1、Designation: E 2624 09Standard Practice forTorque Calibration of Testing Machines and Devices1This standard is issued under the fixed designation E 2624; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A
2、number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This practice covers procedures and requirements forthe calibration of torque for static and quasi-static torquecapable testing machine
3、s or devices. These may, or may not,have torque indicating systems and include those devices usedfor the calibration of hand torque tools. Testing machines maybe calibrated by one of the three following methods orcombination thereof:1.1.1 Use of standard weights and lever arms.1.1.2 Use of elastic t
4、orque measuring devices.1.1.3 Use of elastic force measuring devices and lever arms.1.1.4 Any of the methods require a specific uncertainty ofmeasurement and a traceability derived from national standardsof mass and length.1.2 The procedures of 1.1.1, 1.1.2, and 1.1.3 apply to thecalibration of the
5、torque-indicating systems associated with thetesting machine, such as a scale, dial, marked or unmarkedrecorder chart, digital display, etc. In all cases the buyer/owner/user must designate the torque-indicating system(s) to becalibrated and included in the report.1.3 Since conversion factors are no
6、t required in this prac-tice, either english units, metric units, or SI units can be usedas the standard.1.4 Torque values indicated on displays/printouts of testingmachine data systemsbe they instantaneous, delayed, stored,or retransmittedwhich are Calibrated with provisions of1.1.1, 1.1.2 or 1.1.3
7、 or a combination thereof, and are withinthe 61 % of reading accuracy requirement, comply with thispractice.1.5 The following applies to all specified limits in thisstandard: For purposes of determining conformance with thesespecifications, an observed value or a calculated value shall berounded “to
8、 the nearest unit” in the last right-hand digit used inexpressing the specification limit, in accordance with therounding method of Practice E29, for Using Significant Digitsin Test Data to Determine Conformance with Specifications.1.6 This standard does not purport to address all of thesafety conce
9、rns, 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 limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2E6 Terminology Relating to Methods of Me
10、chanical Test-ingE29 Practice for Using Significant Digits in Test Data toDetermine Conformance with SpecificationsE74 Practice of Calibration of Force-Measuring Instru-ments for Verifying the Force Indication of Testing Ma-chinesE 2428 Practice for Calibration of Torque-Measuring In-struments for V
11、erifying the Torque Indication of TorqueTesting Machines2.2 NIST Technical Notes:NIST Technical Note 1297 Guidelines for Evaluating andExpressing the Uncertainty of NIST Measurement Re-sults33. Terminology3.1 Definitions:3.1.1 accuracyaccuracy is defined in Terminology E6.3.1.1.1 DiscussionAtesting
12、machine is said to be accurateif the indicated torque is within the specified permissiblevariation from the actual torque in these methods the word“accurate” applied to a testing machine is used withoutnumerical values, for example, “An accurate testing machinewas used for the investigation.” The ac
13、curacy of a testingmachine should not be confused with sensitivity. For example,a testing machine might be very sensitive; that is, it mightindicate quickly and definitely small changes in torque, butnevertheless, be very inaccurate. On the other hand, theaccuracy of the results is in general limite
14、d by the sensitivity.3.1.2 calibrated range of torquein the case of testingmachines, the range of indicated torque for which the testingmachine gives results within the permissible variations speci-fied.1This practice is under the jurisdiction of ASTM Committee E28 on MechanicalTesting and is the di
15、rect responsibility of Subcommittee E28.01 on Calibration ofMechanical Testing Machines and Apparatus.Current edition approved April 1, 2009. Published May 2009.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book o
16、f ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3Available from National Institute of Standards and Technology (NIST), 100Bureau Dr., Stop 1070, Gaithersburg, MD 20899-1070, http:/www.nist.gov.1Copyright ASTM International, 100 Barr Harbor Drive, P
17、O Box C700, West Conshohocken, PA 19428-2959, United States.3.1.3 calibration torquea torque with traceability derivedfrom national standards of mass and length and of specificuncertainty of measurement, which can be applied to torquemeasuring devices.3.1.4 capacity rangein the case of testing machi
18、nes, therange of torque for which it is designed. Some testing machineshave more than one capacity range, that is, multiple ranges.3.1.5 correctionin the case of testing machines, thedifference obtained by subtracting the indicated torque fromthe reference value of the applied torque.3.1.6 elastic t
19、orque-measuring devicea device or systemconsisting of an elastic member combined with a device forindicating the measured values (or a quantity proportional tothe measured value) of deformation of the member under anapplied torque.NOTE 1The instrumentation for the elastic devices may be either anele
20、ctrical or a mechanical device, i.e., a scale or pointer system.3.1.7 error (or the deviation from the reference value)inthe case of a testing machine or device, the difference obtainedby subtracting the torque indicated by the calibration devicefrom the torque indicated by the testing machine or de
21、vice.3.1.7.1 DiscussionThe word “error” shall be used withnumerical values, for example, “At a torque of 3000 lbf-in., theerror of the testing machine was +10 lbf-in.”3.1.8 expanded uncertaintya statistical measurement ofthe probable limits of error of a measurement. NIST TechnicalNote 1297 treats t
22、he statistical approach including the ex-panded uncertainty.3.1.9 lower torque limit of calibration rangethe lowestvalue of torque at which a torque measuring system can becalibrated.3.1.10 parasitic torquetorque that bypasses a desiredtorque path that can cause errors in determining the value of th
23、etorque in that path. It is usually caused by cables, conduit, orhydraulic lines attached to objects that are in the torque path.These attachments absorb torque and cause subsequent errorsin the measured torque.3.1.11 percent errorin the case of a testing machine ordevice, the ratio, expressed as a
24、percent, of the error to thereference value of the applied torque.3.1.11.1 DiscussionThe test torque, as indicated by thetesting machine, and the applied torque, as computed from thereadings of the calibration device, shall be recorded at each testpoint. The error, E, and the percent error, Ep, shal
25、l be calculatedfrom this data as follows:E 5 A B (1)Ep5 A B!/B! 3 100where:A = torque indicated by the machine being calibrated, N-m(lbf-in.), andB = reference value of the applied torque, N-m (lbf-in.), asdetermined by the calibration device.3.1.12 permissible variation (or tolerance)in the case of
26、testing machines, the maximum allowable error in the value ofthe quantity indicated.3.1.12.1 DiscussionIt is convenient to express permis-sible variation in terms of percentage of error. The numericalvalue of the permissible variation for a testing machine is sostated hereafter in these practices.3.
27、1.13 reference standarda standard used to generate or tomeasure torque applied to the testing machine to be calibrated.NOTE 2Torque may be generated by a length calibrated arm andcalibrated masses used to produce known torque. Alternatively, torqueapplied to a torque measuring device to be calibrate
28、d may be measured bythe use of a reference torque measurement device, i.e., an elastic torquecalibration device, or a length calibrated arm and an elastic forcemeasuring device.3.1.14 resolution of analog type torque indicators (scales,dials, recorders, etc.)the resolution is the smallest change int
29、orque indicated by a displacement of a pointer, or pen line.The resolution is calculated by multiplying the torque corre-sponding to one graduation by the ratio of the width of thepointer or pen line to the center to center distance between twoadjacent graduation marks.3.1.15 resolution of digital t
30、ype torque indicators (numeric,displays, printouts, etc.)the resolution is the smallest changein torque that can be displayed on the digital torque indicator,at any applied torque. Appendix X1 describes a method fordetermining resolution.3.1.15.1 DiscussionIf the torque indication, for eithertype of
31、 torque indicator, fluctuates by more than twice theresolution, as described in 3.1.15 or 3.1.16, the resolution,expressed as torque, shall be equal to one-half the range of thefluctuation.3.1.16 resolution of the torque indicatorsmallest changeof torque that can be estimated or ascertained on the t
32、orqueindicating apparatus of the testing machine or device, at anyapplied torque. Appendix X1 describes a method for determin-ing resolution.3.1.17 torquevector product of force and length, ex-pressed in terms of N-m, lbf-in., etc.3.1.18 torque capable testing machinea testing machineor device that
33、has provision for applying a torque to aspecimen.4. Significance and Use4.1 Testing machines that apply and indicate torque are usedin many industries, in many ways. They may be used in aresearch laboratory to measure material properties, and in aproduction line to qualify a product for shipment. No
34、 matterwhat the end use of the machine may be, it is necessary forusers to know the amount of torque that is applied, and that theaccuracy of the torque value is traceable to the NationalStandards. This standard provides a procedure to verify thesemachines and devices, in order that the indicated to
35、rque valuesmay be traceable. A key element to having traceability is thatthe devices used in the calibration produce known torquecharacteristics, and have been calibrated in accordance withPractice E 2428.4.2 This standard may be used by those using, thosemanufacturing, and those providing calibrati
36、on service fortorque capable testing machines or devices and related instru-mentation.E26240925. Calibration Devices5.1 Calibration by Standard Weights and Lever ArmsCalibration by the application of standard weights using a leverarm to the torque sensing mechanism of the testing machine,where pract
37、icable, is the most accurate method. Its limitationsare: (1) the small range of torque that can be calibrated, (2) thenon-portability of any high capacity standard weights and (3)analysis of all parasitic torque components.5.2 Calibration by Elastic Calibration DevicesThe sec-ond method of calibrati
38、on of testing machines involves mea-surement of the elastic strain or rotation under the torque of atorque transducer or a force transducer/lever arm combination.The elastic calibration devices are less constrained than thestandards referenced in 5.1. The design of fixtures and inter-faces between t
39、he calibration device and the machine arecritical. When using elastic torque or force measuring devices,use the devices only over their Class A loading ranges asdetermined by Practice E 2428 for elastic torque measuringdevices or Practice E74for elastic force measuring devices.6. Requirements for To
40、rque Standards6.1 Weights and Lever ArmsWeights and lever arms withtraceability derived from national standards of mass, force,length and of specific measurement uncertainty may be used toapply torque to testing machines. Weights used as forcestandards shall be made of rolled, forged, or cast metal.
41、 Theexpanded uncertainty, with a confidence factor of 95% (k=2),for the weight values shall not exceed 0.1 %.6.1.1 The force exerted by a weight in air is calculated asfollows:Force 5 Mg / 9.80665! 1d / D! (2)where:M = mass of the weight,g = local acceleration due to gravity, m/s2,d = air density (a
42、pproximately 0.0012 Mg/m3),D = density of the weight in the same units as d(Note 3), and9.80665 = the factor converting SI units of force into thecustomary units of force. For SI units, this factoris not used.6.1.2 The masses of the weights shall be determined bycomparison with reference standards t
43、raceable to the nationalstandards of mass. Corrections for the local value of theacceleration due to gravity can be made with sufficient accu-racy by using the multiplying factors from Table 1.NOTE 3If M, the mass of the weight, is in pounds, the force will bein pound-force units (lbf). If M is in k
44、ilograms, the force will be inkilogram-force units (kgf). These customary force units are related to thenewton (N), the SI unit of force, by the following relationships:1 kgf = 9.80665 N (exact)1 lbf = 4.44822 N6.1.3 The lever arm or wheel shall be calibrated to deter-mine the length or radius withi
45、n a known uncertainty, that istraceable to national standards of length. The expanded uncer-tainty, with a confidence factor of 95% (k=2), for the measuredlength of the calibration lever arm shall not exceed 0.1 %.6.2 Elastic torque-measuring instruments may be used assecondary standards and shall b
46、e calibrated by primary stan-dards. Practice E 2428 defines the calibration of elastic torque-measuring instruments. Practice E74defines the calibration ofelastic force-measuring instruments.7. Selection of Applied Torques7.1 Determine the upper and lower limits of the torquerange of the testing mac
47、hine to be calibrated. In no case shallthe calibrated torque range include torques below 200 times theresolution of the torque indicator.7.2 If the lower limit of the torque range is greater or equalto one-tenth the upper limit, calibrate the testing machine byapplying at least five test torque valu
48、es, at least two times, withthe difference between any two successive torque value appli-cations being no larger than one-third the difference betweenthe selected maximum and minimum test torque values.Minimum torque values may be one-tenth the maximum torquevalues. Applied torque values on the seco
49、nd run are to beapproximately the same as those on the first run. Report allvalues, including the indicator reading, after removal oftorques. Include indicator resolution for the minimum torquevalue.NOTE 4When calibration is done using lever arms and weights, thecombination of standard weights and lever arms may not exactly corre-spond to the desired upper and lower torques to be applied to the testingmachine. In this case torque values that differ from the desired value by62.5 % are acceptable.7.3 When the lower limit of a calibrated torque
