Application of a master curve and the modified superposition principle for modeling creep and loading rate effects at small strains in high-density polyethylene

Abstract

Studying the nonlinear viscoelastic behavior of high-density polyethylene (HDPE) at small strains and stresses is still a matter of interest in engineering applications such as laying submerged pipelines. Although sound modeling of such behavior requires complex phenomenological or micromechanical constitutive laws, many works have focused on the development of simplified procedures for approximating this type of nonlinear response. Usually, when these simplified methods are employed to reproduce creep behavior, they are not capable to simultaneously provide good estimates for traction tests even at constant stress or strain rates. This work describes a methodology, which has shown a good compromise to reproduce both types of responses within a given stress range. The procedure can be understood as an interpolative approach based on a master curve and the modified superposition principle to account for nonlinear effects. With this strategy, it is possible to predict the nonlinear creep behavior for an HDPE sample subjected at any constant stress level within a given experimental range. Once this predictive capability is achieved, we use an incremental algorithm based on the modified superposition principle to simulate traction tests at constant strain rates. We show that the combined application of the proposed master curve approach and the modified superposition principle results in good approximations for creep tests and simultaneously leads to remarkable agreement with experimental traction tests reported in the literature.