ASTM E1319-98(2003)

Standard Guide for High-Temperature Static Strain Measurement

SIGNIFICANCE AND USE
The use of this guide is voluntary and is intended for use as a procedures guide for selection and application of specific types of strain gages for high-temperature installations. No attempt is made to restrict the type of strain gage types or concepts to be chosen by the user. The provisions of this guide may be invoked in specifications and procedures by specifying those which shall be considered mandatory for the purpose of the specific application. When so invoked, the user shall include in the work statement a notation that provisions of this guide shown as recommendation shall be considered mandatory for the purposes of the specification or procedure concerned, and shall include a statement of any exceptions to or modifications of the affected provisions of this guide.
SCOPE
1.1 This practice covers the selection and application of strain gages and associated instrumentation for the measurement of static strain up to and including the temperature range from 425 to 650°C (800 to 1200°F). This practice reflects some current state-of-the-art techniques in high temperature strain measurement, and will be expanded and updated as new technology develops.
1.2 This practice assumes that the user is familiar with the use of bonded strain gages and associated signal conditioning and instrumentation as discussed in Refs. (1) and (2). The strain measuring systems described are those that have proven effective in the temperature range of interest and were available at the time of issue of this practice. It is not the intent of this practice to limit the user to one of the gage types described nor is it the intent to specify the type of system to be used for a specific application. However, in using any strain measuring system including those described, the proposer must be able to demonstrate the capability of the proposed system to meet the selection criteria provided in Section 5 and the needs of the specific application.
1.3 The devices and techniques described in this practice may be applicable at temperatures above and below the range noted, and for making dynamic strain measurements at high temperatures with proper precautions. The gage manufacturer should be consulted for recommendations and details of such applications.
1.4 The references are a part of this practice to the extent specified in the text and Appendixes X1 through X5.
1.5 The values stated in metric (SI) units are to be regarded as the standard. The values given in parentheses are for information purposes only.
1.6 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 and health practices and determine the applicability of regulatory limitations prior to use.

General Information

• Status: Historical
• Publication Date: 09-May-1998
• Technical Committee: E28 - Mechanical Testing
• Drafting Committee: E28.01 - Calibration of Mechanical Testing Machines and Apparatus

Relations

• Replaces: ASTM E1319-98 - Standard Guide for High-Temperature Static Strain Measurement
• Effective Date: 10-May-1998
• Replaced By: ASTM E1319-98(2009) - Standard Guide for High-Temperature Static Strain Measurement
• Effective Date: 01-Apr-2009

Standards Content (Sample)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation:E1319–98 (Reapproved 2003)
Standard Guide for
High-Temperature Static Strain Measurement
This standard is issued under the fixed designation E1319; 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 (e) indicates an editorial change since the last revision or reapproval.
1. Scope 2. Referenced Documents
1.1 This guide covers the selection and application of strain 2.1 ASTM Standards:
gages for the measurement of static strain up to and including E6 Terminology Relating to Methods of Mechanical Test-
thetemperaturerangefrom425to650°C(800to1200°F).This ing
guide reflects some current state-of-the-art techniques in high
3. Terminology
temperature strain measurement, and will be expanded and
3.1 Definitions:
updated as new technology develops.
1.2 This practice assumes that the user is familiar with the 3.1.1 Refer to Terminology E6 for definitions of terms
relating to stress and strain.
use of bonded strain gages and associated signal conditioning
and instrumentation as discussed in Refs. (1) and (2). The 3.2 Definitions of Terms Specific to This Standard:
3.2.1 Terms pertinent to this guide are described as follows:
strain measuring systems described are those that have proven
effectiveinthetemperaturerangeofinterestandwereavailable 3.2.2 capacitive strain gage—a strain gage whose response
to strain is a change in electrical capacitance which is predict-
at the time of issue of this practice. It is not the intent of this
practicetolimittheusertooneofthegagetypesdescribednor ably related to that strain.
3.2.3 conditioning circuit—a circuit or instrument sub-
is it the intent to specify the type of system to be used for a
specific application. However, in using any strain measuring system that applies excitation to a strain gage, detects an
electrical change in the strain gage, and provides a means for
system including those described, the proposer must be able to
demonstrate the capability of the proposed system to meet the converting this change to an output that is related to strain in
the test article. The conditioning circuit may include one or
selection criteria provided in Section 5 and the needs of the
specific application. more of the following: bridge completion circuit, signal am-
plification, zero adjustment, excitation adjustment, calibration,
1.3 The devices and techniques described in this practice
and gain (span) adjustment.
may be applicable at temperatures above and below the range
noted, and for making dynamic strain measurements at high 3.2.4 compensating gage—a gage element that is subject to
thesameenvironmentastheactivegageelement,andwhichis
temperatures with proper precautions. The gage manufacturer
should be consulted for recommendations and details of such placed in the adjacent leg of a Wheatstone bridge to provide
thermal, pressure, or other compensation in the strain gage
applications.
1.4 The references are a part of this practice to the extent system.
3.2.5 electrical simulation—a method of calibration
specified in the text.
1.5 The values stated in metric (SI) units are to be regarded whereby a known voltage is generated at the input of an
amplifier, equivalent to the voltage produced by a specific
as the standard. The values given in parentheses are for
information purposes only. amount of strain.
3.2.6 free filament gage—a resistive strain gage made from
1.6 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the a continuous wire or foil filament which is fixed to the test
article along the entire length of the gage, and which is
responsibility of the user of this standard to establish appro-
priate safety and health practices and determine the applica- supplied without a permanent matrix.
3.2.7 gage factor—the ratio between the unit change of
bility of regulatory limitations prior to use.
strain gage resistance due to strain and the measurement. The
1 gage factor is dimensionless and is expressed as follows:
ThispracticeisunderthejurisdictionofASTMCommitteeE28onMechanical
Testing and is the direct responsibility of Subcommittee E28.01 on Calibration of
R 2 R L 2 L DR
o o
Mechanical Testing Machines and Apparatus. K 5 / 5 /e (1)
R L R
o o o
Current edition approved Nov. 15, 2005. Published January 2004. Originally
approved in 1989. Last previous edition approved in 1998 as E1319-98.
Theboldfacenumbersinparenthesesrefertothelistofreferencesattheendof
this practice. Annual Book of ASTM Standards, Vol 03.01.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
E1319–98 (2003)
where:
K = gage factor,
R = strain gage resistance at test strain,
R = strain gage resistance at zero or reference strain,
o
L = test structure length under the strain gage at test
strain,
L = test structure length under the strain gage at zero or
o
reference strain,
DR = change in strain gage resistance when strain is
changedfromzero(orreferencestrain)toteststrain,
and
e = L 2 L
o
mechanicalstrain
L
o
3.2.8 integral lead wire—a lead wire or portion of a lead
wire that is furnished by a gage manufacturer as part of the
gage assembly.
FIG. 1 Relationship Between Static and Dynamic Strain
3.2.9 linearity—thevaluemeasuredasthemaximumdevia-
tion between an actual instrument reading and the reading
3.2.19 thermal output—the reversible part of the tempera-
predicted by a straight line drawn between upper and lower
ture induced indicated strain of a strain gage installed on an
calibration points, usually expressed as a percent of the full
unrestrained test specimen when exposed to a change in
scale of the sensor range.
temperature.
3.2.10 lead wire—a conductor used to connect a sensor to
3.2.20 thermal output-unmounted—the reversible part of
its instrumentation.
the temperature induced indicated strain of an unmounted
3.2.11 matrix—an electrically nonconductive layer of ma-
strain gage when exposed to a change in temperature.
terial used to support a strain gage grid. The two main
functions of a matrix are to act as an aid for bonding the strain
4. Significance and Use
gage to a structure and as an electrically insulating layer in
4.1 Theuseofthisguideisvoluntaryandisintendedforuse
cases where the structure is electrically conductive.
as a procedures guide for selection and application of specific
3.2.12 resistive strain gage—a strain gage whose response
types of strain gages for high-temperature installations. No
to strain is a change in electrical resistance that is predictably
attempt is made to restrict the type of strain gage types or
related to that strain.
concepts to be chosen by the user.The provisions of this guide
3.2.13 shunt calibration—a method of calibration whereby
maybeinvokedinspecificationsandproceduresbyspecifying
a resistor or capacitor of known value is placed electrically in
parallel with another resistor or capacitor in a circuit, causing those which shall be considered mandatory for the purpose of
the specific application. When so invoked, the user shall
acalculablechangeinthetotalresistanceorcapacitancethatis
predictably related to a specific amount of strain. include in the work statement a notation that provisions of this
guide shown as recommendation shall be considered manda-
3.2.14 strain, linear—the unit elongation induced in a
tory for the purposes of the specification or procedure con-
specimen either by a stress field (mechanical strain) or by a
cerned, and shall include a statement of any exceptions to or
temperature change (thermal expansion).
modifications of the affected provisions of this guide.
3.2.15 strain gage system—the sum total of all components
usedtoobtainastrainmeasurement.Mayincludeastraingage;
5. Gage Selection Criteria
a means of attaching the strain gage to the test articles; lead
wires; splices; lead-wire attachments; signal-conditioning and 5.1 The factors listed in this section must be considered
read-out instrumentation; data-logging system; calibration and when selecting a strain gage system for use in the temperature
control system; environmental protection; or any combination range specified in 1.1. It is recognized that no gage may have
of these and other elements required for the tests. all of the desired capabilities to meet all requirements of a
3.2.16 static strain—a strain that is measured relative to a particulartest.Theriskofcompromisingcertaintestobjectives
constant reference value, as opposed to dynamic strain, which must be evaluated, and some test objectives may have to be
is the peak-to-peak value of a cyclic phenomenon, without modified to match the capabilities of the available gage
reference to a constant zero or reference value (Fig. 1). selected.GuidelinesforthisevaluationareprovidedinSection
3.2.17 test article—anitemtowhichastraingagesystemis 9.
installed for the purpose of measuring strain in that item. 5.2 Operating Temperature:
3.2.18 thermal compensation—the process by which the 5.2.1 IsothermalTests—Stabilityofthereferencevaluewith
thermaloutputofagagesystemiscounteractedthroughtheuse respect to time is essential when tests are to be made at
ofoneormoresupplementarydevices,suchasathermocouple constant temperature. The stability of the candidate gage
or compensating gage. The counteraction may be integral to system at the specified temperature must be such that any shift
the gage system or may be accomplished by data processing that occurs in the reference value is tolerable for the duration
methods, or both. of the test.
E1319–98 (2003)
5.2.2 Thermal Compensation and Transients—The ad- pressure, vibration, radiation, magnetic fields, humidity, etc.,
equacy of the thermal compensation must be considered when must be considered. The ambient and test environments of the
the measurement of strain during a thermal transient is re- elements of the strain gage system must be considered in the
quired. Thermal output is a function of temperature, thus its selection of lead wires, connectors, instrumentation, and seals
valueatatemperaturedependsnotonlyontemperature,buton (when required).
the temperature history followed in reaching that temperature. 5.6 Strain Range:
Ifsignificanthysteresisinthethermalresponseispresent,large
5.6.1 Total Strain Range—The maximum strain ranges of
errors or uncertainties can result. This is especially true when
thecandidategagetypesmustbedefinedandmustbeadequate
the calibration procedure used to characterize the thermal
for the test. Mechanical strain attenuators, when permissible,
output does not accurately reflect the temperature sequence to
may be added to extend the strain range of a given strain gage
whichthegageswillbeexposedduringtesting.Iftheresponse
system, subject to the limitation of 5.6.2.
timeofthecompensationisexceeded,theresultinguncertainty
5.6.2 Resolution—The ability of the candidate gage to
mustbeconsidered.Theabilityofthegagesystemtowithstand
measuresmallincrementsofstrainwithinthetotalstrainrange
the transient without a detrimental shift of the reference value
should be compared with the incremental strain measurement
must be verified.This is true whether or not strain is measured
requirements of the test. When mechanical strain attenuators
during the transient. Any gage factor change as a function of
are used, the resulting loss of resolution must be considered.
temperature change must also be considered.
5.7 Strain Gradient—Thegagelengthofthecandidategage
5.2.3 Precalibration:
establishes the length over which the unit strain is averaged.
5.2.3.1 Thermal output calibration on the structure is usu- This factor must be considered.
ally not possible and precalibration of gages on a similar
5.8 Uncertainty Factor—Uncertainty information that is
material is necessary. However, variations of up to 0.5 ppm/°F
available from the manufacturer must be considered, in con-
are possible within a material. Often, rolling direction will
junction with conditions which are unique to the test, in order
influence thermal expansion coefficient.
to estimate the total uncertainty.
5.2.3.2 Precalibration of resistive or capacitive strain gages
5.9 Space Requirements—If space on or adjacent to the test
is performed using a calibration fixture made from material articleislimited,thespacerequirementsforthecompletestrain
similar to the test article. The calibration fixture must be made
gage system may be a critical consideration in determining the
to precisely fit the gage, especially if curvature is involved. suitability of a particular gage system. Working space for
Experience has shown mating parts must be lapped together to
installationofthesystemmayalsobelimitedandmustalsobe
provideuniformclampingpressurearoundtheperipheryofthe considered. Space adjacent to the installed strain gage should
gage weld area.
be provided for installation of room-temperature strain gages
required for making in-place calibrations.
5.2.3.3 The calibration test should be repeated to ensure
precise duplication of the calibration. Zero return should also 5.10 Effects of the Strain Gage on the Test Article—In most
repeat exactly. If calibration data does not repeat; either the cases the reinforcing effect of the strain gage on the test article
calibration set-up or the gages are faulty. is negligible, particularly in the case of capacitance gages
wherethespringrateisextremelylow.Ifaweldablegageisto
5.2.4 Post Test Calibration:
beusedonthinsections,anevaluationofthereinforcingeffect
5.2.4.1 A more precise thermal output calibration can be
should be made. Technical data concerning this effect can be
achieved after the test by removing the test gage (cut it out of
obtained from a strain gage manufacturer.
the structure) and running a precision test on the test gage still
attached to the test article material.The test coupon is relieved
6. Characteristics of Available Gages
of all induced stresses (thermal, mecahniacl, residual) and is
free to expand freely with temperature. The integral gage lead
6.1 The two basic types of strain gages used for high
wire should be exposed to thermal gradients similar to those
temperature static strain measurements are resistive strain
that occurred during the test program.
gages and capacitive strain gages.
5.3 Duration of Test—The ability of all parts of the gage
6.1.1 Resistive gages are usually small, low profile units
system to function for the specified duration of test should be
superblysuitedfordynamicstrainmeasurementsandrelatively
demonstrated; if multiple tests are required on the same test
short-term static measurements. Because high temperature
...