超级有限元法及其在结构工程中的应用

本文探讨一种基于半连续半离散思想，适用于复杂结构（如高层框架、剪力墙、桁架、网架等结构系统）工程分析的超级有限元，其结构数值分析是按连续体进行，但又按单个构件进行有限元计算。这种按整体系统进行离散所获得的单元内部包含众多构件，有别于一般常见的实体有限元，称为“超级有限元”。这种方法自由度数比一般有限元法少很多，又与单元内部所含构件数多少无关，并可求取结构内每个构件的内力值。     

平板网架结构分析的超级有限元法

本文给出一种二维矩形超级单元，用以分析平板网架结构、其做法是将大型平板网架结构离散成一系列矩形超级单元，考虑弯曲，剪切、挤压、拉压、翘曲等多种非经典变形效应，采用构件自由度向超级元自由度的转换把大型多构件问题的求解变为二维问题的求解，可大大减少未知量，又能保证精度，并可方便地与一般有限元软件连接。     

平板网架结构分析的超级有限元法

本文给出一种二维矩形超级单元，用以分析平板网架结构，其做法是将大型平板网架结构离散成一系列矩形超级单元，考虑弯曲、剪切、挤压、拉压、翘曲等多种非经典变形效应，采用构件自由度向超级元自由度的转换把大型多构件问题的求解变为二维问题的求解，可大大减少未知量，又能保证精度，并可方便地与一般有限元软件连接。     

空间框架建筑结构静力分析的超级元法解

本文发展一种建筑结构简化计算的新方法，这种方法的整体结构分析按其连续化分单元（超级元）进行，但单个构件又按常规有限元计算，故应用于复杂的空间框架结构提供了一种自由度及工作量极少又适用性强的高效实用分析方法，可望在微机上实现。     

沿板平面材料梯度变化功能材料板件分析

本文发展一种功能梯度构件分析的细观元法.细观元法在构件的常规有限元内部设置密集观细单元以反映材料特性变化,又通过协调条件将各细观元结点自由度转换为同一常规有限元自由度,再上机计算.这种细观元法既能充分反映材料功能梯度沿各方向任意变化特性;而其计算单元又和常规有限元一样,是一种针对功能梯度结构分析的有效数值方法.现有功能梯度板件分析中无论对不同形状还是不同边界的功能梯度构件,其材料特性均沿板厚度方向梯度变化,本文用细观元法进行计算与分析,给出了目前尚未得到的沿板平面方向功能梯度变化构件的力学量三维分布形态.     

功能梯度材料构件三维分析的细观元模型

提出一种新颖的功能梯度构件分析的细观元法,给出了方法模型、基本算式及特点与功能。细观元法对构件的常规有限单元内部设置密集细观单元以反映材料特性梯度变化,又通过协调条件将各细观元结点自由度转换为同一常规有限元自由度,再上机计算。这种细观元法既能充分反映材料功能梯度及组分变化特性,而其计算单元与自由度又与常规有限元一样,是一种针对功能梯度构件分析的有效数值方法。算例表明了细观元法对不同情况下功能梯度构件分析的适应性与精度。     

超级有限元法在桁架组合结构分析中的应用

本文针对复杂杆系组合结构静动力问题讨论一种简捷有效的数值计算方法——超级有限元法,首先介绍其一般原理,继而针对一大类复杂桁架空间杆系组合结构准三维化处理(用一维变量加以表征),并将其离散成一系列单元,考虑弯曲、剪切、挤压、拉伸压缩、扭转等多种非经典变形效应,通过采用构件端部自由度向超级元自由度的转换而把复杂多构件问题的求解变为少量一维结点变量问题的求解,既达到了简化的目的,又保证了精度,而且可方便地与通常的有限元法结合使用。文中还给出了有关杆系组合结构分析的数值算例。     

有限元分析中的信息处理——单元延拓里兹法

有限元分析给出连续场在若干离散点(网格结点)的信息(例如平面应力板的位移)。如何利用这些离散点信息获得全场信息的连续分布(变形曲面)和进一步推算其它性态信息(应力),一般采用分片插值和分片拟合方法。本文提出了单元延拓里兹法,并将其应用于有限元分析中的信息处理。因利用了单元邻近区域的信息来处理单元内部的信息,从而提高了精度;利用较粗的网格作有限元分析,又节约了计算时间。     

大跨板片空间结构的超级有限元分析

板片空间结构是一种新型的结构体系，它是以一系列小板为基本构件，通过适当组合形成的具有空间受力性能的结构形式。本文在对这类结构有限元分析的基础上，应用超级元分析的基本思想，对这类结构进行了分析，给出了这类结构超级元分析方法的基本公式。算例分析结果表明：与一般有限元法相比，超级元法大大节省了计算量，结点自由度下降了二个数量级，且分析结果和有限元法基本吻合，为这类大跨空间结构应用微机分析提供了一个新的方法。     

大跨板片空间结构的超级有限元分析

板片空间结构是一种新型的结构体系，它是以一系列小板为基本构件，通过适当组合形成的具有空间受力性能的结构形式。本文在对这类结构有限元分析的基础上，应用超级元分析的基本思想，对这类结构进行了分析，给出了这类结构超级元分析方法的基本公式。算例分析结果表明：与一般有限元法相比，超级元法大大节省了计算量，结点自由度下降了二个数量级，且分析结果和有限元法基本吻合，为这类大跨空间结构应用微机分析提供了一个新的方     

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.