1、Designation: F724 94a (Reapproved 2016)Standard Test Method forOutdoor Evaluation of Tire Sidewall Component CrackingResistance1This standard is issued under the fixed designation F724; the number immediately following the designation indicates the year of originaladoption or, in the case of revisio
2、n, the year of last revision. A number in parentheses indicates the year of last reapproval. A superscriptepsilon () 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 integrity
3、 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 element
4、s.1.3 This test method is useful for evaluating tire blacksidewalls, white, or other colored, 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 ontoth
5、e same tire (“multisection”) 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
6、 regarded as thestandard.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 pri
7、or to use. For specificprecaution statements, see 5.2.2. Referenced Documents2.1 ASTM Standards:2D518 Test Method for Rubber DeteriorationSurfaceCracking (Withdrawn 2007)3D1149 Test Methods for Rubber DeteriorationCracking inan Ozone Controlled EnvironmentD1171 Test Method for Rubber DeteriorationSu
8、rfaceOzone Cracking Outdoors (Triangular Specimens)D3395 Test Methods for Rubber DeteriorationDynamicOzone Cracking in a Chamber (Withdrawn 2007)3F538 Terminology Relating to the Characteristics and Per-formance of Tires3. Terminology3.1 Definitions:3.1.1 black sidewall, na sidewall on which only bl
9、ackcompounds comprise the outer visible surface of a tire. F5383.1.2 clinch strip, nhigh-modulus or high-hardness com-pound applied between the carcass and the sidewall in the beadarea to reinforce the bead. F5383.1.3 coverstrip, na thin layer of black compound thatcovers the unexposed white sidewal
10、l portion of a finished tire.F5383.1.4 crazing, nminute, closely grouped, generally super-ficial cracks that usually result from light-activated oxidation.F5383.1.5 flex cracking, vcracking primarily caused by appli-cation of mechanical stress-strain cycling. F5383.1.6 juncture, nthe interface betwe
11、en two different tirecomponents or different compounds within the samecomponent. F5383.1.7 juncture cracking, na crack with opening originatingat a juncture between two components. F5383.1.8 juncture opening, na separation developing in ajuncture. F5383.1.9 rim strip, na layer of compound, with or w
12、ithoutfabric reinforcement, that is applied at the bead to protect thecarcass plies against damage from mounting tools and from rimchafing during service. F5381This test method is under the jurisdiction of ASTM Committee F09 on Tiresand is the direct responsibility of Subcommittee F09.30 on Laborato
13、ry (Non-Vehicular) Testing.Current edition approved Jan. 1, 2016. Published February 2016. Originallyapproved in 1981. Last previous edition approved in 2010 as F724 94a (2010)1.DOI: 10.1520/F0724-94AR16.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Se
14、rvice at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3The last approved version of this historical standard is referenced onwww.astm.org.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Co
15、nshohocken, PA 19428-2959. United States13.1.10 sidewall, nof a tire, that portion of a tire betweenthe tread and the bead. F5383.1.11 sidewall component, nan individual part of thesidewall construction, either a separate compound or a sepa-rately assembled piece. F5383.1.12 sidewall rubber, nthe ex
16、terior rubber layer of a tirethat extends over the sidewall part of the carcass. F5383.1.13 splice, nthe joint formed either by overlapping orbutting the ends of a given tire component in the course ofassembling the tire. F5383.1.14 splice crack, na crack originating at a splice. F5383.1.15 splice o
17、pening, na parting of a splice along theinterface of the assembled ends of a given component. F5383.1.16 veneer, na thin layer of rubber covering the surfaceof the tire sidewall. F5383.1.17 weather cracking, ndistinct surface cracks inducedby action of ozone in those areas of sidewall that are under
18、tension; the cracks usually form perpendicularly to the direc-tion of stress.3.1.18 white sidewall, na sidewall that contains a white(or light-colored) compound as a part of the total sidewall.F5384. Significance and Use4.1 Test Methods D518, D1149, D1171, and D3395 can beused to evaluate different
19、aspects of fatigue and weathercracking resistance of sidewall component materials in theform of test 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 ap
20、plicable to regulatorystatutes or purchase specifications until standard classificationsof state of cracking, similar to those in Test Method D1171, canbe established.5. Apparatus5.1 Outdoor RoadwheelAn apparatus situated outdoorsand consisting of:5.1.1 One or more smooth steel road wheels of specif
21、ieddiameter. The road wheel(s) shall be wide enough to extendbeyond the test tire foot print width. 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 tes
22、t tires againstthe road wheel with known constant force.5.1.2.1 Each satellite station can individually 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 an
23、y systemthat provides a constant force to maintain the desired tiredeflection throughout the test.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 cycle
24、s of rota-tion of each test tire.5.2 Safety Precautions:5.2.1 The apparatus shall be surrounded 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 pl
25、an is not applicable since this test methodis intended for research and development testing only. 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 sidew
26、allcomponents, specific as to component formulations, assemblycross-section geometry, and preparation 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 se
27、ctionand other test specimen sections built onto the same (multi-section) tire.7.2 A test specimen 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 Te
28、st Tires8.1 All test tires shall be approximately the same age andsubjected to the same pretest 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-sectio
29、nal profile and dimensions, so as to avoidextraneous mechanical stress variability between thecomponents, 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
30、 or other surface treatment (inthe process of mounting, etc.) that may affect performanceunless this is a part of the experimental study.9. Procedure9.1 Mount a test tire on a rim contour approved by the Tireand Rim Association4for its particular size. For tire-to-tirecomparative tests, rims shall b
31、e of the same width.9.2 Mount the tire with the valve at a convenient referencepoint for describing the locations of cracks or other degradationas they occur.4Available from the Tire and Rim Association, Inc., Crown Pointe, Suite 150,175 Montrose West Ave., Copley, OH 44321.F724 94a (2016)29.3 Infla
32、te 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 Install the tire on the test machine. Give the tire a minuterun at full (test
33、) 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. Reloadthe tire and adjust the load to achieve the specified deflection,while the tire is stationary and in equilibrium with ambient
34、temperature.9.4.1 Measure deflection by some means accurate to 61%of deflection. A useful measuring 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, 2
35、0 % for bias tires. Use lowerdeflection if the above levels produce early durability failure 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 shutd
36、owns.9.6 Inspections of test tires are made commonly at two-dayintervals.9.6.1 Inspection includes: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 shoul
37、d not be evaluated within 50 mm (2 in.)of segment junctures.9.6.1.2 Examination of the tire for 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 s
38、tartingpressure level.NOTE 1Cold tire deflections are used. Use of warm (from running)tire deflection 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
39、, measure the inflation pressurefor comparison with the original value.9.7 Test duration is discretionary 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 Fig
40、s. 1 and 2.10. Report10.1 Full description of the tire, including brand, serialnumber, size, 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 spe
41、ed,10.3.3 Axle load,10.3.4 Tire inflation pressure, cold starting at ambienttemperature,10.3.5 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 charac
42、terizing atmospheric conditions,such as ozone concentration, solar radiation, rain, chemicalagents, 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 multisectio
43、n(s), as the base line for assessing relativeperformance.10.4 Test Results:10.4.1 Notations 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
44、 time and tire cycles of rotation, at whichflaws initiated or progressed significantly.10.4.3 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 sidewa
45、ll A versus essentiallyno occurrence in white sidewall B.10.5 Notations of inflation pressure 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 N
46、o statement is made about either the precision or biasof this test method since the result merely states whether thereis conformance to the criteria for success specified in thisprocedure.12. Keywords12.1 component; cracking; evaluation; outdoor; resistance;road wheel; sidewall; tireF724 94a (2016)3
47、FIG. 1 Data Recording FormatF724 94a (2016)4ANNEX(Mandatory Information)A1. TIRE DEFLECTION MEASUREMENT METHODA1.1 Percent deflection is defined, in accordance with the Tother suitable parameters may also be used.FIG. 2 Data Recording FormatF724 94a (2016)5A1.4.3 Adjust the probe rod laterally, and
48、vertically in thescale slot, to lightly contact the outer edge of the rim flange.Lock the probe position.A1.4.4 Remove the device from the tire and read hu, theprobe distance above the top of the foot, from the huscale.Repeat the measurement to confirm the reading.A1.4.5 Repeat the humeasurement at
49、the second location.A1.5 To measure hl, refer to Fig. A1.2.A1.5.1 Rotate the tire to place the first measurement loca-tion at the center of the road wheel contact area.A1.5.2 Slightly loosen both locking screws and the proberod locking nut on measuring device. Position foot bar Bagainst road wheel running surface at center of tire contactarea; move 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 humeasurement.A1.5.4 Lock probe rod
