Behavior of Reinforced Thermoplastic Pipe (RTP) under Tension

Abstract

Recently, Reinforced Thermoplastic Pipe (RTP) is increasingly applied in the oil and gas industry. Since tensile behavior is a fundamental property of RTP, both theoretical method and numerical simulation are used within this paper to study the behavior of RTP under tension. In theoretical method, the model proposed by Knapp is modified and further applied to RTP, considering the interaction between pipe and wires as well as material nonlinearity. Equilibrium equations are derived based on the principle of stationary potential energy. Using Newton-Raphson method, the problem is solved by an iterative procedure. As for the finite element model, solid and truss elements are used to simulate the HDPE layer and wire respectively. Results from both methods are compared and an agreement between the theoretical method and numerical simulation is obtained. Both methods can offer valuable advice for RTP design and application.

Failure behavior analysis of steel strip–reinforced flexible pipe under combined tension and internal pressure

“…Equation 5reveals the relation between pipe axial strain and reinforcement layer axial strain along the winding direction. Define E steel as the elastic modulus of steel and combining equations (1) and (5), one can obtain:…”

“…Bai et al developed a new model to study the mechanical behavior of RTP under tension load, and this model can take into account the interaction between high-density polyethylene (HDPE) and Kevlar wires as well as the material nonlinearity, and based on the principle of stationary potential energy, the equilibrium equations are set up and further solved with Newton-Raphson method. 5 Svein Savik presented a formulation for predicting the dynamic stresses of tensile armor in un-bonded flexible pipe under bending load, two ways are proposed in this article to treat the shear interaction between layers, and finally experimental studies applying fiber-optic Braggs are presented to validate the performance of the formulations. 6 Based on the numerical 2-D ring model, Bai et al analyzed the mechanical behavior of steel wire-reinforced plastic pipe (PSP) under external hydrostatic pressure by taking into account the wall thickness change, transverse shear deformation, and prebuckling deformation.…”