Eduardo Ribeiro Malta

Simplified Finite Element Models to Study the Dry Collapse of Straight and Curved Flexible Pipes

Dry collapse is one of the possible failure modes of flexible pipes. It refers to the situation in which no damage occurs in the flexible pipe external sheath. In this scenario, all layers of the pipe withstand the external pressure loading in a deep-water application. Such a situation is addressed in this work, which proposes some simplified modeling techniques to represent straight and curved flexible pipes subjected to external pressure, undergoing dry collapse during simulation procedure. The results of the proposed models are compared to other reference results, from a fully three-dimensional (3D) finite element model. Good agreement has been got, even with the proposed simplifications with a large reduction in computational cost when compared to full 3D model.

Finite Element Analysis of Flexible Pipes Under Compression

Axial compressive loads can appear in several situations during the service life of a flexible pipe, due to pressure variations during installation or due to surface vessel heave. The tensile armor withstands well tension loads, but under compression, instability may occur. A Finite Element model is constructed using Abaqus in order to study a flexible pipe compound by external sheath, two layers of tensile armor, a high strength tape and a rigid nucleus. This model is fully tridimensional and takes into account all kinds of nonlinearities involved in this phenomenon, including contacts, gaps, friction, plasticity and large displacements. It also has no symmetry or periodical limitations, thus permitting each individual wire of the tensile armor do displace in any direction. Case studies were performed and their results discussed.© 2014 ASME

Finite Element Analysis of Flexible Pipes Under Compression: Influence of the Sample Length

In order to study the compressive behavior of flexible pipes, a nonlinear tridimensional finite element model was developed. This model recreates a five layer flexible pipe with two tensile armor layers, an external polymeric sheath, an orthotropic high strength tape and a rigid inner nucleus. Using this model, several studies are being conducted to verify the influence of key parameters on the wire instability phenomenon. The pipe sample length can be considered one of these parameters and its variation causes significant change at the stability response of the tensile layers. This article includes a detailed description of the finite element model itself and a case study where the length of the pipe is changed. The procedure of this analysis is here described, along with the results.Copyright

Finite Element Modeling of Flexible Pipes Under Crushing Loads

The launching procedure can be one of the most critical stages of the operational lifetime of a flexible pipe. From the beginning of the pipe unrolling off the reel to the moment of its separation from the launching vessel, the flexible pipe is subjected to severe loads such as crushing and tension. This paper focuses on the crushing load applied to the flexible riser by the shoes of the caterpillars on the launching vessel. The objective is to present an effective methodology to evaluate the stresses at the structural nucleus of a flexible pipe during launching using the Finite Element Method. Firstly, a tridimensional ring model is used to represent the structural nucleus of the flexible pipe. In that model, the geometry of the interlocked carcass and the pressure armor is accurately represented. Then, similar models are constructed including a series of geometry simplifications. Those simplified models are compared to the baseline in order to evaluate the relevancy of an accurate representation of the geometry of the metallic layers. The results of these comparisons are presented and discussed.Copyright