Fracture Behavior for High Density Polyethylene pipes applying the crack front opening displacement method (CTOD).

Comportamiento a Fractura para las Tuberías de Polietileno de Alta Densidad Aplicando el Método del Desplazamiento de la Apertura del frente de Grieta (CTOD).

Abstract

This research is based on an experimental study of fracture mechanics that determined the mechanical behavior to fracture in PE-100 and PE-80 pipes. The tests were carried out on HDPE pipe samples obtained directly from pipes without any additional processing stage, in order to achieve a real characterization of their service behavior. The study is framed in MFEP trials applying the CTOD methodology, establishing the considerations and criteria required according to ASTM standards and ESIS. The experimental results allowed to elaborate curves δ vs. Δa to characterize the mechanical behavior of PE-100 and PE-80 pipes in the direction of the main, longitudinal and circumferential stresses, at the speed of 5 mm / min, and for thickness values of 8.5 ± 0, 5 mm and 15.0 ± 0.5 mm. The fracture toughness test procedure described in the ASTM-1820 standard of the CTOD for metallic materials was successfully applied in polymers, evaluating δIC for the start of stable crack growth at 0.2 mm. Furthermore, the determination of the δIC vs. Δa through the CTOD method allowed to characterize the fracture resistance of HDPE pipes in the stable growth ridge stage of the crack. The material of these pipes presented a high tenacity, which translates into a high plastic deformation in the front of the crack.