1、Designation: E1856 13Standard Guide forEvaluating Computerized Data Acquisition Systems Used toAcquire Data from Universal Testing Machines1This standard is issued under the fixed designation E1856; the number immediately following the designation indicates the year oforiginal adoption or, in the ca
2、se of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope*1.1 This guide is intended to assist the user in the evaluationand documentation of computeri
3、zed data acquisition systemsused to acquire data from quasi-static tests, performed onuniversal testing machines. The report produced will aid in thecorrect use and calibration of the computerized universaltesting machine.1.2 The values stated in SI units are to be regarded asstandard. No other unit
4、s of measurement are included in thisstandard.1.3 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 regul
5、atory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2E4 Practices for Force Verification of Testing MachinesE6 Terminology Relating to Methods of Mechanical TestingE8/E8M Test Methods for Tension Testing of Metallic Ma-terialsE74 Practice of Calibration of Force-Measuring Instru
6、mentsfor Verifying the Force Indication of Testing MachinesE83 Practice for Verification and Classification of Exten-someter SystemsE691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test MethodE1012 Practice for Verification of Testing Frame and Speci-men Alignment
7、 Under Tensile and Compressive AxialForce Application3. Terminology3.1 The definitions of mechanical testing terms that appearin Terminology E6 apply to this guide.3.2 Definitions:3.2.1 resolution, nfor a particular measurement device,the smallest change in the quantity being measured that causesa p
8、erceptible change in the corresponding indication.3.2.1.1 DiscussionResolution may depend on the value(magnitude) of the quantity being measured.3.2.1.2 DiscussionFor paper charts or analog indicators,the resolution should not be assumed to be better (smaller) than110 of the spacing between graduati
9、ons. For digital devices, thebest resolution potentially achievable is the smallest differencebetween two different readings given by the display.3.2.1.3 DiscussionFor both analog and digital devices, theactual resolution can be significantly poorer than describedabove, due to factors such as noise,
10、 friction, etc.3.3 Definitions of Terms Specific to This Standard:3.3.1 basic data, nthe digital equivalents of analogcounterparts, such as force and displacement measurements,which under static conditions are traceable to national stan-dards (see Fig. 1).3.3.2 computerized data acquisition systema
11、device thatcollects basic data from a universal testing machine during atest and calculates and presents derived data based on the basicdata collected.3.3.3 derived data, nadditional numbers derived from thebasic data through computation using software algorithms,such as a peak force or a modulus va
12、lue.3.3.4 data acquisition rate, nthe rate at which digitalsamples of each wave-form (that is, force, strain, displacement,and so forth) are acquired, expressed in samples/second.3.3.5 transducer-channel bandwidththe frequency atwhich the amplitude response of a transducer channel hasfallen by 3 dB;
13、 that is, the measured signal is in error by about30 % and the phase shift is 45 or greater.3.3.5.1 DiscussionThe precise amplitude and phase re-sponses vary with the electrical design of the computerizeddata acquisition system, but the 3 dB bandwidth (expressed inhertz) is a simple single measure o
14、f responsiveness (see Fig. 2).1This guide is under the jurisdiction of ASTM Committee E28 on MechanicalTesting and is the direct responsibility of Subcommittee E28.15 on AutomatedTesting.Current edition approved Nov. 15, 2013. Published January 2014. Originallyapproved in 1997. Last previous edition
15、 approved in 2008 as E185697(2008). DOI:10.1520/E1856-13.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.*A S
16、ummary 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 States14. Summary of Guide4.1 Comparative tests are performed to determine if thederived data acquired with a computerized universal
17、 testingmachine agree with results acquired on the same machine fromgraphical records or with results acquired on other testingmachines to ensure that the materials being tested are correctlycharacterized.5. Significance and Use5.1 This guide is recommended to be used by anyoneacquiring data from a
18、universal testing machine using acomputerized data acquisition system.6. Procedure6.1 Choose at least five different test specimen types that arerepresentative of the specimens commonly tested on theuniversal testing machine. If the universal testing machine isused to test fewer than five different
19、specimen types, choose allthose tested. Specimen types may be differentiated by material(strength level), size, shape, or test performed.6.2 Use one of the following procedures to evaluate anddocument the conformity of the derived data.6.2.1 Round Robin Procedure:6.2.1.1 Perform a round robin involv
20、ing at least two otheruniversal testing machines. The other testing machines neednot necessarily be computerized.NOTE 1It is preferable to use universal testing machines of varyingtypes so that systemic problems are not masked.6.2.1.2 If possible, configure the universal testing machinesin such a wa
21、y as to be able to obtain a graphic record of thetests. The graphic record may be generated by analog signalsources, the computerized data acquisition system, or may begenerated manually from digital data recorded by the comput-erized data acquisition system.6.2.1.3 Ascertain that all readout and re
22、cording deviceshave been calibrated in accordance with Practices E4, E83,orother applicable standards.6.2.1.4 Test at least five specimens of each specimen typeon each machine in conformance with the applicable testmethods or established procedures.NOTE 2It may be desirable to test many more specime
23、ns after aninitial screening, particularly if high standard deviations are observed onall machines.6.2.1.5 Obtain the derived data from the computerized dataacquisition system or graphic records of the tests from eachmachine, or both.6.2.1.6 From the graphic records obtained, manually calcu-late the
24、 same test results obtained by the computerized dataacquisition system.6.2.1.7 Calculate the average and standard deviation of boththe manually calculated results and the derived data obtainedby the computerized data acquisition system(s) within eachgroup of five or more specimens.6.2.1.8 Investigat
25、e, identify, and correct, if necessary, thecause of any average results obtained by the computer thatdiffer from the manually obtained average results, or theaverage results obtained by other testing machines, by morethan 2.0 % of the average or more than one standard deviation,whichever is greater.
26、 In all cases, use the smallest non-zerostandard deviation for evaluations.6.2.1.9 Investigate, identify, and correct, if necessary, thecause of any standard deviations of the derived data obtainedby the computerized data acquisition system that are more thantwo times the standard deviation obtained
27、 manually or by theother machines.NOTE 3Differences in averages and standard deviations of thesemagnitudes are quite often due to variations in the material being tested,and a complete statistical evaluation of the data using methods such asPractice E691 may be necessary.6.2.2 Single Machine Procedu
28、re:6.2.2.1 This procedure may be used for universal testingmachines with the capability of producing graphic recordsfrom which derived data can be manually calculated.6.2.2.2 Configure the testing machine in such a way as to beable to obtain a graphic record of the tests. The graphic recordmay be ge
29、nerated by analog signal sources, the computerizeddata acquisition system, or may be generated manually fromdigital data recorded by the computerized data acquisitionsystem.6.2.2.3 Ascertain that all readout and recording devices used(analog or digital, or both) have been calibrated in accordancewit
30、h Practices E4, E83, or other applicable standards.6.2.2.4 Ascertain that all transducers with their readout orrecording devices, or both, including the devices producing theFIG. 1 Basic Data and Derived DataFIG. 2 BandwidthE1856 132graphic record, have the required transducer-channel band-width for
31、 the tests performed with the machine (see AppendixX2).6.2.2.5 Test at least five specimens of each specimen type inconformance with the applicable test methods or establishedprocedures, obtaining both a graphic record and derived datafrom the computerized data acquisition system at the sametime.6.2
32、.2.6 From the graphic record, determine the same testresults as are calculated by the computerized data acquisitionsystem.6.2.2.7 Calculate the average and standard deviation of boththe manually calculated results and the derived data obtainedby the computerized data acquisition system (derived data
33、)within each group of five specimens.6.2.2.8 Investigate, identify, and correct, if necessary, thecause of any average derived data obtained by the computer-ized data acquisition system that differ from the manuallyobtained average results by more than 2.0 % of the average ormore than one standard d
34、eviation, whichever is greater. In allcases, use the smallest non-zero standard deviation for evalu-ations.6.2.2.9 Investigate, identify, and correct, if necessary, thecause of any standard deviations of the derived data obtainedby the computerized data acquisition system that are more thantwo times
35、 the standard deviation of results obtained manually.7. Test Result Evaluation7.1 A bias in average results between machines or readoutsmay be due to one or more of the following:7.1.1 Calibration DifferencesA bias in all of the forceresults observed usually indicates a difference in calibration. If
36、maximum forces disagree between the manual and computer-ized results, it may be due to differences in calibration betweenparts of the machine (see Appendix X1). If force results are inagreement and stress results vary, the difference may be due tocross-sectional area or other measurements such as sp
37、an in aflexure test. If maximum force results agree and other forceresults differ, the difference is probably not due to differencesin force calibration.7.1.2 Differences in the Speed of TestingDepending on thestrain-rate sensitivity of the material being tested, a differencein derived data may be o
38、bserved if there is a difference in thespeed of testing. A simple way to check the speed of testing isto measure the elapsed time between two points during thetests.7.1.3 Incorrect Inputs to the Computer AlgorithmsIf theresults calculated by manual methods from the graphic recordagree with the other
39、 universal testing machines but the deriveddata from the computerized data acquisition system disagree,the difference may be due to incorrect inputs to the computeralgorithms.7.1.4 Algorithms UsedIf the results calculated by manualmethods from the graphic record agree with the other machinesbut the
40、derived data from the computer disagree, the differencemay be due to algorithms used by the computerized dataacquisition system.7.1.5 Algorithms That Are Not Working ProperlyIf theresults calculated by manual methods from the graphic recordagree with the other machines but the derived data from thec
41、omputerized data acquisition system disagree, the differencemay be due to algorithms that are not working properly.7.1.6 Ambiguity in the Interpretation of the Test MethodThe writer(s) of the algorithms used, or the user, or both, maybe interpreting the test method differently or incorrectly.7.1.7 D
42、ifferences in Gripping and Other Apparatus in Con-tact with the SpecimenDifferences in gripping and otherapparatus in contact with the specimen may cause prematurefailure of the specimen or act as a heat sink and causedifferences in elongation related results.7.1.8 Alignment of the Test PiecePoor al
43、ignment cancause lower-than-normal test results or poorly formed stress-strain curves, or both, in the elastic region of the curve (seePractice E1012).7.1.9 Insufficient bandwidth in one or more of the trans-ducer channels (see Appendix X2).NOTE 4Differences are just as likely to be due to problems
44、with themanually calculated results as they are to problems with the computergenerated derived data.NOTE 5For additional information, see the appendix on FactorsAffecting Tension Test Results in Test Methods E8/E8M.7.2 Adifference in the standard deviation between machinesmay be due to one or more o
45、f the following:7.2.1 Differences in ResolutionPoor resolution can showup in two forms. A standard deviation of zero may indicatepoor resolution. Alternatively, if two or more discrete deriveddata occur with a difference between them that is large relativeto the result being measured, poor resolutio
46、n may be the cause.Example: 206, 206, 210, 206, 210 (see Appendix X3).7.2.2 Specimen Dimension PrecisionIf derived-data forcestandard deviations agree and derived-data stress standarddeviations differ, the difference is probably due to imprecisemeasurements of cross sectional area.7.2.3 Differences
47、in the Speed of TestingTesting at speedsthat are too fast may give either high or low standard deviationsdue to one or more of the transducer-channel bandwidths (seeAppendix X2).7.2.4 Unstable Control of Test Speed Unstable control ofthe testing machine speed may increase the standard deviationof de
48、rived data in strain-rate sensitive materials and causepoorly formed stress-strain curves and measurement errors inextreme cases.7.2.5 Electrical Noise Being Picked Up By One or More ofthe Transducer ChannelsElectrical noise can cause computeralgorithms to perform poorly. This may be observed in the
49、graphic record or in the basic data. This problem may bedetected by capturing data at a fixed force or strain. Thestandard deviation of this data should be comparable to theresolution.7.2.6 Differences in Gripping and Other Apparatus in Con-tact with the SpecimenSome devices in contact with thespecimen may only cause an occasional premature failure. Thiswill show up as a high standard deviation.7.2.7 Alignment of the Test PiecePoor alignment is oftennot repeatable and leads to high standard deviations (seePractice E1012).E1856 1337.2.8 Insufficient b
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