ASTM E21-2017 red 1875 Standard Test Methods for Elevated Temperature Tension Tests of Metallic Materials《金属材料高温拉伸试验的标准试验方法》.pdf

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1、Designation: E21 09E21 17Standard Test Methods forElevated Temperature Tension Tests of Metallic Materials1This standard is issued under the fixed designation E21; the number immediately following the designation indicates the year of originaladoption or, in the case of revision, the year of last re

2、vision.Anumber in parentheses indicates the year of last reapproval.Asuperscriptepsilon () indicates an editorial change since the last revision or reapproval.This standard has been approved for use by agencies of the U.S. Department of Defense.1. Scope Scope*1.1 These test methods cover procedure a

3、nd equipment for the determination of tensile strength, yield strength, elongation, andreduction of area of metallic materials at elevated temperatures.1.2 Determination of modulus of elasticity and proportional limit are not included.1.3 Tension tests under conditions of rapid heating or rapid stra

4、in rates are not included.1.4 The values stated in inch-pound units are to be regarded as standard. The values given in parentheses are mathematicalconversions to SI units that are provided for information only and are not considered standard.1.5 This standard does not purport to address all of the

5、safety concerns, if any, associated with its use. It is the responsibilityof the user of this standard to establish appropriate safety safety, health, and healthenvironmental practices and determine theapplicability of regulatory limitations prior to use.1.6 This international standard was developed

6、 in accordance with internationally recognized principles on standardizationestablished in the Decision on Principles for the Development of International Standards, Guides and Recommendations issuedby the World Trade Organization Technical Barriers to Trade (TBT) Committee.2. Referenced Documents2.

7、1 ASTM Standards:2E4 Practices for Force Verification of Testing MachinesE6 Terminology Relating to Methods of Mechanical TestingE8/E8M Test Methods for Tension Testing of Metallic MaterialsE29 Practice for Using Significant Digits in Test Data to Determine Conformance with SpecificationsE74 Practic

8、e of Calibration of Force-Measuring Instruments for Verifying the Force Indication of Testing MachinesE83 Practice for Verification and Classification of Extensometer SystemsE177 Practice for Use of the Terms Precision and Bias in ASTM Test MethodsE220 Test Method for Calibration of Thermocouples By

9、 Comparison TechniquesE633 Guide for Use of Thermocouples in Creep and Stress-Rupture Testing to 1800F (1000C) in AirE691 Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method3. Terminology3.1 Definitions:3.1.1 Definitions of terms relating to tension testing w

10、hich appear in Terminology E6, shall apply to the terms used in this testmethod.3.1 Definitions of terms relating to tension testing which appear in Terminology E6, apply to this test method. These termsinclude alignment, axial strain, bending strain, gauge length, elongation, elongation after fract

11、ure, extensometer system, necking,reduction of area, tensile strength, yield strength. In addition, the definitions of the following terms relating to tension testing areincluded.1 These test methods are under the jurisdiction of ASTM Committee E28 on Mechanical Testing and are the direct responsibi

12、lity of Subcommittee E28.04 on UniaxialTesting.Current edition approved April 1, 2009Dec. 1, 2017. Published May 2009January 2018. Originally approved in 1933. Last previous edition approved in 20052009 asE21 05.E21 09. DOI: 10.1520/E0021-09.10.1520/E0021-17.2 For referencedASTM standards, visit the

13、ASTM website, www.astm.org, or contactASTM Customer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume information, refer to the standards Document Summary page on the ASTM website.This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an

14、indication of what changes have been made to the previous version. Becauseit 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 versionof the standard as published by ASTM is to

15、be considered the official document.*A Summary of Changes section appears at the end of this standardCopyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States13.2 Definitions of Terms Specific to This Standard:Definitions:3.2.1 reduced section

16、of the specimensectionthe central portion of the length having that has a cross section smaller thanthe ends which are gripped. The cross section is uniform within tolerances prescribed in gripped ends. 7.7.3.2.1.1 DiscussionThe cross section is uniform within prescribed tolerances.3.2.2 length of t

17、he reduced sectionthe distance between tangent points of the fillets whichthat bound the reduced section.3.2.3 adjusted length of the reduced section is greater than the length of the reduced section by an amount calculated tocompensate for strain in the fillet region (see 9.2.3).3.2.4 gage lengthth

18、e original distance between gage marks made on the specimen for determining elongation after fracture.3.2.5 axial strainthe average of the strain measured on opposite sides and equally distant from the specimen axis.3.2.6 bending strainthe difference between the strain at the surface of the specimen

19、 and the axial strain. In general it variesfrom point to point around and along the reduced section of the specimen.3.2.3 maximum bending strainadjusted length of the reduced sectionis the largest value of bending strain in length of thereduced section of the specimen. It can be calculated from meas

20、urements of strain at three circumferential positions at each of twodifferent longitudinal positions.plus an amount calculated to compensate for strain in the fillet region.4. Significance and Use4.1 The elevated-temperature tension test gives a useful estimate of the ability of metals to withstand

21、the application of appliedtensile forces. Using established and conventional relationships it can be used to give some indication of probable behavior underother simple states of stress, such as compression, shear, etc. The ductility values give a comparative measure of the capacity ofdifferent mate

22、rials to deform locally without cracking and thus to accommodate a local stress concentration or overstress; however,quantitative relationships between tensile ductility and the effect of stress concentrations at elevated temperature are not universallyvalid. A similar comparative relationship exist

23、s between tensile ductility and strain-controlled, low-cycle fatigue life under simplestates of stress. The results of these tension tests can be considered as only a questionable comparative measure of the strengthand ductility for service times of thousands of many hours. Therefore, the principal

24、usefulness of the elevated-temperature tensiontest is to assure that the tested material is similar to reference material when other measures such as chemical composition andmicrostructure also show the two materials are similar.5. Apparatus5.1 Testing Machine:5.1.1 The accuracy of the testing machi

25、ne shall be within the permissible variation specified in Practices E4.5.1.2 Precaution should be taken to assure that the force on the specimens is applied as axially as possible. Perfect axialalignment is difficult to obtain especially when the pull rods and extensometer rods pass through packing

26、at the ends of the furnace.However, the machine and grips should be capable of loading a precisely made specimen so that the maximum bending strain doesnot exceed 10 % of the axial strain, when the calculations are based on strain readings taken at zero force and at the lowest forcefor which the mac

27、hine is being qualified.NOTE 1This requirement is intended to limit the maximum contribution of the testing apparatus to the bending which occurs during a test. It isrecognized that even with qualified apparatus different tests may have quite different percent bending strain due to chance orientatio

28、n of a loosely fittedspecimen, lack of symmetry of that particular specimen, lateral force from furnace packing, and thermocouple wire, etc. The scant evidence availableat this time3 indicates that the effect of bending strain on test results is not sufficient, except in special cases, to require th

29、e measurement of this quantityon each specimen tested.5.1.2.1 In testing of brittle material even a bending strain of 10 % may result in lower strength than would be obtained withimproved axiality. In these cases, measurements of bending strain on the specimen to be tested may be specifically reques

30、ted andthe permissible magnitude limited to a smaller value.5.1.2.2 In general, equipment is not available for determining maximum bending strain at elevated temperatures. The testingapparatus may be qualified by measurements of axiality made at room temperature using the assembled machine, pull rod

31、s, andgrips used in high temperature testing. The specimen form should be the same as that used during the elevated-temperature testsand designed so that only elastic strains occur throughout the reduced section. This requirement may necessitate use of a materialdifferent from that used during the e

32、levated-temperature test. See Practice E1012 for recommended methods for determiningspecimen alignment.5.1.2.3 Gripping devices and pull rods may oxidize, warp, and creep with repeated use at elevated temperatures. Increasedbending stresses may result. Therefore, grips and pull rods should be period

33、ically retested for axiality and reworked whennecessary.3 Subcommittee E28.10 on Effect of Elevated Temperature on Properties requests factual information on the effect of nonaxiality of loading on test results.E21 1725.1.3 The testing machine shall be equipped with a means of measuring and controll

34、ing either the strain rate or the rate ofcrosshead motion or both to meet the requirements in 9.6.5.1.4 For high-temperature testing of materials that are readily attacked by their environment (such as oxidation of metal in air),the specimen may be enclosed in a capsule so that it can be tested in a

35、 vacuum or inert gas atmosphere. When such equipmentis used, the necessary corrections must be made to determine the actual forces seen by the specimen. For instance, compensationmust be made for differences in pressures inside and outside of the capsule and for any variation in the forces applied t

36、o thespecimen due to sealing ring friction, bellows or other features.5.2 Heating Apparatus:5.2.1 The apparatus for and method of heating the specimens should provide the temperature control necessary to satisfy therequirements specified in 9.4.5.2.2 Heating shall be by an electric resistance or rad

37、iation furnace with the specimen in air at atmospheric pressure unless othermedia are specifically agreed upon in advance.NOTE 2The media in which the specimens are tested may have a considerable effect on the results of tests.This is particularly true when the propertiesare influenced by oxidation

38、or corrosion during the test.5.3 Temperature-Measuring Apparatus:5.3.1 The method of temperature measurement must be sufficiently sensitive and reliable to ensure that the temperature of thespecimen is within the limits specified in 9.4.4.5.3.2 Temperature should be measured with thermocouples in co

39、njunction with the appropriate temperature indicatinginstrumentation.NOTE 3Such measurements are subject to two types of error. Thermocouple calibration and instrument measuring errors initially introduceuncertainty as to the exact temperature. Secondly both thermocouples and measuring instruments m

40、ay be subject to variation with time. Common errorsencountered in the use of thermocouples to measure temperatures include: calibration error, drift in calibration due to contamination or deterioration withuse, lead-wire error, error arising from method of attachment to the specimen, direct radiatio

41、n of heat to the bead, heat-conduction along thermocouplewires, etc.5.3.3 Temperature measurements should be made with thermocouples of known calibration. Representative thermocouplesshould be calibrated from each lot of wires used for making base-metal thermocouples. Except for relatively low tempe

42、ratures ofexposure, base-metal thermocouples are subject to error upon reuse, unless the depth of immersion and temperature gradients ofthe initial exposure are reproduced. Consequently base-metal thermocouples should be verified by the use of representativethermocouples and actual thermocouples use

43、d to measure specimen temperatures should not be verified at elevated temperatures.Base-metal thermocouples also should not be reused without clipping back to remove wire exposed to the hot zone and rewelding.Any reuse of base-metal thermocouples after relatively low-temperature use without this pre

44、caution should be accompanied byrecalibration data demonstrating that calibration was not unduly affected by the conditions of exposure.5.3.3.1 Noble metal thermocouples are also subject to errors due to contamination, etc., and should be periodically annealed andverified. Thermocouples should be ke

45、pt clean prior to exposure and during use at elevated temperatures.5.3.3.2 Measurement of the emf drift in thermocouples during use is difficult. When drift is a problem during tests, a methodshould be devised to check the readings of the thermocouples on the specimen during the test. For reliable c

46、alibration ofthermocouples after use the temperature gradient of the testing furnace must be reproduced during the recalibration.5.3.4 Temperature-measuring, controlling, and recording instruments should be verified periodically against a secondarystandard, such as a precision potentiometer and if n

47、ecessary re-calibrated. Lead-wire error should be checked with the lead wiresin place as they normally are used.5.4 Extensometer System:5.4.1 Practice E83, is recommended as a guide for selecting the required sensitivity and accuracy of extensometers. Fordetermination of offset yield strength at 0.1

48、 % or greater, a Class B-2 extensometer may be used. The extensometer should meetthe requirements of Practice E83 and should, in addition, be tested to assure its accuracy when used in conjunction with a furnaceat elevated temperature. One such test is to measure at elevated temperature the stress a

49、nd strain in the elastic range of a metalof known modulus of elasticity. Combinations of stress and temperature which will result in creep of the specimen during theextensometer system evaluation should be avoided.NOTE 4If an extensometer of Class B-2 or better is attached to the reduced section of the specimen, the section, the slope of the stress-strain curvewill usually be within 10 % of the modulus of elasticity.5.4.2 Non-axiality of loading is usually sufficient to cause significant errors at small strains when strain is measured on only oneside of the specim