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 2013 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.orgSAE values your input. To provide feedback on this Technical Report, please visit http:/www.sae.org/technical/standards/AIR5797AEROSPACEINFORMATION REPORT AIR5797Issued 2008-08 Reaffirmed 2013-10 Aircra
5、ft Tire Wear Profile Development and Execution for Laboratory Testing RATIONALE AIR5797 has been reaffirmed to comply with the SAE five-year review policy. TABLE OF CONTENTS 1. SCOPE 3 2. REFERENCES 3 2.1 Applicable Documents 3 2.1.1 SAE Publications. 3 2.1.2 U.S. Government Publications 3 2.2 Defin
6、itions . 4 3. TIRE PREPARATION . 4 3.1 Tire Conditioning. 4 3.2 Break-in Procedure . 4 3.3 Tire Inflation 4 4. MECHANICAL PROPERTIES 4 4.1 Mechanical Properties - Dynamometer 4 4.1.1 Sinusoidal Yaw Sweep . 6 4.1.2 Braking Sweep 7 4.2 Supplemental Information - Tire Force Machine Footprint Data. 8 4.
7、2.1 Load Surface. 8 4.2.2 Yaw Angle and Tire Speed . 9 4.2.3 Py and Px Footprints. 9 5. ENERGY CALCULATIONS 9 5.1 Side Wear Energy. 9 5.2 Drag Wear Energy 9 5.3 Power 10 5.4 Total Wear Energy 10 6. WEAR SURFACE . 10 7. WEAR MODEL 10 7.1 Field Conditions 10 7.2 Tire Cross Sections. 10 7.3 Spreadsheet
8、 11 7.3.1 Speed 12 7.3.2 Yaw Angle . 12 7.3.3 Brake Force. 12 7.3.4 Energy. 13 8. WEAR TESTING. 13 8.1 Initial Conditioning. 13 8.1.1 Measurement of Material Removed 13 8.2 Number of Test Articles 13 8.3 Data Collection 14 8.4 Tire Indexing . 14 9. TESTING CORRELATION . 14 10. NOTES 15 FIGURE 1 COOR
9、DINATE SYSTEM 5 FIGURE 2 FORCE AND MOMENT DIAGRAM 5 FIGURE 3 YAW SWEEP DATA . 6 FIGURE 4 SLIP DATA 7 FIGURE 5 FORCE AND MOMENT DIAGRAM - FOOTPRINT 8 FIGURE 6 EXAMPLE WEAR MODEL . 11 TABLE 1 TRAINER SIZED TIRE 14 TABLE 2 FIGHTER SIZED TIRE 15 TABLE 3 TRANSPORT SIZED TIRE . 15 SAE INTERNATIONAL AIR579
10、7 Page 2 of 15_ 1. SCOPE This SAE Aerospace Information Report (AIR) describes the current process for performing comparative wear testing on aircraft tires in a laboratory environment. This technique is applicable to both radial and bias tires, and is pertinent for all aircraft tire sizes. This AIR
11、 describes a technique based upon “wear” energy. In this technique, side wear energy and drag wear energy are computed as the tire is run through a prescribed test program. The specifics that drive the test setup conditions are discussed in Sections 4 through 7. In general, the technique follows thi
12、s process: A test profile is developed from measured mechanical property data of the tires under study. Each tire is repeatedly run to the test profile until it is worn to the maximum wear limit (MWL). Several tires, typically 5 to 10, of each tire design are tested. Wear energy is computed for each
13、 test cycle and then summed to determine total absorbed wear energy. An index is calculated for each tire design. This is accomplished by dividing the total linear inches of wear at the most worn point into the total wear energy. The indexes are then normalized to provide a comparative wear rate. Th
14、e described technique is not meant to provide an absolute wear rate or wear index because the technique does not produce results that allow the user to say a tire will last for a specific number of landings. However, it does provide a comparative index. It will make a distinction from one tire desig
15、n to another by indicating a percentage difference in abrasive wear rate under representative operational conditions. The technique has been demonstrated in a number of test programs and is shown to have an extremely high correlation to field data. Supporting data is included in Section 9. 2. REFERE
16、NCES 2.1 Applicable Documents The following publications form a part of this document to the extent specified herein. The latest issue of SAE publications shall apply. The applicable issue of other publications shall be the issue in effect on the date of the purchase order. In the event of conflict
17、between the text of this document and references cited herein, the text of this document takes precedence. Nothing in this document, however, supersedes applicable laws and regulations unless a specific exemption has been obtained. 2.1.1 SAE Publications Available from SAE International, 400 Commonw
18、ealth Drive, Warrendale, PA 15096-0001, Tel: 877-606-7323 (inside USA and Canada) or 724-776-4970 (outside USA), www.sae.org. Cornering and Wear Behavior of the Space Shuttle Orbiter Main Gear Tire Author(s): Daugherty, Robert H.; Stubbs, Sandy M., NASA Center: Langley Research Report Number: SAE PA
19、PER 871867 2.1.2 U.S. Government Publications None. SAE INTERNATIONAL AIR5797 Page 3 of 15_ 2.2 Definitions CONICITY: The condition of an asymmetric tire construction that causes a tire to generate a lateral force. FOOTPRINT: The shape of a loaded tire in its contact patch. The shape varies based on
20、 the loading, and the inflation pressure of the tire. LIFE CYCLE COST (LCC): Total cost of an object or system, factoring in everything from production, life, maintenance, and disposal. MAXIMUM WEAR LIMIT (MWL): The maximum number of cords that can be worn through before the tire is no longer safe t
21、o use, as determined by the tire manufacturer. Py: Tire tread contact pressure distribution in the lateral or y-direction. Px: Tire tread contact pressure distribution in the longitudinal or x-direction. PLYSTEER: The turning moment produced from the tire in straight roll. This is created by the con
22、struction of the tire. 3. TIRE PREPARATION 3.1 Tire Conditioning Before break-in, a tire is conditioned by mounting it on a suitable rim, inflating it to the unloaded rated inflation pressure, and allowing it to remain in this condition for 24 hours at ambient temperature, between 60 F (15 C) and 10
23、0 F (38 C). 3.2 Break-in Procedure After conditioning, a tire is subjected to taxi rolls to perform “break-ins.” The test tire is inflated to the unloaded rated inflation pressure, and then rolled at taxi speeds for a one-mile taxi roll, followed by a two-mile taxi roll. Each taxi is performed at th
24、e tires rated, or usage load. The taxi speed is typically 20 to 40 mph (32 to 64 kph). The tire is cooled to ambient before starting any of the taxi break-in rolls. 3.3 Tire Inflation During tire wear testing the inflation pressure is set to either a rated or a field usage pressure. Typically, the t
25、ire pressure is not corrected for flywheel curvature, and the footprint contact pressure on the internal drum is similar to a flat plate contact pressure. 4. MECHANICAL PROPERTIES Mechanical property tests are conducted on each of the tire designs that are to be tested. 4.1 Mechanical Properties - D
26、ynamometer Sinusoidal yaw sweeps (described in 4.1.1) and brake sweeps (described in 4.1.2) are performed using the internal drum dynamometer prior to conducting wear testing. The resulting data is input into the wear energy model, as described in Section 7, and the dynamometer surface is prepared a
27、s described in Section 6. Figures 1 and 2 show the coordinate system used throughout dynamometer testing. Figure 3 shows an example of the collected data. The linear regression equation is utilized in generating the wear model. SAE INTERNATIONAL AIR5797 Page 4 of 15_ VFO.B.I.B.-Yaw+ Yaw( O.B. Acting
28、 Force ) ( I.B. Acting Force )+Y+XR.H. Coordinate SystemFIGURE 1 - COORDINATE SYSTEM FZ - Normal ForceFX- Longitudinal ForceMX- Overturning MomentFY- Lateral ForceMY- Rolling Resistance MomentMZ- Self Aligning TorqueFYFXFZMZMXMYRight Hand Coordinate SystemFIGURE 2 - FORCE AND MOMENT DIAGRAM All coor
29、dinate systems referenced in this document have an origin coincident with the tire/wheel centerline and the axle centerline. SAE INTERNATIONAL AIR5797 Page 5 of 15_ 4.1.1 Sinusoidal Yaw Sweep A sinusoidal yaw sweep of 5 degrees is performed with the vertical load and inflation pressure maintained at
30、 test conditions. The flywheel velocity is held within the 20 to 40 mph (32 to 64 kph) speed range, typical of aircraft taxi-way turning operations. These speeds are also those at which the turns will occur in the actual wear test profile. The relationship between side load and yaw angle is establis
31、hed for the tire designs under test. This value is used to predict the side load forces the tire will see while yawing, and becomes a driver in the tires wear energy model. Equation 1 is determined through linear regression by utilizing the data collected on one tire of each design under test. bmFY+
32、= (Eq. 1) where: FY = Side Load (dependent variable) m = slope of data g524 = yaw angle b = side load offset due to ply steer, conicity, and tire asymmetries Side load versus Yaw AngleFy = -314.29 + 34.81-2500-2000-1500-1000-50005001000150020002500-6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6Yaw Angle (deg)Side L
33、oad (lbs)Fy Test Linear (Fy Test )FIGURE 3 - YAW SWEEP DATA SAE INTERNATIONAL AIR5797 Page 6 of 15_ 4.1.2 Braking Sweep During this event, the vertical load and the flywheel velocity are held constant. The flywheel speed is typically set at a value between 40 and 80 mph (64 and 129 kph). The brake f
34、orce is ramped up until approximately 10% slip is achieved. This data is regressed as follows: g184g185g183g168g169g167=ZXFFAY (Eq. 2) where: Y = Percent slip A = Constant FX= Drag load FZ= Vertical load This test predicts drag loads that will be seen during testing, and feeds the wear energy model.
35、 Figure 4 depicts a graphic example of this data, gathered from multiple test tires. In this plot, the X-axis represents the coefficient of friction (Mu) which is equal to FX/ FZ. The Y-axis represents the difference in test tire speed and flywheel speed expressed as a percentage. Mu versus % Slipy
36、= 11.965x012345670 0.1 0.2 0.3 0.4 0.5 0.6 (lb/lb)% SlipWheel Slip Linear (Wheel Slip )FIGURE 4 - SLIP DATA SAE INTERNATIONAL AIR5797 Page 7 of 15_ 4.2 Supplemental Information - Tire Force Machine Footprint Data To develop tire footprint pressure distribution data, the tire is inflated to test pres
37、sure, mounted on a suitable yoke or mandrel, and rolled over a flat surface. The Tire Force Machine (TFM) located at the LGTF at Wright Patterson AFB, Ohio is one test platform that is capable of performing this type of test. The TFM allows a tire to be rolled at slow speeds at controlled vertical l
38、oads, yaw angles, and camber angles. The machine measures and records the tire reaction forces and moments, table speed, table position, tire deflection, tread contact pressures in the x, y, and z directions, and tread contact slip in the x and y directions. Figure 5 graphically depicts the TFM and
39、shows the coordinate system used during this testing. OutboardInboardTable Travel+ Yaw-Yaw+Mz-Fx-Fy+Fz-Mx-MyPressure Sensors(2D) 23 Aug 2005 6500lb 200 psi yaw = -3 27x7.75-r15/12 yaw -3 camber 0510X(in)12345678910Y(in)Pz(psi)476.188439.375402.563365.75328.938292.125255.313218.5181.688144.875108.063
40、71.2534.43751-1-2.375-39.1875Sensor OutputFIGURE 5 - FORCE AND MOMENT DIAGRAM - FOOTPRINT 4.2.1 Load Surface The loading surface used to measure the tread contact forces is a flat aluminum plate (TFM table). At least one full tire revolution should be completed before the test tire reaches the senso
41、r array. This allows the tires reaction forces to stabilize before being measured by the sensor array. To maintain a uniform friction coefficient, assure accurate data development, and conduct an effective test, any contamination on the surface of the flat metal plate should be removed prior to test
42、ing the tires. The load surface and sensor array includes the capability to measure tread contact pressure in each of the x, y, and z directions, and tread slip in the x and y direction. SAE INTERNATIONAL AIR5797 Page 8 of 15_ 4.2.2 Yaw Angle and Tire Speed Footprint Data is typically collected at y
43、aw angles of 0, 3, and 5 degrees, with the test tire driven down the test surface at a speed of approximately 2 in/s (50 mm/s). 4.2.3 Py and Px Footprints The data from the tread contact shear stresses, as measured by the Py and Px sensors, is important when determining wear patterns. Experience has
44、 shown that the areas where the highest shear forces are present are normally the areas of highest wear rates. The tire wear pattern can often be predicted by evaluating Py values during yawed rolling and Px values during un-braked straight rolling. Proper balance between turning and braking in the
45、test profile is established using this information. Additionally, these parameters are used in the wear profile development stage. 5. ENERGY CALCULATIONS 5.1 Side Wear Energy Side Wear Energy is a theoretical quantity derived from the distance traveled in the Y-direction multiplied by the force in t
46、he Y-direction (Reference 2.1.1). The distance traveled in the Y-direction is approximated as the roll distance is multiplied by sine of the yaw angle. This calculation has shown excellent correlation between predicted and measured energy levels. Equation 3 shows this equation: ()YXFdSWE = sin (Eq.
47、3) where: SWE = Amount of energy from side forces wearing the tire = Yaw angle dX= Roll distance in X-direction FY= Force on tire in the Y-direction 5.2 Drag Wear Energy Drag Wear Energy is also a theoretical quantity developed at the Wright-Patterson LGTF during developmental tire wear testing. The drag wear energy is calculate
