【作者】 李明；

【导师】 李映辉；

【作者基本信息】 西南交通大学 ， 力学， 2020， 博士

【摘要】 埋地输油管在工程领域尤其是油气工业、石油运输中扮演着十分重要的角色。本文采用(半)解析的方法系统地研究了长距离埋地输油管的振动特性与响应,重点讨论了环境参数、流速、裂纹参数、结构参数等对输流管固有频率和临界流速的影响。以EulerBernoulli梁理论为基础,首先通过Hamilton原理建立了Pasternak地基上输油管的振动控制方程,然后建立了Winkler地基上含多种因素的输流管的物理模型,接着建立了Pasternak地基上含有多个不连续点的长距离输油管的控制方程。通过与文献中已有的模型相对比,验证了本文模型的正确性与适用性。研究了Pasternak地基上单跨输流管道的受迫振动,采用Green函数得到了其在广义边界下的解析解,分析了其动态响应和稳定性特征,并讨论了边界弹簧刚度、地基刚度、流速、厚径比和长径比等参数对固有频率和临界流速的影响。结果表明:在不同的边界弹簧刚度下,前三阶固有频率随流速的增加先减小后发生复杂的变化;不同的边界弹簧的形式对临界流速有不同的影响;两个地基参数对固有频率和临界流速的影响程度不同;长径比的增加会降低固有频率与临界流速,而厚径比的增加则会提升临界流速。分析了Winkler地基上含有附属结构的非等截面的多跨输油管的振动特性。在传统传递矩阵法的基础上,针对弹性地基与非零的流速这两个难点,提出了一种能够处理这两个问题的改进的传递矩阵法。该方法能够对各种边界均采用同一个频率方程,并据此讨论了多种参数对结构振型的影响。结果如下:多种因素同时作用在管道上时,振型的最大幅值更易出现在管道的悬跨段,附加的集中质量对高阶振型有明显的影响,而转动惯量有时会对振型产生明显的影响;一般情况下,振型随流速的增加不发生很明显的变化,但在某种情况下,Winkler地基刚度的改变也会引起振型随着流速的增加而出现显著的变化。采用Laplace变换,结合连续性条件和广义边界条件,推导出了位于Pasternak地基上含有多个不连续点与任意不连续性的输流管道的振动问题的一般解析解,并讨论了裂纹参数、支撑弹簧刚度、流速、地基参数和结构参数对双跨双裂纹弹性支撑管的固有频率的影响。计算结果表明:裂纹位置对固有频率的影响是对称的,裂纹越靠近某阶振型的最近节点,对相应阶次的固有频率的影响越小;裂纹深度对不同阶固有频率有不同程度的影响;支撑弹簧的位置通过影响结构节点的位置来改变裂纹对固有频率的影响;横向支撑刚度与旋转支撑刚度对裂纹的影响不同;前两阶频率衰减随Winkler地基参数的增加而增加,而随剪切层参数的增加而减小;前三阶频率衰减随着厚径比的增加而急剧下降,尤其是第二阶。最后,对本文的研究内容、研究成果进行总结,并对未来的工作做了展望。更多还原

【Abstract】 Buried oil-conveying pipeline plays a very important role in engineering,like oil and gas industry and oil transportation.In this dissertation,the vibration characteristics and responses of long-distance buried oil-conveying pipelines are systematically studied via(semi)analytical methods,with the effects of environmental parameters,flow velocity,crack and structural parameters being discussed.Up to three kinds of different pipelines are studied,pipelines on the Pasternak foundation,pipelines on the Winkler foundation and with combined factors,and long-distance pipelines with multiple discontinuous points on the Pasternak foundation.For the forced vibration of a single span fluid-conveying pipeline on the Pasternak foundation,the analytical solution under generalized boundary is obtained by using Green’s function,then the dynamic responses and stability characteristics are analyzed.Parametric results show that: under different stiffness of boundary spring,the first three natural frequencies firstly decrease and then change complicated with the increase of the flow velocity;different forms of boundary spring have different effects on the critical velocity;two foundation parameters have different effects on the natural frequency and critical velocity;the increase of length-to-diameter ratio will reduce the natural frequency and critical velocity,while the increase of thickness-to-diameter ratio will improve the critical velocity.Then,the vibration characteristics of a multi-span fluid-conveying pipeline with nonuniform cross-section on the Winkler foundation are studied.Based on the traditional Transfer Matrix Method,a modified Transfer Matrix Method is proposed to deal with the two difficulties of elastic foundation and non-zero flow velocity of the system.The proposed method enables us to use a uniform frequency equation for all kinds of boundary conditions.Parametric results are as follows: when many factors act on the pipeline at the same time,the maximum amplitude of the mode shapes is more likely to appear in the suspension-span section of the pipeline;the additional concentrated mass has obvious effect on the higher mode shape,and the moment of inertia sometimes has obvious effect on the mode shapes;generally,the mode shape does not change significantly with the increase of flow velocity,but in some cases,the change of the stiffness of the Winkler foundation also causes mode shapes to change significantly with the increase of flow velocity.Based on Laplace transform,continuity condition and generalized boundary condition,a general analytical solution of the vibrations of pipelines with multiple discontinuity points and arbitrary discontinuities on the Pasternak foundation is derived.The effects of crack parameters,support spring stiffness,flow velocity,foundation parameters and structural parameters on the natural frequency of a double-span and double-crack elastic-support pipe are discussed,and the results show that: the effect of crack location on the natural frequency is symmetrical,the closer the crack is to the nearest node of a certain mode shape,the less effect on the natural frequency of corresponding order;the depth of crack has different effects on the different order natural frequencies;the position of support spring changes the effect of crack on the natural frequency by affecting positions of structural nodes;transverse and rotational support spring stiffness have different effects on cracks;the first two natural frequency reductions increase with the increase of the Winkler foundation parameter and decreases with the increase of shear layer parameter;the first three natural frequency reductions decrease sharply with the increase of thickness-to-diameter ratio,especially the second order.Finally,the current work of this dissertation is summarized,and the future work is discussed.更多还原