Adaptive lagrange finite element methods for high precision vibrations and piezoelectric acoustic wave computations in SMT structures and plates with nano interfaces

This paper discusses the validity of (adaptive) Lagrange generalized plain finite element method (FEM) and plate element method for accurate analysis of acoustic waves in multi-layered piezoelectric structures with tiny interfaces between metal electrodes and surface mounted piezoelectric substrates. We have come to conclusion that the quantitative relationships between the acoustic and electric fields in a piezoelectric structure can be accurately determined through the proposed finite element methods. The higher-order Lagrange FEM proposed for dynamic piezoelectric computation is proved to be very accurate (prescribed relative error 0.02%–0.04%) and a great improvement in convergence accuracy over the higher order Mindlin plate element method for piezoelectric structural analysis due to the assumptions and corrections in the plate theories. The converged Lagrange finite element methods are compared with the plate element methods and the computed results are in good agreement with available exact and experimental data. The adaptive Lagrange finite element methods and a new FEA computer program developed for macro- and micro-scale analyses are reviewed, and recently extended with great potential to high-precision nano-scale analysis in this paper and the similarities between piezoelectric and seismic wave propagations in layered structures and plates are stressed. Project supported by SRF for ROCS, SEM of China and partially by Zhejiang Provincial Natural Science Foundation (NSF) of China.     

Adaptive Lagrange finite element methods for high precision vibrations and piezoelectric acoustic wave computations in SMT structures and plates with nano interfaces

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The finite element method magnetics (FEMM) freeware package: May it serve as an educational tool in teaching electromagnetics?

Finite Element Method Magnetics (FEMM) is an open source finite element analysis software package for solving electromagnetic problems. The program addresses 2D planar and 3D axisymmetric linear and nonlinear harmonic low frequency magnetic and magnetostatic problems and linear electrostatic problems. It is a simple, accurate, and low computational cost freeware product, popular in science and engineering. However its educational value has been underestimated. Use of the package in education is quite rare. The aim of this paper is to explore the capability of FEMM to meet as a complementary tool the needs of teaching electromagnetics in higher education. In order to demonstrate its use and exhibit the aid it offers in the teaching of electromagnetics illustrative examples are given. Evaluations in both qualitative and quantitative data have also been conducted and presented. Useful conclusions about its usage and potential applications in the teaching of electromagnetics in higher education are finally drawn.     

3D Magnetic Field Computation of a Permanent MagnetDisc-Type Generator Using Scalar Potential Method

The three-dimensional magnetic field of a permanent magnet (PM) disc-type generator is analyzed by the scalar potential method. In the analysis the permanent magnets are taken as magnetic charges. Hexahedron element meshes are automatically generated by a pre-processing program developed by the authors. The flux density is computed by a 3D scalar potential method program. Based on the finite element analysis the induced emf, current, armature reaction effects and electromagnetic torque of the disc machine are all calculated.     

基于matlab的空间三维桁架结构受力分析通用程序设计

介绍了空间三维桁架结构受力分析的有限元方法，运用matlab强大的数学计算功能，解决刚度矩阵的组集和约束条件的处理等问题，编制了通用的求解程序．该程序可以求解任意工作条件下的空间三维桁架的受力问题．     

基于MATLAB平面桁架有限元分析研究

基于平面桁架有限元分析的基本原理,利用MATLAB软件对某平面桁架编制了计算程序,得到了结构的内力计算结果、变形图和结构的动力特性,并将计算结果与ANSYS有限元分析软件的结果进行比较.结果表明,二者的计算结果一致.利用MATLAB可以编制结构有限元分析程序,计算速度快,数据准确,并能为复杂结构有限元分析提供参考.     

基于Plaxis 2D的基坑支护中内支撑对支护桩的影响分析

借助Plaxis 2D的有限元分析程序,计算不同支撑刚度下的支护桩变形及内力,揭示了支护桩支撑轴力与支撑刚度之间的变化规律,分析了两者比值对支护桩的影响曲线,并得出近似比值,用以指导工程实际。     

Finite element model for linear-elastic mixed mode loading using adaptive mesh strategy

An adaptive mesh finite element model has been developed to predict the crack propagation direction as well as to calculate the stress intensity factors （SIFs）, under linear-elastic assumption for mixed mode loading application. The finite element mesh is generated using the advancing front method. In order to suit the requirements of the fracture analysis, the generation of the background mesh and the construction of singular elements have been added to the developed program. The adaptive remeshing process is carried out based on the posteriori stress error norm scheme to obtain an optimal mesh. Previous works of the authors have proposed techniques for adaptive mesh generation of 2D cracked models. Facilitated by the singular elements, the displacement extrapolation technique is employed to calculate the SIK The fracture is modeled by the splitting node approach and the trajectory follows the successive linear extensions of each crack increment. The SlFs values for two different case studies were estimated and validated by direct comparisons with other researchers work.     

Damage identification in beam-type structures using pseudo strain energy density and grey relation coefficient

Based on pseudo strain energy density （PSED） and grey relation coefficient （GRC）, an index is proposed to locate the damage of beam-type structures in time-domain. The genetic algorithm （GA） is utilized to identify the structural damage severity of confirmed damaged locations. Furthermore, a systematic damage identification program based on GA is developed on MATLAB platform. ANSYS is employed to conduct the finite element analysis of com- plicated civil engineering structures, which is embedded with interface technique. The two-step damage identification is verified by a finite element model of Xinxingtang Highway Bridge and a laboratory beam model based on polyvi- nylidens fluoride （PVDF）. The bridge model was constructed with 57 girder segments, and simulated with 58 meas- urement points. The damaged segments were located accurately by GRC index regardless of damage extents and noise levels. With stiffness reduction factors of detected segments as variables, the GA program evolved for 150 generations in 6 h and identified the damage extent with the maximum errors of 1% and 3% corresponding to the noise to signal ratios of 0 and 5%, respectively. In contrast, the common GA-based method without using GRC index evolved for 600 generations in 24 h, but failed to obtain satisfactory results. In the laboratory test, PVDF patches were used as dynamic strain sensors, and the damage locations were identified due to the fact that GRC indexes of points near damaged ele- ments were smaller than 0.6 while those of others were larger than 0.6. The GA-based damage quantification was also consistent with the value of crack depth in the beam model.     

CW6163D型机床动态特性研究

通过对CW6163D型机床的激振试验,识别其模态参数和模态振型,掌握了该机床的结构动态特性,分析了该机床的薄弱环节.基于结合面基础特性参数,研究了机床导轨结合部特性的有限元建模方法,并将其用于机床整机的特性分析,为机床整机特性分析中结合部特性参数的确定提供了一种方法.通过有限元计算和试验模态分析的比较,证明两者能很好地吻合,为改善机床的动态特性提供科学的依据.     

现代结构力学教学中的有限元法

分析了结构力学在土木工程专业中的重要性,尤其是有限元法的应用,将有限元法的学习与实践作为与经典结构力学同样重要的课程部分,构建教学重点并加强实践过程。强调理解"离散"与"集成"的思想和计算程序调试的过程,给出了有限元程序上机实践和ANSYS软件上机实践的建议,包括学时、重点内容、实践流程以及参考例题。     

网格图形显示三维有限元模型

为了减轻有限元前期数据整理工作,正确划分有限元网格,提出了三维有限元模型的网格图形显示算法及程序的实现.     

基于随机场的动力分析

考虑材料空间多样性,材料性能特性例如弹性模量或波松比被看成随机过程。本文采用随机场的中心点方法,在材料性能特性、几何尺寸、所受载荷被看成随机的情况下,结构振动方程先用Newmark法转化为静力问题。二阶Taylor展开随机有限元被用于结构振动分析,推导简单,易于编程。给出了基于随机有限元的混凝土悬臂梁的振动分析的一个计算实例,对计算结果做了比较,本文提出的方法是有效的。     

基于形状记忆合金的多层钢框架被动控制研究

通过形状记忆合金（SMA）材料的超弹性性能试验确定了SMA材料的各项力学性能参数,根据结构的振动控制理论,针对框架结构剪切型变形的特点,建立了SMA拉索对结构进行被动控制的运动方程。然后针对不同的控制方案,应用ANSYS有限元程序,仿真分析了多层钢结构模型在地震激励下的高度非线性动力时程响应,研究了SMA被动拉索的控制效果。     

直接采用二维多截面时步法有限元的斜槽异步电机模型

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Initiating minorities into the professoriate: One school's model

The shortage of minority faculty presence on college and university campuses has been a matter of some concern in recent years. The purpose of this article to describe one college's initiative to address this issue. The West Virginia Graduate College's Minority Faculty Fellowship Program was designed to recruit minority doctoral students who are at the dissertation stage of their program. Appointed as non-tenure track faculty members, fellows are provided with experiences that will help them acclimate to the professoriate. This article describes the program, highlights the institutional benefits, outlines the program's strengths and weaknesses, and makes recommendations for those interested in developing similar programs.John S. Gooden, Ed.D. (University of Massachusetts at Amherst), is an Assistant Professor in the Department of Educational Leadership and Counseling at Eastern Michigan University. He is a former West Virginia Graduate College Faculty Fellow. His areas of professional expertise include administrative certification, school violence, and educational technology. Paul A. Leary, Ed.D. (University of Massachusetts at Amherst), is a Professor in the Educational Leadership Department at West Virginia Graduate College. His areas of professional interest focus on educational governance, educational policy, and program evaluation. Ronald B. Childress, Ed.D. (The University of Tennessee at Knoxville), is a Professor in the Departments of Elementary Education, Secondary Education, and Educational Leadership at West Virginia Graduate College. His areas of professional expertise include curriculum planning, program evaluation, and program management.     

水电站坝体基础结构施工过程及结构分析

依据现行水利电力工程规范规定的方法扣原则，对水电站坝体基础结构进行结构形式扣施工过程的方案设计，并对各方案作有限元结构应力及可靠度分析，以比较方案及选择坝体尺寸。     

壳体热弹塑性问题的有限元求解方法

本文根据厚壳单元的基本理论,设计了壳体热弹塑性问题的有限元分析程序。经验证,该程序在计算各种工况下壳体的应力应变场时具有较高的精度。     

An analysis of professional practice Ed.D. dissertations in Educational Technology

The University of Florida offers an online professional practice Ed.D. focused on Educational Technology. Twenty-three students have completed professional practice dissertations and graduated since the program’s inception in 2008. The purpose of this article is to share what these dissertations have looked like and to begin a dialogue about professional practice dissertations completed in online educational technology programs. Specifically, we (1) provide an overview of different ways professional practice Ed.D. dissertations are structured, (2) share guiding principles for professional practice dissertations in our Ed.D. program, (3) analyze the ways in which these guiding principles played out in the dissertations and (4) discuss the implications of our analysis for our program and for other online professional practice programs in Educational Technology.     

金属拱型波纹屋盖加强后受力性能研究

建立了加强后的金属拱型波纹屋盖模型,利用ANSYS有限元分析软件对加强后的波纹拱进行了荷载作用下几何非线性有限元分析,并与原波纹拱进行了变形与应力的比较。计算结果表明,加强后的波纹拱对约束结构位移变形有较好的效果,且提高了结构的承载能力,这一结论为该结构进行抗风、抗雪等设计提供了有益参考。