Study on the Mechanical Characteristics of Unbonded Flexible Pipes Under Axisymmetric Cyclic Loads

To investigate the mechanical behavior of unbonded flexible pipes under axisymmetric cyclic loading, this study accounts for nonlinear effects including large structural deformations, interlayer contact between multiple layers, and interlayer friction. A complete structural model of an eight-layer unbonded flexible pipe was established using the ABAQUS finite element analysis software. The structural deformation characteristics of the flexible pipe under two types of axisymmetric cyclic loading, axial tension-compression cyclic loading and bidirectional torsional cyclic loading, were studied along with the influence of interlayer friction coefficient on the pipe's mechanical properties under these two loading conditions. The results indicate that the load-deformation curves of the flexible pipe under axisymmetric cyclic loading exhibit hysteretic characteristics. Both the deformation characteristics of the tensile armor layer steel strips and the interlayer friction coefficient have a significant impact on the hysteretic behavior of the axisymmetric cyclic load-deformation curves.