1、Standard Method of Test for Frictional Properties of Paved Surfaces Using a Full-Scale Tire AASHTO Designation: T 242-96 (2013)1ASTM Designation: E 274/E 274M-11 American Association of State Highway and Transportation Officials 444 North Capitol Street N.W., Suite 249 Washington, D.C. 20001 TS-5a T
2、 242-1 AASHTO Standard Method of Test for Frictional Properties of Paved Surfaces Using a Full-Scale Tire AASHTO Designation: T 242-96 (2013)1ASTM Designation: E 274/E 274M-11 1. SCOPE 1.1. This method covers the measurement of the frictional properties of paved surfaces with a specified full-scale
3、automotive tire. 1.2. This method utilizes a measurement representing the steady-state friction force on a locked test wheel as it is dragged over a wetted-pavement surface under constant load and at a constant speed while its major plane is parallel to its direction of motion and perpendicular to t
4、he pavement. 1.3. The values measured represent the frictional properties obtained with the equipment and procedures stated herein and do not necessarily agree or correlate directly with those obtained by other pavement friction measuring methods. The values are intended for use in comparing certain
5、 frictional properties of a pavement relative to those of other pavements or for evaluating changes in these frictional properties of a pavement with the passage of time. The values are insufficient to determine the distance required to stop a vehicle on either a wet or a dry pavement. They are also
6、 insufficient for determining the speed at which control of a vehicle would be lost, because peak and side-force friction are also required for these determinations. 1.4. The values stated in SI units are to be regarded as the standard. 1.5. This standard may involve hazardous materials, operations,
7、 and equipment. This standard does not purport to address all of the safety concerns associated with its use. It is the responsibility of the user of this standard to consult and establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
8、 2. REFERENCED DOCUMENTS 2.1. AASHTO Standards: M 261, Rib-Tread Standard Tire for Special-Purpose Pavement Frictional-Property Tests M 286, Smooth-Tread Standard Tire for Special-Purpose Pavement Frictional-Property Tests T 282, Calibrating a Wheel Force or Torque Transducer Using a Calibration Pla
9、tform (User Level) 2.2. ASTM Standards: E 178, Standard Practice for Dealing With Outlying Observations E 501, Standard Specification for Standard Rib Tire for Pavement Skid-Resistance Tests E 1136, Standard Specification for P195/75R14 Radial Standard Reference Test Tire F 377, Standard Practice fo
10、r Calibration of Braking/Tractive Measuring Devices for Testing Tires 2014 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.TS-5a T 242-2 AASHTO F 457, Standard Test Method for Speed and Distance Calibration o
11、f Fifth Wheel Equipped With Either Analog or Digital Instrumentation 3. SUMMARY OF METHOD 3.1. The test apparatus consists of an automotive vehicle with one or more test wheels incorporated into it or forming part of a suitable trailer towed by a vehicle. The apparatus contains a transducer, instrum
12、entation, a water supply and proper dispensing system, and actuation controls for the brake of the test wheel. The test wheel is equipped with a standard pavement test tire, as specified in M 261 or M 286. 3.2. The test apparatus is brought to the desired test speed. Water is delivered ahead of the
13、test tire and the braking system is actuated to lock the test tire. The resulting friction force acting between the test tire and the pavement surface (or some other quantity that is directly related to this force) and the speed of the test vehicle are recorded with the aid of suitable instrumentati
14、on. 3.3. Frictional properties of the paved surface are determined from the resulting force or torque recorded and reported as friction numbers (FN), which are determined from the force required to slide the locked test tire at a stated speed, divided by the effective wheel load and multiplied by 10
15、0. 4. APPARATUS 4.1. VehicleThe vehicle with one test tire locked shall be capable of maintaining test speeds of 65 to 100 km/h (40 to 60 mph) within 1.5 km/h (1.0 mph) during a test on a level pavement having an FN of 50. 4.2. Braking SystemThe test wheel shall be equipped with a suitable brake. Th
16、e brake system shall be capable of locking the wheel at the condition specified in Section 4.1 and maintaining the locked-wheel condition throughout the test. 4.3. Wheel LoadThe apparatus shall be of such a design as to provide an equal static load of 4800 65 N (1085 15 lbf) to each test wheel and,
17、on detachable trailers, a static download of 450 to 900 N (100 to 200 lbf) at the hitch point. 4.4. Tire and RimThe test tire shall be one of the standard tires for the pavement test, as specified in M 261 or M 286, and it shall be mounted on a suitable 15-by-6-in. rim. Since all rims do not have th
18、e same offset from the hub, replacement rims must be of the same offset to ensure consistent alignment of the tire with the water path. The data from the two tires are not interchangeable. Alternative testing for special purposes may be performed with other tires, such as a standard rib tire for pav
19、ement skid resistance of M 261 or ASTM E 501. 4.5. Instrumentation: 4.5.1. General Requirements for Measuring SystemThe instrumentation system shall conform to the following overall requirements at ambient temperatures between 4 and 40C (40 and 100F): 4.5.1.1. Overall System Accuracy11/2percent of a
20、pplied load from 900 N (200 lbf) to full scale; for example, at 900 N (200 lbf), applied calibration force of the system output shall be determinable within 14 N (3 lbf). 4.5.1.2. Time Stability of Calibration10-h minimum. 2014 by the American Association of State Highway and Transportation Official
21、s.All rights reserved. Duplication is a violation of applicable law.TS-5a T 242-3 AASHTO 4.5.1.3. The exposed portions of the system shall tolerate 100 percent relative humidity (rain or spray) and all other adverse conditions, such as dust, shock, and vibrations, which may be encountered in highway
22、 operations. 4.5.2. Force-Measuring TransducerThe tire forcemeasuring transducer shall be of such design as to measure the tireroad interface force with minimum inertial effects. Transducers are recommended to provide an output directly proportional to force with hysteresis less than 1 percent of th
23、e applied load, nonlinearity less than 1 percent of the applied load up to the maximum expected loading, and sensitivity to any expected cross-axis loading or torque loading less than 1 percent of the applied load. The force transducer shall be mounted in such a manner as to experience less than 1-d
24、egree angular rotation with respect to its measuring plane at the maximum expected loading. 4.5.3. Torque-Measuring TransducerTorque transducers provide an output directly proportional to torque with hysteresis less than 1 percent of the applied load and nonlinearity up to the maximum expected loadi
25、ng less than 1 percent of the applied load. It should have sensitivity to any cross-axis loading less than 1 percent of the applied load. 4.5.4. Additional TransducersForce transducers for measuring quantities such as vertical load, etc., shall meet the recommendations stated in Section 4.5.2. 4.5.5
26、. Vehicle SpeedMeasuring TransducersTransducers such as fifth-wheel or free-rolling wheel-coupled tachometers shall provide speed resolution and accuracy of 1.5 percent of the indicated speed or 1.0 km/h (0.5 mph), whichever is greater. Output shall be directly viewable by the driver and shall be si
27、multaneously recorded. Fifth-wheel systems shall conform to ASTM F 457. 4.6. Signal Conditioning and Recorder System: 4.6.1. Transducers that measure parameters sensitive to inertial loading shall be designed or located in such a manner as to minimize this effect. If the foregoing is not practical,
28、data correction must be made for these effects if they exceed 2 percent of the actual data during expected operation. All signal conditioning and recording equipment shall provide linear output and shall allow data reading resolution to meet the requirements of Section 4.5.1. All systems, except the
29、 smoothing filter recommended in Section 4.6.2, shall provide a minimum bandwidth of at least 0 to 20 Hz (flat within 1 percent). 4.6.2. It is recommended that an electronic filter, typically between 4.8 Hz/3dB/4-pole Bessel-type and a 10 Hz/3dB/8-pole Butterworth filter, selected from the types des
30、cribed in Reference 1 (see Section 13.1) be installed in the signal conditioning circuit preceding the electronic divider and integration calculation of FN as described in Section 9.4. 4.6.3. All strain-gauge transducers shall be equipped with resistance shunt calibration resistors or equivalent tha
31、t can be connected before or after test sequences. The calibration signal shall be at least 50 percent of the normal vertical load and shall be recorded. 4.6.4. Tire friction force or torque and any additional desired inputs, such as vertical load, wheel speed, etc., shall be recorded in phase (5 de
32、grees over a bandwidth of 0 to 20 Hz). Vehicle speed shall also be recorded. All signals shall be referenced to a common time base. 4.6.5. A signal-to-electrical noise ratio of at least 20 to 1 is desirable on all recorded channels. 4.7. Pavement Wetting System: 4.7.1. The water applied to the pavem
33、ent ahead of the test tire shall be supplied by a nozzle conforming to the dimensions in Figure 1. The quantity of water applied at 65 km/h (40 mph) shall be 2014 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable l
34、aw.TS-5a T 242-4 AASHTO 600 mL/min mm 10 percent (4.0 gal/min in. 10 percent) of wetted width. The water layer shall be at least 25 mm (1 in.) wider than the test tire tread and applied so the tire is centrally located between the edges. The volume of water per millimeter (inch) of wetted width shal
35、l be directly proportional to the test speed. 4.7.2. The nozzle configuration and position shall ensure that the water jets shall be directed toward the test tire and pointed toward the pavement at an angle of 20 to 30 degrees. The water shall strike the pavement 250 to 450 mm (10 to 18 in.) ahead o
36、f the vertical axis through the centerline of the test wheel. The nozzle shall be 25 mm (1 in.) above the pavement or the minimum height required to clear obstacles that the tester is expected to encounter, but in no case more than 100 mm (4 in.) above the pavement. 4.7.3. Water used for testing sha
37、ll be reasonably clean and have no chemicals such as wetting agents or detergents added. 2014 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.TS-5a T 242-5 AASHTO 2 Holes, 10.319 DiaHole thru, 14.684 DiaCount
38、er Bore, 10.319 Deep31.242 0.127MarkTop4.77515.87529.264203.2006.7319.5256.350C Drill thru 19 Holes,18 Spaces 9.5253.175 Dia thru 18Holes, 17 Spaces 9.52549.911 0.187221 NominalMaterialAluminumAll Decimals 0.050158.75012.70025.40015.875Material Stainless SteelAll Decimals 0.400203.200 0.050101.60018
39、0.97590.48882.550 REF 76.200 25461.97648.2606.35038.100 NP T XSchedule 40100.330 REF3.175Typ.MarkTop17.7835.5650.80057.15025.40015.875159.5376.35041.504-C-A-B-250C012012125A125AEnd PieceBodySurface CNotes: 1. Dimensions shown are for M 261 and M 286 Standard Tires. 2. All dimensions are in mm. 3. Su
40、rface C must be milled flat and perpendicular to pipe centerline. Figure 1Nozzle 2014 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.TS-5a T 242-6 AASHTO 5. SAFETY PRECAUTIONS 5.1. The test vehicle, as well
41、as all attachments to it, shall comply with all applicable state and federal laws. All necessary precautions shall be taken beyond those imposed by laws and regulations to ensure maximum safety of operating personnel and other traffic. No test shall be made when there is danger that the dispersed wa
42、ter may freeze on the pavement. 6. CALIBRATION 6.1. SpeedCalibrate the test vehicle speed indicator at the test speed by determining the time for traversing at constant speed a reasonably level and straight, accurately measured pavement of a length appropriate for the method of timing. Load the test
43、 vehicle to its normal operating mass for this calibration. Record speed variations during a traverse with the friction test system. Make a minimum of three runs at each test speed to complete the calibration. Other methods of equivalent accuracy may be used. Calibration of a fifth wheel shall be pe
44、rformed in accordance with ASTM F 457. 6.2. Frictional ForceCalibrate the frictional force in the manner described in T 282. 7. GENERAL 7.1. Test PreparationCondition new tires by running them at or near their rated load and inflation pressure on the test vehicle (or on another suitable vehicle) at
45、normal traffic speeds for at least 300 km (200 miles) or equivalent before they are used for test purposes. Prior to each series of tests, warm up the tire by traveling for at least 10 km (5 miles) at normal traffic speeds. Inspect the tire for flat spots, damage, or other irregularities that may af
46、fect test results, and replace if it has been damaged or is worn beyond the wear line. Check the test-wheel load (if adjustable) and adjust, if necessary, prior to each test series to within the value specified in Section 4.3. Set the test tire inflation pressure at 165 3 kPa (24 0.5 psi) at ambient
47、 temperature just before the 10-km (5-mile) warm-up. 7.2. Test SectionsTest sections shall be defined as sections of pavement of uniform age and uniform composition that have been subjected to essentially uniform wear. For instance, sharp curves and steep grades shall not be included in the same tes
48、t section with level tangent sections, nor shall passing lanes be included with traffic lanes. Take frictional property measurements only on pavements that are free of obvious contamination. 7.3. Frictional Properties of a Test SectionMake at least five determinations of the frictional properties at
49、 intervals not greater than 1 km (0.5 mile), in each test section with the test vehicle at the same lateral position in any one lane and at each specified test speed. Consider the arithmetic average of all determinations to be the frictional properties of the test section. If statistical or other criteria applied to the FN for a long test section, indicate that it cannot be considered as uniform, treat the section as two or more sections. For treatment of the results of faulty tests, see Section 10. 7.4. Lateral
