Constitutive model calibration of the time and temperature-dependent behavior of high density polyethylene

Abstract

HDPE is commonly used in pipelines and piping for industrial and societal infrastructure. Like most polymers, HDPE's mechanical properties are sensitive to temperature and show time dependent properties. The temperature effect on both the short and long term compressive and tensile behavior of HDPE, in a combined manner, have not been investigated thoroughly in the past. Especially the constitutive behavior of HDPE, incorporating temperature effects on its long and short term behavior, could be essential when designing such infrastructural components. Hence, the temperature effect on the short and long term response in tension and compression of HDPE is investigated in this study. The short term tensile and compressive stress-strain behavior at 23, 40, 60, and 80 °C were obtained through experiments at constant displacement rate and temperature. Tensile and compressive stress relaxation (e.g. long term) behavior at 23, 40, 50, 60, 70, and 80 °C were investigated through stress relaxation tests. The experimental results from the short term tests showed that both the tensile and compression moduli and yield strength of HDPE decrease linearly with the increase in temperature. It is also shown from the long term test that relaxation modulus in tension and compression are highly dependent on temperature. Based on the experimental results, the constitutive three network model (TNM) was calibrated and implemented in a FEA model, which was then validated through a three point bending (3 PB) relaxation test with a prescribed temperature profile. The FEA model and the calibrated model results agree markedly well with the experimental results, which indicates that the model can be used reliably to predict the temperature dependent short and long term behavior of HDPE in design and analysis of HDPE components.