Efficient mixed Timoshenko–Mindlin shell elements

The precise representation of rigid body motions in the displacement patterns of curved Timoshenko–Mindlin (TM) shell elements is considered. This consideration requires the development of the strain–displacement relationships of the TM shell theory with regard to their consistency with the rigid body motions. For this purpose a refined TM theory of multilayered anisotropic shells is elaborated. The effects of transverse shear deformation and bending‐extension coupling are included. The fundamental unknowns consist of five displacements and eight strains of the face surfaces of the shell, and eight stress resultants. On the basis of this theory the simple and efficient mixed models are developed. The elemental arrays are derived using the Hu–Washizu mixed variational principle. Numerical results are presented to demonstrate the high accuracy and effectiveness of the developed 4‐node shell elements and to compare their performance with other finite elements reported in the literature. Copyright © 2002 John Wiley & Sons, Ltd.     

机器人手指尖六维力/力矩传感器的研制

提出一种机器人手指尖六维力／力矩传感器，并对其弹性体结构进行详细论述；分析应变量与测量量的对应关系；采用现代设计手段对弹性体进行模态分析，并介绍了传感器放大处理电路，给出实验结果。     

TiAl基合金板材制备技术的发展现状

综述了TiAl基合金板材制备技术的发展现状。介绍了的制备TiAl基合金板材三种技术的工艺过程及制得的TiAl基合金板材的显微组织和力学性能。     

机动武器系统的含间隙动力学研究--下篇:系统仿真

本文把中篇建立的间隙铰模型引入多体系统动力学分析中,得到了一种处理含间隙多体系统动力学问题的一般方法.应用这种方法对机动武器的发射过程进行了原理性的仿真,验证了前面建立的碰撞模型和间隙模型,并分析了间隙对导弹运动状态的影响.导弹发射过程具有变拓扑的特点,本文方法提供了一种处理这类问题的思路.     

The need for style systems in ODA

Many advanced document systems provide a formatting mechanism called ‘style sheets’ Style sheets provide a great deal of flexibility in describing a document's format, and allow easy maintenance of different house styles for a collection of documents. In this paper, we describe the basics of general style sheet systems, argue that successful document interchange must include the exchange of style sheet information, and evaluate ODA's style mechanism against this requirement.     

A new stereological principle for test lines in three-dimensional space

A new principle is presented to generate isotropic uniform random (IUR) test lines hitting a geometric structure in three-dimensional space (3D). The principle therefore concerns the estimation of surface area, volume, membrane thickness, etc., of arbitrary structures with piecewise smooth boundary. The principle states that a point-sampled test line on an isotropic plane through a fixed point in 3D is effectively an invariant test line in 3D. Particular attention is devoted to the stereology of particles, where an alternative to the surfactor method is obtained to estimate surface area. An interesting case arises when the particle is convex. The methods are illustrated with synthetic examples.     

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白马庙气田蓬莱镇气藏储层致密 ,孔隙结构复杂 ,非均质性强 ,单井产能低 ,研究储层特征和受控因素 ,加强储层改造方是气藏效益开发的出路。储层精细研究揭示 ,气井产能受沉积相和构造条件控制 ;高、中产井与大而厚、物性好的河口坝、河道砂坝沉积微相有关 ,纵向上具很强的层段性 ,主产层集中在Ⅳ～③、Ⅲ～③两套砂组 ,其钻探成功率分别达 82 %和 10 0 % ;平面上多分布于主体构造和东南鼻状突起 ,二者高、中产能井分别占 30 %和 70 %。在深入的地质研究和储层压裂评层选井的基础上 ,采用多层打开、分层压裂、多层合采的方法可提高气井产能 ,并形成了一套行之有效的压裂评层选井的综合配套技术。采用该技术优选出 19口井 ,已实施 5口井全获成功 ,气产量成倍或十几倍增加 ,其中白浅 4 5井气无阻流量高达 18× 10 4m3 /d ,白浅 38井投产 16 5d净增产值 10 0余万元     

高镁瓷工艺特性研究和应用

本文总结了ＭｇＯ－ＳｉＯ２－Ａｌ２Ｏ３系的高镁瓷配方、增塑及烧成工艺特性的研究过程与应用结果；介绍了适应大生产的高镁瓷制作工艺。     

On the boundary-layer control through momentum injection: Studies with applications

The concept of moving surface boundary-layer control, as applied to a Joukowsky airfoil, is investigated through a planned experimental programme complemented by numerical studies. The moving surface was provided by rotating cylinders located at the leading edge and/or trailing edge as well as top surface of the airfoil. Results suggest that the concept is quite promising, leading to a substantial increase in lift and a delay in stall. Depending on the performance desired, appropriate combinations of cylinder geometry, location and speed can be selected to obtain favourable results over a wide range of angle of attack. Next, effectiveness of the concept in reducing drag of bluff bodies such as a two-dimensional flat plate at large angles of attack, rectangular prisms and three-dimensional models of trucks is assessed through an extensive wind tunnel test-programme. Results show that injection of momentum through moving surfaces, achieved here by introduction of bearing-mounted, motordriven, hollow cylinders, can significantly delay separation of the boundary-layer and reduce the pressure drag. The momentum injection procedure also proved effective in arresting wind-induced vortex resonance and galloping type of instabilities. A flow visualization study, conducted in a closed-circuit water tunnel using slit lighting and polyvinyl choride tracer particles, adds to the wind-tunnel and numerical investigations. It shows, rather dramatically, the effectiveness of the moving surface boundary-layer control (MSBC). The Sabita Chaudhury Memorial Lecture The models were fabricated in the Mechanical Engineering Workshop. The assistance of M/s E Abell, P Hurren and D Camp in the design and construction of the models is gratefully acknowledged. The investigation was supported by the Natural Sciences and Engineering Research Council of Canada, Grant No. A-2181.     

ON THE MODELLING OF PARTICLE-BODY INTERACTIONS IN STOKES FLOWS INVOLVING A SPHERE AND CIRCULAR DISC OR A TORUS AND CIRCULAR CYLINDER USING POINT SINGULARITIES

Few exact solutions of the Stokes equations are known, even for steady or quasi-steady flows, involving finite sized bodies, and numerical techniques generally have to be resorted to for finding solutions. However, quite effective modelling of flows involving complicated boundary geometries is possible using the three-dimensional Stokeslet and rotlet point singularities. Two problems are studied in detail. In the first example, exact solutions for the three-dimensional Stokeslet and rotlet placed axisymmetrically along the axis of a circular disc are found and combined with Brenner's first order interaction formulae to determine the effect of the presence of the disc on the force and torque acting on a particle whose dimensions are small compared with its distance from the disc. The results are compared with those of a full numerical integration of the Stokes equations for a sphere translating towards a disc. In the second example, Brenner's first order wall correction theory is applied to the motion of a particle in a circular cylinder using the exact solutions for a torus translating or rotating in isolation. The theoretical predictions for the drag on a torus settling symmetrically in a circular cylinder are compared with those determined experimentally.