ASTM E21-92(1998)e1
(Test Method)Standard Test Methods for Elevated Temperature Tension Tests of Metallic Materials
Standard Test Methods for Elevated Temperature Tension Tests of Metallic Materials
SCOPE
1.1 These test methods cover procedure and equipment for the determination of tensile strength, yield strength, elongation, and reduction of area of metallic materials at elevated temperatures.
1.2 Determination of modulus of elasticity and proportional limit are not included. A method for static determination of modulus of elasticity at elevated temperatures is given in Method E231.
1.3 Tension tests under conditions of rapid heating or rapid strain rates are not included. Recommended practice for these tests is given in Practice E151.
1.4 The values stated in inch-pound units are to be regarded as the standard.
1.5 This standard does not purport to address all of the safety problems, 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.
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e1
Designation: E 21 – 92 (Reapproved 1998)
Standard Test Methods for
Elevated Temperature Tension Tests of Metallic Materials
This standard is issued under the fixed designation E 21; 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 (e) indicates an editorial change since the last revision or reapproval.
This standard has been approved for use by agencies of the Department of Defense.
e NOTE—Sections 9.4.4 and 9.4.6 were editorially updated in January 2002.
1. Scope Elevated Temperatures with Rapid Heating and Conven-
tional or Rapid Strain Rates
1.1 These test methods cover procedure and equipment for
E 177 Practice for Use of the Terms Precision and Bias in
the determination of tensile strength, yield strength, elongation,
ASTM Test Methods
and reduction of area of metallic materials at elevated tempera-
E 220 Method for Calibration of Thermocouples by Com-
tures.
parison Techniques
1.2 Determination of modulus of elasticity and proportional
E 231 Method for Static Determination of Young’s Modu-
limit are not included. A method for static determination of
lus of Metals at Low and Elevated Temperatures
modulus of elasticity at elevated temperatures is given in
E 691 Practice for Conducting an Interlaboratory Study to
Method E 231.
Determine the Precision of a Test Method
1.3 Tension tests under conditions of rapid heating or rapid
strain rates are not included. Recommended practice for these
3. Terminology
tests is given in Practice E 151.
3.1 Definitions:
1.4 The values stated in inch-pound units are to be regarded
3.1.1 Definitions of terms relating to tension testing which
as the standard.
appear in Terminology E 6, shall apply to the terms used in this
1.5 This standard does not purport to address all of the
test method.
safety concerns, if any, associated with its use. It is the
3.2 Definitions of Terms Specific to This Standard: Defini-
responsibility of the user of this standard to establish appro-
tions of Terms Specific to This Standard:
priate safety and health practices and determine the applica-
3.2.1 reduced section of the specimen—the central portion
bility of regulatory limitations prior to use.
of the length having a cross section smaller than the ends which
2. Referenced Documents are gripped. The cross section is uniform within tolerances
prescribed in 7.7.
2.1 ASTM Standards:
3.2.2 length of the reduced section—the distance between
E 4 Practices for Force Verification of Testing Machines
tangent points of the fillets which bound the reduced section.
E 6 Terminology Relating to Methods of Mechanical Test-
3.2.3 adjusted length of the reduced section is greater than
ing
the length of the reduced section by an amount calculated to
E 8 Test Methods for Tension Testing of Metallic Materials
compensate for strain in the fillet region (see 9.2.3).
E 29 Practice for Using Significant Digits in Test Data to
3.2.4 gage length—the original distance between gage
Determine Conformance with Specification
marks made on the specimen for determining elongation after
E 74 Practice for Calibration of Force Measuring Instru-
fracture.
ments for Verifying the Force Indication of Testing Ma-
2 3.2.5 axial strain—the average of the strain measured on
chines
opposite sides and equally distant from the specimen axis.
E 83 Practice for Verification and Classification of Exten-
2 3.2.6 bending strain—the difference between the strain at
someters
the surface of the specimen and the axial strain. In general it
E 151 Practice for Tension Tests of Metallic Materials at
varies from point to point around and along the reduced section
of the specimen.
3.2.7 maximum bending strain—the largest value of bend-
These test methods are under the jurisdiction of ASTM Committee E28 on
Mechanical Testing and are the direct responsibility of Subcommittee E28.10 on
ing strain in the reduced section of the specimen. It can be
Effect of Elevated Temperature on Properties.
Current edition effective Aug. 15, 1992. Published October 1992. Originally
2 4
published as E 21 – 33. Last previous edition E 21 – 79 (1988)e . Discontinued, see 1983 Annual Book of ASTM Standards, Vol 03.01.
2 5
Annual Book of ASTM Standards, Vol 03.01. Annual Book of ASTM Standards, Vol 14.03.
3 6
Annual Book of ASTM Standards, Vol 14.02. Discontinued, see 1985 Annual Book of ASTM Standards, Vol 03.01.
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NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
E21
calculated from measurements of strain at three circumferential testing apparatus may be qualified by measurements of axiality
positions at each of two different longitudinal positions. made at room temperature. When one is making axiality tests
of equipment, the specimen form should be the same as that
4. Significance and Use
used during the elevated-temperature tests. The specimen
concentricity should be as near perfect as reasonably possible.
4.1 The elevated-temperature tension test gives a useful
Only elastic strains should occur throughout the reduced
estimate of the static load-carrying capacity of metals under
section. This requirement may necessitate use of a material
short-time, tensile loading. Using established and conventional
different from that used during the elevated-temperature test.
relationships it can be used to give some indication of probable
5.1.2.3 Strain measurements at each longitudinal position
behavior under other simple states of stress, such as compres-
may be made by the use of four electrical-resistance strain
sion, shear, etc. The ductility values give a comparative
gages equally spaced around the test section of specimens of
measure of the capacity of different materials to deform locally
circular cross section. The two longitudinal positions should be
without cracking and thus to accommodate a local stress
as far apart as is convenient but not closer than one diameter to
concentration or overstress; however, quantitative relationships
a fillet.
between tensile ductility and the effect of stress concentrations
5.1.2.4 For specimens of rectangular cross section, strain
at elevated temperature are not universally valid. A similar
measurements may be made in the center of each of the four
comparative relationship exists betweentensile ductility and
sides, or in the case of thin strip, near the outer edges of each
strain-controlled, low-cycle fatigue life under simple states of
of the two broad sides.
stress. The results of these tension tests can be considered as
5.1.2.5 To eliminate the effect of specimen bias the test
only a questionable comparative measure of the strength and
should be repeated with the specimen turned 180° and the grips
ductility for service times of thousands of hours. Therefore, the
and pull rods retained in their original position. The maximum
principal usefulness of the elevated-temperature tension test is
bending strain and strain at the specimen axis are then
to assure that the tested material is similar to reference material
calculated from the average of the two readings at the same
when other measures such as chemical composition and
position relative to the machine.
microstructure also show the two materials are similar.
5.1.2.6 Axiality measurements should be made at room
5. Apparatus
temperature on the assembled machine, pull rods, and grips
before use for testing. Gripping devices and pull rods may
5.1 Testing Machine:
oxidize, warp, and creep with repeated use at elevated tem-
5.1.1 The accuracy of the testing machine shall be within
peratures. Increased bending stresses may result. Therefore,
the permissible variation specified in Practices E 4.
grips and pull rods should be periodically retested for axiality
5.1.2 Precaution should be taken to assure that the load on
and reworked when necessary.
the specimens is applied as axially as possible. Perfect axial
5.1.3 The testing machine shall be equipped with a means of
alignment is difficult to obtain especially when the pull rods
measuring and controlling either the strain rate or the rate of
and extensometer rods pass through packing at the ends of the
crosshead motion or both to meet the requirements in 9.6.
furnace. However, the machine and grips should be capable of
5.1.4 For high-temperature testing of materials that are
loading a precisely made specimen so that the maximum
readily attacked by their environment (such as oxidation of
bending strain does not exceed 10 % of the axial strain, when
metal in air), the specimen may be enclosed in a capsule so that
the calculations are based on strain readings taken at zero load
it can be tested in a vacuum or inert gas atmosphere. When
and at the lowest load for which the machine is being qualified.
such equipment is used, the necessary corrections to obtain true
NOTE 1—This requirement is intended to limit the maximum contribu-
specimen loads must be made. For instance, compensation
tion of the testing apparatus to the bending which occurs during a test. It
must be made for differences in pressures inside and outside of
is recognized that even with qualified apparatus different tests may have
the capsule and for any load variation due to sealing ring
quite different percent bending strain due to chance orientation of a
friction, bellows or other features.
loosely fitted specimen, lack of symmetry of that particular specimen,
lateral force from furnace packing, and thermocouple wire, etc. The scant 5.2 Heating Apparatus:
evidence available at this time indicates that the effect of bending strain
5.2.1 The apparatus for and method of heating the speci-
on test results is not sufficient, except in special cases, to require the
mens should provide the temperature control necessary to
measurement of this quantity on each specimen tested.
satisfy the requirements specified in 9.4.
5.1.2.1 In testing of brittle material even a bending strain of
5.2.2 Heating shall be by an electric resistance or radiation
10 % may result in lower strength than would be obtained with
furnace with the specimen in air at atmospheric pressure unless
improved axiality. In these cases, measurements of bending
other media are specifically agreed upon in advance.
strain on the specimen to be tested may be specifically
NOTE 2—The media in which the specimens are tested may have a
requested and the permissible magnitude limited to a smaller
considerable effect on the results of tests. This is particularly true when the
value.
5.1.2.2 In general, equipment is not available for determin-
ing maximum bending strain at elevated temperatures. The
Jones, M. H. and Brown, Jr., W. F., “An Axial Loading Creep Machine,” ASTM
Bulletin, American Society for Testing and Materials, ASTBA, January 1956, pp.
53–60.
Schmieder, A. K., “Measuring the Apparatus Contributions to Bending in
Subcommittee E28.10 on Effect of Elevated Temperature on Properties requests Tension Specimens,” Elevated Temperature Testing Problem Areas, ASTM STP 488,
factual information on the effect of nonaxiality of loading on test results. American Society for Testing and Materials, 1971, pp. 15–42.
NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
E21
properties are influenced by oxidation or corrosion during the test,
at elevated temperature the stress and strain in the elastic range
although other effects can also influence test results.
of a metal of known modulus of elasticity. Care should be
taken to avoid combinations of stress and temperature which
5.3 Temperature-Measuring Apparatus:
will result in creep of the specimen during the extensometer
5.3.1 The method of temperature measurement must be
system evaluation.
sufficiently sensitive and reliable to ensure that the temperature
of the specimen is within the limits specified in 9.4.4.
NOTE 4—If an extensometer of Class B-2 or better is attached to the
5.3.2 Temperature should be measured with thermocouples
reduced section of the specimen, the slope of the stress-strain curve will
in conjunction with potentiometers or millivoltmeters. usually be within 10 % of the modulus of elasticity.
5.4.2 Nonaxiality of loading is usually sufficient to cause
NOTE 3—Such measurements are subject to two types of error. Ther-
mocouple calibration and instrument measuring errors initially introduce
significant errors at small strains when strain is measured on
uncertainty as to the exact temperature. Secondly both thermocouples and
only one side of the specimen. Therefore, the extensometer
measuring instruments may be subject to variation with time. Common
should be attached to and indicate strain on opposite sides of
errors encountered in the use of thermocouples to measure temperatures
the specimen. The reported strain should be the average of the
include: calibration error, drift in calibration due to contamination or
strains on the two sides, either a mechanical or electrical
deterioration with use, lead-wire error, error arising from method of
average internal to the instrument or a numerical average of
attachment to the specimen, direct radiation of heat to the bead, heat-
conduction along thermocouple wires, etc. two separate readings.
5.4.3 When feasible the extensometer should be attached
5.3.3 Temperature measurements should be made with ther-
directly to the reduced section of the specimen. When neces-
mocouples of known calibration. Representative thermo-
sary, other arrangements (discussed in 9.6.3) may be used by
couples should be calibrated from each lot of wires used for
prior agreement of the parties concerned. For example, special
making base-metal thermocouples. Except for relatively low
arrangements may be necessary in testing brittle materials
temperatures of exposure, base-metal thermocouples are sub-
where failure is apt to be initiated at an extensometer knife
ject to error upon reuse, unless the depth of immersion and
edge.
temperature gradients of the initial exposure are reproduced.
5.4.4 To attach the extensometer to miniature specimens
Consequently base-metal thermocouples should be calibrated
may be impractical. In this case, separation of the specimen
by the use of representative thermocouples and actual thermo-
holders or crossheads may be recorded and used to determine
couples used to measure specimen temperatures should not be
strains
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