1、Designation:E194903(Reapproved 2014)1Standard Test Method forAmbient Temperature Fatigue Life of Metallic BondedResistance Strain Gages1This standard is issued under the fixed designation E1949;the number immediately following the designation indicates the year oforiginal adoption or,in the case of
2、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.1NOTESection 7.2.1 and Footnote 3 were editorially corrected in August 2014.1.Scope1.1 This test method covers a
3、uniform procedure for thedetermination of strain gage fatigue life at ambient tempera-ture.A suggested testing equipment design is included.1.2 This test method does not apply to force transducers orextensometers that use bonded resistance strain gages assensing elements.1.3 Strain gages are part of
4、 a complex system that includesstructure,adhesive,gage,lead wires,instrumentation,and(often)environmental protection.As a result,many thingsaffect the performance of strain gages,including user tech-nique.A further complication is that strain gages,onceinstalled,normally cannot be reinstalled in ano
5、ther location.Therefore,it is not possible to calibrate individual strain gages;performance characteristics are normally presented on a statis-tical basis.1.4 This standard does not purport to address all of thesafety concerns,if any,associated with its use.It is theresponsibility of the user of thi
6、s standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to its use.2.Referenced Documents2.1 ASTM Standards:2E1237 Guide for Installing Bonded Resistance Strain Gages3.Terminology3.1 Definitions of Terms Specific to This Stand
7、ard:3.1.1 strain gage fatigue life,nthe number of fully re-versed strain cycles corresponding to the onset of degradedgage performance,whether due to excessive zero shift or otherdetectable failure mode(see 9.6).4.Significance and Use4.1 Strain gages are the most widely used devices formeasuring str
8、ains and for evaluating stresses in structures.Inmany applications there are often cyclic loads which can causestrain gage failure.Performance parameters of strain gages areaffected by both the materials from which they are made andtheir geometric design.4.2 The determination of most strain gage par
9、ameters re-quires mechanical testing that is destructive.Since gages testedfor fatigue life cannot be used again,it is necessary to treat datastatistically.In general,longer and wider gages with lowerresistances will have greater fatigue life.Optional additions togages(integral leads are an example)
10、will often reduce fatiguelife.4.3 To be used,strain gages must be bonded to a structure.Good results,particularly in a fatigue environment,dependheavily on the materials used to clean the bonding surface,tobond the gage,and to provide a protective coating.Skill of theinstaller is another major facto
11、r in success.Finally,instrumen-tation systems must be carefully selected and calibrated toensure that they do not unduly degrade the performance of thegages.4.4 This test method encompasses only fully reversed straincycles.4.5 Fatigue failure of a strain gage may not involve visiblecracking or fract
12、ure of the gage,but merely sufficient zero shiftto compromise the accuracy of the gage output for static straincomponents.5.Interferences5.1 In order to ensure that strain gage test data are within adefined accuracy,the gages must be properly bonded andprotected with acceptable materials.Aids in the
13、 strain gageinstallation and verification thereof can be found in GuideE1237.It is important to note that good performance in cyclicapplications requires the best installations possible.1This test method is under the jurisdiction of ASTM Committee E28 onMechanical Testing and is the direct responsib
14、ility of Subcommittee E28.01 onCalibration of Mechanical Testing Machines and Apparatus.Current edition approved April 1,2009.Published August 2014.Originallyapproved in 1998.Last previous edition approved in 2009 as E1949 03(2009).DOI:10.1520/E1949-03R14E01.2For referenced ASTM standards,visit the
15、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 State
16、s1 6.Hazards6.1 WarningIn the specimen surface cleaning,gagebonding,and protection steps of strain gage installations,hazardous chemicals are often employed.Users of these testmethods are responsible for contacting manufactures of suchchemicals for applicable Material Safety Data Sheets,and toadhere to the required precautions.7.Apparatus7.1 Test Measurement Requirements:7.1.1 For fatigue life determination the uncertainty of therelative resistance change measurement shall not exceed 65/or 60.1%
