Fatigue Testing on POM and PA Plastics - ZwickRoell testing laboratory participates in CAMPUS? round robin tests

The ZwickRoell testing laboratory is currently performing fatigue tests on plastics (POM, PA66-GF35) as part of a round robin test organized by the CAMPUS? "Fatigue" working group. This group consists of experts from the automotive industry, plastic material manufacturers and testing equipment manufacturers. The goal of this group’s work is to define a uniform test methodology that can lead to better reproducibility of the test results between various testing laboratories through the precise definition of applicable test conditions.

The round robin test being performed over several months is based on the test method known internally at CAMPUS? as “Option X”. The standardized type A1 tensile specimen is tested to ISO 20753 with sinusoidal tensile stress at a stress ratio, r, of 0.1 in the tensile threshold range. The result is an S-N curve, which shows the number of vibration cycles until the specimen breaks as a function of the tensile stress level. To optimize the test sequence, Option X does not work with a fixed test frequency, rather it uses the force-displacement curve to determine the dissipated energy and, together with the respective current frequency, the current energy input, which is directly related to the heat development of the specimen. By continuously adjusting the frequency according to the current energy input, the heating of the specimen is limited to an appropriate level. Initial preliminary tests have already shown that a test time reduction of approximately 80% is realistic if the quality of the test results is good.

ZwickRoell participates in these tests by using an LTM 10 series electrodynamic testing machine that is equipped with software optimized for performing the Option X test sequence. Since the tests are performed at 80°C and 120°C, the machine is additionally equipped with a temperature chamber that ensures powerful air flow and also that the test temperature is accurately maintained.

We plan to submit this methodology to ISO as a standardization proposal, provided its suitability is confirmed in round robin tests.

About CAMPUS?:

CAMPUS ( CAMPUSplastics ) stands for Computer Aided Material Preselection by Uniform Standards and is a material information system for the plastics industry. It was established in 1988 by a group of raw material manufacturers. Currently, CAMPUS has 23 members. Its most important tasks include establishing a high degree of comparability between the measured values of different manufacturers, the uniform presentation of data, and support for international standardization work. The CAMPUS database (https://www.campusplastics.com) is considered globally leading in terms of the degree of standardization and thus comparability of characteristic values and the support of characteristics diagrams whereby this data is made available to qualified users free of charge.

Polyoxymethylene (abbreviated POM) is a high molecular weight thermoplastic with high crystallinity that is mainly used for the production of molded parts during the injection molding process and is widely used in the automotive industry.

Polyamide 66 (PA66-GF35) is a semi-crystalline thermoplastic with high strength and thermal stability, reinforced with a glass fiber content of 35%. Reinforced polyamides are engineering plastics and are used for many technical applications, including in automotive engineering. In the United States, PA66 is usually referred to as nylon.