1、Designation: E4 14E4 15 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 or
2、iginaladoption 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
3、Defense.1. Scope*1.1 These practices cover procedures for the force verification, 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 complet
4、e purchase specifications for testing machines. Testing machines may be verified by oneof 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 cov
5、er the verification of all types of testing machines designed to measure forces, for example, theconstant-rate-of-loading type which operates on the inclined-plane principle. This type of machine may be verified as directed in the applicable appendixof Specification D76D76/D76M.1.2 The procedures of
6、 1.1.1 1.1.3 apply to the verification of the force-indicating systems associated with the testing machine,such as a scale, dial, marked or unmarked recorder chart, digital display, etc. In all cases the buyer/owner/user must designate theforce-indicating system(s) to be verified and included in the
7、 report.1.3 The values stated in inch-pound units are to be regarded as standard. The values given in parentheses are mathematicalconversions to SI units that are provided for information only and are not considered standard.1.3.1 Since conversion factors are not required in this practice, either in
8、ch-pound units, SI units, or metric values can be usedas the standard.1.4 Forces indicated on displays/printouts of testing machine data systemsbe they instantaneous, delayed, stored, orretransmittedwhich are verified with provisions of 1.1.1, 1.1.2, or 1.1.3, and are within the 61 % accuracy requir
9、ement, complywith Practices E4.1.5 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 standard to establish appropriate safety and health practices and determine the applicability of regulatorylimitations
10、 prior to use.2. Referenced Documents2.1 ASTM Standards:2D76D76/D76M Specification for Tensile Testing Machines for TextilesE74 Practice of Calibration of Force-Measuring Instruments for Verifying the Force Indication of Testing MachinesE467 Practice for Verification of Constant Amplitude Dynamic Fo
11、rces in an Axial Fatigue Testing System3. Terminology3.1 Definitions:3.1.1 accuracythe specified permissible variation from the reference value.1 These practices are under the jurisdiction of ASTM Committee E28 on Mechanical Testing and is the direct responsibility of Subcommittee E28.01 on Calibrat
12、ion ofMechanical Testing Machines and Apparatus.Current edition approved June 1, 2014Dec. 1, 2015. Published August 2014January 2016. Originally approved in 1923. Last previous edition approved in 20132014 asE4 13.E4 14. DOI: 10.1520/E0004-14.10.1520/E0004-15.2 For referencedASTM standards, visit th
13、eASTM 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 the ASTM website.This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an
14、 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 consult prior editions as appropriate. In all cases only the current versionof the standard as published by ASTM is to
15、 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 Conshohocken, PA 19428-2959. United States13.1.1.1 DiscussionA testing machine is said to be accurate if the indicated force is
16、 within the specified permissible variation from the actual force.In these methods 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 wit
17、h sensitivity. Forexample, a testing machine might be very sensitive; that is, it might indicate quickly and definitely small changes in force, butnevertheless, be very inaccurate. On the other hand, the accuracy of the results is in general limited by the sensitivity.3.1.2 calibration, n in the cas
18、e of force testing machines, the process of comparing the force indication of the machine undertest to that of a standard, making adjustments as needed to meet error requirements.3.1.3 capacity rangein the case of testing machines, the range of forces for which it is designed. Some testing machines
19、havemore than one capacity range, that is, multiple ranges.3.1.4 correctionin the case of a testing machine, the difference obtained by subtracting the indicated force from the correctvalue of the applied force.3.1.5 elastic calibration devicea device for use in verifying the force readings of a tes
20、ting machine consisting of an elasticmember(s) to which forces may be applied, combined with a mechanism or device for indicating the magnitude (or a quantityproportional to the magnitude) of deformation under force.3.1.6 error (or the deviation from the correct value)in the case of a testing machin
21、e, the difference obtained by subtractingthe force indicated by the calibration device from the force indicated by the testing machine.3.1.6.1 DiscussionThe word “error” shall be used with numerical values, for example, “At a force of 30 000 lbf (133 kN), the error of the testingmachine was + 15 lbf
22、 (67 (+ 67 N).”3.1.7 forcein the case of testing machines, a force measured in units such as pound-force, newton, or kilogram-force.3.1.7.1 DiscussionThe pound-force is that force which acting on a 1-lb mass will give to it an acceleration of 32.1740 ft/s2 (9.80665 m/s2). Thenewton is that force whi
23、ch acting on a 1-kg mass will give to it an acceleration of 1 m/s2.3.1.8 percent errorin the case of a testing machine, the ratio, expressed as a percent, of the error to the correct value of theapplied force.3.1.8.1 DiscussionThe test force, as indicated by the testing machine, and the applied forc
24、e, as computed from the readings of the verification device,shall be recorded at each test point. The error, E, and the percent error, Ep, shall be calculated from these data as follows:E 5A 2B (1)Ep 5A 2B!/B#3100where:A = force indicated by machine being verified, lbf (or N), andB = correct value o
25、f the applied force, lbf (or N), as determined by the calibration device.3.1.9 permissible variation (or tolerance)in the case of testing machines, the maximum allowable error in the value of thequantity indicated.3.1.9.1 DiscussionIt is convenient to express permissible variation in terms of percen
26、tage of error. The numerical value of the permissible variationfor a testing machine is so stated hereafter in these practices.3.1.10 resolution of the force indicatorsmallest change of force that can be estimated or ascertained on the force indicatingapparatus of the testing machine, at any applied
27、 force. Appendix X1. describes a method for determining resolution.3.1.10.1 resolution of analog type force indicators (scales, dials, recorders, etc.)the resolution is the smallest change in forceindicated by a displacement of a pointer, or pen line. The resolution is calculated by multiplying the
28、force corresponding to onegraduation by the ratio of the width of the pointer or pen line to the center to center distance between two adjacent graduationE4 152marks. The typical ratios used are 1:1, 1:2, 1:5, or 1:10. A spacing of 0.10 in. (2.5 mm) or greater is recommended for the ratioof 1:10. A
29、ratio less than 1:10 should not be used.3.1.10.1 DiscussionIf a force indicating dial has graduations spaced every 0.080 in. (2.0 mm), the width of the pointer is approximately 0.040 in. (1.0mm), and one graduation represent 5 lbf (25N). The ratio used would be 1:2 and the resolution would be equal
30、to 2-1/2 lbf (12-1/2N).3.1.10.2 resolution of digital type force indicators (numeric, displays, printouts, etc.)the resolution is the smallest change inforce that can be displayed on the force indicator, at any applied force.3.1.10.1 DiscussionA single digit or a combination of digits may be the sma
31、llest change in force that can be indicated.3.1.10.2 DiscussionIf the force indication, for either type of force indicator, fluctuates by more than twice the resolution, as described in 3.1.10.1 or3.1.10.2, the resolution, expressed as a force, shall be equal to one-half the range of the fluctuation
32、.3.1.11 testing machine (force-measuring type)a mechanical device for applying a force to a specimen.3.1.11.1 portable testing machine (force-measuring type)a device specifically designed to be moved from place to place andfor applying a force (load) to a specimen.3.1.12 verification, n in the case
33、of force testing machines, the process of comparing the force indication of the machine undertest to that of a standard and reporting results, without making adjustments.3.1.13 verified range of forcesin the case of testing machines, the range of indicated forces for which the testing machine givesr
34、esults within the permissible variations specified.4. Significance and Use4.1 Testing machines that apply and indicate force are used in many industries, in many ways. They may be used in a researchlaboratory to measure material properties, and in a production line to qualify a product for shipment.
35、 No matter what the end useof the machine may be, it is necessary for users to know that the amount of force applied and indicated is traceable to theInternational System of Units (SI) through a National Metrology Institute (NMI). The procedures in Practices E4 may be used toverify these machines so
36、 that the indicated forces are traceable to the SI. A key element of traceability to the SI is that the devicesused in the verification have known force characteristics, and have been calibrated in accordance with Practice E74.4.2 The procedures in Practices E4 may be used by those using, manufactur
37、ing, and providing calibration service for testingmachines and related instrumentation.5. Calibration Devices5.1 When verifying testing machines, use calibration devices only over their Class A force ranges as determined by PracticeE74.6. Advantages and Limitations of Methods6.1 Verification by Stan
38、dard WeightsVerification by the direct application of standard weights to the weighing mechanism ofthe testing machine, where practicable, is the most accurate method. Its limitations are: (1) the small range of forces that can beverified, (2) the nonportability of any large amount of standards weig
39、hts, and (3) its nonapplicability to horizontal testing machinesor vertical testing machines having weighing mechanisms that are not designed to be actuated by a downward force.6.2 Verification by Equal-Arm Balance and Standard WeightsThe second method of verification of testing machines involvesmea
40、surement of the force by means of an equal-arm balance and standard weights. This method is limited to a still smaller rangeof forces than the foregoing method, and is generally applicable only to certain types of hardness testing machines in which theforce is applied through an internal lever syste
41、m.6.3 Verification by Elastic Calibration DevicesThe third method of verification of testing machines involves measurement ofthe elastic strain or deflection under force of a ring, loop, tension or compression bar, or other elastic device. The elastic calibrationdevice is free from the limitations r
42、eferred to in 6.1 and 6.2.E4 1537. System Verification7.1 A testing machine shall be verified as a system with the force sensing and indicating devices (see 1.2 and 1.4) in place andoperating as in actual use.7.1.1 If this is not technically possible, refer to Annex A1, Verifying the Force Measuring
43、 System out of the Test Machine. Outof the test machine verifications shall be in accordance with the main body of Practices E4 and its Annex A17.2 System verification is invalid if the devices are removed and checked independently of the testing machine unlessverification is performed according to
44、Annex A1.7.3 Many testing machines utilize more than one force measuring device in order to obtain more accurate force indication atlower applied forces. These devices are routinely installed and uninstalled in the testing machine. For such devices,interchangeability shall be established during the
45、original verification and shall be reestablished after an adjustment is performed.This is accomplished by performing a normal verification with the device in place as during normal use. It is advisable thatorientation be kept consistent, such as by noting the direction of the cable connector so that
46、 when reinstalling the device, theorientation will be repeated. Remove and reinstall the device between the two verification runs to demonstrate interchangeability.Repeat the procedure for each interchangeable force measuring device used in the testing machine.7.3.1 Introduction of the new force mea
47、suring devices shall require that interchangeability be established per 7.3.7.4 A Practices E4 Verification consists of at least two verification 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 within the Practices E
48、4 requirements of Section 17, the data may be used“as found” for run one of the two required for the new verification report.7.4.2 If the initial verification run produces any values which are outside of the Practices E4 requirements, the “as found” datamay be reported and may be used in accordance
49、with applicable quality control programs. Calibration adjustments shall be madeto the force indicator system(s), after which the two required verification runs shall be conducted and reported in the newverification report and certificate.7.4.3 Calibration adjustments may be made to improve the accuracy of the system. They shall be followed by the two requiredverification runs, and issuance of a new verification report and certificate.8. Gravity and Air Buoyancy Corrections8.1 In the verification of testing machines, where standard weights are
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