横向磁场中细长压杆的分岔特性

在磁弹性非线性运动方程、物理方程、电动力学方程及洛仑兹力表达式的基础上,应用Lagrange描述法建立了横向磁场中两端铰支受压细长杆的非线性磁弹性动力学模型.通过对该模型的简化,分别讨论了静力学模型、线性动力学模型和含三次非线性项的动力学模型的分岔特性.最后通过数值计算,给出了横向磁场中受压细长杆的失稳临界载荷与相关参量之间的关系曲线,并对计算结果及其变化规律进行了分析讨论.     

MODELING OF NONLINEAR BEHAVIORS OF IMMERSION JOINT

沉管隧道柔性接头的力学性能是其抗震设计的关键准则. 用有限元方法模拟接头的非线性力学性能需要解决接头处材料非线性和接触非线性两个问题. 为简化分析计算,该文采用分段线性化的方法表征接头的材料非线性问题,引进调整因子改进接触算法中的判断条件,处理接头的边界非线性问题. 通过沉管隧道接头的三维精细化建模,研究了沉管隧道接头在拟静力载荷下的响应,获得了接头的轴向等效刚度曲线、抗弯刚度曲线和非线性耦合的剪切特性曲线,进而分析了不同轴向压力对接头剪切特性的影响.     

槽型宽翼受压构件剪力滞分析的传递矩阵法

利用能量变分法,建立了槽型宽翼受压构件考虑剪力滞效应时的平衡控制微分方程,给 出了该方程在轴向均布载荷作用下的初参数解,导出了求解槽型宽翼受压构件内力、应力和 位移的场矩阵和点矩阵,提出一种研究槽型宽翼受压构件剪滞效应的传递矩阵法. 数值算例 表明,该方法计算便捷、精度好、具有较高的工程应用价值.     

K型管节点的应力集中系数研究

采用有限元法分析了K型管节点在承受轴力作用下的应力集中系数. 用三维固体单元模 拟结构,模拟中对不同区域分别划分网格,每个区域的网格独立产生后,再形成整个结构的 有限元网格. 使用ABAQUS软件分析了200组在轴向循环载荷作用下的节点数值模型,获得 了K节点在轴向循环载荷作用下沿焊缝的应力集中系数(SCF),并对主管和支管的SCF进行 研究,得出了节点几何参数对主管和支管的SCF及极值位置的影响规律.     

轴向扩散下简支饱和多孔弹性梁的大挠度分析

基于多孔介质理论和弹性梁的大挠度理论,并考虑轴向变形,在孔隙流体仅沿轴向扩散的假设下,建立了微观不可压饱和多孔弹性梁大挠度弯曲变形的一维非线性数学模型.在此基础上,忽略饱和多孔弹性梁的轴向应变,并利用Galerkin截断法,研究了两端可渗透的简支饱和多孔弹性梁在突加横向均布载荷作用下的拟静态弯曲,给出了饱和多孔梁弯曲时挠度、弯矩和轴力以及孔隙流体压力等效力偶等沿轴线的分布曲线.揭示了大挠度非线性和小挠度线性模型的结果差异,指出大挠度非线性模型的结果小于相应小挠度线性模型的结果,并且这种差异随着载荷的增大而增大.计算表明:当无量纲载荷参数q>5时,应该采用大挠度非线性数学模型进行研究.     

考虑轴向均布载荷时压杆的稳定性计算

为了求得压杆同时承受轴向均布载荷和集中载荷时,临界载荷的计算公式,首先对仅承受轴向均布载荷的压杆,用初参数法,导出了临界载荷特征方程,由软件分析特征方程发现, "固支--定向"、"固支--自由"、"铰支--定向"支承的压杆,轴向均布载荷对其稳定性有明显影响,并求得了临界载荷的近似解;其次采用载荷换算与叠加的方法,求得了压杆同时承受轴向均布载荷和集中载荷时,临界载荷计算的经验公式;最后就"固支--自由"支承的压杆,与其他一些研究结果进行了比较,本文结果与"平均结果"较吻合.     

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根据抗拉刚度等效及抗弯刚度等效将换热器管束简化为当量圆筒以考察其对 斜锥壳应力状况的影响,同时根据轴向载荷等效及泊松效应等效,对作用在管板布管限定圆 内的压力载荷及作用在管束外表面的压力载荷进行了当量转换,建立了考虑管板及管束影响 的斜锥壳应力分析简化模型. 有限元计算结果表明,大端转角过渡区存在较大的弯曲应力. 对一系列结构尺寸的斜锥壳进行了计算,整理了斜锥壳大端转角过渡区基于分析设计的应力 强度水平系数.     

NUMERICAL ANALYSIS OF THE STRESS CONCENTRATION IN REVERSE K-JOINTS

逆K 型管节点广泛应用于海洋平台,其强度是平台结构安全评估的重要课题. 基于ANSYS 软件,应用分区域网格划分法,建立含焊缝的逆K 型管节点有限元模型,分别计算了在轴向载荷、平面内弯矩和平面外弯矩作用下焊缝周围热点应力的分布情况. 通过对105 组逆K 型管节点模型进行分析,获得了其在3 种基本载荷作用下沿焊缝的应力集中系数（stress concentration fctor,SCF）,并对主管和支管的SCF 分别进行研究,得出了几何参数对主管和支管的SCF 及极值位置的影响规律.     

受均布载荷压杆后屈曲形态的数值计算

对受均布载荷压杆的屈曲及后屈曲行为进行了分析.基于杆的大变形理论,考虑杆的轴向伸长,建立了受均布载荷作用下细长压杆的几何非线性平衡方程.采用打靶法和解析延拓法数值求解非线性两点边值问题,得到了杆的后屈曲平衡路径和平衡构形.     

基于模态缺陷的受压球壳屈曲特性研究

针对受压球壳非线性屈曲过程,对含初始缺陷受压球壳的稳定性进行研究。根据EN1993-1-6（2007）规范,给出不同制造等级壳体的等效缺陷值计算方法;基于线性特征值分析的模态构型给出初始缺陷的分布。利用非线性有限元弧长法对球壳受压失稳过程进行数值模拟,得到屈曲前后球壳变形情况及全过程载荷-位移曲线。计算一致缺陷模态法和N阶缺陷模态法对应的球壳屈曲临界载荷,结果表明,受压球壳对缺陷较敏感,承载能力随缺陷值增大而降低;一致缺陷模态法计算便捷,在工程应用上具有合理性,N阶缺陷模态法考虑高阶模态缺陷构型,结果更加全面,可以为工程中缺陷结构稳定性设计提供参考。     

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.