1、 SURFACE VEHICLE RECOMMENDED PRACTICE Tire Normal Force/Deflection and Gross Footprint Dimension Test 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 a
2、pplicability and suitability for any particular use, including any patent infringement arising therefrom, is the sole responsibility of the user.” SAE reviews each technical report at least every five years at which time it may be reaffirmed, revised, or cancelled. SAE invites your written comments
3、and suggestions. Copyright 2005 SAE International All rights reserved. No part of this publication 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.
4、TO PLACE A DOCUMENT ORDER: Tel: 877-606-7323 (inside USA and Canada) Tel: 724-776-4970 (outside USA) Fax: 724-776-0790 Email: custsvcsae.org SAE WEB ADDRESS: http:/www.sae.org Issued 2005-01 J2704 ISSUED JAN2005 1. Scope This SAE Recommended Practice describes a test method for determining the verti
5、cal 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 for use in determining parameters for
6、road load models and for comparative evaluations of the measured properties in research and development. NOTEHerein, road load models are models for predicting forces applied to the vehicle spindles during operation over irregular pavements. Within the context of this Recommended Practice, forces ap
7、plied 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 procedure can simultaneously produce both
8、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 capable of accommodating the tire sizes whic
9、h are to be tested. 1.3 Rationale This Recommended Practice was developed as part of a set of Recommended Practices intended to allow modelers to determine the parameters required by any of the common tire models for calculating spindle loads given the road surface profile from a single set of exper
10、imental results, and thus, to eliminate duplicate testing. Copyright SAE International Provided by IHS under license with SAENot for ResaleNo reproduction or networking permitted without license from IHS-,-,-SAE J2704 Issued JAN2005 - 2 - 2. References 2.1 Applicable Publications The following publi
11、cations form part of the specification to the extent specified herein. Unless otherwise indicated the latest revisions of all publications shall apply. 2.1.1 SAE PUBLICATIONS Available from SAE, 400 Commonwealth Drive, Warrendale, PA 15096-0001. SAE J2047Tire Performance Technology SAE J2429Free-Rol
12、ling Cornering Test for Truck and Bus Tires SAE 770870The Effect of Tire Break-in on Force and Moment Properties, K. D. Marshall, R. L. Phelps, M. G. Pottinger, and W. Pelz, 1977. SAE 810066The Effect of Aging on Force and Moment Properties of Radial Tires, M. G. Pottinger and K. D. Marshall 2.1.2 O
13、SHA PUBLICATION Available from the Rubber Manufacturers Association, 1400 K St., N.W., Washington, DC 20005. OSHA Standard 1910.177Servicing Multi-piece and Single Piece Rim WheelsAvailable in wall chart form as #TTMP-7/95. 2.1.3 ISO PUBLICATION Available from American National Standards Institute,
14、Global Engineering Documents, 15 Inverness Way, East Englewood, CO 80112. ISO Standard 17025General requirements for the competence of testing and calibration laboratories 3. Definitions The definitions that follow are of special meaning in this Recommended Practice and are either not contained in o
15、ther Recommended 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
16、 area in contact 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. Copyright SAE International Provided
17、 by IHS under license with SAENot for ResaleNo reproduction or networking permitted without license from IHS-,-,-SAE J2704 Issued JAN2005 - 3 - FIGURE 1INK BLOCK CONTACT AREA PRINT 3.2 Contact Patch Dimensions For purposes of this practice a rectangle is imposed about the contact patch as illustrate
18、d in Figure 1. The rectangles sides touch the most forward, most rearward, leftmost and rightmost points composing the contact patch. The sides are 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 distanc
19、e from the rearward edge of the imposed rectangle (the edge with the most algebraically negative X coordinate) to its forward edge (the edge with the 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 rect
20、angle (the edge with the most algebraically negative Y coordinate) to its rightmost edge (the edge with the most algebraically positive Y coordinate). 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. Copyrig
21、ht SAE International Provided by IHS under license with SAENot for ResaleNo reproduction or networking permitted without license from IHS-,-,-SAE J2704 Issued JAN2005 - 4 - 3.4 Test Program A Test Program is a designed experiment involving a set of the tests described in this practice.14. Nomenclatu
22、re Table 1 lists the symbols used in this document. For further information on items not in Section 4 of this practice please see SAE J2047. TABLE 1SYMBOLS DEFINED Symbol Defined Term ZVertical Deflection FZNormal Force L Contact Patch Length p Inflation Pressure RlLoaded Radius Standard Deviation (
23、Note Subscripts) 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 e
24、lements 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 sys
25、tem, a flat 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 p
26、roduce normal 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 axis
27、.21There are many experimental possibilities: 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. 2In a practical sense the hub of
28、a properly aligned machine will not rotate during loading in this test so fixity is a moot point in this case. Copyright SAE International Provided by IHS under license with SAENot for ResaleNo reproduction or networking permitted without license from IHS-,-,-SAE J2704 Issued JAN2005 - 5 - 6.1.2 MEA
29、SURING 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 mm.3The system shall have a normal force range that allows m
30、easurement of forces equivalent to those existing at 400% of the client specified 100% load. 6.1.2.2 Contact Image Measuring System The system shall give an image of the portion of the tire in contact with the simulated roadway at the target normal force imposed by the loading and positioning system
31、. 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 such other systems as are capable of imaging the static tire/simulated roadway contact. The sy
32、stem 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 of which the roadway is made is unimportant so long as the roadway satisfies the following c
33、riteria. 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 either transverse or longitudinal orientation or in curvature under the machines maximum appl
34、ied 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 appropriate tire and rim standards association, for example, the Tire and Rim Association, Inc. NO
35、TERim stiffness may have a discernable influence on the results. At this time, the presence of this effect has not been established. Further, there is not now a recognized way to appropriately characterize rim stiffness for use in this Recommended Practice. It is planned to address this question by
36、research carried out prior to the five-year review of this practice. 3Should the measuring system sense multiple forces and moments, the output shall be corrected for load cell interaction by a matrix method conceptually equivalent to that discussed in SAE J2429. 4This is a process in which the tire
37、 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 occurs, the total internal reflectance is modified proportionate to the applied pressure and a footpr
38、int image is produced. Copyright SAE International Provided by IHS under license with SAENot for ResaleNo reproduction or networking permitted without license from IHS-,-,-SAE J2704 Issued JAN2005 - 6 - 7. Calibration5Calibrate all measuring system components in accordance with the mandates of the w
39、ritten plan required by the laboratory quality 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 sy
40、stem calibration shall be traceable to the National 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 per
41、tinent performance measures and comments on 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 Apparatus6Preparation of the apparatus shall ensure that the test equipment meets its c
42、alibration at the outset of each test program 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
43、 of the laboratory. The results of process control experiments shall be available to customers on request. 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 mind when selecting test tires since tire properties
44、 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 this document may be used to address, specific tire se
45、lection 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 identical conditions, have experienced approximately the sa
46、me 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 inflation pressure must be specified by the requester.
47、 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 pressure used in the test must be equivalent to the on-ro
48、ad operating inflation pressure. 5If 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. 6If required, Section 7 of J2429 provides example possibilities for a more complex, but rela
49、ted measuring system. Copyright SAE International Provided by IHS under license with SAENot for ResaleNo reproduction or networking permitted without license from IHS-,-,-SAE J2704 Issued JAN2005 - 7 - 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 rim.7For rim wheels used on large vehicles such a
