ASTM_E_2208_-_02_2018e1.pdf

Designation:E220802(Reapproved 2018)1Standard Guide forEvaluating Non-Contacting Optical Strain MeasurementSystems1This standard is issued under the fixed designation E2208;the number immediately following the designation indicates the year oforiginal adoption or,in the case 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.1NOTE3.1.2 was editorially revised in June 2018.1.Scope1.1 The purpose of this document is to assist potential usersin understanding the issues related to the accuracy of non-contacting strain measurement systems and to provide acommon framework for quantitative comparison of opticalsystems.The output from a non-contacting optical strain anddeformation measurement system is generally divided intooptical data and image analysis data.Optical data containsinformation related to specimen strains and the image analysisprocess converts the encoded optical information into straindata.The enclosed document describes potential sources oferror in the strain data and describes general methods forquantifying the error and estimating the accuracy of themeasurements when applying non-contacting methods to thestudy of events for which the optical integration time is muchsmaller than the inverse of the maximum temporal frequency inthe encoded data(that is,events that can be regarded as staticduring the integration time).A brief application of theapproach,along with specific examples defining the variousterms,is given in the Appendix.1.2 This international standard was developed in accor-dance with internationally recognized principles on standard-ization established in the Decision on Principles for theDevelopment of International Standards,Guides and Recom-mendations issued by the World Trade Organization TechnicalBarriers to Trade(TBT)Committee.2.Referenced Documents2.1 ASTM Standards:2E8 Test Methods for Tension Testing of Metallic MaterialsE83 Practice for Verification and Classification of Exten-someter SystemsE251 Test Methods for Performance Characteristics of Me-tallic Bonded Resistance Strain GagesE399 Test Method for Linear-Elastic Plane-Strain FractureToughness KIcof Metallic MaterialsE1823 Terminology Relating to Fatigue and Fracture Testing3.Terminology3.1 Definitions:3.1.1 accuracythe quantitative difference between a testmeasurement and a reference value.3.1.2 raw datathe sampled values of a sensor output.3.2 Definitions of Terms Specific to This Standard:3.2.1 coherent illuminationlight source where the differ-ence in phase is solely a function of optical path differences;interference is a direct consequence.3.2.2 decoded datameasurement information related tothe displacement or displacement gradient field.3.2.3 decoded data bandwidthspatial frequency range ofthe information after decoding of the optical data.3.2.4 derived datadata obtained through processing of theraw data.3.2.5 dynamic rangethe range of physical parameter val-ues for which measurements can be acquired with the mea-surement system.3.2.6 illumination wavelengthwavelength of illumination,.3.2.7 incoherent illuminationlight source with randomvariations in optical path differences;constructive or destruc-tive interference of waves is not possible.3.2.8 maximum temporal frequency of encoded datareciprocal of the shortest event time contained in the encodeddata(for example,time variations in displacement field).3.2.9 measurement noisevariations in the measurementsthat are not related to actual changes in the physical propertybeing measured.May be quantified by statistical propertiessuch as standard deviation.1This guide is under the jurisdiction of ASTM Committee E08 on Fatigue andFracture and is the direct responsibility of Subcommittee E08.03 on AdvancedApparatus and Techniques.Current edition approved May 1,2018.Published June 2018.Originallyapproved in 2002.Last previous edition approved in 2010 as E220802(2010)1.DOI:10.1520/E2208-02R18E01.2For 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.Copyright 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 Decision on Principles for theDevelopment of International Standards,Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade(TBT)Committee.1 3.2.10 measurement resolutionsmallest change in thephysical property that can be reliably measured.3.2.11 numerical aperture,(N.A.)non-dimensional mea-sure of diffraction-limitation for imaging system;N.A.=D/ffor a simple lens system,where D is lens diameter and f is lensfocal length.3.2.12 optical datar