1、Designation: E4 10E4 13 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 Department of Defen
3、se.1. Scope1.1 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 complete purc
4、hase 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 cover the
5、 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 D76.1.2 The procedures of 1.1.1-1.1.3 a
6、pply 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 report.1.3 Th
7、e 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 inch-pound units
8、, 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 requirement, complyw
9、ith 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 prior to use.
10、2. Referenced Documents2.1 ASTM Standards:2D76 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 Forces in an Axial Fatig
11、ue Testing System3. Terminology3.1 Definitions:3.1.1 testing machine (force-measuring type)a mechanical device for applying a force to a specimen.1 These practices are under the jurisdiction of ASTM Committee E28 on Mechanical Testing and is the direct responsibility of Subcommittee E28.01 on Calibr
12、ation ofMechanical Testing Machines and Apparatus.Current edition approved June 1, 2010April 1, 2013. Published July 2010 May 2013. Originally approved in 1923. Last previous edition approved in 20092010 asE4 09a.E4 10. DOI: 10.1520/E0004-10.10.1520/E0004-13.2 For referencedASTM standards, visit the
13、ASTM 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.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States13.1.1.1 portable testing machine (force-measuring type)a device specifically designed to be moved from place to place andfor applying a force (load) t
16、o a specimen.3.1.2 forcein the case of testing machines, a force measured in units such as pound-force, newton, or kilogram-force.3.1.2.1 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 which
17、 acting on a 1-kg mass will give to it an acceleration of 1 m/s2.3.1.3 accuracythe specified permissible variation from the reference value.3.1.3.1 DiscussionA testing machine is said to be accurate if the indicated force is within the specified permissible variation from the actual force.In these m
18、ethods 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 i
19、s, 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.3.1.4 error (or the deviation from the correct value)in the case of a testing machine, the difference obtai
20、ned by subtractingthe force indicated by the calibration device from the force indicated by the testing machine.3.1.4.1 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 (67 N).”3.1.5 percent
21、errorin the case of a testing machine, the ratio, expressed as a percent, of the error to the correct value of theapplied force.3.1.5.1 DiscussionThe test force, as indicated by the testing machine, and the applied force, as computed from the readings of the verification device,shall be recorded at
22、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 of the applied force, lbf (or N), as determined by the calibration device.3.1.6 co
23、rrectionin the case of a testing machine, the difference obtained by subtracting the indicated force from the correctvalue of the applied force.3.1.7 permissible variation (or tolerance)in the case of testing machines, the maximum allowable error in the value of thequantity indicated.3.1.7.1 Discuss
24、ionIt 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.3.1.8 capacity rangein the case of testing machines, the range of forces for which it is designed. Som
25、e testing machines havemore than one capacity range, that is, multiple ranges.3.1.9 verified range of forcesin the case of testing machines, the range of indicated forces for which the testing machine givesresults within the permissible variations specified.3.1.9.1 calibration, n in the case of forc
26、e 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.3.1.9.2 verification, n in the case of force testing machines, the process of comparing the force indication of the machine undert
27、est to that of a standard and reporting results, without making adjustments.E4 1323.1.10 elastic calibration devicea device for use in verifying the force readings of a testing machine consisting of an elasticmember(s) to which forces may be applied, combined with a mechanism or device for indicatin
28、g the magnitude (or a quantityproportional to the magnitude) of deformation under force.3.1.11 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 force. Appendix X1. describes a method
29、 for determining resolution.3.1.11.1 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 force corresponding to onegraduation by
30、 the ratio of the width of the pointer or pen line to the center to center distance between two adjacent graduationmarks. 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 ratio less than 1:10 should not be used.(1) D
31、iscussionIf a force indicating dial has graduations spaced every 0.080 in. (2.0 mm), the width of the pointer isapproximately 0.040 in. (1.0 mm), and one graduation represent 5 lbf (25N). The ratio used would be 1:2 and the resolution wouldbe equal to 2-1/2 lbf (12-1/2 N).3.1.11.2 resolution of digi
32、tal 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.(1) DiscussionA single digit or a combination of digits may be the smallest change in force that can be indicated.3.1.12 If t
33、he force indication, for either type of force indicator, fluctuates by more than twice the resolution, as described in3.1.11.1 or 3.1.11.2, the resolution, expressed as a force, shall be equal to one-half the range of the fluctuation.4. Significance and Use4.1 Testing machines that apply and indicat
34、e 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. No matter what the end useof the machine may be, it is necessary for users to know the amount of force that is appli
35、ed and indicated, and that the accuracyof the force is traceable to the National Institute of Standards and Technology (NIST), formerly NBS. Practices E4 provides aprocedure to verify these machines, in order that the indicated forces may be traceable. A key element to this NIST traceabilityis that
36、the devices used in the verification have known force characteristics, and have been calibrated in accordance with PracticeE74.4.2 The procedures in Practices E4 may be used by those using, manufacturing, and providing calibration service for testingmachines and related instrumentation.5. Calibratio
37、n 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 Standard WeightsVerification by the direct application of standard weights to the weighing mechanism oft
38、he 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 weights, and (3) its nonapplicability to horizontal testing machinesor vertical testing machines having
39、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 involvesmeasurement of the force by means of an equal-arm balance and standard weights. This method is limited
40、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 system.6.3 Verification by Elastic Calibration DevicesThe third method of verification of testing machine
41、s 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 referred to in 6.1 and 6.2.7. System Verification7.1 A testing machine shall be verified as a system
42、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 System out of the Test Machine. Outof the test machine verifications shall be in accordance with the main
43、 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 Annex A1.7.3 Many testing machines utilize more than one force measuring device in order to obtain more ac
44、curate force indication atlower applied forces. These devices are routinely installed and uninstalled in the testing machine. For such devices,E4 133interchangeability shall be established during the original verification and shall be reestablished after an adjustment is performed.This is accomplish
45、ed 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 when reinstalling the device, theorientation will be repeated. Remove and reinstall the device betw
46、een 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 measuring devices shall require that interchangeability be established per 7.3.7.4 A Practices E4 Verif
47、ication 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 E4 requirements of Section 17, the data may be used“as found” for run one of the two required for the
48、 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 with applicable quality control programs. Calibration adjustments shall be madeto the force indicato
49、r 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 used for applying forces directly or through lever orbalance-arm systems, correct the force for the loc
