上海市力学会的三十年<1959—1989>

上海市力学会成立于1959年9月,到现在已经历了三十个春秋。三十年来,学会在市科协领导下,在中国力学学会和本市有关高等院校、研究所、设计院、工厂单位的大力支持下,团结广大科技工作者,为普及力学知识、提高水平、发展力学科学、培养力学人才、发挥力学在生产建设与文明建设中的作用,作出了应有的贡献。学会不断得到发展壮大,在庆祝学会成立三十周年之际,缅怀过去、展望未来。     

断裂力学简介

断裂力学是固体力学中研究带裂纹材料强度的一门新学科。它在生产上有着重要的应用价值,受到航空、造船、交通、原子能、火箭、化工、机械以及军工等各工业部门的普遍重视。近年来,它在国内外都发展很快。 材料在生产和加工过程(例如冶炼、锻造、铸造、焊接、热处理)中,不可避免地会产生这样或那样的缺陷和裂纹。同时在使用过程中,由于氢的渗入、中子的照射、腐蚀作用、疲劳作用都会使材料局部劣化或脆化而产生裂纹。因此,在实际构件中,不论是否被探伤仪器所发现,总是客观地存在着缺陷或裂纹。但是在断裂力学出现之前,人们是以“材料是无缺陷的、连续的、均匀的介质”为前提,来计算构件的承载能力,作为设计产品的依     

第二次全国渗流力学学术会议

1982年9月18日至21日在兰州召开了第二次全国渗流力学学术会议。参加会议的有我国石油、水电、地质、冶金、教育和中国科学院等系统以及山西、浙江、安徽、河北、甘肃和天津等省市的38个科研、设计、生产单位和大专院校的67名代表。在会上宣读论文55篇,这些论文有的在应用上意义较好,有的在理论上有所创新,有的在研究方法或计算实验方法和技术上有所创新或改进。报告的论文涉及到国民经济的许多重要方面,诸     

第二次全国渗流力学学术会议

1982年9月18日至21日在兰州召开了第二次全国渗流力学学术会议。参加会议的有我国石油、水电、地质、冶金、教育和中国科学院等系统以及山西、浙江、安徽、河北、甘肃和天津等省市的38个科研、设计、生产单位和大专院校的67名代表。在会上宣读论文55篇,这些论文有的在应用上意义较好,有的在理论上有所创新,有的在研究方法或计算实验方法和技术上有所创新或改进。报告的论文涉及到国民经济的许多重要方面,诸...     

磁敏弹性膜的研制、性能表征及应用研究进展

磁敏弹性膜是一种新型的智能材料,其力学、电学、磁学、声学等性质能够受外加磁场的控制,从而在多个领域展现在广泛的应用前景。本文首先从材料设计、制备工艺、结构设计等方面综述了磁敏弹性膜的研制方法,随后详细阐述了磁敏弹性膜的力学、电磁、声学等性能表征及内部机理,最后介绍了磁敏弹性膜在传感器、执行器、柔性机器人等领域的应用,在上述基础上,展望了磁敏弹性膜的发展,也提出了面临的问题及挑战。     

人椅系统肢体气动特性数值模拟

为了研究弹射过程中人体肢体气动特性和高速气流防护装置的有效性,采用有限体积方法数值求解Navier-Stokes方程,空间和时间离散分别采用中心格式和五步龙格库塔格式,并应用基于SA紊流模型DES方法,数值模拟了人椅系统马赫数在0.6、雷诺数在12.3×106、迎角在-90°～90°范围内的气动特性,计算结果与风洞试验结果较为吻合.在此基础上对比模拟了马赫数在0.8～2.0、雷诺数在(6.75～13.85)×106、迎角在5°～30°范围内,有、无防护下人体肢体的气动特性.结果表明限臂板、抬腿机构和导流挡板等高速气流防护装置在保护肢体的同时,也产生一些不利干扰.因此,在实际应用中,应优化设计,最大程度发挥高速气流防护装置的作用.     

某电站大型地下洞室群主变洞确定性块体稳定性评价

以黄河上游某大型电站地下洞室群主变洞为例,通过在AutoCAD软件中建立洞室与结构面的三维实体模型,借助自编程序切割,展示这些结构面在主变洞边墙及拱顶的出露情况,在此基础上检索出组合块体21个,最后对这21个块体进行了确定性块体稳定性评价,给出其在主变洞上下游边墙及拱顶的块体组合情况、滑动方式、出露桩号和高度、出露面积、分布深度、体积、稳定性系数等。     

定向爆破及其在农田基本建设中的应用(三)

第七章 炸药和起爆器材 在农田基本建设中,利用炸药的爆破作用在开挖土石方、修渠、搬山造田、筑坝等工程中得到了越来越广泛的应用。在大爆破中,炸药的费用在整个工程费用中占很大比例。因此,在计算用药量和生产配制炸药过程时,应当充分注意发挥和利用炸药的爆炸作用。 炸药可分为固体炸药和液体炸药,有的是化合物(如黑索金、梯恩梯等),有的是混合物(如铵油炸药)。在农田基本建设中,常用的炸药品种有铵梯炸药、铵油炸药以及黑火药,其中以硝酸铵(化     

海岸波浪场模型研究进展

从建模原理、波浪在近岸区域传播的众多机制、模型的类别、优势、局限性以及模型在未来的发展趋势等方面,综述了在海岸工程实践中广泛运用的以下两大类海岸波浪场预测模型的最新研究进展:(1)能量平衡模型.它一般用来预测海洋深水波候,已发展到相当完善的阶段,例如,最为著名的WAM3G模型.这种模型在海岸工程中的作用就在于可以模拟施加在波浪上的随时间变化的风场效应.(2)质量、动量守恒模型.它在海岸工程中应用最为普遍,并且内容丰富,数值技巧多样.目前包含了以下代表性的模型:缓坡方程、抛物型方程、非线性浅水方程、高阶Boussinesq型方程、Green-Naghdi理论.      

中国力学学会副理事长季文美简介

季文美教授1912年生于浙江省义乌县。1934年在上海交通大学毕业后,赴意大利学习,在都灵大学航空研究院获博士学位,1937年回国。先后在南昌与南川飞机制造厂任工程师。1942年起,从事高等教育工作。历任上海交通大学教授、航空系主任,华东航空学院及西安航空学院教授、副教务长、副院长,西北工业大学教授、教务长、基本理论研究委员会主任、教学工     

一种考虑界面相物性影响的界面单元法

界面是由复杂的界面相简化而成的,界面破坏实际是界面相材料的破坏。数值计算为了方便,如经典模型和内聚力模型等,都把很薄的界面相作无厚度化处理。导致只能考虑界面的面力,而无法考虑界面相内的应力(平行于界面方向的应力)。使界面失效准则先天性地排除了界面相内部应力的影响,从界面相材料失效机理的角度来看这是不够严谨的。本文将界面相材料等效为一种弹性连续体,由界面本构关系推导得到了一种新的界面单元。该单元具有界面参数易确定、对界面相物性可以进行等效描述等优点。通过商用有限元软件ABAQUS和用户子程序UEL实现了数值分析,并与直接物理模型的数值模拟结果进行对比,证明了本方法的简便及准确性。通过对不同界面相厚度结构的进一步分析,探讨了本文方法的可行范围。     

Interaction of an Ellipsoidal Inclusion with an Elliptic Crack in an Elastic Material under Triaxial Tension

The interaction of an elastic ellipsoidal inclusion with an elliptic crack in an infinite elastic medium under triaxial loading is analyzed. The stress state in the elastic space is represented as a superposition of the principal state and perturbed states, which are due to the presence and interaction of the inclusion and the crack. The analytical solution of the problem is found using the method of equivalent inclusion, the potential of an inhomogeneous ellipsoid, and a system of harmonic functions for an elliptic crack. The effect of triaxial loading on the stress intensity factors is analyzed     

A partially implicit method for simulating viscous aerofoil flows

A partially implicit method for the unsteady compressible Navier-Stokes equations is developed. The method is based on an explicit treatment of streamwise fluxes and an implicit treatment of normal fluxes. This leads to a linear system which is generated by an efficient finite difference procedure and which is block pentadiagonal. The method is tested on a shock-induced oscillatory flow over an aerofoil. Parallel implementations of an explicit, fully implicit and partially implicit method are investigated.     

Non-linear argumental oscillators: Stability criterion and approximate implicit analytic solution

The behaviour of a space-modulated, so-called “argumental” oscillator, is studied. The oscillator is submitted to an external harmonic force, which is amplitude-modulated by the oscillator's position in space. An analytic expression of a stability criterion is given. Using the averaging method, an integrating factor and a Van der Pol representation in the (amplitude, phase)-space, an exact implicit analytic solution is given when there is no damping, and an approximate implicit analytic solution is given when there is damping, allowing the plotting of the separatrix curve. An attractor is identified.     

Experimental Investigation of the Interaction between an Electric Arc and a Gas Flow

The results of investigating the shape of an electric arc carrying an electric current of less than 100 A and exposed to an air, nitrogen, or argon stream at a stream velocity of from zero to 20 m/s, when the interelectrode gap is less than 20 mm, are reported. The shape of the arc is qualitatively investigated as a function of the gas type, blowing velocity, and interelectrode gap. It is shown that an arc burning in a channel with insulated walls is much more stable under these conditions than an arc with the same parameters burning in free space.     

Deformation of an ellipsoidal ferrogel sample in a uniform magnetic field

The elongation of a ferroelastic material sample (whose initial shape is a sphere or an ellipsoid of revolution) under the action of an external magnetic field is studied in an in approximation of small strains. For a sphere, there is a classical estimate obtained under the assumption that elongating in the direction of the field, it becomes a spheroid and the stress and strain fields remain uniform. In the present calculation, it is assumed that the body is an ellipsoid (a sphere in a particular case) only in the absence of an external field; the shape of the sample in the presence of a field is not specified in advance but is found from the condition of balance of surface forces (elastic and magnetic). For the spherical case, the problem is solved exactly: it is shown, that the contour of the deformed body is described by a third-order algebraic equation. The case where the initial configuration is an ellipsoid of revolution is studied numerically. It is shown that in all versions, the refined solution leads to an appreciable increase in the elongation of the sample compared to the classical estimate. __________ Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 46, No. 3, pp. 153–164, May–June, 2005.     

Self-Similar Unsteady Viscous Flow

Four examples of self-similar flows of a viscous fluid are considered: separated flow over an expanding plate immersed in an unbounded unsteady viscous flow, the evolution of the velocity field induced by a vortex-source, the flow near an unsteadily moving permeable flat plate, and the flow near an unsteadily rotating disc. For the first example, a numerical solution is constructed. For the next two examples, an analytical solution is found, while the solution of the last problem is reduced to a system of ordinary differential equations.     

POINCARE-CARTAN INTEGRAL INVARIANTS OF BIRKHOFFIAN SYSTEMS

Based on modern differential geometry, the symplectic structure of a Birkhoffiansystem which is an extension of conservative and nonconservative systems is analyz ed. Anone-dimensional damped vibration is taken as an ilhustrative example and an integralinvariant of Poincaré's type is found.     

可压缩流体的Rayleigh-Taylor和Kelvin-Helmholtz不稳定性

在状态方程为压力是密度的任意单值函数形式情况下，运用小扰动分析和奇异摄动法，给出了流体微扰方程渐近解和界面不稳定性的色散关系. 分析表明：对Rayleigh-Taylor不稳定性，在重力场作用下流体可压缩性形成的密度分布是致稳因素；而扰动流体的膨胀收缩效应助长不稳定性的发展；上层重流体的可压缩性是稳定因素，下层轻流体可压缩性是失稳因素. 而对Kelvin-Helmholtz不稳定性，流体可压缩性助长扰动的发展，是不稳定因素.     

Uniform difference scheme for a singularly perturbed linear 2nd order hyperbolic problem with zeroth order reduced equation

In this paper a singularly perturbed linear second order hyperbolic problem with zeroth order reduced equation is discussed. Firstly, an energy inequality of the solution and an estimate of the remainder term of the asymptotic solution are given. Then an exponentially fitted difference scheme is developed in an equidistant mesh. Finally, uniform convergence in small parameter is proved in the sense of discrete energy norm.