Advanced Cyclical Numerical Material Model Supports Pipeline Reel-Lay
- Shulong Liu (SAIPEM S.A. Montigny Le Bretonneux) | Eric Giry (SAIPEM S.A. Montigny Le Bretonneux) | Vincent Cocault-Duverger (SAIPEM S.A. Montigny Le Bretonneux)
- Document ID
- International Society of Offshore and Polar Engineers
- The 30th International Ocean and Polar Engineering Conference, 11-16 October, Virtual
- Publication Date
- Document Type
- Conference Paper
- 2020. International Society of Offshore and Polar Engineers
- cyclic loading, Abaqus user subroutine, Abaqus user subroutine, FE simulation, tests, material model, reel-lay, tests, reel-lay, rigid pipeline, FE simulation, cyclic loading, rigid pipeline, material model
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- 2 since 2007
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Reel-laying rigid pipelines induce cyclic deformation that affect the section. Among other, excessive ovality may jeopardize pipe strength during installation & in-service. Previous works shown that conventional material stress-strain relation is no longer suitable for pipeline reel-lay simulations. This paper introduces an advanced model for material behaviour. The evolution of the material behavior and its variations on the cyclic loads paths is detailed. The model uses stressstrain relations and yield surface evolution from the first load curve, with Lüders plateau leading to stabilized cycle with material property variations in cycles. The model has been implemented in finite element software. This model calibration and validation are discussed in this paper. Simulation accuracy is improved compared to published results.INTRODUCTION
The pipeline reeling installation process can be a cost-effective installation method for infield flowlines/risers and smaller diameter export lines under certain economical, logistical and technical circumstances. Saipem has acquired a recent pipeline construction vessel, Constellation, which has been designed as a high-performance construction and lay vessel, capable of performing in the world's hardest environments and designed to meet the requirements of current deep and ultra-deep-water projects.
During offshore reeling installation, and possibly later pipeline recovery and re-reeling installation, the pipe is reeled, unreeled and straightened. During the process, part of the pipe cross-section has experienced varying levels of plastic deformation in compression and tension, in a cyclic manner. Throughout these steps, the plasticity deformation has modified the pipe material properties, while the other part remains in the elastic domain.
Materials under cyclic loading can harden both kinematically and isotropically (or anisotropically). For applications where cyclic loads stay within a single cycle, hardening process comes mainly from kinematic hardening while yield domain surface evolution is negligible. Within a single cycle, Bauschinger effect drive the model behavior, while variation of this behavior through cycles comes from isotropic hardening. The Bauschinger effect refers to a property of materials where the material's stress/strain characteristics change as a result of the microscopic stress distribution of the material. An increase in tensile yield strength occurs at the expense of compressive yield strength. After increasing the tensile yield strength, the local initial compressive yield strength is actually reduced. The greater the tensile strengthening, the lower the compressive yield strength.
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