ASTM E1949-21

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Designation: E1949 − 03 (Reapproved 2014) E1949 − 21
Standard Test Method for
Ambient Temperature Fatigue Life of Metallic Bonded
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Resistance Strain Gages
This standard is issued under the fixed designation E1949; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
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ε NOTE—Section 7.2.1 and Footnote 3 were editorially corrected in August 2014.
1. Scope Scope*
1.1 This test method covers a uniform procedure for the determination of strain gage fatigue life at ambient temperature. A
suggested testing equipment design is included.
1.2 This test method does not apply to force transducers or extensometers that use metallic bonded resistance strain gages as
sensing elements.
1.3 Strain gages are part of a complex system that includes structure, adhesive, strain gage, lead wires, instrumentation, and (often)
environmental protection. As a result, many things affect the performance of strain gages, including user technique. A further
complication is that strain gages, once installed, normally cannot be reinstalled in another location. Therefore, it is not possible
to calibrate individual strain gages; performance characteristics are normally presented on a statistical basis.
1.4 This test method encompasses only fully reversed stain cycles.
1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility
of the user of this standard to establish appropriate safety safety, health, and healthenvironmental practices and determine the
applicability of regulatory limitations prior to its use.
1.6 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
2. Referenced Documents
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2.1 ASTM Standards:
E6 Terminology Relating to Methods of Mechanical Testing
E1237 Guide for Installing Bonded Resistance Strain Gages
3. Terminology
3.1 Definitions of terms common to mechanical testing:
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This test method is under the jurisdiction of ASTM Committee E28 on Mechanical Testing and is the direct responsibility of Subcommittee E28.01 on Calibration of
Mechanical Testing Machines and Apparatus.
Current edition approved April 1, 2009Feb. 1, 2021. Published August 2014March 2021. Originally approved in 1998. Last previous edition approved in 20092014 as
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E1949 – 03(2009).(2014) . DOI: 10.1520/E1949-03R14E01.10.1520/E1949-21.
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For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
*A Summary of Changes section appears at the end of this standard
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E1949 − 21
3.1.1 The terms accuracy, extensometer, gage factor, lead wire, metallic bonded resistance strain gage, and resolution are used
as defined in Terminology E6.
3.2 Definitions of Terms Specific to This Standard:
3.2.1 strain gage, n—the term “strain gage” is equivalent to the longer, but more accurate, “metallic bonded resistance strain
gage.”
3.2.2 strain gage fatigue life, n—the number of fully reversed strain cycles corresponding to the onset of degraded gage
performance, whether due to excessive zero shift or other detectable failure mode (see 9.6).
4. Significance and Use
4.1 Strain gages are the most widely used devices for measuring strains and for evaluating stresses in structures. In many
applications there are often cyclic loads whichthat can cause strain gage failure. Performance parameterscharacteristics of strain
gages are affected by both the materials from which they are made and their geometric design.
4.2 The determination of most strain gage parameters performance characteristics requires mechanical testing that is destructive.
Since strain gages tested for fatigue life cannot be used again, it is necessary to treat data statistically. In general, longer and wider
strain gages with lower resistances will ha
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