Shear Failure of a Clamped Dented Tubular Beam Under Lateral Impact

- The shear failure of a rigid-plastic dented clamped tubular beam under the lateral impact of a mass is investigated. Both the denting and the impact point are in the middle span of the beam. It is assumed that denting does not spread during the shear sliding. Numerical results show that the axial force and lateral deflection of the beam are very small at the moment of the occurence of shear failure, which means that the finite deformation effect can be neglected in the shear failure analysis. Also, some aspects of the initial impact energy are investigated.     

Elasto-Plastic Analysis of Tubular Joints of Offshore Platforms by Finite Element Method

The plastic node method is reformulated by the variational principle and is applied to elasto-plastic finite element analysis of tubular joints, eventually including the effect of internal and external gussets, stiffener rings, etc., if necessary. Four different joints are studied here in detail for the elasto-plastic behavior, the strain at the hot spot, the strain concentration factor around the intersection line, and the propagation of the plastic region with loading up to collapse in order to determine the ultimate strength, safety factor, and development of the plastic field. The present results are in good agreement with the experimental results.     

Computation of Viscous Uniform and Shear Flow over A Circular Cylinder by A Finite Element Method

The incompressible viscous uniform and shear flow past a circular cylinder is studied. The two-dimensional Navier-Stokes equations are solved by a finite element method. The governing equations are discretized by a weighted residual method in space. The stable three-step scheme is applied to the momentum equations in the time integration. The numerical model is firstly applied to the computation of the lid-driven cavity flow for its validation. The computed results agree well with the measured data and other numerical results. Then, it is used to simulate the viscous uniform and shear flow over a circular cylinder for Reynolds numbers from lO0 to lO00. The transient time interval before the vortex shedding occurs is shortened considerably by introduction of artificial perturbation. The computed Strouhal number, drag and lift coefficients agree well with the experimental data. The computation shows that the finite element model can be successfully applied to the viscous flow problem.     

桶形基础平台三维有限元稳定性分析

以我国第一座桶形基础采油平台工程实例为原型，采用三维有限元计算方法对桶形基础稳定性分析。平台在波浪、风等荷载作用下，其稳定性不仅与平台的整体结构有关，而且与桶形基础及其周围土体相互作用相关。在计算中，利用薄层摩擦单元模拟土与结构间的相互作用，取得了很好的效果。分析结果表明桶形基础采油平台在设计条件下运行是较为稳定的。     

海底输油管道底砂床冲刷机理研究

设计了海底输油管道水槽冲刷试验模型,研究了海底输油管道与砂床处于不同相对位置情况下床砂起动流速的变化,采用理想流体映射定理对其进行了理论分析,探讨起动流速变化规律。结合有限元数值模拟对试验进行细化分析,研究了海底管道底砂床砂粒起动的产生机理,根据研究结果将冲刷过程划分为五个阶段。阐明了海底管道暴露冲刷的危害性和实时监测的重要性。     

Numerical simulation of solitary wave scattering by a circular cylinder array

The interaction of a solitary wave with an array of surface-piercing vertical circular cylinders is investigated numerically. The wave motion is modeled by a set of generalized Boussinesq equations. The governing equations are discretized using a finite element method. The numerical model is validated against the experimental data of solitary wave reflection from a vertical wall and solitary wave scattering by a vertical circular cylinder respectively. The predicted wave surface elevation and the wave forces on the cylinder agree well with the experimental data. The numerical model is then employed to study solitary wave scattering by arrays of two circular cylinders and four circular cylinders respectively. The effect of wave direction on the wave forces and the wave runup on the cylinders is quantified.     

南海高钙沉积物中18种常微量元素的ICP-AES测定方法研究

在利用ICP-AES分析南海高钙沉积物中的常微量元素时,钙、镁常常干扰其它元素测试。通过采用优化仪器工作参数、扣除背景值、谱线干扰校正和基体匹配的步骤,消除了元素干扰和钙、镁基体效应,提高了方法的灵敏度和准确度。通过对南海沉积物样品的大量实验和国家一级标准样验证,建立了适宜高钙海洋沉积物元素含量的ICP-AES测试方法。该方法检出限为1.55~271μg/L,相对标准偏差RSD<4.54%(n=6)。     

柴达木盆地第三系咸水湖相生油岩古沉积环境地球化学特征

在系统分析柴达木盆地西部第三系咸水湖相生油岩样品的微量元素、有机物、粘土矿物组成的基础上,揭示了研究区生油岩的无机元素和有机质组成特征;并结合沉积环境的无机与有机地球化学指标,重建了生油岩沉积时的古沉积环境。生油岩的B、Cl-及伽玛蜡烷含量表明,沉积时的水介质条件是半咸水—咸水环境,并伴随湖盆沉积中心北迁过程各层位地层的盐度发生规律性时空]化;生油岩的Fe2 /Fe3 、S2-、Pr/Ph比值、藿烷碳数分布模式及黄铁矿含量反映其沉积时的沉积环境为强还原性;粘土矿物组合特征及含量揭示这些生油岩的沉积相带介于中心咸湖相和边缘咸湖相之间。     

The buckling of a corrugated carbon fibre cylinder under external hydrostatic pressure

A theoretical and an experimental investigation was carried out, where a carbon fibre corrugated circular cylinder was tested to destuction under external hydrostatic pressure. The theoretical investigation was via the finite element method, where the structure was modelled with several orthotropic axisymmetric thin-walled shell elements. The experimental observations were aided with strategically placed strain gauges. Comparison between theory and experiment showed that the experimentally observed buckling pressure was a little lower than the theoretical prediction. This may have been due to the fact that the model had slight initial geometrical imperfections in the circumferenential direction.     

鲁苏榴辉岩的地球化学

以微量元素、稀土元素、Ｓｒ和Ｎｄ同位素变异特征为依据，确定鲁苏榴辉岩为多成因、多来源和多阶段，指出主要是在印支期扬子陆块与华北陆块碰撞造山作用过程中，挤入的上地幔碎片以及不同原岩类型的壳内高压变质岩碎块。燕山晚期的区域构造热事件使得某些榴辉岩的同位素体系再平衡。