48、pplied.10.2.3 Tensile Machine MethodMeasure the specimenwidth and thickness with the micrometer. Stretch the specimen30 times to the maximum extension used in testing. Elongatethe specimen at 50 mm/min (2 in./min), automatically record-ing the force at every 10 % elongation increment until anextensi
49、on ratio of 2.5 (150 % elongation) is obtained. Aconstant rate of extension tensile machine may be used.11. Calculations11.1 Determine the geometric mean fatigue life for eachrubber vulcanizate at each extension. When the logarithmictransformation is applied, the mean fatigue life is determinedas follows:G 5 n=N13N23 3Nn(4)NOTE 1Cutter to be used for cutting samples from molded rubbersheets.Material: A2 tool steel.FIG. 2 Specimen CutterD4482 11 (2017)4whereG = geometic mean,Ni= fatigue life of theith specimen, andn = total number of specimens.11.1.1
