ASTM D 412 free standard pdf

Standard Test Methods for
Vulcanized Rubber and Thermoplastic Elastomers—
Tension

These test methods cover procedures used to evaluate
the tensile (tension) properties of vulcanized thermoset rubbers
and thermoplastic elastomers. These methods are not applicable to ebonite and similar hard, low elongation materials.
The methods appear as follows: 

• Test Method A—Dumbbell and Straight Section Specimens 
• Test Method B—Cut Ring Specimens

Terminology

Tensile set—the extension remaining after a specimen
has been stretched and allowed to retract in a specified manner,
expressed as a percentage of the original length. 

Tensile set-after-break—the tensile set measured by
fitting the two broken dumbbell pieces together at the point of
rupture.

Tensile strength—the maximum tensile stress applied
in stretching a specimen to rupture.

Tensile stress—a stress applied to stretch a test piece.

Tensile stress at-given-elongation—the stress required
to stretch the uniform cross section of a test specimen to a
given elongation.

Thermoplastic elastomers—a diverse family of rubberlike materials that unlike conventional vulcanized rubbers can
be processed and recycled like thermoplastic materials.

ultimate elongation—the elongation at which rupture
occurs in the application of continued tensile stress.

yield point—that point on the stress-strain curve, short
of ultimate failure, where the rate of stress with respect to
strain, goes through a zero value and may become negative.

Summary of Test Method

The determination of tensile properties starts with test
pieces taken from the sample material and includes the
preparation of the specimens and the testing of the specimens.
Specimens may be in the shape of dumbbells, rings or straight
pieces of uniform cross-sectional area.

 Measurements for tensile stress, tensile stress at a given
elongation, tensile strength, yield point, and ultimate elongation are made on specimens that have not been prestressed.
Tensile stress, yield point, and tensile strength are based on the
original cross-sectional area of a uniform cross-section of the
specimen

Measurement of tensile set is made after a previously
unstressed specimen has been extended and allowed to retract
by a prescribed procedure. Measurement of “set after break” is
also described.

 Significance and Use

All materials and products covered by these test methods must withstand tensile forces for adequate performance in
certain applications. These test methods allow for the measurement of such tensile properties. However, tensile properties
alone may not directly relate to the total end use performance
of the product because of the wide range of potential performance requirements in actual use.

Tensile properties depend both on the material and the
conditions of test (extension rate, temperature, humidity, specimen geometry, pretest conditioning, etc.); therefore materials
should be compared only when tested under the same conditions.

Temperature and rate of extension may have substantial
effects on tensile properties and therefore should be controlled.
These effects will vary depending on the type of material being
tested

Tensile set represents residual deformation which is
partly permanent and partly recoverable after stretching and
retraction. For this reason, the periods of extension and
recovery (and other conditions of test) must be controlled to
obtain comparable results.

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