对称循环矩阵的一些结果

讨论了对称循环矩阵的性质,并研究了任意矩阵在对称循环矩阵中的逼近问题。     

平面有限元单元网格自动生成

本文通过对平面三角形单元、四边形单元节点信息及单元定义的分析,用C语言编制了能自动生成平面三节点三角形单元,四节点、八节点四边形单元的有限元问题的前处理程序FEMPRE2D．C．通过使用FEMPRE2D．C程序可大大节省数据录入人员的工作量,减少准备数据的时间,并能消除录入数据时可能发生的错误,从而为正确解决工程问题提供可靠的保证．     

大功率柴油机机体隔板三维有限元强度分析

横隔板是大功率Ｖ型柴油机机体的承力系统．本文运用有限元法对其强度进行了三维数值分析,模型中考虑了工作载荷和装配力的共同作用,以及结构的接触问题,得出了结构的应力和变形参数,为机体的设计提供了依据．     

Winkler地基上加肋板的弹性分析

把加肋板分成板和肋梁两个部分,板作为Ｗｉｎｋｌｅｒ地基上的板,用边界元方法分析,肋梁作为连续梁,用有限元方法分析,利用肋梁结点处力的平衡和位移的协调关系进行耦全水解。     

High-temperature oxidation of Al-deposited stainless-steel foils

The oxidation resistance of Al-deposited Fe–Cr–Al foils containing small amounts of La and Ce was assessed by a cyclic oxidation test with temperature varying between room temperature and 1323 K to 1423 K in static air. (1) The Al content of Fe–Cr–Al–La, Ce foils can be increased by depositing an Al layer from the vapor phase. The deposition of a 1-m-thick Al layer on both sides of the 50-m-thick foil is equivalent to a 1.5 mass% increase in the Al content. The deposited Al diffuses into the foil during heat treatment. The uniform distribution of Al is obtained by heating at 1273 K for 18 ks. (2) After the initial transition stage the oxidation follows the parabolic law until breakaway sets in. The scale consists mainly of -Al₂O₃ during the parabolic period. (3) The increase in the Al content by more than 5 mass% by the Al-deposition remarkably improves high-temperature oxidation resistance (smaller parabolic rate constant and longer protection time). (4) The Al-deposited foils have better oxidation resistance than the conventional foils with the same contents of Al and rare-earth elements. This is attributable to the different nature of the initially formed oxide on the Al-deposited foil. (5) The so-called rare-earth element effect was also observed for the Al-deposited foils. Predominant diffusion of oxygen through the Al₂O₃ scale and vacancy-sink mechanism are applicable to the present results.     

Finite element analysis of creep fracture initiation in a model superalloy material

Detailed finite element analyses were performed for a single edge-cracked specimen geometry under both plane stress and plane strain constraint for a superalloy material that obeys a power-law creep relationship. The objectives of these analyses were to elucidate the stationary creep crack-tip fields and to provide guidance for the experimental measurement of crack-tip deformations. New results demonstrate that, for both plane stress and plane strain, the angular variations in the creep strain fields do not agree with HRR-type predictions, although the radial variations are in agreement with HRR-type creep strain field predictions in a zone very near the crack tip. Thus, the use of experimental measurement of surface displacement and/or strain data for the location of HRR-type fields may not be possible, unless modifications to the existing HRR-type theory are made. It is also noted that the size of the stress-based HRR-dominance zone is only a fraction of the creep zone size in plane stress, and is very small (especially along =0°) compared to the creep zone size in plane strain. Furthermore, the dominance of the singular strain fields are at least two orders of magnitude smaller than the corresponding stress dominance zones. As such, unless the microstructural features of the material are smaller than the dimensions of the dominance zones, the basis for using stress or strain-based fracture parameters derived from the HRR-type fields for prediction of creep fracture initiation is unclear.     

非对称结构相变存储单元的三维模拟与分析

文章提出一种具有非对称结构的新型相变存储器单元结构,并通过有限元方法对该非对称结构相变存储单元进行了三维电热模拟.模拟结果表明,在相同的特征尺寸下,非对称结构相变存储单元的操作电流明显小于传统的对称型T型结构相变存储单元.     

Implementation of a strain energy-based nonlinear finite element in the object-oriented environment

The objective of the paper is to describe a novel finite element computational method based on a strain energy density function and to implement it in the object-oriented environment. The original energy-based finite element was put into the known standard framework of classes and handled in a different manner. The nonlinear properties of material are defined with a modified strain energy density function. The local relaxation procedure proposed as a method used to resolve a nonlinear problem is implemented in C++ language. The hexahedral element with eight nodes as well as the adaptation of the nonlinear finite element is introduced. The chosen numerical model is made of nearly incompressible hyperelastic material. The application of the proposed element is shown on the example of a rectangular parallelepiped with a hollow port.     

Spectral element spatial discretization error in solving highly anisotropic heat conduction equation

This paper describes a study of the effects of the overall spatial resolution, polynomial degree and computational grid directionality on the accuracy of numerical solutions of a highly anisotropic thermal diffusion equation using the spectral element spatial discretization method. The high-order spectral element macroscopic modeling code SEL/HiFi has been used to explore the parameter space. It is shown that for a given number of spatial degrees of freedom, increasing polynomial degree while reducing the number of elements results in exponential reduction of the numerical error. The alignment of the grid with the direction of anisotropy is shown to further improve the accuracy of the solution. These effects are qualitatively explained and numerically quantified in 2- and 3-dimensional calculations with straight and curved anisotropy.     

基坑开挖对邻近建筑物影响的数值模拟

基坑开挖引起的近邻建筑物沉降变形是多种因素耦合作用的结果,现有的计算理论很难考虑这种多因素的耦合作用。针对这一问题,采用大型工程软件ADINA对锚杆支护形式下基坑开挖引起的近邻建筑物沉降问题进行了数值模拟分析,得出了一些基本结论:建筑物的沉降在宽度方向变化显著,在长度和高度方向变化不明显;建筑物的水平位移在高度方向变化显著,在长度和宽度方向变化不明显,基础埋得越深对沉降的影响越小,在开挖到基础标高之前,建筑物沉降不大,当开挖到标高以后,沉降发展很快,因此在实际施工时,基础标高以上可以加快开挖速度,标高以下需要放慢开挖速度。对于结构设计而言,应该在基础以下进行加固处理,以减小由基底附加应力产生的较大沉降。