1、Standard Method of Test for Frictional Properties of Paved Surfaces Using a Full-Scale Tire AASHTO Designation: T 242-181Technical Section: 5a, Pavement Measurement Release: Group 1 (April) ASTM Designation: E274/E274M-15 American Association of State Highway and Transportation Officials 444 North C
2、apitol Street N.W., Suite 249 Washington, D.C. 20001 TS-5a T 242-1 AASHTO Standard Method of Test for Frictional Properties of Paved Surfaces Using a Full-Scale Tire AASHTO Designation: T 242-181Technical Section: 5a, Pavement Measurement Release: Group 1 (April) ASTM Designation: E274/E274M-15 1. S
3、COPE 1.1. This method covers the measurement of the frictional properties of paved surfaces with a specified full-scale 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 c
4、onstant load and at a constant speed while its major plane is parallel to its direction of motion and perpendicular to the 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 directl
5、y with those obtained by other pavement friction measuring methods. The values are intended for use in comparing certain 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 value
6、s are insufficient to determine the distance required to stop a vehicle on either a wet or a dry pavement. They are also 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 value
7、s stated in SI units are to be regarded as the standard. 1.5. This standard may involve hazardous materials, operations, 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 e
8、stablish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. 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-
9、Purpose Pavement Frictional-Property Tests T 282, Calibrating a Wheel Force or Torque Transducer Using a Calibration Platform (User Level) 2.2. ASTM Standards: E178, Standard Practice for Dealing with Outlying Observations 2018 by the American Association of State Highway and Transportation Official
10、s. All rights reserved. Duplication is a violation of applicable law.TS-5a T 242-2 AASHTO E501, Standard Specification for Standard Rib Tire for Pavement Skid-Resistance Tests E1136, Standard Specification for P195/75R14 Radial Standard Reference Test Tire F457, Standard Test Method for Speed and Di
11、stance Calibration of 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
12、 transducer, instrumentation, 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 del
13、ivered ahead of the 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 su
14、itable instrumentation. 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
15、and multiplied by 100. 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
16、a suitable brake. The 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 e
17、ach test wheel and, 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
18、 rims do not have the 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 ASTM E1
19、136. 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 applied load from 900 N (200 lbf) to full
20、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. 2018 by the American Association of State Highway and Transportation Officials. All rights reserved. Duplication is a
21、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 operations. 4.5.2. Force-Measuring Tran
22、sducerThe 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 the applied load, nonlinearity less than 1
23、 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-degree angular rotation with respect to i
24、ts 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 loading less than 1 percent of the applied lo
25、ad. 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. Vehicle SpeedMeasuring TransducersTran
26、sducers 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 simultaneously recorded. Fifth-wheel syste
27、ms shall conform to ASTM F457. 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, data correction must be made for these ef
28、fects 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 smoothing filter recommended in Section
29、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 described in Reference 1 (see Section 13.1)
30、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 that can be connected before or after test s
31、equences. 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 degrees over a bandwidth of 0 to 20 Hz). Ve
32、hicle 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 pavement ahead of the test tire shall be suppl
33、ied by a nozzle conforming to the dimensions in Figure 1. The quantity of water applied at 65 km/h (40 mph) shall be 2018 by the American Association of State Highway and Transportation Officials. All rights reserved. Duplication is a violation of applicable law.TS-5a T 242-4 AASHTO 600 mL/min mm 10
34、 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 shall be directly proportional to the test s
35、peed. 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 of the vertical axis through the centerli
36、ne 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 shall be reasonably clean and have no chemi
37、cals such as wetting agents or detergents added. 2018 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 Notes: 1. Dimensions shown are for M 261 and M 286 Standard Tires. 2. All dimensions
38、 are in mm. 3. Surface C must be milled flat and perpendicular to pipe centerline. Figure 1Nozzle 2 Holes, 10.312 DiaHole thru, 14.681 DiaCounter Bore, 10.312 Deep31.242 0.127MarkTop4.77515.87528.575203.2006.3509.5256.350C Drill thru 19 Holes,18 Spaces 9.5253.175 Dia thru 18Holes, 17 Spaces 9.52549.
39、911 0.127219.075 NominalMaterialAluminumAll Decimals 0.051158.75012.70025.40015.875Material Stainless SteelAll Decimals 0.041203.200 0.050101.600180.97590.50082.550 REF76.200 193.67565.10048.2606.35038.100 NP T XSchedule 40100.330 REF3.175Typ.MarkTop17.7835.5650.80057.15025.40015.875159.5376.35041.2
40、75-C-A-B-CAAEnd PieceBodySurface C9.525-16 thru2 Holes0.500 2018 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 as all attachments t
41、o 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 water may freeze on th
42、e 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 vehicle to its norm
43、al 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 performed in accordanc
44、e with ASTM F457. 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 normal traffic speeds
45、 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 affect test results, an
46、d 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 temperature just bef
47、ore 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 test section with level
48、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 intervals not greate
49、r 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 Positioning of Test Vehicle
