Abstract
Temperatures of −25 °C, +5 °C, and +35 °C were selected to study the creep behavior of high-density polyethylene (HDPE). The ultimate tensile strength of HDPE materials was obtained through uniaxial tensile experiments and the time–strain curves were obtained through creep experiments. When the loaded stress levels were lower than 60% of the ultimate strength, the specimens could maintain a longer time in the stable creep stage and were not prone to necking. In contrast, the specimens necked in a short time. Then, the time hardening form model was applied to simulate the time–strain curve and the parameter values were solved. The parameter values changed exponentially with the stresses, thereby expanding and transforming the time hardening model. The expanded model can easily and accurately predict creep behaviors of the initial and stable creep stages as well as the long-term deformations of HDPE materials. This study would provide a theoretical basis and reference value for engineering applications of HDPE.
Highlights
From the stress–strain curves, it can be seen that the elastic modulus and yield stress of high-density polyethylene (HDPE) materials have a great relationship with the strain rate
HDPE materials are susceptible to temperature and the properties are greatly affected by the temperatures
This study study is is intended intended to to investigate investigate tensile tensile creep creep behavior behavior by by creep creep experiments experiments and and expand the time hardening form model
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. Polymer materials must maintain the loading state for a long time in the applications of daily life. It is easy to produce warpage deformations in the molding process, it is unable to bear heavy pressure and tension, poor mechanical properties at high temperatures, obvious aging phenomenon, and so on. It is vital to understand the evolution processes of creep to predict the load-bearing capacity of the polymer structures and the deformations after long-term use. The Monkman–Grant relationship is another useful creep model that has been widely applied to metallic materials [14] These empirical models could simulate the creep curves of polymers, it takes many experiments to determine the long-term creep behaviors of polymers, which requires a lot of time. The curves drawn by the expanded model in comparison with the test curves and the curves simulated by the time hardening model results were in good agreement
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