"水立方"中的膜结构——ETFE

简要介绍了``水立方'膜结构的主体材料------ETFE材料的发展、性质及其在建筑 领域中的应用.     

THE "REBEL TRAVELLING" OF GENERAL NONLINEAREVOLUTIONAL EQUATION AND DISCUSSIONON RELATED PROBLEMS

I.IntroductionThere\ersedtransforlllationofevolutionfornlisot'tellobser\.edillnature.forexample.there\'ersedchangeofcon\'ergenceintodid'er~ellcefaithlandingofu hitecap.theuns}'mmetricalbreak-off'ofresilelltmaterialcausedb}'poundingftheelldlessnowofiii'eevolutionalldtheval-iatiollofspecies;tileriseandfilllinecollonlicacti\-ittes,the"collfLlsion"alld'order"illcvolutiollofsociety.etc..Itisoh\-loLlSthattilelinearInodelorcontinuousthinkingpatternispo\verlesstocopewiththesephenonlella.Thetheoryofc…     

基于“兴趣-科研-探索”的船舶与海洋工程流体力学启发式教学模式初探

针对船舶与海洋工程流体力学课程的教学特点,提出一种“兴趣-科研-探索”的启发式教学模式。该教学模式以“兴趣驱动”为牵引,以“科研应用”为抓手,以“探索未知”为导向,最大限度地调动学生的主动学习能力和发散思维潜力。以空泡现象为例,将该模式与船舶与海洋工程流体力学知识点相结合,激发学生对于知识点的好奇和兴趣,加深学生对于知识点的掌握和应用,启发学生对于知识点的理解和想象,旨在为该课程教学探索一种新模式。     

边界膜剪切弹性模量对于微接触性能的影响

建立接触模型,理论分析了微接触中边界膜剪切弹性模量对于接触性能的影响. 接触区由两平行平面形成,属一维接触. 上接触表面为粗糙表面,具有矩形微凸体. 下接触表面为光滑平面. 两接触表面均处理成刚性表面. 微接触区中充满流体. 它分成两个子区,在微接触的出口区由于极小的接触间隙充满边界膜,在微接触的入口区由于接触间隙较大充满流体膜. 边界膜和流体膜行为决定整个微接触性能. 当膜厚较大时,这里边界膜可看成纳米级薄膜. 由于上接触表面处有限的剪应力承受能力,边界膜可于上接触表面滑移. 设下接触表面处剪应力承受能力很大而边界膜在下接触表面不滑移. 由于边界膜-接触表面间相互作用,边界膜黏度、密度和剪切弹性模量均沿膜厚变化,在理论分析中使用它们的等效值,这些值与边界膜厚度有关. 流体膜在两个接触表面均不发生滑移,分析中不考虑流体膜剪切弹性模量. 流体膜采用传统分析法. 给出了理论分析和若干变工况参数下的计算结果.      

DESIGN SCHEME BY THE CHAMPION TEAM OF THE "THEORETICAL DESIGN AND OPERATION" OF THE 11th NATIONAL ZHOU PEIYUAN COMPETITION ON MECHANICS FOR COLLEGE STUDENTS OF CHINA

本文主要介绍了清华大学代表队在第十一届全国周培源大学生力学竞赛"理论设计与操作"团体赛中的解题思路、操作过程和设计方案,简要总结了此次参赛的经验和教训。     

考虑膜厚影响薄膜磁致伸缩系数、泊松比和杨氏模量的同时测量

基于经典层合板理论,建立了一个能同时测量薄膜-基底系统中薄膜的磁致伸缩系数、杨氏模量和泊松比的板模型.以前的研究计算薄膜磁致伸缩系数时,大多假设薄膜的弹性属性与相应的块材一致,由此导致的磁致伸缩系数计算是不准确的.在目前大多数方法中仅仅在使用一个单一的弹性各向同性基底中能够避免这个问题.该文模型在各向异性基底下同样适用,并且不要求薄膜的厚度远远小于基底厚度,因此也能够用来计算磁致伸缩应变和设计微电机械系统和生物微电机械系统.对已有的铁基非晶薄膜的实验数据,在不同磁场强度下,磁致伸缩系数的计算结果与已有模型进行了比较,它们之间的差异得到了解释.同时,还可以得到薄膜的弹性常数.     

磁致伸缩薄膜力学行为的有限元仿真研究

建立了一种磁致伸缩薄膜力学行为的有限元计算方法.该方法将磁致伸缩薄膜在磁场中的形变行为等效为薄膜在热场中的各向异性热膨胀形变行为,基于该等效模型,利用有限元软件计算了磁致伸缩薄膜悬臂梁的力学行为与外加磁场的关系.结果表明,该方法可有效模拟磁致伸缩薄膜在外磁场下的力学行为.     

有限长滑动轴承非线性油膜力的近似解法

本文中提出了一种求解有限长径向滑动轴承非线性油膜力的近似解析方法.在滑动轴承-转子系统非线性动力行为分析中,油膜力计算模型通常采用"π"油膜假设,但是,实际工况中油膜的存在区域并非是"π"区域,运行时油膜中出现气穴,破裂成条纹状(即具有Reynolds边界条件).本文中的近似解析方法采用Reynolds边界条件,基于变分原理,运用分离变量法求解油膜的压力分布,其中油膜压力的周向分离函数通过无限长轴承的油膜压力分布获得,油膜的破裂终止位置角通过连续条件确定,轴向分离函数运用变分原理并结合周向函数求得.计算结果表明:本文中提出的方法和有限元方法的结果吻合得很好.在此基础上,分析了一些轴承参数对油膜压力分布的影响.     

第十二届全国周培源大学生力学竞赛“理论设计与操作”团体赛“自停滚轮”项目设计方案

本文介绍了江苏科技大学代表队在第十二届全国周培源大学生力学竞赛“理论设计与操作”团体赛“自停滚轮”项目中的设计方案和制作过程,给关心和热爱该比赛的力学爱好者提供参考。     

Surface concentration measurement of a spreading monolayer film using a displacement current technique

There are numerous techniques for measuring surface concentration of monolayer films. While most techniques are suitable only for stationary films, a novel technique is examined for its feasibility in measuring the concentration of a polar monolayer during the spreading of the film. Measurement of the concentration of an octadecanol monolayer while spreading over a water surface is demonstrated with a displacement current measurement technique in conjunction with Wilhelmy plate measurements of the surface pressure. It was found that the displacement current technique can easily measure changes in the film concentration well below those detectable by the Wilhelmy plate. A gaseous film region was observed ahead of the leading edge detectable by the Wilhelmy plate. This film region has not been previously reported in the literature. Furthermore, the film front appears to diffuse during the spreading process. Surfactant concentration behavior during spreading is useful for examining and developing models of surface tension driven flows.     

含气泡油滴撞击油膜壁面时气泡的变形与破裂

油--气润滑过程中润滑油液滴受高速气流扰动易形成含气泡油滴,微气泡将对油滴撞击壁面时的运动过程以及壁面油膜 层的形成质量产生重要影响. 基于耦合的水平集--体积分数 方法,对含气泡油滴撞击油膜壁面行为进行数值模拟研究, 考察含气泡油滴撞击油膜壁面时气泡的变形运动过程,探讨气泡破裂的动力学机制,分析气泡大小、碰撞速度和液体黏度等因素对含气 泡油滴撞壁过程中气泡变形特征参数的影响规律. 研究表明:含气泡油滴撞击油膜壁面后气泡会发生变形,并破裂形成膜液滴;气泡随同 液滴运动过程中,气泡内外压力和速度梯度变化是使气泡发生破裂的主要诱因. 气泡大小对气泡破裂方式影响较大,气泡较小时发生单 点破裂,而气泡较大时更容易发生多处破裂. 不同大小气泡受力差异较大,气泡大小与破裂发生时刻没有明显相关性. 碰撞速度和液体 黏度对气泡的变形、破裂和破裂发生时刻都具有一定的影响. 碰撞速度越大,油滴动能越大,更容易产生气泡变形和破裂现象. 液体黏 度增大,在油滴撞壁运动前期促进气泡变形,而在运动后期可以阻延气泡破裂行为发生.      

蠕变压痕实验的计算机模拟

采用有限元的方法对双相材料的蠕变压痕实验进行了数值模拟，在有限元数值解的基础上，定义了相应于传统单轴蠕变实验的“等效应力”和“等效应变”，建立了蠕变压痕实验同传统单轴蠕变实验之间的关系，给出了确定薄膜蠕变应力指数和蠕变常数的方法；同时数值解的结果表明，实验中通过控制压痕深度不超过薄膜厚度的 ５％～１０％，忽略基体的硬化指数对确定薄膜性能的影响存在一定的误差，但基体的弹性模量对确定薄膜的蠕变性能影响不大。     

Wave regimes on a ferromagnetic viscous‐fluid film flowing down a vertical cylinder

Axially symmetrical waves on the surface of a ferromagnetic viscousfluid film flowing down a cylindrical conductor with alternating current are considered. In this case, in addition to the gravitational force, the film is affected by a spatially nonuniform timedependent magnetic field. The film thickness was assumed to be small compared to the radius of the conductor. In the longwave approximation, a model equation for the deviation of the film thickness from its undisturbed value is obtained. Some numerical solutions of this equations are reported.     

Numerical study of evaporation by mixed convection of a binary liquid film flowing down the wall of two coaxial cylinders

Evaporation by mixed convection of a binary liquid film flowing down the external wall of a vertical cylinder has been investigated numerically. Two cases were considered: one where the cylinder wall is soaked with a liquid, and another where a liquid film flows along this wall. Heat, mass and momentum transfer in the liquid film and the vapor phase are modelled by mixed convection equations. In order to locate the liquid–vapor interface, a suitable coordinate transformation is carried out with suitable variables. The discretization of the dimensionless equations by an implicit difference scheme leads to a system of algebraic equations, which are solved by using Gauss algorithm for the momentum conservation equations and Thomas algorithm for the energy and diffusion conservation equations. The film thickness is calculated by the Newtons method. Results show, in particular, that the film thickness cannot be neglected and that the latent heat transfers are increasingly significant as the liquid film components become more volatile.     

Downward Flow of a Nonisothermal thin Liquid Film with Variable Viscosity

Equations of a thinfilm flow with linear dependences of viscosity and surface tension of the liquid on temperature are derived. The impact of various factors on the shape of the free boundary of the film are numerically analyzed.     

Stability of a Falling Liquid Film with a Non-Equilibrium Adsorbed Sublayer of Soluble Surfactant

The hydrodynamic instability of a falling film of a dilute solution of a volatile surfactant is studied.The flow of the liquid-gas (vapor) two-phase three-component system is accompanied by surfactant mass transfer across the free surface and is described by a system of five evolutionary equations for five functions depending on time and a spatial coordinate. These functions are the thicknesses of the film and the diffusion boundary layer, the concentrations of the free surfactant and the bound surfactant in the adsorbed sublayer, and the fluid velocity on the film surface. The dispersion equation determining the eigenvalues and the corresponding instability modes is solved numerically in the space of ten free nondimensional governing parameters. Main attention is focused on examining the role of the parameters controlling the influence of the surfactant on the Marangoni effect and the film instability at finite adsorption-desorption rates.     

酯化型环氧化合物摩擦成膜对润滑油摩擦学性能影响之研究

用油酸和环氧树脂合成了一种能够形成摩擦聚合膜的酯化型环氧化合物润滑油添加剂——DE成膜剂。以液体石蜡或二线油为基础油,在栓-盘式试验机和四球试验机上就DE成膜剂对润滑油摩擦学性能的影响进行了研究。结果表明,添加DE成膜剂明显地改善了润滑油的摩擦学性能;在基础油中加入DE成膜剂比加环氧树脂、脂肪酸酯或油酸时的摩擦系数低、表面擦伤少、承载能力高、磨损量小。文章还对DE成膜剂在摩擦表面上形成的摩擦聚合膜的作用机制进行了分析和探讨。     

PVDF薄膜在金属层裂现象研究中的初步应用

主要介绍了一种基于聚偏二氟乙烯(polyvinylidene fluoride,PVDF)薄膜的同步触发器的原理设计.该种触发器利用PVDF薄膜和探针响应时间较快的特点,实现了微秒级的时间同步精度,解决了数字化闪光X射线成像系统应用于金属层裂现象研究中的同步时间关联技术难题,获取了不同飞行时刻层裂飞片的X光图片.     

Measurement of liquid film in microchannels using a laser focus displacement meter

This paper presents a new method for measuring the interfacial displacement of a liquid film in microchannels using a laser focus displacement meter (LFD). The purpose of the study is to clarify the effectiveness of the new method for obtaining detailed information concerning interfacial displacement, especially in the case of a thin liquid film, in microchannels and minichannels. To prevent the tube wall signal from disturbing that of the gas–liquid interface, a fluorocarbon tube with a water box was used; the refraction index of this device is the same as that for water. With this method, accurate instantaneous measurements of the interfacial displacement of the liquid film were achieved. The error caused by refraction of the laser beam passing through the acrylic water box and fluorocarbon tube was estimated analytically and experimentally. The formulated analytical equation can estimate the real interface displacement by using the measured displacement in a fluorocarbon tube of 25 m to 2.0 mm I.D. A preliminary test using fluorocarbon tubes of 1 mm and 2 mm I.D. showed that the corrected interface displacement calculated by the equation agreed with the real displacement to within a 1% margin of error. It was also confirmed that the LFD in the system could measure a liquid film of 0.25 m at the thinnest. We made simultaneous measurements of the interface in fluorocarbon tubes of 0.5 mm and 1 mm I.D. using the LFD and a high-speed video camera with a microscope. These showed that the LFD could measure the interface of a liquid film with high spatial and temporal resolution during annular, slug, and piston flow regimes. The data also clarified the existence of a thin liquid film of less than 1 m in thickness in the slug and annular flow regimes.     

聚变堆相关的液态金属膜流初步实验研究

在磁约束核聚变堆的面对等离子部件设计中,液态金属锂膜流因具有带走杂质、保护面对等离子固壁等优点而被认为是优选方案之一. 然而,如何克服聚变堆中强磁场环境下产生的磁流体力学效应并形成大面积均匀铺展锂膜流动是目前亟需解决的问题.本文通过搭建室温液 态镓铟锡回路和高温液态锂回路,开展了两种不同特性的液态金属膜流实验, 并采用传统可视化方法获得了展向磁场存在时镓铟锡和锂在导电底板形成的液膜流动表面特征.实验结果 表明: 无磁场时,两种液态金属膜流流动表面波动特性与常规流体膜流均一致, 即随着流动雷诺数的增加表面波动变得更为混乱; 而展向磁场存在时,镓铟锡膜流表面波动变得更为规则, 且沿着磁场方向平行排列,表现为拟二维波动的特征; 而锂膜流却产生了明显的磁流体 力学阻力效应,表现为在流动方向局部产生锂滞留现象, 且滞留点随雷诺数增大向下游移动. 最后通过膜流受力分析,进一步阐述了锂膜流受到比镓铟锡膜流更为严重磁流体力学效应影响的原因.