Probabilistic life prediction of plastic pipes using an equivalent crack growth model

The life prediction of gas pipelines is important for maintaining the functionality of the infrastructure. A new life prediction methodology for plastic pipes due to creep deformation is proposed in this paper. The key idea is to use an equivalent crack growth process to describe the damage accumulation and failure process of plastic pipes. An asymptotic stress intensity factor (SIF) solution which considers the effect of stress concentration due to manufacturing (e.g., squeezing process) and environmental conditions (e.g., rock impingement) was used in the model. A power law crack growth model is proposed and the life is calculated by integrating the crack growth function from the initial crack length to the critical crack length. Following this, the proposed model is demonstrated and validated with experimental data for various conditions. The model parameter is calibrated using one group of testing data for Aldyl-A pipes without geometry concentration (e.g., baseline data). Experimental data with different types of stress concentration are used to validate the proposed life prediction method. Due to the large scatter in the experimental data, uncertainty quantification and Monte Carlo simulation are used for probabilistic life prediction. The error scatter predicted from the proposed model is validated with the experimental observations. Finally, some conclusions and future work are drawn based on the proposed study.