Mechano-chemical degradation effects on slow crack growth in polyethylene pipes with multiple cracks

In a chemically aggressive environment, polyethylene pipes are affected by oxidation-induced brittle fracture as follows: (i) multiple crack initiation through a thin degradation layer, (ii) mechano-chemical discontinuous slow crack growth of a main crack, and (iii) eventual fast fracture. A new analytical model for the second stage is proposed based on a modified crack layer theory. The mechano-chemical degradation of the process-zone medium was modeled theoretically by diffusion-reaction equation. Interactions between cracks immediately follow multiple crack initiations based on Green's function. Also, the parametric study involved several model parameters to provide a physical explanation. Further, this study proposed a theoretical method to estimate the crack lifetime by simulating crack initiation and slow crack growth periods, providing a new framework for predicting the durability of polyethylene pipes under aggressive chemicals.