Calculation method of radial compression capacity of carcass layer of unbonded flexible pipes

Carcass layer is known as the anti-radial pressure layer of unbonded flexible pipe, whose performance determines the installation performance and operation depth of flexible pipe. However, due to the complex structure of carcass layer, it is difficult to accurately calculate its compressive properties using traditional methods. Therefore, this paper proposes the cross section equivalence method of carcass layer, and the compression performance of carcass layer is analyzed by experimental, three-dimensional and two-dimensional finite element methods, as well as theoretical method. The calculation results show that:(1) in the analysis of radial compression stiffness, the error between the the result from the three-dimensional finite element method and the experimental result is 8.29%, and that between the results from the cross section equivalence method and the experimental result is 1.86%; (2) when analyzing the critical collapse load of uniform compression, it can be only obtained by using the finite element method and taking into account the plasticity parameters of carcass layer, and the error between the results of the three-dimensional finite element method and the two-dimensional finite element method of cross section equivalence and the experimental result is 1.18% and 0.88%, respectively. The results show that the compression model and cross section equivalence method of carcass layer are applicable and can provide simple and reliable methods for the design and performance evaluation of carcass layer.