填充型高导热复合材料的有限元仿真研究

为研究微米颗粒填料对填充型高导热复合材料导热性能的影响,本研究构建了填料颗粒随机分布的复合材料有限元模型,分别计算、分析了填料的填充比例、粒径、导热系数、颗粒形状等因素对复合材料导热系数的影响.结果表明:随着填料填充比例提高、填料颗粒长径比增大,复合材料的导热系数明显提高;在不考虑界面热阻和颗粒团聚的情况下填料粒径对导热系数的影响很小;填料自身的导热系数对复合物的导热性能影响很小;在不考虑界面热阻的情况下,能否有效地形成导热通道是决定填充型复合材料导热系数的关键.     

基于有限元方法的冰箱箱体发泡模具补偿算法

针对企业降成本过程中因为板材厚度降低导致发泡过程中箱内壳局部变形等质量缺陷,发现发泡模具与箱内壳的配合准确程度是主要原因.基于有限元方法对箱内壳变形的原因进行了模拟和分析,在传统模具设计的基础上,得出了模具设计时的补偿算法,采用该算法对某型号冰箱箱体发泡模具进行了设计,生产实践证明完全可行.     

转子热应力计算中的有限元方法

针对汽轮机转子热应力有限元分析方法 ,分析常用的位移有限元计算热应力时的精度问题 ,简述应力杂交元、杂交元等多变量杂交有限元的优缺点。分析表明杂交有限元的应力计算结果精度高 ,当杂交有限元应用于转子热应力的计算时 ,热应力与位移具有相同的计算精度 ,而且可以有效地消除位移有限元中温度场插值函数误差对应力场右端项的影响。     

干涉配合复合材料强化机理的研究

通过有限元分析与理论推导,系统研究了应力集中、残余应力、预紧力对复合材料干涉配合接头疲劳寿命的影响。研究结果表明复合材料干涉配合接头的有效应力集中系数小于复合材料间隙配合接头的有效应力集中系数;复合材料干涉配合接头在配合部位具有较高的残余压应力;预紧力对整个接头的有效应力集中系数有一定缓解作用,随着预紧力的增大复合材料板上的应力集中系数有缓慢减小趋势。     

电容器电场有限元方法研究

简要介绍有限元方法,并把有限元方法同电容器内部电位计算问题相结合,同时以一个具体的实例较为深入地说明.通过仿真表明,有限元方法对电容器内部电位的计算具有较高的可靠性.图4参6     

伺服设计中的有限元建模

带宽是伺服控制系统设计中的核心问题,但其设计受到对象的高频机械谐振的影响。本文用有限元方法对三轴转台控制对象进行动力学分析,建立机械谐振的频域模型,为带宽设计提供了依据,由于转台的转动自由度将造成有限元模型刚度矩阵奇异,文中先定转轴进行有限元分析,再于简化模型中推导释放情形,这种方法具有较小的计算复杂度。适合于现有条件的控制系统建模应用。     

脉搏图像传感器有限元建模

建立脉搏图像传感器模型,依据模型对软性探测触头上的橡胶薄膜进行受力分析,了解薄膜变形情况,通过薄膜变形情况提取脉管运动的特征信息。橡胶薄膜的受力分析采用有限元法,运用有限元软件abaqus建立传感器有限元模型,应用abaqus／explicit对有限元模型进行动态分析,计算薄膜上点的竖向位移量,即可提取相应的脉搏波形。     

汽车制动盘高精度有限元建模及试验研究

为提高汽车制动盘的建模精度,分别采用3类单元建立制动盘有限元模型.通过计算与试验获得制动盘前六阶固有频率,对比发现采用四面体、1阶和2阶六面体单元建立的有限元模型与测试所得的前六阶固有频率误差分别小于9％、2％和7％.进而比对1阶六面体有限元模型计算与测试振型,并对其进行约束模态分析.结果 表明,计算与测试所得制动盘前...     

复合电介质介电性能有限元仿真

以聚合物基体添加具有非线性填料非线性复合电介质为研究对象,利用编程实现填料颗粒在基料中随机分布和基于蒙特卡洛(MC)模拟的模型随机构建,并通过三维有限元数值分析软件求得不同电压激励下的响应电流.采用时域最小二乘法对仿真得到的总电流进行分解并获得材料的宏观介电参数与电场强度的关系.结果表明:填料在空间的随机分布导致复合材...     

碳纤维复合材料红外无损检测的数值分析

运用大型有限元分析软件ANSYS,对含缺陷的碳纤维复合材料进行瞬态温度场有限元数值模拟,计算分析了缺陷深度、大小和厚度对碳纤维复合材料表面热像对比度的影响规律。结果表明,当缺陷大小一定时,距试样表面越近的缺陷越易检测;当缺陷位于试样一定深度时,缺陷大小在一定范围内,大缺陷容易检测;当缺陷表面与试样表面距离一定时,缺陷越厚越易检测。     

Comparison between line and surface integral formulations of the hybrid mode‐matching/two‐dimensional finite element method

The hybrid mode‐matching/two‐dimensional‐finite‐element (MM/FEM2D) technique has been proposed for the analysis of discontinuities with waveguides of arbitrary cross section; this technique combines the computational efficiency of modal analysis with the versatility and flexibility of the FEM approach. In this paper, we present in detail a surface‐integrals and a line‐integrals formulation of the hybrid MM/FEM2D technique, in case the ‘Standard Formulation’ is used as FEM2D formulation. Such formulations allow computing analytically both the normalization and the coupling integrals. Furthermore, we compare the accuracy obtained by using the line‐integrals and the corresponding surface‐integrals formulation. To these aims we present several numerical results. Copyright © 2004 John Wiley & Sons, Ltd.     

A characteristics-based finite element method for transmission line problem

This paper presents a numerical model of transmission line equations based on a combination of the finite element method and the generalized method of characteristics. A local system of the transmission line finite element is obtained using the generalized method of characteristics applied to the Telegrapher's equations. In this way, a spatial functional approximation using local shape functions together with the generalized trapezoidal rule used for time integration as it is done in the classical finite element formulation is avoided and higher accuracy of results is obtained. In order to show the essential principles of the proposed numerical method, for sake of simplicity, the scope of the paper is restricted to a single transmission line problem at the low frequency regime.     

Ionospheric radio wave propagation finite element method modeling

In this work, a transionospheric propagation model is presented. The application analyzed here uses data from the Rome ionospheric station together with data from the theoretical IRI-95 and MSIS-E-90 models, in order to simulate the ionosphere. Using formulas from ionospheric propagation theory, these data form the wave equation, which is solved by means of the finite element method. Post-processing of the solution leads to the determination of the main wave propagation parameters.     

埋藏式压力钢管受外压失稳屈曲分析的半解析有限元法

埋藏式压力钢管受外压失稳屈曲的分析 ,采用半解析有限元法 ,即周向采用离散柱壳有限条元法。该方法的柱壳有限条元弧长是可变的 ,从而模拟失稳屈曲波形变化的状态。理论分析及实验研究都告诉我们 ,该理论具有精度高、计算结果合理 ,有广泛的推广应用价值。     

Analysis of short circuit and inrush transients in a current transformer using a field-circuit coupled FE formulation

The existing models based on the lumped-circuit approach consider the constant leakage inductance during transient simulations. However, leakage inductance of the current transformer (CT) may not remain constant. In fact, it may vary with the degree of saturation of the core. During severe saturation conditions, leakage inductance variation in fact may result in significant difference between the calculated and the measured secondary currents. In this work, a nonlinear, field-circuit coupled finite element model of a current transformer (CT) is presented. The model considers the variation in leakage inductance during the simulation of transient conditions. Moreover, since geometry of the transformer was taken into account, it was possible to estimate forces associated with the short-circuit current. Hysteresis characteristic of the core was taken into account by using Jiles-Atherton model in conjunction with fixed-point iteration method. The formulation was realized using a code developed in MATLAB and implemented for a 69 kV, 200/5 A current transformer. The normal operation and other cases such as short-circuit, and transformer sympathetic inrush current through the primary of the CT are presented. These cases demonstrate modeling flexibility of the field-circuit coupled formulation.     

倒梯形对称双脊波导传输特性的有限元分析

为了研究倒梯形对称双脊波导脊的结构参数变化对传输特性的影响,在MATLAB环境下应用有限元工具箱PDE进行二次编程,计算了倒梯形对称双脊波导在TE模式下的截止波长和单模带宽,分析研究了倒梯形对称双脊波导截止波长和单模带宽随结构参数的变化。数值结果表明,与相同条件下矩形、梯形脊波导比较,倒梯形脊波导的单模带宽较宽,截止波长最大。     

离散单元法的饱和/非饱和渗流模型及其实验验证

本文基于时步显式迭代的方法，提出了离散单元法的饱和／非饱和渗流模型，使裂隙岩体中的渗透效应直接参与离散单元法的显式平衡迭代，而无需求解大规模的渗透方程组。利用该模型对饱和／非饱和裂隙网络实验进行了数值模拟，其饱和区和非饱和区的渗透荷载分布与实测结果有很好的一致性。本文提出的模型具备应用于暴雨入渗条件下岩质边坡的变形和稳定分析的重要前景。     

干涉对复合材料疲劳寿命影响的研究

通过拉-拉疲劳试验与理论分析,研究了间隙配合与干涉配合两种不同连接形式对机械连接复合材料接头疲劳寿命的影响,以及不同干涉量对干涉配合复合材料接头疲劳寿命的影响。研究结果表明:复合材料干涉配合接头的疲劳寿命远远高于间隙配合接头的疲劳寿命;干涉量对复合材料干涉配合接头的疲劳寿命有较大影响,所研究的干涉配合模型的最佳干涉量为1%~1.4%。     

Study on Plasticity Modification for Measuring High Residual Stress by Hole-Drilling Method

Hole-drilling method is a commonly used method for measuring residual stress. The calibration coefficients in ASTM E837-13a would cause large errors due to the plasticity deformation of materials. In the study, calibration coefficients were modified in the plasticity deformation stage based on the distortion energy theory. The calibration experiment of calibration coefficients was simulated by the finite element model, and the plasticity modification formulas of 7075 aluminum alloy were obtained. From the results of uniaxial tensile loading test, the measuring errors of high residual stress are significantly reduced from -4.071% ~ 53.440% to -5.140% ~ 0.609% after the plasticity modification. This work provides an effective way to expand the application of hole-drilling method.