轴向承载力作用下非粘结柔性立管的侧向失效分析

Lateral Failure Analysis of Unbonded Flexible Risers Under Axial Compression Force

利用非线性有限元方法研究柔性立管在轴向承载力作用下的失效特性,采用实体单元模拟柔性立管抗拉铠装层、强结构带层和外部聚合物层,并考虑材料非线性、几何大变形、接触和摩擦等非线性效应的影响,通过数值模拟分析了柔性立管抗拉铠装层的螺旋钢带数、摩擦系数和外部聚合物层厚度等因素对非粘结柔性立管的失效模式和轴向承载能力的影响.结果表明:与采用部分螺旋钢带的简化模型相比,在抗拉铠装层采用全螺旋钢带数目的模型的失效过程更为复杂,其轴向承载力出现了多个峰值;摩擦系数对立管失效模式的影响很大,摩擦系数较小时立管为侧向失效,摩擦系数较大时立管为径向失效;外部聚合物层厚度对立管侧向失效时的最大轴向承载力影响有限.

Nonlinear finite element method is used to study the failure characters of flexible riser under axial compression force.The tensile armor layer,structural tape and outer sheath are modeled by solid elements. Material nonlinearity,geometrical large deformation,complex contact and friction are considered in this article.The effects of number of helix bands in armor layer,friction coefficient,thickness of outer sheath on the failure modes and axial compression force of flexible risers are studied.The results show that the failure process of all steel helix bands model is more complex than the simplified model which only contains partial helix bands.And the axial compression force exhibits a multiple peak phenomenon.Friction coefficient has a great influence on failure mode.It's a lateral failure when the friction coefficient is small,otherwise a radial failure when the friction coefficient is large.The thickness of the outer sheath has limited influence on the maximum axial compression force of lateral failure.