悬线式力矩器磁路设计中的有限元分析应用

光学头力矩器的空间磁场分布直接决定了力矩器的动态性能,对磁场进行准确分析是力矩器设计的前提。分析了悬线式力矩器的空间磁场产生机理,并采用有限元分析法进行了理论推导。以一款动线圈式二维对称型只读悬线式力矩器为例,采用有限元仿真软件（ANSYS）分析并设计了其空间磁场分布,对影响力矩器空间磁场分布的相关因素进行了分析。将采用有限元法对悬线式力矩器空间磁场仿真计算得出的力矩器动态特性参数与实测力矩器动态特性参数相比,其结果均符合力矩器的设计要求,证明基于有限元分析法的悬线式力矩器空间磁场设计是可行的。     

用二维时域有限差分法分析条形多层波导

为精确分析条形多层波导和多量子阱波导，本文提出了一种以二维时 限差分法为基础的全波数值方法，给出了场分布的色散特性的数值结果，并与矢量有限元法已有的结果作了比较；文中还研究了以二维时域有限差分法为基础的标量近似技术，提出了它的有效性和精度的局限性。     

Numerical study on transient flow in the deep naturally fractured reservoir with high pressure

According to the experimental results and the characteristics of the pressure-sensitive fractured formation, a transient flow model is developed for the deep naturally-fractured reservoirs with different outer boundary conditions. The finite element equations for the model are derived. After generating the unstructured grids in the solution regions, the finite element method is used to calculate the pressure type curves for the pressure-sensitive fractured reservoir with different outer boundaries, such as the infinite boundary, circle boundary and combined linear boundaries, and the characteristics of the type curves are comparatively analyzed. The effects on the pressure curves caused by pressure sensitivity module and the effective radius combined parameter are determined, and the method for calculating the pressure-sensitive reservoir parameters is introduced. By analyzing the real field case in the high temperature and pressure reservoir, the perfect results show that the transient flow model for the pressure-sensitive fractured reservoir in this paper is correct.     

声表面波在厚金属栅阵中的耦合模参数

提出了一种研究声表面波在压电晶体厚金属栅阵中传播特性的理论方法。将有限元和声表面波在周期栅阵中的变分原理分析方法相结合,在陈东培和H.A.Haus理论基础上、用有限元分析金属短路栅对声表面波传输特性的影响,将力学负载贡献的耦合模参数用有限元矩阵表示,使其适用于声表面波在厚金属或任意形状栅条中传输情况,给出了具体理论分析方法和相应的理论表达式。最后,具体研究了几种压电晶体上金、铝或银栅阵中声表面波的传输特性,通过数值计算给出了声表面波的耦合模参数。      

Free vibration of formed sandwich panel

In this paper, the free vibration of prefabricated architectural sandwich panels is studied. The core of the sandwich panel is approximated by finite prisms and the thin faces are modelled by finite strips. The finite prism-strip method is simple to program and saves considerable computing effort when compared with the finite element method. In this paper, only the dynamic characteristics of flat faced homogeneous sandwich panels are compared with results obtained by other methods, and also with the analytical solutions. Several examples are also presented for the free vibration of prefabricated architectural sandwich panels.     

不确定声场分析的二阶区间摄动有限元法

针对一阶区间摄动有限元法在声场参数不确定程度增大时误差过大的缺陷,在二阶Taylor展开的基础上推导了声学二阶区间摄动有限元法,并将其应用于区间不确定声场的声压响应分析。该方法先对声学区间有限元方程的声压响应向量进行二阶Taylor展开,获取声压响应的二阶近似响应向量;再根据二次函数极值定理获得声压响应向量的上下界。二维管道声场与轿车声腔模型的数值分析算例表明,与一阶区间摄动有限元法相比,二阶区间摄动有限元法有效提高了计算精度。因此二阶区间摄动有限元适合不确定度更大的区间不确定声场声压响应分析,具有良好的工程应用前景。      

流体加载下加肋板结构的声辐射特性研究

本文采用有限元和边界元方法对加肋板结构的声辐射进行了计算分析,研究分析了加肋板结构的板厚、板面积、板边长比、肋骨惯性矩和间距、边界条件以及板材和流体介质等对结构辐射声功率的影响,得到了一些有意义的结论,从而为揭示加板结构声辐射规律,降低结构的声辐射提供了一定的依据。     

On the Dominant Mode in Closed Trapezoidal-Groove Guide by Finite Element Method

The structure of closed trapezoidal-groove guide is similiar to that of open one, but it can be used to prevent energy from leaking out of the guide. In this paper, the propagation characteristics of dominant mode in closed trapezoidal-groove guide are analysed by using finite element method and the results are discussed.     

二维正方晶格多点缺陷声子晶体实验研究

基于超声浸水透射技术, 实验研究了有限尺寸二维正方晶格钢/水声子晶体多点缺陷模态性质. 利用COMSOL Multiphysics软件建立该声子晶体有限元计算方法, 求解了9×9超胞多点缺陷声子晶体能带结构, 把缺陷局域模态频率与数值仿真和实验结果进行对比, 结果表明: 实验数据和理论值能够很好符合. 进一步分析发现, 点缺陷数量影响声波局域效应、本征模态和传播特性, 为设计有限尺寸声波器件提供理论依据. 关键词： 声子晶体 多点缺陷 实验研究 有限元     

Finite element approach to acoustic transmission-radiation systems and application to horn and silencer design

The present paper deals with acoustical systems with an opening to semi-infinite space for sound radiation. The approach is a combination of the finite element method and the analytical method. The finite element approach is used for the hollow internal space, while the analytical approach is utilized for the open semi-infinite space. The semi-infinite space is expressed in terms of an integral with respect to the opening surface (Green's theorem). Compatibility conditions are then introduced for the interface boundary. The region to which the finite element analysis is to be applied is thus greatly reduced at the expense of additional numerical integration. A computer program is developed and, for numerical demonstration, calculations of some characteristics of conical and exponential horns, and of a practical speaker device with central post and silencers are considered. Comparisons with the measured results confirm the validity of the approach.     

Free vibration of curved sandwich beams by the method of finite elements

The finite element displacement method is used to investigate the flexural vibration characteristics of curved sandwich beams. Three displacement models are used incorporating an element having three, four and five degrees of freedom per node and various parametric studies are made to investigate their effect on the natural frequencies of curved clamped-clamped sandwich beams.     

扩散平面光波导的传递函数方法

引入一种计算光波导传播特性的新方法传递函数方法。给出了公式推导,计算了扩散各向同性及扩散各向异性平面光波导的传播特性,并与其它方法所得结果进行了比较。结果表明用传递函数方法处理折射率渐变分布的光波导问题,计算相对简单,可以得到精确的数值结果。     

On the Main Mode of Trapezoidal-Groove Guide By Finite Element Method

In this paper, the propagation properties such as the dispersion characteristics, cut-off wavelength, guide wavelength and field distribution for the main mode of trapezoidal-groove guide are analysed by using the finite element method. The dispersion is very low, and the field distribution in a trapezoidal-groove guide is similar to that of rectangular one. The results have important values in design, manufacture, and application of groove guides.     

高精度物镜波纹管致动器的线性度分析

采用有限元方法对高精度物镜波纹管致动器的几何非线性变形进行了分析,并引入线性度对波纹管致动器的性能进行了评估.通过有限元方法分析了常见的U型、S型、C型、方型及三角型波纹管的几何非线性变形,并结合最小二乘法,得到了上述各种波纹管致动器的行程及线性度.计算结果表明：在设计大行程波纹管致动器时,S型波纹管的线性度最好,为0.161%|而在设计小行程波纹管致动器时,三角形波纹管的线性度最好,为0.135%.     

横观各向同性材料中激光超声谱有限元数值模拟

研究了横观各向同性材料中激光超声波的传播特征．基于谱有限元方法,建立了横观各向同性材料中激光超声的数值模型．利用谱有限元方法模拟脉冲激光作用于材料上产生超声波及其传播的过程．讨论了横观各向同性薄板的各向异性及各向同性平面内超声波的传播特征,并分析了材料厚度的变化对产生超声波模态的影响．     

Least-squares finite element method for radiation heat transfer in graded index medium

To avoid the complicated and time-consuming computation of curved ray trajectories, a least-squares finite element method based on discrete ordinate equation is extended to solve the radiative transfer problem in a multi-dimensional semitransparent graded index medium. Four cases of radiative heat transfer are examined to verify this least-squares finite element method. Linear and nonlinear graded index are considered. The predicted dimensionless net radiative heat fluxes are determined by the least-squares finite element method and compared with the results obtained by other methods. The results show that the least-squares finite element method is stable and has a good accuracy in solving the multi-dimensional radiative transfer problem in a semitransparent graded index medium, while the Galerkin finite element method sometimes suffers from nonphysical oscillations.     

激光加热的微塑性成形有限元模拟

针对难成形材料微构件成形困难的特点,提出基于激光双面加热的微塑性成形方法。采用有限元分析软件ABAQUS,建立了基于激光加热的微镦粗圆柱形工件的热力耦合有限元模型,并对激光加热后工件的温度场分布和微塑性成形进行了模拟和应力分析。结果表明,采用激光双面加热的方法可以为微塑性成形建立合适的温度场,激光加热状态下的微塑性成形力明显降低,提高了微塑性材料的成形性能,拓宽了微塑性成形技术的应用范围。     

Analysis of force characteristics of a superconducting ball in a given magnetic field

The electromagnetic force characteristics along Z direction of a superconducting ball levitated by spherical coils with shaping blocks are calculated based on a semi-analytical method. The calculating results from the semi-analytical method are compared with the finite element analysis (FEA) method through a calculation example. The method can be applied to further analysis of dynamic characteristics and parameter optimization in the suspension system.     

Analysis of wave propagation in a thin composite cylinder with periodic axial and ring stiffeners using periodic structure theory

Wave propagation characteristics of a thin composite cylinder stiffened by periodically spaced ring frames and axial stringers are investigated by an analytical method using periodic structure theory. It is used for calculating propagation constants in axial and circumferential directions of the cylindrical shell subject to a given circumferential mode or axial half-wave number. The propagation constants corresponding to several different circumferential modes and/or half-wave numbers are combined to determine the vibrational energy ratios between adjacent basic structural elements of the two-dimensional periodic structure. Vibration analyses to validate the theoretical development have been carried out on sufficiently detailed finite element model of the same dimension and configuration as the stiffened cylinder and very good agreement is obtained between the analytical and the dense finite element results. The effects of shell material properties and the length of each periodic element on the wave propagation characteristics are also examined based on the current analytical approach.     

Impact on short length bars

A finite element method for the solution of an axisymmetric wave propagation problem of a bar of finite length is proposed. The results are obtained for a uniform bar with (i) a displacement input and (ii) a stress input. Also results are obtained for a discontinuous bar with stress input. They are compared with the existing finite difference solutions and experimental results. It is observed that the results are in close agreement. The study is then extended to the case of bars with an hemispherical end. The advantage of using the finite element method for such problems is indicated. Finally the results for a composite bar comprising a hallow cylinder and hemisphere are obtained by using the finite element method. Experiments are conducted to verify these results.