This study investigates the collapse mechanisms and capacity of the faceted pipe against the conventional pipe under external hydrostatic pressure. The experimental protocol is comprised of additively manufactured (3D-printed) faceted and conventional titanium pipes (Ti6Al4V-0406) tested inside a 30MPa hyperbaric chamber. A finite element analysis (FEA) is presented and is validated against the experimental results. Using the validated FE model, the major geometric parameters affecting the collapse capacity of faceted pipe were investigated. The proposed FE model can accurately predict the collapse pressure of faceted and conventional pipes. Results showed that the faceted pipe can boost the collapse capacity by at least an 80% increase compared to the conventional pipe. Also, the collapse mode was observed
In today's world, subsea pipeline systems are construed as the most influential means to transport oil and gas. The rapid development that the oil and gas industry has witnessed necessitates the construction of thousands of kilometres of pipelines across the world. Given that these pipelines are lengthy, it is highly probable that they cross active faults (on land and in the sea); accordingly, they are in constant exposure to various catastrophic hazards. The characteristic distinguishing this kind of pipeline from other structures constructed on the ground is that the inertial forces exerted by the pipe's weight and its content are not very important.
The most important structure damages occurring in pipelines are caused by collapse pressure if the external hydrostatic pressure of the pipeline is larger than its critical pressure. As a failure form, collapse will not only produce enormous economic loss but also result in large catastrophe to the ocean environment and ecosystem system (Drumond et al., 2018). Therefore, this phenomenon causes fracture in the pipe wall which is investigated by several researchers (Yeh and Kyriakides, 1986; Gong et al. 2013; He et al. 2014; Alrsai et al. 2018b) or leads to local buckling. A local buckle, ovalization, dent, or corrosion in the pipe wall can quickly transform the pipe cross-section into a dumb-bell shape that propagates along the pipeline as long as the external pressure is high enough to sustain propagation.
