The overriding goal of testing molding materials is to achieve a high degree of reproducibility. 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. Decisive is therefore the measurement range in which a test machine achieves the specified class accuracy. Due to the viscoelastic properties of polymers, mechanical properties different from those measured on a standardized test specimen normally result under altered strain rates. 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.
An instrumented pendulum impact tester can determine additional characteristic values, such as maximum tensile force. A major advantage of the flexure test is the relatively easy measurement of low specimen strains. An extensometer is used to determine elongation and tensile modulus. Durch definierte Versuchsbedingungen wird eine Vergleichbarkeit der an verschiedenen Proben bzw. 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.
Möglicherweise unterliegen die Inhalte jeweils zusätzlichen Bedingungen. This additional requirement states that the measurement path between the beginning and end of modulus determination must be measured with an accuracy of 1%. When a specimen is subjected to a flexure load, the specimen thickness measurement error has a quadratic effect. The high-speed tensile test can be performed using drop weight testers or hydraulic high-speed tensile testing machines. For this reason the flexure test, unlike the tensile test, can be used only for low specimen strains. However, the loads on a component or structure in actual service may lie within a very wide range of the deformation rate.
Room temperature usually refers to a somewhat wider temperature range, between 18 °C and 28 °C. 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. If you have any questions or suggestions regarding the accessibility of this site, please. Werkstoffen ermittelten Werte sichergestellt, die jedoch nicht mit den an einem Bauteil praktisch auftretenden Belastungen identisch sein müssen. If strong orientations are present in the material, the result will be differences in measured values as compared to the tensile test.
Along with a defined relative in percentage error, the class specifications for measuring extension also include a specification for an absolute error, which occurs when measuring smaller extensions. The use of extensometers is not necessary, and thin, waisted specimens can be used. All copyright requests should be addressed to. This would result in a correspondingly large measurement error. The contact surface is flat and circular with a diameter of 6.
For example, a caliper is normally used to measure the overall length of hard plastics larger than 10 mm. These characteristic values are mostly used for comparison purposes. Specifications for the conditioning duration can usually be found in the material standards for the plastic being tested. Often only the maximum tensile stress is used for assessment of this behavior. Any use, including reproduction requires our written permission. Since surface pressing during measurement cannot be checked, measurement accuracy is rather low even if the resolution of the caliper is high. The ratchet limits the measurement force to 5—15 N.
Insbesondere verhalten sich viele Kunststoffe , was zusätzliche Charakterisierungsmethoden erforderlich macht. However, since high-accuracy, easy-to-use extensometers are now available the significance of this advantage plays less of a role. In addition to the reading accuracy of the measuring equipment, the size and form of the contact element and the applied surface pressing during measurement also play an important role. The chamber has internal electric heaters for elevated temperatures and uses external carbon dioxide gas as a coolant for reduced temperatures. This means that a deviation of up to 6 µm may exist between measurements at the beginning and end of the modulus range. This device holds the specimen during measurement and determines the dimensions with four digital measuring transducers, a defined measurement force, and sensor feet.
Testing machines measure two fundamental values: force and extension. This requires limiting the number of specimen types. Most test standards require a measurement accuracy of 1% for the measured value. 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. A gage length of 50mm is specified for Type 1B specimens due to the larger radius resulting in a shorter parallel area.
In the standardized tensile test, results are based on a defined specimen pull-off speed on the specimen. 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. Tests at high or low temperatures are also possible, for which differing requirements can be specified. With a conventional pendulum impact tester, only energy values can be determined, however, and the pull-off speeds are generally limited to around 3. The chamber is designed to allow the test mounts from the base and crosshead of the universal tester to pass through the top and bottom of the chamber. This test offers a simple method for determining a tensile property at a high loading rate using a pendulum impact tester.
Durch die Nutzung dieser Website erklären Sie sich mit den und der einverstanden. Almost all modern testing machines today achieve Class 1 accuracy, or even Class 0. Whether your business is local or global, we can ensure your products meet quality, health, environmental, safety, and social accountability standards for virtually any market around the world. Procedure: Specimens are placed in the grips of the universal tester at a specified grip separation and pulled until failure. This could be angular errors resulting from mechanical processing or sink marks and minor draft angles in injection molded specimens. Specimens are usually produced by injection molding. They are generally machined from pressed or injection molded sheets.