一种岩石损伤本构模型在地下强爆炸中的应用

为了描述地下爆炸波的传播,建立了一种考虑塑性硬化、剪胀和损伤软化效应的岩石本构模型,并应用于地下强爆炸自由场的数值计算,获得的速度和位移波形以及峰值速度衰减曲线等与国外地下试验测量数据和同类计算相比十分接近,从而验证了本构模型的有效性。     

水饱和岩石中爆炸应力波传播的数值模拟

基于连续介质力学和不相融混合物理论,假定组分间无相对运动,采用B-W-N-B有效应力准则,在屈服面中引入孔隙影响因子,提出了一种多孔含水介质流固耦合的本构模型,并给出了孔隙的演化方程,对水饱和凝灰岩介质中的爆炸应力波传播作了数值模拟。数值计算给出的应力波形与实测结果有良好的一致性。采用本文中所述流固耦合本构模型,可很好地预测水饱和岩石中爆炸波的演化规律。     

饱和土中爆炸波传播问题的数值模拟

应用流体弹塑性力学的框架描述了爆炸荷载作用下饱和土介质的本构模型,包括体积压缩关系和强度关系。应用LS-dyna软件分析了三相饱和土介质中的爆炸波传播及其与结构的相互作用问题,并与先前完成的试验结果进行了对比,两者吻合较好。饱和土中爆炸波传播的一些特殊现象被重现,表明本构模型的描述是可行的。     

土中爆炸波与地下结构相互作用计算方法研究综述

土中爆炸波与结构相互作用是地下工程结构抗爆计算的理论基础,理论研究中通常在宏观试验基础上,引入合理的介质动力本构模型分析波动问题。针对工程防护中的计算模型和解析方法,综述了岩土介质中爆炸波与结构相互作用的现状和研究进展,内容包括土的动力本构模型,自由场中爆炸波的传播、爆炸波与箱型、圆柱形和直墙圆拱型等地下结构的相互作用等。重点阐述了常用的非饱和土和饱和土的动力本构模型、考虑松弛效应的土的综合弹塑性模型,一维平面波在不均匀介质和分层介质中的传播及地下结构爆炸荷载计算方面的研究成果,分析了各种模型和计算方法的适用范围和存在问题。     

爆炸波作用下三相饱和土本构研究

基于对爆炸荷载作用下三相饱和土宏观试验现象的综述，并结合以往对饱和土中气体运动规律的分析，对一维爆炸波作用下三相饱和土本构关系进行了描述。     

混凝土中爆炸应力波衰减规律的数值模拟研究

基于Kong-Fang混凝土材料模型和LS-DYNA的多物质ALE算法,开展混凝土中爆炸波衰减规律的数值模拟研究。首先,基于已有实验数据对材料模型参数和数值算法的可靠性进行了验证,在此基础上分析球形装药在混凝土自由场中爆炸波衰减规律,利用量纲分析和数值模拟拟合了球形装药在混凝土自由场中近区爆炸波峰值应力计算公式并明确其适用范围;然后,分析装药埋深对混凝土中装药正下方不同距离处爆炸波峰值应力分布的影响,建立了耦合系数与装药埋深和测点距离之间的定量关系。结果表明:Kong-Fang混凝土材料模型可实现对混凝土中爆炸波传播衰减规律的高精度数值模拟;定义混凝土中装药质量系数和耦合常数,可定量描述装药埋深和测点距离对峰值应力耦合系数的影响;建立的混凝土中近区爆炸波峰值应力计算公式可较准确地快速预测不同装药埋深、不同测点距离和不同混凝土强度时爆炸波峰值应力。研究结果可为混凝土结构抗爆设计和爆炸毁伤评估提供参考。     

饱和和非饱和介质的弹塑性损伤模型

针对饱和和非饱和工程材料变形和强度特点,给出了一个具体的弹塑性损伤本构方程,该本构方程可以描述材料性质的劣化过程（即损伤和软化）以及饱和程度对材料变形强度特性的影响。此外,还讨论了该弹塑性损伤本构方程的有限元实施方法,编制了专用的有限元程序。对常规三轴试伯进行了有限元分析,得出了一些具体的结果。     

花岗岩介质中地下爆炸震源函数研究

结合地震反演方法和数值计算方法，研究了地下爆炸震源函数的特征以及介质特性对震源函数的影响。从水饱和花岗岩地下爆炸波数值模拟计算出发，重点分析了含水量对震源函数特性的影响。结果表明，含水量会提高地下爆炸的耦合强度，对于震源函数的稳态值，干岩要比水饱和岩石低，且稳态值随含水量的增大而增大；拐角频率随含水量的增大而降低；在水饱和花岗岩中，震源函数的高频衰减指数高于f-2；而过冲特性并不明显。     

形状记忆合金的热力学本构方程

利用形状记忆因子,直观地描述了形状记忆合金(SMA)实现其超弹性与形状记忆效应的热力学宏观过程.根据热力学基本原理并假设SMA为各向同性材料,建立了描述复杂应力状态下SMA热力学行为的三维本构方程.该本构方程具有直观的表述形式且所含材料常数均可以通过宏观实验测定,克服了现存SMA三维本构方程由于表述形式复杂和材料参数不...     

土体的本构模型和超重力物理模拟

数值模拟和物理模拟是分析土体沉降和稳定性的主要手段. 本构模型作为描述土体应力应变关系的数学表达式, 是数值模拟的基础. 土体具有碎散性, 这一基本物理特性导致了其具有压硬性、摩擦性和剪胀性, 这是土的力学特性区别于金属的主要特征, 在土体的本构模型中必须反映这3个基本特性. 传统土力学将土体的变形和强度分离考虑, 分别采用弹性理论和基于刚塑性模型的极限平衡理论分析, 虽然应用广泛, 但由于不能全面地反映土的基本力学特性, 计算结果的精度常常难以满足定量分析的需要. 剑桥模型作为第一个全面反映压硬性、摩擦性和剪胀性的弹塑性本构模型, 实现了变形和强度的统一, 能较好地描述饱和正常固结黏土的应力应变关系, 被视为是现代土力学的开端; 统一硬化模型通过引入一个独特的硬化参数进一步发展了剑桥模型, 将适用范围扩大到超固结黏土. 作者认为, 未来岩土体本构模型研究的挑战是: 如何考虑岩土体在受力过程中土骨架相变与多场耦合, 以解决目前本构模型尚无法定量分析的能源、交通、环境和水利相关的重大岩土工程问题. 超重力物理模拟具有缩尺效应和缩时效应, 克服了常重力物理模拟中模型的应力水平低于原型的缺点, 特别适用于大尺度、长历时问题的模拟. 相较数值模拟, 超重力物理模拟的优势在于能够检验本构模型的合理性, 揭示本构模型无法描述的未知特性. 最后, 介绍了采用数值模拟和物理模拟联合分析大直径钢管桩水平受荷特性的工程案例.      

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.     

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.     

Impact non-pénétrant sur le thorax : influence de la courbure sur la propagation des ondesNonpenetrating impact on the thorax: influence of curvature on wave propagation

Theoretical studies of the propagation of impact waves through the thorax are needed to improve the design of bulletproof jackets and blast protections (Fung in ‘Biomechanics Motions, Flow, Stress, and Growth’, Springer-Verlag, 1990; Cooper et al., J. Trauma 40 (1996) S38–S41). The influence of the weak acoustic coupling at the interface between the thoracic wall and the lung were described in (Grimal et al., C. R. Acad. Sci. IIB 329 (2001) 655–662); in this work, we study, within the frame of elastodynamics and with an approximate analytical method, the effects of the curvature of this interface. Results are given in terms of strain energy for the pressure wave, transmitted or converted. Focalisation of energy in the medium representing the lung is important for curvatures measured in humans. To cite this article: Q. Grimal et al., C. R. Mecanique 330 (2002) 569–574.     

Vérification expérimentale de la relation de réciprocité d'Onsager pour l'électro-osmose et l'électro-filtration dans une argile naturelleExperimental verification of the Onsager's reciprocal relations for electro-osmosis and electro-filtration phenomena on a saturated clay

This Note is devoted to the experimental verification of the Onsager's reciprocal relations in the particular case of electro-osmosis and electro-filtration. A special set up has been designed to carry out the measurements of both the electro-osmotic permeability and the streaming potential. This has been performed by using a natural material i.e., saturated kaolinite. To cite this article: K. Beddiar et al., C. R. Mecanique 330 (2002) 893–898.