ASTM D4975-96a
(Test Method)Standard Test Methods for Single-Filament Tire Bead Wire Made from Steel
Standard Test Methods for Single-Filament Tire Bead Wire Made from Steel
SCOPE
1.1 These test methods cover testing of single-filament steel wires that are components of tire beads used in the manufacture of pneumatic tires. By agreement, these test methods may be applied to similar filaments used for reinforcing other rubber products.
1.2 These test methods describe test procedures only and do not establish specifications and tolerances.
1.3 These test methods are written in SI units. The inch-pound units which are provided are not necessarily exact equivalents of the SI units. Either system of units may be used in these test methods. In case of referee decisions the SI units will prevail.
1.4 These test methods cover the determination of the mechanical properties listed below:
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.
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Designation: D 4975 – 96a
Standard Test Methods for
Single-Filament Tire Bead Wire Made from Steel
This standard is issued under the fixed designation D 4975; 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.
1. Scope 3. Terminology
1.1 These test methods cover testing of single-filament steel 3.1 Definitions:
wires that are components of tire beads used in the manufacture 3.1.1 breaking force, n—the maximum force applied to a
of pneumatic tires. By agreement, these test methods may be material carried to rupture.
applied to similar filaments used for reinforcing other rubber 3.1.2 percent elongation, n—the increase in length of a
products. specimen expressed as a percentage of the original length.
1.2 These test methods describe test procedures only and do 3.1.3 tire bead, n—that part of a tire that comes in contact
not establish specifications and tolerances. with the rim and that is shaped to secure the tire to the rim.
1.3 These test methods are written in SI units. The inch- 3.1.4 tire bead wire, n—a monofilament steel wire with a
pound units which are provided are not necessarily exact metallic coating, usually bronze, used in forming a tire bead.
equivalents of the SI units. Either system of units may be used 3.1.5 torsion resistance, n—in tire bead wire, the number of
in these test methods. In case of referee decisions the SI units turns of twist in a short length of wire that causes rupture.
will prevail. 3.1.6 yield strength, n—the stress at which a material
1.4 These test methods cover the determination of the exhibits a specified limiting deviation from the proportionality
mechanical properties listed below: of stress to strain.
1.5 This standard does not purport to address all of the 3.1.6.1 Discussion—It is customary in this instance to
safety problems, if any, associated with its use. It is the express the deviation in terms of strain and to determine yield
responsibility of the user of this standard to establish appro- strength by the offset method where a strain of 0.2 % is
priate safety and health practices and determine the applica- specified (see 10.9.1).
bility of regulatory limitations prior to use. 3.1.7 For definitions of other textile terms, refer to Termi-
nology D 123.
Property Section
Breaking Force (Strength) 7-13
4. Summary of Test Methods
Yield Strength 7-13
4.1 A summary of the directions prescribed for the determi-
Elongation 7-13
Torsion Resistance 14-20
nation of specific properties of tire bead wire is stated in the
Diameter (Gage) 21-27
appropriate sections of the specific test methods that follow.
2. Referenced Documents
5. Significance and Use
2.1 ASTM Standards:
5.1 The procedures for the determination of properties of
A 370 Test Methods and Definitions for Mechanical Testing
single-filament bead wire made from steel are considered
of Steel Products
satisfactory for acceptance testing of commercial shipments of
D 76 Specification for Tensile Testing Machines for Tex-
this product since the procedures are the best available and
tiles
have been used extensively in the trade.
D 123 Terminology Relating to Textiles
5.1.1 In case of a dispute arising from differences in
D 2969 Test Method for Steel Tire Cords
reported test results when using these test methods for accep-
E 6 Terminology Relating to Methods of Mechanical Test-
tance testing of commercial shipments, the purchaser and
ing
supplier should conduct comparative tests to determine if there
E 558 Test Method for Torsion Testing of Wire
is a statistical bias between their laboratories. Competent
statistical assistance is recommended for the investigation of
bias. As a minimum, the two parties should take a group of test
These test methods are under the jurisdiction of ASTM Committee D-13 on
Textiles and are the direct responsibility of Subcommittee D13.19 on Tire Cord and
specimens which are as homogeneous as possible and which
Fabrics.
are from a lot of material of the type in question. The test
Current edition approved Aug. and Oct. 10, 1996. Published December 1997.
specimens then should be randomly assigned in equal numbers
Originally published as D 4975 – 89. Last previous edition D 4975 – 93.
Annual Book of ASTM Standards, Vol 01.03. to each laboratory for testing. The average results from the two
Annual Book of ASTM Standards, Vol 07.01.
laboratories should be compared using Student’s t-test for
Annual Book of ASTM Standards, Vol 03.01.
Copyright © ASTM, 100 Barr Harbor Drive, West Conshohocken, PA 19428-2959, United States.
D 4975
unpaired data and an acceptable probability level chosen by the computing equipment which may be programmed to calculate
two parties before testing is begun. If a bias is found, either its and print the results for each of these desired properties.
cause must be determined and corrected or the purchaser and Because of the variety of electronic equipment available and
the supplier must agree to interpret future test results in the the various possibilities for recording test data, use of this type
light of the known bias. of equipment is not covered in this test method.
9.3 Grips, of such design that failure of the specimen does
6. Sampling
not occur at the gripping point, and slippage of the specimen
6.1 Lot Sample—As a lot sample for acceptance testing,
within the jaws (grips) is prevented.
take at random the number of reels, coils, spools, or other
10. Procedure
shipping units of wire directed in an applicable material
specification or other agreement between the purchaser and the
10.1 Thermally age the specimen by placing it in a suitable
supplier. Consider reels, coils, spools, or other shipping units of
oven for1hat 150°C (300°F). Allow specimens to cool to
wire to be the primary sampling units.
room temperature before testing.
10.2 Select the proper force scale range on the tensile
NOTE 1—A realistic specification or other agreement between the
purchaser and the supplier requires taking into account the variability testing machine based on the estimated breaking force of the
between and within primary sampling units so as to provide a sampling
specimen being tested.
plan which at the specified level of the property of interest has a
10.3 Adjust the distance between the grips of the testing
meaningful producer’s risk, acceptable quality level, and desired limiting
machine, nip to nip, to a gage length of 250 mm (10 in.).
quality level.
10.4 Secure the specimen in the upper grip sufficiently to
6.2 Laboratory Sample—Use the primary sampling units in
prevent slippage during testing. While keeping the specimen
the lot sample as a laboratory sample.
straight and taut, place and secure the other end in the lower
6.3 Test Specimens—For each test procedure, take the
grip.
number of lengths of tire bead wire of the specified lengths
10.5 Apply a force of 1 N (0.2 lbf) on the clamped specimen
from each laboratory sample as directed in the test procedure.
to take out any residual slack before initiating the test. This will
be considered the zero reference point for elongation calcula-
BREAKING FORCE, YIELD STRENGTH, AND
tions.
ELONGATION
10.6 After setting the cross head speed at 25 mm (1 in.)/min
7. Summary of Test Method
and recorder chart speed at 250 mm (10 in.)/min, start the
testing machine and record the force-extension curve gener-
7.1 The two ends of a specimen are clamped in a tensile
ated.
testing machine; an increasing force is applied until the
10.6.1 If the specimen fractures at or within 5 mm (0.2 in.)
specimen breaks. The change in force is measured versus the
of the gripping point, discard the result and test another
increase in separation of the specimen clamps to form a
specimen. If such jaw breaks continue to occur, insert a jaw
force-extension curve. Breaking force is read directly from the
liner such as an abrasive cloth between the gripping surface
curve and is expressed in newtons (pounds-force). Percent
and the specimen in a manner so that the liner extends beyond
elongation at break is the extension at break divided by the
the grip edge where it comes in contact with the specimen.
original specimen length, 3 100. The yield strength, the inter-
10.7 Conduct this test procedure on two specimens from
section of the force-extension curve with a line at 0.2 % offset,
each laboratory sampling unit.
is read from the force-extension curve and is expressed in
10.8 Elongation, the increase in gage length of a tensile
newtons (pounds-force).
specimen, is usually expressed as a percentage of the original
8. Significance and Use
gage length and can be determined from the force-extension
8.1 The load-bearing ability of a reinforced rubber product
curve.
such as a tire bead is related to the strength of the single- 10.8.1 When a greater degree of accuracy is required in the
filament wire used as the reinforcing material. The breaking determination of elongation, an extensometer can be attached
force and yield strength of tire bead wire is used in engineering to the specimen.
calculations when designing this type of reinforced product. 10.9 Yield strength is the stress at which a material exhibits
8.2 Elongation of tire bead wire is taken into consideration a specified limiting deviation from the proportionality of stress
in the design and engineering of tire beads because of its effect to strain. Determine the yield strength by the 0.2 % offset
on uniformity and dimensional stability during service. method.
10.9.1 On the force-extension curve (Fig. 1) that has been
9. Apparatus
generated (see 10.6) lay off Om equal to the specified value of
9.1 Tensile Testing Machine, CRE (Constant-Rate-of-
the offset (0.2 % elongation); draw mn parallel to OA and
Extension) tensile testing machine of such capacity that the
locate r. This intersection of mn with the force-extension curve
maximum force required to fracture the wire shall not exceed
corresponds to force R which is the yield strength. Should the
90 % nor be of less than 10 % of the selected force measure-
force-extension curve exhibit an initial nonlinear portion,
ment range. The specifications and methods of calibration and
verification shall conform to Specification D 76.
9.2 In some laboratories, the output of CRE type of tensile
Suitable electric ovens are manufactured by Blue M Electric Company, Blue
testing machine is connected with electronic recording and Island, IL 60406.
D 4975
Breaking force 15 N
Yield strength
0.965-mm diameter wire 15 N
1.295-mm diameter wire 40 N
Elongation 0.4 %
Materials were grouped by size for yield strength determi-
nations due to the differences calculated.
13.1.1 The magnitude of the differences is likely to be
affected adversely by different circumstances. The true values
of breaking force, elongation, and yield strength can be defined
only in terms of specific test methods. Within this limitation,
the procedures in this test method for determining these
properties have no known bias. Paragraphs 13.2-13.4 explain
the basis for this summary and for evaluations made under
other conditions.
13.2 Interlaboratory Test Data—An interlaboratory test was
run in 1990 in which randomly drawn samples of four
materials were tested in 13 laboratories. Each laboratory used
two operators, each of whom tested two specimens of each
FIG. 1 Force-Extension Curve for Determination of Yield
material on two separate days.
Strength by the Offset Method
NOTE 2—The bead wire products used in the interlaboratory evaluation
were of the following diameter and strength levels:
Material Diameter Strength
extrapolate from the straight line portion to the base line. This
intersection is point O used in this section.
1 0.965 mm regular
2 0.965 mm high
3 1.295 mm regular
11. Calculation
4 1.295 mm high
11.1 Calculate the average breaking force of the laboratory
13.3 Precision—For the property of interest, two averages
sample to the nearest5N(1 lbf).
of observed values should be considered significantly different
11.2 Calculate the elongation to rupture from the force-
at the 95 % probability level if the difference equals or exceeds
extension curve to the nearest 0.1 %. Should the force- the critical differences given in Table 1.
extension curve exhibit an initial nonlinear portion, extrapolate
NOTE 3—The tabulated values of the critical differences should be
from the straight line portion of the curve to the base line. This
considered to be a general statement, particularly with respect to between
intersection is the point of origin for the elongation determi-
laboratory precision. Before a meaningful statement can be made con-
nation. The extension from this point to the force at the point
cerning any two specific laboratories, the amount of statistical bias, if any,
of rupture is the total elongation. between them must be established, with each comparison being based on
recent data obtained on specimens taken from a lot of material of the type
11.3 Calculate the average yield strength of each laboratory
being evaluated so as to be as nearly homogeneous as possible and then
sample as directed in 10.9.1 to the nearest5N(1 lbf).
assigned randomly in equal numbers to each of the laboratories.
13.4 Bias—The procedures in this test method for measur-
12. Report
ing breaking force, elongation, and yield strength have no
12.1 State that the tests were performed as directed in Test
known bias because the value of these properties can be
Methods D 4975, describe the material or product tested, and
defined only in terms of a test method.
report the following:
TORSION RESISTANCE
12.1.1 The test results of each specimen and the laboratory
sample average. Calculate and report any other data agreed to
14. Summary of Test Method
between the purchaser and the supplier,
14.1 A single-filament of wire is tested in torsion by either
12.1.2 Date of test,
holding one end of the wire fixed while rotating the other or by
12.1.3 Type of tensile test machine and rate of extension,
rotating both ends in opposite directions at the same time until
and
fracture occurs.
12.1.4 Any deviation from the standard test procedure.
15. Significance and Use
15.1 Complex stress and strain conditions, sensitive to
13. Precision and Bias
variations in materials, occur in a wire specimen during torsion
13.1 Summary—In comparing two averages of two obser-
testing. The torsion test is a useful tool in assessing wire
vations, the differences should not exceed the following critical
ductility under torsional loading. Defective wire lowers torsion
dif
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