1、Designation: F 377 03Standard Practice forCalibration of Braking/Tractive Measuring Devices forTesting Tires1This standard is issued under the fixed designation F 377; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of las
2、t revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This practice gives procedures for the calibration of:reference load cellscalibration platform systems by using a refere
3、nce load cellstatic calibration of braking/tractive force on locked wheelsof tire test trailers, instrumented vehicles, and laboratory tiretesting machines by using the calibration platform system as acalibration fixture.1.2 The values stated in SI units are to be regarded asstandard. The values in
4、parentheses are for information only.1.3 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory lim
5、itations prior to use.2. Referenced Documents2.1 ASTM Standards:2E 74 Practice for Calibration of Force-Measuring Instru-ments for Verifying the Force Indication of Testing Ma-chinesF 538 Terminology Relating to Characteristics and Perfor-mance of Tires3. Terminology3.1 Definitions:3.2 bias, nthe di
6、fference between the average measuredtest result and the accepted reference value; it measures in aninverse manner the accuracy of a test.3.3 longitudinal force, F, of a tire, nthe component ofthe tire force vector in the X direction.3.4 vertical load, nthe normal reaction of the tire on theroad whi
7、ch is equal to the negative of normal force.4. Summary of Practice4.1 Reference-load cells shall be calibrated using proce-dures and equipment traceable to the National Institute ofStandards and Technology (NIST), or appropriate nationalstandards organization.NOTE 1Practice E 74 may be used as an al
8、ternative method forload-cell calibration.4.2 The calibrated reference-load cell is used to calibrate thecalibration-platform systems or used as the longitudinal forcesensor. The tire test trailer, instrumented vehicle, or laboratorytire testing machine is calibrated with the platform.5. Significanc
9、e and Use5.1 Calibration is essential in the use of various test plat-forms and devices to insure that the test results generated bythese test devices are accurate, repeatable and meaningful. Thisstandard gives the necessary instructions for the calibration ofall of the test devices cited in the Sco
10、pe.6. Apparatus6.1 The calibration system consists of the following basiccomponents:6.1.1 PlatformThe platform on which the test wheel isplaced shall have a flat high friction top surface. The platformshall be of sufficient dimensions to support the entire tirecontact patch throughout the calibratio
11、n process. A low frictionbearing (an air bearing is recommended) permitting freehorizontal motion and capable of sustaining a vertical loadequal to the largest anticipated wheel load shall support theplatform. The longitudinal movement shall be sufficient toobtain the necessary required force levels
12、. The platform mayalso be instrumented with integrated transducers (Force Sen-sors) to measure vertical and longitudinal forces.6.1.2 Force Generation ApparatusA system, capable ofdeveloping a longitudinal force sufficient for the calibration ofthe operating range of the device, shall be used. The f
13、orce shallbe applied along the longitudinal centerline of the platform.6.1.3 Force SensorsSensors to measure applied forces inthe vertical and longitudinal directions that shall be used tocalibrate braking/tractive measuring devices. These sensorscan be integrated force transducers located in the pl
14、atform,1This practice is under the jurisdiction of ASTM Committee F09 on Tires and isthe direct responsibility of Subcommittee F09.10 on Structural Integrity.Current edition approved Dec. 1, 2003. Published January 2004. Originallypublished as F 377 74. Last previous edition F 377 94.2For referenced
15、 ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Cons
16、hohocken, PA 19428-2959, United States.scales or tension load cells. Sensors shall have sufficientmeasurement range to cover the maximum anticipated testwheel forces. Sensors shall be mounted in a manner such thatcross-axis forces will not adversely affect the accuracy. Theforce sensor instrumentati
17、on shall have the capability to allowfor the recording of data, such as a chart recorder, data logger,or visual output that allows for manual logging of data.6.1.4 Reference Load CellThe force standard that pro-vides direct traceability to NIST or appropriate national stan-dards organization that sh
18、all be used to certify other forcesensors or weights used within this standard. If integratedplatform transducers are not used, the reference load cell maybe used as the longitudinal force sensor during calibration ofthe braking/tractive measuring device. The reference load cellshall have sufficient
19、 measurement range to cover the maximumanticipated forces.7. Calibration of the Reference Load Cell and ForceSensors7.1 Three procedures are covered: (1) calibration of thereference-load cell, (2) calibration of the longitudinal forcesensor, and (3) calibration of the vertical load sensor. Repeatthe
20、 appropriate calibrations when any relevant component ischanged or altered (see ASTM Manual 7). Repeat the calibra-tions annually unless the changes between the most recentcalibration equation values and those from the previous cali-bration do not exceed 0.1%. Calibration intervals may belengthened
21、to a maximum of 2 years provided that thesechanges do not exceed 0.1% of the value. Record the ambienttemperature during load cell calibrations. Force sensor gainvalues (or their equivalent) shall be consistent throughoutsections 7.3 and 7.4.7.2 Reference Load Calibration:7.2.1 Set up the reference
22、load cell, indicator and requiredequipment to perform the calibration. List all equipment used,including signal conditioning and output devices. Recordequipment identification and calibration dates.7.2.2 Set the bridge-excitation voltage and gain, or itsequivalent, in accordance with the instruction
23、s on the unitbeing used.7.2.3 Adjust the 9bridge zero,9 or its equivalent, to 9zero.9Be certain that the reference load cell is not being stressed.7.2.4 Using force measuring instruments or weights knownto 0.01% or better of applied force, perform a calibration on thereference load cell. Class F wei
24、ghts of 8.9N (2 lb) or greaterhave a tolerance of 0.01%. Apply the calibration forces in atleast 8 appropriately spaced increments to a maximum of notless than the anticipated maximum force seen in use. Allow allforce indicators to come to rest at each increment and recordthe force readings.7.2.5 De
25、termine bias values at each applied force.7.2.6 The biases of the reference-load cell and indicatorsystem shall be 0.25% or less of the known applied force(minimum of 62.2N(60.5lbf).7.3 Calibration of Longitudinal Force Sensor Fig. 1:Section 7.3 does not apply when the reference load cell isused as
26、the longitudinal force sensor during calibration of thebraking/tractive measuring device.7.3.1 Mount the reference-load cell such that its longitudi-nal axis is parallel to the direction of motion of the platformwithin 62 and in line with the applied force. If necessary,place a tension spring in the
27、 longitudinal force applicationsystem to allow for longitudinal motion.7.3.2 Apply sufficient force to both channels of the systemthrough the full range of expected calibration forces to exerciseto platform. Release all forces.7.3.3 Set the bridge-excitation voltage and gain, or itsequivalent, for a
28、ll instrumentation in accordance with theinstructions on the unit being used.7.3.4 Adjust the “bridge zeros,” or its equivalent, to “zero”on all instrumentation. Be certain that the reference load celland platform are not being stressed.7.3.5 Using weights known to 0.1% of applied load orbetter, app
29、ly a test load, representative of a load which will beencountered on the braking/tractive test device to be calibrated,to the top of the platform near the geometric center of the top.The platform must be maintained level within 60.25 duringcalibration. Record all force readings.NOTE 2The platform ma
30、y be sensitive to the support structure usedduring calibration. Therefore during calibration, the platform shall besupported in a manner similar to that which will subsequently be usedduring the calibration of the braking/tractive measuring device.7.3.6 Apply the longitudinal calibration force in at
31、 least 6approximately equally spaced increments to a maximum of notless than the anticipated maximum longitudinal wheel forceseen in use. Allow all force indicators to come to rest at eachincrement and record the force readings.7.3.7 Repeat 7.3.3 and 7.3.6 as necessary to collect at least12 calibrat
32、ion points.FIG. 1 Force Calibration of a Platform Force TransducerF3770327.3.8 Determine longitudinal force bias values at eachapplied force.7.3.9 The biases of the longitudinal force sensor and indi-cator system shall be 1.0 % or less of the applied force and 0.5% or less than the maximum applied f
33、orce (minimum of 0.1%of anticipated maximum braking/tractive measuring device testforce or 4.4 N (1lbf) whichever is greater).7.3.10 Determine cross talk of longitudinal force, read aspart of the vertical load at each applied longitudinal force. Thebias of the vertical load sensor and indicator syst
34、em at eachapplied longitudinal force shall be 61.0 % or less (minimum of64.4N(61lbf) of the applied vertical load.7.4 Calibration of Vertical Load Sensor:7.4.1 Level the vertical load sensor (platform with integraltransducers or appropriate scale) within 60.25.7.4.2 Set the bridge-excitation voltage
35、 and gain, or itsequivalent, for all instrumentation in accordance with theinstructions on the unit being used. Use gain values (or theirequivalent) from 7.3.3 if a two-axis platform with integraltransducers is utilized.7.4.3 Adjust the “bridge zeros,” or its equivalent, to “zero”on all instrumentat
36、ion. Be certain that the platform or scale isnot being stressed.7.4.4 Using force measuring instruments or weights knownto 0.1 % of applied load or better, apply the vertical calibrationforce to the top of the platform/scale near the geometric centerof the top in at least six approximately equally s
37、pacedincrements. The platform/scale shall be maintained levelwithin 60.25 during calibration. Begin at a load less than theminimum test load of the braking/tractive measuring deviceand continue to a load greater than or equal to the anticipatedmaximum wheel load. Allow all force indicators to come t
38、orest at each increment and record all force readings.NOTE 3The platform may be sensitive to the support structure usedduring calibration. Therefore during calibration, the platform shall besupported in a manner similar to that which will subsequently be usedduring the calibration of the braking/tra
39、ctive measuring device.7.4.5 Repeat 7.4.1 through 7.4.4 as necessary to collect atleast 12 calibration points.7.4.6 Determine vertical load bias values at each appliedforce.7.4.7 The biases of the vertical sensor and indicator systemshall be 1.0 % or less of the applied force and 0.5 % or less thant
40、he maximum applied force (minimum of 0.1% of anticipatedmaximum braking/tractive measuring device test force or 4.4 N(1lbf) whichever is greater).7.4.8 Determine cross talk of vertical load, read as part ofthe longitudinal force at each applied vertical load. The bias ofthe longitudinal force sensor
41、 and indicator system at eachapplied vertical load shall be 61.0 % or less (minimum of64.4N(61lbf) of the applied longitudinal force.8. Calibration of Braking/Tractive Force on a LockedWheel (Fig. 2, Fig. 3, or Fig. 4)8.1 Three procedures are covered: (1) for vertical calibra-tion of the test wheel
42、load cell, (2) for longitudinal drivingtractive force calibration of the test wheel load cell, and (3) aprocedure identical to (2) above except for direction of theapplied force, ie. for the longitudinal braking force calibrationof the test wheel load cell. Repeat the appropriate calibrationswhen an
43、y relevant component is changed or altered (see ASTMManual 7). At a minimum, repeat the calibrations annually.Record the ambient temperature during load cell calibrations.Force sensor gain values (or their equivalent) must be consis-tent throughout sections 8.3 and 8.4.8.2 Equipment Preparation:8.2.
44、1 Prior to starting calibration verify all reference equip-ment is in calibration in accordance with Section 6. List allequipment used, both test vehicle and reference force measure-ment, signal conditioning and output devices. Record equip-ment identification and calibration dates.8.2.2 Turn on the
45、 test vehicle system instrumentation andcalibration system instrumentation suitably in advance to allowwarm-up before attempting calibration.8.2.3 If necessary, clean the low friction bearing or airbearing plate surface to allow for free movement of theplatform.FIG. 2 Force Calibration of a Locked W
46、heelF3770338.2.4 Position the test wheel over the platform such that thetest wheel is located as near as possible to the geometric centerof the platform throughout each calibration procedure. Ifnecessary, to maintain normal vehicle orientation and toprevent movement, place blocks with a high frictio
47、n surfaceunder the other vehicle wheels so that the test wheel mountingface is perpendicular to level within 1. In the case of a trailer,the hitch point should be externally secured by a fixture or bythe tow vehicle. If the tow vehicle is used, engage the brakesand block the wheels to prevent slippa
48、ge.8.2.5 Level the platform to within 0.25 and align it laterallywithin 3 of the trailer or vehicle longitudinal axis along thecenterline of the test wheel. Maintain platform level throughoutall calibration procedures.8.3 Vertical Calibration Procedure:8.3.1 Ensure the system force sensors are not s
49、tressed bylifting the test wheel from the calibration platform. Verify thatthe test wheel is locked/unlocked from rotation as appropriateto the test device. The suspension may be further unloaded bytapping the test wheel with a mallet. Adjust the zeros/gains ofall systems.8.3.2 Start the data-logging device and lower the test wheelonto the platform. Increase the load in no less than fourincrements until the full weight (not less than the anticipatedmaximum test load) has been placed on the platform. Allow allforce indicators to stabilize at each increment. Ma
