ASTM A938-07
(Test Method)Standard Test Method for Torsion Testing of Wire
Standard Test Method for Torsion Testing of Wire
SIGNIFICANCE AND USE
The complex stress and strain conditions that occur in the sample during the torsion test are sensitive to minor variations in materials, making the torsion test a useful tool in assessing wire ductility under torsional loading.
SCOPE
1.1 This test method describes the torsion (or twist) testing of metallic wire.
1.2 The values stated in U.S. customary units are to be regarded as the standard. The SI equivalents of U.S. customary units may be approximate.
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.
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Designation: A938 − 07
StandardTest Method for
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Torsion Testing of Wire
This standard is issued under the fixed designation A938; 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 (´) indicates an editorial change since the last revision or reapproval.
1. Scope* clamping head shall be equipped with a device capable of
applying the necessary tensile load.
1.1 This test method describes the torsion (or twist) testing
5.1.3 The clamping heads shall clamp the wire firmly, but
of metallic wire.
should not damage it to the extent that fracture occurs at the
1.2 The values stated in U.S. customary units are to be
clamping point during twisting. The distance between the
regarded as the standard. The SI equivalents of U.S. customary
clamps is the test length. The wire shall be twisted only along
units may be approximate.
the test length, and not at the point of clamping. These
1.3 This standard does not purport to address all of the requirements can be satisfied by bending a short section at each
safety concerns, if any, associated with its use. It is the
end of the specimen to an angle of about 90° to the wire axis,
responsibility of the user of this standard to establish appro- as described in 6.3.
priate safety and health practices and determine the applica-
5.2 Revolution Counter—Amechanism to count the number
bility of regulatory limitations prior to use.
of twists shall be provided.
5.3 Protective Shield—Aprotective shield shall be provided
2. Referenced Documents
to protect the operator from flying fragments in cases when the
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2.1 ASTM Standards:
wire breaks into more than two pieces.
E6 Terminology Relating to Methods of Mechanical Testing
6. Specimen Preparation
3. Terminology
6.1 Straightening—The test piece, consisting of a length of
3.1 Definitions—The definitions related to torsion testing
wire, should be straight before being tested. If straightening is
appearing in Terminology E6 shall be considered as applying
necessary, it shall, unless otherwise specified, be done by hand.
to the terms used in this test method.
Other straightening techniques are permitted provided surface
4. Significance and Use
damage is avoided. Since the shear stress is maximum at the
surface of the wire during testing, even slight surface damage
4.1 The complex stress and strain conditions that occur in
such as pits or scratches can cause early fracture, and the
the sample during the torsion test are sensitive to minor
results may not be indicative of the full capability of the wire.
variations in materials, making the torsion test a useful tool in
assessing wire ductility under torsional loading.
NOTE 1—During straightening, it is important that the properties and
cross section remain unchanged as far as possible. In particular, the
5. Apparatus specimen shall not be subjected to any twisting.
6.2 Test Length:
5.1 Clamping Heads:
6.2.1 Recommended test length is 8 in. (203 mm) (distance
5.1.1 The torsion test apparatus must have clamping heads
between the clamping heads). Sufficient material must also be
that will remain coaxial (within 10°) during the test.
provided to allow for gripping.
5.1.2 One clamping head shall be easily displaceable in the
6.2.2 Other test lengths may be used as agreed upon
direction of the wire axis. This longitudinally displaceable
between the producer and purchaser or as specified in the
appropriate product specification.
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This test method is under the jurisdiction of ASTM Committee A01 on Steel,
6.2.3 When a test length other than 8 in. (203 mm) is used,
Stainless Steel and RelatedAlloysand is the direct responsibility of A01.03 on Steel
the minimum torsions shall be revised in direct proportion to
Rod and Wire.
the change in the jaw spacing, or as determined by the
Current edition approved Sept. 1, 2007. Published October 2007. Originally
approved in 1975. Last previous edition approved in 2004 as A938 – 04. DOI:
following formula:
10.1520/A0938-07.
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contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
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*A Summary of Changes section appears at the end of this standard
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A938 − 07
broken ends. If the number of turns does not satisfy the
T = minimum torsions for new length,
x
requirements of the specification, and the initial fracture,
T = minimum torsions for 8 in. (203 mm)
...
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