Lower bound limit analysis using non‐linear programming

This paper describes a new formulation, based on linear finite elements and non‐linear programming, for computing rigorous lower bounds in 1, 2 and 3 dimensions. The resulting optimization problem is typically very large and highly sparse and is solved using a fast quasi‐Newton method whose iteration count is largely independent of the mesh refinement. For two‐dimensional applications, the new formulation is shown to be vastly superior to an equivalent formulation that is based on a linearized yield surface and linear programming. Although it has been developed primarily for geotechnical applications, the method can be used for a wide range of plasticity problems including those with inhomogeneous materials, complex loading, and complicated geometry. Copyright © 2002 John Wiley & Sons, Ltd.     

海洋石油平台水下夹桩器本体结构分析

水下夹桩器是一种广泛应用于海洋石油平台建设的液压夹具。水下夹桩器本体焊接在导管架上，支撑夹桩器液压缸。在水下夹桩器本体设计中，采用有限元法完成了对本体强度和刚度的结构分析；建立了有限元分析模型，用ANSYS软件进行结构分析，得到了分析结果，并将该结果与理论计算结果进行了比较，验证了有限元分析技术的有效性。设计结果满足工程要求，为改进和优化结构提供了理论依据，节省了分析计算时间。     

单桩腿有限元分析

为保证桩腿在冬季冰区海域的安全使用,对桩腿结构进行冰载荷作用下的强度分析。应用ANSYS软件建立桩腿、地基、冰相互作用的仿真计算模型,实现桩腿的力学分析。对桩腿进行了强度校核,计算出冰载荷作用下桩腿的变形及其应力状态。计算结果表明,桩腿在此冰载荷作用下强度满足安全要求。     

潜孔锤冲击作用下土体变形的有限元分析

潜孔锤冲击挤密钻进过程中周围土体的变形机理是一个高度非线性问题。针对潜孔锤在土中的面-面接触问题,运用Drucker-Prager屈服准则为判据,将土体视为DP材料,通过钻具与土之间的接触及施加冲击载荷来模拟钻进过程,从而建立了潜孔锤在土中冲击挤密钻进的有限元模型。利用非线性瞬态动力学有限元分析手段,对钻进过程中冲击力对土的作用加以研究,分析了钻具周围土体的应力、应变以及钻具与土体的摩擦情况。结果表明,在冲击载荷作用下,锥形钻头前端土体应力集中,并形成应力泡,冲击功主要用于竖向压缩土体,而水平方向的挤压作用相对较小,摩擦应力在钻头锥面附近出现峰值,是影响钻进速度的主要原因之一。     

The principles of information processing based on the numerical solution of the nonlinear heat-conduction problem. Pt. 1. The three-dimensional discrete mathematical model

A three-dimensional solution of the direct problem of heat conduction when a linear pulsed heat source acts in the plane of contact of two semibounded bodies is presented. The solution is obtained by the method of finite differences. An example of the modeling is considered. __________ Translated from Izmeritel’naya Tekhnika, No. 10, pp. 42–45, October, 2007.     

三维有限元法分析频率对接地电阻的影响

提出了用涡流场的A-V有限元分析方法计算接地系统接地电阻的方法,分析了入地电流频率的变化对接地电阻的影响。计算结果表明,频率对接地体自身电阻的影响较大,但对散流电阻的影响很小。     

Flow Control Through the Use of Topography

In this work, optimal shaft shapes for flow in the annular space between a rotating shaft with axially-periodic radius and a fixed coaxial outer circular cylinder, are investigated. Axisymmetric steady flows in this geometry are determined by solving the full Navier-Stokes equations in the actual domain. A measure of the flow field, a weighted convex combination of the volume averaged square of the L₂-norm of the velocity and vorticity vectors, is employed. It has been demonstrated that boundary shape can be used to influence the characteristics of the flow field, such as its velocity component distribution, kinetic energy, or even vorticity. This ability to influence flow fields through boundary shape may be employed to improve microfluidic mixing or, possibly, to minimize shear in biological applications.     

WSP特殊螺纹接头油井管的研制

介绍了WSP特殊螺纹接头的基本结构和设计思想,运用有限元方法,重点论述了密封设计和连接强度设计的方法和准则,并通过全尺寸试验进行了验证。计算和试验结果表明,该接头具有先进的螺纹形式、合理的扭矩台肩和金属/金属密封结构,有效地克服了API圆螺纹和偏梯形螺纹的不足,螺纹达到了与管体等强度,气密封能力达到了管体的内壁屈服压力。研究结果可以为开发更多适合油气田实际的特殊螺纹接头油井管提供参考。     

Mixed formulation of nonlinear beam on foundation elements

This paper presents an inelastic element for the analysis of beams on foundations. The element is derived from a two-field mixed formulation with independent approximation of forces and displacements. The state determination algorithm for the implementation of the element in a general purpose nonlinear finite element analysis program is presented and its stability characteristics are discussed. Numerical studies are performed to compare the model with the classical displacement formulation. The studies confirm the superiority of the proposed model in describing the inelastic behavior of beams on foundations.     

基于TiNi合金的超弹性对其相关磨损机制的FEM研究

本文在重点考虑TiNi合金高弹性变形量的前提下，采用等向强化模型，对不锈钢和超弹TiNi合金在法向接触载荷作用下的六种模型进行了有限元(FEM)分析。结果表明：在相同载荷条件下，超弹TiNi合金产生的von Mises弹性应变要高于不锈钢，但其von Mises应力和塑性应变却恰恰相反，在同一载荷下该合金发生塑性变形的区域要小于不锈钢；此外，超弹TiNi合金发生塑性变形要比不锈钢困难，所需的临界载荷值随其最大弹性变形量(屈服点处的应变值)的增加而增加。最后，基于本文的有限元计算结果对超弹TiNi合金的蘑粒磨损和疲劳磨损机制进行了讨论。