1、Designation: G 163 99 (Reapproved 2004)Standard Guide forDigital Data Acquisition in Wear and Friction Measurements1This standard is issued under the fixed designation G 163; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year
2、 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 covers the providing of general guidance inapplying hardware and software to digitally acquire wear an
3、dfriction data in laboratory test systems. It points out importantconsiderations in such data acquisition. It does not makespecific recommendations or discuss specific details regardingcommercial hardware or software.1.2 This standard does not purport to address all of thesafety concerns, if any, as
4、sociated 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:2G 40 Terminology Relating to Erosion and WearG 77 Test
5、Method for Ranking Resistance of Materials toSliding Wear Using Block-on-Ring Wear TestG 83 Test Method for Wear Testing with a Crossed-CylinderApparatusG 99 Test Method for Wear Testing with a Pin-on-DiskApparatusG 115 Guide for Measuring and Reporting Friction Coeffi-cientsG 118 Guide for Recommen
6、ded Format of Wear Test DataSuitable for Databases3. Terminology3.1 Definitions:3.1.1 wear, ndamage to a surface, generally involvingprogressive loss of material, due to relative motion betweenthat surface and a contacting substance or substances.3.1.2 coeffcient of friction, nthe dimensionless rati
7、o ofthe friction force between two bodies to the normal forcepressing the bodies together.3.2 Definitions of Terms Specific to This Standard:3.2.1 hardware, nmechanical and electronic componentsin instrumentation used to acquire data.3.2.2 software, ncomputer code that can be executed tocontrol hard
8、ware systems and store data.4. Summary of Guide4.1 Several important issues relating to digital data acquisi-tion in wear and friction measurements are identified andexplained. Hardware and software choices are described ingeneral terms, along with some important considerations indata storage.5. Sig
9、nificance and Use5.1 The guide illustrates the steps and considerations in-volved with digital data acquisition. While analog recording ofwear and friction data has been customary in the field for sometime, a trend of increasing use of digital methods is nowapparent.5.2 Multi-station wear and fricti
10、on testing is increasing inuse, and because of the increased volume of data in suchapproaches, the use of digital data acquisition facilitates suchtesting.5.3 The same hardware and software used for the initialanalog data conversion to digital form can often also be usedfor initial data processing,
11、for example, multiple-point averag-ing. This can conveniently lead to computer-based storage ofprocessed data in digital form.5.4 Databases are frequently constructed in computerizedformat (see Guide G 118) in order to hold large amounts ofwear and friction data from laboratory test programs.6. Hard
12、ware and Software6.1 HardwareNecessary electronic components associ-ated with the wear test system include sensors (for example,force transducers, strain gages, linear variable differentialtransformers), a data acquisition system (for example, analogsignal conditioners, filters, analog-to-digital co
13、nvertors, otherelectronic circuits), a controlling computer, and a digital data1This guide is under the jurisdiction of ASTM Committee G02 on Wear andErosion and is the direct responsibility of Subcommittee G02.20 on Computeriza-tion in Wear and Erosion.Current edition approved Nov 1, 2004. Publishe
14、d November 2004. Originallyapproved in 1999. Last previous edition approved in 1999 as G 163 99.2For 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 Docume
15、nt Summary page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.storage device. These items can be bought commercially, orconstructed specifically for the task (1-3).6.2 Data Acquisition SystemTypically consists of
16、 an elec-tronic amplifier/filter system that receives and conditionssensor data, and whose output is fed to a scanning ormultiplexing circuit designed to handle multiple inputs. Sys-tems are commercially available to read voltage, current, orresistance. The analog signals are then digitized in a dat
17、aconvertor and sent to temporary or permanent storage in digitalform, possibly after pre-processing the digital data. The systemcan be either of a stand-alone design or in the form of printedcircuit cards that reside in the controlling computer (2, 3).6.3 Analog-to-Digital Convertor Resolution andAc
18、curacyPresent technology typically offers either 12 bit or16 bit data conversion, with 61 least significant digit as theusual resolution, and over a voltage range of typically 65Vor610 V. It is important to match the selected resolution to eachapplication. For example 12 bit resolution involves 1 pa
19、rt in4096 resolution. For a full scale of 65 V, the voltage resolutionwould be 2.4 mV. This may be sufficient for an amplified signalof 1 or 2 V level, but might be insufficient for a signal level aslow as 0.1 V. Such resolution would be clearly insufficient forraw thermocouple signals of a few mV.
20、Accuracy of dataconversion is usually maintained by self-calibrating electronicfeatures that are built-in to the hardware. However, it isrecommended that manual voltage calibration also be doneperiodically to ensure against any electronic component drift orfailure.6.4 SoftwareNecessary software incl
21、udes code that oper-ates the data acquisition system, as well as code that operatesthe computer and necessary peripherals.6.4.1 Source of SoftwareUsually commercial software isobtained to operate the controlling computer. Vendors of digitaldata acquisition hardware usually offer modular software cod
22、esthat can be assembled together to carry out many measurementoperations. The user can usually configure that software to suithis needs, and may be able to add self-written code to furtheradapt the overall software, if necessary.7. Procedure7.1 Sampling Rate and Number of ChannelsInformationtheory r
23、ecommends sampling a waveform at a rate of 10 timesthe highest frequency present, in order to accurately recon-struct the waveform. In practical terms, the factor may bereduced to three times that of the highest significant frequencyin the data. For multi-channel systems, the overall samplingrate mu
24、st be increased in proportion to the number of channelsscanned. As an example, fora0to10Hzbandwidth signal anda data convertor set to scan five channels, the recommendedoverall sampling rate is 500 Hz (that is, each recommendedchannel sampling rate is 10310=100 Hz). Many wear testsystems involve a m
25、echanical rotation frequency that is presentto some degree in the sensor output signals. For example, in apin-on-disk system, a disk rotating at 60 RPM could inject a 1Hz component into a friction force transducer output, usuallydue to lack of flatness or misalignment of the disk. As a result,ideall
26、y a one channel system should scan at least at 10 Hz (ora five channel system at 50 Hz) to accurately record that effect.7.2 Electronic NoiseSpurious signals may appear alongwith sensor outputs as a result of electronic interference. Theinterference frequencies may be related to ac voltage supply or
27、characteristic signals of other equipment. Such noise signalsmay seriously complicate proper data acquisition. An oscillo-scope may be used to help identify interfering signals. It isrecommended that proper shielding of signal leads, minimizingof lead length, and proper grounding, all be practiced t
28、o a highlevel to avoid problems with data validity later. Good analogsignals must be available through proper conditioning beforedigital conversion is attempted. Low pass filtering of theanalog signal may be required to improve its quality.7.3 CalibrationOverall system calibration includes volt-age
29、calibration at sensor input levels, and sensor calibrationusing directly applied force, temperature, and so forth. Ideally,some partial calibration is applied on every separate occasionof use of the system, and for unusually long tests, even at someintervals during the test. Complete system calibrat
30、ion shouldbe done at some suitable interval such as monthly or quarterly.Calibration should involve input levels close to that normallyexperienced, and also somewhat larger levels. Calibrationshould be done under conditions close to those of usual systemoperation. Any deviations from linearity that
31、exist for any partof the measuring system should be determined, and correctionsto the data applied as needed.7.4 Data StorageUsually, the data stream is accumulatedin the controlling computer memory, and periodically trans-ferred to an associated hard disk storage system in the form ofa text file. I
32、n some cases, the data are automatically placed intoa spreadsheet file (a row versus column organization) by theoperating software. In other cases, the data file can at a latertime be loaded into a database or spreadsheet. The organizationof the data file is important to the extent that necessarydes
33、criptors of the test are saved. Guide G 118 should beconsulted for assistance in deciding on the database format,along with the Report section in any standard that applies to thetest involved.7.5 Data Reduction On-lineAn important advantage ofdigital data acquisition is that it gives the capability
34、to carry outonline data reduction to reduce the volume of data to be stored.This can be done using simple smoothing algorithms whichperform a running average or other similar function to yieldaverage values of the different parameters which are thenstored in a datafile for the test. More sophisticat
35、ed algorithmscan also be used which have the ability to adjust the datareduction and storage rate to reflect the speed of changes in thedata. This type of analysis, often termed adaptive storage, isuseful for situations where the data values are steady for longperiods with intervals where the data c
36、hange quickly. In allcases where online data reduction is used, it is important toensure that the strategy employed will retain all essentialfeatures of the data.8. Report8.1 Wear TestingExamples of wear testing methods thathave been followed using digital data acquisition systemsinclude block-on-ri
37、ng (Practice G 77), crossed cylinder (TestMethod G 83), and pin-on-disk (Test Method G 99) (4,5).Other ASTM wear tests may also lend themselves to thatG 163 99 (2004)2approach. In these three cases cited, there was no conflict withany requirements in those standards. Sensors may be added tothose tes
38、t rigs to measure, for example, wear displacement,normal load, temperature, background vibration amplitudes,and frequencies, and so forth, without concern over conflictingwith the standard requirements. Actually, such additionalmeasures have merit as they further describe the wear condi-tions being
39、applied in the test.8.2 Friction TestingSeveral friction testing rigs men-tioned in Guide G 115 have been instrumented for digital dataacquisition. Most of the considerations mentioned in theprevious section also apply in friction measurements.9. Keywords9.1 data acquisition; database; digital data;
40、 friction; hard-ware; software; tribology; wearREFERENCES(1) Computer-Aided Experimentation: Interfacing to Minicomputers,Finkel, J., Wiley-Interscience, New York, 1975.(2) Analog-to-Digital Conversion: A Practical Approach, Daugherty, K.M., McGraw-Hill, NY, 1995.(3) Analog-to-Digital and Digital-to
41、-Analog Conversion Techniques,D.F.Hoeschele, Jr. D. F., J. Wiley, NY, 1994.(4) “A Computer-controlled Test System for Operating Different WearTest Machines,” Whitenton, E. P., and Ruff, A. W., NISTIR 89-4107,1989.(5) “Signal Processing Techniques for Friction Measurement,” Chen Z.and Liu, P. in pres
42、s (1997).ASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentionedin this standard. Users of this standard are expressly advised that determination of the validity of any such patent rights, and the riskof infringement of such ri
43、ghts, are entirely their own responsibility.This standard is subject to revision at any time by the responsible technical committee and must be reviewed every five years andif not revised, either reapproved or withdrawn. Your comments are invited either for revision of this standard or for additiona
44、l standardsand should be addressed to ASTM International Headquarters. Your comments will receive careful consideration at a meeting of theresponsible technical committee, which you may attend. If you feel that your comments have not received a fair hearing you shouldmake your views known to the AST
45、M Committee on Standards, at the address shown below.This standard is copyrighted by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959,United States. Individual reprints (single or multiple copies) of this standard may be obtained by contacting ASTM at the aboveaddress or at 610-832-9585 (phone), 610-832-9555 (fax), or serviceastm.org (e-mail); or through the ASTM website(www.astm.org).G 163 99 (2004)3
