1、Designation: E 1911 98 (Reapproved 2002)Standard Test Method forMeasuring Paved Surface Frictional Properties Using theDynamic Friction Tester1This standard is issued under the fixed designation E 1911; the number immediately following the designation indicates the year oforiginal adoption or, in th
2、e case of revision, 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 the procedure for measuringpaved surface frictional propertie
3、s as a function of speed usingthe Dynamic Friction Tester (DF-Tester).1.2 The DF Tester consists of a horizontal spinning diskfitted with three spring loaded rubber sliders which contact thepaved surface as the disk rotational speed decreases due to thefriction generated between the sliders and the
4、paved surface. Awater supply unit delivers water to the paved surface beingtested. The torque generated by the slider forces measuredduring the spin down is then used to calculate the friction as afunction of speed.1.3 The DF Tester can be used for laboratory investigationsand in the field on actual
5、 paved surfaces.1.4 The values stated in SI (metric) units are to be regardedas standard. The inch- pound equivalents are rationalized,rather than exact mathematical conversions.1.5 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is therespons
6、ibility 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:E 274 Test Method for Skid Resistance of Paved SurfacesUsing a Full-Scale Tire2E 501 Specificat
7、ion for Standard Rib Tire for PavementSkid-Resistance Tests2E 867 Terminology Relating Vehicle-Pavement Systems2E 1845 Practice for Calculating Pavement MacrotextureMean Profile Depth23. Terminology3.1 Definitions:For Definitions of terms pertaining to this standard, seeTerminology E 867.4. Summary
8、of Test Method4.1 This test method uses a disk that spins with its planeparallel to the test surface. Three rubber sliders are mounted onthe lower surface of the disk. The disk work pavement isbrought to the desired rotational velocity, corresponding to themaximum tangential velocity of the sliders.
9、 The DF Tester iscapable of providing a maximum tangential velocity of 90km/h (55 mph).4.2 Water is introduced in front of the sliders and the disk islowered to contact the test surface so that it bears the fullvelocity of the disk and model assembly.4.3 The torque is monitored continuously as the d
10、isk rota-tional velocity reduces due to the friction between the slidersand the test surface.4.4 The torque signal is reduced to a measurement offriction by converting the torque to the force on the sliders anddividing by the weight of the disk and motor assembly.4.5 The friction at 20, 40, 60, and
11、80 km/h (12, 24, 36, and48 mph) is recorded and the friction - speed relationship maybe plotted.5. Significance and Use5.1 This test method provides a measure of surface frictionas a function of sliding speed, either in the field or in alaboratory.5.2 This test method may be used to determine the re
12、lativeeffects of various polishing techniques on materials or materialcombinations.5.3 The values measured in accordance with this method donot necessarily agree or directly correlate with those obtainedutilizing other methods of determining friction properties orskid resistance.6. Apparatus6.1 DF T
13、ester (see Fig. 1)The measuring instrumentconsists of a main body and a control unit. A portable personalcomputer or an X-Y plotter can be used to record the data. Fig.1 shows the DF Tester measuring unit, consisting of a fly wheeland disc which is driven by a motor. Three rubber sliders areattached
14、 to the disc by leaf springs. The sliders are pressed onthe test surface by the weight of the device through threerollers. Each slider is loaded to 11.8 N (2.65 lbf) by the leafsprings. The disc and the fly wheel are connected by a spring1This practice is under the jurisdiction of Committee E17 on V
15、ehicle-PavementSystems and is the direct responsibility of Subcommittee E17.21 on Field Methodsfor Measuring Tire Pavement Friction.Current edition approved Dec. 10, 2002. Published February 2003. Originallyapproved in 1998. Last previous edition approved in 1998 as E 191198.2Annual Book of ASTM Sta
16、ndards, Vol 04.03.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.balance mounted along a circle on which the rubber sliders arefixed. Due to the forces on the rubber sliders, displacementoccurs in a spring balance. This displacement
17、 is converted to anelectrical signal through a displacement transducer with anaccuracy of 6 1 % of full scale attached to the opposite side ofthe disc. This signal is output through a slip ring and brush,both of which are mounted on a driving shaft. The speed ofrubber sliders is measured from the ou
18、tput of a rotational speeddynamo.6.2 Water Supply (see Fig. 2)A water supply unit isprovided to maintain a wet condition of the test surface. Whenthe tank is 0.6 m above the tester a water flow of 3.6 l/min(0.95 gal/min) is maintained. If the flow is initiated when therotation corresponds to a tange
19、ntial velocity of 85 km/h (50mph) the water thickness will be 1 mm (0.04 in) by the timethat the velocity reaches 90 km/h (55 mph) and the measure-ment is initiated.6.3 Slider (see Fig. 3)The slider assembly shall consist ofa steel backing plate to which is bondeda6by16by20mm(0.25 by 0.63 by 0.79 in
20、.) rubber shaped as shown in Fig. 3.This shape provides a contact pressure of 150 kPa (21.5(lbf/in.2). The rubber compound shall be synthetic rubber asspecified in Specification E 501 and shall have a shore hard-ness of 58 6 2. The sliders shall be replaced due to waves aftertwelve runs. The slider
21、production date is given on the plasticbag in which they are shipped. The sliders must be used withintwelve months of the production date to avoid effects ofpassive deterioration.NOTE 1On extremely harsh surfaces it may be necessary to replacethe sliders more often.6.4 Data CollectionThe instantaneo
22、us value of the fric-tion is detected as a signal from the force transducer. Thevibration during measurement is absorbed by a damper. Thesignal is filtered by a first order R-C filter with a time constantof 0.1 s. The signal may be saved for future analysis.6.5 Data RecordingThe tester can be connec
23、ted to apersonal computer and the data can be displayed on the screenFIG. 1 The DF Testers (Dimensions in mm: 25.4 mm = 1 in.)E 1911 98 (2002)2and stored on floppy discs. As an alternative, the friction signaland the speed signal from the rotational speed dynamo can berecorded using an X-Y plotter t
24、o provide a paper record of therelation between friction and speed.7. Test Samples7.1 FieldField test surfaces shall be free of loose particlesand flushed with clean water. The test surface does not have tobe horizontal provided the instrument can be leveled inworking position.7.2 LaboratoryLaborato
25、ry test panels shall be clean andfree of loose particles and shall be held rigidly so as not to bemoved by the forces during measurement.7.2.1 Flat laboratory test panels shall have a test surface ofat least 600 by 600 mm (24 by 24 in) with no disturbance fromedge effects for a diameter of 500 mm (2
26、0 in).8. Procedure8.1 Place the DF Tester on the test sample that should belevel and free of any contamination.NOTE 2It is preferable to operate the DF Tester at a location where thesurface is flat. However, it was shown (1) that the effect is negligible fora deviation from flatness of up to 6 mm (0
27、.24 in) over a 0.5 m (20 in)specimen.8.2 Start the rotation of the disk. Verify that the fly wheeland disc with three rubber sliders rotates without contacting thetest surface, and start the water supply.8.3 When the rotating speed reaches a target speed, waterflow is closed and the driving device i
28、s lowered to the testsurface.FIG. 2 The Watering ApparatusE 1911 98 (2002)38.4 The measurement begins, the speed of the drivingdevice gradually decreases due to the friction between rubbersliders and the test surface, and finally stops.8.5 Record the test results or store the data for futureanalysis
29、.9. Report9.1 Report the following information:9.1.1 Date and time of day,9.1.2 Individual values of the friction DFT Numbers forspeeds of 20, 40, 60, and 80 km/h (12, 24, 36, and 48 mph),9.1.3 Temperature of the test surface,9.1.4 Type, age, condition, and location of test surface,9.1.5 Shore hardn
30、ess and production date of the rubbersliders,9.1.6 Plot of the friction-speed curve, and9.1.7 Type and date of the most recent calibration.10. Precision and Bias10.1 PrecisionThe standard deviation of eight measure-ments on the same test surface ranged from 0.044 at 30 km/hto 0.038 at 60 km/h.310.2
31、BiasThere is no basis for determination of the bias.NOTE 3Results from the International PIARC Experiment to Com-pare and Harmonize Texture and Skid Resistance Measurements4indi-cated a correlation with the Skid Numbers from Test Method E 274produced a correlation coefficient (R) of 0.86. The result
32、s also showedthat, when used with a measure of Mean Profile Depth, the InternationalFriction Index can be determined by the DF Tester within 6 0.027.11. Keywords11.1 friction; pavements; skid resistance3Saito, K., Horiguchi, T, Kasahara, A., Abe, H., and Henry, J.J., Development ofa Portable Tester
33、for Measuring Skid Resistance and its Speed Dependency onPavement Surfaces, Transportation Research Record 1536, Washington, DC 1996,pp. 45-51.4Wambold, J. C., Antle, C.E., Henry, J. J., and Rado, Z, International PIARCExperiment to Compare and Harmonize Texture and Skid Resistance Measure-ments, Fi
34、nal Report, Permanent International Association of Road Congresses(PIARC), Paris 1995.FIG. 3 The Rubber Slider (Dimensions in mm: 25.4 mm = 1 in.)E 1911 98 (2002)4ANNEX(Mandatory Information)A1. CALIBRATIONA1.1 Friction Force TransducerDisconnect the powercord to the driving motor. Set up the tester
35、 as shown in Fig.A1.1 with the solenoid at the top and the locking screw inplace. Apply a calibration mass of 3.6 kg (8 lb) to the springscale which is attached to a lug by a calibration wire. Thiscorresponds to a coefficient of friction of 1.0. Adjust the knobmarked -GAIN so that the portable compu
36、ter or the X-Yplotter reads 1.06 1 %. Lift the calibration mass and reapply itseveral times to verify that the friction remains at 1.0 6 1%.A1.2 Vertical ForceSet up the DF Tester on a smoothlevel surface as in the usual measurement condition as shownin Fig. A1.2 and Fig. A1.3. Mark the position of
37、the motor caserelative to the frame. Remove the screw from the bottom of thedamper. Insert two wooden boards 30 by 70 by 500 mm (1.2 by2.75 by 20 in) under the tester. Attach a pulley and thecalibration mass of 3.6 kg (8 lb) to the top of the tester asshown in Fig. A1.2 and Fig. A1.3. The mark on th
38、e motor caseshould line up with frame. If not, increase or decrease thespring tension using the adjusting screws as necessary such thatthe mark on the motor case lines up relative to the frame.NOTE A1.1For calibration in the field where it is impractical to use apulley/weight system a spring scale c
39、an be used (see Fig. A1.2). Ifadjustments were made in the field using the spring scale this fact shouldbe reported with the results.A1.3 Slider Tangential VelocityThe DF Tester is de-signed so that when the disk rotates at 1500 rpm the slidertangential velocity is 80 km/h (48 mph). Adjust the S.GAI
40、Nknob on the control unit such that the speed of 80 km/h (48mph) is recorded when the rotational speed is 1500 rpm.E 1911 98 (2002)5FIG. A1.1 Setup for Calibration of Friction ForceE 1911 98 (2002)6FIG. A1.2 Setup for Calibration of Vertical ForceE 1911 98 (2002)7ASTM International takes no position
41、 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.T
42、his standard is subject to revision at any time by the responsible technical committee and must be reviewed every five years andif not revised, either reapproved or withdrawn. Your comments are invited either for revision of this standard or for additional standardsand should be addressed to ASTM In
43、ternational Headquarters. Your comments will receive careful consideration at a meeting of theresponsible technical committee, which you may attend. If you feel that your comments have not received a fair hearing you shouldmake your views known to the ASTM Committee on Standards, at the address show
44、n below.This standard is copyrighted by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959,United States. Individual reprints (single or multiple copies) of this standard may be obtained by contacting ASTM at the aboveaddress or at 610-832-9585 (phone), 610-832-9555 (fax), or serviceastm.org (e-mail); or through the ASTM website(www.astm.org).FIG. A1.3 Alternate Setup for Calibration of Vertical ForceE 1911 98 (2002)8
