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 theref
2、rom, 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 2012 SAE International All rights reserved. No part of this pub
3、lication 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: +1 724-776-4970
4、(outside USA) 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/J2731_201205SURFACEVEHICLERECOMMENDEDPRACTICEJ2731 MAY2012 Issued 2006-11Revised 201
5、2-05Superseding J2731 NOV2006 Low Speed Enveloping Test with Perpendicular and Inclined Cleats RATIONALEJ2731 is being revised to correct editorial changes in paragraph 10.3 and 10.4.2. 1. SCOPE This SAE Recommended Practice describes a test method for measuring the forces and moments generated at a
6、 spindle when a tire rolls over a rectangular obstacle, cleat, at very low speed. The cleat used in a particular test condition is configured with its crest either perpendicular, 90, to the path of the tire or optionally with its crest inclined at an angle tothe path of the tire. The carriage to whi
7、ch the spindle is attached is rigidly constrained in position during each test condition so as to provide a good approximation to fixed loaded radius operation. The method discussed in this document provides cleat envelopment force and moment and tire angular position histories as functions of dista
8、nce traveled. These histories are essentially free from variations due to tire non-uniformities. The method applies to any size 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 road lo
9、ad 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 surfaces, paved or otherwise. Within the context of this document, forces a
10、pplied to the road or terrain surface are not considered. 2. REFERENCES 2.1 Applicable Publications The following publications form part of the specification to the extent specified herein. Unless otherwise indicated the latest revisions of all publications shall apply. SAE J2731 Revised MAY2012 Pag
11、e 2 of 12 2.1.1 SAE Publications Available from SAE, 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 J2047 Tire Performance Technology SAE J2429 Free-Rolling Cornering Test for Truck and Bus Tires SAE J2710 M
12、odal Testing and Identification of Lower Order Tire Natural Frequencies of Radial Tires SAE J2730 Dynamic Cleat Test with Perpendicular and Inclined Cleats 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 8100
13、66 The Effect of Aging on Force and Moment Properties of Radial Tires, M. G. Pottinger and K. D. Marshall, 19812.1.2 Rubber Manufacturers Association Publication Available from Rubber Manufacturers Association, 1400 K Street, NW, Suite 900, Washington, DC 20005, Tel: 202-682-4800, www.rma.org.OSHA S
14、tandard 1910.177 Servicing Multi-piece and Single Piece Rim Wheels (Available in wall chart form as #TTMP7/95)2.1.3 ISO Publication Available from ANSI, 25 West 43rd Street, New York, NY 10036-8002, Tel: 212-642-4900, www.ansi.org.ISO Standard 17025 General Requirements for the Competence of Testing
15、 and Calibration Laboratories3. DEFINITIONS The definitions that follow are of special meaning in this document and are either not contained in other Recommended Practices or are worded somewhat differently in this practice. 3.1 The Parallel Axis Tire Coordinate System This system is defined in SAE
16、J2710 and extended in SAE J2730 to allow tire rotation. For axes definitions and associated geometry, please see SAE J2730.3.2 The Tire Forces and Moments This set of spindle centered forces and moments is fully defined in SAE J2730.3.3 Test A Test is execution of the procedure described in this doc
17、ument one time on one tire at a single set of conditions. SAE J2731 Revised MAY2012 Page 3 of 12 3.4 Test Program A Test Program is a designed experiment involving a set of the tests described in this practice.14. NOMENCLATURE Table 1 lists the symbols used in this document. For further information
18、on items not in Section 4 of this practice please see SAE J2047. TABLE 1 - SYMBOLS DEFINED Symbol Defined Term D Distance Traveled FX”Parallel System Longitudinal Force FY”Parallel System Lateral Force FZ”Parallel System Normal Force Angular Displacement of Tire MX”Parallel System Overturning Moment
19、 MZ”Parallel System Aligning Moment RlTire Loaded Radius RlmaxMaximum RlExpected During Test Machine Use V Test Velocity 5. LABORATORY QUALITY SYSTEM REQUIREMENT The laboratory performing the procedures specified in this document shall have a quality system either conforming to ISO 17025 or which ca
20、n be shown to be functionally equivalent to ISO 17025. The elements 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 test machine with a test surface (round or flat bed) capable of rolling test
21、tires over at least a quarter revolution prior to cleat envelopment, as defined in the test conditions, Section 10.4. It is preferable thatthe apparatus allow at least a full tire revolution before cleat envelopment starts. This would allow the relaxation phenomena to become complete.The test surfac
22、e shall allow mounting of rectangular cleats, one at a time, as specified in this practice. The machine shall have an instrumented spindle capable of measuring three forces (FX”, FY”, and FZ”) and two moments (MX”and MZ”)developed during tire envelopment of the cleat. Additionally, the relative disp
23、lacement of the spindle with respect to the test surface in the X”-Axis direction, D, and the tire angular displacement, , about the spindle shall be measured during envelopment using absolute encoders. The speed of travel during envelopment does not have to be constant due to the angular displaceme
24、nt measurements that are taken. Figure 1 is a schematic of both common machine types: a round test surface (drum) and a plank. Appropriate data acquisition equipment is considered to be part of the apparatus. The space housing the loading machine is also considered to be part of the apparatus.1There
25、 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.SAE J2731 Revised MAY2012 Page 4 of 12 +DR
26、oadwheelTireCleatFixed DistanceDRUMFixed DistanceFixed DistanceFixed DistanceFIGURE 1A - ROUND TEST SURFACE OR DRUM MACHINE D+TirePlankFixed RadiusFixed, Rl,Loaded RadiusFixed RadiusFixed, Rl,Loaded RadiusFixed RadiusFixed, Rl,Loaded RadiusFixed RadiusFixed, Rl,Loaded RadiusFixed RadiusFixed RadiusF
27、ixed RadiusFixed, Rl,Loaded RadiusFIGURE 1B - PLANK OR FLAT SURFACE FIGURE 1 - TEST MACHINE SCHEMATICS 6.1 Environmental Vibration and Isolation Cleat envelopment generates significant forces. The instrumented spindle will respond to force signals regardless of whether they reach it directly from th
28、e tire/wheel system, as is desired, or, as environmental noise, from a source in the laboratory environment through the floor and then the machine frame. The machines planned environment should be tested for significant structure borne vibration arising from the laboratory environment prior to insta
29、llation.2If the vibration found is insignificant from the standpoint of this document, the machine can be mounted on a normal foundation. If significant environmentally associated vibrations are discovered, which will affect results, either follow the mitigation practices described in SAE J2730 or f
30、ilter the data suitably so as to suppress spurious results due to environmental vibration.2Significance is a judgment that should be made by a competent expert in machine isolation.SAE J2731 Revised MAY2012 Page 5 of 12 6.2 Loading System The loading system shall maintain the tire at a slip angle of
31、 0 0.05 and an inclination angle of 0 0.05, common machine specifications when this document was drafted. The system shall be capable of loading the tire to at least twice the test requester specified 100% load. It shall be capable of loading the tire to an average normal force accurate to within 1.
32、0% of the test machines full-scale normal force range when no cleat is mounted and to an average loaded radius accurate to within 0.5 mm either with or without a cleat mounted.3Loading shall be possible with the test surface either static or rolling. The loading system must be stiff enough to assure
33、 an essentially constant distance between spindle and test surface during the tire envelopment process. So long as the machines structural design is adequate, it is not important whether the machine is designed such that the Z”axis is directed horizontally or vertically.6.3 Measuring System 6.3.1 In
34、strumented Spindle The spindle shall be capable of measuring three forces (FX”, FY”, and FZ”) and two moments (MX”and MZ”). The output shall be corrected for load cell interaction by a matrix method conceptually equivalent to that discussed in SAE J2429.The capacities recommended in this section are
35、 best estimates at the time this document was prepared, but are not known to be correct based on experimental evidence. Force and moment measurements shall be accurate to 0.5% of each load cells maximum capacity. The load cell capacities given in Table 2 are believed to be adequate, but are best est
36、imates. The loaded radius needs to be set so that the maximum vertical force is not exceeded when the tire envelops the cleat.NOTE: A rotating wheel force transducer may be used in place of an instrumented spindle. If this is done, verify that the apparent vertical stiffness of the transducer is con
37、stant independent of its angular orientation with respect to the center of tire contact. TABLE 2 - MINIMUM LOAD CELL CAPACITIES BASED ON FORCE AND MOMENT Force or Moment Load Cell Capacity Longitudinal Force -(Maximum 100% Tire Load4) FX” (Maximum 100% Tire Load)Lateral Force -(Maximum 100% Tire Loa
38、d) FY” (Maximum 100% Tire Load) Normal Force -(300% Maximum Tire Load) FZ” 0 Overturning Moment -FY”Capacity times Rlmax MX” FY”Capacity times RlmaxAligning Moment -FY”Capacity times Rlmax MZ” FY”Capacity times RlmaxNOTE: By way of example, assume that the machine in question was designed to test ti
39、res with 100% loads up to 9000 N with a maximum loaded radius in test of 0.4 m. That would mean that the load cell capacities would need to be as follows. 3Due to tire non-uniformity, the normal force and loaded radius vary with tire angular position. Thus, when the tire is rolling the best solution
40、 is to set the tire normal force or loaded radius to a value most correspondent to its average value during a tire rotation.4The Maximum 100% Tire Load is the 100% load for the largest load capacity tire the machine is designed to test.SAE J2731 Revised MAY2012 Page 6 of 12 TABLE 3 - DESIGN LOAD CEL
41、L CAPACITY EXAMPLE Force or Moment Load Cell Capacity Longitudinal Force -9,000N FX” 9,000N Lateral Force -9,000N FY” 9,000N Normal Force -27,000N FZ” 0 Overturning Moment -3,600N-m MX” 3,600N-m Aligning Moment -3,600N-m MZ” 3,600N-m 6.3.2 Loaded Radius Instrumentation The system shall measure loade
42、d radius over a range from at least 0.4 times the nominal bead seat diameter of the smallest wheel that is expected to be mounted up to 1.2 times the unloaded crown radius of the largest tire expected to be tested. The measurement shall be accurate within 0.5 mm. 6.3.3 Distance Traveled Instrumentat
43、ion The measurement system shall determine distance traveled by the tire by measuring test surface position with a resolution of 1 mm or better. The distance traveled measurement shall drive data acquistion in Section 6.4. 6.3.4 Wheel Angular Displacement Instrumentation An absolute encoder system s
44、hall monitor tire angular position at 0.10 increments of rotation per count or better.56.4 Data Acquisition Test data for all channels shall be acquired at a rate corresponding to the resolution in traveled distance, which is defined in Section 6.3.3. Data shall be simultaneously sampled and held at
45、 each sample of the test surface position. Data acquisition shall begin at least 50 mm before the test cleat first encounters the tire and shall end at least 50 mm after the cleat has passed out of contact with the tire. The system shall feature anti-aliasing filters applicable to the analog signals
46、 such as load cells with corner frequencies set to less than 25% of the estimated sampling frequency.6Alternatively, the data could be time sampled at a frequency sufficiently large to insure approximately the same spatial resolution provided by the encoder triggered method of data acquisition. For
47、example, sampling at 300 Hz would be sufficient at a 1 km/hr bed speed. In time sampled data acquisition the test surface encoder reading becomes one of the sampled data channels.6.5 Test Surface The test surface shall be stiff enough that it may be assumed rigid for the purposes of this experiment
48、and will provide a good foundation for cleat attachment. The surface curvature shall be at most 1.176 m-1(drum diameter 1.7 m or more, or flat bed).5A 4096-count encoder meets this requirement. By way of example, this would divide the circumference of common Truck Bus Radials and all smaller tires i
49、nto circumferential increments of less than 1 mm per count.6While the test speed does not have to be precise, see Section 6, it should be reasonably well determined to facilitate filter selection.SAE J2731 Revised MAY2012 Page 7 of 12 6.6 Test Cleats The purpose of the cleats, which are sized so that they encounter the entire tread width, is to excite a nonlinear res
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