【作者】 祝娟；

【导师】 邹龙庆；

【作者基本信息】 大庆石油学院 ， 安全技术及工程， 2004， 硕士

【摘要】 在油田起下油(气)井管柱的各种施工中，作业井架是主要的承力构件，井架的承载性能对井下各种施工作业产生直接影响。目前对作业井架的力学行为分析大都是在线弹性范围内进行，采用有限元方法建立结构的计算机分析模型，得到结构在给定载荷作用下的位移、应力等参数，而对结构在弹塑性、塑性阶段的研究很少。作业井架在使用过程中，有时会出现短期超载现象，而且大多数井架已服役多年，结构自身存在着各种损伤缺陷，使得在用井架与理想状态下的井架在力学特性和承载能力上产生了差异。 本文应用双重非线性有限元方法研究井架结构的力学行为。结构分析采用ANSYS软件，建立作业井架的有限元分析模型。通过考虑结构几何非线性来研究结构的大初曲率、大变形对结构力学性能的影响；通过考虑材料非线性来研究结构在弹塑性阶段的力学性能。对线性、非线性两种分析方法所得的结果进行了对比分析。结果表明，在小荷载、小变形情况下，按线弹性理论对井架结构进行分析是可行的。 绷绳作为作业井架的特殊支承构件，其工作特性对作业井架的力学行为有较大影响。本文对井架绷绳的非线性效应进行了等效处理。在计算中采用等效弹性模量代替钢丝绳的有效弹性模量，来研究井架绷绳在载荷作用下由垂度变化所引起的非线性效应，分析了井架绷绳的非线性效应对结构受力变形产生的影响。结果表明，井架绷绳的非线性效应主要对结构的刚度产生影响。 本文研究了井架结构的极限承载力问题。对井架的失稳形式进行分析，确定井架结构的失稳形式属于极值点失稳，并通过双重非线性稳定性分析计算井架结构的极限承载力。对井架的整体初弯曲缺陷，采用与结构失稳时屈曲一致的初始缺陷波形进行模拟，对具有不同程度初始弯曲的井架进行了承载能力研究，得出了井架整体初弯曲程度与结构极限承载力之间的变化关系。更多还原

【Abstract】 In oilfield, downhole derricks are the main part that bears the loads in the downhole operation hoist system. Load capacity of the downhole derricks directly affects the downhole operation work At present, most mechanical behavior analysis for derricks are in the domain of elasticity, using finite element method to establish the computer analysis model, by analyzing get the stress, displacements and other mechanical parameters. The studies for derricks in the domain of plasticity are very few. The downhole derricks sometimes are over loading and most derricks are already worked for many years. They inevitably have varieties of damages and distortions, which made the derricks in-use have different mechanical characteristics as contrasted with their ideal status.This thesis presents a method of double nonlinear analysis to study the mechanical behavior of derricks steel structures. Large analytical software ANSYS was used. The large deformation of structures is considered by geometric nonlinearities analysis. The mechanical characteristics of derricks in the domain of plasticity are considered by material nonlinerities analysis. Contrasted with the results that come from linearity and nonlinearity analysis, it is concluded that to analyze derricks steel structures is feasible with linearity theory in the condition of light load and small deformation.Derrick guy wire as the special supporting member of downhole derricks, its performance has much impact on the mechanical behavior of derricks. Its nonlinear effect has been dealt with equivalently in this thesis. The equivalent elastic module has been used instead of derrick guy wire’s effective elastic module in the study of the nonlinear behavior that caused by derrick guy wire. The effect of derrick guy wires nonlinear behavior to structure’s deformation has been analyzed. According to the analysis, the nonlinear effects are mainly on the stiffness of downhole derricks steel structure.The ultimate load of the structure has been studied in this thesis and arrived by using nonlinear buckling analysis, which technique employs a nonlinear static analysis with gradually increasing loads to seek the load level at which the structure becomes unstable. The author presented a simulating method for bending deformation of derricks by using the mode, which is consistent with the buckling mode of derricks. The relation between the bending degrees and structural ultimate load capacity has been researched by using the simulation method.更多还原