Study On New Pipe-Laying Technique

Reel lay is a new pipe laying method which is developed since the end of 20 century. This kind of pipe laying method's efficiency is high and the pipe laying expense is low, and is widespread applicated in the developed country such as the USA. This article take reel lay as the main research object, mainly discuss the analytic and geometry aspects of the pipeline when it is under the applied force of pure bending moment, tension and bending moment, pression and bending moment and radial pressure during the process of reel lay in the premise of certain supposition and simplification, and the finite element method is also carried out to analyse the metioned stress models, to provid the theory basis and reference value for reel lay.The major contents of the article are summarized as follows:(1) Carries on the elastic-plasticity analysis when the pipeline is under pure bending moment, determines the pipeline's maximum elastic bending moment and plastic limit bending moment, and the section form factor according to the benging moments. Calculates the bending moments of different elastic-plasticity states according to consider the material's strengthening as well as dosen't considerate the material's strengthening to establish the pipeline's benging moment and curvature relationships under pure bending moment. Establishes the pipeline's finite element model under pure bending moment, carries on the finite element analysis under pure bending moment by considering the material's strengthening and as well as dosen't considerate the material's strengthening respectively. The analysis result indicated that the result of finite element analysis is consistent with the result of geometry analysis.(2) Carries on the elastic-plasticity analysis when the pipeline is under tension and bending moment. Calculates the relationships of zero dimension value n and zerodimension value m with zero dimension parameter γ and δ according to three kinds of stress distribution, the concrete value simulation graphs according to the computed result is also provided. The series of formulas are not only suitable for the pipeline, also are suitable for any annular section. It also provides the basis for calculating the zero dimension value n and zero dimension value m when the pipeline's stress distribution is known. Establishs the pipeline finite element model under the tension and bending moment, carries on the finite element analysis according to different combinations of n value and m value separately, and obtains the pipeline's zero dimension curvature along with the different n value and m value according to the finite element analysis results.(3) Carries on the elastic-plasticity analysis when the pipeline is under pression, calculates the limit value of elastic pressure and plastic pressure according to the elastic deformation stage and plastic deformation stage of the simplified model separately. Establishes the pipeline's finite element model when the pipeline is underpression, carries on the finite element analysis through different pressure. The limit value of elastic pressure of geometric computation and finite element computation is differed by about 7%, the pipeline will achieve the plastic limit condition when the pressure is 200kN.(4) Carries on the analysis when the pipeline is under the combination of axial tension and external radial pressure, determines the stress distribution along the pipeline section in elastic and plastic stages as well as pipeline's limit elastic and plastic radial pressure.