Abstract: Due to the viscoelasticity of polymer materials, flexible riser inner liner creep and prone to "embedded" into the carcass grooves, this phenomenon causes loss of structural integrity and carcass layer tear, etc., but in the existing analysis of theory and finite element model, the nature of the material are made a simple linear hypothesis, did not consider nonlinear viscoelastic properties of polymer materials. Based on the experimental test results of PA11, the time-hardening nonlinear constitutive model and the multi-integral nonlinear constitutive model considering the effect of time temperature are used to characterize the material properties respectively, and the fitting of the two models with the experimental data is compared. Based on the real structure of the inner liner and the carcass layer, a two-dimensional finite element numerical model is established, and the nonlinear creep behavior of the structure is analyzed and compared by using the two theoretical models. The nonlinear creep constitutive model can predict the strain and stress of the key parts of the structure more accurately in the unstable stage and under the condition of temperature gradient, which can provide reference and reference for the design and evaluation of the inner liner of flexible riser.

Key words: flexible riser, inner liner, polymer viscoelasticity, creep, finite element model