螺旋屈曲钻柱中诱发扭矩计算方法的研究

早期针对钻柱螺旋屈曲问题的研究一般忽略了由于螺旋屈曲诱发的扭矩,但随着水平井和大位移井的增多,这种诱发扭矩越来越明显,严重影响钻柱的安全性评估。文中建立了螺旋屈曲管柱诱发扭矩的计算模型,并对扭矩计算方法展开了研究。     

变曲率井中有重钻柱屈曲的非线性有限元分析

基于等曲率井中有重钻柱屈曲的平衡方程及对应的泛函表达式,建立了采用有限元法对变曲率井中有重钻柱屈曲过程进行分析的方法,给出了求解变曲率井中钻柱屈曲非线性方程的算法。力学模型中考虑了钻柱重力、井眼轨迹曲率半径变化率对屈曲的影响。分析结果表明:钻柱上端轴向载荷增大时,钻柱的下端先出现局部屈曲,随后屈曲向钻柱上部扩展,导致钻柱发生整体屈曲;屈曲位移、井壁约束力线密度和钻柱弯矩都呈周期性变化;井眼的弯曲对钻柱屈曲具有抑制作用,井眼轨迹曲率半径变化率越大,钻柱的屈曲也越严重。     

垂直井与水平井钻柱屈曲数学模型优化

对钻柱在井眼内的受力情况进行了分析,得到钻柱在井下的几种屈曲形式。同时对国内外利用能量法推导的垂直井与水平井钻柱屈曲数学模型进行分析对比,分别考虑井眼中在内外流体压力作用下钻柱单位长度重量及钻柱与井壁的摩擦系数,推导出更适用于现场垂直井和水平井钻柱临界屈曲载荷的正弦屈曲临界载荷与螺旋屈曲临界载荷的新数学模型。通过屈曲载荷新数学模型的建立,为现场预测钻柱稳定性提供了可靠的理论依据。     

斜直井中钻柱非线性屈曲分析的有限元增量加权迭代法

建立了直井中有重钻柱非线性屈曲平衡方程及相应的泛函表达式，构造了一种能避免发散并加速收敛的有限元增量加权迭代法求解斜直井中钻柱屈曲问题，首次采用直接求解非线性特征值的方法来分析钻柱屈曲问题。计算结果表明，井斜角和屈曲位移幅值中任意一项增大，钻柱的非线性屈曲临界载荷也随之增大，且呈非线性；重力线密度对屈曲载荷的影响与屈曲状态有关；井壁约束力和特征向量的幅值随屈曲位移幅值增大而增大；扭矩对屈曲的影响很小，可以略去。研究结果为实际钻井作业中屈曲载荷的确定提供了参考。     

斜直井中考虑摩擦时钻柱的正弦屈曲分析

提出了在斜直井中钻柱正弦屈曲分析时对摩擦阻力的处理方法,给出了考虑摩擦阻力时的屈曲平衡方程,建立了相应的微分求积法列式,用微分求积法对平衡方程直接求解.在力学模型中考虑了摩擦因数、重力线密度、钻柱长度和井斜角对临界载荷的影响,并将数值计算结果与实验数据进行了比较.分析表明,提出的在钻柱正弦屈曲分析时对摩擦阻力的处理方法是正确有效的,能够为实验结果提供理论分析基础;在同等条件下,钻柱正弦屈曲临界载荷随摩擦因数的增加而增大;钻柱越长,摩擦阻力对临界载荷的影响越大,在一定程度上,摩擦可以增加钻柱的稳定性.     

斜直井中考虑摩擦时钻柱的正弦屈曲分析

提出了在斜直井中钻柱正弦屈曲分析时对摩擦阻力的处理方法,给出了考虑摩擦阻力时的屈曲平衡方程,建立了相应的微分求积法列式,用微分求积法时平衡方程直接求解。在力学模型中考虑了摩擦因数、重力线密度、钻柱长度和井斜角对临界载荷的影响,并将数值计算结果与实验数据进行了比较。分析表明,提出的在钻柱正弦屈曲分析时对摩擦阻力的处理方法是正确有效的,能够为实验结果提供理论分析基础;在同等条件下,钻柱正弦屈曲临界载荷随摩擦因数的增加而增大;钻柱越长,摩擦阻力对临界载荷的影响越大,在一定程度上,摩擦可以增加钻柱的稳定性。     

钻柱疲劳寿命计算方法研究

钻柱在井下的受力极度复杂，甚至工作在腐蚀性介质中。通过对钻柱疲劳破坏机理的分析，建立合理的钻柱受力模型，同时编写适合于工程应用的钻柱寿命计算程序，研究影响钻柱疲劳破坏的主要因素，为井下钻柱的使用，尤其是在定向井和水平井钻进过程中避免或减少发生钻柱复杂情况和井下事故，提供了可靠的保证。     

钻井液作用下水平井钻柱横向振动建模与分析

根据哈密顿原理,并考虑到钻井液和钻柱的耦合作用,建立了水平钻柱横向振动的数学模型,分析了内外钻井液流速、钻井液密度、钻井液粘度系数、重力、摩阻、钻压等对钻柱横向振动特性的影响规律,并基于自主研制的水平井钻柱动力学试验装置,开展了不同钻压、钻井液流速条件下的钻柱横向振动特性模拟试验研究。研究结果表明:钻压的增加、钻井液的存在及其流速的提升都会导致钻柱的横向振动频率减小以及振动幅值上升。     

水平井钻柱涡动特性数值分析与试验

根据转子动力学和流体力学理论,建立了水平井钻柱涡动的动力学方程,分析了钻柱自重、井壁摩阻、钻井液流速等因素对水平井钻柱涡动的影响规律,阐释了诱发水平钻柱涡动产生的机理及边界条件。基于自主研制的水平井钻柱动力学试验装置,采用数值模拟和试验研究相结合的方法,分析了钻压、转速、流体速度等参数对钻柱涡动轨迹和涡动速度的影响规律。研究结果表明：在钻柱的远钻头段不会发生涡动,但是转速达到阈值后,近钻头段便会出现涡动现象,并且随着钻压和转速的增加,其涡动轨迹幅值也在增大;而近钻头段的涡动方向并不是始终如一的,存在正反两个方向的涡动,并且随着转速的增大,还会出现“半频涡动”现象;另外,钻井液的存在及其流动速度的增大都不会改变钻柱现有的运动状态,仅小幅增加其运动范围。研究成果对水平井钻井工艺参数的选定有一定的借鉴作用。     

某柴油机EGR安装平台结构失稳分析

应用三维建模软件对某安装平台进行三维建模,采用有限元软件对平台进行线性屈曲分析。在考虑重力的工作情况下,施加载荷及约束,分析结构的屈曲性能,根据屈曲分析结果,找出易失稳的部位与失稳先后顺序,并研究了约束方式和型材尺寸对平台稳定性的影响规律,为平台的合理化设计提供了很好的参考。     

Static, dynamic, and buckling analysis of partial interaction composite members using Timoshenko's beam theory

The static, dynamic, and buckling behavior of partial interaction composite members is investigated in this paper by taking into account for the influences of rotary inertia and shear deformations. The governing differential equations obtained are very comprehensive, covering and extending the current models for the problems that are based on Euler–Bernoulli beam theory. The analytical solutions of the deflection are then found for the beam with uniformly distributing load under common boundary conditions. The free vibration and buckling behavior are also studied and the analytical expressions of the frequencies of the simply supported beam are obtained explicitly, as are the buckling loads. For other boundary conditions, the eigen-equations are transcendental and thus some numerical examples are presented to demonstrate the effects of the shear deformation and rotary inertia on the resonant frequencies and buckling loads.     

Nonlocal beam models for buckling of nanobeams using state-space method regarding different boundary conditions

Buckling analysis of nanobeams is investigated using nonlocal continuum beam models of the different classical beam theories namely as Euler-Bernoulli beam theory (EBT), Timoshenko beam theory (TBT), and Levinson beam theory (LBT). To this end, Eringen’s equations of nonlocal elasticity are incorporated into the classical beam theories for buckling of nanobeams with rectangular cross-section. In contrast to the classical theories, the nonlocal elastic beam models developed here have the capability to predict critical buckling loads that allowing for the inclusion of size effects. The values of critical buckling loads corresponding to four commonly used boundary conditions are obtained using state-space method. The results are presented for different geometric parameters, boundary conditions, and values of nonlocal parameter to show the effects of each of them in detail. Then the results are fitted with those of molecular dynamics simulations through a nonlinear least square fitting procedure to find the appropriate values of nonlocal parameter for the buckling analysis of nanobeams relevant to each type of nonlocal beam model and boundary conditions.analysis.     

Generalized buckling analysis of laminated plates with random material properties using stochastic finite elements

A generalized layer-wise stochastic finite element formulation is developed for the buckling analysis of both homogeneous and laminated plates with random material properties. The pre-buckled stresses are considered in the derivation of geometric stiffness matrix and the effect of variation in these stresses on the mean and coefficient of variation of buckling strength is studied. The mean buckling strength of plates under uniform stress assumption exactly matches with those reported in the literature. However, it is shown that the actual mean buckling strength of plates can be significantly different based on the pre-buckled stress analysis which depends on boundary constraints, principal material directions, aspect and thickness ratios of plates. The statistics of buckling strength is determined using a Taylor series expansion based mean centered first order perturbation technique. The stochastic finite element solutions obtained using layer-wise plate theory is also validated with analytical solutions presented in this paper. Parametric studies are conducted for different aspect ratios, ply orientations and boundary conditions.     

Buckling of composite beams with two non-overlapping delaminations: Lower and upper bounds

In this paper, lower and upper bounds of the buckling load of a composite beam with two non-overlapping delaminations are obtained by developing analytical models. The characteristic equation governing the delamination buckling is derived by using Euler-Bernoulli beam theory, performing proper linearization and by imposing the appropriate continuity and boundary conditions. The effects of the differential stretching and the bending-extension coupling are considered. The accuracy of the approach is verified by comparing results with previously published data and a separately carried out finite element analysis. The effects of the dimensions of the delaminations, their thicknesswise and spanwise locations on the lower and upper bounds of the buckling load are investigated in detail. The longer of the two non-overlapping delaminations dominates the buckling behavior. Composite beams with anti-symmetric non-overlapping delaminations withstand lower buckling loads than the composite beams with symmetric non-overlapping delaminations. The lower and upper bounds of the buckling load will be useful to gauge the working range of bridging and give guidelines for practical applications.     

纤维增强FGM梁的自由振动和临界屈曲载荷分析

基于经典梁理论（CBT）研究轴向力作用下纤维增强功能梯度材料（FGM）梁的横向自由振动和临界屈曲载荷问题。首先考虑由混合律模型来表征纤维增强FGM梁的材料属性,其次利用Hamilton原理推导轴向力作用下纤维增强FGM梁横向自由振动和临界屈曲载荷的控制微分方程,并应用微分变换法（DTM）对控制微分方程及边界条件进行变换,计算了纤维增强FGM梁在固定-固定（C-C）、固定-简支（C-S）和简支-简支（S-S）3种边界条件下横向自由振动的无量纲固有频率和无量纲临界屈曲载荷。退化为各向同性梁和FGM梁,并与已有文献结果进行对比,验证了本文方法的有效性。最后讨论在不同边界条件下纤维增强FGM梁的刚度比、纤维体积分数和无量纲压载荷对无量纲固有频率的影响以及各参数对无量纲临界屈曲载荷的影响。     

油(套)管标准与我国压力容器用管材标准规范比对研究

对油(套)管标准和我国压力容器用管材标准规范进行了比对分析,掌握了油(套)管标准与我国压力容器用管材标准规范对材料的制造方法、化学成分、力学性能等方面的要求之间存在的差异,可以为储气井专用钢管材料国家标准的制定以及为企业研制储气井专用钢管提供参考。     

Finite-element simulation of the lateral compression of aluminium tube between rigid plates

The lateral compression of aluminium and clad tubes owing to a large deformation is examined by an incremental elasto-plastic finite-element method based on an updated Lagrangian formulation in which a sliding-sticking friction mode is specially considered. It is mainly expected to predict the buckling process and load–deflection curves for energy dissipation capacity during the design stage, before trials. The high non-linearity of the process due to geometric changes, the inelastic constitutive behavior, and the deformation-dependent boundary conditions are taken into account in an incremental manner. A static explicit approach to the solution is applied, tangent stiffness matrix equation is solved without iteration and the r_min technique is employed to limit the step size to linear relation. The simulated load–deflection curve agrees with a published experimental result. The predicted geometries of the compressed tube clearly demonstrate the processes of the formation of buckling until unloading. The effects of various parameters of the process, such as elastic modulus, strain hardening exponent, tube thickness, friction coefficient and configurations of the clad tube, on the occurrence of buckling of tube are discussed and interpreted in simulation. The present work may be expected to improve the understanding of the buckling mechanism of lateral compression.