ASTM D412 Tensile Set (Elastomers)

ASTM D412 Tensile Set (Elastomers) Scope:

ASTM D412 is a standard test method for determining the tensile properties of thermoplastic elastomers and thermoset rubber. A wide variety of products and consumer goods is manufactured from this family, such as tires, vehicle components, pitch game balls, and rubber bands. Tensile properties are dependent upon the material under stress, and the conditions under which the test is ongoing such as specimen geometry, pretest conditioning, extension rate, temperature, and humidity. This is a significant reason why materials should always be compared under similar conditions. Space shuttle O-rings, which must critically perform under ultimate temperature and pressure conditions, are also a specialized product of this family. 

For the purposes of this standard, values expressed in either SI or non-SI units must be regarded independently as normative. Each system must be utilized separately without merging values since the values in each system could not be exact equivalents.

Test Procedure:

ASTM D412 tests the elasticity of a material while undergoing tensile strain and records its behavior after the stress is released. ASTM D412 is carried out on a universal testing machine (tensile testing device) while maintaining a 500 ± 50 mm/min speed until the specimen undergoes failure. For maintaining the appropriateness of the test, specimens are held at 90 degrees to the jaw faces and any tilt is avoided. Misalignment of specimens may cause major variations in test result charts. Therefore, consistent alignment is ensured for each test. There are two test methods: Test method A – Dumbbell and straight section specimens and Test Method B – Cut ring specimens. Identical results may not be produced with the same specimen with these methods.

After stretching and retraction, residual deformation, that is partially permanent and partially reversible, is represented by the tensile set. To acquire comparable results, the times of extension and recovery (as well as other test circumstances) must be under control.

Materials should only be compared when tested under the same conditions because tensile qualities are dependent on both the material and the performance parameters (extension rate, temperature, humidity, specimen shape, pretest conditioning, etc.). Temperature and rate of extension should be regulated because they may have a significant impact on tensile characteristics. Depending on the kind of substance being examined, these impacts will change.

Video 01: ASTM D412 Rubber and Elastomer Testing

Specimen size:

ASTM D412 standard outlines six permissible brackets of dogbone samples for ASTM D412 testing and two permissible brackets of cut ring samples. A typical test shape is a die-cut C dogbone sample, which requires an overall length of 115 mm (gauge length 25 mm), a circumference of 6 mm, and a thickness of 3 mm. The median value being the accepted value, the thickness of the sample is measured three times.

Data:
Tensile strength
Tensile stress at a given elongation
Ultimate elongation
Tensile set
The values stated in SI or non-SI units shall be observed separately as inflexible for this standard.

Conclusion

With the method described above, an accurate stress value at a specified elongation of the material can be easily obtained. ISO 48 is the ISO standard that is comparable with ASTM D412. Infinitalab has a strong history of helping our clients to perform this test successfully and affordably.