Nonlinear response of viscoelastic polyoxymethylene (POM) at elevated temperatures

In this study we present experimental results and a constitutive model for predicting the nonlinear viscoelastic response of polyoxymethylene (POM). Relaxation and creep tests under relatively low strains are conducted at room temperature. The nonlinearity is analyzed by conducting the aforementioned tests at several stress or strain levels at higher temperatures. To complete the characterization, monotonic tensile tests at several strain rates and temperatures are presented. We use the quasi-linear viscoelastic (QLV) model to simulate the viscoelastic behavior of POM. We modify the QLV model by introducing a strain- and temperature-dependent relaxation function in order to predict the response of POM for strains up to 5% and temperatures ranging from 23 °C to 80 °C. For computational purposes we present a numerical algorithm for the time-integration of the QLV model with prescribed strains. We further discuss an inverse method to find the strain response to a given stress history, which is used to study the creep response of the POM.