1、Designation:E408American Association StateHighway and Transportation Officials StandardsAASHTO No: T67Standard Practices forForce Verification of Testing Machines1This standard is issued under the fixed designation E 4; the number immediately following the designation indicates the year of originala
2、doption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A superscriptepsilon () indicates an editorial change since the last revision or reapproval.This standard has been approved for use by agencies of the Department of Defense.
3、1. Scope1.1 These practices cover procedures for the force verifica-tion, by means of standard calibration devices, of tension orcompression, or both, static or quasi-static testing machines(which may, or may not, have force-indicating systems). Thesepractices are not intended to be complete purchas
4、e specifica-tions for testing machines. Testing machines may be verified byone of the three following methods or combination thereof:1.1.1 Use of standard weights,1.1.2 Use of equal-arm balances and standard weights, or1.1.3 Use of elastic calibration devices.NOTE 1These practices do not cover the v
5、erification of all types oftesting machines designed to measure forces, for example, the constant-rate-of-loading type which operates on the inclined-plane principle. Thistype of machine may be verified as directed in the applicable appendix ofSpecification D76.1.2 The procedures of 1.1.1-1.1.3 appl
6、y to the verification ofthe force-indicating systems associated with the testing ma-chine, such as a scale, dial, marked or unmarked recorder chart,digital display, etc. In all cases the buyer/owner/user mustdesignate the force-indicating system(s) to be verified andincluded in the report.1.3 Since
7、conversion factors are not required in this prac-tice, either inch-pound units, SI units, or metric values can beused as the standard.1.4 Forces indicated on displays/printouts of testing ma-chine data systemsbe they instantaneous, delayed, stored, orretransmittedwhich are verified with provisions o
8、f 1.1.1,1.1.2,or1.1.3, and are within the 61 % accuracy requirement,comply with Practices E 4.1.5 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 pra
9、ctices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D76 Specification for Tensile Testing Machines for TextilesE74 Practice of Calibration of Force-Measuring Instru-ments for Verifying the Force Indication of Testing Ma-chinesE 46
10、7 Practice for Verification of Constant Amplitude Dy-namic Forces in an Axial Fatigue Testing System3. Terminology3.1 Definitions:3.1.1 testing machine (force-measuring type)a mechani-cal device for applying a force to a specimen.3.1.1.1 portable testing machine (force-measuring type)adevice specifi
11、cally designed to be moved from place to placeand for applying a force (load) to a specimen.3.1.2 forcein the case of testing machines, a force mea-sured in units such as pound-force, newton, or kilogram-force.3.1.2.1 DiscussionThe pound-force is that force whichacting on a 1-lb mass will give to it
12、 an acceleration of 9.80665m/s2(32.1740 ft/s2). The newton is that force which acting ona 1-kg mass will give to it an acceleration of 1 m/s2.3.1.3 accuracythe specified permissible variation fromthe reference value.3.1.3.1 DiscussionAtesting machine is said to be accurateif the indicated force is w
13、ithin the specified permissiblevariation from the actual force. 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 accuracy of a testingmachine should not be confused with sen
14、sitivity. For example,a testing machine might be very sensitive; that is, it might1These practices are under the jurisdiction of ASTM Committee E28 onMechanical Testing and is the direct responsibility of Subcommittee E28.01 onCalibration of Mechanical Testing Machines and Apparatus.Current edition
15、approved Dec. 1, 2008. Published January 2009. Originallyapproved in 1923. Last previous edition approved in 2007 as E407.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, ref
16、er to the standards Document Summary page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.indicate quickly and definitely small changes in force, butnevertheless, be very inaccurate. On the other hand, theaccuracy
17、of the results is in general limited by the sensitivity.3.1.4 error (or the deviation from the correct value)in thecase of a testing machine, the difference obtained by subtract-ing the force indicated by the calibration device from the forceindicated by the testing machine.3.1.4.1 DiscussionThe wor
18、d “error” shall be used withnumerical values, for example, “At a force of 30 000 lbf (133kN), the error of the testing machine was + 15 lbf (67 N).”3.1.5 percent errorin the case of a testing machine, theratio, expressed as a percent, of the error to the correct value ofthe applied force.3.1.5.1 Dis
19、cussionThe test force, as indicated by thetesting machine, and the applied force, as computed from thereadings of the verification device, shall be recorded at eachtest point. The error, E, and the percent error, Ep, shall becalculated from these data as follows:E 5 A 2 B (1)Ep5 A 2 B!/B 3 100where:
20、A = force indicated by machine being verified, lbf (or N),andB = correct value of the applied force, lbf (or N), asdetermined by the calibration device.3.1.6 correctionin the case of a testing machine, thedifference obtained by subtracting the indicated force from thecorrect value of the applied for
21、ce.3.1.7 permissible variation (or tolerance)in the case oftesting machines, the maximum allowable error in the value ofthe quantity indicated.3.1.7.1 DiscussionIt is convenient to express permissiblevariation in terms of percentage of error. The numerical valueof the permissible variation for a tes
22、ting machine is so statedhereafter in these practices.3.1.8 capacity rangein the case of testing machines, therange of forces for which it is designed. Some testing machineshave more than one capacity range, that is, multiple ranges.3.1.9 verified range of forcesin the case of testing ma-chines, the
23、 range of indicated forces for which the testingmachine gives results within the permissible variations speci-fied.3.1.9.1 calibration, nin the case of force testing machines,the process of comparing the force indication of the machineunder test to that of a standard, making adjustments as neededto
24、meet error requirements.3.1.9.2 verification, nin the case of force testing ma-chines, the process of comparing the force indication of themachine under test to that of a standard and reporting results,without making adjustments.3.1.10 elastic calibration devicea device for use in veri-fying the for
25、ce readings of a testing machine consisting of anelastic member(s) to which forces may be applied, combinedwith a mechanism or device for indicating the magnitude (or aquantity proportional to the magnitude) of deformation underforce.3.1.11 resolution of the force indicatorsmallest change offorce th
26、at can be estimated or ascertained on the forceindicating apparatus of the testing machine, at any appliedforce. Appendix X1. describes a method for determiningresolution.3.1.11.1 resolution of analog type force indicators (scales,dials, recorders, etc.)the resolution is the smallest change inforce
27、indicated by a displacement of a pointer, or pen line. Theresolution is calculated by multiplying the force correspondingto one graduation by the ratio of the width of the pointer or penline to the center to center distance between two adjacentgraduation marks. The typical ratios used are 1:1, 1:2,
28、1:5, or1:10.Aspacing of 0.10 in. (2.5 mm) or greater is recommendedfor the ratio of 1:10. A ratio less than 1:10 should not be used.(1) DiscussionIf a force indicating dial has graduationsspaced every 0.080 in. (2.0 mm), the width of the pointer isapproximately 0.040 in. (1.0 mm), and one graduation
29、 repre-sent 5 lbf (25N). The ratio used would be 1:2 and the resolutionwould be equal to 2-1/2 lbf (12-1/2 N).3.1.11.2 resolution of digital type force indicators (numeric,displays, printouts, etc.)the resolution is the smallest changein force that can be displayed on the force indicator, at anyappl
30、ied force.(1) DiscussionA single digit or a combination of digitsmay be the smallest change in force that can be indicated.3.1.12 If the force indication, for either type of forceindicator, fluctuates by more than twice the resolution, asdescribed in 3.1.11.1 or 3.1.11.2, the resolution, expressed a
31、s aforce, shall be equal to one-half the range of the fluctuation.4. Significance and Use4.1 Testing machines that apply and indicate force 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
32、for shipment. No matterwhat the end use of the machine may be, it is necessary forusers to know the amount of force that is applied and indicated,and that the accuracy of the force is traceable to the NationalInstitute of Standards and Technology (NIST), formerly NBS.Practices E 4 provides a procedu
33、re to verify these machines, inorder that the indicated forces may be traceable. A key elementto this NIST traceability is that the devices used in theverification have known force characteristics, and have beencalibrated in accordance with Practice E74.4.2 The procedures in Practices E 4 may be use
34、d by thoseusing, manufacturing, and providing calibration service fortesting machines and related instrumentation.5. Calibration Devices5.1 When verifying testing machines, use calibration de-vices only over their Class A force ranges as determined byPractice E74.6. Advantages and Limitations of Met
35、hods6.1 Verification by Standard WeightsVerification by thedirect application of standard weights to the weighing mecha-nism of the testing machine, where practicable, is the mostaccurate method. Its limitations are: (1) the small range ofE4082forces that can be verified, (2) the nonportability of a
36、ny largeamount of standards weights, and (3) its nonapplicability tohorizontal testing machines or vertical testing machines havingweighing mechanisms that are not designed to be actuated bya downward force.6.2 Verification by Equal-Arm Balance and StandardWeightsThe second method of verification of
37、 testing ma-chines involves measurement of the force by means of anequal-arm balance and standard weights. This method islimited to a still smaller range of forces than the foregoingmethod, and is generally applicable only to certain types ofhardness testing machines in which the force is applied th
38、roughan internal lever system.6.3 Verification by Elastic Calibration DevicesThe thirdmethod of verification of testing machines involves measure-ment of the elastic strain or deflection under force of a ring,loop, tension or compression bar, or other elastic device. Theelastic calibration device is
39、 free from the limitations referred toin 6.1 and 6.2.7. System Verification7.1 A testing machine shall be verified as a system with theforce sensing and indicating devices (see 1.2 and 1.4) in placeand operating as in actual use.7.1.1 If this is not technically possible, refer to Annex A1,Verifying
40、the Force Measuring System out of the Test Machine.Out of the test machine verifications shall be in accordancewith the main body of Practices E 4 and its Annex A17.2 System verification is invalid if the devices are removedand checked independently of the testing machine unlessverification is perfo
41、rmed according to Annex A1.7.3 Many testing machines utilize more than one forcemeasuring device in order to obtain more accurate forceindication at lower applied forces. These devices are routinelyinstalled and uninstalled in the testing machine. For suchdevices, interchangeability shall be establi
42、shed during theoriginal verification and shall be reestablished after an adjust-ment is performed. This is accomplished by performing anormal verification with the device in place as during normaluse. It is advisable that orientation be kept consistent, such asby noting the direction of the cable co
43、nnector so that whenreinstalling the device, the orientation will be repeated. Re-move and reinstall the device between the two verification runsto demonstrate interchangeability. Repeat the procedure foreach interchangeable force measuring device used in thetesting machine.7.3.1 Introduction of the
44、 new force measuring devices shallrequire that interchangeability be established per 7.3.7.4 A Practices E 4 Verification consists of at least twoverification runs of the forces contained in the force range(s)selected. See 10.1 and 10.3.7.4.1 If the initial verification run produces values withinthe
45、 Practices E 4 requirements of Section 17, the data may beused “as found” for run one of the two required for the newverification report.7.4.2 If the initial verification run produces any valueswhich are outside of the Practices E 4 requirements, the “asfound” data may be reported and may be used in
46、 accordancewith applicable quality control programs. Calibration adjust-ments shall be made to the force indicator system(s), afterwhich the two required verification runs shall be conducted andreported in the new verification report and certificate.7.4.3 Calibration adjustments may be made to impro
47、ve theaccuracy of the system. They shall be followed by the tworequired verification runs, and issuance of a new verificationreport and certificate.8. Gravity and Air Buoyancy Corrections8.1 In the verification of testing machines, where standardweights are used for applying forces directly or throu
48、gh leveror balance-arm systems, correct the force for the local value ofgravity and for air buoyancy.8.2 Calculate the force exerted by a weight in air as follows:Force 5Mg9.80665S1 2dDD(2)where:M = mass of the weight,g = local acceleration due to gravity, m/s2,d = air density (0.0012 Mg/m3), andD =
49、 density of the weight in the same units as d.For use in verifying testing machines, corrections for localvalues of gravity and air buoyancy can be made with sufficientaccuracy using the multiplying factors from Table 1.NOTE 2If M, the mass of the weight is in pounds, the force will be inpounds-force units. If M is in kilograms, the force will be in kilogram-force units. These customary force units are related to the newton, the SIunit of force, by the following relationships:1 lbf 5 4.448222 N1 kgf 5 9.80665 N exact! (3)9. Application of Force9.1 In t
