1 Copyright © 2013 by ASME EFFECT OF MATERIAL PLASTICITY AND METALLIC LAYER PROFILES ON THE CRUSHING RESISTANCE OF FLEXIBLE PIPES Marcel Sato marcel.sato@prysmiangroup.com Rafael L. Tanaka rafael.tanaka@prysmiangroup.com Elson L. Albuquerque elson.albuquerque@prysmiangroup.com Rafael G. Morini rafael.morini@prysmiangroup.com Carlos A. F. Godinho carlos.godinho@prysmiangroup.com Prysmian Surflex Umbilicais e Tubos Flexíveis do Brasil Vila Velha, ES, Brazil ABSTRACT This paper presents a numerical 3D finite element model to simulate a flexible pipe under crushing-traction condition, which is a typical situation found during its laying operation. This model considers the geometry of some layers from the flexible pipe, responsible of providing the most contribution to its radial strength (e.g., interlocked carcass, internal polymeric layer, pressure armor, and external polymeric layer) and geometry of laying system shoes. It also considers the flexible pipe initial ovalization and the squeezing effect due to the tensile armor layers under traction. A numerical-experimental comparison is presented, in order to show the model validity. Keywords: Flexible pipe, crushing tests, numerical finite element model, experimental results. INTRODUCTION During installation process, a flexible pipe may be subjected to a high radial compressive force to hold the pipe suspended weight. Usually, a system of three or four shoes is employed for sustaining the flexible pipe during laying operation. If the radial load applied is too high, those shoes can crush the flexible pipe. In order to ensure the ongoing feasibility of the flexible pipe design for application with increasing water depth, it is important to improve the knowledge of the mechanism which can lead to a radial compressive failure of the pipe layers and enhance the ability to predict with greater assurance this particular failure mode. Once the water depth of offshore field becomes deeper, the flexible pipe resistance to installation loads becomes a critical design driver. The focus of this work is the prediction of radial compression failure due to pipe installation in deep water depth applications. For that purpose, a full 3D finite element model has been developed, including the interlocked carcass, the internal polymeric layer, the pressure armor, and the external polymeric layer. The model considers all the cross section profile details of the pressure armor and interlocked carcass, including self-contacts and contact between layers. It also considers the flexible pipe initial ovalization (as per definition from reference [1]) and the squeezing effect due to the tensile armor layers under traction. In order to avoid over-sizing the flexible pipe with the current project loads, the model took into account the elastic and plastic material properties. This model is able to accurately evaluate the stress distribution in carcass and pressure armor layers, used to establish the acceptable load limits during laying. It is also capable of predicting the flexible pipe behavior when stresses exceed material elastic limit of a layer, i.e., when yielding takes place. The results are presented and compared with experimental data. A discussion is made from this comparison and it is concluded that the presented model provides accurate results, leading to a more reliable design. NUMERICAL MODEL OVERVIEW The numerical model developed in order to predict the crushing of flexible pipes includes four layers: interlocked carcass, internal polymeric layer, pressure armor, and external polymeric layer. This model is intended to simulate the case of a laying system with four V-shape shoes and it was developed using the commercial finite element package Ansys ® . Figure 1 presents the model geometry. Some assumptions are considered on this model: • The interlocked carcass layer is considered to be compound by rings with the same cross section of the Proceedings of the ASME 2013 32nd International Conference on Ocean, Offshore and Arctic Engineering OMAE2013 June 9-14, 2013, Nantes, France OMAE2013-10909