ASTM E83-2016 1214 Standard Practice for Verification and Classification of Extensometer Systems《伸长仪系统检验和分类标准实施规程》.pdf

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1、Designation: E83 16Standard Practice forVerification and Classification of Extensometer Systems1This standard is issued under the fixed designation E83; the number immediately following the designation indicates the year of originaladoption or, in the case of revision, the year of last revision. A n

2、umber 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 U.S. Department of Defense.1. Scope*1.1 This practice covers procedures for the verificat

3、ion andclassification of extensometer systems, but it is not intended tobe a complete purchase specification. The practice is applicableonly to instruments that indicate or record values that areproportional to changes in length corresponding to eithertensile or compressive strain. Extensometer syst

4、ems are clas-sified on the basis of the magnitude of their errors.1.2 Because strain is a dimensionless quantity, this docu-ment can be used for extensometers based on either SI or UScustomary units of displacement.NOTE 1Bonded resistance strain gauges directly bonded to a speci-men cannot be calibr

5、ated or verified with the apparatus described in thispractice for the verification of extensometers having definite gauge points.(See procedures as described in Test Methods E251.)1.3 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is therespo

6、nsibility 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. Referenced Documents2.1 ASTM Standards:2E6 Terminology Relating to Methods of Mechanical TestingE21 Test Methods for Elevated Temper

7、ature Tension Tests ofMetallic MaterialsE251 Test Methods for Performance Characteristics of Me-tallic Bonded Resistance Strain Gages2.2 Other Standards:3JCGM 100:2008 Evaluation of measurement data Guide tothe expression of uncertainty in measurement3. Terminology3.1 Definitions:3.1.1 In addition t

8、o the terms listed, see Terminology E6.3.1.2 calibrationa determination of the calibration factorfor a system using established procedures.3.1.3 calibration factorthe factor by which the change inextensometer reading must be multiplied to obtain the equiva-lent strain.3.1.3.1 DiscussionFor any exten

9、someter, the calibrationfactor is equal to the ratio of change in length to the product ofthe gauge length and the change in the extensometer reading.For direct-reading extensometers the calibration factor is unity.3.1.4 compressometera specialized extensometer used forsensing negative or compressiv

10、e strain.3.1.5 deflectometera specialized extensometer used forsensing of extension or motion, usually without reference to aspecific gauge length.3.1.6 error, in extensometer systemsthe value obtained bysubtracting the correct value of the strain from the indicatedvalue given by the extensometer sy

11、stem.3.1.7 extensometer, na device for sensing strain.3.1.8 extensometer systemsa system for sensing and indi-cating strain.3.1.8.1 DiscussionThe system will normally include anextensometer, conditioning electronics and auxiliary device(recorder, digital readout, computer, etc.). However, com-pletel

12、y self-contained mechanical devices are permitted. Anextensometer system may be one of three types.3.1.9 Type 1 extensometer system, nan extensometer sys-tem which both defines gauge length and senses extension, forexample, a clip-on strain gauge type with conditioning elec-tronics.3.1.10 Type 2 ext

13、ensometer system, nan extensometerwhich senses extension and the gauge length is defined byspecimen geometry or specimen features such as ridges ornotches.3.1.10.1 DiscussionA Type 2 extensometer is used wherethe extensometer gauge length is determined by features on thespecimen, for example, ridges

14、, notches, or overall height (incase of compression test piece). The precision associated with1This practice is under the jurisdiction of ASTM Committee E28 on MechanicalTesting and is the direct responsibility of Subcommittee E28.01 on Calibration ofMechanical Testing Machines and Apparatus.Current

15、 edition approved Dec. 15, 2016. Published January 2017. Originallyapproved in 1950. Last previous edition approved in 2010 as E83 10a. DOI:10.1520/E0083-16.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of AS

16、TMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3Available from International Organization for Standardization (ISO), ISOCentral Secretariat, BIBC II, Chemin de Blandonnet 8, CP 401, 1214 Vernier,Geneva, Switzerland, http:/www.iso.org.*A Summary of Cha

17、nges section appears at the end of this standardCopyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United StatesThis international standard was developed in accordance with internationally recognized principles on standardization established in the De

18、cision on Principles for theDevelopment of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.1gauge length setting for a Type 2 extensometer should bespecified in relevant test method or product standard. Thepositio

19、n readout on a testing machine is not recommended foruse in a Type 2 extensometer system.3.1.11 Type 3 extensometer system, nan extensometersystem which intrinsically senses strain (ratiometric principle),for example, video camera system.3.1.12 gauge length (L), nthe original length of thatportion o

20、f the specimen over which strain or change of lengthis determined.3.1.12.1 DiscussionIf the device is used for sensing ex-tension or motion, and gauge length is predetermined by thespecimen geometry or specific test method, then only resolu-tion and strain error for a specified gauge length shouldde

21、termine the class of extensometer system.3.1.13 resolution of the strain indicatorthe smallestchange in strain that can be estimated or ascertained on thestrain indicating apparatus of the testing system, at any appliedstrain.3.1.14 resolution of the digital type strain indicators (nu-meric displays

22、, printouts, and so forth)the resolution is thesmallest change in strain that can be displayed on the strainindicator (may be a single digit or a combination of digits) atany applied strain.3.1.14.1 DiscussionIf the strain indication, for either typeof strain indicator, fluctuates more than twice th

23、e resolution, asdescribed in 3.1.13 or 3.1.14, the resolution expressed as astrain shall be equal to one-half the range of fluctuation.3.1.15 verificationa determination that a system meets therequirements of a given classification after calibration accord-ing to established procedures.3.1.16 verifi

24、cation apparatusa device for verifying exten-someter systems.3.1.16.1 DiscussionThis device is used to simulate thechange in length experienced by a test specimen as a result ofthe applied force. The extensometer may either be attacheddirectly to the mechanism or interfaced with it in a mannersimila

25、r to normal operation (that is, possibly without contactfor some optical extensometers).4. Verification Apparatus4.1 The apparatus for verifying extensometer systems shallprovide a means for applying controlled displacements to asimulated specimen and for measuring these displacementsaccurately. It

26、may consist of a rigid frame, suitable coaxialspindles, or other fixtures to accommodate the extensometerbeing verified, a mechanism for moving one spindle or fixtureaxially with respect to the other, and a means for measuringaccurately the change in length so produced,4or any otherdevice or mechani

27、sm that will accomplish the purpose equallywell. The mechanism provided for moving one spindle relativeto the other shall permit sensitive adjustments. The changes inlength shall be measured, for example, by means of aninterferometer, calibrated standard gauge blocks and anindicator, a calibrated mi

28、crometer screw, or a calibrated lasermeasurement system. If standard gauge blocks and anindicator, or a micrometer screw, are used, they shall becalibrated and their limits of accuracy and sensitivity stated.The errors of the verification apparatus shall not exceed onethird of the permissible error

29、of the extensometer.4.2 The verification apparatus shall be calibrated at intervalsnot to exceed two years.NOTE 2He-Ne laser interferometer measurement systems based onthe 0.633 m wavelength line are considered to be primary-baseddisplacement standards and do not require recalibration.54.3 If the ve

30、rification apparatus is to be used to verifyextensometers used for bidirectional tests, the errors of theverification apparatus should be measured in both directions oftravel so as to include any backlash present.5. Verification Procedure for Extensometer Systems5.1 General RequirementsThe verificat

31、ion of an exten-someter system should not be done unless the components ofthe system are in good working condition. Thoroughly inspectall parts associated with smooth operation of the instrument toensure there are no excessively worn components. Repair orreplace parts as necessary. Remove any dirt p

32、articles whichmay have accumulated through normal use of the instrument.Verification of the system shall be performed whenever partsare interchanged or replaced. Some extensometers have partsthat are designed to be interchanged such as gauge lengthextenders and lenses used with video extensometers.

33、If theseparts can be shown to be interchangeable without degrading theverified classification of the extensometer, they may be inter-changed between scheduled verifications of the extensometer.Verification of the extensometer with all combinations ofinterchangeable parts that are anticipated to be u

34、sed for testingis required.5.1.1 The verification of an extensometer system refers to aspecific extensometer used with a specific readout device.Unless it can be demonstrated that autographic extensometersand recorders of a given type may be used interchangeablywithout introducing errors that would

35、affect the classificationof the extensometer, the extensometer shall be calibrated withthe readout device with which it is to be used.5.1.2 Prior to the initial verification, the extensometershould be calibrated according to the manufacturers instruc-tions or established procedures. The calibration

36、procedure mayinclude adjustment of span or determination of calibrationfactor, or both.5.2 Gauge Length Measurement MethodMeasure thegauge length of self-setting instruments by either the direct orindirect method.NOTE 3The following is an example of an indirect method. Set theextensometer to its sta

37、rting position and mount it on a soft rod of the4A review of some past, current, and possible future methods for calibratingstrain measuring devices is given in the paper by Watson, R. B., “CalibrationTechniques for Extensometry: Possible Standards of Strain Measurement,” Journalof Testing and Evalu

38、ation, JTEVA, Vol. 21, No. 6, November 1993, pp. 515521.5A letter from NIST (National Institute of Standards and Technology) has beenfiled at ASTM International Headquarters and may be obtained by requestingResearch Report RR: E28-1013.E83162typical specimen size or diameter. After the extensometer

39、is removed,measure the distance between the marks left by the gauge points (or knifeedges). If there are four or more gauge points, take the average of theindividual lengths as the gauge length. The differences between individualmeasurements shall not exceed the tolerance given for the class ofexten

40、someter. If there are two gauge points (or knife edges), but onopposite sides of the specimen, attach the extensometer twice rotating it180 with respect to the rod. Take the average of the lengths thusestablished on each side of the rod as the gauge length.5.2.1 Make two measurements of the gauge le

41、ngth. Deter-mine and record the error from each measurement, which is thedifference between the measured gauge length and the speci-fied gauge length, expressed as a percent of the specified gaugelength.5.2.2 For extensometer devices that do not have a self-setting gauge length during use, such as d

42、eflectometers andsome high-temperature tensile or creep extensometers, verifi-cation run errors should be calculated using the gauge lengthfor which the device is used. Separate classifications should beestablished for each gauge length or range used.5.2.3 Some extensometers have the capability to m

43、easurethe gauge length set by or chosen by the user. If thismeasurement is used in the calculation of strain, then it is theinherent measurement accuracy that is the important factorrather than the error between the chosen length and the actual.NOTE 4An example of an extensometer that is described b

44、y 5.2.3 isan optical extensometer that measures the position of “flags” attached tothe test specimen. The flags are positioned at the approximate requiredgauge length and the instrument measures the position of the flags (theactual gauge length) before and after the specimen is stressed. Althoughthi

45、s kind of device usually has a stated accuracy of gauge length, it mustbe verified by either direct or indirect methods at the appropriate gaugelengths.5.3 Position of ExtensometerCarefully position the exten-someter on or interface it to the verification device in the samemanner as it is normally u

46、sed for typical specimens. Forextensometers that attach directly to the specimen, the verifi-cation device should allow attachment to pieces that are similarto the specimen on which the extensometer will be attached.5.4 Temperature ControlVerify the extensometer at ap-proximately the same temperatur

47、e at which it will be used.Allow sufficient time for the verification device and extensom-eter to reach satisfactory temperature stability. Maintain tem-perature stability by excluding drafts throughout the subse-quent verification. Record the temperature during eachverification run.NOTE 5Extensomet

48、ers used for high-temperature testing may beverified at ambient temperature to insure proper operation, but fixturesshould be designed to verify performance at the actual test temperature.This is especially true with optical extensometers which may be adverselyaffected by air density changes associa

49、ted with thermal gradients andturbulence, environmental chamber windows, or specimen changes due tothe environment. See Appendix X2.5.5 Method of ReadingRead the instrument or, in the caseof an autographic extensometer, measure the record in the samemanner as during use.5.5.1 For extensometer with dial micrometers or digitalreadouts, the readings shall be recorded. Extensometers thatuse autographic methods shall have their charts read andrecorded using a suitable measuring device, such as a vernieror dial caliper. The use of an optical magnifying