Optimum creep lifetime of Polymethyl Methacrylate (PMMA) tube using rheological creep constitutive models based on experimental data

In this paper, the creep behavior of Polymethyl Methacrylate (PMMA) is investigated both experimentally and numerically at different temperatures (30, 40 and 50 degrees C) and stress levels. The experimental results show that PMMA has a nonlinear viscoelastic behavior. Hence, to model the creep behavior of PMMA, three types of constitutive models have been proposed: a) the generalized time hardening model, b) Burgers model, c) modified Burgers model. It was found that the generalized time hardening model, which has extensive applications in commercial softwares, predicts the creep behavior of PMMA at higher stress levels but it deviates from the experimental results at lower stress levels. Although, Burgers model predicts the creep behavior of PMMA, to improve the accuracy of the model a modified version of Burgers model has been proposed, which demonstrates very good consistency with the experimental data over the whole range of applied stresses and temperatures. Finally, the results are used to estimate the optimum creep lifetime of a rotating pressurized tube. A set of diagrams, which can be used in industry, have been produced based on each model.