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对高架桥吊装中发生的严重事故进行了力学分析，指出事故发生的原因和防止类似事故发生的对应策略．     

远距离,高精度二维动态位移测量

本文介绍了基于ＣＣＤ位置探测技术的远距离位移测量系统。将一明亮光标固定于被测目标位置上，用望远显微成象系统将光标成象于ＣＣＤ的光靶上，ＣＣＤ摄像机将靶面上的光信号转变为相应的电信号，利用数字图象处理技术可以精确地确定光标的位置。通过与初始位置的比较，可以测量被测目标所产生的微小位移。在６ｍ的测量距离上可获得０．０１ｍｍ的测量精度，而且通过改变光学系统可使测量距离扩大到１００ｍ甚至更远     

ESPI技术对外贴纤维混凝土加固承载的实验研究

采用电子散斑干涉技术,对外贴碳纤维加固混凝土梁的外贴材料位移的分布特征,进行了全场实时测量,通过实验获得的散斑干涉条纹图可以得到外贴材料与混凝土梁的粘结传力长度随粘结长度及初始载荷之间的关系;了解用于加固的碳纤维材料的应变分布特点和产生梁侧剥离破坏时的碳纤维表面位移(应变)的演化过程。实验还说明了电子散斑干涉技术不仅可用于位移的测量,而且也可用于结构安全监测和破坏预报。文中给出了对C20D、C25A和C60C侧贴碳纤维板加固在不同载荷作用直到构件破坏前的位移测试及对试件C60C轴线上的剪应力分析结果。     

边坡工程加固需求度评价及其应用

稳定程度不足的边坡通常都需要进行加固。但在加固系统设计时工程师们必须搞清边坡的哪些部位应进行重点加固 ,哪些部位只需要一般加固 ,甚至不需要加固 ,以便合理地布置加固措施。在工程地质力学综合集成方法论 (EGMS)的基础上 ,作者提出了边坡工程加固需求度 (DRD)的概念及其应用方法。     

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.     

有限宽板中心裂纹断裂过程区的长度和位移公式

对岩石、混凝土和陶瓷等准脆性材料进行断裂分析,有必要研究裂纹前端的断裂过程区所起的作用以及各种因素对它的影响。本文提出分析有限宽中心裂纹板剪切断裂过程区的方法,此方法基于D－B模型的叠加原理,考虑了压剪断裂的摩擦阻力,并将有限板宽影响简化为载荷的修正,以非常简便的方法推导出计算断裂过程区长度和位移的公式,这些公式补充了现有文献只有“无限大”板的解的不足。利用这些公式,分析各种参数对断裂过程区长度和位移的影响变得非常方便。     

A photo-optical technique for measuring flow-induced vibrations in cantilevered tube bundles

A photo-optical technique has been developed for monitoring the dynamic displacement of cantilevered tubes in fluid flow. The technique employs an optical fiber to transmit light through the tube and a phototransistor array to measure the motion of the light beam that is projected from the end of the tube. The device is simple, inexpensive, and very sensitive to small displacements. Details are given for the development of the technique, analysis of performance, and static calibration. The device was tested by monitoring the dynamic response of a bundle of cantilevered tubes in both single-phase and two-phase Freon 11 flows. The results are compared with those of a standard strain gauge bridge.     

RESEARCH PROGRESS OF FRACTURE TOUGHNESS TEST METHOD FOR LOW CONSTRAINT SPECIMENS 1)

低约束试件断裂韧性测试对油气管道安全运营具有重要意义。本文回顾了低约束试件断裂韧性测试方法及发展过程,介绍了裂纹尖端张开位 移(crack tip opening displacement, CTOD)和J积分等常用断裂韧性表征参数,并对断裂韧性测试中应力强度因子、J积分塑性因子、J积分与CTOD转换因子、裂纹尺寸测量方法、数 字图像相关方法等关键问题进行对比分析,总结需要深入研究的问题,为低约束试件断裂韧性测试发展提供一定依据。     

Velocity fields and streamline patterns of miscible displacements in cylindrical tubes

Displacements of a viscous fluid by a miscible fluid of a lesser viscosity and density in cylindrical tubes were investigated experimentally. Details of velocity and Stokes streamline fields in vertical tubes were measured using a DPIV (digital particle image velocimetry) technique. In a reference frame moving with the fingertip, the streamline patterns around the fingertip obtained from the present measurements confirm the hypothesis of Taylor (1961) for the external patterns, and that of Petitjeans and Maxworthy (1996) for the internal patterns. As discussed in these papers, the dependent variable, m, a measure of the volume of viscous fluid left on the tube wall after the passage of the displacing finger, is a parameter that determines the flow pattern. When m>0.5 there is one stagnation point at the tip of the finger; when m<0.5 there are two stagnation points on the centerline, one at the tip and the other inside the fingertip, and a stagnation ring on the finger surface with a toroidal recirculation in the fingertip between the two stagnation points. The finger profile is obtained from the zero streamline of the streamline pattern.An erratum to this article can be found at     

Modeling and Analysis of an Elastic Problem with Large Displacements and Small Strains

In this paper we present and analyze a geometrically nonlinear formulation that models the unsteady motion of two and three-dimensional elastic structures in the case of large displacements-small strains. In a first part (Section 2) we derive the equations describing the motion of the body. In a second part (Section 3), existence of a weak solution is proved using a Galerkin method. We also prove that the solution is unique.