Theoretical model for variable helical angle of tensile armour wires in bent flexible pipes

摘要

This paper systematically addresses a theoretical model to account for the variation of the initial helical lay angle of the tensile armour wires in flexible pipes during bending condition. Based on differential geometrical discussion and curved beam theory, a nonlinear differential equation system which contains the unknown variable helical angle is established. Moreover, different expressions of wires' strain before and after wires' slip are included in the paper to underline the discrepancy between scenarios in non-slippage and slippage regions. The variation of the armour wires helical angles, which are usually implicit in previous work, can be obtained numerically, revealing potential application in global bending problem. Case studies compared with results obtained through analytical and numerical models available in the literature as well as parametric analyses corresponding to original helical angle, initial tensile force, friction coefficient and bending curvature are performed to verify the feasibility of the proposed theoretical method.