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 2016 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/J2704_201709 SURFACE VEHICLE RECOMMENDED PRACTICE J2704 SEP2017 Issued 2005-01 Reaffirmed 2010-
5、09 Revised 2017-09 Superseding J2704 SEP2010 Tire Normal Force/Deflection and Gross Footprint Dimension Test RATIONALE The document was edited to remove time-sensitive statements regarding pending research related to the influence of wheel stiffness. 1. SCOPE This SAE Recommended Practice describes
6、a test method for determining the vertical force and deflection properties of a non-rolling tire and the associated contact patch length and width. The method applies to any tire so long as the equipment is properly scaled to conduct the measurements for the intended test tire. The data are suitable
7、 for use in determining parameters for road load models and for comparative evaluations of the measured properties in research and development. NOTE: Herein, road load models are models for predicting forces applied to the vehicle spindles during operation over irregular pavements. Within the contex
8、t of this Recommended Practice, forces applied to the pavement are not considered. 1.1 Procedures Two procedures are specified. The first procedure produces tire normal force/deflection data. The second procedure produces gross footprint, tire contact area, dimensions. Properly applied, the second p
9、rocedure can simultaneously produce both normal force/deflection data and gross footprint dimensions. 1.2 Test Machines This document is test machine neutral. It may be applied using any type of test machine capable of fulfilling the requirements stated in this document. The test machine must be cap
10、able of accommodating the tire sizes which are to be tested. SAE INTERNATIONAL J2704 SEP2017 Page 2 of 10 2. REFERENCES 2.1 Applicable Documents The following publications form a part of this specification to the extent specified herein. Unless otherwise indicated, the latest issue of SAE publicatio
11、ns shall apply. 2.1.1 SAE Publications Available from SAE International, 400 Commonwealth Drive, Warrendale, PA 15096-0001, Tel: 877-606-7323 (inside USA and Canada) or +1 724-776-4970 (outside USA), www.sae.org. SAE J2047 Tire Performance Technology SAE J2429 Free-Rolling Cornering Test for Truck a
12、nd Bus Tires SAE 770870 The Effect of Tire Break-in on Force and Moment Properties, K. D. Marshall, R. L. Phelps, M. G. Pottinger, and W. Pelz, 1977. SAE 810066 The Effect of Aging on Force and Moment Properties of Radial Tires, M. G. Pottinger and K. D. Marshall 2.1.2 ISO Publication Copies of thes
13、e documents are available online at http:/webstore.ansi.org/. ISO Standard 17025 General requirements for the competence of testing and calibration laboratories 2.1.3 OSHA Publication Available from U.S. Department of Labor/OSHA, 200 Constitution Avenue, Washington, DC 20210, Tel: 800-321-6742, www.
14、osha.gov/pls/publications/pubindex.list. OSHA Standard 1910.177 Servicing Multi-piece and Single Piece Rim WheelsAvailable in wall chart form as #TTMP-7/95. 3. DEFINITIONS The definitions that follow are of special meaning in this Recommended Practice and are either not contained in other Recommende
15、d Practices or are worded somewhat differently in this practice. 3.1 CONTACT PATCH This is the total area of the tire surface that touches the road surface. It is possible because of the large normal forces applied in the procedures specified in this Recommended Practice for the total area in contac
16、t to include parts of the tire surface that are normally considered to be parts of the sidewalls as well as portions of the tire surface normally considered to be part of the tread surface. Figure 1 is an example of an ink block contact area print. SAE INTERNATIONAL J2704 SEP2017 Page 3 of 10 Figure
17、 1 - Ink block contact area print 3.2 CONTACT PATCH DIMENSIONS For purposes of this practice a rectangle is imposed about the contact patch as illustrated in Figure 1. The rectangles sides touch the most forward, most rearward, leftmost and rightmost points composing the contact patch. The sides are
18、 parallel to the X and Y axes of the SAE Tire Axis System, which are shown in Figure 1. 3.2.1 CONTACT PATCH LENGTH, L Contact Patch Length is the distance from the rearward edge of the imposed rectangle (the edge with the most algebraically negative X coordinate) to its forward edge (the edge with t
19、he most algebraically positive X coordinate). 3.2.2 CONTACT PATCH WIDTH, W Contact Patch Width is the distance from the leftmost edge of the imposed rectangle (the edge with the most algebraically negative Y coordinate) to its rightmost edge (the edge with the most algebraically positive Y coordinat
20、e). 3.3 TEST A Test is execution of the procedure described in this Recommended Practice one time on one tire at a single set of test conditions. 3.4 TEST PROGRAM A Test Program is a designed experiment involving a set of the tests described in this practice1. 1 There are many experimental possibili
21、ties: repeated tests of the same tire, tests of the same tire under multiple test conditions, tests of tires with different specifications (design details), application of this test as part of a series of different tests, etc. SAE INTERNATIONAL J2704 SEP2017 Page 4 of 10 4. NOMENCLATURE Table 1 list
22、s the symbols used in this document. For further information on items not in Section 4 of this practice, please see SAE J2047. Table 1 - Symbols defined Symbol Defined Term Z Vertical Deflection FZ Normal Force L Contact Patch Length p Inflation Pressure Rl Loaded Radius Standard Deviation (Note Sub
23、scripts) W Contact Patch Width 5. LABORATORY QUALITY SYSTEM REQUIREMENT The laboratory performing either of the procedures specified in this Recommended Practice shall have a quality system either conforming to ISO 17025 or which can be shown to be functionally equivalent to ISO 17025. The elements
24、of such a system are assumed below and are not, therefore, specifically called out within this practice. 6. APPARATUS The required apparatus consists of a loading machine and test rims. 6.1 Loading Machine The loading machine consists of a tire loading and positioning system, a measuring system, a f
25、lat surface simulated roadway, and the space housing the machine, which shall be maintained at 22 C 2 C. 6.1.1 Loading and Positioning System The system shall maintain the tire with the tire/wheel plane within 0.05 of perpendicular to the simulated roadway during all loading. Loading shall produce n
26、ormal forces accurate to within 1.0% of the test machines full-scale normal force range. The machines full-scale normal force range shall allow imposition of loads equivalent to at least 400% of the client specified 100% load. The hub may be either fixed or free to rotate about the spin axis2. 6.1.2
27、 Measuring System Two coordinated measuring systems are required. 6.1.2.1 Load/Deflection Measuring System This system shall measure normal force to within 0.5% of the test machines full-scale normal force range and loaded radius to within 0.5 mm3. The system shall have a normal force range that all
28、ows measurement of forces equivalent to those existing at 400% of the client specified 100% load. 2 In a practical sense the hub of a properly aligned machine will not rotate during loading in this test so fixity is a moot point in this case. 3 Should the measuring system sense multiple forces and m
29、oments, the output shall be corrected for load cell interaction by a matrix method conceptually equivalent to that discussed in SAE J2429. SAE INTERNATIONAL J2704 SEP2017 Page 5 of 10 6.1.2.2 Contact Image Measuring System The system shall give an image of the portion of the tire in contact with the
30、 simulated roadway at the target normal force imposed by the loading and positioning system. Examples of satisfactory imaging systems include ink block printing, frustrated total internal reflection photography or video imaging4, matrix mat electronic pressure sensing system computer imaging, or suc
31、h other systems as are capable of imaging the static tire/simulated roadway contact. The system shall allow determination of contact patch length and width within 2.0 mm. 6.1.3 Simulated Roadway The simulated roadway shall be a smooth flat surface free of loose materials and deposits. The material o
32、f which the roadway is made is unimportant so long as the roadway satisfies the following criteria. 6.1.3.1 The roadway shall be large enough to fully support the entire tire footprint. 6.1.3.2 The roadway and its supporting structure shall be sufficiently rigid so as to not change appreciably in ei
33、ther transverse or longitudinal orientation or in curvature under the machines maximum applied normal force. 6.2 Test Rims Test rims shall meet the dimensional tolerances of original equipment rims supplied on new vehicles and match the rim profile for the applicable tire as specified by the appropr
34、iate tire and rim standards association, for example, the Tire and Rim Association, Inc. NOTE: Rim stiffness may have a discernable influence on the results. 7. CALIBRATION5 Calibrate all measuring system components in accordance with the mandates of the written plan required by the laboratory quali
35、ty system referenced in Section 5. Calibration must exercise all measuring system components over substantially their full range of application and must be performed not less than once each year. The reference standards and instruments used in measuring system calibration shall be traceable to the N
36、ational Institute of Standards and Technology or the appropriate national standards organization with currently valid calibration certificates on file in the testing laboratorys files when the systems calibration is performed. Gains, offsets, and other pertinent performance measures and comments on
37、system behavior during calibration shall be kept permanently on file within the testing laboratorys archives and be available to customers on request. 8. PREPARATION OF APPARATUS6 Preparation of the apparatus shall ensure that the test equipment meets its calibration at the outset of each test progr
38、am and that the contact visualization system is functioning correctly. The precise process control method used to verify readiness of the apparatus is likely to be unique to an individual test site, but must be specified in writing within the quality system of the laboratory. The results of process
39、control experiments shall be available to customers on request. 4 This is a process in which the tire surface resting on a plastic membrane presses on a thick glass plate illuminated from the edges such that total internal reflectance occurs where there is no tire pressure (contact). Where pressure
40、occurs, the total internal reflectance is modified proportionate to the applied pressure and a footprint image is produced. 5 If required, Section 7 of SAE J2429 provides an expanded discussion of the question of calibration in the case of a more complex, but conceptually parallel measuring system.
41、6 If required, Section 7 of J2429 provides example possibilities for a more complex, but related measuring system. SAE INTERNATIONAL J2704 SEP2017 Page 6 of 10 9. SELECTION AND PREPARATION OF TEST TIRES 9.1 Selecting the Tires for Good Comparability The purpose of the test must be carefully borne in
42、 mind when selecting test tires since tire properties depend on numerous factors besides the tire design and materials. It is especially important to properly account for storage history (SAE 810066) and previous work history (SAE 770870). Due to the many complex questions that the test defined in t
43、his document may be used to address, specific tire selection recommendations can only be made for the case in which different tires are to be compared for pure design or materials effects. In that case, all test tires should be of approximately the same age, have been stored under essentially identi
44、cal conditions, have experienced approximately the same exercise history, and have been sampled from production lots with similar statistical characteristics. 9.2 Inflation Pressure The inflation pressure will significantly affect the deflection of a tire under load. Therefore the appropriate test i
45、nflation pressure must be specified by the requester. Because tires typically operate at a temperature higher than that of the ambient air, operating inflation pressure is usually higher than cold inflation pressure. If the purpose of testing is to simulate the running state, then the inflation pres
46、sure used in the test must be equivalent to the on-road operating inflation pressure. 9.3 Tire Preparation Clean the tire surface of dirt, loose material, or other contaminants. Mount the test tire on the tire and rim standards organization specified rim7. For rim wheels used on large vehicles such
47、as trucks, tractors, buses, and off-road machines, mounting and demounting shall be done in accordance with the practices specified in (OSHA 1910.177). (OSHA 1910.177) does not apply to the servicing of rim wheels used on automobiles or on pickup trucks and vans utilizing automobile tires or truck t
48、ires designated “LT”. The rim used shall meet the specifications noted in 6.2. 9.4 Sample Size Typically, a single tire selected at random from among the group of tires in each specification is an adequate sample if the goal is parametric data for producing a tire model. However, should the desire b
49、e to determine differences between tire specifications at a stated level of accuracy it will be necessary to use statistically valid sample sizes and to employ appropriate statistical analyses of the results to define the differences among specifications. 10. TEST PROCEDURES 10.1 Prior to Performing Either Procedure The test tire and rim assembly with the tire properly inflated and prepared for testing shall b
