1、Designation: E 303 93 (Reapproved 2008)Standard Test Method forMeasuring Surface Frictional Properties Using the BritishPendulum Tester1This standard is issued under the fixed designation E 303; the number immediately following the designation indicates the year oforiginal adoption or, in the case o
2、f revision, the year of last revision. 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 procedure for measuringsurface frictional properties using the Bri
3、tish Pendulum SkidResistance Tester.2A method for calibration of the tester isincluded in the Annex.1.2 The British Pendulum Tester is a dynamic pendulumimpact-type tester used to measure the energy loss when arubber slider edge is propelled over a test surface. The tester issuited for laboratory as
4、 well as field tests on flat surfaces, andfor polish value measurements on curved laboratory specimensfrom accelerated polishing-wheel tests.1.3 The values measured, BPN = British Pendulum (Tester)Number for flat surfaces and polish values for acceleratedpolishing-wheel specimens, represent the fric
5、tional propertiesobtained with the apparatus and the procedures stated hereinand do not necessarily agree or correlate with other slipperinessmeasuring equipment.1.4 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the u
6、ser of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.1.5 The values stated in SI units are to be regarded as thestandard. The values given in parentheses are for informationonly.2. Referenced Documents2.1 A
7、STM Standards:2E 501 Specification for Rib Tire for Pavement Skid-Resistance Tests3. Summary of Test Method3.1 This test method consists of using a pendulum-typetester with a standard rubber slider to determine the frictionalproperties of a test surface.3.2 The test surface is cleaned and thoroughly
8、 wetted priorto testing.3.3 The pendulum slider is positioned to barely come incontact with the test surface prior to conducting the test. Thependulum is raised to a locked position, then released, thusallowing the slider to make contact with the test surface.3.4 A drag pointer indicates the British
9、 Pendulum (Tester)Number. The greater the friction between the slider and the testsurface, the more the swing is retarded, and the larger the BPNreading. Four swings of the pendulum are made for each testsurface.4. Significance and Use4.1 This test method provides a measure of a frictionalproperty,
10、microtexture, of surfaces, either in the field or in thelaboratory.4.2 This test method may be used to determine the relativeeffects of various polishing processes on materials or materialcombinations.4.3 The values measured in accordance with this method donot necessarily agree or directly correlat
11、e with those obtainedutilizing other methods of determining friction properties orskid resistance.NOTE 1BPN and polish values from similar types of surfaces will notbe numerically equal, primarily because of the differences in slide lengthand surface shape. Theoretical correction of the polish value
12、s to obtainnumerical equality, either by mathematical manipulation or by use ofspecial measuring scales is not recommended.5. Apparatus5.1 British Pendulum Tester (Fig. 1)The pendulum withslider and slider mount shall weigh 1500 6 30 g. The distanceof the center of gravity of the pendulum from the c
13、enter ofoscillation shall be 411 6 5 mm (16.2 6 0.2 in.). The testershall be capable of vertical adjustment to provide a slidercontact path of 125 6 1.6 mm (41516 +116 in.) for tests on flatsurfaces, and 76 to 78 mm (3 6116 in.) for tests onpolishing-wheel specimens. The spring and lever arrangement
14、shown in Fig. 2 shall give an average normal slider loadbetween the 76-mm (3-in.) wide slider and test surface of 25006 100 g as measured by the method prescribed in the annex.1This test method is under the jurisdiction of ASTM Committee E17 on Vehicle- Pavement Systems and is the direct responsibil
15、ity of Subcommittee E17.23 onSurface Characteristics Related to Tire Pavement Slip Resistance.Current edition approved June 1, 2008. Published July 2008. Originally approvedin 1961. Last previous edition approved in 2003 as E 303 93 (2003).2For referenced ASTM standards, visit the ASTM website, www.
16、astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.5.2 Sl
17、iderThe slider assembly shall consist of an alumi-num backing plate to which is bondeda6by25by76-mm (14by 1 by 3-in.) rubber strip for testing flat surfaces ora6by25by 32 mm (14 by1by114-in.) rubber strip for testing curvedpolishing-wheel specimens. The rubber compound shall benatural rubber meeting
18、 the requirements of the Road ResearchLaboratory3or synthetic rubber as specified in SpecificationE 501.5.2.1 New sliders shall be conditioned prior to use bymaking ten swings on No. 60 grade silicon carbide cloth4orequivalent under dry conditions. The swings shall be madewith a tester adjusted as i
19、n Section 7.5.2.2 Wear on the striking edge of the slider shall not exceed3.2 mm (18 in.) in the plane of the slider or 1.6 mm (116 in.)vertical to it, as illustrated in Fig. 3.5.3 Accessories:3Giles, C. G. Sabey, Barbara E., and Carden, K. W. F., “Development andPerformance of Portable Skid-Resista
20、nce Tester,” Road Research Technical PaperNo. 66, Road Research Laboratory, Dept. of Scientific and Industrial Research,England, 1964.Kummer, H. W. and Moore, D. F. “Concept and Use of the British PortableSkid-Resistance Tester,” Report No. 6, PDH-PSV Joint Road Friction Program,Dept. of Mechanical
21、Engineering, The Pennsylvania State University, State College,PA 16802, June 1963.4The sole source of supply of the apparatus known to the committee at this timeis available from 3 M Co., St. Paul, MN, under the trade name of Type BSafety-Walk. If you are aware of alternative suppliers, please provi
22、de this informa-tion to ASTM International Headquarters. Your comments will receive carefulconsideration at a meeting of the responsible technical committee,1which you mayattend.FIG. 1 British Pendulum TesterFIG. 2 Schematic Drawing of Pendulum Showing Spring andLever ArrangementE 303 93 (2008)25.3.
23、1 Contact path gage shall consist of a thin ruler suitablymarked for measuring contact path length between 124 and 127mm (478 and 5.0 in.) or between 75 and 78 mm (21516 and 3116in.) as required for the particular test.5.3.2 Miscellaneous equipment, such as water container,surface thermometer, and b
24、rush is recommended.6. Test Specimen6.1 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 using only the leveling screws and thependulum head will clear the s
25、urface.6.2 LaboratoryLaboratory test panels shall be clean andfree of loose particles and shall be held rigidly so as not to bemoved by the force of the pendulum.6.2.1 Flat laboratory test panels shall have a test surface ofat least 89 by 152 mm (312 by 6 in.).6.2.2 Accelerated laboratory polishing-
26、wheel specimens-shall have a test surface of at least 44 by 89 mm (134 by 312 in.)and shall be curved in the arc of a circle 406 mm (16 in.) indiameter.7. Preparation of Apparatus7.1 LevelingLevel the instrument accurately by turningleveling screws until the bubble is centered in the spirit level.7.
27、2 Zero Adjustment Raise pendulum mechanism by loos-ening locking knob (directly behind pendulum pivot) and turneither of pair of head movement knobs at center of tester toallow slider to swing free of test surface. Tighten locking knobfirmly. Place pendulum in release position and rotate the dragpoi
28、nter counter clockwise until it comes to rest against adjust-ment screw on pendulum arm. Release pendulum and notepointer reading. If reading is not zero, loosen locking ring androtate friction ring on bearing spindle slightly and lock again.Repeat test and adjust friction ring until the pendulum sw
29、ingcarries pointer to zero.7.3 Slide Length Adjustment:7.3.1 With pendulum hanging free, place spacer underadjusting screw of lifting handle. Lower pendulum so edge ofslider just touches surface. Lock pendulum head firmly, raiselifting handle, and remove spacer.7.3.2 Raise slider by lifting handle,
30、move pendulum to rightlower slider, and allow pendulum to move slowly to left untiledge of slider touches surface. Place gage beside slider andparallel to direction of swing to verify length of contact path.Raise slider, using lifting handle, and move pendulum to left,then slowly lower until slider
31、edge again comes to rest onsurface. If the length of the contact path is not between 124 and127 mm (478 and 5.0 in.) on flat test specimens or between 75and 78 mm (21516 and 3116 in.) on curved polishing-wheelspecimens, measured from trailing edge to trailing edge of therubber slide, adjust by raisi
32、ng or lowering instrument with thefront leveling screws. Readjust level of instrument if necessary.Place pendulum in release position and rotate the drag pointercounter-clockwise until it comes to rest against adjustmentscrew on pendulum arm.8. Procedure8.1 Apply sufficient water to cover the test a
33、rea thoroughly.Execute one swing, but do not record reading.NOTE 2Always catch the pendulum during the early portion of itsreturn swing. While returning the pendulum to its starting position, raisethe slider with its lifting handle to prevent contact between the slider andthe test surface. Prior to
34、each swing, the pointer should be returned untilit rests against the adjustment screw.8.2 Without delay, make four more swings, rewetting thetest area each time and record the results.NOTE 3Care should be taken that the slider remains parallel to the testsurface during the swings, and does not rotat
35、e so that one end rather thanthe entire striking edge makes the initial contact. Available data indicatethat tilting of the slider may cause erroneous BPN readings.Installation of a small flat spring will relieve the problem. The springcan be inserted into a slot in the spring clip and the assembly
36、secured bythe cotter pin as shown in Fig. 4.The free ends of the spring can rest onthe slider backing plate to restrain the slider from tilting.8.3 Recheck the slide contact length in accordance with 4.3.9. Report9.1 Report the following information:9.1.1 Individual values in BPN or polish value uni
37、ts,9.1.2 Temperature of the test surface,FIG. 3 Slider Assembly Illustrating the Maximum Wear onStriking EdgeFIG. 4 Spring Clip and Spring to Inhibit Slider RotationE 303 93 (2008)39.1.3 Type, age, condition, texture and location of testsurface,9.1.4 Type and source of aggregate for polish value tes
38、ts,and9.1.5 Type and age of the rubber slider.10. Precision and BiasNOTE 4The following material pertains only to the precision and biasof BPN units.10.1 Repeated tests show standard deviations as follows:British rubber sliders 1.0 BPN unitRubber sliders (conforming to Specification E 501) 1.2 BPN u
39、nitsIn both cases the upper quartile of variability is representedin prevailing test instruments.As there is no marked correlationbetween standard deviation and arithmetic mean of sets of testvalues, it appears that standard deviations are pertinent to thistest regardless of the average skid resista
40、nce being tested.10.2 The relationship, if any exists, of observed BPN unitsto some “true” value of skid resistance has not and probablycannot be studied. As a result, precision and bias of this test inrelation to a true skid resistance measure cannot be evaluated,and only repeatability is given for
41、 the method.10.3 Determine the testing error as follows:E 5 tsn21/2(1)where:E = testing error,t = normal curve of 1.96 or 2.0 rounded,s = standard deviation of individual test results (BPNunits), andn = number of tests.10.4 In order to ensure that the testing error stays within 1.0BPN unit at a 95 %
42、 confidence level (corresponding to anormal curve of 1.96 or 2.0 rounded), the following samplesizes are needed:British natural rubber sliders 4Synthetic rubber sliders (conforming to Specification E 501)5ANNEX(Mandatory Information)A1. CALIBRATIONA1.1 Weight of PendulumThe pendulum arm withmounted
43、rubber slider shall be disconnected from the instru-ment and weighed to the nearest 1 g.A1.2 Center of GravityThe center of gravity of thependulum with a mounted rubber slider shall be determined byplacing the pendulum assembly over a knife edge and experi-mentally locating the point of balance as s
44、hown in Fig. A1.1.The adapter nut shall be held at the far end of the arm by a lightpaper wedge. After the point of balance has been obtained, theposition of the balance weight shall be adjusted until the slidesof the pendulum foot are horizontal.A1.3 Distance of Center of Gravity from Center ofOsci
45、llationWith the pendulum reconnected to the tester andknurled bearing cap removed, distance shall be measured fromthe center of oscillation (center of bearing nut) to the point ofbalance (center of gravity). This distance shall be measureddirectly to the nearest 1 mm (0.04 in.).A1.4 Slider LoadThe p
46、endulum shall be clamped to aholder attached to the scale plate of the tester and the testerplaced and leveled on a tripod stand as shown in Fig. A1.2.Insert the spacer. Adjust the pan balance with a bearingassembly (see Note A1.1) on one pan and tare weights on theother pan so that the balance poin
47、ter is at center scale reading.The pendulum, with a slider, shall be lowered with the verticalheight knobs of the tester until the slider is approximately 0.25mm (0.01 in.) from the top surface of the bearing assembly.Lock vertical height knob and remove the spacer. This willcause an unbalance which
48、 shall be partially compensated byFIG. A1.1 Pendulum Assembly Showing Location of the Point of BalanceE 303 93 (2008)4adding weights to the opposite pan to bring the indicator towithin approximately 200 g of the center scale reading. Tocomplete the balance procedure, the pointer is returned to thece
49、nter scale reading, by adding water slowly into a graduatedcylinder. Empty the cylinder and repeat pouring. Record theaverage weight required to raise slider so that the balancepointer is at the center of scale (see Note A1.2). If the average,normal slider load between the 76-mm (3-in.) wide slider andthe pan balance is not within the requirements stated in 2.1.1adjust the spring tension nut illustrated in Fig. 2 and redeter-mine the slider load.NOTE A1.1The bearing assembly may be a “ladder” bearing with arigid, free-moving top plate or a similar
