1、Designation: E274/E274M 11Standard Test Method forSkid Resistance of Paved Surfaces Using a Full-Scale Tire1This standard is issued under the fixed designation E274/E274M; the number immediately following the designation indicates the yearof original adoption or, in the case of revision, the year of
2、 last revision. A number in parentheses indicates the year of last reapproval.A superscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers the measurement of skid resis-tance of paved surfaces with a specified full-scale automotivet
3、ire.1.2 This test method utilizes a measurement representingthe steady-state friction force on a locked test wheel as it isdragged over a wetted pavement surface under constant loadand at a constant speed while its major plane is parallel to itsdirection of motion and perpendicular to the pavement.1
4、.3 The values measured represent the frictional propertiesobtained with the equipment and procedures stated herein anddo not necessarily agree or correlate directly with thoseobtained by other pavement friction measuring methods. Thevalues are intended for use in evaluating the skid resistance ofa p
5、avement relative to that of other pavements or for evaluatingchanges in the skid resistance of a pavement with the passageof time. The values are insufficient to determine the distancerequired to stop a vehicle on either a wet or a dry pavement.They are also insufficient for determining the speed at
6、 whichcontrol of a vehicle would be lost, because peak and side forcefriction are also required for these determinations.1.4 The values stated in either SI units or inch-pound unitsare to be regarded separately as standard. The values stated ineach system may not be exact equivalents; therefore, eac
7、hsystem shall be used independently of the other. Combiningvalues from the two systems may result in non-conformancewith the standard.1.5 This standard does not purport to address all of thesafety problems associated with its use. It is the responsibilityof the user of this standard to establish app
8、ropriate safety andhealth practices and determine the applicability of regulatorylimitations prior to use. For specific safety precautions, seeSection 5.2. Referenced Documents2.1 ASTM Standards:2E178 Practice for Dealing With Outlying ObservationsE501 Specification for Rib Tire for Pavement Skid-Re
9、sistance TestsE524 Specification for Smooth Tire for Pavement Skid-Resistance TestsE867 Terminology Relating to Vehicle-Pavement SystemsE1136 Specification for P195/75R14 Radial Standard Ref-erence Test TireF377 Practice for Calibration of Braking/Tractive Measur-ing Devices for Testing TiresF457 Te
10、st Method for Speed and Distance Calibration ofFifth Wheel Equipped With Either Analog or DigitalInstrumentation3. Summary of Test Method3.1 The test apparatus consists of an automotive vehiclewith one or more test wheels incorporated into it or formingpart of a suitable trailer towed by a vehicle.
11、The apparatuscontains a transducer, instrumentation, a water supply andproper dispensing system, and actuation controls for the brakeof the test wheel. The test wheel is equipped with a standardpavement test tire. See 4.4 for tire references.3.2 The test apparatus is brought to the desired test spee
12、d.Water is delivered ahead of the test tire and the braking systemis actuated to lock the test tire. The resulting friction forceacting between the test tire and the pavement surface (or someother quantity that is directly related to this force) and thespeed of the test vehicle are recorded with the
13、 aid of suitableinstrumentation.3.3 The skid resistance of the paved surface is determinedfrom the resulting force or torque record and reported as skidnumber (SN), which is determined from the force required toslide the locked test tire at a stated speed, divided by theeffective wheel load and mult
14、iplied by 100.1This test method is under the jurisdiction of ASTM Committee E17 on Vehicle- Pavement Systems and is the direct responsibility of Subcommittee E17.21 onField Methods for Measuring Tire Pavement Friction.Current edition approved Jan. 1, 2011. Published March 2011. Originallyapproved in
15、 1965. Last previous edition approved in 2006 as E274 06. DOI:10.1520/E0274_E0274M-11.2For 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 Document Summary
16、 page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.4. Apparatus4.1 VehicleThe vehicle with one test tire locked shall becapable of maintaining test speeds of 40 to 60 mph (65 to 100km/h) within 61.0 mph (61.5 km
17、/h) during a test on a levelpavement having a skid number of 50.4.2 Braking SystemThe test wheel shall be equipped witha suitable brake. The brake system shall be capable of lockingthe wheel at the conditions specified in 4.1 and maintaining thelocked-wheel condition throughout the test.4.3 Wheel Lo
18、adThe apparatus shall be of such a design asto provide an equal static load of 1085 615 lbf (4800 6 65 N)to each test wheel and on detachable trailers a static downloadof 100 to 200 lbf (450 to 900 N) at the hitch point.4.4 Tire and RimThe test tire shall be one of the standardtires for the pavement
19、 test as specified in Specification E501 orE524, and it shall be mounted on a suitable 15 by 6 in. rim. Thetire mounting for rotation consideration is important to mini-mize tread separation. The tire shall rotate clockwise whenviewed facing the serial number stamped on the tire. Therefore,when test
20、ing the left wheel path, the serial number should facethe center of the lane. Since all rims do not have the same offsetfrom the hub, replacement rims must be of the same offset toensure consistent alignment of the tire with the water path. Thedata from the two tires are not interchangeable. (1)3Alt
21、ernativetesting for special purposes may be performed with other tires,such as a radial standard reference test tire of SpecificationE1136.4.5 Instrumentation:4.5.1 General Requirements for Measuring SystemTheinstrumentation system shall conform to the following overallrequirements at ambient temper
22、atures between 40 and 100F (4and 40C):Overall system accuracy6112 % of applied load from200 lbf (900 N) to full scale; for example, at 200 lbf, appliedcalibration force of the system output shall be determinablewithin 63 lbf (614 N).Time stability of calibration10 h, min.The exposed portions of the
23、system shall tolerate 100 %relative humidity (rain or spray) and all other adverse condi-tions, such as dust, shock, and vibrations which may beencountered in highway operations.4.5.2 Force-Measuring TransducerThe tire force-measuring transducer shall be of such design as to measure thetire-road int
24、erface force with minimum inertial effects (2).Transducers are recommended to provide an output directlyproportional to force with hysteresis less than 1 % of theapplied load, nonlinearity less than 1 % of the applied load upto the maximum expected loading, and sensitivity to anyexpected cross-axis
25、loading or torque loading less than 1 % ofthe applied load. The force transducer shall be mounted in sucha manner as to experience less than 1 deg angular rotation withrespect to its measuring plane at the maximum expectedloading.4.5.3 Torque-Measuring TransducerTorque transducersprovide an output d
26、irectly proportional to torque with hyster-esis less than 1 % of the applied load and nonlinearity up to themaximum expected loading less than 1 % of the applied load.It should have sensitivity to any cross-axis loading less than1 % of the applied load.4.5.4 Additional TransducersForce transducers f
27、or mea-suring quantities such as vertical load, etc., shall meet therecommendations stated in 4.5.2.4.5.5 Vehicle Speed-Measuring TransducersTransducerssuch as “fifth wheel” or free-rolling wheel coupled tachometersshall provide speed resolution and accuracy of 6 1.5 % of theindicated speed or 60.5
28、mph (60.8 km/h), whichever isgreater. Output shall be directly viewable by the driver andshall be simultaneously recorded. Fifth wheel systems shallconform to Method F457.4.6 Signal Conditioning and Recorder System:4.6.1 Transducers that measure parameters sensitive to in-ertial loading shall be des
29、igned or located in such a manner asto minimize this effect (3). If the foregoing is not practical, datacorrection must be made for these effects if they exceed 2 % ofactual data during expected operation. All signal conditioningand recording equipment shall provide linear output and shallallow data
30、 reading resolution to meet the requirements of 4.5.1.All systems, except the smoothing filter recommended in 4.6.2,shall provide a minimum bandwidth of at least 0 to 20 Hz (flatwithin 61 %).4.6.2 It is recommended that an electronic filter, typicallybetween 4.8 Hz/-3db/4 pole Bessel-type and a 10 H
31、z/-3db/8pole Butterworth filter, selected from the types described in Ref(4) be installed in the signal conditioning circuit preceding theelectronic divider and integration calculation of SN as de-scribed in 9.4.4.6.3 All strain-gage transducers shall be equipped withresistance shunt calibration res
32、istors or equivalent that can beconnected before or after test sequences. The calibration signalshall be at least 50 % of the normal vertical load and shall berecorded.4.6.4 Tire friction force or torque and any additional desiredinputs, such as vertical load, wheel speed, etc., shall berecorded in
33、phase (65 over a bandwidth of 0 to 20 Hz).Vehicle speed shall also be recorded. All signals shall bereferenced to a common time base.4.6.5 A signal to electrical noise ratio of at least 20 to 1 isdesirable on all recorded channels.4.7 Pavement Wetting System:4.7.1 The water being applied to the pave
34、ment ahead of thetest tire shall be supplied by a nozzle conforming to thedimensions in Fig. 1. The quantity of water applied at 40 mph(65 km/h) shall be 4.0 gal 6 10 %/minin. (600 mL/minmm610 %) of wetted width. The water layer shall be at least 1 in.(25 mm) wider than the test tire tread and appli
35、ed so the tire iscentrally located between the edges. The volume of water perinch (or millimetre) of wetted width shall be directly propor-tional to the test speed (5).4.7.2 The nozzle configuration and position shall ensure thatthe water jets shall be directed toward the test tire and pointedtoward
36、 the pavement at an angle of 20 to 30. The water shallstrike the pavement 10 to 18 in. (250 to 450 mm) ahead of thevertical axes through the centerline of the test wheel. The3The boldface numbers in parentheses refer to the list of references at the end ofthis method.E274/E274M 112nozzle shall be 1
37、in. (25 mm) above the pavement or theminimum height required to clear obstacles that the tester isexpected to encounter, but in no case more than 4 in. (100 mm)above the pavement.4.7.3 Water used for testing shall be reasonably clean andhave no chemicals such as wetting agents or detergents added.5.
38、 Safety Precautions5.1 The test vehicle, as well as all attachments to it, shallcomply with all applicable state and federal laws.All necessaryprecautions shall be taken beyond those imposed by laws andregulations to ensure maximum safety of operating personneland other traffic. No test shall be mad
39、e when there is dangerthat the dispersed water may freeze on the pavement.6. Calibration6.1 SpeedCalibrate the test vehicle speed indicator at thetest speed by determining the time for traversing at constantspeed a reasonably level and straight, accurately measuredpavement of a length appropriate fo
40、r the method of timing.Load the test vehicle to its normal operating weight for thiscalibration. Record speed variations during a traverse with theskid-test system. Make a minimum of three runs at each testspeed to complete the calibration. Other methods of equivalentFIG. 1 Water NozzleE274/E274M 11
41、3accuracy may be used. Calibration of a fifth wheel shall beperformed in accordance with Method F457.6.2 Skid Resistance ForcePlace the test wheel of theassembled unit, with its own instrumentation, on a suitablecalibration platform, which has been calibrated in accordancewith Method F377, and load
42、vertically to the test load. Measurethe test wheel load within 60.5 % accuracy whenever thetransducer is calibrated. Level the transducers both longitudi-nally and laterally, such that the tractive force sensitive axis ishorizontal. This can be accomplished by minimizing thetractive force output for
43、 large variations in vertical load. Thesystem (vehicle or trailer) should be approximately levelduring this procedure. The calibration platform shall utilizeminimum friction bearings and have an accuracy of 60.5 % ofthe applied load and a hysteresis of 60.25 % of the appliedload up to the maximum ex
44、pected loading. Take care to ensurethat the applied load and the transducer sensitive axis are in thesame vertical line. Perform the tractive force calibrationincrementally to not less than 800 lbf (3600 N).7. General7.1 Test PreparationCondition new tires by running themat or near their rated load
45、and inflation pressure on the testvehicle (or on another suitable vehicle) at normal traffic speedsfor at least 200 miles (300 km) or equivalent before they areused for test purposes. Prior to each series of tests, warm up thetire by traveling for at least 5 miles (10 km) at normal trafficspeeds. In
46、spect the tire for flat spots, damage, or otherirregularities that may affect test results, and replace if it hasbeen damaged or is worn beyond the wear line. Check thetest-wheel load (if adjustable) and adjust, if necessary, prior toeach test series to within the value specified in 4.3. Set the tes
47、ttire inflation pressure at 24 6 0.5 psi (165 6 3 kPa) at ambienttemperature just before the 5 mile (10 km) warmup.7.2 Test SectionsTest sections shall be defined as sectionsof pavement of uniform age and uniform composition that havebeen subjected to essentially uniform wear. For instance, sharpcur
48、ves and steep grades shall not be included in the same testsection with level tangent sections, nor shall passing lanes beincluded with traffic lanes. Take skid-resistance measurementsonly on pavements that are free of obvious contamination.7.2.1 Steel Grated Bridge DecksThese surfaces may betested
49、using the same procedures as those used on pavementsbut the test section must include only the uniform portion of thebridge deck.7.3 Skid Resistance of a Test SectionMake at least fivedeterminations of the skid resistance, at intervals not greaterthan 0.5 mile (1 km), in each test section with the test vehicleat the same lateral position in any one lane and at eachspecified test speed. Consider the arithmetic average of alldeterminations to be the skid resistance of the test section. Ifstatistical or other criteria applied to the skid number for a longtest
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