ASTM E1450-92(1998)e1
(Test Method)Standard Test Method for Tension Testing of Structural Alloys in Liquid Helium
Standard Test Method for Tension Testing of Structural Alloys in Liquid Helium
SCOPE
1.1 This test method describes procedures for the tension testing of structural alloys in liquid helium. The format is similar to that of other ASTM tension test standards, but the contents include modifications for cryogenic testing which requires special apparatus, smaller specimens, and concern for serrated yielding, adiabatic heating, and strain-rate effects.
1.2 To conduct a tension test by this standard, the specimen in a cryostat is fully submerged in normal liquid helium (He I) and tested using crosshead displacement control at a nominal strain rate of 10-3 s-1 or less. Tests using load control or high strain rates are not considered.
1.3 This standard specifies methods for the measurement of yield strength, tensile strength, elongation, and reduction of area. The determination of the elastic modulus is treated in Test Method E 111.
Note 1—The boiling point of normal liquid helium (He I) at sea level is 4.2 K (-452.1°F or 7.6°R). It decreases with geographic elevation and is 4.0 K (-452.5°F or 7.2°R) at the National Institute of Standards and Technology in Colorado, 1677 m (5500 ft) above sea level. In this standard the temperature is designated 4 K.
1.4 Values stated in SI units are treated as primary. Values stated in U.S. customary units are treated as secondary.
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 and health practices and determine the applicability of regulatory limitations prior to use. See Section 5.
General Information
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Standards Content (Sample)
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Designation: E 1450 – 92 (Reapproved 1998)
Standard Test Method for
Tension Testing of Structural Alloys in Liquid Helium
This standard is issued under the fixed designation E 1450; 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.
e NOTE—Section 4.1 was editorially updated in June 2003.
1. Scope E 6 Terminology Relating to Methods of Mechanical Test-
ing
1.1 This test method describes procedures for the tension
E 8 Test Methods for Tension Testing of Metallic Materials
testing of structural alloys in liquid helium. The format is
E 8M Test Methods for Tension Testing of Metallic Mate-
similar to that of other ASTM tension test standards, but the
rials [Metric]
contents include modifications for cryogenic testing which
E 29 Practice for Using Significant Digits in Test Data to
requires special apparatus, smaller specimens, and concern for
Determine Conformance with Specifications
serrated yielding, adiabatic heating, and strain-rate effects.
E 83 Practice for Verification and Classification of Exten-
1.2 To conduct a tension test by this standard, the specimen
someters
in a cryostat is fully submerged in normal liquid helium (He I)
E 111 Test Method for Young’s Modulus, Tangent Modulus,
and tested using crosshead displacement control at a nominal
−3 −1
and Chord Modulus
strain rate of 10 s or less. Tests using load control or high
E 1012 Practice for Verification of Specimen Alignment
strain rates are not considered.
Under Tensile Loading
1.3 This standard specifies methods for the measurement of
yield strength, tensile strength, elongation, and reduction of
3. Terminology
area. The determination of the elastic modulus is treated in Test
3.1 Definitions:
Method E 111.
3.1.1 The definitions of terms relating to tension testing that
NOTE 1—The boiling point of normal liquid helium (He I) at sea level
appear in Terminology E 6 shall apply here. The definitions in
is 4.2 K (−452.1°F or 7.6°R). It decreases with geographic elevation and
this section also apply.
is 4.0 K (−452.5°F or 7.2°R) at the National Institute of Standards and
3.1.2 adiabatic heating—the internal heating of a specimen
Technology in Colorado, 1677 m (5500 ft) above sea level. In this
resulting from tension testing under conditions such that the
standard the temperature is designated 4 K.
heat generated by plastic work cannot be quickly dissipated to
1.4 Values stated in SI units are treated as primary. Values
the surrounding cryogen.
stated in U.S. customary units are treated as secondary.
3.1.3 adjusted length of the reduced section—the length of
1.5 This standard does not purport to address all of the
the reduced section plus an amount calculated to compensate
safety concerns, if any, associated with its use. It is the
for strain in the fillet region.
responsibility of the user of this standard to establish appro-
3.1.4 axial strain—the average of the longitudinal strains
priate safety and health practices and determine the applica-
measured at opposite or equally spaced surface locations on the
bility of regulatory limitations prior to use. See Section 5.
sides of the longitudinal axis of symmetry of the specimen. The
longitudinal strains are measured using two or more strain-
2. Referenced Documents
sensing devices located at the mid-length of the reduced
2.1 ASTM Standards:
section.
A 370 Test Methods and Definitions for Mechanical Testing
3.1.5 bending strain—the difference between the strain at
of Steel Products
the surface of the specimen and the axial strain (the bending
E 4 Practices for Force Verification of Testing Machines
strain varies around the circumference and along the reduced
section of the specimen).
3.1.6 Dewar—a vacuum-insulated container for cryogenic
This test method is under the jurisdiction of ASTM Committee E-28 on
Mechanical Testing and is the direct responsibility of Subcommittee E28.10 on
fluids.
Effect of Temperature on the Properties of Metals.
Current edition approved Jan. 15, 1992. Published April 1992.
Annual Book of ASTM Standards, Vol 01.03.
3 4
Annual Book of ASTM Standards, Vol 03.01. Annual Book of ASTM Standards, Vol 14.02.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
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e1
E 1450 – 92 (1998)
3.1.7 discontinuous yielding stress, s —the peak stress at (1). Serrations are formed by repeated bursts of unstable
i
the initiation of the first measurable serration on the curve of plastic flow and arrests. The unstable plastic flow (discontinu-
stress-versus-strain. ous yielding) is a free-running process occurring in localized
3.1.7.1 Discussion—The parameter s is a function of test regions of the reduced section at higher than nominal rates of
i
variables and is not a material constant. strain with internal specimen heating. Examples of serrated
3.1.8 gage length—the original distance between gage stress-strain curves for a typical austenitic stainless steel with
marks made on the specimen for determining elongation after discontinuous yielding are shown in Fig. 2.
fracture. 4.3 A constant specimen temperature cannot be maintained
3.1.9 length of the reduced section—the distance between at all times during tests in liquid helium. The specimen
the tangent points of the fillets that bound the reduced section. temperature at local regions in the reduced section rises
3.1.10 maximum bending strain—the largest value of bend- temporarily above 4 K during each discontinuous yielding
ing strain in the reduced section of the specimen. event (see Fig. 2), owing to adiabatic heat. The number of
3.1.10.1 Discussion—Maximum bending strength is calcu- events and the magnitude of the associated load drops are a
lated from strains measured at two, three, or more circumfer- function of the material composition and other factors such as
ential positions, and at each of two different longitudinal specimen size and test speed. Typically, altering the mechani-
positions. cal test variables can modify but not eliminate the discontinu-
3.1.11 reduced section—section in the central portion of the ous yielding (2-4). Therefore, tensile property measurements of
specimen, which has a cross section smaller than the gripped alloys in liquid helium (especially tensile strength, elongation,
ends. and reduction of area) lack the usual significance of property
3.1.12 tensile cryostat—a test apparatus for applying tensile measurements at room temperature where deformation is more
forces to test specimens in cryogenic environments (Fig. 1). nearly isothermal and discontinuous yielding typically does not
occur.
4. Significance and Use
4.4 The stress-strain response of a material tested in liquid
4.1 Tension tests provide information on the strength and
helium depends on whether load control or displacement
ductility of materials under uniaxial tensile stresses. This control is used (3). Crosshead displacement control is specified
information may be useful for alloy development, comparison
in this standard since the goal is material characterization by
and selection of materials, and quality control. Under certain conventional methods. The possibility of a different and less
circumstances, the information may also be useful for design.
favorable material response must be taken into account when
4.2 The force-time and force-extension records for alloys data are used for design in actual applications subject to
tested in liquid helium using displacement control are serrated
load-controlled conditions.
5. Hazards
5.1 Several precautions must be observed in the use of
cryogenic fluids and equipment. Skin or eye contact with
cryogens will freeze and destroy tissue. The appropriate
protection may require goggles, clothing without pockets or
cuffs, gloves, and tongs for handling cold specimens. Cryo-
genic containers that are internally pressurized or evacuated are
potentially hazardous in that damage or leaks can produce
explosions or implosions. Also, when liquids evaporate to
gases, there is a huge volume increase; therefore asphyxiation
is a potential threat where liquid nitrogen or liquid helium
evaporates in rooms that are not properly ventilated. Safety
guidelines pertaining to the use of liquid helium and other
cryogenic fluids are considered elsewhere in more detail (5).
6. Apparatus
6.1 Test Machines—Use a test machine that meets the
requirements of Practices E 4 regarding verification of force
accuracy. Know the test machine compliance (displacement
per unit of applied force of the apparatus itself). Measure the
compliance by coupling the load train without including a
FIG. 1 Schematic Illustration of Typical Cryostat for Tension
The boldface numbers in parentheses refer to the list of references at the end of
Testing at 4 K this test method.
NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
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E 1450 – 92 (1998)
FIG. 2 Typical Engineering Stress-Strain Curves and Specimen Temperature Histories, at Four Different Nominal Strain Rates,
for AISI 304L Stainless Steel Tested in Liquid Helium (4)
specimen, by replacing the specimen with a rigid block, or by Nonmetallic materials (for example, glass-epoxy composites)
using a special calibration specimen. Then, measure the com- are excellent insulators and are sometimes used for compres-
pliance at a low force and at the highest force used to qualify
sion members.
the machine, as directed in 6.4.1 of this test method.
6.4 Alignment:
6.2 System Design—Typically, alloys in liquid helium ex-
6.4.1 Proper system alignment is essential to avoid bending
hibit double or triple their ambient strengths. For the same
strains in the tension tests.
specimen geometry, higher forces must be applied to the
6.4.2 Single-Specimen Apparatus—For a conventional
cryostat, test specimen, load train members, and grips at
single-specimen cryostat, the machine and grips should be
cryogenic temperatures. Since many conventional test ma-
capable of applying force to a precisely machined calibration
chines have a maximum force of 100 kN (22 480 lbf) or less,
specimen so that the maximum bending strain does not exceed
it is recommended that the apparatus be designed to accom-
10 % of the axial strain. Reduce bending strain to an acceptable
modate one of the small specimens cited in 8.2.2 of this test
level by making proportional adjustments to a cryostat having
method.
alignment capability, or by using spacing shims to compensate
6.3 Construction Materials—Many construction materials,
an unadjustable fixture. Calculate the strain based on readings
including the vast majority of ferritic steels, are brittle at 4 K.
taken while the calibration specimen is subjected to a low
To prevent service failures, fabricate the grips and other
force, as well as at the highest force for which the machine and
load-train members using strong, tough, cryogenic alloys.
load train are being qualified. Procedures for measuring speci-
Materials that have low thermal conductivity are desirable to
men alignment are given in Practice E 1012.
reduce heat flow. Austenitic stainless steels (AISI 304LN),
maraging steels (200, 250, or 300 grades, with nickel plating to
NOTE 2—This requirement will minimize contributions from the test
prevent rust), and extra-low-interstitial (ELI) grade titanium
apparatus to the bending strain. Tests performed with a qualified apparatus
alloys (Ti-6Al-4V and Ti-5Al-2.5Sn) have been used with
may still vary in amount of bending strain owing to small variations in the
proper design, for grips, pull rods, and cryostat frames. proposed test specimen configurations, or differences in machining.
NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
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E 1450 – 92 (1998)
6.4.3 Multiple-Specimen Apparatus—For this type of cry- tical designs, including turret-disc designs for multiple-
specimen testing with a single cooling, are discussed in Refs
ostat the alignment depends on the type of fixtures used.
(6-10).
Measure and record the maximum bending strain.
6.7.2 Dewars—Stainless steel Dewars are safer (that is,
6.4.4 Qualify the apparatus by making axiality measure-
more fracture resistant) than glass Dewars and less expensive
ments at room temperature and at 4 K. To perform axiality tests
than fiberglass Dewars. Generally, a single helium Dewar (see
of the apparatus, the specimen form should be the same as that
Fig. 1) is sufficient for short-term tensile tests. Also possible is
used during cryogenic tests, and the specimen concentricity
a double-Dewar arrangement in which an outer Dewar of liquid
should be as nearly perfect as possible. No plastic strain should
nitrogen surrounds the inner Dewar of liquid helium.
occur in the reduced section of the alignment specimen during
6.7.3 Ancillary Equipment—Dewars and transfer lines for
loading. In some cases this may necessitate the use of a
liquid helium must be vacuum insulated. Vacuum pumps,
relatively stiff, high-strength calibration specimen.
pressurized gas, and liquid nitrogen facilities are therefore
6.4.4.1 For cylindrical specimens, calculate the maximum
required. After testing, the helium may be released to the
bending strain defined in 3.1.10 from the strains measured at
atmosphere (see Section 5), recycled as a gas, or reliquefied.
three circumferential positions, at each of two different longi-
Recycling or reliquefaction requires large investments in puri-
tudinal positions. Measure the strains with three electrical-
fication and support systems.
resistance strain gages, extensometers, or clip gages equally
6.8 Temperature Maintenance and Liquid-Level
spaced around the reduced section of the specimen. The two
Indicators—The intended test condition is ensured by main-
longitudinal positions should be as far apart as possible, but not
taining a liquid helium environment. With the specimen
closer than one diameter to a fillet.
completely immersed, a thermocouple to measure its tempera-
6.4.4.2 For specimens of square or rectangular cross sec-
ture is not required for routine tests. Instead, a simple indicator
tion, measure the s
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