Visual representation of the kinematics of the continuum

The purpose of this paper is to present some experimentally determined properties of the continuum. The development starts with the illustration of deformed shapes, or metamorphoses, and the introduction of the concept of displacement. From there on, the development follows the classic mechanics-of-continuum presentation, spatial and time derivatives of displacement, strains, stresses and rigid rotations. To unify the presentation, all considerations are applied to the case of a circular ring subjected to diametral compression. Particular advantage is taken of grids, moiré, brittle-coatings and photoelasticity methods to obtain the physical representations of the properties. The following loci are considered: isokinetics, isothetics, isogonics, isoclinics of displacement, displacement trajectories, loci of partial derivative, isogyros, isotenics, isochromatics, isoclinics of strain and stress, isostatics, isopachics, isobars, isostrophics and isoentatics. The understanding of the properties of these fields helps in the visualization of the mechanics of the continuum, in general, and may prove to be particularly useful in the fields of plasticity and finite strain.     

轴向运动弦线的纵向振动及其控制

综述轴向运动弦线纵向振动及其控制问题的研究进展.多种工程 系统如动力传送带、磁带、纸带、纺织纤维、带锯、空中缆车索道等均 涉及轴向运动弦线的纵向振动.对线性模型而言,除早期结果外,总结了 运动弦线的模态分析、具有复杂约束和耦合的运动弦线振动和运动弦线 参数振动的近期研究.对非线性模型而言,提出了轴向运动弦线大幅纵向 振动的运动微分方程,概述了离散化和直接近似解析分析、用黏弹性材 料模型化阻尼机制和动力传输系统的耦合振动研究的新进展.讨论了轴 向运动弦线振动主动控制的研究现状,包括能控性和能观性,控制分析的 频域方法和能量方法,振动的自适应控制和非线性振动的控制.最后指出 该研究方向今后需要研究的若干重要问题,包括运动弦线的非线性动力学 行为、黏弹性运动弦线的振动、含运动弦线的混杂系统的控制和轴向运 动弦线非线性振动的控制.     

Problems of dynamic fracture mechanics without contact of the crack faces

Conclusion In this, the first part of the survey we have discussed only certain aspects of dynamic fracture mechanics. The surveyed material has been selected with a preference for the most highly developed parts of the theory, specifically those elements which have direct bearing on the second part of the survey. We have also included information on the dynamic fracture mechanics of initially stressed materials, in the development of which one of the authors has been a major contributor.Since many problems of dynamic fracture mechanics have been overlooked in the survey, we have added supplementary references to the literature. Various aspects of the strength and fracture of materials under dynamic loading are set forth in [11, 12, 40, 57, 60, 73, 80, 83]. Criteria of the initiation, motion, branching, and arrest of cracks are discussed in [7, 9, 60, 102, 111, 113, 124]. Among the most interesting elements of dynamic fracture mechanics are the problems of crack propagation. Certain analytical results pertinent to this topic have been obtained in [43–45, 47, 67–72, 78, 87, 92, 96, 97].S. P. Timoshenko Institute of Mechanics, National Academy of Sciences of Ukraine, Kiev. Highway Engineering University, Kharkov. Translated from Prikladnaya Mekhanika, Vol. 30, No. 10, pp. 3–28, October, 1994.     

区域稳定动力学研究(一)——理论与方法体系

将区域稳定工程地质学推进到区域稳定动力学的研究层次上, 系统地构建了区域表层稳定动力学、区域浅层稳定动力学、区域深层稳定动力学、区域活动构造动力学、区域地震动力学、区域非稳定动力学过程及机制模式, 以及区域非稳定动力学环境下的地震工程效应、岩体失稳效应、场地失稳效应及建筑物抗断效应的综合研究及分析评价的区域稳定动力学研究的理论体系与方法体系。     

Masonry structures made of monolithic blocks with an application to spiral stairs

The broad topic of the present work is Statics and Kinematics of masonry structures, made of monolithic blocks, modelled a la Heyman, that is rigid bodies loaded by external forces, submitted to unilateral constraints, and undergoing small displacements, under the simplifying assumption that sliding on rough interfaces is prevented. Specifically, in this work, we study the effect, in terms of internal forces, of specified loads, by using given settlements/eigenstrains to trigger special regimes of the internal forces. Although our scope here is the analysis of masonry structures composed by monolithic pieces, and whose blocks are not likely to break at their inside, the method we propose can also be applied to generic masonry structures, such as those made of bricks or small stones. Heyman’s assumptions translate, for unilateral continua, into a normality assumption which allows to employ the two theorems of Limit Analysis. These continuous structures may actually fracture everywhere at their inside, forming rigid blocks in relative displacement among each other. Such piecewise rigid-body displacements in masonry are physiological, and rather than the result of over-loading, are most likely the direct product of small changes of the displacement type boundary conditions. However, when in a part of the structure a specific piecewise rigid-body displacement nucleates, that part of the structure exhibits a one degree of freedom mechanism, and becomes statically determined. Therefore, the internal forces can be computed, despite the original uncracked structure being abundantly overdetermined, and then admitting infinite many statically admissible stress regimes. With these assumptions, in the present paper we study the equilibrium and the effect of settlements in a masonry structure made of monolithic blocks. In particular, the triple helical stair of the convent of San Domingos de Bonaval, located in the Bonaval district of Santiago de Compostela, is considered as case study.     

温压炸药的特性及发展现状

温压炸药的爆炸涉及到起爆、爆轰、冲击波的传播与反射、多相湍流和多模化学反应等, 是一个多尺度、多物质、多因素、多物理场耦合过程, 深化温压炸药高效释能的关键基础理论, 揭示温压爆炸的反应机理并有效控制和利用是温压武器创新发展的关键科学问题, 对高威力温压炸药的配方设计、温压武器的研制和使用具有重要指导意义. 本文描述了温压爆炸的基本原理, 讨论了温压炸药的概念和内涵, 从炸药种类、释能特点、能量构成、爆炸反应机制、爆炸效应增强机理、杀伤机制等方面阐述了温压炸药的特征, 分析了温压炸药有限空间内部爆炸威力的评估方法以及温压炸药的研发状况, 并提出了相关发展建议, 以期为高威力温压炸药的设计、温压弹的研制及毁伤评估提供指导.      

人体腰椎生物力学的某些基本问题

本文就人体腰段脊柱生物力学的某些基本问题的研究现状与进展进行述评。介绍了腰椎各组成部分包括椎体、椎间盘、椎弓、韧带以及脊髓的力学性能,对其运动学和运动力学进行了讨论,最后就腰椎的力学模型主要是有限元模型的研究作了简单的回顾。      

Theory of acoustoelasticity of rayleigh surface waves

Institute of Electric Welding, Academy of Sciences of the Ukrainian SSR, Kiev. Institute of Mechanics, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Prikladnaya Mekhanika, Vol. 26, No. 4, pp. 35–41, April, 1990.     

折纸及其折痕设计研究综述

折纸是指不经剪裁和粘接,将二维平面纸张折叠成三维立体的方法,具有设计简单、成形迅速、适用范围广等优点,在可展开式结构、结构组装与自成型等领域有着广阔的应用前景. 本文首先简述了多种典型的新式折纸应用,如屈曲诱导的微尺度三维结构、可折叠太阳能电池板、DNA螺旋组装结构等;根据折纸的曲线折痕数量、相对运动、刚性折叠面、使用纸张数量界定折纸的分类;然后 折痕设计是实现折纸结构的核心问题,着重阐述了折纸的折痕设计方面,包括梳理折痕设计的基本条件,给出若干典型折痕设计如三浦折痕设计、水弹折痕设计、吉村式折痕设计和对角线型折痕设计,介绍典型折痕设计的显著特点及几何条件,将目前折纸折痕设计的创新方法归纳为对经典折痕设计适当改进、形成折痕设计数据库、利用拓扑优化方法、借助成型的汇编算法等;最后,基于当前折纸的研究进展对未来的研究方向进行了展望,其中涉及到可重构折纸结构、四维折纸、多材料折纸和多尺度折纸等.      

Mechanics of composite materials with distorted structure (review). continuum theory,fiber composites

Conclusions Investigations of the mechanics of composite materials with structural distortion within the framework of the continuum approach and within the framework of the model of a piecewise-homogeneous body for fibrous composite materials have been reviewed in the present work. On the basis of this review, these investigations must be regarded as in their early stages, In our view, the next stages in this work are to investigate the characteristic static and dynamic problems within the framework of continuum theory [10, 21, 23] and to investigate the stress-strain state in fibrous composite materials with structural distortion taking account of the mutual influence of the fibers.Institute of Mathematics and Mechanics, Academy of Sciences of the Azerbaidzhan SSR, Baku. Institute of Mechanics, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Prikladnaya Mekhanika, Vol. 27, No, 5, pp. 3–20, May, 1991.     

In Memory of Our Honorary Editor-in-Chief Editorial Board of Applied Mathematics and Mechanics

Chien Wei-zang,one of the founders of modern mechanics in China,a world renowned scientist,educator,outstanding social leader,prominent leader of the Chinese Democratic League and a close friend of the Communist Party of China,the Vice Chairman of the 6th,7th,8th,and 9th National Committee of Chinese People's Political Consultative Conference, the Vice Chairman of the 5th, 6th, and 7th Central Committee of Chinese Democratic League, the Honorary Chairman of the 7th, 8th, and 9th Central Committee of Chinese Democratic League, a senior member of Chinese Academy of Science, the President of Shanghai University, the Director of Shanghai Institute of Applied Mathematics and Mechanics, and the Honorary Editor-in Chief of Applied Mathematics and Mechanics, Passed away at the age of 98 in Shanghai at 6:20 AM on July 30,2010.     

Stress-deformation state of thick shells and plates. Three-dimensional theory (review)

Conclusions In the first part of the present review we surveyed systematically published results of investigations of the stress-deformation state of thick-walled spheres, ellipsoids, cones, circular cylinders, as well as thick slabs, obtained by exact analytic solutions of spatial problems of elasticity theory. Several quantitative results were given of the variation of displacements and stresses with shell or plate thickness, and their comparative analysis was provided, making it possible to establish the validity limits of the corresponding applied theories. We also surveyed systematically published specific results of the spatial stress-deformation state of nearly canonical thick-walled shells, as well as non-thin plates of varying thickness, obtained by effective approximate analytic methods and known exact solutions for the corresponding canonical regions. Especially noted were characteristic mechanical (including boundary) effects on the stress-deformation state of the bodies under consideration. These effects are generated, in particular, by variations in the radius of curvature of the surface, the thickness parameter, the amplitude and frequency of the corrugated surface, material, inhomogeneity, conditions of mechanical contact between layers, the nature of self-balancing loads, and other factors.However, the possibilities of exact and effective approximate analytic solution of boundary value problems of this class in the three dimensional statement are restricted. In the case of shells and plates of mean thickness these results can be substantially supplemented by qualitative and quantitative data, obtained on the basis of analytic solutions in the generalized theory of shells and plates, based on expansions of components of the stress-deformation state in Legendre polynomial series, and making it possible, in principle, to approximate the three-dimensional solution with any required accuracy. This is one of the basic features distinguishing it from the classical and applied theories of shells and plates. The second part of this review will be devoted to systematic and comparative analysis of the results of investigations carried out within the generalized theory of non-thin shells and plates.Institute of Mechanics, Ukrainian Academy of Sciences, Kiev. Translated from Prikladnaya Mekhanika, Vol. 27, No. 11, pp. 3–27, November, 1991.     

Investigation of the one-dimensional motion of a snow avalanche along a flat slope

In view of the developing construction in mountainous regions where there is danger from avalanches, the problem of protection against avalanches has become timely. In the solution of this problem, various methods can be used in practice; in connection with the use of these methods, there arise a great number of engineering and mechanical problems. In particular, in the design of structures for protection against avalanches, information is needed on the parameters of moving avalanches, i.e., on velocities, heights of the front, densities of the snow, etc., that is to say, calculations of the motion of avalanches along a slope, as well as of their interaction with the structure under consideration. From a practical point of view, information on the maximal range of the throw, i.e., on the boundary of the avalanche danger zone, is also important. The present article is devoted to an analytical and numerical investigation of the one-dimensional motion of an avalanche; an asymptotic solution is obtained to the problem of the one-dimensional motion of an avalanche along a homogeneous slope.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 5, pp. 7–14, September–October, 1973.     

Applied model of the deformation of nonlinearly viscoelastic vibration insulators subject to cyclic deformation

S. P. Timoshenko Institute of Mechanics, National Academy of Sciences of Ukraine, Kiev. Institute of Geotechnical Mechanics, National Academy of Sciences of Ukraine, Dnepropetrovsk. Translated from Prikladnaya Mekhanika, Vol. 30, No. 9, pp. 63–68, September, 1994.     

Nonlinear Dynamical Systems in Speech Perception and Production

Research examining the nonlinear, dynamical-systems aspects of speech production and perception is reviewed. Examples are provided from studies of phonation, speech respiration, vocal tract acoustics, speech gestures, and auditory-phonetic perception. Results support a conclusion that nonlinear, dynamical system behaviors and principles are represented in speech production and perception at several levels of system behavior. The results are interpreted as suggesting that the communicative distinctions in speech are represented in task-relevant, order parameters which are preserved over a wide range of sets of task-irrelevant, control parameters. The control parameters, in turn, define the domains of behavior for each of the relevant acoustic, biological, or psychological systems. More specifically, it is proposed that speech order parameters may be understood in terms of collective variables defined, in production, over the degrees of, and opening/closing rates of, the vocal tract and, in perception, over the rates, amounts, and relative phases of the broad-band temporal modulations in speech signals.     

On the relations governing rayleigh wave propagation in bodies with initial stresses

Institute of Mechanics, Academy of Sciences of the Ukraine, Kiev. Institute of Electrowelding, Academy of Sciences of the Ukraine, Kiev. Translated from Prikladnaya Mekhanika, Vol. 29, No. 11, pp. 47–52, November, 1993.     

岩体结构要素分形几何研究

本文研究了岩体结构诸要素, 包括结构面形态、结构面厚度、结构面分布、产状分布、孔隙分布颗粒表面形态等的分形表征, 目的是提高岩体结构的定量描述程度, 为岩体工程的定量评价提供新的途径。     

Calculation of the explosion of a trotyl bar of infinite length

The dynamics of the explosion of spherical, cylindrical, or flat charges of explosive has been thoroughly studied [1–6]. The form of these charges is such that the energy evolved is distributed under the condition of the instantaneous character of the detonation or of its initiation at the center, along the axis, or at the plane of symmetry of the charge, uniformly over the surface of the charges, which, with an explosion in a homogeneous medium, leads to one-dimensional not fully established motions. It is of interest to investigate the process of the explosion of charges of more general form, where the above distribution of energy ceases to be uniform, and the corresponding motion of the medium ceases to be one-dimensional. An example can be the explosions of charges having the form of a cube, a parallelepiped, an ellipsoid, etc. The study of such cases makes it possible to clarify the resulting redistribution of the energy of the explosion, which can be of importance from the point of view of the search for possibilities of improving the use and the control of this energy. Such investigations have been carried out experimentally (see, for example, [7]); however, up to the present time there has been no rigorous theoretical analysis, which is connected with the great complexity of the corresponding gasdynamic problems. The article discusses the natural generalization of the problem of the explosion of an infinitely long cylindrical charge.     

Wave flows in a thin layer of a viscous liquid. Influence of a constant electric field

The influence of a constant transverse electric field on the dynamics of longwave, weakly nonlinear flow of a viscous dielectric liquid film down a vertical wall is studied. An amplitude integrodifferential equation in partial derivatives of the Kuramoto-Sivashinskii equation type, which describes the behavior of the free surface of the layer, is derived using the method of multiscale stretching. In the case considered, the potential energy of the electric field is a source of longwave perturbations, but, on the whole, secondary regimes are apparently nonlinearly steady. Probably, the electric polarization effects studied can be used as a factor that governs the dynamics of film flow. Computer Center, Siberian Division, Russian Academy of Sciences, Krasnoyarsk 660036. Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 39, No. 1, pp. 90–97, January–February, 1998.