1、Designation: E1319 98 (Reapproved 2014)Standard Guide forHigh-Temperature Static Strain Measurement1This standard is issued under the fixed designation E1319; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revisio
2、n. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This guide covers the selection and application of straingages for the measurement of static strain up to and includingthe tempera
3、ture range from 425 to 650C (800 to 1200F). Thisguide reflects some current state-of-the-art techniques in hightemperature strain measurement, and will be expanded andupdated as new technology develops.1.2 This guide assumes that the user is familiar with the useof bonded strain gages and associated
4、 signal conditioning andinstrumentation as discussed in (1) and (2).2The strainmeasuring systems described are those that have proveneffective in the temperature range of interest and were availableat the time of issue of this guide. It is not the intent of this guideto limit the user to one of the
5、gage types described nor is it theintent to specify the type of system to be used for a specificapplication. However, in using any strain measuring systemincluding those described, the proposer must be able todemonstrate the capability of the proposed system to meet theselection criteria provided in
6、 Section 5 and the needs of thespecific application.1.3 The devices and techniques described in this guide maybe applicable at temperatures above and below the range noted,and for making dynamic strain measurements at high tempera-tures with proper precautions. The gage manufacturer shouldbe consult
7、ed for recommendations and details of such appli-cations.1.4 The references are a part of this guide to the extentspecified in the text.1.5 The values stated in metric (SI) units are to be regardedas the standard. The values given in parentheses are forinformational purposes only.1.6 This standard d
8、oes not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM St
9、andards:3E6 Terminology Relating to Methods of Mechanical Testing3. Terminology3.1 Definitions:3.1.1 Refer to Terminology E6 for definitions of termsrelating to stress and strain.3.2 Definitions of Terms Specific to This Standard:3.2.1 Terms pertinent to this guide are described as follows:3.2.2 cap
10、acitive strain gagea strain gage whose responseto strain is a change in electrical capacitance which is predict-ably related to that strain.3.2.3 conditioning circuita circuit or instrument subsys-tem that applies excitation to a strain gage, detects an electricalchange in the strain gage, and provi
11、des a means for convertingthis change to an output that is related to strain in the testarticle.3.2.3.1 DiscussionThe conditioning circuit may includeone or more of the following: bridge completion circuit, signalamplification, zero adjustment, excitation adjustment,calibration, and gain (span) adju
12、stment.3.2.4 compensating gagea gage element that is subject tothe same environment as the active gage element, and which isplaced in the adjacent leg of a Wheatstone bridge to providethermal, pressure, or other compensation in the strain gagesystem.3.2.5 electrical simulationa method of calibration
13、whereby a known voltage is generated at the input of anamplifier, equivalent to the voltage produced by a specificamount of strain.3.2.6 free filament gagea resistive strain gage made froma continuous wire or foil filament which is fixed to the testarticle along the entire length of the gage, and wh
14、ich issupplied without a permanent matrix.1This guide is under the jurisdiction of ASTM Committee E28 on MechanicalTesting and is the direct responsibility of Subcommittee E28.01 on Calibration ofMechanical Testing Machines and Apparatus.Current edition approved April 15, 2014. Published August 2014
15、. Originallyapproved in 1989. Last previous edition approved in 2009 as E1319 - 98 (2009).DOI: 10.1520/E1319-98R14.2The boldface numbers in parentheses refer to the list of references at the end ofthis guide.3For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Custome
16、r 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 States13.2.7 gage factorthe ratio between the
17、unit change ofstrain gage resistance due to strain and the measurement.3.2.7.1 DiscussionThe gage factor is dimensionless and isexpressed as follows:K 5R 2 RoRo/L 2 LoLo5RRo/ (1)where:K = gage factor,R = strain gage resistance at test strain,Ro= strain gage resistance at zero or reference strain,L =
18、 test structure length under the strain gage at teststrain,Lo= test structure length under the strain gage at zero orreference strain,R = change in strain gage resistance when strain ischanged from zero (or reference strain) to test strain,and =mechanical strainL2LoLo3.2.8 integral lead wirea lead w
19、ire or portion of a leadwire that is furnished by a gage manufacturer as part of thegage assembly.3.2.9 linearitythe value measured as the maximum devia-tion between an actual instrument reading and the readingpredicted by a straight line drawn between upper and lowercalibration points, usually expr
20、essed as a percent of the fullscale of the sensor range.3.2.10 lead wirea conductor used to connect a sensor to itsinstrumentation.3.2.11 matrixan electrically nonconductive layer of mate-rial used to support a strain gage grid.3.2.11.1 Discussion The two main functions of a matrixare to act as an a
21、id for bonding the strain gage to a structure andas an electrically insulating layer in cases where the structureis electrically conductive.3.2.12 resistive strain gagea strain gage whose responseto strain is a change in electrical resistance that is predictablyrelated to that strain.3.2.13 shunt ca
22、librationa method of calibration wherebya resistor or capacitor of known value is placed electrically inparallel with another resistor or capacitor in a circuit, causinga calculable change in the total resistance or capacitance that ispredictably related to a specific amount of strain.3.2.14 strain,
23、 linearthe unit elongation induced in a speci-men either by a stress field (mechanical strain) or by atemperature change (thermal expansion).3.2.15 strain gage systemthe sum total of all componentsused to obtain a strain measurement.3.2.15.1 DiscussionMay include a strain gage; a means ofattaching t
24、he strain gage to the test articles; lead wires; splices;lead-wire attachments; signal-conditioning and read-out instru-mentation; data-logging system; calibration and control sys-tem; environmental protection; or any combination of theseand other elements required for the tests.3.2.16 static strain
25、a strain that is measured relative to aconstant reference value, as opposed to dynamic strain, whichis the peak-to-peak value of a cyclic phenomenon, withoutreference to a constant zero or reference value (Fig. 1).3.2.17 test articlean item to which a strain gage system isinstalled for the purpose o
26、f measuring strain in that item.3.2.18 thermal compensationthe process by which thethermal output of a gage system is counteracted through the useof one or more supplementary devices, such as a thermocoupleor compensating gage.3.2.18.1 DiscussionThe counteraction may be integral tothe gage system or
27、 may be accomplished by data processingmethods, or both.3.2.19 thermal outputthe reversible part of the tempera-ture induced indicated strain of a strain gage installed on anunrestrained test specimen when exposed to a change intemperature.3.2.20 thermal output-unmountedthe reversible part of thetem
28、perature induced indicated strain of an unmounted straingage when exposed to a change in temperature.4. Significance and Use4.1 The use of this guide is voluntary and is intended for useas a procedures guide for selection and application of specifictypes of strain gages for high-temperature installa
29、tions. Noattempt is made to restrict the type of strain gage types orconcepts to be chosen by the user. The provisions of this guidemay be invoked in specifications and procedures by specifyingthose which shall be considered mandatory for the purpose ofthe specific application. When so invoked, the
30、user shallinclude in the work statement a notation that provisions of thisguide shown as recommendation shall be considered manda-tory for the purposes of the specification or procedureconcerned, and shall include a statement of any exceptions toor modifications of the affected provisions of this gu
31、ide.5. Gage Selection Criteria5.1 The factors listed in this section must be consideredwhen selecting a strain gage system for use in the temperaturerange specified in 1.1. It is recognized that no gage may haveall of the desired capabilities to meet all requirements of aFIG. 1 Relationship Between
32、Static and Dynamic StrainE1319 98 (2014)2particular test. The risk of compromising certain test objectivesmust be evaluated, and some test objectives may have to bemodified to match the capabilities of the available gageselected. Guidelines for this evaluation are provided in Section9.5.2 Operating
33、Temperature:5.2.1 Isothermal TestsStability of the reference value withrespect to time is essential when tests are to be made atconstant temperature. The stability of the candidate gagesystem at the specified temperature must be such that any shiftthat occurs in the reference value is tolerable for
34、the durationof the test.5.2.2 Thermal Compensation and TransientsThe ad-equacy of the thermal compensation must be considered whenthe measurement of strain during a thermal transient is re-quired. Thermal output is a function of temperature, thus itsvalue at a temperature depends not only on tempera
35、ture, but onthe temperature history followed in reaching that temperature.If significant hysteresis in the thermal response is present, largeerrors or uncertainties can result. This is especially true whenthe calibration procedure used to characterize the thermaloutput does not accurately reflect th
36、e temperature sequence towhich the gages will be exposed during testing. If the responsetime of the compensation is exceeded, the resulting uncertaintymust be considered. The ability of the gage system to withstandthe transient without a detrimental shift of the reference valuemust be verified. This
37、 is true whether or not strain is measuredduring the transient. Any gage factor change as a function oftemperature change must also be considered.5.2.3 Precalibration:5.2.3.1 Thermal output calibration on the structure is usu-ally not possible and precalibration of gages on a similarmaterial is nece
38、ssary. However, variations of up to 0.5 ppm/Fare possible within a material. Often, rolling direction willinfluence thermal expansion coefficient.5.2.3.2 Precalibration of resistive or capacitive strain gagesis performed using a calibration fixture made from materialsimilar to the test article. The
39、calibration fixture must be madeto precisely fit the gage, especially if curvature is involved.Experience has shown mating parts must be lapped together toprovide uniform clamping pressure around the periphery of thegage weld area.5.2.3.3 The calibration test should be repeated to ensureprecise dupl
40、ication of the calibration. Zero return should alsorepeat exactly. If calibration data does not repeat; either thecalibration setup or the gages are faulty.5.2.4 Post Test Calibration:5.2.4.1 A more precise thermal output calibration can beachieved after the test by removing the test gage (cut it ou
41、t ofthe structure) and running a precision test on the test gage stillattached to the test article material. The test coupon is relievedof all induced stresses (thermal, mechanical, residual) and isfree to expand freely with temperature. The integral gage leadwire should be exposed to thermal gradie
42、nts similar to thosethat occurred during the test program.5.3 Duration of TestThe ability of all parts of the gagesystem to function for the specified duration of test should bedemonstrated; if multiple tests are required on the same testarticle, the capability and effect of gage replacement must al
43、sobe established.5.4 Strain RateThe time response of the candidate gagesystem must be adequate to meet test requirements if rapidchanges of load are anticipated. It may be necessary to designthe loading rate of the test to accommodate limitations of thestrain measurement system selected.5.5 Environm
44、entSome gages are limited to specific oper-ating environments and therefore, the gage system selectedmust be capable of withstanding the environment in which itwill operate. Such limitations must be carefully consideredwhen selecting the gage system to be used. Factors such aspressure, vibration, ra
45、diation, magnetic fields, humidity, etc.,must be considered. The ambient and test environments of theelements of the strain gage system must be considered in theselection of lead wires, connectors, instrumentation, and seals(when required).5.6 Strain Range:5.6.1 Total Strain RangeThe maximum strain
46、ranges ofthe candidate gage types must be defined and must be adequatefor the test. Mechanical strain attenuators, when permissible,may be added to extend the strain range of a given strain gagesystem, subject to the limitation of 5.6.2.5.6.2 ResolutionThe ability of the candidate gage tomeasure sma
47、ll increments of strain within the total strain rangeshould be compared with the incremental strain measurementrequirements of the test. When mechanical strain attenuatorsare used, the resulting loss of resolution must be considered.5.7 Strain GradientThe gage length of the candidate gageestablishes
48、 the length over which the unit strain is averaged.This factor must be considered.5.8 Uncertainty FactorUncertainty information that isavailable from the manufacturer must be considered, in con-junction with conditions which are unique to the test, in orderto estimate the total uncertainty.5.9 Space
49、 RequirementsIf space on or adjacent to the testarticle is limited, the space requirements for the complete straingage system may be a critical consideration in determining thesuitability of a particular gage system. Working space forinstallation of the system may also be limited and must also beconsidered. Space adjacent to the installed strain gage shouldbe provided for installation of room-temperature strain gagesrequired for making in-place calibrations.5.10 Effects of the Strain Gage on the Test ArticleIn mostcases the reinforcing effect
