Sealing technology manual for the process industry

Tensile test Tensile tests are used to determine the tear strength, tensile strength, elongation at break, and the stress val- ues of elastomeric materials. The test specimens used for this purpose are usually tensile bars or standardized rings with rectangular cross-sections. These are stretched at a constant speed to break. In the tensile test according to DIN 53504, as many points as possible of the force-length change curve (tensile force with corresponding change in length of the sample) are recorded. The following values can be calculated from the experiment: 1.The tear strength is the quotient of the force achieved at the moment of rupture and the initial cross-section of the specimen 2.The tensile strength is the quotient of the measured maximum force and the initial cross-section of the speci- men. Tear strength and tensile strength are generally the same in elastomers, if the measurement is performed at room temperature or above 3. The elongation at break is the ratio of the length change achieved at the moment of rupture to the initial length 4.The stress value is defined as the quotient of the tensile force existing when a certain elongation is achieved and the initial cross-section The three characteristics tear strength, 100% stress value and elongation at break are indicated on the material data sheets of the Freudenberg elastomers. They describe the behavior of the respective material to tensile stress. Resistance to tear propagation The tear propagation resistance is a measure of the sen- sitivity of elastomers in the event of cutting and tearing damage. The most common test to determine tear propa- gation resistance is the strip test according to DIN ISO 34-1 (DIN 53 507). In this case, a longitudinal cut is made in the material to be tested, the two half-strips are clamped in a pulling machine and pulled apart. The force subtended by the test specimen to the tear propagation is measured in relation to the sample thickness. A further testing method is the angle test specimen ac- cording to DIN ISO 34-1 (DIN 53 515). Here, an incision is made in an angled (“bent”) sample manufactured in a form, and the sample is similarly pulled apart using a pull- ing machine. The measured values do not need to correlate with the stress values determined in the tensile test. Since the results of the tear propagation resistance test strongly depend on the specific test conditions and particularly on the shape of the sample, it is crucial that the test meth- od and the sample shape are always indicated when the results are stated. Technical fundamentals 24 (DIN 53507). In this case, a longitudinal cut is made in the cording to DIN ISO 34-1 (DIN 53515). Here, an incision is

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