ASTM D412-98a(R2002) pdf free.Standard Test Methods for Vulcanized Rubber and Thermoplastic Rubbers and Thermoplastic Elastomers-Tension.
These test methods describe procedures used to evaluate the tensile (tension) properties of vulcanized rubbers and thermoplastic rubbers and thermoplastic elastomers. The test 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
Note 1- these two different methods do not produce identical results.
1.2 The values stated in either SI or non-SI units shall be regarded separately as normative for this standard. The values in each system may not be exact equivalents; therefore each system must be used independently, without combining values.
1.3 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.
4. Summary of Test Method
4. 1 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.
4.2 Measurements for tensile stress, tensile stress at a given elongation, tensile strength. yield point, and ultimate elongalion 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.
4.3 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.
5. Signilicance and Use
5. 1 All materials and products covered by these test methoils must withstand tensile forces for adequate performance in certain applications. These Lest methods allow for the measurement of such tensile properties. However, tensile properties alone may not directly relate to the total end USC performance of the product because ot the wide range of potential peiThrmance requirenlents in actual use.
5.2 Tensile properties depend both on the material and the conditions of test (extension rate, temperature, humidity. specimen geometry, pretest conditioning. etc.); therefore materials should he compared only when tested under the same conditions.
5.3 Temperature and rate of extension may have substantial cffccts on tensile properties and therefore should bc controlled. These effects will vary depending on the type of material being tested.
5.4 Tensile set represents residual defornation 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.
17. Calculation
17.1 Stress-strain propertics for ring specimens arc in general calculated in the same manner as br dumbbell and straight specimens with one important exception. Extending a ring specimen generates a nonuniform stress (or strain) field across the width (as viewed from left to right) of each leg of the ring. The initiul inside dimension (circunifei-ence) is less than the outside dimension (circumference), therefore for any extension of the grips, the inside strain (or stress) is greater than the Outside strain (or stress) because of’ the differences in the initial (unstrained) dimensions.
17.2 The following options are used to calculate stress at a specified elongation (strain) and breaking or ultimate elongation.
17.2.1 Stress tit a Specified Elongation —The mean circumference of the ring is used for determining the elongation. The rationale for this choice is that the mean circumference best represents the average strain in each leg of the ring.
172.2 l]ltimnt (Breaking) Elongation —This is calculated on the basis of the inside circumference since this represents the maximum strain (stress) in each leg of the ring. This location is the most probable site for the initiation of the rupture process that occurs at break.ASTM D412-98a(R2002) pdf free download.