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关键词： 有限元法   自升式钻井船   钻井平台   桩靴   筒型基础   地基  

摘要： 自升式钻井船和筒型基础平台都属于浅基础结构物。在完成钻井作业后 ,桩靴较大的自升式钻井船在拔桩中会对筒型基础平台的地基产生一定的影响。利用通用的有限元程序ANSYS软件 ,以渤海 8号自升式钻井船和歧口 17 2筒型基础平台为对象 ,在相同荷载和约束下分 3步模拟了自升式钻井船桩靴的拔出过程 ,就桩靴在拔出过程中对筒型基础平台地基强度的影响进行了三维有限元分析。分析结果表明 ,在设计中将地基承载力提高 10 % ,自升式钻井船就可以在桩靴距筒型基础筒体 12

关键词： low-velocity impact   cohesive-based finite element technique   composites   composite laminates   simulation   impact-induced delamination   transverse matrix cracks   traction-separation relation   critical matrix cracks  

摘要： The mechanism of damage initiation and growth in layered composites subjected to low-velocity impact is simulated using a cohesive-based finite element technique. The numerical technique used comprises cohesive elements sandwiched between the regular finite elements. The basic structure of the formulation is presented, followed by the results of the simulation. The success of this numerical technique is dependent on the cohesive model used. The cohesive model is a thermodynamically-based phenomenological model, describing the damage ahead of a crack tip. Details of the rate-independent cohesive model used in this study are also presented.

关键词： 弹性应变梯度理论   平面18-DOF   三角形应变梯度单元   C^0-1分片检验   孔边应力  

摘要： 基于细观有限元弹性应变梯度理论,首次提出应变梯度有限元的C0-1分片检验条件及其变分基础和一种构造应变梯度单元的方法.与常规的C0分片检验和C1分片检验不同,C0-1分片检验要求检验函数为满足平衡方程的二次函数,并同时通过线性平面应力C0分片检验和应变梯度常曲率的C1分片检验.进一步提出一个平面18-DOF三角形应变梯度单元(RCT9+RT9),算例表明该单元通过C0-1分片检验,无伪零能模式,并有较高的精度.

关键词： 桶形基础   本构模型   地震动力   平台   三维弹塑性有限元   软土   应力应变关系   滩海   模拟   动力分析  

摘要： 在经典的D-P本构模型基础上,通过改进其屈服准则,引入硬化曲线建立了改进的D-P模型,使该本构模型能很好地模拟大港滩海软土的应力应变关系。利用MARC程序作为平台,建立了滩海桶形基础平台整体有限元动力分析模型,并对我国第一座桶形基础平台进行了三维弹塑性地震时程动力分析,得到了一些很有用的结论。

关键词： BRAIN   REGULARIZATION   LOCALIZATION   ALGORITHMS   ANISOTROPY  

摘要： The inverse problem in electro- and magneto-encephalography (EEG/MEG) aims at reconstructing the underlying current distribution in the human brain using potential differences and/or magnetic fluxes that are measured noninvasively directly, or at a close distance, from the head surface. The simulation of EEG and MEG fields for a given dipolar source in the brain using a volume-conduction model of the head is called the forward problem. The finite element (FE) method, used for the forward problem, is able to realistically model tissue conductivity inhomogeneities and anisotropies, which is crucial for an accurate reconstruction of the current distribution. So far, the computational complexity is quite large when using the necessary high resolution FE models. In this paper we will extend the concept of the EEG lead field basis to the MEG and present algorithms for their efficient computation. Exploiting the fact that the number of sensors is generally much smaller than the number of reasonable dipolar sources, our lead field approach will speed up the state-of-the-art forward approach by a factor of more than 100 for a realistic choice of the number of sensors and sources. Our approaches can be applied to inverse reconstruction algorithms in both continuous and discrete source parameter space for EEG and MEG. In combination with algebraic multigrid solvers, the presented approach leads to a highly efficient solution of FE-based source reconstruction problems.

关键词： PHOTONIC CRYSTAL FIBERS   OPTICAL-FIBERS   LEAKY MODES   PROPAGATION   DISPERSION   DEGENERACY   SILICA   INDEX  

摘要： A finite-element-based vectorial optical mode solver is used to analyze microstructured optical waveguides. By employing 1st-order Bayliss-Gunzburger-Turkel-like transparent boundary conditions, both the real and imaginary part of the modal indices can be calculated in a relatively small computational domain. Results for waveguides with either circular or non-circular microstructured holes, solid-or air-core will be presented, including the silica-air Bragg fiber recently demonstrated by Vienne et al. (Post-deadline Paper PDP25, OFC 2004). The results of solid-core structures are in good agreement with the results of other methods while the results of air-core structure agree to the experimental results. (C) 2004 Optical Society of America.

关键词： solids   finite element   finite rotation   failure  

摘要： In the second article of the series, the vector form intrinsic finite element is extended to formulate plane solid elements, a three-node triangular element and a four-node isoparametric element. Also, conceptual differences of the intrinsic element and traditional element based on variational formulation are discussed.

关键词： 分布反力   弹性基础板   半无限地基   有限单元法   薄板弯曲   节点位移  

摘要： 按平面问题与薄板弯曲问题描述基础板,建立了基础板同地基接触面上的节点位移与板中心面位移之间的转换关系式.假设板上荷载按分布力形式传递到地基中,根据半无限空间上某节点力与该处的位移关系,用高斯积分法建立了地基表面分布力与节点位移关系表达式.据此,再根据地基与板间的位移协调及静力平衡条件,建立了以板的中心面位移为未知量的有限元方程.算例表明,考虑地基分布反力十分必要.

ISBN: (纸本)7111142926

ISBN: (纸本)7118035629