With the continuous development of offshore oil and gas resources,the application of un-bonded flexible risers has become more widespread.When the vessel hoisting flexible riser on the surface of the water experience irregular movement,the flexible riser attached to the lower part of the vessel will undergo a changing axial load.The innermost structure of the un-bonded flexible riser-carcass layer would cause friction between the contacts under external loads owing to its special geometry.To understand the stress and strain of the carcass layer and the friction loss under different changing axial loads,the mechanical calculation model of carcass layer is established based on the helical strip structure,and is solved using ABAQUS finite element software with changing axial loads on the carcass layer.When the friction coefficient is within the range of 0.15 to 0.20,the friction work is the largest.When the friction factor is larger than 0.25,the friction work is gradually reduced with the increase of the friction factor.When 5 MPa external pressure is applied to the carcass layer,the change of external pressure does not have much influence on the friction work.The friction loss factor increases with the increase of friction factor.When the friction factor is larger than 0.20,the change of friction factor has little effect on the change of friction loss factor.The study results could provide bases for the failure judging and strength calculation of the carcass layer end.%随着海洋油气资源不断开发,非黏结柔性立管的应用也越来越广泛.当水面上吊装柔性立管的船舶发生不规则运动时,连接在船舶下部的柔性立管会承受变化的轴向载荷.骨架层作为非黏结柔性立管最内层结构,由于其几何形状的特殊性,在外载荷作用下相邻表面会出现接触从而引起摩擦.鉴于此,针对骨架层螺旋带结构建立相应的骨架层力学计算模型,对骨架层施加变化的轴向力,借助ABAQUS有限元软件分析骨架层在变化轴向力作用下应力应变和不同情况下的摩擦损失.当摩擦因数在0.15～0.20区间内时,摩擦力做功最大;当摩擦因数大于0.25时,摩擦力做功随着摩擦因数的增加逐渐减小;对骨架层施加径向外压在5 MPa以内时,其外部压力变化对摩擦力做功没有太大影响;摩擦损失因子随着摩擦因数增大而逐渐增大,当摩擦因数大于0.20时,摩擦因数的变化对摩擦损失因子改变影响较小.研究结果可为骨架层端部失效及工程设计制造时的强度计算提供依据.
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