1、Designation: E 1856 97 (Reapproved 2002)Standard Guide forEvaluating Computerized Data Acquisition Systems Used toAcquire Data from Universal Testing Machines1This standard is issued under the fixed designation E 1856; the number immediately following the designation indicates the year oforiginal ad
2、option or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This guide is intended to assist the user in the evaluationand docume
3、ntation of computerized 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 This standard does not purport to address all of thesa
4、fety 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. Referenced Documents2.1 ASTM Standards:E 4 Practices for Force Verific
5、ation of Testing Machines2E 8 Test Methods for Tension Testing of Metallic Materials2E 74 Practice for Calibration of Force Measuring Instru-ments for Verifying the Force Indication of Testing Ma-chines2E 83 Practice for Verification and Classification of Exten-someters Systems2E 691 Practice for Co
6、nducting an Interlaboratory Study toDetermine the Precision of a Test Method3E 1012 Practice for Verification of Specimen AlignmentUnder Tensile Loading23. Terminology3.1 Definitions:3.1.1 basic databasic data are the digital equivalents ofanalog counterparts, such as force and displacement measure-
7、ments, which under static conditions are traceable to nationalstandards (see Fig. 1).3.1.2 derived dataderived data are additional numbersderived from the basic data through computation using soft-ware algorithms, such as a peak force or a modulus value.3.1.3 data acquisition ratedata acquisition ra
8、te is definedas the rate at which digital samples of each wave-form (that is,force, strain, displacement, and so forth) are acquired, ex-pressed in samples/second.3.1.4 resolutionthe resolution is the smallest change inforce, strain, or displacement, or both, that can be displayed orobtained, or bot
9、h, from the computerized testing system at anyapplied force, strain, or position, or both (for force resolutionsee Practice E 4).3.1.5 transducer-channel bandwidththe bandwidth of atransducer-measurement channel which is measuring a force,strain, or displacement in a testing machine is the frequency
10、 atwhich the amplitude response of the measurement system hasfallen by 3 dB, that is, the measured signal is in error by about30 % and the phase shift has become 45 or greater. Theprecise amplitude and phase responses vary with the electricaldesign of the system, but the 3 dB bandwidth (expressed in
11、Hertz) is a simple single measure of responsiveness (see Fig.2).3.1.6 computerized data acquisition systemfor the pur-pose of this guide, a computerized data acquisition system is adevice which collects basic data from a universal testingmachine during a test and calculates and presents derived data
12、based on the basic data collected.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 Jan. 10, 1997. Published March 1997.2Annual Book of ASTM Standards, Vol 03.01.3Annua
13、l Book of ASTM Standards, Vol 14.02.FIG. 1 Basic Data and Derived Data1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.4. Summary of Guide4.1 Comparative tests are performed to determine if thederived data acquired with a computerized
14、 universal 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 da
15、ta from a universal testing machine using acomputerized data acquisition system.6. Procedure6.1 Choose at least five different test specimen types whichare representative of the specimens commonly tested on thetesting machine.NOTE 1If the testing machine is used to test less than five differentspeci
16、men types, choose all those tested.NOTE 2Specimen types can be differentiated by material (strengthlevel), size, shape, or test performed, or both.6.2 Use one of the following procedures to evaluate anddocument the conformity of the computerized test results.6.2.1 Round Robin Procedure:6.2.1.1 Perfo
17、rm a round robin involving at least two othertesting machines. The other testing machines need not neces-sarily be computerized.NOTE 3It is preferable to use testing machines of varying types sothat systemic problems are not masked.6.2.1.2 If possible, configure the testing machines in such away as
18、to be able to obtain a graphic record of the tests. Thegraphic record may be generated by analog signal sources, thecomputer system, or may be generated manually from digitaldata recorded by the data system.6.2.1.3 Ascertain that all readout and recording deviceshave been calibrated in accordance wi
19、th Practices E 4, E 83, 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 4It may be desirable to test many more specimens after aninitial screening, particularly if hig
20、h standard deviations are observed onall machines.6.2.1.5 Obtain the results from the computer system orgraphic records of the tests from each machine, or both.6.2.1.6 From the graphic records obtained, manually calcu-late the same test results obtained by the computer system.6.2.1.7 Calculate the a
21、verage and standard deviation of boththe manually calculated results and the results obtained by thecomputer system(s) (derived data) within each group of five ormore specimens.6.2.1.8 Investigate, identify, and correct, if necessary, thecause of any average results obtained by the computer whichdif
22、fer 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.NOTE 5In all cases, use the smallest non-zero standard deviation forevaluations.6.2.1.9 Investigate, ide
23、ntify, and correct, if necessary, thecause of any standard deviations of the results obtained by thecomputer which are more than two times the standard deviationobtained manually or by the other machines.NOTE 6Differences in averages and standard deviations of thesemagnitudes are quite often due to
24、variations in the material being tested,and a complete statistical evaluation of the data using methods such asPractice E 691 may be necessary.6.2.2 Single Machine Procedure:6.2.2.1 This procedure may be used for testing machineswith the capability of producing graphic records from whichtest results
25、 (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 generated by analog signal sources, the computersystem, or may be generated manually from digital datarecorded by the data sys
26、tem.6.2.2.3 Ascertain that all readout and recording devices used(analog or digital, or both) have been calibrated in accordancewith Practices E 4, E 83, or other applicable standards.6.2.2.4 Ascertain that all transducers with their readout orrecording devices, or both, including the devices produc
27、ing thegraphic record, have the required bandwidth for the testsperformed with the machine (see Appendix X2).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 results fromthe compute
28、r system at the same time.6.2.2.6 From the graphic record, determine the same testresults as are calculated by the computer system.6.2.2.7 Calculate the average and standard deviation of boththe manually calculated results and the results obtained by thecomputer system (derived data) within each gro
29、up of fivespecimens.6.2.2.8 Investigate, identify, and correct, if necessary, thecause of any average results obtained by the computer whichdiffer from the manually obtained average results by more than2.0 % of the average or more than one standard deviation,whichever is greater.NOTE 7In all cases,
30、use the smallest non-zero standard deviation forevaluations.FIG. 2 BandwidthE 1856 97 (2002)26.2.2.9 Investigate, identify, and correct, if necessary, thecause of any standard deviations of the results obtained by thecomputer which are more than two times the standard deviationof results obtained ma
31、nually.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 is usually indicative of a difference in calibra-tion. If maximum forces disagree between the m
32、anual andcomputerized results, it may be due to differences in calibrationbetween parts of the machine (see Appendix X1). If forceresults are in agreement and stress results vary, the differencemay be due to cross-sectional area or other measurements suchas span in a flexure test. If maximum force r
33、esults agree andother force results differ, the difference is probably not due todifferences in 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 or may not be observed if there is adiffere
34、nce in the speed of testing. A simple way to check thespeed of testing is to measure the elapsed time between twopoints during the tests.7.1.3 Incorrect Inputs to the Computer AlgorithmsIf theresults calculated by manual methods from the graphic recordagree with the other machines but the results fr
35、om thecomputer disagree, the difference may be due to incorrectinputs to the computer algorithms.7.1.4 Algorithms UsedIf the results calculated by manualmethods from the graphic record agree with the other machinesbut the results from the computer disagree, the difference maybe due to algorithms use
36、d by the computer 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 results from thecomputer disagree, the difference may be due to algorithmsthat are not working properly.7.1.6 Ambiguity in th
37、e 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 Differences in Gripping and Other Apparatus in Con-tact with the SpecimenDifferences in gripping and otherapparatus in contact with the s
38、pecimen 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 alignment cancause lower than normal test results or poorly formed stress-strain curves, or both, in the elastic region of the curve (seeP
39、ractice E 1012).7.1.9 Insufficient bandwidth in one or more of the trans-ducer channels (see Appendix X2).NOTE 8Differences are just as likely to be due to problems with themanually calculated results as they are to problems with the computergenerated results.NOTE 9For additional information, see th
40、e appendix on FactorsAffecting Tension Test Results in Test Methods E 8.7.2 A difference in the standard deviation between machinesmay be due to one or more of the following:7.2.1 Differences in ResolutionPoor resolution can showup in two forms. A standard deviation of zero may indicatepoor resoluti
41、on. Alternatively, if two or more discrete numericresults (derived data) occur with a difference between themwhich is large relative to the result being measured, poorresolution may be the cause. Example: 206, 206, 210, 206, 210(see Appendix X3).7.2.2 Specimen Dimension PrecisionIf derived-data forc
42、estandard deviations agree and derived-data stress standarddeviations differ, the difference is probably due to imprecisemeasurements of cross sectional area.7.2.3 Differences in the Speed of TestingTesting at speedsthat are too fast may give either high or low standard deviationsdue to one or more
43、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 derived data in strain-rate sensitive materials and causepoorly formed stress-strain curves and measurement errors inextreme c
44、ases.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 thegraphic record or in the basic data. This problem may bedetected by capturing data at a fixed force or strain. Thestandard d
45、eviation 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 Tes
46、t PiecePoor alignment is oftennot repeatable and leads to high standard deviations (seePractice E 1012).7.2.8 Insufficient band width in one or more of the trans-ducer channels (see Appendix X2).8. Report8.1 For each testing machine evaluated, report the followinginformation:8.1.1 Name of reporting
47、agency,8.1.2 Date of report,8.1.3 Complete testing machine description(s) including theserial number(s) of the machine(s), and all instrumentation, andthe location(s),8.1.4 Software version(s) identification,8.1.5 Graphic data and manually calculated test results, ifavailable,8.1.5.1 Computer test r
48、eport(s),8.1.5.2 Averages and standard deviations for each testresult,8.1.5.3 Tabulation of the differences observed, and8.1.6 Name(s) of reporting personnel.8.2 This report need only be performed once and need notbe repeated unless changes are made to the system whichwould significantly affect the
49、report.E 1856 97 (2002)38.2.1 Changes which can significantly affect the results ofthis report include, but are not limited to:8.2.1.1 Replacement of the indicating system with a differ-ent type of system,8.2.1.2 Software changes or modifications, and8.2.1.3 Changes to the computer(s) in the system whichaffect the processors speed.9. Precision and Bias9.1 The precision and bias of this guide for evaluatingcomputerized data acquisition systems on universal testingmachines is dependent upon the derived data being determined.Refer to the test method for the
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