Tensile Testing of Plastics ISO 527
The ratchet limits the measurement force to 5—15 N. The chamber has internal electric heaters for elevated temperatures and uses external carbon dioxide gas as a coolant for reduced temperatures. Due to the viscoelastic properties of polymers, mechanical properties different from those measured on a standardized test specimen normally result under altered strain rates. For this reason the flexure test has been the preferred test for modulus measurement for a long time. Werkstoffen ermittelten Werte sichergestellt, die jedoch nicht mit den an einem Bauteil praktisch auftretenden Belastungen identisch sein müssen. The orientations of the polymer normally differ significantly from those in injection molded specimens.
Flexure tests are performed at loading rates similar to those for tensile tests and therefore provide similar material characteristics. This means that a deviation of up to 6 µm may exist between measurements at the beginning and end of the modulus range. However, since high-accuracy, easy-to-use extensometers are now available the significance of this advantage plays less of a role. For this reason the characteristic values determined in a tensile test are only of limited suitability for component design, but represent a very reliable basis for material comparisons. Defined conditioning and ambient conditions Observing defined conditioning and ambient conditions with regard to temperature and humidity is of great importance for the comparability of test results.
When a specimen is subjected to a tensile load, the measurement error is reflected linearly by the stress result. For this reason the flexure test, unlike the tensile test, can be used only for low specimen strains. Decisive is therefore the measurement range in which a test machine achieves the specified class accuracy. The size of the chamber places a limitation on the maximum elongation that can be reached, and extensometers are generally limited to no more than 200° C. Furthermore, specimens used in tests on molding materials must be kept in a standard atmosphere standardized temperature and humidity conditions for at least 16 hours prior to the test.
The high-speed tensile test can be performed using drop weight testers or hydraulic high-speed tensile testing machines. Any use, including reproduction requires our written permission. Sub-tropical atmosphere: 27 ± 2 °C, 65 ± 10% r. This requires limiting the number of specimen types. Standard test fixtures are installed inside the chamber, and testing is conducted inside the controlled thermal environment the same as it would be at ambient temperature. Exact determination of specimen dimensions Determining the specimen dimensions can result in a relatively high number of stress value errors. Almost all modern testing machines today achieve Class 1 accuracy, or even Class 0.
For soft plastics and films, it is imperative that the measurement force is strictly observed. In addition, the use of direct extension measurement on the specimen is possible, allowing informative stress-strain diagrams to be generated. A gage length of 50mm is specified for Type 1B specimens due to the larger radius resulting in a shorter parallel area. Aging tests: The tensile test provides a good basis for demonstrating the change in the mechanical characteristic values of a polymer following aging, heat or medium aging, or weathering. This means you can measure the modulus values and tensile stress of many materials with the same test arrangement and without having to reconfigure the arrangement. Inherent to the method, the flexure test is more accurate in characterizing the material condition on the surface of the specimen.
Wikipedia® ist eine eingetragene Marke der Wikimedia Foundation Inc. Testing machines measure two fundamental values: force and extension. For example, a caliper is normally used to measure the overall length of hard plastics larger than 10 mm. Sometimes, individual test standards contain additional specifications. A small cross-section is advantageous for all aging procedures which progress from the surface of the specimen. Durch definierte Versuchsbedingungen wird eine Vergleichbarkeit der an verschiedenen Proben bzw. If strong orientations are present in the material, the result will be differences in measured values as compared to the tensile test.
Injection molded specimens display decreasing orientation as the distance from the feed point increases, leading to non-constant mechanical property curves along the length of the specimen, and therefore frequently resulting in specimen break on the side away from the gate. Tests at high or low temperatures are also possible, for which differing requirements can be specified. The tolerances correspond to class 2. In this tensile test, essential mechanical properties of molding material are determined. Often only the maximum tensile stress is used for assessment of this behavior. Insbesondere verhalten sich viele Kunststoffe , was zusätzliche Charakterisierungsmethoden erforderlich macht.
Specifications for the conditioning duration can usually be found in the material standards for the plastic being tested. However, the loads on a component or structure in actual service may lie within a very wide range of the deformation rate. A major advantage of the flexure test is the relatively easy measurement of low specimen strains. As part of periodic calibration when compared to a measuring instrument based on national standards, evidence has shown that these measured values achieve a level of accuracy defined in the test standard across defined measuring ranges. The overriding goal of testing molding materials is to achieve a high degree of reproducibility.
All copyright requests should be addressed to. The high-speed tensile test also provides valuable parameters for crash simulations. The thickness and width of the specimen is normally determined by a micrometer screw with ratchet. For this, the characteristic values of the tensile test are determined in the newly molded state, as well as after defined aging or weathering periods. Depending on the gage length used, this sometimes results in significant differences by definition, in particular when measuring small extensions. Room temperature usually refers to a somewhat wider temperature range, between 18 °C and 28 °C.