1、_ SAE Technical Standards Board Rules provide that: “This report is published by SAE to advance the state of technical and engineering sciences. The use of this report is entirely voluntary, and its applicability and suitability for any particular use, including any patent infringement arising there
2、from, is the sole responsibility of the user.” SAE reviews each technical report at least every five years at which time it may be revised, reaffirmed, stabilized, or cancelled. SAE invites your written comments and suggestions. Copyright 2017 SAE International All rights reserved. No part of this p
3、ublication may be reproduced, stored in a retrieval system or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without the prior written permission of SAE. TO PLACE A DOCUMENT ORDER: Tel: 877-606-7323 (inside USA and Canada) Tel: +1 724-776-497
4、0 (outside USA) Fax: 724-776-0790 Email: CustomerServicesae.org SAE WEB ADDRESS: http:/www.sae.org SAE values your input. To provide feedback on this Technical Report, please visit http:/standards.sae.org/J2452_201707 SURFACE VEHICLE RECOMMENDED PRACTICE J2452 JUL2017 Issued 1999-06 Revised 2017-07
5、Superseding J2452 JUN1999 Stepwise Coastdown Methodology for Measuring Tire Rolling Resistance RATIONALE The revisions in this version are to address missing SI units a typo in section 3.10 and to clarify issues associated with zero speed points in the MERF/SMERF calculations. FOREWORD This SAE Reco
6、mmended Practice establishes a laboratory method for determination of tire rolling resistance of Passenger Car and Light Truck tires. The method provides a standard for collection and analysis of rolling resistance data with respect to vertical load, inflation pressure, and velocity. The primary int
7、ent is for estimation of the tire rolling resistance contribution to vehicle force applicable to SAE Vehicle Coastdown recommended practices SAE J2263 and SAE J2264. 1. SCOPE This SAE Recommended Practice is applicable to pneumatic Passenger Car “P” Type, Light Truck Metric, and Light Truck High Flo
8、tation tires, or similar tires approved by bodies other than Tire 17-20-1995 by S. H. Bordelon and S. M. Padula. “An Analytical Model for Transient Rolling Resistance Behavior of Tires,” Mars, Will V.; Luchini, John R.; Journal of Tire Science and Technology, v27#4, 1999. 3. DEFINITIONS 3.1 ROLLING
9、RESISTANCE Rolling resistance is the energy consumed per unit distance and is equivalent to the scalar sum of all contact forces tangent to the test surface and parallel to the wheel plane of the tire. Units are Newtons (lbf). 3.2 ROLLING RESISTANCE COEFFICIENT Rolling resistance coefficient is the
10、ratio of the rolling resistance to the tire load. Units are Newtons per 1000 N of applied load. (Pounds per 1000 lbs of applied load or kg/ton (1000 kg) 3.3 LOADED RADIUS Loaded radius is the perpendicular distance from the axis of rotation of the loaded tire to the surface on which it is rolling. U
11、nits are mm (in). 3.4 MAXIMUM LOAD Maximum load is molded in the sidewall and is listed as load limit in the tire load tables of the current Tire therefore, at these zero speed points, the rolling resistance force shall be set equal to zero for the MERF/SMERF calculations. For further details regard
12、ing the theory and use of MERF/SMERF, the reader is referred to the reference listed in 2.1.2.1. 9.7 Converting Data Measured on Different Surface Size Rolling resistance data generated on a test surface of given diameter may be converted to rolling resistance on a test surface of different diameter
13、 or even a flat surface by means of Equation 21: 112212RRrRrRR/RRR(Eq. 21) SAE INTERNATIONAL J2452 JUL2017 Page 23 of 39 where: RR1 = rolling resistance on surface with radius R1 meters N (lbf) RR2 = rolling resistance on surface with radius R2 meters N (lbf) r = unloaded nominal tire radius meters
14、(in) If this expression is used to convert rolling resistance measured on a surface, of known radius R1, to that on a flat surface (R2 ), it reduces to: (see Equation 22) 1112RRrRRRR(Eq. 22) NOTE: These expressions are not yet proven for universal application. Their inclusion does not constitute an
15、endorsement of their validity, but merely signifies that this represents current state-of-the-art knowledge. See SAE J1270 for further comments. 10. PRECISION AND BIAS A reproducibility experiment was conducted at several laboratories to provide data to evaluate this test methodology. Since there is
16、 no absolute standard, or calibration standard, for the experimentally measured value of rolling resistance, the experiment was used to provide average values for comparison across laboratories. Table 4 details the results of the study as described in the following paragraphs. TABLE 4 - GAGE R AND R
17、 RESULTS SUMMARY Tire Summary Repeatability Pooled Repeatability Pooled Reproducibility Mean Gauge R and R Pooled Bias (RMS) Pooled P215/70R15 0.2 N 0.1 0.4 N 0.8 N 0.8 N 0.5 N P205/60R15 0.3 N 0.2 0.3 N 0.6 N 0.7 N 0.6 N LT235/85R16 (LR E) 0.7 N 0.3 0.7 N 1.2 N 1.4 N 1.2 N All tire composite 0.5 N
18、0.9 N 1.0 N 0.8 N 10.1 Repeatability The repeatability of this method is its capacity to duplicate the results of previous experiments without bias, within the equipment limits of Section 6. A pooled standard deviation within each laboratory was used to estimate the repeatability of this methodology
19、. 10.2 Reproducibility The reproducibility of this method is its capacity to use another experimental set up (different equipment, location, or operator) and obtain duplicate results without bias, within the equipment limits of Section 6. A pooled standard deviation between laboratories was used to
20、estimate the reproducibility of this methodology. 10.3 Gauge R & R The gauge for overall test repeatability and reproducibility is the total pooled standard deviation, which includes the effects of both within laboratory and between laboratory variations. SAE INTERNATIONAL J2452 JUL2017 Page 24 of 3
21、9 10.4 Bias Bias from a reference value provides a measure of test accuracy, in an inverse fashion, when there is no absolute standard. (A small bias implies good accuracy.) When bias exists, increased sample size and statistical analysis does not increase accuracy, but merely gives an increased con
22、fidence in the bias estimate. The reference measurement for the reproducibility and repeatability experiment from which the bias error was calculated was the average of the predictions from each laboratory under specific conditions. The predicted values at 8 combinations of load, inflation pressure,
23、 and speed were used in computing the bias estimate. The geometric mean, the square root of the mean of the squares (RMS), was used to compute the bias for each tire. 11. NOTES 11.1 Marginal Indicia A change bar (I) located in the left margin is for the convenience of the user in locating areas wher
24、e technical revisions, not editorial changes, have been made to the previous issue of this document. An (R) symbol to the left of the document title indicates a complete revision of the document, including technical revisions. Change bars and (R) are not used in original publications, nor in documen
25、ts that contain editorial changes only. PREPARED BY THE SAE HIGHWAY TIRE FORUM STEERING COMMITTEE SAE INTERNATIONAL J2452 JUL2017 Page 25 of 39 APPENDIX A - VERIFICATION OF METHODOLOGY USED FOR THIS RECOMMENDED PRACTICE A.1 This methodology was developed and verified using the following parameters:
26、a. Road Surface: 1.7 m diameter steel surface b. Road Surface: Medium grit (80 grit) c. Speed Range: 115 to 15 km/h (71 to 9 mph) d. Time: 180 s from 115 to 15 km/h (71 to 9 mph) e. Load/Inflation: Tables A1 and A2 f. Slip Angle: 0 degrees g. Camber Angle: 0 degrees h. Test Temperature: 24 C 4 C (75
27、 F 7 F) Test results should be valid within the limits stated in the scope of this methodology. Validity of results for any use outside of these guidelines cannot be verified. TABLE A1 - PASSENGER CAR VERIFICATION TEST MATRIX Inflation Pressure (Base ) % Load(1)30 % Load(1)45 % Load(1)60 % Load(1)75
28、 % Load(1)90 40 x x x 15 x x+10 x x x 35 x x +60 x x X 1. Percent of T&RA 240 kPa load. TABLE A2 - LIGHT TRUCK VERIFICATION TEST MATRIX Inflation Pressure (% of Max) % Load(1)20 % Load(1)40 % Load(1)55 % Load(1)70 % Load(1)85 % Load(1)100 40 x x x 60 x x 80 x x x 100 x x x 110 x x x NOTE: Shaded cel
29、ls represent conditions outside legal operating envelope 1. Percent of T&RA Max Load. SAE INTERNATIONAL J2452 JUL2017 Page 26 of 39 APPENDIX B - SURFACE CONDITIONING PROCEDURE B.1 After applying a new surface to the test surface, run a wide tread tire on the test surface at max load to remove any ai
30、r pockets that may exist beneath the surface. This tire should be wide enough to encompass the largest contact width of any tire which may be tested. Conditioning of the surface may be required to stabilize its effect on rolling resistance and minimize wear. This can be accomplished via the followin
31、g steps: a. With the test surface moving at 5 km/h or less, hold a conditioning stone against the test surface with moderate pressure for 4 revolutions of the surface. b. Move the conditioning stone to the next lateral position on the surface and repeat Step a until the entire test surface area has
32、been completed. c. Run a wide tread tire, similar to that described previously, for a period of 30 min under Standard Reference conditions at 80 km/h. d. Stop the tire and check for noticeable tread wear. Repeat steps a through c until no noticeable tread rubber is removed. e. Run a control tire wit
33、h an established and stable rolling resistance level to ensure that results are consistent with previous surfaces. If no prior data is available, make consecutive runs of the control tire to verify that the surface effect on rolling resistance has stabilized. SAE INTERNATIONAL J2452 JUL2017 Page 27
34、of 39 APPENDIX C - DETAILS OF THE PRECISION AND BIAS STUDY C.1 OBJECTIVE Establish operating repeatability and reproducibility associated with coastdown RR test procedure as performed at various test labs on 67 in surface machines. C.2 TEST METHOD a. Each of three labs performed testing according to
35、 test schedule in Table C1. TABLE C1 - TEST SEQUENCE Lab 4 05/04/98 Lab 2 04/29/98 Lab 3 05/08/98 Lab 4 05/22/98 Lab 2 06/01/98 Tire A: P215/70R15 xxx xxx xxx Tire B: P205/60R15 xxx xxx xxx Tire C: LT235/85R16 xxx xxx xxx NOTE: xxx denotes three repeat tests of tires b. Stepwise coastdown tests were
36、 run as defined in this document. Coastdown speed range was from 115 to 15 km/h (71 to 9 mph). Test conditions detailed in Table C2. TABLE C2 - TEST CONDITIONS Step Load (N) Load (lb) Inflation kPa) Inflation (psi) Warm Up (min) TIRE A 1 2162 486 250 36.3 30 2 (SKIM) 89 20 250 36.3 10 3 4323 972 200
37、 29.0 10 4 6485 1458 300 43.5 10 5 6485 1458 200 29.0 10 TIRE B 1 1765 390 250 36.3 30 2 (SKIM) 89 20 250 36.3 10 3 3474 781 200 29.0 10 4 5209 1171 300 43.5 10 5 5209 1171 200 29.0 10 TIRE C 1 2704 608 607 88.0 60 2 (SKIM) 156 35 552 80.0 15 3 5413 1217 276 40.0 15 4 5413 1217 552 80.0 15 5 9470 21
38、29 331 48.0 15 6 13531 3042 552 80.0 15 SAE INTERNATIONAL J2452 JUL2017 Page 28 of 39 c. Following a test, the tire was placed at ambient test room temperature 24 C 4 C (75 F 7 F) for 6 h to permit tire to reach thermal equilibrium d. RR data was reported as temperature corrected Net RR. 3. e. Force
39、 type data included average of FWD and REV directions. Time was representative of time in FWD direction only. C.3 TEST TIRES/SCHEDULE a. Refer to Table C3 for list of tires run. TABLE C3 - TEST TIRES Tire A Tire B Tire CSize P215/70R15 P205/60R15 LT235/85R16 E Speed Rating S H Rim 6.5 in 6.0 in 6.5
40、in b. Each lab provided a previously-stabilized test tire. c. Each lab tested each tire three times with a cool down time between runs per Table C1. C.4 DATA ANALYSIS a. Test repeatability (variation within lab) was determined by comparing variation between specific data points (at specific speeds)
41、between three runs on same machine. b. With machines measuring at different speeds, test reproducibility (variation between labs) was determined by regressing all data for each test and comparing single data points along the best-fit curves for specific velocities at specification loads and pressure
42、s. SAE INTERNATIONAL J2452 JUL2017 Page 29 of 39 APPENDIX D - EPA SCHEDULE DEFINITIONS (TIME VERSUS VELOCITY) D.1 EPA URBAN CYCLE (CCVS) Time (seconds) versus Velocity (km/h) Profile FIGURE D1A - EPA URBAN CYCLE (CCVS) SAE INTERNATIONAL J2452 JUL2017 Page 30 of 39 FIGURE D1B - EPA URBAN CYCLE (CCVS) (CONTINUED)
