A nonlinear viscoelastic bend stiffener steady-state formulation |
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| Institution: | 1. Continental, ContiTech Industrial Fluid System, Dunlop Oil and Marine Limited, Grimsby, DN31 2SY, United Kingdom;2. Engineering Department, Lancaster University, Lancaster LA1 4YW, United Kingdom;1. Dept. of Aerospace Engineering, Penn State University, University Park, PA 16802, USA;2. Dept. of Engineering Science and Mechanics, Penn State University, University Park, PA 16802, USA;1. Department of Mechanical Engineering, Kermanshah Branch, Islamic Azad University, Kermanshah, Iran;2. Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, USA;3. Integrated Modelling and Simulation Lab, Department of Mechanical Engineering, Indian Institute of Technology-Madras, Chennai, India |
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| Abstract: | Bend stiffeners are essential components of a flexible riser system, employed to ensure a smooth transition at the upper connection and to protect the riser against over bending and from accumulation of fatigue damage. The highly nonlinear rate dependent behavior of these structures directly affects the integrity assessment of the riser in one of its most critical regions, the top connection. A steady-state formulation (disregarding inertial forces) and numerical solution procedure is developed in this work employing the perturbation method for a nonlinear viscoelastic bend stiffener large deflection beam model subjected to harmonic loading conditions. For stochastic loading conditions, the response is calculated employing the superposition principle by summing up the steady-state result of a number of individual frequency components. A time domain formulation is also derived employing the state-variable approach for the numerical solution of the resulting hereditary integral in the governing equations. A case study is presented for the top connection system of a 4″ ID flexible riser using relaxation and tensile experimental data obtained from a typical class of bend stiffener polyurethane. Harmonic and stochastic input loading conditions are employed for time and frequency domain model comparison/validation and to assess loading history and frequency influence in the curvature response. |
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| Keywords: | Bend stiffener Nonlinear viscoelasticity Steady-state Frequency domain Time domain Flexible riser Top connection |
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