非均匀载荷下磨损套管抗挤强度研究

针对非均匀载荷下套管磨损后抗挤强度降低的问题,将磨损简化为套管的壁厚不均度和内壁不圆度几何缺陷。在此基础上,建立了非均匀载荷下磨损套管抗挤强度计算方程。该方程计算值与试验值的对比表明,该方程计算结果是可靠的,可为复杂地层磨损套管柱设计提供理论依据。研究表明,当载荷不均匀程度较小时,磨损对套管抗挤强度的影响较大;当载荷不均匀程度较大时,磨损对套管抗挤强度的影响较小。     

非均匀挤毁测试研究C110套管的变形规律

为完善套管非均匀挤毁失效机理的理论研究,开展了C110套管的非均匀挤毁实验,通过精密的压力试验机给套管施加非均匀载荷,进而得到套管不同载荷下的径向位移。采用在套管外壁粘贴电阻应变片的方式来测量套管在挤毁过程中的应变,进而得到了套管的屈服载荷、失稳载荷以及套管在非均匀载荷下的变形规律和失效机理。     

石油套管偏磨后剩余强度的模拟分析

基于钻柱接头与套管磨损试验结果,采用Dawson和White的能量损失磨损理论计算得到套管磨损系数。运用ABAQUS建立钻柱接头-套管偏磨的三维有限元模型,采用二次开发的Umeshmotion子程序和Arbitrary Lagrange-Euler自适应网格技术准确模拟钻进过程中的套管局部偏磨过程,并对磨损后的套管的剩余抗挤和抗内压强度进行分析。结果表明：套管磨损后的形状为“月牙形”,且磨损最大深度与磨损时间呈非线性关系,而套管剩余强度与磨损最大深度近似呈线性关系;套管磨损对剩余抗挤强度影响最大,当剩余壁厚小于50%时,套管失去抵抗外挤作用的能力, 但仍然具有一定的抗内压强度;发生偏磨后的套管被外挤和内压载荷作用而破坏的形式分别为挤扁毁坏和拉断毁坏。     

现场工况条件下含点蚀缺陷套管抗外挤强度分析

套管一旦发生点蚀，其表面可能出现孔洞，甚至穿孔现象，这严重削弱了套管的剩余强度，对井场的生产和安全构成了重大威胁。为了评估点蚀后套管的抗外挤强度，提出了一种模拟现场工况对套管抗外挤强度进行分析的方法。首先模拟现场工况下压力和温度条件，严格配比井下腐蚀液体作为介质对套管全尺寸试样和挂片样件进行腐蚀；然后对腐蚀后套管进行抗外挤试验，测量出其被挤毁时的失效压力；接着观察腐蚀后挂片的表面点蚀规律，并计算和测出其平均腐蚀速率、最大点蚀深度和点蚀密度，为有限元分析提供数据支撑；最后使用ABAQUS对不同条件下套管的抗外挤强度进行分析。结果表明：在一定温度和压力范围内，温度和压力越高，套管失效压力越高；平均腐蚀速率、最大点蚀深度和点蚀密度随温度和压力升高而增大，其中平均腐蚀速率增长率为112.5%，增长最为显著；套管的抗外挤强度随腐蚀时间增长而降低；点蚀密度会影响套管的应力分布情况和承载能力。     

非均匀磨损套管空间有限元分析

针对非均匀磨损套管进行了空间有限元分析,研究了磨损量、磨损长度、轴向拉力对套管抗内压强度的影响.计算结果表明非均匀磨损套管的抗内压强度随磨损厚度的增加而降低;不同的磨损长度对套管抗内压强度影响不明显,即抗内压强度主要受磨损厚度的影响;套管轴向拉力对其抗内压强度影响不大,并且这种影响随着磨损量的增加而逐渐减小.通过对磨损套管抗内压强度变化规律的研究,为合理制定井控措施提供了科学依据.     

内压对射孔套管强度影响的有限元分析

射孔对套管抗挤强度的影响程度取决于多种因素.主要研究内压对射孔套管强度的影响.建立未射孔套管、不带水泥环射孔套管、外裹水泥环射孔套管有限元模型,并应用ANSYS有限元软件分析计算了未射孔、射孔及孔边开裂三种情况下套管的最大应力,同时研究了水泥环对射孔套管强度的影响.结果表明:射孔套管最大应力比未射孔套管增大了64%,孔...     

月牙形磨损缺陷套管的抗内压强度研究

套管磨损多呈"月牙形",其直接后果是降低套管的抗挤强度和抗内压强度,如何计算磨损套管的抗挤强度、抗内压强度制约着如何安全地设计套管柱。因此笔者对"月牙形磨损"套管在不同磨损程度时的周向应力进行研究,并重点对其抗内压强度的计算方法进行了探索。笔者以P110的95/8 in套管为例,建立了计算磨损套管周向应力的解析模型,并用弹塑性有限元方法建立了套管的有限元力学模型,通过有限元分析来验证解析模型的正确性,最后以此为基础得出了磨损套管的抗内压强度计算公式。     

CO_2腐蚀对套管强度动态影响分析

针对腐蚀对套管强度时变性影响,采用双重迭代试算法结合压力温度耦合作用,计算井筒内压力、温度沿井深方向分布情况,依据Norsok模型得到全井套管柱CO2腐蚀速率计算预测模型。依据试井理论利用现场录测井口压力数据回归得到气井稳产阶段井口压力随时间变化函数关系,将定产降压阶段内的压力温度时变规律引入腐蚀速率预测模型,建立CO2腐蚀环境下全井套管柱剩余强度时变性分析系统,通过对均匀腐蚀套管强度实例计算结果表明:腐蚀引起的壁厚减薄使得套管柱剩余强度随时间增加逐年降低,稳产阶段初期下降最快,随时间增加下降趋势逐渐减缓,其沿井深分布规律与腐蚀速率变化规律相似;套管极限抗挤毁强度受均匀腐蚀影响显著,其降低程度高于套管极限抗内压强度和管体抗拉强度。     

不同缺陷对套管剩余强度影响分析

借助有限元软件ANSYS对套管在均匀、点状和裂缝腐蚀缺陷下的剩余强度进行了计算。结果表明:均匀腐蚀下套管剩余强度随壁厚减薄而近似线性降低;点状腐蚀套管剩余强度变化为降低—平稳—降低;裂缝腐蚀下套管内压和外压剩余强度变化与点状腐蚀趋势近似,而拉伸曲线只在开始时急剧下降,随后一直保持平稳;腐蚀后套管承载能力由大到小排序为:点状腐蚀、均匀腐蚀、缝隙腐蚀。     

油井压力套管强度有限元仿真分析

在某油田提供的60臂测径仪所测的7in套管腐蚀缺陷检测结果及工程测井解释报告的基础之上,用MSC／ARIES、MSC／NASTRAN有限元分析软件,对其剩余抗爆破和剩余抗挤毁能力进行了分析计算。结果表明：当腐蚀程度不严重时,并不影响其使用性;而当腐蚀达到一定程度时,其剩余强度明显降低。     

基于NURBS的水力机械叶片表面造型研究

论述了在已知叶片轴面截线图的情况下,采用B样条插值理论,求出叶片表面控制点,然后利用非均匀有理B样条方法实现叶片表面的数值化。同时可采用交互方式对叶片表面控制点或其权因子进行修改,构造出逼真的叶片,增强了叶片计算机辅助设计系统的交互设计能力;对改进叶片的设计方法和提高其设计质量具有重要意义。     

等效节点载荷解析解在结构受力分析中的应用

针对非均布载荷作用结构的受力分析问题,从有限元基本原理出发,选取三角形单元对加载边进行等间距网格离散,推导加载边上端点和中间节点处等效节点载荷的解析解,其包含加载边端点坐标、网格数、外加载荷及外加载荷与加载边的夹角。以单向均布轴压作用下斜板的屈曲分析、非均布载荷作用下悬臂矩形板弯曲的弹性力学解为例,在加载边节点上施加解析解对应等效节点载荷。通过对比其他数值解表明,解析解可精确、简便地求解非均布载荷作用结构的受力问题。     

A quick deviation zone fitting in coordinate metrology of NURBS surfaces using principle component analysis

Evaluation of the tolerance zone using discrete measured points plays a critical role in today’s manufacturing, metrology, and many industrial applications. The deviation zone is typically evaluated using a fitting method that locates an ideal desired geometry corresponding to a set of measured points while a function of the Euclidean distances of the measured points to the ideal surface becomes minimum. This paper presents a quick and reliable algorithm called Dynamic Principle Component Alignment (DPCA) for fitting complex surfaces to the coordinate metrology measured points using the information that is dynamically generated by Principal Component Analysis (PCA) of the measurement data and the corresponding fitted geometry. The developed algorithm efficiently eliminates the necessity for applying commonly used optimization methods for the fitting (localization) process, which decreases the computational cost and uncertainty of the evaluation process. Moreover, DPCA is very reliable and practical in coordinate metrology with large data sets in processes such as laser scanning and other optical methods. The results show that the proposed methodology more accurately finds fitting parameters in comparison with the other commonly used methods while the computational cost is considerably reduced.     

Minimal Realization of Linear Graph Models for Multi-physics Systems

An engineering system may consist of several different types of components,belonging to such physical"domains"as mechanical,electrical,fluid,and thermal.It is t...     

Quantum Cooperative Robotics and Autonomy

The intersection of Quantum Technologies and Robotics Autonomy is explored in the present paper.The two areas are brought together in establishing an interdisci...     

考虑进油孔有限长滑动轴承油膜力的近似解析解

针对具有进油孔的有限长滑动轴承油膜力求解问题,采用变分原理和分离变量法,求得了有限长滑动轴承油膜压力分布的近似解析表达式。将油膜压力分布的近似解析表达式在油膜存在区域上进行积分,即得到了油膜力。将提出的计算有限长滑动轴承油膜力方法与无限长轴承模型、有限元方法的计算结果进行了比较,发现了提出的方法与有限元方法的计算结果很接近。最后,研究了进油孔位置和进油压力对油膜存在区域、油膜力等的影响,研究结果表明进油孔位置和进油压力对油膜存在区域和油膜力有较大的影响。     

Fifth International Summer School on Screw-Theory Based Methods in Robotics

正3-11 September,2014University of Bologna,Bologna,Italy www.summerscrews.org summerscrews2014.ing.unibo.it SUMMER 20SCREWS 14In 2014,our screw-theory school comes to the world's oldest university.In early September,Summer Screws'14 will gather six experts in the application of screw theory in robotics and up to 40 participants at the University of Bologna,Bologna,Italy.The school will teach attendees how to apply existing methods and empower them to develop new ones in their own research.The basic theoretical notions will be introduced in a rigorous manner,emphasizing examples,applications,and exercises.Scholarships are available.     

三绕组变压器的双绕组等效建模及在Matpower中的应用

针对实际电网存在着大量的三绕组变压器,但国际上一些著名商业软件,如BPA仿真软件、Matpower这一权威潮流计算开源软件,均只提供双绕组变压器模型,限制了其在具有三绕组变压器的电力系统中的应用的问题,潮流计算是自主开发的电力系统各种应用软件的核心模块,因此依托国际权威开源程序进行二次开发,是一种较好的选择。对Matpower要求的数据格式进行了归纳,对变压器的一般的等值电路及带理想变压器的等值电路和带标幺值的等值电路进行了分析研究,提出了三绕组变压器转换为双绕组等效模型的建模方法,使得原先只适应双绕组变压器的潮流计算软件可以适用于三绕组变压器电网的潮流计算;最后以Matpower软件为例进行了案例计算,并用PSASP仿真软件进行对比验证。研究结果证明,所提出的建模方法是有效的。     

On the Relation of Load to Average Gap in the Contact Between Surfaces with Longitudinal Roughness

A computer simulation model for the contact between longitudinally-oriented rough surfaces has been formulated. This model closely duplicates the actual surf ace contact deformation behavior by taking into account the elastic interactions between the asperities. There were no assumptions made about the shapes, or any deformation behavior of the asperities, except for their obeying the laws of elasticity. The plastic deformations on the high asperity peaks were taken into account by setting a ceiling on their contact pressures at the material hardness value. The simulations used real surface profiles which were digitized from unworn circumferentially ground steel surfaces. Each pair of these profiles was mathematically combined to form an equivalent rough profile pressing against an infinitely rigid flat and having the appropriately adjusted elastic modulus. A total of 28 different pairs of profiles were used in the simulations. Each contacting pair was subjected to 30 different load levels and the local contact pressures and deformations were calculated. The contact simulations yielded some important mathematical relationships between parameters, such as the real area of contact, average gap, and average asperity load through statistical curve fitting. Two analytical functions were generated to relate the average load to average gap and the real area of contact to load.     

INTEGRAL EQUATION METHOD＇S APPLICATION IN HOLE-EDGE STRESS OF COMPOSITE MATERIAL PLATE WITH DIFFERENT SHAPED HOLES

The strength of composite plate with different hole-shapes is always one of the most important but complicated issues in the application of the composite material. The holes will lead to mutations and discontinuity to the structure. So the hole-edge stress concentration is always a serious phenomenon. And the phenomenon makes the structure strength decrease very quickly to form dangerous weak points. Most partial damage begins from these weak points. According to the complex variable functions theory, the accurate boundary condition of composite plate with different hole-shapes is founded by conformal mapping method to settle the boundary condition problem of complex hole-shapes. Composite plate with commonly hole-shapes in engineering is studied by several complex variable stress fimction. The boundary integral equations are founded based on exact boundary conditions. Then the exact hole-edge stress analytic solution of composite plate with rectangle holes and wing manholes is resolved. Both of offset axis loadings and its influences on the stress concentration coefficient of the hole-edge are discussed. And comparisons of different loads along various offset axis on the hole-edge stress distribution of orthotropic plate with rectangle hole or wing manhole are made. It can be concluded that hole-edge with continuous variable curvatures might help to decrease the stress concentration coefficient; and smaller angle of outer load and fiber can decrease the stress peak value.