PA and POM: Testing and Modeling of Viscoelastic-Viscoplastic Behavior
We needed to characterize the rate dependent cyclic behavior of POM and PA materials. Additionally, we needed to create material models for finite element analysis, whereby repetitive loading-unloading sequences needed to be described.
Our customer provided standard ISO specimens for testing. We did tensile tests to 50% of strain with some strain rates representing typical application conditions. Then we added some cyclic “yield point” tests. They consisted of loading-unloading-retraction sequences at increasing stress levels. For validation purposes we added a cyclic relaxation test.
It is known that modeling retraction is a tricky task. We solved this problem using a multiphase viscoelastic-viscoplastic material model. We are proud we were able to correctly model the monotonous and cyclical behavior of these materials with high fidelity.