上覆单相弹性层的饱和地基上刚性圆板的扭转振动分析

采用解析的方法研究了上覆单相弹层的饱和地基上刚性圆板的扭转振动。首先运用积分变换技术分别求解了单相弹性介质和饱和介质情况时的控制方程，然后按混合边值条件建立了上覆单相弹性层的饱和地基上刚性圆板扭转振动的对偶积分方程，并把对偶积分方程化为易于数值求解的第二类Fredholm积分方程，并给出了数值算例。     

电磁共振腔辛有限元法

将电磁场的基本方程导向了对偶方程形式。给出了推导电磁场有限元所需相应的对偶变量变分原理。为了有限元列式的保辛，交分原理被积函数可导向对于对偶变量为对称的形式。交分原理的边界积分项对于相邻单元互相抵消。对偶变量有限元推导可避免所谓的C1连续性问题。采用对偶变量离散分析了共振腔本征值问题，离散后再消去一类变量可导出普通的广义本征值问题而求解。算例表明了对偶变量有限元分析的有效性。     

四边形等参单元温度场有限元分析中的混合边界条件

在温度场有限元分析中，边界条件的合理确定是一个非常重要的问题。本文以四边形等参单元为基本单元，采用基于微分方程等效积分原理的Galerkin加权余量法，建立了热传导问题的有限元方程，推导出混合边界条件的有限元计算公式。最后，根据求得的温度场可得截面温度应力分布。     

三维电磁场辛有限元列式及电磁共振腔的计算

针对三维共振腔的电磁场分析,利用Maxwell方程的对偶方程体系形式,从其相应的对偶变量变分原理出发,导出了三维电磁场辛有限单元的详细列式。为了有限元列式的保辛,变分原理被积函数可导向对于对偶变量为对称的形式。变分原理的边界积分项对于相邻单元相互抵消。由于采用了对偶变量的插值函数,使得电磁场单元构造可以在层面上进行,从而避免了所谓的连续性问题。无物理意义的零本征解可采用奇异值分解加以排除。文末分别对矩形及圆柱形的共振腔做了数值计算并与解析解和棱边元计算结果进行对比,算例表明了列式及算法的有效性。     

基于对偶变量变分原理的完整约束系统保辛算法

基于对偶变量变分原理,选择积分区间两端位移为独立变量,构造了求解完整约束哈密顿动力系统的高阶保辛算法。首先,利用拉格朗日多项式对作用量中的位移、动量及拉格朗日乘子进行近似;然后,对作用量中不包含约束的积分项采用Gauss积分近似,对作用量中包含约束的积分项采用Lobatto积分近似,从而得到近似作用量;最后,在此近似作用量的基础上,利用对偶变量变分原理,将求解完整约束哈密顿动力系统问题转化为一组非线性方程组的求解。算法具有保辛性和高阶收敛性,能够在位移的插值点处高精度地满足完整约束。算法的收敛阶数及数值性质通过数值算例验证。     

二维Nonlocal线弹性理论的变分原理与对偶方程

基于Eringen提出的Nonlocal线弹性理论的微分形式本构关系,导出了相应的能量密度表达式,进而得到二维Nonlocal线弹性理论的变分原理.利用变分原理导出了对偶平衡方程和相应的边界条件.进而给出了非局部动力问题的Lagrange函数,并引入对偶变量和Hamilton函数,得到了对偶体系下的变分方程.在Hamilton体系下,通过变分得到了二维Nonlocal线弹性理论的对偶平衡方程和相应的边界条件.     

电磁波导的奇异元与对偶有限元分析

基于电磁波导的对偶变量变分原理以及Hamilton正则方程,将含有奇异性的电磁场问题导入Hamilton体系下进行分析,通过分离变量及共轭辛本征函数向量展开法,构造出可以表征电磁场奇异性的奇异解析元。奇异元的采用克服了普通单元处理含有导电劈和介质楔的波导问题的困难,同时能够方便地与电磁对偶元相结合,保持了有限元方法的灵活性,具有较高的精度。     

非均匀弹性材料中反平面的运动裂纹

用解析方法研究了非均匀弹性材料中反平面运动裂纹问题。首先采用余弦变换求解非均匀材料的基本方程，然后根据混合边值条件建立裂纹运动的对偶积分方程，再把对偶积分方程化为第二类Fredholm积分方程。给出了数值算例，计算结果表明材料的非均匀性对动应力强度因子有较大的影响。     

截面含切口圆柱体自由扭转的弹塑性分析

对于截面含切口圆柱体的弹塑性自由扭转问题的分析,可按受力特点分为三个阶段:全弹性阶段、全塑性阶段和弹塑性阶段.每一阶段对应的分析方法不同,其中,在全弹性阶段可以采用有限差分法分析;在全塑性阶段可以按沙堆比拟的方法采用等倾曲面模拟;弹塑性阶段可以结合上述两种方法的结果和思路进行分析.利用差分法可以求出自由扭转截面内各离散点应力函数φ的数值解.本文推导了自由扭转的应力函数φ与J积分之间的关系,得出了自由扭转的应力函数与Ⅲ型裂纹的J积分之间的关系式.数值计算结果验证了本文方法的有效性和精确性.     

柱体扭转若干情形的应力强度因子

本文旨在讨论外裂缝的若干情形的等截而柱体的扭转.Nowacki曾讨论过这些截面,将问题归结为第一类积分方程,但不便于进行数值处理.本文通过对偶级数方程将问题归结为具有连续核的第二类Fredholm积分方程,并且给出抗扭刚度和应力强度因子的表达式.     

The 7th International Conference on Fluid Mechanics May 24-27,2015,Qingdao,China

正http://www.icfm7.org First Announcement and Call for PapersThe objective of International Conference on Fluid Mechanics(ICFM)is to provide a forum for researchers to exchange new ideas and recent advances in the fields of theoretical,experimental,computational Fluid Mechanics as well as interdisciplinary subjects.It was successfully convened by the Chinese Society of Theoretical and Applied Mechanics(CSTAM)in Beijing(1987,     

INFORMATION FOR CONTRIBUTORS

Contributions： The Journal, Acta Mechanica Solida Sinica, is pleased to receive papers from engineers and scientists working in various aspects of solid mechanics. All contributions are subject to critical review prior to acceptance and publication.     

Preface

This special issue of PARTICUOLOGY is devoted to the first UK-China Particle Technology Forum taking place in Leeds, UK, on 1-3 April 2007. The forum was initiated by a number of UK and Chinese leading academics and organised by the University of Leeds in collaboration with Chinese Society of Particuology, Particle Technology Subject Group （PTSG） of the Institution of Chemical Engineers （IChemE）, Particle Characterisation Interest Group （PCIG） of the Royal Society of Chemistry （RSC） and International Fine Particle Research Institute （IFPRI）. The forum was supported financially by the Engineering and Physics Sciences Research Council （EPSRC） of United Kingdom,     

基于鲁棒滤波的捷联导引头视线角速度估计方法

针对捷联导引头无法直接获取视线角速度等信息的问题,研究了鲁棒滤波在大气层外飞行器捷联导引头视线角速度估计中的应用。为了建立非线性滤波估计模型,考虑目标视线角速度的慢变特性,采用一阶马尔科夫模型建立了状态方程;推导了视线角速度的解耦模型,并建立了量测方程;考虑到实际应用中存在系统噪声统计特性失准的问题,基于Huber-Based鲁棒滤波方法,设计了视线角速度滤波器,并完成了基于Huber-Based滤波方法和扩展卡尔曼滤波方法的数学仿真。仿真结果表明Huber-Based滤波方法的视线角、视线角速度及视线角加速度估计精度分别达到0.1140'、0.1423'/s、0.0203'/s2,而扩展卡尔曼滤波方法的视线角、视线角速度及视线角加速度估计精度仅分别为0.6577'、0.6415'/s、0.0979'/s~2。仿真结果证明了该方法可以有效地估计出相对视线角速度等信息,并且在非高斯噪声的条件下,依然可获得较高的估计精度,具有一定的鲁棒性。     

Guide for authors

正Each of the sections below provides essential information for authors.We recommend that you take the time to read them before submitting a contribution to Acta Mechanica Sinica.We hope our guide to authors may help you navigate to the appropriate section.How to prepare a submission This document provides an outline of the editorial process involved in publishing a scientific paper in Acta Mechanica     

Use specification of multiscale materials for life spanned over macro-, micro-, nano-, and pico-scale

Multiscale material intends to enhance the strength and life of mechanical systems by matching the transmitted spatiotemporal energy distribution to the constituents at the different scale, say—macro, micro, nano, and pico,—, depending on the needs. Lower scale entities are, particularly, critical to small size systems. Large structures are less sensitive to microscopic effects. Scale shifting laws will be developed for relating test data from nano-, micro-, and macro-specimens. The benefit of reinforcement at the lower scale constituents needs to be justified at the macroscopic scale. Filling the void and space in regions of high energy density is considered.Material inhomogeneity interacts with specimen size. Their combined effect is non-equilibrium. Energy exchange between the environment and specimen becomes increasingly more significant as the specimen size is reduced. Perturbation of the operational conditions can further aggravate the situation. Scale transitional functions and/or f_j/j+1 are introduced to quantify these characteristics. They are represented, respectively, by , and (f_mi/ma,f_na/mi,f_pi/na). The abbreviations pi, na, mi, and ma refer to pico, nano, micro and macro.Local damage is assumed to initiate at a small scale, grows to a larger scale, and terminate at an even larger scale. The mechanism of energy absorption and dissipation will be introduced to develop a consistent book keeping system. Compaction of mass density for constituents of size 10⁻¹², 10⁻⁹, 10⁻⁶, 10⁻³ m, will be considered. Energy dissipation at all scales must be accounted for. Dissipations at the smaller scale must not only be included but they must abide by the same physical and mathematical interpretation, in order to avoid inconsistencies when making connections with those at the larger scale where dissipations are eminent.Three fundamental Problems I, II, and III are stated. They correspond to the commonly used service conditions. Reference is made to a Representative Tip (RT), the location where energy absorption and dissipation takes place. The RT can be a crack tip or a particle. At the larger size scales, RT can refer to a region. Scale shifting of results from the very small to the very large is needed to identify the benefit of using multiscale materials.