1、Designation: E2624 15E2624 17Standard Practice forTorque Calibration of Testing Machines1This standard is issued under the fixed designation E2624; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A number
2、 in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope Scope*1.1 This practice covers procedures and requirements for the calibration of torque for static and quasi-static torque capabletesting machi
3、nes. These may, or may not, have torque indicating systems and include those devices used for the calibration of handtorque tools. Testing machines may be calibrated by one of the three following methods or combination thereof:1.1.1 Use of standard weights and lever arms.1.1.2 Use of elastic torque
4、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 of measurement, displaying metrological traceability to TheInternational System of Units (SI).NOTE 1 for further definition of the term metrological traceability, ref
5、er to the latest revision of JCGM 200: International vocabulary of metrology Basic and general concepts and associated terms (VIM).1.2 The procedures of 1.1.1, 1.1.2, and 1.1.3 apply to the calibration of the torque-indicating systems associated with the testingmachine, such as a scale, dial, marked
6、 or unmarked recorder chart, digital display, etc. In all cases the buyer/owner/user mustdesignate the torque-indicating system(s) to be calibrated and included in the report.1.3 Since conversion factors are not required in this practice, either english units, metric units, or SI units can be used a
7、s thestandard.1.4 Torque values indicated on displays/printouts of testing machine data systemsbe they instantaneous, delayed, stored, orretransmittedwhich are calibrated with provisions of 1.1.1, 1.1.2 or 1.1.3 or a combination thereof, and are within the 61 % ofreading accuracy requirement, comply
8、 with this practice.1.5 The following applies to all specified limits in this standard: For purposes of determining conformance with thesespecifications, an observed value or a calculated value shall be rounded “to the nearest unit” in the last right-hand digit used inexpressing the specification li
9、mit, in accordance with the rounding method of Practice E29, for Using Significant Digits in TestData to Determine Conformance with Specifications.1.6 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibilityof the user of this st
10、andard to establish appropriate safety safety, health, and healthenvironmental practices and determine theapplicability of regulatory limitations prior to use.1.7 This international standard was developed in accordance with internationally recognized principles on standardizationestablished in the D
11、ecision on Principles for the Development of International Standards, Guides and Recommendations issuedby the World Trade Organization Technical Barriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:2E6 Terminology Relating to Methods of Mechanical TestingE29 Practice for Using
12、 Significant Digits in Test Data to Determine Conformance with SpecificationsE74 Practice of Calibration of Force-Measuring Instruments for Verifying the Force Indication of Testing MachinesE2428 Practice for Calibration and Verification of Torque Transducers1 This practice is under the jurisdiction
13、 of ASTM Committee E28 on Mechanical Testing and is the direct responsibility of Subcommittee E28.01 on Calibration ofMechanical Testing Machines and Apparatus.Current edition approved Dec. 1, 2015Sept. 1, 2017. Published January 2016November 2017. Originally approved in 2009. Last previous edition
14、approved in 20092015as E2624 09. 15. DOI: 10.1520/E2624-15.10.1520/E2624-17.2 For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume information, refer to the standards Document Summary page on th
15、e ASTM website.This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Becauseit may not be technically possible to adequately depict all changes accurately, ASTM recommends that users co
16、nsult prior editions as appropriate. In all cases only the current versionof the standard as published by ASTM is to be considered the official document.*A Summary of Changes section appears at the end of this standardCopyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocke
17、n, PA 19428-2959. United States12.2 NIST Technical Notes:NIST Technical Note 1297 Guidelines for Evaluating and Expressing the Uncertainty of NIST Measurement Results32.3 BIPM Standard:4JCGM 200 : International vocabulary of metrology Basic and general concepts and associated terms (VIM)3. Terminolo
18、gy3.1 Definitions: In addition to the terms listed, see Terminology E6.3.1.1 accuracythe permissible variation from the correct value.3.1.1.1 DiscussionA testing machine is said to be accurate if the indicated torque is within the specified permissible variation from the actual torque.In this practi
19、ce the word “accurate” applied to a testing machine is used without numerical values. For example, “An accuratetesting machine was used for the investigation.” The accuracy of a testing machine should not be confused with sensitivity. Forexample, a testing machine might be very sensitive; that is, i
20、t might indicate quickly and definitely small changes in torque, butnevertheless, be very inaccurate. On the other hand, the accuracy of the results is in general limited by the sensitivity.3.1.2 error, nfor a measurement or reading, the amount it deviates from a known or reference value represented
21、 by ameasurement standard. Mathematically, the error is calculated by subtracting the accepted value from the measurement or reading.3.1.2.1 DiscussionThe word “error” shall be used with numerical values, for example, “At a torque of 3000 lbfin., the error of the testing machinewas +10 lbfin.”3.1.3
22、percent error, nin the case of a testing machine or device, the ratio, expressed as a percent, of an error to the knownaccepted value represented by a measurement standard.3.1.4 reference standard, nan item, typically a material or an instrument, that has been characterized by recognized standardsor
23、 testing laboratories, for some of its physical or mechanical properties, and that is generally used for calibration or verification,or both, of a measurement system or for evaluating a test method.3.1.4.1 DiscussionTorque may be generated by a length calibrated arm and calibrated masses used to pro
24、duce known torque. Alternatively, torqueapplied to a torque measuring device to be calibrated may be measured by the use of a reference torque measurement device, thatis, an elastic torque calibration device, or a length calibrated arm and an elastic force measuring device.3.1.5 resolution, nfor a p
25、articular measurement device, the smallest change in the quantity being measured that causes aperceptible change in the corresponding indication.3.1.5.1 DiscussionResolution may depend on the value (magnitude) of the quantity being measured.3.1.5.2 DiscussionFor paper charts or analog indicators, th
26、e resolution should not be assumed to be better (smaller) than 110 of the spacing betweengraduations. For digital devices, the best resolution potentially achievable is the smallest difference between two different readingsgiven by the display.3.1.5.3 DiscussionFor both analog and digital devices, t
27、he actual resolution can be significantly poorer than described above, due to factors such asnoise, friction, etc.3.1.6 torque, na moment (of forces) that produces or tends to produce rotation or torsion.3 Available from National Institute of Standards and Technology (NIST), 100 Bureau Dr., Stop 107
28、0, Gaithersburg, MD 20899-1070, http:/www.nist.gov.4 Available from BIPM (Bureau International des Poids et Mesures)- Pavillon de Breteuil F-92312 Svres Cedex FRANCE http:/www.bipm.orgE2624 1723.2 Definitions of Terms Specific to This Standard:3.2.1 calibrated range of torquein the case of testing m
29、achines, the range of indicated torque for which the testing machinegives results within the permissible variations specified.3.2.2 calibration torquea torque with metrological traceability derived from standards of mass and length and of specificuncertainty of measurement, which can be applied to t
30、orque measuring devices.3.2.3 capacity rangein the case of testing machines, the range of torque for which it is designed.3.2.3.1 DiscussionSome testing machines have more than one capacity range, that is, multiple ranges.3.2.4 correctionin the case of testing machines, the difference obtained by su
31、btracting the indicated torque from the referencevalue of the applied torque.3.2.5 elastic torque-measuring devicea device or system consisting of an elastic member combined with a device forindicating the measured values (or a quantity proportional to the measured value) of deformation of the membe
32、r under an appliedtorque.3.2.5.1 DiscussionThe instrumentation for the elastic devices may be either an electrical or a mechanical device, that is, a scale or pointer system.3.2.6 expanded uncertaintya statistical measurement of the probable limits of error of a measurement, NIST Technical Note1297
33、treats the statistical approach including the expanded uncertainty.3.2.7 lower torque limit of calibration rangethe lowest value of torque at which a torque measuring system can be calibrated.3.2.8 parasitic torqueForces that bypass the torque axis and can cause errors in determining the value of th
34、e torque.3.2.8.1 DiscussionUsually the result of off axis loading (bending moments) caused by cables, conduit, or hydraulic lines attached to objects that arein the torque path and cause subsequent errors in the measured torque.3.2.9 permissible variation (or tolerance) in the case of testing machin
35、es, the maximum allowable error in the value of thequantity indicated.3.2.9.1 DiscussionIt is convenient to express permissible variation in terms of percentage of error. The numerical value of the permissible variationfor a testing machine is so stated hereafter in these practices.3.2.10 torque-cap
36、able testing machinea testing machine or device that has provision for applying a torque to a specimen.4. Significance and Use4.1 Testing machines that apply and indicate torque are used in many industries, in many ways. They may be used in a researchlaboratory to measure material properties, and in
37、 a production line to qualify a product for shipment. No matter what the end useof the machine may be, it is necessary for users to know the amount of torque that is applied, and that the accuracy of the torquevalue is traceable to the SI. This standard provides a procedure to verify these machines
38、and devices, in order that the indicatedtorque values may be traceable.Akey element to having metrological traceability is that the devices used in the calibration produceknown torque characteristics, and have been calibrated in accordance with Practice E2428.4.2 This standard may be used by those u
39、sing, those manufacturing, and those providing calibration service for torque capabletesting machines or devices and related instrumentation.5. Calibration Devices5.1 Calibration by Standard Weights and Lever ArmsCalibration by the application of standard weights using a lever arm tothe torque sensi
40、ng mechanism of the testing machine, where practicable, is the most accurate method. Its limitations are: (1) thesmall range of torque that can be calibrated, (2) the non-portability of any high capacity standard weights and (3) analysis of allparasitic torque components.5.2 Calibration by Elastic C
41、alibration DevicesThe second method of calibration of testing machines involves measurementof the elastic strain or rotation under the torque of a torque transducer or a force transducer/lever arm combination. The elasticE2624 173calibration devices are less constrained than the standards referenced
42、 in 5.1. The design of fixtures and interfaces between thecalibration device and the machine are critical. When using elastic torque or force measuring devices, use the devices only overtheir ClassAloading ranges as determined by Practice E2428 for elastic torque measuring devices or Practice E74 fo
43、r elastic forcemeasuring devices.6. Requirements for Torque Standards6.1 Weights and Lever ArmsWeights and lever arms with traceability derived from standards of mass, force, length and ofspecific measurement uncertainty may be used to apply torque to testing machines. Weights used as force standard
44、s shall be madeof rolled, forged, or cast metal. The expanded uncertainty, with a confidence factor of 95% (k=2), for the weight values shall notexceed 0.1 %.6.1.1 The force exerted by a mass in air is determined by:F 5Mg S1 2 dDD (1)where:F = force, NM = true mass of the weight, kgg = local acceler
45、ation due to gravity, m/s2,d = air density (1.2 kg/m3), andD = density of the weight in the same units as dNOTE 2Neglecting air buoyancy can cause errors on the order of 0.01% to 0.05% depending on the metal the weight is fabricated from. If it isneglected, it should be considered in any uncertainty
46、 analysis.6.1.2 For the purposes of this standard, g can be calculated with a sufficient uncertainty using the following formula.g 59.7803110.0053sin !2#20.000001967h (2)where: = latitudeh = elevation above sea level in meters.NOTE 3Formula 2 corrects for the shape of the earth and elevation above s
47、ea level. The correction for the shape of the earth is a simplification ofthe World Geodetic System 84 Ellipsoidal Gravity Formula. The results obtained with the simplified formula differ by less than 0.0005%. The term thatcorrects for altitude, corrects for an increased distance from the center of
48、the earth and the counter-acting Bouguer effect of localized increased mass ofthe earth. The formula assumes a rock density of 2.67 g/cc. If the rock density changed by 0.5 g/cc, an error of 0.003 % would result.6.2 The force in customary units exerted by a weight in air is calculated as follows:Fc
49、5 Mg9.80665S1 2 dDD (3)where:Fc = force expressed in customary units, that is, pound force or kilogram forceM = true mass of the weightg = Local acceleration due to gravity, m/s2d = air density (1. 2 kg/m3)D = density of the weight in the same units as d, and9.80665 = The factor converting SI units of force into customary units of force; this factor is equal to the value of standardgravity. 9.80665 m/s2NOTE 4If M, the mass of the weight is in pounds, the force will be in pound-force units (lbf). If M is in kilograms, the force wi
