1、Designation: E4 14 American Association StateHighway and Transportation Officials StandardsAASHTO No: T67Standard Practices forForce Verification of Testing Machines1This standard is issued under the fixed designation E4; the number immediately following the designation indicates the year of origina
2、ladoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.Asuperscriptepsilon () indicates an editorial change since the last revision or reapproval.This standard has been approved for use by agencies of the U.S. Department of Defen
3、se.1. Scope*1.1 These practices cover procedures for the forceverification, by means of standard calibration devices, oftension or compression, or both, static or quasi-static testingmachines (which may, or may not, have force-indicatingsystems). These practices are not intended to be completepurcha
4、se specifications for testing machines. Testing machinesmay be verified by one of the three following methods orcombination 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 ve
5、rification 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 apply
6、 to the verificationof the force-indicating systems associated with the testingmachine, such as a scale, dial, marked or unmarked recorderchart, digital display, etc. In all cases the buyer/owner/usermust designate the force-indicating system(s) to be verified andincluded in the report.1.3 The value
7、s stated in inch-pound units are to be regardedas standard. The values given in parentheses are mathematicalconversions to SI units that are provided for information onlyand are not considered standard.1.3.1 Since conversion factors are not required in thispractice, either inch-pound units, SI units
8、, or metric values canbe used 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 of 1.1.1,1.1.2,or1.1.3, and are within the 61 % accuracy requirement,comply with Practice
9、s E4.1.5 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 practices and determine the applica-bility of regulatory limitations prior to use.2. Referen
10、ced Documents2.1 ASTM Standards:2D76 Specification for Tensile Testing Machines for TextilesE74 Practice of Calibration of Force-Measuring Instrumentsfor Verifying the Force Indication of Testing MachinesE467 Practice for Verification of Constant Amplitude Dy-namic Forces in an Axial Fatigue Testing
11、 System3. Terminology3.1 Definitions:3.1.1 accuracythe specified permissible variation fromthe reference value.3.1.1.1 DiscussionAtesting machine is said to be accurateif the indicated force is within the specified permissiblevariation from the actual force. In these methods the word“accurate” appli
12、ed 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 sensitivity. For example,a testing machine might be very sensitive; that is, it mightindicate quickly and de
13、finitely small changes in force, butnevertheless, be very inaccurate. On the other hand, theaccuracy of the results is in general limited by the sensitivity.3.1.2 calibration, n in the case of force testing machines,the process of comparing the force indication of the machineunder test to that of a
14、standard, making adjustments as neededto meet error requirements.1These 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 approved June 1,
15、2014. Published August 2014. Originallyapproved in 1923. Last previous edition approved in 2013 as E4 13. DOI:10.1520/E0004-14.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information
16、, refer to the standards Document Summary page onthe ASTM website.*A Summary of Changes section appears at the end of this standardCopyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States13.1.3 capacity rangein the case of testing machines, th
17、erange of forces for which it is designed. Some testing machineshave more than one capacity range, that is, multiple ranges.3.1.4 correctionin the case of a testing machine, thedifference obtained by subtracting the indicated force from thecorrect value of the applied force.3.1.5 elastic calibration
18、 devicea device for use in verify-ing the force 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.3.1.6 error (or the d
19、eviation 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.3.1.6.1 DiscussionThe word “error” shall be used withnumerical values, for example, “At a force of 30
20、000 lbf (133kN), the error of the testing machine was + 15 lbf (67 N).”3.1.7 forcein the case of testing machines, a force mea-sured in units such as pound-force, newton, or kilogram-force.3.1.7.1 DiscussionThe pound-force is that force whichacting on a 1-lb mass will give to it an acceleration of 3
21、2.1740ft/s2(9.80665 m/s2). The newton is that force which acting ona 1-kg mass will give to it an acceleration of 1 m/s2.3.1.8 percent errorin the case of a testing machine, theratio, expressed as a percent, of the error to the correct value ofthe applied force.3.1.8.1 DiscussionThe test force, as i
22、ndicated 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# 3100where:A = force indicated by mach
23、ine being verified, lbf (or N),andB = correct value of the applied force, lbf (or N), asdetermined by the calibration device.3.1.9 permissible variation (or tolerance)in the case oftesting machines, the maximum allowable error in the value ofthe quantity indicated.3.1.9.1 DiscussionIt is convenient
24、to express permissiblevariation in terms of percentage of error. The numerical valueof the permissible variation for a testing machine is so statedhereafter in these practices.3.1.10 resolution of the force indicatorsmallest change offorce that can be estimated or ascertained on the forceindicating
25、apparatus of the testing machine, at any appliedforce. Appendix X1. describes a method for determiningresolution.3.1.10.1 resolution of analog type force indicators (scales,dials, recorders, etc.)the resolution is the smallest change inforce indicated by a displacement of a pointer, or pen line. The
26、resolution 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, 1:5, or1:10.Aspacing of 0.10 in. (2.5 mm) or greater is re
27、commendedfor the ratio of 1:10. A ratio less than 1:10 should not be used.3.1.10.1 DiscussionIf a force indicating dial has gradua-tions spaced every 0.080 in. (2.0 mm), the width of the pointeris approximately 0.040 in. (1.0 mm), and one graduationrepresent 5 lbf (25N). The ratio used would be 1:2
28、and theresolution would be equal to 2-1/2 lbf (12-1/2 N).3.1.10.2 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 anyapplied force.3.1.10.1 DiscussionA single digit or a comb
29、ination ofdigits may be the smallest change in force that can beindicated.3.1.10.2 DiscussionIf the force indication, for either typeof force indicator, fluctuates by more than twice the resolution,as described in 3.1.10.1 or 3.1.10.2, the resolution, expressedas a force, shall be equal to one-half
30、the range of thefluctuation.3.1.11 testing machine (force-measuring type)a mechani-cal device for applying a force to a specimen.3.1.11.1 portable testing machine (force-measuringtype)a device specifically designed to be moved from placeto place and for applying a force (load) to a specimen.3.1.12 v
31、erification, n in the case of force testing machines,the process of comparing the force indication of the machineunder test to that of a standard and reporting results, withoutmaking adjustments.3.1.13 verified range of forcesin the case of testingmachines, the range of indicated forces for which th
32、e testingmachine gives results within the permissible variations speci-fied.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
33、a product for shipment. No matterwhat the end use of the machine may be, it is necessary forusers to know that the amount of force applied and indicated istraceable to the International System of Units (SI) through aNational Metrology Institute (NMI). The procedures in Prac-tices E4 may be used to v
34、erify these machines so that theindicated forces are traceable to the SI. A key element oftraceability to the SI is that the devices used in the verificationhave known force characteristics, and have been calibrated inaccordance with Practice E74.4.2 The procedures in Practices E4 may be used by tho
35、seusing, manufacturing, and providing calibration service fortesting machines and related instrumentation.E41425. 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 Method
36、s6.1 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 offorces that can be verified, (2) the nonportability of any large
37、amount 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 testing
38、 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 throughan
39、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 free fr
40、om 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 the Forc
41、e Measuring System out of theTest Machine.Out of the test machine verifications shall be in accordancewith the main body of Practices E4 and its Annex A17.2 System verification is invalid if the devices are removedand checked independently of the testing machine unlessverification is performed accor
42、ding 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 established durin
43、g 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 connector so
44、 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 new force
45、 measuring devices shallrequire that interchangeability be established per 7.3.7.4 A Practices E4 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 Practices
46、E4 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 E4 requirements, the “asfound” data may be reported and may be used in accordancewi
47、th 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 improve theaccurac
48、y 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 through leveror ba
49、lance-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 = 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,
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