Mechanism investigation of welding induced buckling using inherent deformation method

Due to the increasing use of thin plates in lightweight welded structure, welding induced buckling may occur in such thin plate welded structure. In this study, welding induced buckling of thin plate welded structure is investigated using the eigenvalue analysis and elastic Finite Element (FE) analysis based on inherent deformation theory, and the mechanism of welding induced buckling is clarified.Bead-on-plate welding is first examined. Measured out-of-plane welding distortion indicates that saddle type buckling is produced after cooling. Eigenvalue analysis shows the computed lowest buckling mode is the saddle type and the corresponding critical force is less than the applied tendon force evaluated by Thermal–Elastic–Plastic (TEP) Finite Element (FE) analysis beforehand. Using elastic Finite Element (FE) analysis in which all components of inherent deformation are used and also considering initial deflection, out-of-plane welding distortion is predicted with high accuracy compared with measurement. It is also concluded that tendon force (longitudinal inherent shrinkage) is the dominant reason of buckling and it determines the buckling mode, and initial deflection and inherent bending are considered to be disturbances which trigger buckling.Later, a thin plate stiffened welded structure with fillet welded joints is examined. Although welding did not induce buckling of plate fields in bending modes in the considered thin plate stiffened welded structure, the whole stiffened welded structure buckles in a twisting mode, while plate panels remain unbuckled. Eigenvalue analysis gives the twisting buckling mode as the lowest buckling mode. However, in stiffened welded structures, not only tendon force (longitudinal inherent shrinkage) but also transverse inherent shrinkage is responsible for buckling. The good agreement between computed and measured out-of-plane welding distortion shows that the elastic Finite Element (FE) analysis using inherent deformation theory is an advantage of the computational approach to predict welding distortion in large-scale and complex welded structure with enough computational accuracy.     

基于MAS的供应链可靠性综合评估模型

为了保证供应链的正常运作,构建了一种基于MAS的供应链可靠性综合评估模型。模型上最底层的节点Agent利用遗传投影寻踪法计算节点可靠度,中间层的子系统Agent利用特征值赋权法计算子系统可靠度,最上层的系统Agent负责供应链整体可靠性评估。应用实例表明,该模型可以从局部到整体对供应链可靠性进行全面评估。     

层叠板瞬态随机温度场的分析

以各层材料不相同的层叠板为研究对象,在热传导和对流边界条件下,利用伽辽金法推导瞬态温度场的有限元微分方程,研究当所有结构参数均具有随机性时,通过方程解耦、特征对随机性分析以及二阶矩方法,对瞬态随机温度场的数字特征进行求解.以三层板结构为算例,并将所得结果与Monte Carlo数值模拟法的结果进行比较,证明文中方法的功效性.     

基于树状小波分解的纹理图象检索

针对图象检索应具有简单、快速、有效等要求,提出了一种采用树状小波分解特征的纹理图象检索方法,该方法可以在相应的能量准则下,自适应地对图象进行了带分解,同时可利用小波函数分解的多分辨率与多方向特性,来形成能够在一定程度上对图象进行精确描述的特征矢量;在此基础上,又采用基于图象特征值的主分量分析方法,有效降低了特征矢量的维数;另外,基于用户需求的分层检索,还满足了用户不同层次的需求。实验结果表明,该算法快速,有效,具有较强的应用价值。     

A blocked QR-decomposition for the parallel symmetric eigenvalue problem

In this paper we present a new stable algorithm for the parallel QR-decomposition of “tall and skinny” matrices. The algorithm has been developed for the dense symmetric eigensolver ELPA, where the QR-decomposition of tall and skinny matrices represents an important substep. Our new approach is based on the fast but unstable CholeskyQR algorithm (Stathopoulos and Wu, 2002) [1]. We show the stability of our new algorithm and provide promising results of our MPI-based implementation on a BlueGene/P and a Power6 system.     

New Upper and Lower Eigenvalue Bounds for the Solution of the Continuous Algebraic Riccati Equation

In this paper, applying majorization inequalities, new upper and lower bounds for summation of eigenvalues (including the trace) of the solution of the continuous algebraic Riccati equation are presented. Corresponding numerical examples illustrate that our new bounds extend some of the recent results.     

泛函分析对线性代数的点滴应用

本文利用泛函分析方法,论述了线性方程组理论与二次型,为工科线性代数教材的改革,提供了一个方案。     

NETWORK ANALYSIS OF EIGENVALUE PROBLEM FOR MULTILAYER DIELECTRIC WAVEGUIDE CONSISTING OF ARBITRARY NUMBER OF LAYERS

In this paper,the eigenvalue problem of a multilayer dielectric waveguide consisting of arbitrarynumber of layers is solved by the microwave network method.A general program with the function of com-puter graphics has been developed for analyzing the dispersion characteristics and the electromagnetic fielddistributions of an N layer dielectric waveguide.As an example of practical applications,the procedure ofmode conversion and mode separation in dielectric branching waveguides is vividly demonstrated throughanalyzing the field distributions of asymmetric multilayer dielectric structures and the general rules of modeconversion are discussed.     

Interfacial crack tip field in anisotropic/isotropic bimaterials

The co-cured joint is more efficient than the adhesively bonded joint for composite structures because of its several advantages. However, failure analysis of the co-cured joint has just a little been reported since the co-cured joining method was introduced. Observing based on the experimental results, failure starts at the interface corner of the co-cured joint. Therefore, it is important to consider stress intensities at the interface corner of the co-cured joint.

In this paper, the eigenvalue problem was used to determine asymptotic stress and displacement fields near the interface corner between composite and steel adherends. For obtaining stress intensities at the interface corner a path independent conservative line integral was used.     

重根特征灵敏度分析

本文建立了一种确定具有重特征值系统之特征灵敏度的新方法。所提出的方法以Ｍｏｏｒｅ─Ｐｅｎｒｏｓｅ广义逆技术为基础。对于重根结构系统的特征导数计算，它是一项有效的技术。