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4、A) Fax: 724-776-0790 Email: CustomerServicesae.org SAE WEB ADDRESS: http:/www.sae.orgSAE values your input. To provide feedback on this Technical Report, please visit http:/www.sae.org/technical/standards/J2505_201008SURFACEVEHICLERECOMMENDEDPRACTICEJ2505 AUG2010 Issued 2003-06Revised 2010-08 Supers
5、eding J2505 JUN2003 Measurement of Vehicle-Roadway Frictional Drag RATIONALEThis document has been revised with editorial changes suggested during a review by the Accident Investigation and reconstruction practices committee TABLE OF CONTENTS 1. SCOPE 22. REFERENCES 32.1 Applicable Publications . 32
6、.1.1 SAE Publications . 32.1.2 NIST Publication . 32.2 Related Publications . 32.2.1 SAE Publications . 32.2.2 ASTM Publications 32.2.3 NIST Publication . 42.2.4 Other Publications . 43. DEFINITIONS . 43.1 ABS . 43.2 Braking Distance, d . 43.3 Fifth Wheel 43.4 Frictional Drag . 43.5 Frictional Drag
7、Coefficient (Coefficient of Friction) . 43.6 Frictional Drag Factor, f 43.7 Full Brake Application . 43.8 Skid Mark Length 53.9 Test Weight . 53.10 Vehicle Reference Point . 54. TEST CONDITIONS . 54.1 Safety 54.2 Vehicle 54.3 Initial Speed 54.4 Roadway Environment 54.5 Testing Events 5SAE J2505 Revi
8、sed AUG2010 Page 2 of 115. MEASUREMENT OF VEHICLE-ROADWAY DRAG FACTOR BY BRAKING DISTANCE 65.1 Procedure 65.2 Data Preparation and Analysis . 66. MEASUREMENT OF VEHICLE-ROADWAY DRAG USING ACCELERATION MEASURING INSTRUMENTS 66.1 Instrumentation . 66.1.1 Identification 76.1.2 Mounting Location . 76.1.
9、3 Signal Conditioning and Data Recording 76.1.4 Calibration . 76.2 Procedures 76.3 Data Presentation . 76.3.1 Averaging Procedures 76.3.2 Integration Procedures 77. RECORD KEEPING, DATA ANALYSIS, AND REPORTING . 87.1 Record Keeping 87.1.1 Testing Environment . 87.1.2 Vehicle and Allied Equipment . 8
10、7.1.3 Measurement Method Equipment Identification, Settings, Calibrations, Accuracy and Precision . 87.2 Data Acquisition and Analysis . 87.3 Computation and Unit Conversion 97.4 Data Analysis 97.5 Documentation and Reporting 98. NOTES 108.1 Marginal Indicia . 10APPENDIX A VEHICLE-ROADWAY FRICTIONAL
11、 DRAG MEASUREMENT DATA SHEET 11FIGURE 1 DECELERATION TIME HISTORY ILLUSTRATING THE AVERAGE VALUE COMPUTEDOVER THE TIME INTERVAL FROM t1TO t2. 8FIGURE A1 VEHICLE-ROADWAY FRICTIONAL DRAG MEASUREMENT DATA SHEET 111. SCOPE This SAE Recommended Practice provides guidelines for procedures and practices us
12、ed to obtain and record measurements and to analyze and present results of frictional drag tests of a vehicle with its brakes fully applied at a given roadway location. It is for use at accident sites and test sites and is applicable to straight-line stopping of vehicles such as passenger cars, ligh
13、t trucks and vans under fully braked conditions including locked-wheel skids for vehicles with a conventional braking system and for vehicles with full or partial antilock braking systems (ABS). The average deceleration resulting from a given series of tests is intended to be representative of a fri
14、ctional drag factor for the conditions under which the test was conducted such as the type of vehicle, type and condition of tires, roadway material and roadway surface conditions. The frictional drag factor is intended to conform to use with the stopping distance formula (Fricke, 1990) as stated in
15、 Equation 1. Two methods are included: Stopping Distance Method (measurement of the distance required to bring a vehicle to a complete stop from a known initial speed) and Average Acceleration Measurement (using acceleration measuring devices and data analysis to determine the average drag factor).
16、The Recommended Practice applies to vehicles stopping in a fully braked condition. Values of roadway frictional drag obtained by other means do not necessarily agree or correlate (Lock, et al., 1982) with full vehicle testing and are not recommended.SAE J2505 Revised AUG2010 Page 3 of 112. REFERENCE
17、S 2.1 Applicable Publications The following publications form a part of this recommended practice to the extent specified herein. Unless otherwise specified, the latest version of SAE publications shall apply. 2.1.1 SAE Publications Available from SAE International, 400 Commonwealth Drive, Warrendal
18、e, PA 15096-0001, Tel: 877-606-7323 (inside USA and Canada) or 724-776-4970 (outside USA), www.sae.org.SAE J670 Vehicle Dynamics Terminology 2.1.2 NIST Publication Available from National Institute of Standards and Technology, 100 Bureau Drive, Stop 1070, Gaithersburg, MD 20899-1070, Tel: 301-975-64
19、78, www.nist.gov.Taylor, B. N., Guide for the Use of the International System of Units (SI), NIST SP 811, 1995 2.2 Related Publications The following publications are for information purposes only and are not a required part of this document. 2.2.1 SAE Publications Available from SAE International,
20、400 Commonwealth Drive, Warrendale, PA 15096-0001, Tel: 877-606-7323 (inside USA and Canada) or 724-776-4970 (outside USA), www.sae.org.SAE J2909 Light Vehicle Dry Stopping Distance SAE J299 SEP93 Stopping Distance Test Procedure TSB 003 Rules for SAE Use of SI (Metric) Units SAE Paper 940722 Uncert
21、ainty in Accident Reconstruction Calculations, Brach, R. M., 1994 SAE Paper 940918 Analysis of Accelerometer Data for Use in Skid-Stop Calculations, Robinson, E. L., 1994 2.2.2 ASTM Publications Available from ASTM International, 100 Barr Harbor Drive, P.O. Box C700, West Conshohocken, PA 19428-2959
22、, Tel: 610-832-9585, www.astm.org.ASTM E 274-93 Test Method for Skid Resistance of Paved Surfaces Using a Full-Scale Tire ASTM E 445/E 445M-88 Test Method for Stopping Distance on Paved Surfaces Using a Passenger Vehicle Equipped with Full-Scale Tires ASTM E 456-96 Standard Terminology for Relating
23、to Quality and Statistics ASTM E 503/E 503M-88 (1994) Test Methods for Measurement of Skid Resistance on Paved Surfaces Using a Passenger Vehicle Diagonal Braking System SAE J2505 Revised AUG2010 Page 4 of 11ASTM F 403-86 (Reapproved 1993) Test Method for Tires for Wet Traction in Straight-Ahead Bra
24、king, Using Highway VehiclesASTM F 811-95 Practice for Accelerometer Use in Vehicles for Tire Testing 2.2.3 NIST Publication Available from National Institute of Standards and Technology, 100 Bureau Drive, Stop 1070, Gaithersburg, MD 20899-1070, Tel: 301-975-6478, www.nist.gov.Taylor, B. N. and C. E
25、. Kuyatt, Guidelines for Evaluating and Expressing the Uncertainty of NIST Measurement Results, NIST Technical Note 1297, US Dept of Commerce, 1994 2.2.4 Other Publications Fricke, Lynn B., Traffic Accident Reconstruction, Vol 2, Traffic Accident Investigation Manual, Northwestern University Traffic
26、 Institute, 1990 Lock, J. R., D. L. Ivey, A. S. Jones, K. E. Barnes, O. J. Pendelton and T. Chira-Chavala, Pavement Condition Measurement for Safety Improvements, Vol 1, “Development of Procedures”, Final Report, Texas Transportation Institute, College Station, TX, 1982 3. DEFINITIONS The following
27、terms and acronyms are defined for use herein. 3.1 ABS Antilock Braking System 3.2 Braking Distance, dThe straight line distance on a flat surface taken to bring a vehicle to rest by rapid full application of the braking system. 3.3 Fifth Wheel An instrumented wheel device attached to a vehicle that
28、 provides kinematic data in the heading direction of the vehicle. 3.4 Frictional Drag The total retarding force on a moving vehicle between its tires and the roadway surface, exerted as a result of brake application.3.5 Frictional Drag Coefficient (Coefficient of Friction) The ratio of the frictiona
29、l drag force to the vehicles weight at a given speed, position or instant of time. 3.6 Frictional Drag Factor, fThe frictional drag coefficient averaged over a fully braked stop as calculated using the stopping-distance formula (see Equation 1). 3.7 Full Brake Application The production of sufficien
30、t brake pedal force to cause wheels with conventional brakes to lock and/or for continual operation of an ABS system. SAE J2505 Revised AUG2010 Page 5 of 113.8 Skid Mark Length The length of a visible tire mark on a roadway surface made under full brake application. 3.9 Test Weight Total weight of t
31、he test vehicle, including onboard equipment and occupants, at the time of the tests. 3.10 Vehicle Reference Point A point on the exterior of a vehicle whose position is to be noted and measured at various times and events during a test. 4. TEST CONDITIONS 4.1 Safety The manner of conducting all act
32、ivities covered by this recommended practice should ensure the safety of the test personnel, observers and the general public. All applicable professional practices and applicable governmental laws and regulations for conducting such tests are to be followed. 4.2 Vehicle The vehicle used in the test
33、s, including its features, equipment and condition, should be chosen as appropriate to the needs and intended use of the data. The braking system should be inspected prior to all tests and any unplanned or unintentional irregularities noted and corrected. If testing of any part of the vehicle under
34、abnormal conditions is specifically intended, such conditions should not be a hazard to participants or the general public. The operator should be familiar with the vehicle, its condition and operation.Vehicle descriptive and physical information should be recorded for each test as described in Sect
35、ion 7 and the example data sheet in Appendix A. 4.3 Initial Speed The initial speed(s) chosen for testing should be representative of the conditions for which the data are to be applied. For example, if used for accident reconstruction purposes, speeds should simulate those of the subject conditions
36、. 4.4 Roadway Environment The roadway test site location and conditions should be chosen as appropriate to the needs and intended use of the data. The use of roadways and other locations accessible to the general public should be properly controlled. Weather conditions, roadway surface conditions in
37、cluding temperature, roadway geometry and other existing environmental conditions should be recorded (see attached data form) and any abnormalities noted. A sufficiently long portion of the roadway should be available to reach the test speed and to allow for controlled, aborted and abnormal stopping
38、 distances.4.5 Testing Events Extraordinary events that occur during testing, such as a significant change in vehicle heading, temporary lifting of a wheel or wheels from the roadway, brake fade, nonuniform wheel locking, different skid mark lengths from wheel to wheel, etc., should be noted. When p
39、ossible, measurements of extraordinary events should be taken, such as a heading angle at rest different from the original value. The consideration of potential error sources is left to the judgement and experience of the investigator. SAE J2505 Revised AUG2010 Page 6 of 115. MEASUREMENT OF VEHICLE-
40、ROADWAY DRAG FACTOR BY BRAKING DISTANCE 5.1 Procedure The vehicle should be brought to the steady desired initial speed. The brakes then should be rapidly actuated and sustained with sufficient force to maintain wheel lock and/or ABS system operation until the vehicle comes to rest. Any factors that
41、 can cause significant deviations from a straight line path and constant heading angle should be avoided. The roadway location corresponding to a vehicle reference point is to be marked at the time of brake system application, such as with a chalk gun triggered by brake system actuation. The speed a
42、t the time of brake pedal application at the mark point should be measured and recorded using appropriate instruments such as a radar gun, fifth wheel (side wheel) device, etc. The position of the vehicle reference point at the time of wheel lock can be marked in addition to or as an alternative to
43、brake system application location if all wheels lock with reasonable simultaneity. The distance of travel, d, from the marked point to the vehicle reference position at rest is to be measured and recorded. Measurement devices have an associated inaccuracy (for example, a 1% error in measuring 1.6093
44、 km is 16.093 m 1 mile is 52.8 ft). Experimental techniques, especially the act of coordinating a human observation and action with an event (starting and stopping a stop watch to time an event, reading a speed at an event such as wheel lock, etc.) have associated inaccuracies. A description of each
45、 measurement device and each experimental technique and a quantitative evaluation of their associated accuracies, precisions and variations should be reported.5.2 Data Preparation and Analysis Each test run produces corresponding values of initial speed, v0, and distance to rest, d. Using consistent
46、 units, the frictional drag factor, f, is calculated with the formula fv022gd cos- tan=(Eq. 1) where:g is the acceleration of gravity and is a constant grade angle. For a level roadway = 0; for an up grade is positive and for a down grade is negative. Calculation of the frictional drag factor, f, by
47、 any method other than Equation 1 (such as when a vehicle is not brought to rest) should be documented. For grade angles less than about 0.17 rad (10 degrees, 17.6% grade), the root-mean-square uncertainty of the frictional drag coefficient computed by Equation 1 can be estimated using the formula f
48、2fv0-2v02 fd-2d22+=(Eq. 2) v0, d and are variations of the initial speed, distance, and roadway grade angle, respectively, corresponding to measurement devices and procedures. Note that when any of the denominators in the terms of Equation 2 is small compared to the variations, the uncertainty is la
49、rge. The results of an uncertainty analysis by Equation 2 or other established technique, should be part of any report of measurement results. 6. MEASUREMENT OF VEHICLE-ROADWAY DRAG USING ACCELERATION MEASURING INSTRUMENTS This methodology is to be employed to determine frictional drag factor with the use of an acceleration measurement system such as an on-board accelerometer
