ISO 34 Tear Growth Test Rubber and Elastomers
ISO 34-1/-2 describes methods for determining the tear strength or tear resistance of various specimens (trouser or strip specimens, angle specimens, crescent-shaped specimens, Delft specimens) made of vulcanized or thermoplastic elastomers.
The following content explains the key aspects. For standard-compliant testing to ISO 34-1 and ISO 34-2, however, it is essential to purchase the complete standard. Further methods for determining the tear strength of elastomers are described in ASTM D624.
ISO 34 is only concerned with methods for testing the tear resistance of elastomers. The determination of mechanical properties of rubber in the tensile test, such as tensile stress, tensile strength and strain at break are described in ISO 37, DIN 53504 and ASTM D412.
Objectives & application Specimen Specimen preparation Running a test Testing system & accessories Automation FAQ Request a consultation
ISO 34 Objective & Applications
The application of ISO 34 ensures that tests can be carried out reproducibly and comparably independently of the laboratory. The standard defines the requirements for specimen geometry, test speed, conditioning and the evaluation of the results.
The standards are applied wherever elastomers are used and mechanical stress from cracks poses a critical risk, such as in the automotive industry, rubber manufacturers or medical devices.
ISO 34-1/-2 Specimen preparation
The specimens to ISO 34-1/-2 must be cut from a uniformly thick elastomer plate with a thickness of 2.0 mm ± 0.2 mm. The punching die used to produce the specimens must correspond to the dimensions specified in the standard. The specimens must be cut out of the plate with a single stroke of the press by punching.
ISO 34-1 describes four methods:
- Method A: Use of a strip specimen
- Method B, procedure a: Use of an angle specimen without notch
- Method B, procedure b: Use of an angle specimen with notch
- Method C: Use of a crescent-shaped specimen
Depending on the method, the specimens must be cut or notched to the depth specified in the standard using specified equipment.
Running a test
ISO 34-1: The specimen is clamped in the testing machine and stretched at a separation speed of 500 mm/min ± 50 mm/min for angled and crescent-shaped specimens and 100 mm/min ± 10 mm/min for strip specimens until the specimen tears. For angled specimens and crescent-shaped specimens, the maximum force is to be recorded, for strip specimens, the entire force curve during the tearing process.
ISO 34-2: The specimen is secured in the testing machine in such a way that the free length between the contact points of the clamps on the specimen is 30 mm, i.e. that each clamp is 15 mm away from the slot. The specimen is stretched until it is completely torn. The maximum force achieved during tearing is recorded.
ISO 34-1/-2 Testing systems
For the test to ISO 34, the detection of the elongation of the specimen is crucial. So that the extension can be reliably recorded until break, both the travel distance of the crosshead must be long enough and the load frame must be designed to be correspondingly high. ZwickRoell offers the right universal testing machines for this:
- zwickiLine – space-saving solution for small test loads up to 5 kN and with a test range up to 1365 mm
- ProLine - for standard-compliant tests and simple applications with a test area from 1050 mm to 1450 mm
- AllroundLine - adaptable and versatile with a test area from 1030 mm to 2560 mm
Specimen grips for tests to ISO 34
According to ISO 34-1, the testing machine must be equipped with specimen grips that automatically tighten as the tensile force increases and exert uniform pressure on the stretched ends of the specimen. The specimen must be clamped symmetrically and in line with the axis of the tensile direction in the specimen grips. ISO 34-2 does not specify any specific specimen grips. Pneumatic grips or screw grips can also be used for testing to ISO 34-1/-2.
In the pneumatic grips from ZwickRoell, the gripping force is generated by pneumatic actuators. It can be operated with a hand or foot control. Gripping force independent of the tensile force ensures a constant test speed over the course of the entire test sequence.
Do you have any questions about your test requirements or challenges with the ISO 34-1/-2? Please contact our experts.
They will be glad to provide the information you need!
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Automated tensile test to ISO 34
Tensile tests on rubber and elastomers to ISO 34, can also be automated, meaning they can be performed with fully automatic specimen feeding. An automated testing system is primarily used when many specimens need to be tested, or when operator influences must be eliminated. Hand temperature or moisture, as well as inaccurate or angled positioning of the specimen in the specimen grips, can affect the test results.
- For large specimen series, our experts recommend the compact robotic testing systemroboTest L. It can autonomously perform tensile tests on up to 350 specimens and can be used 24/7. A thickness measuring device integrated in the system measures the specimen thickness with accuracy and reproducibility.
- The robotic testing system roboTest R is more complex and allows you to connect additional devices such as a specimen marking station or a temperature chamber for accurate tempering of the specimen.
- To avoid operator influences even with small specimen series, ZwickRoell has the testing system ALEX in its portfolio: simple, compact, and cost-effective, it can be used with a series as small as 10 specimens.
Downloads
- Product Brochure: Testing machines and testing systems for plastics and rubber PDF 9 MB
- Product Information: lightXtens: non-contact, simple, and fully automated testing of high-extension materials PDF 886 KB
- Product Information: videoXtens 1-270 P PDF 1 MB
- Product Information: multiXtens II HP extensometer PDF 1 MB
- Product Information: Robotic testing system roboTest L (linear) for plastics PDF 71 KB
- Product Information: Robotic testing system roboTest R (polar) for plastics PDF 86 KB
- Product Information: ALEX - The automated lab expert PDF 308 KB
Frequently asked questions about ISO 34-1/-2
ISO 34-1 and ISO 34-2 specify methods for determining the tear resistance of elastomers and thermoplastic elastomers. For this purpose, standardized specimens (strip specimens, angle specimens, crescent-shaped specimens, Delft specimens) are clamped and tested under tensile load until the specimen is torn.
ISO 34-1 offers several specimen shapes (e.g., strip, angle and crescent-shaped specimens) to represent different stress situations. ISO 34-2 describes the determination of the tear strength of Delft specimens. ASTM D624 works with five defined specimen geometries (types A–E) and is more oriented towards US practice. The test results are not directly reproducible, as the specimens and test conditions are different.
The tear resistance according to ISO 34-1 is, for strip specimen, the median of the force required to enlarge a cut in a defined specimen by tearing, divided by the thickness of the specimen. In an angle specimen, the tear resistance is the maximum force required to tear open or tear apart the incision of a fixed specimen, divided by the thickness of the specimen.
In ISO 34-2, the tear resistance is calculated by multiplying the maximum force measured during the tearing of the Delft specimen by the fixed standard factor 8 and dividing by the actual width next to the slot and the thickness of the specimen.
