ASTM E1450-92(1998)

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 E111.  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 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. See Section 5.

General Information

• Status: Historical
• Publication Date: 09-Apr-1998
• Technical Committee: E28 - Mechanical Testing

Relations

• Replaced By: ASTM E1450-92(1998)e1 - Standard Test Method for Tension Testing of Structural Alloys in Liquid Helium
• Effective Date: 15-Jan-1992

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NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.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: 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 E1450; 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 (ε) indicates an editorial change since the last revision or reapproval.
1. Scope E8 TestMethodsforTensionTestingofMetallicMaterials
E8M Test Methods for Tension Testing of Metallic Mate-
1.1 This test method describes procedures for the tension
rials [Metric]
testing of structural alloys in liquid helium. The format is
E29 Practice for Using Significant Digits in Test Data to
similar to that of other ASTM tension test standards, but the
Determine Conformance with Specifications
contents include modifications for cryogenic testing which
E83 Practice for Verification and Classification of Exten-
requires special apparatus, smaller specimens, and concern for
someters
serrated yielding, adiabatic heating, and strain-rate effects.
E111 TestMethodforYoung’sModulus,TangentModulus,
1.2 To conduct a tension test by this standard, the specimen
and Chord Modulus
in a cryostat is fully submerged in normal liquid helium (He I)
E 1012 Practice for Verification of Specimen Alignment
and tested using crosshead displacement control at a nominal
−3 −1
Under Tensile Loading
strain rate of 10 s or less. Tests using load control or high
strain rates are not considered.
3. Terminology
1.3 This standard specifies methods for the measurement of
3.1 Definitions:
yield strength, tensile strength, elongation, and reduction of
3.1.1 Thedefinitionsoftermsrelatingtotensiontestingthat
area.ThedeterminationoftheelasticmodulusistreatedinTest
appear in Terminology E6 shall apply here. The definitions in
Method E111.
this section also apply.
NOTE 1—The boiling point of normal liquid helium (He I) at sea level
3.1.2 adiabatic heating—the internal heating of a specimen
is 4.2 K (−452.1°F or 7.6°R). It decreases with geographic elevation and
resulting from tension testing under conditions such that the
is 4.0 K (−452.5°F or 7.2°R) at the National Institute of Standards and
heat generated by plastic work cannot be quickly dissipated to
Technology in Colorado, 1677 m (5500 ft) above sea level. In this
the surrounding cryogen.
standard the temperature is designated 4 K.
3.1.3 adjusted length of the reduced section—the length of
1.4 Values stated in SI units are treated as primary. Values
the reduced section plus an amount calculated to compensate
stated in U.S. customary units are treated as secondary.
for strain in the fillet region.
1.5 This standard does not purport to address all of the
3.1.4 axial strain—the average of the longitudinal strains
safety concerns, if any, associated with its use. It is the
measuredatoppositeorequallyspacedsurfacelocationsonthe
responsibility of the user of this standard to establish appro-
sidesofthelongitudinalaxisofsymmetryofthespecimen.The
priate safety and health practices and determine the applica-
longitudinal strains are measured using two or more strain-
bility of regulatory limitations prior to use. See Section 5.
sensing devices located at the mid-length of the reduced
section.
2. Referenced Documents
3.1.5 bending strain—the difference between the strain at
2.1 ASTM Standards:
the surface of the specimen and the axial strain (the bending
A370 TestMethodsandDefinitionsforMechanicalTesting
strain varies around the circumference and along the reduced
of Steel Products
section of the specimen).
E4 Practices for Force Verification of Testing Machines
3.1.6 Dewar—a vacuum-insulated container for cryogenic
E6 Terminology Relating to Methods of Mechanical Test-
fluids.
ing
3.1.7 discontinuous yielding stress, σ—the peak stress at
i
the initiation of the first measurable serration on the curve of
1 stress-versus-strain.
This test method is under the jurisdiction of ASTM Committee E-28 on
3.1.7.1 Discussion—The parameter σ is a function of test
Mechanical Testing and is the direct responsibility of Subcommittee E28.10 on
i
Effect of Temperature on the Properties of Metals.
variables and is not a material constant.
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.
E 1450
3.1.8 gage length—the original distance between gage strain with internal specimen heating. Examples of serrated
marks made on the specimen for determining elongation after stress-strain curves for a typical austenitic stainless steel with
fracture. discontinuous yielding are shown in Fig. 2.
3.1.9 length of the reduced section—the distance between 4.3 A constant specimen temperature cannot be maintained
the tangent points of the fillets that bound the reduced section.
at all times during tests in liquid helium. The specimen
3.1.10 maximum bending strain—the largest value of bend- temperature at local regions in the reduced section rises
ing strain in the reduced section of the specimen.
temporarily above 4 K during each discontinuous yielding
3.1.10.1 Discussion—Maximum bending strength is calcu- event (see Fig. 2), owing to adiabatic heat. The number of
lated from strains measured at two, three, or more circumfer-
events and the magnitude of the associated load drops are a
ential positions, and at each of two different longitudinal function of the material composition and other factors such as
positions.
specimen size and test speed. Typically, altering the mechani-
3.1.11 reduced section—sectioninthecentralportionofthe cal test variables can modify but not eliminate the discontinu-
specimen, which has a cross section smaller than the gripped
ousyielding(2-4).Therefore,tensilepropertymeasurementsof
ends. alloys in liquid helium (especially tensile strength, elongation,
3.1.12 tensile cryostat—atestapparatusforapplyingtensile and reduction of area) lack the usual significance of property
forces to test specimens in cryogenic environments (Fig. 1).
measurements at room temperature where deformation is more
nearlyisothermalanddiscontinuousyieldingtypicallydoesnot
4. Significance and Use
occur.
4.1 Tension tests provide information on the strength and
4.4 The stress-strain response of a material tested in liquid
ductibility of materials under uniaxial tensile stresses. This helium depends on whether load control or displacement
information may be useful for alloy development, comparison
controlisused (3).Crossheaddisplacementcontrolisspecified
and selection of materials, and quality control. Under certain in this standard since the goal is material characterization by
circumstances, the information may also be useful for design.
conventional methods. The possibility of a different and less
4.2 The force-time and force-extension records for alloys favorable material response must be taken into account when
tested in liquid helium using displacement control are serrated
data are used for design in actual applications subject to
(1). Serrations are formed by repeated bursts of unstable load-controlled conditions.
plastic flow and arrests. The unstable plastic flow (discontinu-
ous yielding) is a free-running process occurring in localized
5. Hazards
regions of the reduced section at higher than nominal rates of
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
Theboldfacenumbersinparenthesesrefertothelistofreferencesattheendof
protection may require goggles, clothing without pockets or
this test method.
cuffs, gloves, and tongs for handling cold specimens. Cryo-
geniccontainersthatareinternallypressurizedorevacuatedare
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 E4 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
specimen, by replacing the specimen with a rigid block, or by
using a special calibration specimen. Then, measure the com-
pliance at a low force and at the highest force used to qualify
the machine, as directed in 6.4.1 of this test method.
6.2 System Design—Typically, alloys in liquid helium ex-
hibit double or triple their ambient strengths. For the same
specimen geometry, higher forces must be applied to the
cryostat, test specimen, load train members, and grips at
cryogenic temperatures. Since many conventional test ma-
FIG. 1 Schematic Illustration of Typical Cryostat for Tension
Testingat4K chines have a maximum force of 100 kN (22 480 lbf) or less,
E 1450
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)
it is recommended that the apparatus be designed to accom- specimen so that the maximum bending strain does not exceed
modate one of the small specimens cited in 8.2.2 of this test 10%oftheaxialstrain.Reducebendingstraintoanacceptable
method. level by making proportional adjustments to a cryostat having
6.3 Construction Materials—Many construction materials, alignment capability, or by using spacing shims to compensate
including the vast majority of ferritic steels, are brittle at 4 K.
an unadjustable fixture. Calculate the strain based on readings
To prevent service failures, fabricate the grips and other taken while the calibration specimen is subjected to a low
load-train members using strong, tough, cryogenic alloys.
force,aswellasatthehighestforceforwhichthemachineand
Materials that have low thermal conductivity are desirable to
load train are being qualified. Procedures for measuring speci-
reduce heat flow. Austenitic stainless steels (AISI 304LN),
men alignment are given in Practice E1012.
maragingsteels(200,250,or300grades,withnickelplatingto
NOTE 2—This requirement will minimize contributions from the test
prevent rust), and extra-low-interstitial (ELI) grade titanium
apparatustothebendingstrain.Testsperformedwithaqualifiedapparatus
alloys (Ti-6Al-4V and Ti-5Al-2.5Sn) have been used with
maystillvaryinamountofbendingstrainowingtosmallvariationsinthe
proper design, for grips, pull rods, and cryostat frames.
proposed test specimen configurations, or differences in machining.
Nonmetallic materials (for example, glass-epoxy composites)
6.4.3 Multiple-Specimen Apparatus—For this type of cry-
are excellent insulators and are sometimes used for compres-
ostat the alignment depends on the type of fixtures used.
sion members.
Measure and record the maximum bending strain.
6.4 Alignment:
6.4.1 Proper system alignment is essential to avoid bending 6.4.4 Qualify the apparatus by making axiality measure-
strains in the tension tests. mentsatroomtemperatureandat4K.Toperformaxialitytests
6.4.2 Single-Specimen Apparatus—For a conventional of the apparatus, the specimen form should be the same as that
single-specimen cryostat, the machine and grips should be used during cryogenic tests, and the specimen concentricity
capable of applying force to a precisely machined calibration shouldbeasnearlyperfectaspossible.Noplasticstrainshould
E 1450
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
required. After testing, the helium may be released to the
6.4.4.1 For cylindrical specimens, calculate the maximum
atmosphere (see Section 5), recycled as a gas, or reliquefied.
bending strain defined in 3.1.10 from the strains measured at
Recycling or reliquefaction requires large investments in puri-
three circumferential positions, at each of two different longi-
fication and support systems.
tudinal positions. Measure the strains with three electrical-
6.8 Temperature Maintenance and Liquid-Level
resistance strain gages, extensometers, or clip gages equally
Indicators—The intended test condition is ensured by main-
spaced around the reduced section of the specimen. The two
taining a liquid helium environment. With the specimen
longitudinalpositionsshouldbeasfarapartaspossible,butnot
completely immersed, a thermocouple to measure its tempera-
closer than one diameter to a fillet.
tureisnotrequiredforroutinetests.Instead,asimpleindicator
6.4.4.2 For specimens of square or rectangular cross sec-
or meter is required to ensure that the specimen remains fully
tion, measure the strain at the center of two parallel (opposite)
submerged throughout the test. An on-off indicator of the
faces, or in the case of thin cross sections, at the center of the
carbon-resistor type located at some reference point in the
two broad faces.
cryostat may be used to verify that the liquid level always
6.4.4.3 For conventional threaded or pinned grips, evaluate
remainsabovethespecimen.Alternatively,theliquidlevelmay
the effect of specimen bias as follows. Repeat the axiality
be continuously monitored using a superconducting wire
measurements with the specimen rotated 180°, but with the
sensor of appropriate length positioned vertically inside the
grips and pull rods retained in their original positions. Then
cryostat.
calculate the maximum bending strain and the strain at the
NOTE 3—One indication of the system nearing and reaching a steady
specimen axis as the average of the two readings at the same
state condition is the amount of condensation flare. As liquid helium is
position relative to the machine. If other grips or methods are
transferred into the cryostat, the flare becomes visible when boiled-off
used to evaluate the effect of specimen bias it should be
helium contacts room temperature air at the vent of the cryostat (Fig. 1).
described
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