1、Designation: F 724 94a (Reapproved 2004)Standard Test Method forOutdoor Evaluation of Tire Sidewall Component CrackingResistance1This standard is issued under the fixed designation F 724; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revis
2、ion, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers procedures for evaluating pas-senger car tires for sidewall component integr
3、ity and crackingresistance, using an outdoor roadwheel.1.2 This test method evaluates the resistance of tire side-walls to dynamic weathering, atmospheric ozone cracking,fatigue cracking, or openings of splices within, or of juncturesbetween, sidewall components and cracking at molded side-wall elem
4、ents.1.3 This test method is useful for evaluating tire blacksidewalls, white sidewalls, and coverstrips.1.4 This test method is limited to comparative performancetesting between a “control” sidewall component or assemblyand one or more experimental alternatives that are built ontothe same tire (“mu
5、ltisection”) or onto tires that are identical inall respects other than the sidewall variation.1.5 This test method is not applicable to evaluation ofsidewall resistance to abrasion, as may be experienced insevere cornering or curb scuffing.1.6 The values stated in SI units are to be regarded as the
6、standard.1.7 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 and health practices and determine the applica-bility of regulatory limitations prior to use. For s
7、pecificprecaution statements, see 5.2.2. Referenced Documents2.1 ASTM Standards:2D 518 Test Method for Rubber DeteriorationSurfaceCrackingD 1149 Test Method for Rubber DeteriorationSurfaceOzone Cracking in a ChamberD 1171 Test Method for Rubber DeteriorationSurfaceOzone Cracking Outdoors or Chamber
8、(Triangular Speci-mens)D 3395 Test Methods for Rubber DeteriorationDynamicOzone Cracking in a ChamberF 538 Terminology Relating to the Characteristics and Per-formance of Tires3. Terminology3.1 Definitions:3.1.1 black sidewall, na sidewall on which only blackcompounds comprise the outer visible surf
9、ace of a tire.(F 538)3.1.2 clinch strip, nhigh-modulus or high-hardness com-pound applied between the carcass and the sidewall in the beadarea to reinforce the bead. (F 538)3.1.3 coverstrip, na thin layer of black compound thatcovers the unexposed white sidewall portion of a finished tire.(F 538)3.1
10、.4 crazing, nminute, closely grouped, generally super-ficial cracks that usually result from light-activated oxidation.(F 538)3.1.5 flex cracking, vcracking primarily caused by appli-cation of mechanical stress-strain cycling. (F 538)3.1.6 juncture, nthe interface between two different tirecomponent
11、s or different compounds within the same compo-nent. (F 538)3.1.7 juncture cracking, na crack with opening originat-ing at a juncture between two components. (F 538)3.1.8 juncture opening, na separation developing in ajuncture. (F 538)3.1.9 rim strip, na layer of compound, with or withoutfabric rein
12、forcement, that is applied at the bead to protect thecarcass plies against damage from mounting tools and from rimchafing during service. (F 538)3.1.10 sidewall, nof a tire, that portion of a tire betweenthe tread and the bead. (F 538)3.1.11 sidewall component, nan individual part of thesidewall con
13、struction, either a separate compound or a sepa-rately assembled piece. (F 538)1This test method is under the jurisdiction of ASTM Committee F09 on Tiresand is the direct responsibility of Subcommittee F09.30 on Laboratory (Non-Vehicular) Testing.Current edition approved Dec. 1, 2004. Published Dece
14、mber 2004. Originallyapproved in 1981. Last previous edition approved in 2000 as F 724 94a (2000).2For referenced ASTM standards, 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 Docu
15、ment Summary page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.3.1.12 sidewall rubber, nthe exterior rubber layer of a tirethat extends over the sidewall part of the carcass. (F 538)3.1.13 splice, nthe joint for
16、med either by overlapping orbutting the ends of a given tire component in the course ofassembling the tire. (F 538)3.1.14 splice crack, na crack originating at a splice.(F 538)3.1.15 splice opening, na parting of a splice along theinterface of the assembled ends of a given component.(F 538)3.1.16 ve
17、neer, na thin layer of rubber covering the surfaceof the tire sidewall. (F 538)3.1.17 weather cracking, ndistinct surface cracks inducedby action of ozone in those areas of sidewall that are undertension; the cracks usually form perpendicularly to the direc-tion of stress.3.1.18 white sidewall, na s
18、idewall that contains a white(or light-colored) compound as a part of the total sidewall.(F 538)4. Significance and Use4.1 Test Methods D 518, D 1149, D 1171, and D 3395 canbe used to evaluate different aspects of fatigue and weathercracking resistance of sidewall component materials in theform of t
19、est specimens. The present method applies to com-plete tires that are subjected to actual weather exposureconditions. The present method is satisfactory for research anddevelopment purposes but is not applicable to regulatorystatutes or purchase specifications until standard classificationsof state
20、of cracking, similar to those in Test Method D 1171,can be established.5. Apparatus5.1 Outdoor RoadwheelAn apparatus situated outdoorsand consisting of:5.1.1 One or more smooth steel road wheels of specifieddiameter. The road wheel(s) shall be wide enough to extendbeyond the test tire foot print wid
21、th. The road wheel diametershall be no less than 610 mm (24 in.). Smaller diameter wheelsmay produce excessive flexing and premature extraneous tirefailure.5.1.2 Satellite stations for loading several test tires againstthe road wheel with known constant force.5.1.2.1 Each satellite station can indiv
22、idually unload andwithdraw the tire from contact with the road wheel in the eventof an inflation pressure loss or other potentially catastrophicoccurrence.5.1.2.2 The tire-loading system may be done by any systemthat provides a constant force to maintain the desired tiredeflection throughout the tes
23、t.5.1.3 A drive motor that can drive the road wheel(s), within61 % of a set test speed for extended periods of time. Acommonly used speed is 48 km/h (30 mph).5.1.4 System for determining accumulated cycles of rota-tion of each test tire.5.2 Safety Precautions:5.2.1 The apparatus shall be surrounded
24、by a suitableenclosure to trap tire fragments in the event of a catastrophicfailure during the test.5.2.2 The controls for the apparatus shall be situated outsidethe enclosure.6. Sampling6.1 A sampling plan is not applicable since this test methodis intended for research and development testing only
25、. Testspecimens (see Section 7) shall be tested simultaneously witha control specimen for direct comparison of relative perfor-mance.7. Test Specimens7.1 A test specimen shall be a given assembly of sidewallcomponents, specific as to component formulations, assemblycross-section geometry, and prepar
26、ation procedure. The testspecimen may cover the entire sidewall circumference of thetest tire and be compared with a control tire or it may cover asection of the sidewall and be compared with a control sectionand other test specimen sections built onto the same (multi-section) tire.7.2 A test specim
27、en section shall cover14 of the circumfer-ence of the tire sidewall.7.3 In multisection tire tests, only specimens on the sameside of the tire shall be compared directly.8. Selection and Preparation of Test Tires8.1 All test tires shall be approximately the same age andsubjected to the same pretest
28、conditions, particularly as relatedto heat and ultraviolet exposure.8.2 Multisection test tires shall have been prepared with thetest components (for example, varied compounds) having thesame cross-sectional profile and dimensions, so as to avoidextraneous mechanical stress variability between the c
29、ompo-nents, unless the profile variation is a test variable.8.3 The test component surfaces of tires shall be washedwith water to remove any temporary protective coating butshall not be subjected to solvent or other surface treatment (inthe process of mounting, etc.) that may affect performanceunles
30、s this is a part of the experimental study.9. Procedure9.1 Mount a test tire on a rim contour approved by the Tireand Rim Association3for its particular size. For tire-to-tirecomparative tests, rims shall be of the same width.9.2 Mount the tire with the valve at a convenient referencepoint for descr
31、ibing the locations of cracks or other degradationas they occur.9.3 Inflate the tire to the selected test pressure at ambienttemperature. A commonly used inflation pressure is 138 kPa(20 psi). This pressure facilitates the desired deflection of thetire (see 9.4.2) with moderate axle loading.9.4 Inst
32、all the tire on the test machine. Give the tire a minuterun at full (test) load to ensure that the beads have fully seated.Unload the tire and allow it to return to ambient temperature.Adjust inflation pressure to the selected test pressure. Reload3Available from the Tire and Rim Association, Inc.,
33、Crown Pointe, Suite 150,175 Montrose West Ave., Copley, OH 44321.F 724 94a (2004)2the tire and adjust the load to achieve the specified deflection,while the tire is stationary and in equilibrium with ambienttemperature.9.4.1 Measure deflection by some means accurate to 61%of deflection. A useful mea
34、suring device and method aredescribed in Annex A1.9.4.2 Select the deflection to yield a relatively severesidewall flexing without early durability failure of the tire. Use30 % deflection for radial tires, 20 % for bias tires. Use lowerdeflection if the above levels produce early durability failure
35、oftires.9.5 Run the test tire against the road wheel continuously atthe set axle loading associated with the initial inflation, theselected deflection, and selected speed, except for periodicinspection shutdowns.9.6 Inspections of test tires are made commonly at two-dayintervals.9.6.1 Inspection inc
36、ludes:9.6.1.1 Close visual (unmagnified) examination of the testcomponent areas for crack initiation and propagation or otherdegradation development. In a multisection test tire, compo-nent performance should not be evaluated within 50 mm (2 in.)of segment junctures.9.6.1.2 Examination of the tire f
37、or extraneous durabilityproblems.9.6.1.3 Inflation pressure and loaded deflection checks afterthe tire has cooled to ambient temperature. Air pressure isadjusted if necessary to return to the original cold startingpressure level.NOTE 1Cold tire deflections are used. Use of warm (from running)tire de
38、flection is not feasible due to cool down errors when a number oftires are run simultaneously, and they must be measured for deflectionsequentially during inspection shutdowns.9.6.1.4 In the final inspection, measure the inflation pressurefor comparison with the original value.9.7 Test duration is d
39、iscretionary but generally need notexceed 64 000 km (40 000 miles), which requires 56 to 60days.9.8 Data sheet formats for recording test conditions, peri-odic inspection data, and observations appear in Figs. 1 and 2.10. Report10.1 Full description of the tire, including brand, serialnumber, size,
40、basic construction, and test variable constructionfeatures, etc.10.2 Rim diameter, width and contour.10.3 Description of test machine and operation conditions:10.3.1 Road wheel diameter,10.3.2 Road wheel speed,10.3.3 Axle load,10.3.4 Tire inflation pressure, cold starting at ambient tem-perature,10.
41、3.5 Loaded tire deflection, cold starting,10.3.6 Total tire test time and cycles of rotation or equiva-lent travel distance,10.3.7 Inclusive dates between which the test was run, and10.3.8 Specific data characterizing atmospheric conditions,such as ozone concentration, solar radiation, rain, chemica
42、lagents, and ambient temperature shall be recorded if available,but are not necessary since the test always involves a controltire or tire multisection(s) running concurrently with the testtires or multisection(s), as the base line for assessing relativeperformance.10.4 Test Results:10.4.1 Notations
43、 describing the types of flaws initiated (thatis, cracks, openings, etc.), their number, and approximatedimensions (length and depth) or qualitative comments ifmeasurements are not feasible.10.4.2 Elapsed test time and tire cycles of rotation, at whichflaws initiated or progressed significantly.10.4
44、.3 Only major differences in flaw development aresignificant in comparing relative performance of test speci-mens. For example, general occurrence of or deep penetrationof flaws of a given type in white sidewall A versus essentiallyno occurrence in white sidewall B.10.5 Notations of inflation pressu
45、re adjustments requiredduring the test.10.6 Inflated, unloaded tire section width and height beforeand after test measured at ambient temperature and the originalinflation pressure.11. Precision and Bias11.1 No statement is made about either the precision or biasof this test method since the result
46、merely states whether thereis conformance to the criteria for success specified in thisprocedure.12. Keywords12.1 component; cracking; evaluation; outdoor; resistance;road wheel; sidewall; tireF 724 94a (2004)3FIG. 1 Data Recording FormatF 724 94a (2004)4FIG. 2 Data Recording FormatF 724 94a (2004)5
47、ANNEX(Mandatory Information)A1. TIRE DEFLECTION MEASUREMENT METHODA1.1 Percent deflection is defined, in accordance with the Tmove scale base against the edge of the road wheel toensure proper alignment. Lock foot bar with screw A.A1.5.3 Adjust probe to lightly contact rim flange outer edgeas in the
48、 humeasurement.A1.5.4 Lock probe rod in position with screw D and nut F.A1.5.5 Remove the device from tire and read hl, the probepoint distance above the bottom of the foot bar, from the hlscale. Repeat the measurement to confirm the reading.A1.5.6 Rotate the tire to place the second measurementloca
49、tion at the center of the road wheel contact area.A1.5.7 Repeat the hlmeasurement as described inA1.5.2-A1.5.5.ASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentionedin this standard. Users of this standard are expressly advised that determination of the validity of any such patent rights, and the riskof infringement of such rights, are entirely their own responsibility.This standard is subject to revision at any time by the responsible technical committee and must be reviewed ever
