ASTM E1949-21

Standard Test Method for Ambient Temperature Fatigue Life of Metallic Bonded Resistance Strain Gages

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 that can cause strain gage failure. Performance characteristics 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 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 have greater fatigue life. Optional additions to strain gages (integral lead wires are an example) will often reduce fatigue life.  
4.3 To be used, strain gages must be bonded to a structure. Good results, particularly in a fatigue environment, depend heavily on the materials used to clean the bonding surface, to bond the strain gage, and to provide a protective coating. Skill of the installer is another major factor in success. Finally, instrumentation systems shall be carefully selected and calibrated to ensure that they do not unduly degrade the performance of the strain gages.  
4.4 Fatigue failure of a strain gage often does not involve visible cracking or fracture of the strain gage, but merely sufficient zero shift to compromise the accuracy of the strain gage output for static strain components.
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, health, and environmental practices and determine the applicability of regulatory limitations prior to 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.

General Information

• Status: Published
• Publication Date: 31-Jan-2021
• ICS: 19.060 - Mechanical testing
• Technical Committee: E28 - Mechanical Testing
• Drafting Committee: E28.01 - Calibration of Mechanical Testing Machines and Apparatus

Relations

• Refers: ASTM E1237-20 - Standard Guide for Installing Bonded Resistance Strain Gages
• Effective Date: 15-Aug-2020

Standards Content (Sample)

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.
Designation: E1949 − 21
Standard Test Method for
Ambient Temperature Fatigue Life of Metallic Bonded
1
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.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope* 2. Referenced Documents
2
2.1 ASTM Standards:
1.1 This test method covers a uniform procedure for the
E6Terminology Relating to Methods of Mechanical Testing
determination of strain gage fatigue life at ambient tempera-
E1237Guide for Installing Bonded Resistance Strain Gages
ture. A suggested testing equipment design is included.
1.2 This test method does not apply to force transducers or 3. Terminology
extensometers that use metallic bonded resistance strain gages
3.1 Definitions of terms common to mechanical testing:
as sensing elements.
3.1.1 The terms accuracy, extensometer, gage factor, lead
wire,metallicbondedresistancestraingage,andresolutionare
1.3 Strain gages are part of a complex system that includes
used as defined in Terminology E6.
structure, adhesive, strain gage, lead wires, instrumentation,
3.2 Definitions of Terms Specific to This Standard:
and (often) environmental protection.As a result, many things
3.2.1 strain gage, n—the term “strain gage” is equivalent to
affect the performance of strain gages, including user tech-
the longer, but more accurate, “metallic bonded resistance
nique. A further complication is that strain gages, once
strain gage.”
installed, normally cannot be reinstalled in another location.
Therefore,itisnotpossibletocalibrateindividualstraingages;
3.2.2 strain gage fatigue life, n—the number of fully re-
performance characteristics are normally presented on a statis-
versed strain cycles corresponding to the onset of degraded
tical basis. gage performance, whether due to excessive zero shift or other
detectable failure mode (see 9.6).
1.4 This test method encompasses only fully reversed stain
cycles.
4. Significance and Use
1.5 This standard does not purport to address all of the
4.1 Strain gages are the most widely used devices for
safety concerns, if any, associated with its use. It is the
measuring strains and for evaluating stresses in structures. In
responsibility of the user of this standard to establish appro-
many applications there are often cyclic loads that can cause
priate safety, health, and environmental practices and deter-
strain gage failure. Performance characteristics of strain gages
mine the applicability of regulatory limitations prior to use.
are affected by both the materials from which they are made
and their geometric design.
1.6 This international standard was developed in accor-
dance with internationally recognized principles on standard-
4.2 The determination of most strain gage performance
ization established in the Decision on Principles for the
characteristics requires mechanical testing that is destructive.
Development of International Standards, Guides and Recom-
Since strain gages tested for fatigue life cannot be used again,
mendations issued by the World Trade Organization Technical
it is necessary to treat data statistically. In general, longer and
Barriers to Trade (TBT) Committee.
wider strain gages with lower resistances will have greater
fatigue life. Optional additions to strain gages (integral lead
wires are an example) will often reduce fatigue life.
4.3 To be used, strain gages must be bonded to a structure.
Good results, particularly in a fatigue environment, depend
heavily on the materials used to clean the bonding surface, to
1
This test method is under the jurisdiction of ASTM Committee E28 on
Mechanical Testing and is the direct responsibility of Subcommittee E28.01 on
2
Calibration of Mechanical Testing Machines and Apparatus. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Current edition approved Feb. 1, 2021. Published March 2021. Originally contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
ɛ1
approved in 1998. Last previous edition approved in 2014 as E1949–03(2014) . Standards volume information, refer to the standard’s Document Summary page on
DOI: 10.1520/E1949-21. the ASTM website.
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
1

---------------------- Page: 1 ----------------------
E1949 − 21
bond the strain gage, and to provide
...

This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
´1
Designation: E1949 − 03 (Reapproved 2014) E1949 − 21
Standard Test Method for
Ambient Temperature Fatigue Life of Metallic Bonded
1
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.
1
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
2
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:
1
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
ɛ1
E1949 – 03(2009).(2014) . DOI: 10.1520/E1949-03R14E01.10.1520/E1949-21.
2
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at [e-mail]. 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
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
1

---------------------- Page: 1 ----------------------
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
...