实验力学在未来国际上的地位

本文论述了测量和实验技术当前和未来在分析结构、结构单元以及技术系统的位移、应变和应力中所起的作用.今天比以往任何时候都有更多的原因在广泛的领域中采用实验力学的方法。现代先进的新技术,新的测量设备,自动的量测和评价过程已应运而生。先进的测量技术和计算机技术的结合——杂交技术已得到了发展,这些技术使我们能对结构和产品进行优化设计:节省能源和原材料,提高产品质量以及结构和技术系统的可靠性和安全度,管理生产的过程,监控运行系统的安全。这些方法能用于减少技术系统的危险性和对环境的破坏,对发展中国家传授先进的实验力学方法的知识,显得更为重要。     

Optimization of multiwalled carbon nanotubes reinforced hollow‐fiber solid–liquid‐phase microextraction for the determination of polycyclic aromatic hydrocarbons in environmental water samples using experimental design

A novel design of hollow‐fiber liquid‐phase microextraction containing multiwalled carbon nanotubes as a solid sorbent, which is immobilized in the pore and lumen of hollow fiber by the sol–gel technique, was developed for the pre‐concentration and determination of polycyclic aromatic hydrocarbons in environmental water samples. The proposed method utilized both solid‐ and liquid‐phase microextraction media. Parameters that affect the extraction of polycyclic aromatic hydrocarbons were optimized in two successive steps as follows. Firstly, a methodology based on a quarter factorial design was used to choose the significant variables. Then, these significant factors were optimized utilizing central composite design. Under the optimized condition (extraction time = 25 min, amount of multiwalled carbon nanotubes = 78 mg, sample volume = 8 mL, and desorption time = 5 min), the calibration curves showed high linearity (R ² = 0.99) in the range of 0.01–500 ng/mL and the limits of detection were in the range of 0.007–1.47 ng/mL. The obtained extraction recoveries for 10 ng/mL of polycyclic aromatic hydrocarbons standard solution were in the range of 85–92%. Replicating the experiment under these conditions five times gave relative standard deviations lower than 6%. Finally, the method was successfully applied for pre‐concentration and determination of polycyclic aromatic hydrocarbons in environmental water samples.     

A study of internal heat transfer in nonuniform porous structures

The results of theoretical and experimental studies of heat transfer and pressure drop in nonuniform porous materials and systems are presented. In experiments, measurements were made of the air flow rate, inlet and outlet air pressures, and air and porous sample temperatures. Experimental determination of the heat transfer coefficient in porous structures is associated with certain difficulties. The problem of determining a temperature difference between coolant and porous skeleton is the most complex. As a rule, under laboratory conditions this difference is small and cannot be found with sufficient accuracy. In the present work, the method of determination of the internal heat transfer coefficient is based on solving the inverse unsteady heat transfer problem for porous structures. Using this approach, the heat transfer coefficient is calculated indirectly or on the basis of the porous material temperature variation over time.     

粘贴碳纤维布加固混凝土管道试验研究

首次通过对14个素混凝土和14个钢筋混凝土环状试件外粘碳纤维布加固性能进行试验，研究了碳纤维布加固混凝土内压圆管的破坏特征、受力性能和破坏机理。对不同加固方法及一次或二次受力的混凝土管在内压力作用下的极限承载力、荷载一应变关系等方面进行了研究。试验结果表明，用碳纤维布加固混凝土内压管可以显著地提高极限承载力，明显的改善了构件的延性，能够获得良好的力学性能。加固后试件的开裂承载力与未加固试件相比，提高幅度不大，加固试件二次受力与一次受力相比，开裂荷载有所降低，但极限承载力基本相同。用碳纤维布加固内压管是一个新课题，具有很好的应用前景，用本文提出的加固方法具有优良的加固性能，可为工程应用提供参考。     

An experimental study of the effect of the blow-in rate on the size of the flow separation region

Experimental results are presented concerning the effect of the air blow-in rate on the size of the flow separation region downstream of a rearward-facing step at different step heights. The stream function is found from the experimental velocity profiles, the streamline = 0 being taken as the boundary line. It is shown that the separation region increases as the blow-in rate is increased. Generalization of the experimental results for different blow-in rates and step heights has made it possible to obtain an analytical expression describing the location of some characteristic lines in the separation region (boundary streamline, reverse-flow boundary, line of reverse-flow maximum velocity, line of variable-velocity layer thickness, and the displacement thickness line). Velocity profiles are obtained by means of a hot-wire anemometer. Analytical expressions are written as polynomials with unknown coefficients. The results obtained may be helpful in developing techniques for the treatment of heat transfer under flow separation conditions.     

实验／分析模态双协调综合的实现

本文讨论了实验/分析模态双协调综合实现中实验子结构转角自由度和集中力矩柔度的测量问题。首次提出基于有限元理论的双无加载概念,并通过仿真计算说明其在转角自由度测量的应用价值.最后以一汽车底架模型为实例,经过分析综合和实验(/分析)综合,实践了本文的主题.     

Identification of the Physical Parameters Used in the Thermo-Hygro-Mechanical Model

This paper describes different methods used to identify a large number of physical parameters of the thermo-hygro-mechanical coupling model. This model is developed on the basis of mechanics of porous media and deals with the prediction of response of a structure submitted to thermal, hygrometric and mechanical loading. The aim of this work is mainly to propose some experimental methods for the determination of physical parameters used previously in the model such as hygrometric parameters (liquid Biot's coefficient b _l , vapour and liquid permeability _v, _l and tangent capillary modulus N _ll). Thermal parameters such as thermal conductivity (), specific heat (C) and the thermo-hydrous expansion coefficient ( _i ^p ) have been identified using some works published previously. The different physical parameters were identified in the case of cement mortar without taking into account the influence of hysteresis.     

遥感技术用于固体力学实验研究的新成果

在岩石、混凝土和钢材加载直到破坏的过程中用红外和微波遥感技术进行了观测研究．发现这些材料在加载过程中其红外和微波辐射温度、红外辐射波谱及红外热像均随应力的变化而变化．材料破坏前这些变化表现出某些前兆性特征．研究表明遥感技术可作为固体力学研究的一种新手段，并可望在工程上得到应用     

穿透短裂纹扩展趋偏现象的模型分析和实验研究

本文揭示了穿透短裂纹疲劳扩展中的一个特性－趋偏扩展特性。这一特性是穿透短裂纹预测和测试中产生偏问题的根本原因。通过对长、短裂纹扩展特性及主要影响因素的分析，提出了进行穿透短裂纹试验时必须注意的若干事项。     

Transport with a Very Low Density Contrast in Hele–Shaw Cell and Porous Medium: Evolution of the Mixing Zone

The optimal concentration of a blue dye solution with 'tracer' properties, enabling a pollutant to be marked was determined by the use of numerical, theoretical and experimental approaches. Experimental investigations were performed on a transparent Hele–Shaw cell and the concentration distribution was analyzed using an optical technique based on dye light absorption properties. The injected optimal concentration was established thanks to a theoretical and experimental study carried out on the output signal dynamics. Using the same experimental conditions, numerical simulations were performed. The very good agreement between the data (experimental and numerical) clarified that: (i) the choice of the blue dye optimal concentration was valid and (ii) the concentration-dependent density should not be neglected in flow and transport equations even if it concerns a so-called 'tracer'. Following this remark, a theoretical aspect was developed in order to determine the analogous conditions between a Hele–Shaw cell and a porous medium for the variable density transport phenomenon. The structure of the concentration-dependent dispersion tensor used in the numerical code was obtained by homogenizing the Stokes flow of a bi-component mixture. The numerical results show that, as long as the tracer density does not exceed a certain value, it is not necessary to take into account a density contrast in terms of the dispersion tensor. The classical form of the Taylor dispersion tensor can be used successfully.