Xiaoli Shen

On collapse failure analysis of subsea corroded sandwich pipelines under external pressure

Subsea pipelines are essential equipment in ocean engineering. The development of oceanic exploitation of subsea oil and nature gas has gone into deeper and deeper areas and sandwich pipelines (SPs) are required in this area. In this paper, the effect of local corrosion on the collapse pressure of SPs is investigated through comprehensive finite element analysis. It can be found that the elastic bifurcation or buckle of externally corroded SPs could be categorized into global buckling mode and local buckling mode. The buckle mode is effect by the corroded location, the corrosion depth, the elastic moduli and the thickness of the core layer. While the SPs buckle as a whole, the critical pressure decreases with the corrosion depth and angular extent increasing. Increase the thickness and elastic moduli can increase the critical pressure.

On the collapse failure of dented pipes under bending moment and external pressure

This paper presents the numerical research on the collapse failure of dented subsea pipelines under bending moment and external pressure. Firstly, the case of pure bending moment is studied and shows that the increase of initial denting displacement and ratio of diameter to thickness leads to decreased critical moment. Then the external pressure is imposed, and it is concluded that the non-dimensionalized critical bending moment decreases with the increase of the pre-applied external pressure and the initial denting displacement. If the bending moment is applied to the dented pipe before the external pressure, the collapse pressure would decrease to some extent. This paper is expected to provide the security guidelines to dented pipes under bending moment and external pressure.

Collapse of dented subsea pipelines under external pressure

In this work, collapse of subsea pipelines subjected to external pressure which are dented by foreign objects is investigated through numerical method. The effect of diameter-to-thickness ratio D/t and ovalization caused by denting Δom on the collapse pressure is discussed. Of particular concern is the effect of indenters shape on the collapse pressure. The collapse behavior between pipelines dented by spherical and ellipsoidal indenters are compared. Finally, an empirical equation is proposed to predict the collapse pressure of dented pipelines under external pressure.