Fatigue damage assessment of welded HDPE details evaluating their energy release

Abstract

In the recent years, high density polyethylene (HDPE) has been adopted in several industrial fields due to its good mechanical resistance, lightness and low cost, for the realization of pipelines. According to the current standards, welding techniques in such application have to guarantee a reliable connection of the different pipe sections but, on the other hand, they can also alter the mechanical performances of the polyethylene due to the heating procedure. Mechanical and fatigue tests should be performed in order to derive the working load conditions at which the pipe withstand without any failure or leakage of the internal fluid. Generally, traditional fatigue tests are extremely time-consuming and requires a huge amount of material. Recently, the Static Thermographic Method (STM) has been applied to a large set of engineering materials to evaluate the limit stress at which the material surface temperature trend deviates from the linearity during a static traction test, indicating the initiation of damage within the material. In the present work, the STM is applied on welded specimens made of PE100 in order to investigate its fatigue properties. The predicted limit stress has been compared with the fatigue limit obtained with traditional fatigue tests showing good agreement.