1、. 1/ ,1/ 11111111111111111111111111111/ 1111/111/11111 I11111 1111111 1/3 1176 00166 6305NASA Contractor Report 165720NASA-CR-165720I 9?J / ao.2 f SA COMPARISON OF SOME STATIC AND DYNAMIC G(MECHANICAL PROPERTIES OF 18x5.5 AND49x17 TYPE VII AIRCRAFT TIRES AS MEASUREDBY THREE TEST FACILITIESRichard N.
2、 Dodge and Samuel K. ClarkTHE UNIVERSITY OF MICHIGANAnn Arbor, Michigan 48109Grant NSG-1494July 1981-. : .-:- .( :- : .-.: :.:“: ,. j NlSINational Aeronautics andSpace AdministrationLangley Research CenterHampton,Virginia 23665Provided by IHSNot for ResaleNo reproduction or networking permitted with
3、out license from IHS-,-,-, IProvided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-TABLE OF CONTENTSPAGESUMMARY 1INTRODUCTION 3SYMBOLS 6TEST FACILITIES AND PROCEDURESNASA FacilityFDL FacilityUniversity of Michigan FacilityRESULTS AND DISCUSSIONStatic Test R
4、esultsPure vertical loading Vertical spring rate:Contact patch:Combined vertical and lateral loading Lateral spring rate:Lateral hysteresis:Combined vertical and torsional loadings Torsional spring rate:Torsional hysteresis:Combined vertical and fore-and-aft loadings Fore-and-aft spring rate:Fore-an
5、d-aft hysteresis:Slow-Rolling Yawed Test ResultsRelaxation length Steady-state side force Self-aligning torque-Dynamic Test ResultsPure vertical loading Yawed rolling side force-Self-aligning torque under yawed rolling-CONCLUDING REMARKSiProvided by IHSNot for ResaleNo reproduction or networking per
6、mitted without license from IHS-,-,-Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-A COMPARISON OFSOME STATIC AND DYNAMIC MECHANICAL PROPERTIES OF18X5.5 AND 49Xl7 TYPE VII AIRCRAFT TIRESAS MEASURED BY THREE TEST FACILITIESRichard N. Dodge and Samuel
7、 K. ClarkThe University of MichiganSUMMARYMechanical properties of 49xl7 and 18x5.5 type VII aircrafttires were measured during static, slow rolling, and high-speedtests, and comparisons were made between data as acquired on in-door drum dynamometers and on an outdoor test track. In addi-tion, mecha
8、nical properties were also obtained from scale modeltires and compared with corresponding propertiesfrofull-sizetires. While the tests covered a wide range of tire properties,results seem to indicate that speed effects are not large, scalemodels may be used for obtaining some but not all tire proper
9、-ties, and that predictive equations developed in NASA TR R-64are still useful in estimating most mechanical properties., ofProvided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-Provided by IHSNot for ResaleNo reproduction or networking permitted without l
10、icense from IHS-,-,-INTRODUCTIONTo analyze adequately the takeoff, landing and taxicharacteristics of modern dayairraft,it is essential thatlanding gear designers have accurate data available on manytire mechanical properties. The measurement of these mechani cal properties, however, is an expensive
11、 and lengthy processsince aircraft tires are usually heavily loaded and operate ofhigh speeds, thus requiring large and costly test equipment tosimulate their operating conditions. Only two such facilitiesexist in the United States for the controlled study of suchtire characteristics at realistic sp
12、eeds and operating condi tions: the Landing Loads and Traction Facility at the NASALangley Research Center, and the Flight Dynamics Laboratoryunder the Air Force Wright Aeronautical Laboratories at Wright Patterson Air Force Base (FDL).At the present time, aircraft landing gear designers areforced t
13、o rely on very limited aircraft tire mechanical propertydata furnished by tire or component manufacturers or by thegovernment laboratories of NASA and the Air Force. Extensiveuse is still being made of NASA Technical Report R-64, “MechanicalProperties of Aircraft Tires“ reference 1, which summarizes
14、the state of knowledge concerning mechanical characteristicsof such tires as it existed about 20 years ago, and based almostentirely upon static or very slow rolling data. Almost nothingis currently available which describes the influence of speedon such tire characteristics.3Provided by IHSNot for
15、ResaleNo reproduction or networking permitted without license from IHS-,-,-4Recognizing the lack of such data, aircraft industryrepresentatives have for some years ureed a coherent programfor assessing the influence of speed and other dynamiccharacteristics on aircraft tire mechanical properties, an
16、d,further, have urged programs designed to assess the continuingvalidity of NASA TR R-64 in light of more modern aircraft tiredesigns. These efforts became focused in the industry committeewhich is primarily active in this area - the SAE Committee A5.Under the sponsorship of this committee, a progra
17、m was originatedjointly by the Landing Dynamics Office at NASA-Langley andthe Flight Dynamics Laboratory at Wright Patterson Air ForceBase. These two groups agreed to a co-operative test programgenerated jointly by them in conjunction with the SAE A5committee, and The University of Michigan agreed t
18、o conduct amodest scale-model tire measurement program to determine theadequacy of scale model techniques in assessing speed anddynamic effects on aircraft tire mechanical properties.Two Type VII, modern aircraft tire designs were chosen forthis program: size 49xl7 in a 26-ply rating and size 18x5.5
19、 ina 14-ply rating. The test plan originally prepared to meet theneeds of the program is given in Appendix B, and it basicallyinvolves evaluating the usual vertical, lateral, fore-and-aftand torsional static characteristics of both tire sizes, to gether withmesurementsof slow rolling relaxation leng
20、th, cor nering force, and self aligning torque. In addition, and mostimportant, dynamic vertical load deflection, vertical hysteresis,cornering force and self aligningorque,measurements were to becarried out on both tire sizes over a speed range to 100 knots.Provided by IHSNot for ResaleNo reproduct
21、ion or networking permitted without license from IHS-,-,-Each of these properties has important uses in analyzingoperating characteristics of the runway-tire-1anding gearinteraction in modern aircraft. For example, the verticalload deflection characteristics directly affect landing gearstrut design,
22、 while lateral and torsional characteristics ofthe tires are directly related to cornering and yaw responseand are thus important to shimmy analysis Tire fore-and-aftelastic properties affect anti-skid and braking design, andare therefore important in their own right.The program was initiated in 197
23、5 with the acquisition ofthe tires through the Aeronautical Systems Division, Wright Patterson Air Force Base and tests were conducted independentlyby both NASA-Langley and the Flight Dynamics Laboratory. In 1978,NASA initiated a Research Grant with the University of Michiganto conduct an analysis o
24、f the obtained data and to examinevarious methods for the transformation of the data from thestatic to the dynamic case. The purpose of this report is topresent the results of that effort.5Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-SYMBOLSValues
25、 are given in both SI and U.S. Customary Units.The measurements were made in U.S. Customary Units,CiConstants relating model spring constants to prototypeD - Outside diameter of free tireEh - Tire membrane stiffnessFxFyFzhKKALYMzNPoQvaxayaznny6- Fore-and-aft force (ground force parallel to direction
26、of motion)- Lateral force (perpendicular to direction of motion)- Vertical force- Half-length of the tire-ground contact area (footprint)- Spring constant- Lateral spring constant- Yawed-rolling - relaxation lengthTurning or twisting moment about a vertical axis throughthe wheel center- Cornering po
27、wer- Inflation pressure at zero vertical load (gage)- Dimensionless force ratio used in relating model forcesto prototype forces- Horizontal rolling speed- Fore-and-aft deflection- Lateral deflection- Vertical deflection- Dimensionless deflection ratio used in relating modeldeflections to prototype
28、deflections- Lateral hysteresis parameter- Yaw angleProvided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-TEST FACILITIES AND PROCEDURESThe tires used in this program were 49x17, 26 ply-ratingand 18x5.5, 14 ply-rating, Type VII aircraft tires which weresel
29、ected in quantities of 5 each from Air Force inventory,chosen from the same manufacturer and with closely spacedserial numbers and dates of manufacture. Each of the tireswas subjected to three break-in taxi runs of two miles at ratedpressure and load. The scale model tires used in this studywere des
30、igned and built by the University of Michigan whichhad experience (reference 2) in the modeling of aircraft tires.The scale models were constructed to a 12:1 ratio for the49x17 tire and to a 4:1 ratio for the 18x5.5 tire. Table 1provides a summary of pertinent geometric properties of thefull-size ti
31、res and their corresponding scaled models.The test plan for each tire is outlined in Appendix B. Thisplan was used by each facility, although it was not possible foreach organization to measure all properties identified in theplan.NASA Facility.NASA used the same basic test equipment to determine mo
32、stof the tire static vertical, lateral, and fore-and-aft stiffnesscharacteristics. This equipment consisted of a bearing plateupon which the test tire rested under a vertical load, and theinstrumentation necessary to monitor the various tire loadingsand displacements. Tire loadings included the vert
33、ical load,which was controlled by the test carriage hydraulic system,and either the lateral or fore-and-aft load which was appliedto the bearing plate by means of a hydraulic piston. The7Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-8magnitude of t
34、he vertical load was measured by load cellsunder the bearing plate, whereas other loads were measuredby a load cell located between the hydraulic piston and arigid backstop. The displacements were measured with dialgages and motion transducers.The dynamic tire data obtained by NASA came from testsco
35、nducted on the Langley aircraft landing loads and tractionfacility. A description of this facility can be found innumerous NASA publications, of which reference 3 is a goodexample. Both test carriages were employed in this program.The large carriage witha speed potential of 110 knots servedas the te
36、st bed for the 49x17 tire and the small carriagecapable of speeds to 120 knots was used in testing the smallertire. The runway surface for both tires was dry concrete.The slow-rolling, quasi-static NASA data were obtained withthe same facility used to acquire the dynamic data exceptinstead of being
37、propelled by the water jet the carriages weretowed over the test section by a tug.FDL FacilityThe Flight Dynamics Laboratory static and slow-rollingquasi-static tests were performed on the flat surface TireForce Machine (TFM). The basic features of this machineinclude a tire/wheel assembly housed in
38、 a frame containingsix load cells through which the loads are applied and theresultant tire forces and moments are reacted, a twenty-footflat movable test bed, and a computer-controlled automatic datalogging system.Provided by IHSNot for ResaleNo reproduction or networking permitted without license
39、from IHS-,-,-The dynamic data were obtained from the computer-controlled,120-inch dynamometer test apparatus. The major features of thisapparatus are a test carriage which supports the tire and ispositioned by a servo-controlled hydraulic system, a 120-inchdiameter dynamometer wheel, and a complete
40、process controlsystem which provides automatic sequencing and control of thetest dynamometer and receives, processes, displays and recordsall test data.A more complete description of these two test systems canbe found in references 4 and 5.University of Michigan FacilityStatic tire data at the Unive
41、rsity of Michigan were.obtained primarily from tests conducted on its small scalestatic test machine. This machine consists of a rigid bearingplate mounted on ball bearings, a hinged dead-weight arm andyoke for applying vertical loads to the test tire mounted in theyoke, a screw drive and load trans
42、ducer system for applyingand measuring lateral and fore-and-aft loads to the bearingplate, and dial gages and variable transformers for measuringdisplacements. A more complete description of this apparatusis given in reference 6.The slow-rolling quasi-static, yawed tests were conductedon a 30-inch d
43、iameter cast iron road wheel discussed in reference2. This apparatus consists primarily of a driven roadwheel,a hinged arm equipped with a tire yoke, and transducers tomonitor lateral force andselfaligningtorque.Dynamic data were obtained from tests conducted on theUniversity of Michigan 40-inch dia
44、meter inside-outside road-9Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-wheel. This apparatus consists of a driven cantileveredroadwheel with apparatus similar to that on the smaller wheel.All tests described in this report were obtained on the ou
45、t side surface of this wheel.10Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-RESULTS“ AND DISCUSSIONSince the participants in this testprogamused differentequipment in making their measurements, it was necessary toconvert most of the raw data to so
46、me common format. This con version was done, and to some extent it masked individual dif ferences in measuring techniques, as, for example, curved steeldrums as opposed to flat concrete surfaces. However such apresentation does allow direct comparison of results betweendifferent test facilities.Seve
47、ral pertinent tire mechanical properties were calcu lated in terms of parameters defined in“ reference I and theseare presented, where possible, to illustrate any changes asso ciated with the newer type VII tires.STATIC TEST RESULTSPure Vertical Loading - The load-deflection curves presentedin figur
48、e I for the 49xl7 tire and in figure 2 for the 18x5.5.tire include the four vertical loading conditions. As is com monly observed, a hysteresis loop in the vertical load deflec tion curve is obtained but the load deflection relationship isnearly linear for increasing load except for relatively lowvalues of the load.While there is some variation in the data obtained betweenthe participants as noted in figures 1 and 2, no consistent dif ference of any mag
