1、Designation: E 303 93 (Reapproved 2003)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 (e) 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 Br
3、itish 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 a
4、s 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 fri
5、ctional 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
6、user 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
7、ASTM Standards:E 501 Specification for Standard Rib Tire for PavementSkid Resistance Tests23. 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 t
8、horoughly 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 th
9、e British 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 frictionalp
10、roperty, 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
11、 correlate 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 pol
12、ish values 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 f
13、rom the center 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 1256 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 arr
14、angementshown 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 onVehicle-Pavement Systems and is the direct respo
15、nsibility of Subcommittee E17.23on Surface Characteristics Related to Tire-Pavement Friction.Current edition approved Aug. 10, 2003. Published November 2003. Originallyapproved in 1961. Last previous edition approved in 1998 as E 303 93 (1998).2Annual Book of ASTM Standards, Vol 04.03.1Copyright AST
16、M International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.5.2 SliderThe 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.) r
17、ubber strip for testing curvedpolishing-wheel specimens. The rubber compound shall benatural rubber meeting 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 s
18、ilicon carbide cloth4orequivalent under dry conditions. The swings shall be madewith a tester adjusted as in 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:
19、5.3.1 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.3Giles, C. G. Sabey, Barbara E., and Carden, K. W. F., “Development andPerfor
20、mance of Portable Skid-Resistance 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 Frictio
21、n Program,Dept. of Mechanical Engineering, The Pennsylvania State University, State College,PA 16802, June 1963.4Material known to be suitable for this purpose is available from 3 M Co., St.Paul, MN, under the trade name of Type B Safety-Walk.FIG. 1 British Pendulum TesterFIG. 2 Schematic Drawing of
22、 Pendulum Showing Spring andLever ArrangementE 303 93 (2003)25.3.2 Miscellaneous equipment, such as water container,surface thermometer, and brush 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
23、tobe horizontal provided the instrument can be leveled inworking position using only the leveling screws and thependulum head will clear the surface.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 pendu
24、lum.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-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. Pre
25、paration of Apparatus7.1 LevelingLevel the instrument accurately by turningleveling screws until the bubble is centered in the spirit level.7.2 Zero Adjustment Raise pendulum mechanism by loos-ening locking knob (directly behind pendulum pivot) and turneither of pair of head movement knobs at center
26、 of tester toallow slider to swing free of test surface. Tighten locking knobfirmly. Place pendulum in release position and rotate the dragpointer counter clockwise until it comes to rest against adjust-ment screw on pendulum arm. Release pendulum and notepointer reading. If reading is not zero, loo
27、sen locking ring androtate friction ring on bearing spindle slightly and lock again.Repeat test and adjust friction ring until the pendulum swingcarries pointer to zero.7.3 Slide Length Adjustment:7.3.1 With pendulum hanging free, place spacer underadjusting screw of lifting handle. Lower pendulum s
28、o edge ofslider just touches surface. Lock pendulum head firmly, raiselifting handle, and remove spacer.7.3.2 Raise slider by lifting handle, move pendulum to rightlower slider, and allow pendulum to move slowly to left untiledge of slider touches surface. Place gage beside slider andparallel to dir
29、ection of swing to verify length of contact path.Raise slider, using lifting handle, and move pendulum to left,then slowly lower until slider 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 7
30、8 mm (21516 and 3116 in.) on curved polishing-wheelspecimens, measured from trailing edge to trailing edge of therubber slide, adjust by raising or lowering instrument with thefront leveling screws. Readjust level of instrument if necessary.Place pendulum in release position and rotate the drag poin
31、tercounter-clockwise until it comes to rest against adjustmentscrew on pendulum arm.8. Procedure8.1 Apply sufficient water to cover the test area thoroughly.Execute one swing, but do not record reading.NOTE 2Always catch the pendulum during the early portion of itsreturn swing. While returning the p
32、endulum to its starting position, raisethe slider with its lifting handle to prevent contact between the slider andthe test surface. Prior to 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 ti
33、me and record the results.NOTE 3Care should be taken that the slider remains parallel to the testsurface during the swings, and does not rotate so that one end rather thanthe entire striking edge makes the initial contact. Available data indicatethat tilting of the slider may cause erroneous BPN rea
34、dings.Installation of a small flat spring will relieve the problem. The springcan be inserted into a slot in the spring clip and the assembly 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 th
35、e 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 units,9.1.2 Temperature of the test surface,9.1.3 Type, age, condition, texture and location of testsurface,9.1.4 Type and source of aggregate for polish value t
36、ests,and9.1.5 Type and age of the rubber slider.FIG. 3 Slider Assembly Illustrating the Maximum Wear onStriking EdgeFIG. 4 Spring Clip and Spring to Inhibit Slider RotationE 303 93 (2003)310. Precision and BiasNOTE 4The following material pertains only to the precision and biasof BPN units.10.1 Repe
37、ated tests show standard deviations as follows:British rubber sliders 1.0 BPN unitRubber sliders (conforming to Specification E 501) 1.2 BPN unitsIn both cases the upper quartile of variability is representedin prevailing test instruments. As there is no marked correlationbetween standard deviation
38、and arithmetic mean of sets of testvalues, it appears that standard deviations are pertinent to thistest regardless of the average skid resistance 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
39、 a result, precision and bias of this test inrelation to a true skid resistance measure cannot be evaluated,and only repeatability is given for 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
40、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 % confidence level (corresponding to anormal curve of 1.96 or 2.0 rounded), the following samplesizes are needed:British natural rubber sliders 4Synthetic rub
41、ber sliders (conforming to Specification E 501) 5ANNEX(Mandatory Information)A1. CALIBRATIONA1.1 Weight of PendulumThe pendulum arm withmounted 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 mo
42、unted rubber slider shall be determined byplacing the pendulum assembly over a knife edge and experi-mentally locating the point of balance as shown 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 o
43、f the balance weight shall be adjusted until the slidesof the pendulum foot are horizontal.A1.3 Distance of Center of Gravity from Center ofOscillationWith the pendulum reconnected to the tester andknurled bearing cap removed, distance shall be measured fromthe center of oscillation (center of beari
44、ng 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 pendulum 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.Inser
45、t 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 pointer 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
46、.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 shall be partially compensated byadding weights to the opposite pan to bring the indicator towithin approximately 200 g of the center scale reading. Tocomp
47、lete the balance procedure, the pointer is returned to thecenter 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 avera
48、ge,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
49、 or a similar arrangement so that no horizontalloads are introduced while measuring the vertical slider load.FIG. A1.1 Pendulum Assembly Showing Location of the Point of BalanceE 303 93 (2003)4NOTE A1.2It may be necessary to move the pans of the balance upand down to “work” the spring in order to get smooth and consistentreadings. If the measurements of the slider load are still irregular after“working” the spring, remove the side and bottom panels of the pendulumfoot and inspect for cleanliness of the bearing surfaces and knife edgesillustrated in
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