Accelerated fatigue strength determination
Testing and calculation methods for the accelerated determination of fatigue strength curves for thermoplastics
Project duration
From: 01.08.2022 To: 31.07.2024Description
The material and component design of thermoplastic materials regarding the fatigue strength range is a big challenge. Time intensive and costly material tests are contrary to shortening development cycles, rising cost pressure and requirements aiming at resource efficiency as well as light weight construction. Within the research project an accelerated test and calculation procedure to characterize the materials fatigue strength was developed. Based on one force-controlled cyclic load increase test and two force-controlled fatigue (Wöhler) tests, the so called Wöhler line was physically based calculated. Therefore, the measured values of the strain amplitude, dissipated energy density and temperature changes, which result of the load applied, were mathematically described by power law functions. Thus, the link between cyclic load increase test and fatigue tests was determined. Using another power law equation and one reference point, the Wöhler line has been calculated. This requires a priori knowledge of a material specific constant, which could be determined for several materials. The calculation procedure was implemented in software. Provided that the material specific constant is known, a significant time and therefore costs saving for the Wöhler line estimation was demonstrated. Testing laboratories, which may provide the test procedure developed, and companies, which get access to cheaper fatigue data for their component design and may estimate their products long term performance, benefit from this.
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